Create generic query result mapper and implement it for PostgreSQL.

+ Add generic query result mapper.
+ Add query result mapper implementation for PostgreSQL.

src/insert.zig

@@ -6,6 +6,7 @@ const database = @import("database.zig");
 const postgresql = @import("postgresql.zig");
 const _sql = @import("sql.zig");
 const repository = @import("repository.zig");
+const _result = @import("result.zig");
 
 /// Type of an insertable column. Insert shape should be composed of only these.
 fn InsertableColumn(comptime ValueType: type) type {
@@ -118,6 +119,9 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 
 		const Configuration = RepositoryInsertConfiguration(InsertShape);
 
+		/// Result mapper type.
+		pub const ResultMapper = _result.ResultMapper(Model, TableShape, repositoryConfig, null, null);
+
 		arena: std.heap.ArenaAllocator,
 		connector: database.Connector,
 		connection: *database.Connection = undefined,
@@ -332,7 +336,8 @@ pub fn RepositoryInsert(comptime Model: type, comptime TableShape: type, comptim
 			defer queryResult.deinit();
 
 			// Map query results.
-			return postgresql.mapResults(Model, TableShape, repositoryConfig, allocator, queryResult);
+			var postgresqlReader = postgresql.QueryResultReader(TableShape, null).init(queryResult);
+			return try ResultMapper.map(allocator, postgresqlReader.reader());
 		}
 
 		/// Initialize a new repository insert query.

src/postgresql.zig

@@ -7,6 +7,7 @@ const database = @import("database.zig");
 const _sql = @import("sql.zig");
 const _relations = @import("relations.zig");
 const repository = @import("repository.zig");
+const _result = @import("result.zig");
 
 /// PostgreSQL query error details.
 pub const PostgresqlError = struct {
@@ -79,32 +80,58 @@ pub fn makeMapper(comptime T: type, result: *pg.Result, allocator: std.mem.Alloc
 	};
 }
 
-/// Generic query results mapping.
-pub fn mapResults(comptime Model: type, comptime TableShape: type,
-	repositoryConfig: repository.RepositoryConfiguration(Model, TableShape),
-	allocator: std.mem.Allocator, queryResult: *pg.Result) !repository.RepositoryResult(Model)
-{
-	//TODO make a generic mapper and do it in repository.zig?
-	// Create an arena for mapper data.
-	var mapperArena = std.heap.ArenaAllocator.init(allocator);
-	// Get result mapper.
-	const mapper = try makeMapper(TableShape, queryResult, mapperArena.allocator(), null);
+pub fn QueryResultReader(comptime TableShape: type, comptime inlineRelations: ?[]const _relations.ModelRelation) type {
+	const InstanceInterface = _result.QueryResultReader(TableShape, inlineRelations).Instance;
 
-	// Initialize models list.
-	var models = std.ArrayList(*Model).init(allocator);
-	defer models.deinit();
+	return struct {
+		const Self = @This();
 
-	// Get all raw models from the result mapper.
-	while (try mapper.next()) |rawModel| {
-		// Parse each raw model from the mapper.
-		const model = try allocator.create(Model);
-		model.* = try repositoryConfig.fromSql(rawModel);
-		try models.append(model);
+		pub const Instance = struct {
+			/// Main object mapper.
+			mainMapper: pg.Mapper(TableShape) = undefined,
+
+			fn next(opaqueSelf: *anyopaque) !?TableShape { //TODO inline relations.
+				const self: *Instance = @ptrCast(@alignCast(opaqueSelf));
+				return try self.mainMapper.next();
 			}
 
-	// Return a result with the models.
-	return repository.RepositoryResult(Model).init(allocator,
-		zollections.Collection(Model).init(allocator, try models.toOwnedSlice()),
-		mapperArena,
-	);
+			pub fn instance(self: *Instance, allocator: std.mem.Allocator) InstanceInterface {
+				return .{
+					.__interface = .{
+						.instance = self,
+						.next = next,
+					},
+
+					.allocator = allocator,
+				};
+			}
+		};
+
+		instance: Instance = Instance{},
+
+		/// The PostgreSQL query result.
+		result: *pg.Result,
+
+		fn initInstance(opaqueSelf: *anyopaque, allocator: std.mem.Allocator) !InstanceInterface {
+			const self: *Self = @ptrCast(@alignCast(opaqueSelf));
+			self.instance.mainMapper = try makeMapper(TableShape, self.result, allocator, null);
+			return self.instance.instance(allocator);
+		}
+
+		pub fn reader(self: *Self) _result.QueryResultReader(TableShape, inlineRelations) {
+			return .{
+				._interface = .{
+					.instance = self,
+					.init = initInstance,
+				},
+			};
+		}
+
+		/// Initialize a PostgreSQL query result reader from the given query result.
+		pub fn init(result: *pg.Result) Self {
+			return .{
+				.result = result,
+			};
+		}
+	};
 }

src/query.zig

@@ -9,6 +9,7 @@ const _conditions = @import("conditions.zig");
 const relations = @import("relations.zig");
 const repository = @import("repository.zig");
 const _comptime = @import("comptime.zig");
+const _result = @import("result.zig");
 
 /// Repository query configuration structure.
 pub const RepositoryQueryConfiguration = struct {
@@ -19,6 +20,8 @@ pub const RepositoryQueryConfiguration = struct {
 
