commit 268a6937b123f7454b606a2caee9e5ecb0623b55
Author: Madeorsk <madeorsk@protonmail.com>
Date:   Fri Nov 8 17:12:46 2024 +0100

    Initialize Nest model library.

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2dfd9ec
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# IDEA
+.idea/
+*.iml
+
+# Composer
+vendor/
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..f42a331
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,47 @@
+{
+	"version": "1.0",
+	"name": "nest/model",
+	"description": "Nest model service.",
+	"type": "library",
+	"authors": [
+		{
+			"name": "Madeorsk",
+			"email": "madeorsk@protonmail.com"
+		}
+	],
+	"autoload": {
+		"psr-4": {
+			"Nest\\Model\\": "src/"
+		}
+	},
+	"repositories": [
+		{
+			"type": "vcs",
+			"url": "https://code.zeptotech.net/Nest/Core"
+		},
+		{
+			"type": "vcs",
+			"url": "https://code.zeptotech.net/Nest/Events"
+		},
+		{
+			"type": "vcs",
+			"url": "https://code.zeptotech.net/Nest/Types"
+		},
+		{
+			"type": "vcs",
+			"url": "https://code.zeptotech.net/Nest/Database"
+		},
+		{
+			"type": "vcs",
+			"url": "https://code.zeptotech.net/Nest/Cli"
+		}
+	],
+	"minimum-stability": "dev",
+	"require": {
+		"php": "^8.3",
+		"nest/core": "dev-main",
+		"nest/events": "dev-main",
+		"nest/types": "dev-main",
+		"nest/database": "dev-main"
+	}
+}
diff --git a/src/ArrayBlueprint.php b/src/ArrayBlueprint.php
new file mode 100644
index 0000000..e786ae4
--- /dev/null
+++ b/src/ArrayBlueprint.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Nest\Model;
+
+abstract class ArrayBlueprint
+{
+	protected string $type;
+
+	protected ?string $table = null;
+
+	protected ?string $foreignKeyName = null;
+
+	protected ?string $foreignValueName = null;
+
+	/**
+	 * @param class-string $entityClass Entity class where the field is defined.
+	 * @param string $name Name of the field.
+	 */
+	public function __construct(protected string $entityClass, protected string $name)
+	{
+	}
+
+	public function type(string $type): static
+	{
+		$this->type = $type;
+		return $this;
+	}
+
+	public function table(string $table): static
+	{
+		$this->table = $table;
+		return $this;
+	}
+
+	public function foreignKeyName(string $foreignKeyName): static
+	{
+		$this->foreignValueName = $foreignKeyName;
+		return $this;
+	}
+
+	public function foreignValueName(string $foreignValueName): static
+	{
+		$this->foreignValueName = $foreignValueName;
+		return $this;
+	}
+}
diff --git a/src/ArrayInstance.php b/src/ArrayInstance.php
new file mode 100644
index 0000000..71c9f88
--- /dev/null
+++ b/src/ArrayInstance.php
@@ -0,0 +1,120 @@
+<?php
+
+namespace Nest\Model;
+
+use Nest\Database\Query\DeleteQuery;
+use Nest\Database\Query\InsertQuery;
+use Nest\Database\Query\Raw;
+use Nest\Database\Query\SelectQuery;
+use Nest\Database\Exceptions\NotCurrentTransactionException;
+use Nest\Database\Exceptions\Query\MissingConditionValueException;
+use Nest\Database\Exceptions\UnknownDatabaseException;
+use Nest\Model\Query\EntityQuery;
+use function Nest\Utils\array_first_or_val;
+use function Nest\Utils\str_snake_singularize;
+
+class ArrayInstance extends ReadableArrayBlueprint
+{
+	/**
+	 * Create an array field instance from an array field definition.
+	 * @param ArrayBlueprint $array
+	 */
+	public function __construct(ArrayBlueprint $array)
+	{
+		parent::__construct($array->entityClass, $array->name);
+
+		// Copy all fields.
+		$this->type = $array->type;
+		$this->table = $array->table;
+		$this->foreignKeyName = $array->foreignKeyName;
+		$this->foreignValueName = $array->foreignValueName;
+	}
+
+	/**
+	 * Get current table / foreign key / foreign value state.
+	 * @param string $fromTable Table from which to get values.
+	 * @return array{string, string, string} Table, Foreign key, Foreign value.
+	 */
+	public function getState(string $fromTable): array
+	{
+		return [
+			$table = $this->getTable() ?? "{$fromTable}_{$this->name}",
+			$foreignKey = $this->getForeignKeyName() ?? "$table.".str_snake_singularize($fromTable)."_id",
+			$foreignValue = $this->getForeignValueName() ?? "$table.".str_snake_singularize($this->name),
+		];
+	}
+
+	/**
+	 * Extract a column name from a fully qualified name.
+	 * @return string The column name.
+	 */
+	private function getColumnName(string $fullyQualifiedName): string
+	{
+		return substr($fullyQualifiedName, strrpos($fullyQualifiedName, ".") + 1);
+	}
+
+	/**
+	 * Setup inline loading for the current array field in an entity query.
+	 * @param EntityQuery $baseQuery The entity query to alter.
+	 * @param string $prefix Prefix to add to the name of the properties.
+	 * @return Raw Generated select subquery.
+	 * @throws MissingConditionValueException
+	 */
+	public function genSelect(EntityQuery $baseQuery, string $prefix = ""): Raw
+	{
+		// Get all auto values for undefined tables or keys.
+		[$table, $foreignKey, $foreignValue] = $this->getState($baseQuery->getTableName());
+
+		// Build subquery SELECT SQL.
+		$sql = ((new SelectQuery($baseQuery->getDatabase(), $table))
+			->select($foreignValue)
+			->whereColumn("{$baseQuery->getTableName()}.".$baseQuery->getPrimaryKeyName(), "=", $foreignKey))->build();
+
+		// Return the raw SELECT of a JSON array.
+		return new Raw(
+			"ARRAY_TO_JSON(ARRAY($sql->sql)) AS $prefix$this->name",
+			$sql->bindings,
+		);
+	}
+
+	/**
+	 * @param Entity $entity Entity for which to save.
+	 * @param array $value Array to save.
+	 * @return void
+	 * @throws MissingConditionValueException
+	 * @throws UnknownDatabaseException
+	 * @throws NotCurrentTransactionException
+	 */
+	public function save(Entity $entity, array $value): void
+	{
+		// Start a transaction for the whole save.
+		$transaction = $entity->getDatabase()->startTransaction();
+
+		// Get all auto values for undefined tables or keys.
+		[$table, $foreignKey, $foreignValue] = $this->getState($entity->getTableName());
+
+		// Get entity primary key value.
+		$entityKey = $entity->{array_first_or_val($entity->getPrimaryFields())};
+
+		// Delete existing values.
+		((new DeleteQuery($entity->getDatabase(), $table))
+			->where($foreignKey, "=", $entityKey))
+			->execute();
+
+		// Get actual columns names.
+		$foreignKey = $this->getColumnName($foreignKey);
+		$foreignValue = $this->getColumnName($foreignValue);
+
+		// Insert new ones.
+		((new InsertQuery($entity->getDatabase(), $table)))
+			// Insert all values of the array.
+			->values(...array_map(fn (mixed $val) => ([
+				$foreignKey => $entityKey,
+				$foreignValue => $val,
+			]), $value))
+			->execute();
+
+		// Commit transaction.
+		$transaction->commit();
+	}
+}
diff --git a/src/Entities.php b/src/Entities.php
new file mode 100644
index 0000000..487a8d0
--- /dev/null
+++ b/src/Entities.php
@@ -0,0 +1,125 @@
+<?php
+
+namespace Nest\Model;
+
+use Nest\Database\Exceptions\Query\MissingConditionValueException;
+use Nest\Database\Exceptions\Query\NoPrimaryFieldException;
+use Nest\Database\Exceptions\UnknownDatabaseException;
+use Nest\Exceptions\InvalidTypeException;
+use Nest\Model\Exceptions\MissingRequiredFieldException;
+use Nest\Model\Exceptions\UndefinedRelationException;
+use Nest\Types\Exceptions\IncompatibleTypeException;
+use Nest\Model\Query\EntityQuery;
+use function Nest\Utils\array_first;
+
+/**
+ * Class of a collection of entities, to perform operations on all of them.
+ * @template Entity
+ */
+class Entities
+{
+	/**
+	 * Entities.
+	 * @var Entity[]
+	 */
+	protected array $entities;
+
+	/**
+	 * Create a collection of entities with an array of entities.
+	 * @param Entity[] $entities
+	 */
+	public function __construct(array $entities)
+	{
+		$this->entities = $entities;
+	}
+
+	/**
+	 * Get entities array.
+	 * @return Entity[] The entities.
+	 */
+	public function get(): array
+	{
+		return $this->entities;
+	}
+
+	/**
+	 * Set values to all the entities.
+	 * @param string $name Name of the value to set.
+	 * @param mixed $value Value to set.
