package repository

import (
	"context"
	"errors"
	"time"

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

const imageCardDailyFree = 3

// ImageCardRepo tracks daily draw quotas.
type ImageCardRepo struct {
	Pool *pgxpool.Pool
}

// UsedToday returns how many free draws used today.
func (r *ImageCardRepo) UsedToday(ctx context.Context, userID uuid.UUID, day time.Time) (int, error) {
	var n int
	err := r.Pool.QueryRow(ctx, `
		SELECT used FROM image_card_quotas
		WHERE user_id=$1 AND day=$2::date`,
		userID, day.Format("2006-01-02"),
	).Scan(&n)
	if errors.Is(err, pgx.ErrNoRows) {
		return 0, nil
	}
	return n, err
}

// TryConsume increments today's used count when under free limit.
// Returns remaining after consume. ErrQuotaExhausted when free tier is out.
func (r *ImageCardRepo) TryConsume(ctx context.Context, userID uuid.UUID, day time.Time) (remaining int, err error) {
	dayStr := day.Format("2006-01-02")
	var used int
	err = r.Pool.QueryRow(ctx, `
		INSERT INTO image_card_quotas(user_id, day, used)
		VALUES ($1, $2::date, 1)
		ON CONFLICT (user_id, day) DO UPDATE
		  SET used = image_card_quotas.used + 1
		WHERE image_card_quotas.used < $3
		RETURNING used`,
		userID, dayStr, imageCardDailyFree,
	).Scan(&used)
	if errors.Is(err, pgx.ErrNoRows) {
		return 0, ErrQuotaExhausted
	}
	if err != nil {
		return 0, err
	}
	return imageCardDailyFree - used, nil
}

// RemainingToday without consuming.
func (r *ImageCardRepo) RemainingToday(ctx context.Context, userID uuid.UUID, day time.Time, unlimited bool) (int, error) {
	if unlimited {
		return 99, nil
	}
	used, err := r.UsedToday(ctx, userID, day)
	if err != nil {
		return 0, err
	}
	left := imageCardDailyFree - used
	if left < 0 {
		left = 0
	}
	return left, nil
}

// DailyFreeLimit is the free-tier cap.
func DailyFreeLimit() int { return imageCardDailyFree }

// ErrQuotaExhausted means free daily draws are used up.
var ErrQuotaExhausted = errors.New("今日免费次数已用完")