package service

import (
	"context"
	"sync"
	"time"

	"apskel-pos-be/internal/logger"
)

const (
	defaultGameSessionJobInterval      = time.Minute
	defaultGameBudgetPeriodJobInterval = 24 * time.Hour
)

// tickerJob runs a function now and then on every tick until stopped. It keeps no
// state in memory: the work it runs is safe on several instances at once.
type tickerJob struct {
	name     string
	run      func(ctx context.Context)
	stopCh   chan struct{}
	stopOnce sync.Once
}

func (j *tickerJob) start(interval, fallback time.Duration) {
	if interval <= 0 {
		interval = fallback
	}
	go func() {
		j.run(context.Background())
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		for {
			select {
			case <-ticker.C:
				j.run(context.Background())
			case <-j.stopCh:
				return
			}
		}
	}()
	logger.NonContext.Infof("%s started (interval: %s)", j.name, interval)
}

func (j *tickerJob) stop() {
	j.stopOnce.Do(func() { close(j.stopCh) })
}

type gameSessionWork interface {
	ProcessDueSessions(ctx context.Context) (refunded, expired int, err error)
}

// GameSessionJob refunds or expires the EnakGame sessions left STARTED
// (docs/rfc-enakgame.md §7.3). Every session is handled under its customer's wallet
// lock with a conditional update, and the refund carries an idempotency key, so
// several instances and repeated runs refund nothing twice.
type GameSessionJob struct{ job tickerJob }

func NewGameSessionJob(work gameSessionWork) *GameSessionJob {
	j := &GameSessionJob{}
	j.job = tickerJob{name: "Game session job", stopCh: make(chan struct{}), run: func(ctx context.Context) {
		refunded, expired, err := work.ProcessDueSessions(ctx)
		if err != nil {
			logger.NonContext.Error("Game session job failed", err)
		}
		if refunded > 0 || expired > 0 {
			logger.NonContext.Infof("Game session job refunded %d and expired %d sessions", refunded, expired)
		}
	}}
	return j
}

func (j *GameSessionJob) Start(interval time.Duration) {
	j.job.start(interval, defaultGameSessionJobInterval)
}
func (j *GameSessionJob) Stop() { j.job.stop() }

type gameBudgetPeriodWork interface {
	CreateNextPeriods(ctx context.Context) (int, error)
}

// GameBudgetPeriodJob gives each running global EnakGame budget its successor for the
// following month, when there is none yet (§12). The unique index on the period start
// keeps repeated runs and several instances from creating it twice.
type GameBudgetPeriodJob struct{ job tickerJob }

func NewGameBudgetPeriodJob(work gameBudgetPeriodWork) *GameBudgetPeriodJob {
	j := &GameBudgetPeriodJob{}
	j.job = tickerJob{name: "Game budget period job", stopCh: make(chan struct{}), run: func(ctx context.Context) {
		created, err := work.CreateNextPeriods(ctx)
		if err != nil {
			logger.NonContext.Error("Game budget period job failed", err)
		}
		if created > 0 {
			logger.NonContext.Infof("Game budget period job created %d budgets", created)
		}
	}}
	return j
}

func (j *GameBudgetPeriodJob) Start(interval time.Duration) {
	j.job.start(interval, defaultGameBudgetPeriodJobInterval)
}
func (j *GameBudgetPeriodJob) Stop() { j.job.stop() }

const defaultVoucherCodeExpiryJobInterval = time.Hour

type voucherCodeExpiryWork interface {
	ExpireCodes(ctx context.Context, now time.Time) (int64, error)
}

// VoucherCodeExpiryJob moves the voucher codes past their expiry from AVAILABLE to
// EXPIRED (docs/rfc-enakgame.md §12). Redemption already skips them; this keeps the
// counts honest. Rows are taken with SKIP LOCKED, so instances share the work.
type VoucherCodeExpiryJob struct{ job tickerJob }

func NewVoucherCodeExpiryJob(work voucherCodeExpiryWork) *VoucherCodeExpiryJob {
	j := &VoucherCodeExpiryJob{}
	j.job = tickerJob{name: "Voucher code expiry job", stopCh: make(chan struct{}), run: func(ctx context.Context) {
		expired, err := work.ExpireCodes(ctx, time.Now())
		if err != nil {
			logger.NonContext.Error("Voucher code expiry job failed", err)
		}
		if expired > 0 {
			logger.NonContext.Infof("Voucher code expiry job expired %d codes", expired)
		}
	}}
	return j
}

func (j *VoucherCodeExpiryJob) Start(interval time.Duration) {
	j.job.start(interval, defaultVoucherCodeExpiryJobInterval)
}
func (j *VoucherCodeExpiryJob) Stop() { j.job.stop() }

const defaultVoucherRecoveryJobInterval = time.Minute

type voucherRecoveryWork interface {
	RecoverPending(ctx context.Context) (completed, failed int, err error)
}

// VoucherRedemptionRecoveryJob settles the EXTERNAL voucher redemptions their provider
// left without an answer (docs/rfc-enakgame.md §7.5 step 4). Redemptions are claimed
// with SKIP LOCKED and settled with conditional updates, so several instances and
// repeated runs never refund one twice.
type VoucherRedemptionRecoveryJob struct{ job tickerJob }

func NewVoucherRedemptionRecoveryJob(work voucherRecoveryWork) *VoucherRedemptionRecoveryJob {
	j := &VoucherRedemptionRecoveryJob{}
	j.job = tickerJob{name: "Voucher redemption recovery job", stopCh: make(chan struct{}), run: func(ctx context.Context) {
		completed, failed, err := work.RecoverPending(ctx)
		if err != nil {
			logger.NonContext.Error("Voucher redemption recovery job failed", err)
		}
		if completed > 0 || failed > 0 {
			logger.NonContext.Infof("Voucher redemption recovery job completed %d and failed %d redemptions", completed, failed)
		}
	}}
	return j
}

func (j *VoucherRedemptionRecoveryJob) Start(interval time.Duration) {
	j.job.start(interval, defaultVoucherRecoveryJobInterval)
}
func (j *VoucherRedemptionRecoveryJob) Stop() { j.job.stop() }