+	 * @return void
+	 */
+	public function __set(string $name, mixed $value): void
+	{
+		foreach ($this->entities as $entity)
+			$entity->$name = $value;
+	}
+
+	/**
+	 * Get all values with the given name in the entities.
+	 * @param string $name Name of the value to get.
+	 * @return array Array of values.
+	 */
+	public function __get(string $name): array
+	{
+		$result = [];
+		foreach ($this->entities as $entity)
+			$result[] = $entity->$name;
+		return $result;
+	}
+
+	/**
+	 * Call the given method on all entities.
+	 * @param string $name Name of the method to call.
+	 * @param array $arguments Arguments of the method.
+	 * @return array Results of all calls.
+	 */
+	public function __call(string $name, array $arguments): array
+	{
+		$results = [];
+		foreach ($this->entities as $entity)
+			$results[] = $entity->$name(...$arguments);
+		return $results;
+	}
+
+	/**
+	 * Save current entities states.
+	 * @return bool True if something was saved, false otherwise.
+	 * @throws IncompatibleTypeException
+	 * @throws MissingConditionValueException
+	 * @throws MissingRequiredFieldException
+	 * @throws NoPrimaryFieldException
+	 * @throws InvalidTypeException
+	 */
+	public function save(): bool
+	{
+		$result = false;
+		foreach ($this->entities as $entity)
+			// Set result to true if needed.
+			$result = $result || $entity->save();
+		return $result;
+	}
+
+	/**
+	 * Load given relation in the entities.
+	 * @param array<string|int, string|callable(EntityQuery): void> $relations Relations to load.
+	 * @return $this
+	 * @throws UnknownDatabaseException
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws MissingConditionValueException
+	 * @throws UndefinedRelationException
+	 */
+	public function load(array $relations): static
+	{
+		// Do nothing if there are no entities.
+		if (empty($this->entities)) return $this;
+
+		// Normalize relations array.
+		$relations = EntityQuery::normalizeRelationsDefinition($relations);
+
+		// Perform load for all the entities.
+		array_first($this->entities)->query()->load($this->entities, $relations);
+
+		return $this;
+	}
+}
diff --git a/src/Entity.php b/src/Entity.php
new file mode 100644
index 0000000..7e501c6
--- /dev/null
+++ b/src/Entity.php
@@ -0,0 +1,586 @@
+<?php
+
+namespace Nest\Model;
+
+use Carbon\Carbon;
+use Nest\Application;
+use Nest\Database\Database;
+use Nest\Database\Query\QueryBuilder;
+use Nest\Database\Query\Raw;
+use Nest\Events\HasEvents;
+use Nest\Database\Exceptions\Query\MissingConditionValueException;
+use Nest\Database\Exceptions\Query\NoPrimaryFieldException;
+use Nest\Database\Exceptions\UnknownDatabaseException;
+use Nest\Exceptions\InvalidTypeException;
+use Nest\Model\Exceptions\MissingRequiredFieldException;
+use Nest\Model\Exceptions\UndefinedRelationException;
+use Nest\Model\Exceptions\UnhandledPropertyTypeException;
+use Nest\Types\Exceptions\IncompatibleTypeException;
+use Nest\Model\Events\AfterDelete;
+use Nest\Model\Events\AfterInsert;
+use Nest\Model\Events\AfterLoad;
+use Nest\Model\Events\AfterPropertiesInitialization;
+use Nest\Model\Events\AfterSave;
+use Nest\Model\Events\AfterUpdate;
+use Nest\Model\Events\BeforeDelete;
+use Nest\Model\Events\BeforeInsert;
+use Nest\Model\Events\BeforeLoad;
+use Nest\Model\Events\BeforePropertiesInitialization;
+use Nest\Model\Events\BeforeSave;
+use Nest\Model\Events\BeforeUpdate;
+use Nest\Model\Events\EntityDefinitionEvent;
+use Nest\Model\Query\EntityQuery;
+use Nest\Types\SqlType;
+use function Nest\Utils\array_first;
+use function Nest\Utils\get_class_name_from_fullname;
+use function Nest\Utils\str_camel_to_snake;
+use function Nest\Utils\str_snake_pluralize;
+
+/**
+ * Class of an entity of the model.
+ */
+abstract class Entity
+{
+	use HasEvents;
+	/**
+	 * Set if the entity is new (should be inserted) or not.
+	 * @var bool
+	 */
+	protected bool $isNew = true;
+
+	/**
+	 * Original properties values.
+	 * @var array
+	 */
+	protected array $originals = [];
+
+	/**
+	 * Entity definition cache.
+	 * @var EntityBlueprint
+	 */
+	private EntityBlueprint $_definition;
+
+	/**
+	 * Definition of the entity.
+	 * @param EntityBlueprint $blueprint Entity blueprint to define.
+	 * @return EntityBlueprint Defined entity blueprint.
+	 */
+	public abstract function definition(EntityBlueprint $blueprint): EntityBlueprint;
+
+	/**
+	 * Get the entity definition (from cache if already requested).
+	 * @return EntityBlueprint Defined entity blueprint.
+	 */
+	private function _getDefinition(): EntityBlueprint
+	{
+		if (empty($this->_definition))
+		{ // Get a new definition and save it in cached definition.
+			$this->_definition = $this->definition(new EntityBlueprint(static::class));
+			$this->getEventsManager()->fire(new EntityDefinitionEvent($this));
+		}
+
+		// Return cached definition.
+		return $this->_definition;
+	}
+
+	/**
+	 * Initialize entity.
+	 */
+	public function __construct()
+	{
+		// Initialize properties.
+		$this->initializeProperties();
+	}
+
+	/**
+	 * Initialize entity default properties.
+	 * @return void
+	 */
+	protected function initializeProperties(): void
+	{
+		$this->getEventsManager()->fire(new BeforePropertiesInitialization($this));
+
+		foreach ($this->_getDefinition()->getProperties() as $propertyName => $property)
+		{ // For each property, set its default value if there is one.
+			if ($property instanceof ReadableFieldBlueprint && $property->hasCurrentDateByDefault())
+				$this->$propertyName = Carbon::now();
+		}
+
+		$this->getEventsManager()->fire(new AfterPropertiesInitialization($this));
+	}
+
+
+	/**
+	 * Guess the entity database table name from its class name.
+	 * Always use a plural snake_cased name.
+	 * @return string The database table name of the entity, based on its class name.
+	 */
+	private function guessTableName(): string
+	{
+		return str_snake_pluralize(str_camel_to_snake(get_class_name_from_fullname(
+			(new \ReflectionClass($this))->isAnonymous() ? get_parent_class(static::class) : static::class,
+		)));
+	}
+
+	/**
+	 * Get the entity database table name.
+	 * @return string The database table name of the entity.
+	 */
+	public function getTableName(): string
+	{
+		return $this->_getDefinition()->getTable() ?? $this->guessTableName();
+	}
+
+	/**
+	 * Check that the required fields are set.
+	 * @return string[] Names of the missing required fields.
+	 */
+	public function getMissingRequiredFields(): array
+	{
+		// Get current entity definition.
+		$entityBlueprint = $this->_getDefinition();
+		// Get its required fields.
+		$requiredFields = array_filter($entityBlueprint->getProperties(), fn ($field) => $field instanceof ReadableFieldBlueprint && $field->isRequired());
+
+		// Initialize missing required fields list.
+		$missingRequiredFields = [];
+
+		foreach ($requiredFields as $requiredFieldName => $requiredField)
+		{ // If any required field is not set, add it in the list.
+			if (!isset($this->{$requiredFieldName}))
+				// A required field is not set.
+				$missingRequiredFields[] = $requiredFieldName;
+		}
+
+		return $missingRequiredFields; // All the missing required fields.
+	}
+
+	/**
+	 * Check that all the required fields are set.
+	 * Throw an exception if some are not set.
+	 * @return void
+	 * @throws MissingRequiredFieldException
+	 */
+	public function checkRequiredFields(): void
+	{
+		if (!empty($missingFields = $this->getMissingRequiredFields()))
+			// Some required fields are missing, throwing an exception.
+			throw new MissingRequiredFieldException($missingFields);
+	}
+
+	/**
+	 * Get primary fields.
+	 * @return string|string[] The primary field name, or array of fields when there are multiple primary fields.
+	 */
+	public function getPrimaryFields(): string|array
+	{
+		// Search primary fields.
+		$primaryFields = array_filter($this->_getDefinition()->getProperties(), fn ($field) => $field instanceof ReadableFieldBlueprint && $field->isPrimary());
+
+		// Return primary field(s).
+		return count($primaryFields) == 1 ? array_key_first($primaryFields) : array_keys($primaryFields);
+	}
+
+
+	/**
+	 * Get database of the entity.
+	 * @return Database Database of the entity.
+	 * @throws UnknownDatabaseException
+	 */
+	public function getDatabase(): Database
+	{
+		return Application::get()->databases()->db($this->_getDefinition()->getDatabase());
+	}
+
+	/**
+	 * Create a new SQL query for the entity.
+	 * @return QueryBuilder SQL query builder.
