package diary

import (
	"context"
	"errors"
	"fmt"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// ErrNotFound is returned when a diary entry does not exist for the user.
var ErrNotFound = errors.New("diary entry not found")

// Repository handles persistence for meal diary entries.
type Repository struct {
	pool *pgxpool.Pool
}

// NewRepository creates a new Repository.
func NewRepository(pool *pgxpool.Pool) *Repository {
	return &Repository{pool: pool}
}

// ListByDate returns all diary entries for a user on a given date (YYYY-MM-DD).
func (r *Repository) ListByDate(ctx context.Context, userID, date string) ([]*Entry, error) {
	rows, err := r.pool.Query(ctx, `
		SELECT id, date::text, meal_type, name, portions,
		       calories, protein_g, fat_g, carbs_g,
		       source, recipe_id, created_at
		FROM meal_diary
		WHERE user_id = $1 AND date = $2::date
		ORDER BY created_at ASC`, userID, date)
	if err != nil {
		return nil, fmt.Errorf("list diary: %w", err)
	}
	defer rows.Close()

	var result []*Entry
	for rows.Next() {
		e, err := scanEntry(rows)
		if err != nil {
			return nil, fmt.Errorf("scan diary entry: %w", err)
		}
		result = append(result, e)
	}
	return result, rows.Err()
}

// Create inserts a new diary entry and returns the stored record.
func (r *Repository) Create(ctx context.Context, userID string, req CreateRequest) (*Entry, error) {
	portions := req.Portions
	if portions <= 0 {
		portions = 1
	}
	source := req.Source
	if source == "" {
		source = "manual"
	}

	row := r.pool.QueryRow(ctx, `
		INSERT INTO meal_diary (user_id, date, meal_type, name, portions,
		    calories, protein_g, fat_g, carbs_g, source, recipe_id)
		VALUES ($1, $2::date, $3, $4, $5, $6, $7, $8, $9, $10, $11)
		RETURNING id, date::text, meal_type, name, portions,
		    calories, protein_g, fat_g, carbs_g, source, recipe_id, created_at`,
		userID, req.Date, req.MealType, req.Name, portions,
		req.Calories, req.ProteinG, req.FatG, req.CarbsG,
		source, req.RecipeID,
	)
	return scanEntry(row)
}

// Delete removes a diary entry for the given user.
func (r *Repository) Delete(ctx context.Context, id, userID string) error {
	tag, err := r.pool.Exec(ctx,
		`DELETE FROM meal_diary WHERE id = $1 AND user_id = $2`, id, userID)
	if err != nil {
		return fmt.Errorf("delete diary entry: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// --- helpers ---

type scannable interface {
	Scan(dest ...any) error
}

func scanEntry(s scannable) (*Entry, error) {
	var e Entry
	err := s.Scan(
		&e.ID, &e.Date, &e.MealType, &e.Name, &e.Portions,
		&e.Calories, &e.ProteinG, &e.FatG, &e.CarbsG,
		&e.Source, &e.RecipeID, &e.CreatedAt,
	)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	return &e, err
}