// Package reward 承载邀请奖励与奖励任务的数据访问 + 发奖 + 防刷。
package reward

import (
	"context"
	"database/sql"
	"errors"
	"strings"
	"time"
)

var ErrClaimExists = errors.New("reward: claim already exists")

type Store struct{ db *sql.DB }

func NewStore(db *sql.DB) *Store { return &Store{db: db} }

// EnsureInviteCode 惰性生成邀请码;已有则返回旧值。gen 生成候选码(冲突时重试到成功)。
func (s *Store) EnsureInviteCode(ctx context.Context, userID int64, gen func() string) (string, error) {
	var existing sql.NullString
	if err := s.db.QueryRowContext(ctx, `SELECT invite_code FROM users WHERE id=?`, userID).Scan(&existing); err != nil {
		return "", err
	}
	if existing.Valid && existing.String != "" {
		return existing.String, nil
	}
	for i := 0; i < 5; i++ {
		code := gen()
		_, err := s.db.ExecContext(ctx, `UPDATE users SET invite_code=? WHERE id=? AND invite_code IS NULL`, code, userID)
		if err != nil {
			if isDup(err) {
				continue
			}
			return "", err
		}
		// 读回(并发下可能是别的并发写入的值)
		var got sql.NullString
		if err := s.db.QueryRowContext(ctx, `SELECT invite_code FROM users WHERE id=?`, userID).Scan(&got); err != nil {
			return "", err
		}
		if got.Valid && got.String != "" {
			return got.String, nil
		}
	}
	return "", errors.New("reward: invite code generation exhausted")
}

func (s *Store) ResolveInviteCode(ctx context.Context, code string) (int64, bool, error) {
	var id int64
	err := s.db.QueryRowContext(ctx, `SELECT id FROM users WHERE invite_code=? AND status='active'`, code).Scan(&id)
	if err == sql.ErrNoRows {
		return 0, false, nil
	}
	return id, err == nil, err
}

func (s *Store) DeviceUsedByOther(ctx context.Context, deviceUUID string, exceptUserID int64) (bool, error) {
	if deviceUUID == "" {
		return false, nil
	}
	var n int
	err := s.db.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM devices WHERE uuid=? AND user_id<>?`, deviceUUID, exceptUserID).Scan(&n)
	return n > 0, err
}

func (s *Store) RegRewardCountThisMonth(ctx context.Context, inviterID int64, since time.Time) (int, error) {
	var n int
	err := s.db.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM referrals WHERE inviter_id=? AND status='reg_rewarded' AND reg_rewarded_at>=?`,
		inviterID, since).Scan(&n)
	return n, err
}

func (s *Store) InsertReferralTx(ctx context.Context, tx *sql.Tx, inviterID, inviteeID int64,
	deviceUUID, status string, regRewardedAt *time.Time, now time.Time) error {
	_, err := tx.ExecContext(ctx,
		`INSERT INTO referrals (inviter_id,invitee_id,device_uuid,status,reg_rewarded_at,created_at)
		 VALUES (?,?,?,?,?,?)`, inviterID, inviteeID, deviceUUID, status, regRewardedAt, now)
	if isDup(err) {
		return ErrClaimExists
	}
	return err
}

func (s *Store) ReferralByInvitee(ctx context.Context, tx *sql.Tx, inviteeID int64) (int64, string, bool, error) {
	var inviter int64
	var status string
	err := tx.QueryRowContext(ctx, `SELECT inviter_id,status FROM referrals WHERE invitee_id=?`, inviteeID).
		Scan(&inviter, &status)
	if err == sql.ErrNoRows {
		return 0, "", false, nil
	}
	return inviter, status, err == nil, err
}

func (s *Store) MarkFirstPaidTx(ctx context.Context, tx *sql.Tx, userID int64, at time.Time) (bool, error) {
	res, err := tx.ExecContext(ctx,
		`UPDATE users SET first_paid_at=? WHERE id=? AND first_paid_at IS NULL`, at, userID)
	if err != nil {
		return false, err
	}
	n, _ := res.RowsAffected()
	return n == 1, nil
}

func (s *Store) MarkPaidRewardedTx(ctx context.Context, tx *sql.Tx, inviteeID int64, at time.Time) error {
	_, err := tx.ExecContext(ctx,
		`UPDATE referrals SET status='paid_rewarded', paid_rewarded_at=? WHERE invitee_id=?`, at, inviteeID)
	return err
}

func (s *Store) InsertClaimTx(ctx context.Context, tx *sql.Tx, userID int64, taskKey, externalRef string,
	days int, now time.Time) error {
	_, err := tx.ExecContext(ctx,
		`INSERT INTO reward_claims (user_id,task_key,external_ref,granted_days,granted_at)
		 VALUES (?,?,?,?,?)`, userID, taskKey, externalRef, days, now)
	if isDup(err) {
		return ErrClaimExists
	}
	return err
}

func (s *Store) TelegramClaimed(ctx context.Context, userID int64) (bool, error) {
	var n int
	err := s.db.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM reward_claims WHERE user_id=? AND task_key='telegram_join'`, userID).Scan(&n)
	return n > 0, err
}

// Summary: invited=已绑定人数;converted=已首充奖励人数;earnedDays=本人从奖励得到的总天数(audit_log 累加)。
func (s *Store) Summary(ctx context.Context, userID int64) (invited, converted, earnedDays int, err error) {
	if err = s.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM referrals WHERE inviter_id=?`, userID).Scan(&invited); err != nil {
		return
	}
	if err = s.db.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM referrals WHERE inviter_id=? AND status='paid_rewarded'`, userID).Scan(&converted); err != nil {
		return
	}
	// earnedDays: audit_log 里 actor=user:<id> 且 action∈奖励动作,meta.days 累加(简化:reward_claims + referrals 估算)
	var tg, reg, paid int
	s.db.QueryRowContext(ctx, `SELECT COALESCE(SUM(granted_days),0) FROM reward_claims WHERE user_id=?`, userID).Scan(&tg)
	s.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM referrals WHERE inviter_id=? AND status IN ('reg_rewarded','paid_rewarded')`, userID).Scan(&reg)
	s.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM referrals WHERE inviter_id=? AND status='paid_rewarded'`, userID).Scan(&paid)
	// 邀请人:每 reg_rewarded +3、每 paid_rewarded 再 +7;被邀请人自身得的天数不计入其「邀请战绩」。
	earnedDays = tg + reg*3 + paid*7
	return
}

func isDup(err error) bool {
	if err == nil {
		return false
	}
	m := strings.ToLower(err.Error())
	return strings.Contains(m, "unique") || strings.Contains(m, "duplicate")
}