+	 * @throws UnknownDatabaseException
+	 */
+	public function sql(): QueryBuilder
+	{
+		return $this->getDatabase()->query($this->getTableName());
+	}
+
+	/**
+	 * Create a new entity query.
+	 * @return EntityQuery<static> Entity query builder.
+	 * @throws UnknownDatabaseException
+	 */
+	public function query(): EntityQuery
+	{
+		// Create the query.
+		$query = new EntityQuery($this->getDatabase(), $this->getTableName(), $this);
+
+		// Automatically fill "with" with eager loaded properties.
+		$query->with(array_filter(array_map(fn ($property) => (
+			$property instanceof ReadableEntityPropertyBlueprint && $property->doEagerLoad()
+		), $this->_getDefinition()->getProperties())));
+
+		return $query; // Return the created query.
+	}
+
+	/**
+	 * Load given relations in the entity.
+	 * @param array<string|int, string|callable(EntityQuery): void> $relations Relations to load.
+	 * @return $this
+	 * @throws UnknownDatabaseException
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws MissingConditionValueException
+	 * @throws UndefinedRelationException
+	 * @throws UnhandledPropertyTypeException
+	 */
+	public function load(array $relations): static
+	{
+		// Normalize relations array.
+		$relations = EntityQuery::normalizeRelationsDefinition($relations);
+
+		$this->getEventsManager()->fire(new BeforeLoad($this, $relations));
+
+		// Perform load for the current entity.
+		$this->query()->load([$this], $relations);
+
+		$this->getEventsManager()->fire(new AfterLoad($this, $relations));
+
+		return $this;
+	}
+
+	/**
+	 * Create a new entity of the same type.
+	 * @return static A new entity of the same type.
+	 */
+	public function new(): static
+	{
+		return new static();
+	}
+
+	/**
+	 * Set an original property value.
+	 * @param string $propertyName Property name.
+	 * @param mixed $propertyValue Property value.
+	 * @return void
+	 */
+	public function setOriginalProperty(string $propertyName, mixed $propertyValue): void
+	{
+		$this->$propertyName = $propertyValue;
+		$this->originals[$propertyName] = $propertyValue;
+	}
+
+	/**
+	 * Find changes made on the entity.
+	 * @return array<string, mixed> New properties values.
+	 */
+	public function diff(): array
+	{
+		// Initialize diff array.
+		$diff = [];
+
+		foreach ($this->_getDefinition()->getProperties() as $propertyName => $propertyDefinition)
+		{ // Add current property value to diff if it's different from original value.
+			if (!($propertyDefinition instanceof FieldBlueprint || $propertyDefinition instanceof ArrayBlueprint))
+				// Only keep normal fields.
+				continue;
+
+			if (isset($this->$propertyName) && (!isset($this->originals[$propertyName]) || $this->originals[$propertyName] != $this->$propertyName))
+				// Current value is different from original one, adding it to the diff.
+				$diff[$propertyName] = $this->$propertyName;
+		}
+
+		return $diff; // Return properties diff.
+	}
+
+	/**
+	 * Save the current entity state.
+	 * @return bool True if something was saved, false otherwise.
+	 * @throws IncompatibleTypeException
+	 * @throws MissingConditionValueException
+	 * @throws MissingRequiredFieldException
+	 * @throws NoPrimaryFieldException
+	 * @throws UnhandledPropertyTypeException
+	 * @throws UnknownDatabaseException
+	 */
+	public function save(): bool
+	{
+		$this->getEventsManager()->fire(new BeforeSave($this));
+
+		// Check required fields to save.
+		$this->checkRequiredFields();
+
+		if ($this->isNew)
+		{ // This is a new entity, inserting it, then reading the result.
+			$this->fromSqlProperties($this->insert());
+		}
+		else
+		{ // The entity already exists, updating it.
+
+			// Get entity diff.
+			$diff = $this->diff();
+
+			// No diff, return false because there is nothing to update.
+			if (empty($diff)) return false;
+
+			// Get properties definition.
+			$properties = $this->_getDefinition()->getProperties();
+
+			foreach ($diff as $propertyName => $propertyValue)
+			{ // For each property in diff, check if it's an array field.
+				if ($properties[$propertyName] instanceof ArrayBlueprint)
+				{ // If the property is an array field, save it then remove it from diff.
+					(new ArrayInstance($properties[$propertyName]))->save($this, $propertyValue);
+					unset($diff[$propertyName]);
+				}
+			}
+
+			// Update every else property (if there are still some).
+			if (!empty($diff))
+				$this->fromSqlProperties($this->update($diff));
+		}
+
+		$this->getEventsManager()->fire(new AfterSave($this));
+
+		return true; // Entity saved.
+	}
+
+	/**
+	 * Delete the entity.
+	 * @return bool
+	 * @throws MissingConditionValueException
+	 * @throws NoPrimaryFieldException
+	 * @throws UnknownDatabaseException
+	 */
+	public function delete(): bool
+	{
+		$this->getEventsManager()->fire(new BeforeDelete($this));
+
+		// Delete current entity.
+		$this->sql()->newDelete()->whereKeyOf($this)->execute();
+
+		// Set entity as new, in case of a save after deletion.
+		$this->isNew = true;
+
+		$this->getEventsManager()->fire(new AfterDelete($this));
+
+		return true; // Entity is deleted.
+	}
+
+	/**
+	 * Insert current entity values.
+	 * @return object Raw inserted object.
+	 * @throws IncompatibleTypeException
+	 * @throws UnknownDatabaseException
+	 */
+	private function insert(): object
+	{
+		$this->getEventsManager()->fire(new BeforeInsert($this));
+
+		// Return the first result (= the sole inserted row).
+		$result = array_first(
+			// Execute INSERT in RETURNING mode.
+			$this->sql()->newInsert()->values(
+				// Extract properties in an SQL row values array.
+				$this->toSqlProperties()
+			)->execute(true)
+		);
+
+		$this->getEventsManager()->fire(new AfterInsert($this));
+
+		return $result;
+	}
+
+	/**
+	 * Update given entity values.
+	 * @param array<string, mixed> $values Values to update.
+	 * @return object Raw updated object.
+	 * @throws MissingConditionValueException
+	 * @throws IncompatibleTypeException
+	 * @throws NoPrimaryFieldException
+	 * @throws UnknownDatabaseException
+	 */
+	private function update(array $values): object
+	{
+		$this->getEventsManager()->fire(new BeforeUpdate($this));
+
+		// Return the first result (= the sole updated row).
+		$result = array_first(
+			// Execute UPDATE in RETURNING mode.
+			$this->sql()->newUpdate()->set($this->valuesToSql($values))
+				->whereKeyOf($this)
+				->execute(true)
+		);
+
+		$this->getEventsManager()->fire(new AfterUpdate($this));
+
+		return $result;
+	}
+
+	/**
+	 * Get relation of the given name.
+	 * @param string $relationName Name of the relation to get.
+	 * @return EntityPropertyInstance The property instance.
+	 * @throws UndefinedRelationException
+	 */
+	public function getRelation(string $relationName): EntityPropertyInstance
+	{
+		// Get defined properties for the entity.
+		$properties = $this->_getDefinition()->getProperties();
+
+		if (!empty($properties[$relationName]))
+		{ // A property with the relation name exists, trying to get its relation definition.
+			$definition = $properties[$relationName];
+			if (is_a($definition, EntityPropertyBlueprint::class))
+				// Initialize a property instance.
+				return new EntityPropertyInstance($definition);
+			else
+			{ // Not an entity blueprint, throw an exception.
+				throw new UndefinedRelationException(static::class, $relationName);
+			}
+		}
+		else
+		{ // No property with this name, throw an exception.
+			throw new UndefinedRelationException(static::class, $relationName);
+		}
+	}
+
+	/**
+	 * Convert given values to SQL from matching properties types.
+	 * @param array<string, mixed> $values Values to convert to SQL value.
+	 * @return array<string, Raw|string|int|float|null> SQL values.
+	 * @throws IncompatibleTypeException
+	 */
+	private function valuesToSql(array $values): array
+	{
+		// Get properties definition.
+		$propertiesDefinition = $this->_getDefinition()->getProperties();
+
+		foreach ($values as $propertyName => $value)
+		{ // For each value, try to convert its data.
+
+			// Keep the value (and convert it) if there is a matching property.
+			if (!empty($propertiesDefinition[$propertyName]))
+			{
+				// Get property type.
+				$propertyType = $propertiesDefinition[$propertyName]->getTypeInstance();
+
+				if (!$propertyType instanceof SqlType)
+					// Type is not an SQL type, throwing an exception.
+					throw new IncompatibleTypeException(get_class($propertyType), SqlType::class);
+
+				// Converting property value and put it in the SQL object.
+				$values[$propertyName] = $propertyType->toSql($value);
+			}
+			else
+				// No property matching the current value, unset it.
+				unset($values[$propertyName]);
+		}
+
+		return $values; // Return converted values.
+	}
+
+	/**
+	 * Import properties from a raw SQL object.
+	 * @param object $sqlProperties Raw SQL object where to extract properties.
+	 * @param string $prefix Optional prefix of properties in SQL.