 /// Compiled relations structure.
 const CompiledRelations = struct {
+	inlineRelations: []relations.ModelRelation,
+	otherRelations: []relations.ModelRelation,
 	inlineSelect: []const u8,
 	inlineJoins: []const u8,
 };
@@ -58,11 +61,15 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 			}
 
 			break :compile CompiledRelations{
+				.inlineRelations = inlineRelations,
+				.otherRelations = &[0]relations.ModelRelation{},
 				.inlineSelect = if (inlineSelect.len > 0) ", " ++ _comptime.join(", ", inlineSelect) else "",
 				.inlineJoins = if (inlineJoins.len > 0) " " ++ _comptime.join(" ", inlineJoins) else "",
 			};
 		} else {
 			break :compile CompiledRelations{
+				.inlineRelations = &[0]relations.ModelRelation{},
+				.otherRelations = &[0]relations.ModelRelation{},
 				.inlineSelect = "",
 				.inlineJoins = "",
 			};
@@ -80,6 +87,9 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 	return struct {
 		const Self = @This();
 
+		/// Result mapper type.
+		pub const ResultMapper = _result.ResultMapper(Model, TableShape, repositoryConfig, compiledRelations.inlineRelations, compiledRelations.otherRelations);
+
 		arena: std.heap.ArenaAllocator,
 		connector: database.Connector,
 		connection: *database.Connection = undefined,
@@ -286,7 +296,8 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 			defer queryResult.deinit();
 
 			// Map query results.
-			return postgresql.mapResults(Model, TableShape, repositoryConfig, allocator, queryResult);
+			var postgresqlReader = postgresql.QueryResultReader(TableShape, compiledRelations.inlineRelations).init(queryResult);
+			return try ResultMapper.map(allocator, postgresqlReader.reader());
 		}
 
 		/// Initialize a new repository query.

src/result.zig

@@ -0,0 +1,72 @@
+const std = @import("std");
+const zollections = @import("zollections");
+const _repository = @import("repository.zig");
+const _relations = @import("relations.zig");
+
+/// Generic interface of a query result reader.
+pub fn QueryResultReader(comptime TableShape: type, comptime inlineRelations: ?[]const _relations.ModelRelation) type {
+	_ = inlineRelations;
+	return struct {
+		const Self = @This();
+
+		/// Generic interface of a query result reader instance.
+		pub const Instance = struct {
+			__interface: struct {
+				instance: *anyopaque,
+				next: *const fn (self: *anyopaque) anyerror!?TableShape, //TODO inline relations.
+			},
+
+			allocator: std.mem.Allocator,
+
+			pub fn next(self: Instance) !?TableShape {
+				return self.__interface.next(self.__interface.instance);
+			}
+		};
+
+		_interface: struct {
+			instance: *anyopaque,
+			init: *const fn (self: *anyopaque, allocator: std.mem.Allocator) anyerror!Instance,
+		},
+
+		/// Initialize a reader instance.
+		pub fn init(self: Self, allocator: std.mem.Allocator) !Instance {
+			return self._interface.init(self._interface.instance, allocator);
+		}
+	};
+}
+
+/// Map query result to repository model structures, and load the given relations.
+pub fn ResultMapper(comptime Model: type, comptime TableShape: type, comptime repositoryConfig: _repository.RepositoryConfiguration(Model, TableShape), comptime inlineRelations: ?[]const _relations.ModelRelation, comptime relations: ?[]const _relations.ModelRelation) type {
+	_ = relations;
+	return struct {
+		/// Map the query result to a repository result, with all the required relations.
+		pub fn map(allocator: std.mem.Allocator, queryReader: QueryResultReader(TableShape, inlineRelations)) !_repository.RepositoryResult(Model) {
+			// Create an arena for mapper data.
+			var mapperArena = std.heap.ArenaAllocator.init(allocator);
+
+			// Initialize query result reader.
+			const reader = try queryReader.init(mapperArena.allocator());
+
+			// Initialize models list.
+			var models = std.ArrayList(*Model).init(allocator);
+			defer models.deinit();
+
+			// Get all raw models from the result reader.
+			while (try reader.next()) |rawModel| {
+				// Parse each raw model from the reader.
+				const model = try allocator.create(Model);
+				model.* = try repositoryConfig.fromSql(rawModel);
+				//TODO inline relations.
+				try models.append(model);
+			}
+
+			//TODO load relations?
+
+			// Return a result with the models.
+			return _repository.RepositoryResult(Model).init(allocator,
+				zollections.Collection(Model).init(allocator, try models.toOwnedSlice()),
+				mapperArena,
+			);
+		}
+	};
+}

src/update.zig

@@ -7,6 +7,7 @@ const postgresql = @import("postgresql.zig");
 const _sql = @import("sql.zig");
 const conditions = @import("conditions.zig");
 const repository = @import("repository.zig");
+const _result = @import("result.zig");
 
 /// Repository update query configuration structure.
 pub fn RepositoryUpdateConfiguration(comptime UpdateShape: type) type {
@@ -57,6 +58,9 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 
 		const Configuration = RepositoryUpdateConfiguration(UpdateShape);
 
+		/// Result mapper type.
+		pub const ResultMapper = _result.ResultMapper(Model, TableShape, repositoryConfig, null, null);
+
 		arena: std.heap.ArenaAllocator,
 		connector: database.Connector,
 		connection: *database.Connection = undefined,
@@ -301,7 +305,8 @@ pub fn RepositoryUpdate(comptime Model: type, comptime TableShape: type, comptim
 			defer queryResult.deinit();
 
 			// Map query results.
-			return postgresql.mapResults(Model, TableShape, repositoryConfig, allocator, queryResult);
+			var postgresqlReader = postgresql.QueryResultReader(TableShape, null).init(queryResult);
+			return try ResultMapper.map(allocator, postgresqlReader.reader());
 		}
 
 		/// Initialize a new repository update query.