package diary

import (
	"context"
	"errors"
	"fmt"

	"github.com/food-ai/backend/internal/infra/locale"
	"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).
// Supports both dish-based and catalog product-based entries.
func (r *Repository) ListByDate(ctx context.Context, userID, date string) ([]*Entry, error) {
	lang := locale.FromContext(ctx)
	rows, err := r.pool.Query(ctx, `
		SELECT
			md.id, md.date::text, md.meal_type, md.portions,
			md.source, md.dish_id::text, md.product_id::text, md.recipe_id::text, md.portion_g, md.job_id::text, md.created_at,
			COALESCE(dt.name, d.name, p.canonical_name) AS entry_name,
			COALESCE(
				r.calories_per_serving * md.portions,
				p.calories_per_100g   * md.portion_g / 100
			),
			COALESCE(
				r.protein_per_serving * md.portions,
				p.protein_per_100g   * md.portion_g / 100
			),
			COALESCE(
				r.fat_per_serving * md.portions,
				p.fat_per_100g   * md.portion_g / 100
			),
			COALESCE(
				r.carbs_per_serving * md.portions,
				p.carbs_per_100g   * md.portion_g / 100
			)
		FROM meal_diary md
		LEFT JOIN dishes d ON d.id = md.dish_id
		LEFT JOIN dish_translations dt ON dt.dish_id = d.id AND dt.lang = $3
		LEFT JOIN recipes r ON r.id = md.recipe_id
		LEFT JOIN products p ON p.id = md.product_id
		WHERE md.user_id = $1 AND md.date = $2::date
		ORDER BY md.created_at ASC`, userID, date, lang)
	if err != nil {
		return nil, fmt.Errorf("list diary: %w", err)
	}
	defer rows.Close()

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

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

	var entryID string
	insertError := r.pool.QueryRow(ctx, `
		INSERT INTO meal_diary (user_id, date, meal_type, portions, source, dish_id, product_id, recipe_id, portion_g, job_id)
		VALUES ($1, $2::date, $3, $4, $5, $6, $7, $8, $9, $10)
		RETURNING id`,
		userID, req.Date, req.MealType, portions, source, req.DishID, req.ProductID, req.RecipeID, req.PortionG, req.JobID,
	).Scan(&entryID)
	if insertError != nil {
		return nil, fmt.Errorf("insert diary entry: %w", insertError)
	}

	row := r.pool.QueryRow(ctx, `
		SELECT
			md.id, md.date::text, md.meal_type, md.portions,
			md.source, md.dish_id::text, md.product_id::text, md.recipe_id::text, md.portion_g, md.job_id::text, md.created_at,
			COALESCE(dt.name, d.name, p.canonical_name) AS entry_name,
			COALESCE(
				r.calories_per_serving * md.portions,
				p.calories_per_100g   * md.portion_g / 100
			),
			COALESCE(
				r.protein_per_serving * md.portions,
				p.protein_per_100g   * md.portion_g / 100
			),
			COALESCE(
				r.fat_per_serving * md.portions,
				p.fat_per_100g   * md.portion_g / 100
			),
			COALESCE(
				r.carbs_per_serving * md.portions,
				p.carbs_per_100g   * md.portion_g / 100
			)
		FROM meal_diary md
		LEFT JOIN dishes d ON d.id = md.dish_id
		LEFT JOIN dish_translations dt ON dt.dish_id = d.id AND dt.lang = $2
		LEFT JOIN recipes r ON r.id = md.recipe_id
		LEFT JOIN products p ON p.id = md.product_id
		WHERE md.id = $1`, entryID, lang)
	return scanEntry(row)
}

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

// --- helpers ---

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

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