+	 * @return void
+	 * @throws IncompatibleTypeException
+	 * @throws UnhandledPropertyTypeException
+	 */
+	public function fromSqlProperties(object $sqlProperties, string $prefix = ""): void
+	{
+		$this->isNew = false; // The entity already exists, as it's read from SQL properties.
+
+		foreach ($this->_getDefinition()->getProperties() as $propertyName => $propertyDefinition)
+		{ // For each defined property, try to read its data.
+			// Prepend property name by the prefix.
+			$propertyName = $prefix.$propertyName;
+
+			// Try to read only if a value is present.
+			if (isset($sqlProperties->$propertyName))
+			{ // Get property type.
+				if (!($propertyDefinition instanceof FieldBlueprint || $propertyDefinition instanceof ArrayBlueprint))
+					throw new UnhandledPropertyTypeException($propertyName, get_class($propertyDefinition));
+
+				// Get property type instance.
+				$propertyType = $propertyDefinition->getTypeInstance();
+
+				if (!$propertyType instanceof SqlType)
+					// Type is not an SQL type, throwing an exception.
+					throw new IncompatibleTypeException(get_class($propertyType), SqlType::class);
+
+				if ($propertyDefinition instanceof FieldBlueprint)
+				{ // Read direct value.
+					// Parsing property value and put it in the entity.
+					$value = $propertyType->fromSql($sqlProperties->$propertyName);
+				}
+				else
+				{ // Read JSON array value.
+					$value = json_decode($sqlProperties->$propertyName);
+					// Parsing array values.
+					foreach ($value as &$val) $val = $propertyType->fromSql($val);
+				}
+
+				// Set original property value.
+				$this->setOriginalProperty($propertyName, $value);
+			}
+		}
+	}
+
+	/**
+	 * Export properties to a raw SQL object.
+	 * @return array<string, Raw|string|int|float|null> Raw SQL array where properties are extracted.
+	 * @param string $prefix Optional prefix of properties in SQL.
+	 * @throws IncompatibleTypeException
+	 */
+	public function toSqlProperties(string $prefix = ""): array
+	{
+		// Initialize raw SQL array.
+		$object = [];
+
+		foreach ($this->_getDefinition()->getProperties() as $propertyName => $propertyDefinition)
+		{ // Get SQL value of each defined property.
+			// Prepend property name by the prefix.
+			$propertyName = $prefix.$propertyName;
+
+			if (isset($this->$propertyName))
+			{ // If property is set, converting it.
+				// Get property type.
+				$propertyType = $propertyDefinition->getTypeInstance();
+
+				if (!$propertyType instanceof SqlType)
+					// Type is not an SQL type, throwing an exception.
+					throw new IncompatibleTypeException(get_class($propertyType), SqlType::class);
+
+				// Converting property value and put it in the SQL object.
+				$object[$propertyName] = $propertyType->toSql($this->$propertyName);
+			}
+		}
+
+		return $object; // Return built raw SQL array.
+	}
+
+	/**
+	 * Generate columns SELECT for the defined properties.
+	 * @param string $prefix Prefix to add to the name of the properties.
+	 * @return Raw[] Selected columns.
+	 * @throws UnknownDatabaseException
+	 * @throws MissingConditionValueException
+	 */
+	public function sqlSelectFields(string $prefix = ""): array
+	{
+		$select = [];
+
+		foreach ($this->_getDefinition()->getProperties() as $propertyName => $property)
+		{ // For each field, generate a column selection.
+			if ($property instanceof FieldBlueprint)
+			{ // It's a field property, generate a SELECT for it.
+				$select[] = new Raw("\"{$this->getTableName()}\".\"$propertyName\"".(!empty($prefix) ? " AS \"$prefix$propertyName\"" : ""));
+			}
+			elseif ($property instanceof ArrayBlueprint)
+			{ // It's an array field, generate a SELECT for it.
+				$select[] = (new ArrayInstance($property))->genSelect($this->query(), $prefix);
+			}
+		}
+
+		return $select;
+	}
+}
diff --git a/src/EntityBlueprint.php b/src/EntityBlueprint.php
new file mode 100644
index 0000000..8a6fb46
--- /dev/null
+++ b/src/EntityBlueprint.php
@@ -0,0 +1,155 @@
+<?php
+
+namespace Nest\Model;
+
+use Nest\Types\Definitions\CarbonType;
+use Nest\Types\Definitions\Integers\BigintType;
+
+/**
+ * @template T
+ */
+class EntityBlueprint
+{
+	/**
+	 * Entity class.
+	 * @var class-string<T>
+	 */
+	protected string $entityClass;
+
+	/**
+	 * Database identifier of the entity.
+	 * @var string|null
+	 */
+	protected ?string $database = null;
+
+	/**
+	 * Database table name of the entity.
+	 * @var string|null
+	 */
+	protected ?string $table = null;
+
+	/**
+	 * Properties definition array.
+	 * @var array<string, (ReadableFieldBlueprint|ReadableArrayBlueprint|ReadableEntityPropertyBlueprint)>
+	 */
+	protected array $properties = [];
+
+	/**
+	 * @param class-string<T> $entityClass Entity class.
+	 */
+	public function __construct(string $entityClass)
+	{
+		$this->entityClass = $entityClass;
+	}
+
+	/**
+	 * Set the database table name of the entity.
+	 * @param string $table The database table name of the entity.
+	 * @return $this
+	 */
+	public function setTable(string $table): static
+	{
+		$this->table = $table;
+		return $this;
+	}
+
+	/**
+	 * Get the database table name of the entity.
+	 * @return string|null The database table name.
+	 */
+	public function getTable(): ?string
+	{
+		return $this->table;
+	}
+
+	/**
+	 * Set the database of the entity.
+	 * @param string $databaseIdentifier The database identifier.
+	 * @return $this
+	 */
+	public function setDatabase(string $databaseIdentifier): static
+	{
+		$this->database = $databaseIdentifier;
+		return $this;
+	}
+
+	/**
+	 * Get the database of the entity.
+	 * @return string|null The database identifier.
+	 */
+	public function getDatabase(): ?string
+	{
+		return $this->database ?? "default";
+	}
+
+	/**
+	 * Get the defined properties.
+	 * @return array<string, (ReadableFieldBlueprint|ReadableArrayBlueprint|ReadableEntityPropertyBlueprint)> The defined properties.
+	 */
+	public function getProperties(): array
+	{
+		return $this->properties;
+	}
+
+	public function field(string $name, string $type): FieldBlueprint
+	{
+		return $this->properties[$name] = (new ReadableFieldBlueprint())->type($type);
+	}
+
+	public function id(string $name = "id", string $type = BigintType::class): FieldBlueprint
+	{
+		return $this->foreignId($name, $type)->autoIncrement()->primary();
+	}
+
+	public function foreignId(string $name, string $type = BigintType::class): FieldBlueprint
+	{
+		return $this->field($name, $type)->unsigned()->index();
+	}
+
+	public function createdAt(string $name = "created_at", string $type = CarbonType::class): FieldBlueprint
+	{
+		return $this->field($name, $type)->required()->currentDateByDefault();
+	}
+
+	public function updatedAt(string $name = "updated_at", string $type = CarbonType::class): FieldBlueprint
+	{
+		return $this->field($name, $type)->required()->currentDateByDefault()->currentDateOnUpdate();
+	}
+
+
+
+	/**
+	 * Define an array field.
+	 * @param string $name The name of the field.
+	 * @param string $type The type of the array values.
+	 * @return ArrayBlueprint The array blueprint.
+	 */
+	public function array(string $name, string $type): ArrayBlueprint
+	{
+		return $this->properties[$name] = (new ReadableArrayBlueprint($this->entityClass, $name))->type($type);
+	}
+
+
+	/**
+	 * Define an entity property.
+	 * @param string $name The name of the property.
+	 * @param string $class The class of the property.
+	 * @param bool $multiple Whether the property is an array or not.
+	 * @return EntityPropertyBlueprint The property blueprint.
+	 */
+	public function entity(string $name, string $class, bool $multiple = false): EntityPropertyBlueprint
+	{
+		return $this->properties[$name] = (new ReadableEntityPropertyBlueprint())->class($class)->multiple($multiple);
+	}
+
+	/**
+	 * Define an entities array property.
+	 * @param string $name The name of the property.
+	 * @param string $class The class of the property.
+	 * @return EntityPropertyBlueprint The property blueprint.
+	 */
+	public function entities(string $name, string $class): EntityPropertyBlueprint
+	{
+		return $this->entity($name, $class, true);
+	}
+}
diff --git a/src/EntityPropertyBlueprint.php b/src/EntityPropertyBlueprint.php
new file mode 100644
index 0000000..5328012
--- /dev/null
+++ b/src/EntityPropertyBlueprint.php
@@ -0,0 +1,106 @@
+<?php
+
+namespace Nest\Model;
+
+abstract class EntityPropertyBlueprint
+{
+	protected string $class;
+
+	protected bool $multiple;
+
+	protected bool $allowInline = true;
+
+	protected EntityPropertyMode $mode;
+
+	protected ?string $localKey = null;
+
+	protected ?string $relatedKey = null;
+
+	protected ?string $pivotTable = null;
+
+	protected ?string $pivotLocalKey = null;
+
+	protected ?string $pivotRelatedKey = null;
+
+	protected bool $eagerLoad = false;
+
+	public function class(string $class): static
+	{
+		$this->class = $class;
+		return $this;
+	}
+
+	public function multiple(bool $multiple = true): static
+	{
+		$this->multiple = $multiple;
+		return $this;
+	}
+
+	/**
+	 * Set if inline loading of the relation is allowed or not.
