Second checkpoint

internal/repository/postgres/category.go

@@ -0,0 +1,104 @@
+package postgres
+
+import (
+	"context"
+
+	"gis/internal/domain"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// CategoryRepository persists categories in Postgres.
+type CategoryRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewCategoryRepository returns a CategoryRepository backed by the given pool.
+func NewCategoryRepository(pool *pgxpool.Pool) *CategoryRepository {
+	return &CategoryRepository{pool: pool}
+}
+
+const categoryColumns = `id, parent_id, name, description, created_at, updated_at`
+
+func scanCategory(row pgx.Row) (domain.Category, error) {
+	var c domain.Category
+	err := row.Scan(&c.ID, &c.ParentID, &c.Name, &c.Description, &c.CreatedAt, &c.UpdatedAt)
+	return c, err
+}
+
+// Create inserts a new category and returns the stored row.
+func (r *CategoryRepository) Create(ctx context.Context, c domain.Category) (domain.Category, error) {
+	row := r.pool.QueryRow(ctx,
+		`INSERT INTO categories (parent_id, name, description)
+		 VALUES ($1, $2, $3)
+		 RETURNING `+categoryColumns,
+		c.ParentID, c.Name, c.Description,
+	)
+	out, err := scanCategory(row)
+	return out, mapError(err)
+}
+
+// GetByID returns the category with the given id, or domain.ErrNotFound.
+func (r *CategoryRepository) GetByID(ctx context.Context, id uuid.UUID) (domain.Category, error) {
+	row := r.pool.QueryRow(ctx,
+		`SELECT `+categoryColumns+` FROM categories WHERE id = $1`, id)
+	out, err := scanCategory(row)
+	return out, mapError(err)
+}
+
+// List returns categories ordered by name. When parentID is non-nil it filters
+// to that parent's direct children; otherwise it returns all categories.
+func (r *CategoryRepository) List(ctx context.Context, parentID *uuid.UUID) ([]domain.Category, error) {
+	var (
+		rows pgx.Rows
+		err  error
+	)
+	if parentID != nil {
+		rows, err = r.pool.Query(ctx,
+			`SELECT `+categoryColumns+` FROM categories WHERE parent_id = $1 ORDER BY name`, *parentID)
+	} else {
+		rows, err = r.pool.Query(ctx,
+			`SELECT `+categoryColumns+` FROM categories ORDER BY name`)
+	}
+	if err != nil {
+		return nil, mapError(err)
+	}
+	defer rows.Close()
+
+	categories := make([]domain.Category, 0)
+	for rows.Next() {
+		c, err := scanCategory(rows)
+		if err != nil {
+			return nil, mapError(err)
+		}
+		categories = append(categories, c)
+	}
+	return categories, mapError(rows.Err())
+}
+
+// Update modifies a category's parent, name, and description.
+func (r *CategoryRepository) Update(ctx context.Context, c domain.Category) (domain.Category, error) {
+	row := r.pool.QueryRow(ctx,
+		`UPDATE categories
+		 SET parent_id = $2, name = $3, description = $4, updated_at = now()
+		 WHERE id = $1
+		 RETURNING `+categoryColumns,
+		c.ID, c.ParentID, c.Name, c.Description,
+	)
+	out, err := scanCategory(row)
+	return out, mapError(err)
+}
+
+// Delete removes a category. Returns domain.ErrNotFound if it does not exist.
+func (r *CategoryRepository) Delete(ctx context.Context, id uuid.UUID) error {
+	tag, err := r.pool.Exec(ctx, `DELETE FROM categories WHERE id = $1`, id)
+	if err != nil {
+		return mapError(err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}