+	 * @param bool $inline True to allow relation inline loading.
+	 * @return $this
+	 */
+	public function allowInline(bool $inline = true): static
+	{
+		$this->allowInline = $inline;
+		return $this;
+	}
+
+	public function fromLocal(?string $localKey = null, ?string $relatedKey = null): static
+	{
+		$this->mode = EntityPropertyMode::LOCAL;
+		$this->localKey = $localKey;
+		$this->relatedKey = $relatedKey;
+		return $this;
+	}
+	public function fromRelated(?string $relatedKey = null, ?string $localKey = null): static
+	{
+		$this->mode = EntityPropertyMode::RELATED;
+		$this->localKey = $localKey;
+		$this->relatedKey = $relatedKey;
+		return $this;
+	}
+
+	public function localKey(string $localKey): static
+	{
+		$this->localKey = $localKey;
+		return $this;
+	}
+	public function relatedKey(string $relatedKey): static
+	{
+		$this->relatedKey = $relatedKey;
+		return $this;
+	}
+
+	public function fromPivot(string $pivotTable, ?string $pivotLocalKey = null, ?string $pivotRelatedKey = null): static
+	{
+		$this->mode = EntityPropertyMode::PIVOT;
+		$this->pivotLocalKey = $pivotLocalKey;
+		$this->pivotRelatedKey = $pivotRelatedKey;
+		return $this;
+	}
+
+	public function pivotLocalKey(string $pivotLocalKey): static
+	{
+		$this->pivotLocalKey = $pivotLocalKey;
+		return $this;
+	}
+	public function pivotRelatedKey(string $pivotRelatedKey): static
+	{
+		$this->pivotRelatedKey = $pivotRelatedKey;
+		return $this;
+	}
+
+	/**
+	 * Set if the related field should be eager loaded or not.
+	 * Only apply on related fields.
+	 * @param bool $load True to eager load the field.
+	 * @return $this
+	 */
+	public function eagerLoad(bool $load = true): static
+	{
+		$this->eagerLoad = $load;
+		return $this;
+	}
+}
diff --git a/src/EntityPropertyInstance.php b/src/EntityPropertyInstance.php
new file mode 100644
index 0000000..909a420
--- /dev/null
+++ b/src/EntityPropertyInstance.php
@@ -0,0 +1,200 @@
+<?php
+
+namespace Nest\Model;
+
+use Nest\Database\Query\Raw;
+use Nest\Database\Exceptions\UnknownDatabaseException;
+use Nest\Model\Query\EntityQuery;
+use function Nest\Utils\array_first;
+use function Nest\Utils\array_first_or_val;
+use function Nest\Utils\str_snake_singularize;
+
+class EntityPropertyInstance extends ReadableEntityPropertyBlueprint
+{
+	/**
+	 * Goal entity instance.
+	 * @var Entity
+	 */
+	private Entity $entity;
+
+	/**
+	 * Create an entity property instance from an entity property definition.
+	 * @param EntityPropertyBlueprint $entityProperty The entity property to copy from.
+	 */
+	public function __construct(EntityPropertyBlueprint $entityProperty)
+	{
+		// Copy all fields.
+		$this->class = $entityProperty->class;
+		$this->multiple = $entityProperty->multiple;
+		$this->allowInline = $entityProperty->allowInline;
+		$this->mode = $entityProperty->mode;
+		$this->localKey = $entityProperty->localKey;
+		$this->relatedKey = $entityProperty->relatedKey;
+		$this->pivotTable = $entityProperty->pivotTable;
+		$this->pivotLocalKey = $entityProperty->pivotLocalKey;
+		$this->pivotRelatedKey = $entityProperty->pivotRelatedKey;
+		$this->eagerLoad = $entityProperty->eagerLoad;
+
+		// Initialize goal entity.
+		$this->entity = new ($this->getClass())();
+	}
+
+	/**
+	 * Create a new related entity.
+	 * @return Entity A new related entity instance.
+	 */
+	public function newEntity(): Entity
+	{
+		return $this->entity->new();
+	}
+
+	/**
+	 * Determine if the property can be inline loaded.
+	 * @return bool True if the property can be inline loaded.
+	 */
+	public function canInlineLoad(): bool
+	{
+		return !$this->isMultiple() && $this->isInlineAllowed();
+	}
+
+	/**
+	 * Build a query to retrieve relations for the given entities.
+	 * @param Entity[] $entities Entities for which to retrieve relations.
+	 * @return EntityQuery Built entities query.
+	 * @throws UnknownDatabaseException
+	 */
+	public function queryFor(array $entities): EntityQuery
+	{
+		// Initialize query.
+		$query = $this->entity->query();
+
+		if (empty($entities))
+			// No entities, return a simple query without conditions.
+			return $query;
+
+		// Get a reference entity.
+		$referenceEntity = array_first($entities);
+		// Entity primary key.
+		$entityPrimaryKey = array_first_or_val($referenceEntity->getPrimaryFields());
+
+		// Get keys from entities list.
+		$entitiesKeys = array_column($entities, $entityPrimaryKey);
+
+		switch ($this->getMode())
+		{ // Build query depending on the relation mode.
+			case EntityPropertyMode::LOCAL:
+				$query
+					->select(new Raw("\"{$referenceEntity->getTableName()}\".\"$entityPrimaryKey\" AS \"__reference_key\""))
+					// Generate SELECT for the related entity.
+					->select(...$this->entity->sqlSelectFields())
+					->innerJoin($referenceEntity->getTableName())->on(
+						"{$this->entity->getTableName()}.".(
+							$this->getRelatedKey() ?? array_first_or_val($this->entity->getPrimaryFields())
+						),
+						"=",
+						"{$referenceEntity->getTableName()}.".(
+							$this->getLocalKey() ?? str_snake_singularize($this->entity->getTableName())."_id"
+						),
+					)->whereIn(
+						"{$referenceEntity->getTableName()}.$entityPrimaryKey", $entitiesKeys
+					);
+				break;
+			case EntityPropertyMode::RELATED:
+				$query
+					->select(new Raw("\"{$this->entity->getTableName()}\".\"".(
+							$this->getRelatedKey() ?? str_snake_singularize($referenceEntity->getTableName())."_id"
+						)."\" AS \"__reference_key\""))
+					// Generate SELECT for the related entity.
+					->select(...$this->entity->sqlSelectFields())
+					->whereIn(
+						"{$this->entity->getTableName()}.".(
+							$this->getRelatedKey() ?? str_snake_singularize($referenceEntity->getTableName())."_id"
+						)."",
+						$entitiesKeys
+					);
+				break;
+			case EntityPropertyMode::PIVOT:
+				$query
+					->select(new Raw("\"{$this->entity->getTableName()}\".\"".(
+							$this->getPivotLocalKey() ?? str_snake_singularize($referenceEntity->getTableName())."_id"
+						)."\" AS \"__reference_key\""))
+					// Generate SELECT for the related entity.
+					->select(...$this->entity->sqlSelectFields())
+					->innerJoin($this->getPivotTable())->on(
+						"{$query->getTableName()}.".(
+							$this->getRelatedKey() ?? $query->getPrimaryKeyName()
+						),
+						"=",
+						"{$this->getPivotTable()}.".(
+							$this->getPivotLocalKey() ?? str_snake_singularize($query->getTableName())."_id"
+						),
+					)
+					->whereIn(
+						"{$this->getPivotTable()}.".(
+							$this->getPivotLocalKey() ?? str_snake_singularize($referenceEntity->getTableName())."_id"
+						),
+						$entitiesKeys
+					);
+				break;
+		}
+
+		return $query;
+	}
+
+	/**
+	 * Setup inline loading for the current property in an entity query.
+	 * @param EntityQuery $query The entity query to alter.
+	 * @return void
+	 */
+	public function setupInlineLoading(EntityQuery $query): void
+	{
+		switch ($this->getMode())
+		{ // Add join depending on the relation mode.
+			case EntityPropertyMode::LOCAL:
+				$query
+					->leftJoin($this->entity->getTableName())->on(
+						"{$query->getTableName()}.".(
+							$this->getLocalKey() ?? str_snake_singularize($this->entity->getTableName())."_id"
+						),
+						"=",
+						"{$this->entity->getTableName()}.".(
+							$this->getRelatedKey() ?? array_first_or_val($this->entity->getPrimaryFields())
+						),
+					);
+				break;
+			case EntityPropertyMode::RELATED:
+				$query
+					->leftJoin($this->entity->getTableName())->on(
+						"{$query->getTableName()}.".(
+							$this->getLocalKey() ?? $query->getPrimaryKeyName()
+						),
+						"=",
+						"{$this->entity->getTableName()}.".(
+							$this->getRelatedKey() ?? str_snake_singularize($query->getTableName())."_id"
+						),
+					);
+				break;
+			case EntityPropertyMode::PIVOT:
+				$query
+					->leftJoin($this->getPivotTable())->on(
+						"{$query->getTableName()}.".(
+							$this->getLocalKey() ?? $query->getPrimaryKeyName()
+						),
+						"=",
+						"{$this->getPivotTable()}.".(
+							$this->getPivotLocalKey() ?? str_snake_singularize($query->getTableName())."_id"
+						),
+					)
+					->leftJoin($this->entity->getTableName())->on(
+						"{$this->getPivotTable()}.".(
+							$this->getPivotRelatedKey() ?? str_snake_singularize($this->entity->getTableName())."_id"
+						),
+						"=",
+						"{$this->entity->getTableName()}.".(
+							$this->getRelatedKey() ?? array_first_or_val($this->entity->getPrimaryFields())
+						),
+					);
+				break;
+		}
+	}
+}
diff --git a/src/EntityPropertyMode.php b/src/EntityPropertyMode.php
new file mode 100644
index 0000000..113e6ad
--- /dev/null
+++ b/src/EntityPropertyMode.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model;
+
+enum EntityPropertyMode: string
+{
+	case LOCAL = "local";
+	case RELATED = "related";
+	case PIVOT = "pivot";
+}
diff --git a/src/Events/AfterDelete.php b/src/Events/AfterDelete.php
new file mode 100644
index 0000000..b758847
--- /dev/null
+++ b/src/Events/AfterDelete.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired after entity delete.
+ */
+class AfterDelete extends EntityEvent
+{
+}
diff --git a/src/Events/AfterInsert.php b/src/Events/AfterInsert.php
new file mode 100644
index 0000000..be0df20
--- /dev/null
+++ b/src/Events/AfterInsert.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired after entity insert.
+ */
+class AfterInsert extends EntityEvent
+{
+}
diff --git a/src/Events/AfterLoad.php b/src/Events/AfterLoad.php
new file mode 100644
index 0000000..1d61c65
--- /dev/null
+++ b/src/Events/AfterLoad.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Nest\Model\Events;
+
+use Nest\Model\Entity;
+use Nest\Model\Query\EntityQuery;
+
+/**
+ * Event fired after entity relations load.
+ */
+class AfterLoad extends EntityEvent
+{
+	/**
+	 * @param Entity $entity The entity on which the event is fired.
+	 * @param array<string, callable(EntityQuery): void|true> $relations Loaded relations.
+	 */
+	public function __construct(Entity $entity, public readonly array $relations)
+	{
+		parent::__construct($entity);
+	}
+}
diff --git a/src/Events/AfterPropertiesInitialization.php b/src/Events/AfterPropertiesInitialization.php
new file mode 100644
index 0000000..609abbf
--- /dev/null
+++ b/src/Events/AfterPropertiesInitialization.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired after entity properties initialization.
+ */
+class AfterPropertiesInitialization extends EntityEvent
+{
+}
diff --git a/src/Events/AfterSave.php b/src/Events/AfterSave.php
new file mode 100644
index 0000000..25a5e49
--- /dev/null
+++ b/src/Events/AfterSave.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired after entity save.
+ */
+class AfterSave extends EntityEvent
+{
+}
diff --git a/src/Events/AfterUpdate.php b/src/Events/AfterUpdate.php
new file mode 100644
index 0000000..e9c6351
--- /dev/null
+++ b/src/Events/AfterUpdate.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired after entity update.
+ */
+class AfterUpdate extends EntityEvent
+{
+}
diff --git a/src/Events/BeforeDelete.php b/src/Events/BeforeDelete.php
new file mode 100644
index 0000000..df0c788
--- /dev/null
+++ b/src/Events/BeforeDelete.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired before entity delete.
+ */
+class BeforeDelete extends EntityEvent
+{
+}
diff --git a/src/Events/BeforeInsert.php b/src/Events/BeforeInsert.php
new file mode 100644
index 0000000..6dca9a2
--- /dev/null
+++ b/src/Events/BeforeInsert.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired before entity insert.
+ */
+class BeforeInsert extends EntityEvent
+{
+}
diff --git a/src/Events/BeforeLoad.php b/src/Events/BeforeLoad.php
new file mode 100644
index 0000000..ef3a3a3
--- /dev/null
+++ b/src/Events/BeforeLoad.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Nest\Model\Events;
+
+use Nest\Model\Entity;
+use Nest\Model\Query\EntityQuery;
+
+/**
+ * Event fired before entity relations load.
+ */
+class BeforeLoad extends EntityEvent
+{
+	/**
+	 * @param Entity $entity The entity on which the event is fired.
+	 * @param array<string, callable(EntityQuery): void|true> $relations Relations to load.
+	 */
+	public function __construct(Entity $entity, public readonly array $relations)
+	{
+		parent::__construct($entity);
+	}
+}
diff --git a/src/Events/BeforePropertiesInitialization.php b/src/Events/BeforePropertiesInitialization.php
new file mode 100644
index 0000000..bffefda
--- /dev/null
+++ b/src/Events/BeforePropertiesInitialization.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired before entity properties initialization.
+ */
+class BeforePropertiesInitialization extends EntityEvent
+{
+}
diff --git a/src/Events/BeforeSave.php b/src/Events/BeforeSave.php
new file mode 100644
index 0000000..3c5dc60
--- /dev/null
+++ b/src/Events/BeforeSave.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired before entity save.
+ */
+class BeforeSave extends EntityEvent
+{
+}
diff --git a/src/Events/BeforeUpdate.php b/src/Events/BeforeUpdate.php
new file mode 100644
index 0000000..68a4dda
--- /dev/null
+++ b/src/Events/BeforeUpdate.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired before entity update.
+ */
+class BeforeUpdate extends EntityEvent
+{
+}
diff --git a/src/Events/EntityDefinitionEvent.php b/src/Events/EntityDefinitionEvent.php
new file mode 100644
index 0000000..f77783b
--- /dev/null
+++ b/src/Events/EntityDefinitionEvent.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Nest\Model\Events;
+
+/**
+ * Event fired when the entity definition function has been called.
+ */
+class EntityDefinitionEvent extends EntityEvent
+{
+}
diff --git a/src/Events/EntityEvent.php b/src/Events/EntityEvent.php
new file mode 100644
index 0000000..9311d9f
--- /dev/null
+++ b/src/Events/EntityEvent.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Nest\Model\Events;
+
+use Nest\Model\Entity;
+
+/**
+ * Any entity event.
+ */
+abstract class EntityEvent extends ModelEvent
+{
+	/**
+	 * @param Entity $entity The entity on which the event is fired.
+	 */
+	public function __construct(public readonly Entity $entity)
+	{}
+}
diff --git a/src/Events/ModelEvent.php b/src/Events/ModelEvent.php
new file mode 100644
index 0000000..2568319
--- /dev/null
+++ b/src/Events/ModelEvent.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace Nest\Model\Events;
+
+use Nest\Events\Event;
+
+/**
+ * Any model event.
+ */
+abstract class ModelEvent extends Event
+{
+}
diff --git a/src/Exceptions/MissingRequiredFieldException.php b/src/Exceptions/MissingRequiredFieldException.php
new file mode 100644
index 0000000..ed9a6c2
--- /dev/null
+++ b/src/Exceptions/MissingRequiredFieldException.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Nest\Model\Exceptions;
+
+use Throwable;
+
+/**
+ * Exception thrown when a required field of a model is missing.
+ */
+class MissingRequiredFieldException extends ModelException
+{
+	/**
+	 * @param string[] $missingFields Names of required fields that are missing.
+	 * @param int $code [optional] The Exception code.
+	 * @param null|Throwable $previous [optional] The previous throwable used for the exception chaining.
+	 */
+	public function __construct(public array $missingFields, int $code = 0, ?Throwable $previous = null)
+	{
+		parent::__construct("The following fields are required: ".implode(", ", $this->missingFields), $code, $previous);
+	}
+}
diff --git a/src/Exceptions/ModelException.php b/src/Exceptions/ModelException.php
new file mode 100644
index 0000000..343d774
--- /dev/null
+++ b/src/Exceptions/ModelException.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace Nest\Model\Exceptions;
+
+use Nest\Exceptions\Exception;
+
+class ModelException extends Exception
+{
+}
diff --git a/src/Exceptions/UndefinedRelationException.php b/src/Exceptions/UndefinedRelationException.php
new file mode 100644
index 0000000..ef676cf
--- /dev/null
+++ b/src/Exceptions/UndefinedRelationException.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Nest\Model\Exceptions;
+
+use Throwable;
+
+/**
+ * Exception thrown when a requested relation is undefined.
+ */
+class UndefinedRelationException extends ModelException
+{
+	/**
+	 * @param string $modelClass Class of the model where the relation is undefined.
+	 * @param string $relationName Name of the undefined relation.
+	 * @param int $code [optional] The Exception code.
+	 * @param null|Throwable $previous [optional] The previous throwable used for the exception chaining.
+	 */
+	public function __construct(public readonly string $modelClass, public readonly string $relationName, int $code = 0, ?Throwable $previous = null)
+	{
+		parent::__construct("Undefined relation $this->relationName in $this->modelClass.", $code, $previous);
+	}
+}
diff --git a/src/Exceptions/UnhandledPropertyTypeException.php b/src/Exceptions/UnhandledPropertyTypeException.php
new file mode 100644
index 0000000..cacae5c
--- /dev/null
+++ b/src/Exceptions/UnhandledPropertyTypeException.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Nest\Model\Exceptions;
+
+use Throwable;
+
+/**
+ * Thrown when a property with an unhandled type has been provided.
+ */
+class UnhandledPropertyTypeException extends ModelException
+{
+	/**
+	 * @param string $propertyName Name of the provided property.
+	 * @param class-string $propertyType Class name of the unhandled property type.
+	 * @param int $code [optional] The Exception code.
+	 * @param null|Throwable $previous [optional] The previous throwable used for the exception chaining.
+	 */
+	public function __construct(public readonly string $propertyName, public readonly string $propertyType, int $code = 0, ?Throwable $previous = null)
+	{
+		parent::__construct("Unhandled property $this->propertyName of type $this->propertyType.", $code, $previous);
+	}
+}
diff --git a/src/FieldBlueprint.php b/src/FieldBlueprint.php
new file mode 100644
index 0000000..0061a09
--- /dev/null
+++ b/src/FieldBlueprint.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace Nest\Model;
+
+abstract class FieldBlueprint
+{
+	protected string $type;
+
+	protected bool $primary = false;
+
+	protected bool $index = false;
+
+	protected bool $unique = false;
+
+	protected bool $required = false;
+
+	protected bool $autoIncrement = false;
+
+	protected bool $unsigned = false;
+
+	protected bool $currentDateByDefault = false;
+	protected bool $currentDateOnUpdate = false;
+
+	public function type(string $type): static
+	{
+		$this->type = $type;
+		return $this;
+	}
+
+	public function primary(bool $primary = true): static
+	{
+		$this->primary = $primary;
+		return $this;
+	}
+
+	public function index(bool $index = true): static
+	{
+		$this->index = $index;
+		return $this;
+	}
+
+	public function unique(bool $unique = true): static
+	{
+		$this->unique = $unique;
+		return $this;
+	}
+
+	public function required(bool $required = true): static
+	{
+		$this->required = $required;
+		return $this;
+	}
+
+	public function autoIncrement(bool $autoIncrement = true): static
+	{
+		$this->autoIncrement = $autoIncrement;
+		return $this;
+	}
+
+	public function unsigned(bool $unsigned = true): static
+	{
+		$this->unsigned = $unsigned;
+		return $this;
+	}
+
+	public function currentDateByDefault(bool $currentDateByDefault = true): static
+	{
+		$this->currentDateByDefault = $currentDateByDefault;
+		return $this;
+	}
+
+	public function currentDateOnUpdate(bool $currentDateOnUpdate = true): static
+	{
+		$this->currentDateOnUpdate = $currentDateOnUpdate;
+		return $this;
+	}
+}
diff --git a/src/Query/EntityQuery.php b/src/Query/EntityQuery.php
new file mode 100644
index 0000000..5f585ee
--- /dev/null
+++ b/src/Query/EntityQuery.php
@@ -0,0 +1,344 @@
+<?php
+
+namespace Nest\Model\Query;
+
+use Nest\Database\Database;
+use Nest\Database\Query\SelectQuery;
+use Nest\Database\Exceptions\Query\MissingConditionValueException;
+use Nest\Database\Exceptions\UnknownDatabaseException;
+use Nest\Exceptions\InvalidTypeException;
+use Nest\Model\Exceptions\UndefinedRelationException;
+use Nest\Model\Exceptions\UnhandledPropertyTypeException;
+use Nest\Types\Exceptions\IncompatibleTypeException;
+use Nest\Model\Entity;
+use function Nest\Utils\array_first;
+use function Nest\Utils\array_first_or_val;
+
+/**
+ * Query builder for an entity.
+ * @template Entity
+ */
+class EntityQuery extends SelectQuery
+{
+	/**
+	 * Normalize a relations definition array.
+	 * @param array<string|int, string|callable(EntityQuery): void> $relations Relations to normalize.
+	 * @return array<string, (callable(EntityQuery): void)|true> Relations definition.
+	 */
+	public static function normalizeRelationsDefinition(array $relations): array
+	{
+		// Normalize relations array.
+		foreach ($relations as $key => $relation)
+		{ // Add each relation to eager load to the with array.
+			if (!is_string($key))
+			{ // If key is an integer, then $relation is a string key.
+				$relations[$relation] = true;
+				unset($relations[$key]);
+			}
+		}
+
+		// Return normalized relations array.
+		return $relations;
+	}
+
+	/**
+	 * Relations that should be eager loaded.
+	 * @var array<string, (callable(EntityQuery): void)|true>
+	 */
+	protected array $with = [];
+
+	/**
+	 * @inheritDoc
+	 * @param Entity $entity Reference entity.
+	 */
+	public function __construct(Database $database, string $table, protected Entity $entity)
+	{
+		parent::__construct($database, $table);
+	}
+
+	/**
+	 * Create a new entity instance.
+	 * @return Entity Entity instance.
+	 */
+	protected function newEntity(): Entity
+	{
+		// Create a new entity instance.
+		return $this->entity->new();
+	}
+
+	/**
+	 * Get queried entity primary key name.
+	 * @return string Primary key name.
+	 */
+	public function getPrimaryKeyName(): string
+	{
+		return array_first_or_val($this->entity->getPrimaryFields());
+	}
+
+	/**
+	 * Add a where condition for the primary key of the entity.
+	 * @param mixed|array $keyValue Entity primary key value(s) to match.
+	 * @return $this
+	 */
+	public function whereKey(mixed $keyValue): static
+	{
+		return $this->whereIn($this->getPrimaryKeyName(), is_array($keyValue) ? $keyValue : [$keyValue]);
+	}
+
+	/**
+	 * Make a relation prefix for the given relation.
+	 * @param string $relationKey Relation key.
+	 * @return string Relation prefix.
+	 */
+	private function getRelationPrefix(string $relationKey): string
+	{
+		return "{$this->entity->getTableName()}_{$relationKey}_";
+	}
+
+	/**
+	 * Go through all first-level relations to eager load and add joins and selected columns for them.
+	 * @param bool $generateSelect Set if SELECTed columns must be generated or not.
+	 * @return string[] Loaded inline relations.
+	 * @throws UndefinedRelationException
+	 */
+	private function addInlineRelations(bool $generateSelect): array
+	{
+		if (empty($this->with)) return [];
+
+		// Initialize list of inline loaded relations.
+		$inlineRelations = [];
+
+		foreach ($this->with as $relationKey => $relationCallable)
+		{ // For each relation, if it's inline, append a JOIN and SELECT for it.
+			// Get the required relation.
+			$relation = $this->entity->getRelation($relationKey);
+			if ($relation->canInlineLoad())
+			{ // If the relation is not multiple, it can be retrieved inline.
+				$relation->setupInlineLoading($this);
+
+				if ($generateSelect)
+					// Generate SELECT for the relation.
+					$this->select(...$relation->newEntity()->sqlSelectFields($this->getRelationPrefix($relationKey)));
+
+				if (is_callable($relationCallable))
+					// Call the callable with the alterable query.
+					$relationCallable($this);
+
+				// Add to inline loaded relations.
+				$inlineRelations[] = $relationKey;
+			}
+		}
+
+		return $inlineRelations;
+	}
+
+	/**
+	 * Get queried entities.
+	 * @param string|null $indexProperty A property to use as entities array index.
+	 * @return Entity[]|array<mixed, Entity[]> Retrieved entities.
+	 * @throws MissingConditionValueException
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws UndefinedRelationException
+	 * @throws UnknownDatabaseException
+	 * @throws UnhandledPropertyTypeException
+	 */
+	public function get(?string $indexProperty = null): array
+	{
+		// If there's no custom SELECT, generate it.
+		$generateSelect = empty($this->selected);
+
+		if ($generateSelect)
+			// Generate SELECT for the main entity.
+			$this->select(...$this->entity->sqlSelectFields());
+
+		// Add inline relations retrieval to the query.
+		$inlineRelations = $this->addInlineRelations($generateSelect);
+
+		// Map entities with their inline relations, if there are some.
+		$entities = $this->mapEntities($this->execute(), $inlineRelations, $indexProperty);
+
+		// Load all remaining relations (remove already loaded inline relations).
+		$relationsToLoad = $this->with ?? [];
+		foreach ($inlineRelations as $inlineRelation)
+			unset($relationsToLoad[$inlineRelation]);
+
+		$this->load($entities, $relationsToLoad);
+
+		return $entities;
+	}
+
+	/**
+	 * Retrieve the entities with the given keys.
+	 * @param mixed[] $keysValues Entity primary keys values to match.
+	 * @return Entity[] Retrieved entities.
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws MissingConditionValueException
+	 * @throws UndefinedRelationException
+	 * @throws UnhandledPropertyTypeException
+	 * @throws UnknownDatabaseException
+	 */
+	public function findMany(array $keysValues): array
+	{
+		return $this->whereKey($keysValues)->get();
+	}
+
+	/**
+	 * Retrieve the first entity of the query.
+	 * @return Entity Retrieved entity.
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws MissingConditionValueException
+	 * @throws UndefinedRelationException
+	 * @throws UnhandledPropertyTypeException
+	 * @throws UnknownDatabaseException
+	 */
+	public function first(): Entity
+	{
+		return array_first($this->limit(1)->get());
+	}
+
+	/**
+	 * Retrieve the entity with the given key.
+	 * @param mixed $keyValue Primary key value of the entity.
+	 * @return Entity Retrieved entity.
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws MissingConditionValueException
+	 * @throws UndefinedRelationException
+	 * @throws UnhandledPropertyTypeException
+	 * @throws UnknownDatabaseException
+	 */
+	public function find(mixed $keyValue): Entity
+	{
+		return $this->whereKey($keyValue)->first();
+	}
+
+	/**
+	 * Map raw objects results to entities.
+	 * @param object[] $objects Raw objects results.
+	 * @param string[] $inlineRelations Inline relations to map, if there are some.
+	 * @return Entity[] The entities.
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws UndefinedRelationException
+	 * @throws UnhandledPropertyTypeException
+	 */
+	protected function mapEntities(array $objects, array $inlineRelations = [], ?string $indexProperty = null): array
+	{
+		// Initialize entities array.
+		$entities = [];
+
+		foreach ($objects as $object)
+		{ // Map each object to an entity.
+			$entity = $this->mapEntity($object);
+
+			// Append to entities array, depending on index property name.
+			if (empty($indexProperty))
+				$entities[] = $entity;
+			else
+			{
+				if (empty($object->$indexProperty)) $object->$indexProperty = [];
+				$entities[$object->$indexProperty][] = $entity;
+			}
+
+			// Map inline relations.
+			foreach ($inlineRelations as $inlineRelation)
+			{ // For each inline relation, map its data.
+				$relation = $this->entity->getRelation($inlineRelation);
+				// Create a new entity as property value.
+				$propertyValue = $relation->newEntity();
+				$propertyValue->fromSqlProperties($object, $this->getRelationPrefix($inlineRelation));
+
+				// Set the relation property.
+				$entity->setOriginalProperty($inlineRelation, $propertyValue);
+			}
+		}
+
+		// Return parsed entities.
+		return $entities;
+	}
+
+	/**
+	 * Map raw object result to an entity.
+	 * @param object $object Raw object.
+	 * @return Entity The entity.
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 */
+	protected function mapEntity(object $object): Entity
+	{
+		// Create a new entity.
+		$entity = $this->newEntity();
+
+		// Read entity from SQL properties.
+		$entity->fromSqlProperties($object);
+
+		// Return parsed entity.
+		return $entity;
+	}
+
+	/**
+	 * Eager load given relations.
+	 * @param Entity[] $entities Entities for which to load relations.
+	 * @param array<string, callable(EntityQuery): void|true> $relationsToLoad Relations to load.
+	 * @return void
+	 * @throws IncompatibleTypeException
+	 * @throws InvalidTypeException
+	 * @throws MissingConditionValueException
+	 * @throws UndefinedRelationException
+	 * @throws UnknownDatabaseException
+	 * @throws UnhandledPropertyTypeException
+	 */
+	public function load(array $entities, array $relationsToLoad): void
+	{
+		foreach ($relationsToLoad as $relationKey => $relationCallable)
+		{ // For each relation to load...
+			// Get relation instance.
+			$relation = $this->entity->getRelation($relationKey);
+
+			// Build base query to retrieve relations.
+			$query = $relation->queryFor($entities);
+
+			// Apply query modifier callable.
+			if (is_callable($relationCallable))
+				$relationCallable($query);
+
+			// Retrieve models and associate them with the right entities.
+			$models = $query->get("__reference_key");
+
+			foreach ($entities as &$entity)
+			{ // Associate the retrieved model(s) to every entity.
+				if (!empty($models[$entityId = $entity->{array_first_or_val($entity->getPrimaryFields())}]))
+					$entity->setOriginalProperty($relationKey, $relation->isMultiple() ? $models[$entityId] : array_first($models[$entityId]));
+			}
+		}
+	}
+
+	/**
+	 * Add relations to eager load.
+	 * @param array<string|int, string|callable(EntityQuery): void> $relations Relations that should be eager loaded.
+	 * @return $this
+	 */
+	public function with(array $relations): static
+	{
+		// Normalize relations array and add them in the with array.
+		array_merge($this->with, EntityQuery::normalizeRelationsDefinition($relations));
+		return $this;
+	}
+
+	/**
+	 * Add relations to NOT eager load.
+	 * @param string[] $relations Relations that shouldn't be eager loaded.
+	 * @return $this
+	 */
+	public function without(array $relations): static
+	{
+		foreach ($relations as $relation)
+		{ // For each relation to NOT eager load, remove it from the with array.
+			if (!empty($this->with[$relation])) unset($this->with[$relation]);
+		}
+		return $this;
+	}
+}
diff --git a/src/ReadableArrayBlueprint.php b/src/ReadableArrayBlueprint.php
new file mode 100644
index 0000000..0076005
--- /dev/null
+++ b/src/ReadableArrayBlueprint.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Nest\Model;
+
+use Nest\Types\Type;
+
+class ReadableArrayBlueprint extends ArrayBlueprint
+{
+	public function getType(): string
+	{
+		return $this->type;
+	}
+
+	/**
+	 * Get type instance of the given field.
+	 * @return Type Type instance.
+	 */
+	public function getTypeInstance(): Type
+	{
+		return new $this->type();
+	}
+
+	public function getTable(): ?string
+	{
+		return $this->table;
+	}
+
+	public function getForeignKeyName(): ?string
+	{
+		return $this->foreignKeyName;
+	}
+
+	public function getForeignValueName(): ?string
+	{
+		return $this->foreignValueName;
+	}
+}
diff --git a/src/ReadableEntityPropertyBlueprint.php b/src/ReadableEntityPropertyBlueprint.php
new file mode 100644
index 0000000..d29cb54
--- /dev/null
+++ b/src/ReadableEntityPropertyBlueprint.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Nest\Model;
+
+class ReadableEntityPropertyBlueprint extends EntityPropertyBlueprint
+{
+	public function getClass(): string
+	{
+		return $this->class;
+	}
+
+	public function isMultiple(): bool
+	{
+		return $this->multiple;
+	}
+
+	public function isInlineAllowed(): bool
+	{
+		return $this->allowInline;
+	}
+
+	public function getMode(): EntityPropertyMode
+	{
+		return $this->mode;
+	}
+
+	public function getLocalKey(): ?string
+	{
+		return $this->localKey;
+	}
+
+	public function getRelatedKey(): ?string
+	{
+		return $this->relatedKey;
+	}
+
+	public function getPivotTable(): ?string
+	{
+		return $this->pivotTable;
+	}
+
+	public function getPivotLocalKey(): ?string
+	{
+		return $this->pivotLocalKey;
+	}
+
+	public function getPivotRelatedKey(): ?string
+	{
+		return $this->pivotRelatedKey;
+	}
+
+	/**
+	 * @return bool True if the field should be eager loaded.
+	 */
+	public function doEagerLoad(): bool
+	{
+		return $this->eagerLoad;
+	}
+}
diff --git a/src/ReadableFieldBlueprint.php b/src/ReadableFieldBlueprint.php
new file mode 100644
index 0000000..0702583
--- /dev/null
+++ b/src/ReadableFieldBlueprint.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace Nest\Model;
+
+use Nest\Types\Type;
+
+class ReadableFieldBlueprint extends FieldBlueprint
+{
+	public function getType(): string
+	{
+		return $this->type;
+	}
+
+	/**
+	 * Get type instance of the given field.
+	 * @return Type Type instance.
+	 */
+	public function getTypeInstance(): Type
+	{
+		return new $this->type();
+	}
+
+	public function isPrimary(): bool
+	{
+		return $this->primary;
+	}
+
+	public function isIndexed(): bool
+	{
+		return $this->index;
+	}
+
+	public function isUnique(): bool
+	{
+		return $this->unique;
+	}
+
+	public function isRequired(): bool
+	{
+		return $this->required;
+	}
+
+	public function isAutoIncrementing(): bool
+	{
+		return $this->autoIncrement;
+	}
+
+	public function isUnsigned(): bool
+	{
+		return $this->unsigned;
+	}
+
+	public function hasCurrentDateByDefault(): bool
+	{
+		return $this->currentDateByDefault;
+	}
+
+	public function hasCurrentDateOnUpdate(): bool
+	{
+		return $this->currentDateOnUpdate;
+	}
+}