package outbox

import (
	"context"
	stderrors "errors"
	"math"
	"sync"
	"time"

	"github.com/bytedance/sonic"
	"github.com/hibiken/asynq"
	"go.uber.org/zap"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"

	"github.com/break/junhong_cmp_fiber/internal/model"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
	"github.com/break/junhong_cmp_fiber/pkg/queue"
)

// DeliveryEnvelope 是 Relay 原样传播到 Asynq 的公共结构化信封。
type DeliveryEnvelope struct {
	EventID        string                 `json:"event_id"`
	EventType      string                 `json:"event_type"`
	PayloadVersion int                    `json:"payload_version"`
	AggregateType  string                 `json:"aggregate_type"`
	AggregateID    string                 `json:"aggregate_id"`
	ResourceType   string                 `json:"resource_type"`
	ResourceID     string                 `json:"resource_id"`
	BusinessKey    string                 `json:"business_key,omitempty"`
	RequestID      string                 `json:"request_id,omitempty"`
	CorrelationID  string                 `json:"correlation_id,omitempty"`
	Payload        sonic.NoCopyRawMessage `json:"payload"`
}

// Publisher 是 Relay 的队列边界。
type Publisher interface {
	Publish(ctx context.Context, envelope DeliveryEnvelope) error
}

// PermanentError 表示重试无法修复的投递错误。
type PermanentError struct {
	err error
}

// Error 返回安全的错误文本，仅供内部日志和错误链判断使用。
func (e *PermanentError) Error() string {
	return e.err.Error()
}

// Unwrap 返回原始错误。
func (e *PermanentError) Unwrap() error {
	return e.err
}

// Permanent 将不可恢复错误标记为永久失败，Relay 会直接保留最终失败事实。
func Permanent(err error) error {
	if err == nil {
		return nil
	}
	return &PermanentError{err: err}
}

// QueuePublisher 使用项目统一队列客户端发布结构化信封。
type QueuePublisher struct {
	client *queue.Client
}

// NewQueuePublisher 创建项目统一队列客户端 Adapter。
func NewQueuePublisher(client *queue.Client) *QueuePublisher {
	return &QueuePublisher{client: client}
}

// Publish 将公共信封作为 struct 入队，禁止调用方预序列化。
func (p *QueuePublisher) Publish(ctx context.Context, envelope DeliveryEnvelope) error {
	return p.client.EnqueueTask(ctx, constants.TaskTypeOutboxDeliver, envelope)
}

// RelayOptions 控制单个 Relay 实例的领取与重试行为。
type RelayOptions struct {
	Owner         string
	BatchSize     int
	LeaseDuration time.Duration
	Now           func() time.Time
}

// Relay 完成公共 Outbox 的租约领取和至少一次队列投递。
type Relay struct {
	db        *gorm.DB
	publisher Publisher
	logger    *zap.Logger
	options   RelayOptions
}

// NewRelay 创建公共 Outbox Relay。
func NewRelay(db *gorm.DB, publisher Publisher, logger *zap.Logger, options RelayOptions) (*Relay, error) {
	if db == nil || publisher == nil || options.Owner == "" {
		return nil, stderrors.New("Outbox Relay 依赖和租约所有者不能为空")
	}
	if options.BatchSize <= 0 {
		options.BatchSize = constants.OutboxDefaultBatchSize
	}
	if options.LeaseDuration <= 0 {
		options.LeaseDuration = constants.OutboxDefaultLeaseDuration
	}
	if options.Now == nil {
		options.Now = time.Now
	}
	if logger == nil {
		logger = zap.NewNop()
	}
	return &Relay{db: db, publisher: publisher, logger: logger, options: options}, nil
}

// ProcessBatch 领取并投递一批到期事件。
func (r *Relay) ProcessBatch(ctx context.Context) (int, error) {
	events, err := r.ClaimBatch(ctx)
	if err != nil {
		return 0, err
	}
	processed := 0
	for _, event := range events {
		if err := r.publisher.Publish(ctx, deliveryEnvelope(event)); err != nil {
			var permanentError *PermanentError
			permanent := stderrors.As(err, &permanentError)
			code := "OUTBOX_ENQUEUE_FAILED"
			summary := "队列暂时不可用"
			if permanent {
				code = "OUTBOX_PERMANENT_FAILURE"
				summary = "事件无法投递，已停止自动重试"
			}
			if failErr := r.markFailed(ctx, event, code, summary, permanent); failErr != nil {
				return processed, failErr
			}
			r.logger.Warn("Outbox 事件投递失败",
				zap.String("event_id", event.EventID), zap.String("correlation_id", event.CorrelationID),
				zap.String("error_code", code), zap.Bool("permanent", permanent))
			continue
		}
		if err := r.MarkDelivered(ctx, event.ID); err != nil {
			// 入队成功但标记失败时保留租约，过期后会使用同一 event_id 再次投递。
			return processed, err
		}
		processed++
	}
	return processed, nil
}

// ClaimBatch 通过行锁跳过竞争行，并领取待投递或租约过期事件。
func (r *Relay) ClaimBatch(ctx context.Context) ([]model.OutboxEvent, error) {
	now := r.options.Now().UTC()
	expiresAt := now.Add(r.options.LeaseDuration)
	claimed := make([]model.OutboxEvent, 0, r.options.BatchSize)
	err := r.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		var candidates []model.OutboxEvent
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE", Options: "SKIP LOCKED"}).
			Where("(status = ? AND next_attempt_at <= ?) OR (status = ? AND lease_expires_at <= ?)",
				constants.OutboxStatusPending, now, constants.OutboxStatusDelivering, now).
			Order("created_at ASC, id ASC").Limit(r.options.BatchSize).Find(&candidates).Error; err != nil {
			return err
		}
		for index := range candidates {
			result := tx.Model(&model.OutboxEvent{}).
				Where("id = ? AND ((status = ? AND next_attempt_at <= ?) OR (status = ? AND lease_expires_at <= ?))",
					candidates[index].ID, constants.OutboxStatusPending, now, constants.OutboxStatusDelivering, now).
				Updates(map[string]any{
					"status": constants.OutboxStatusDelivering, "lease_owner": r.options.Owner,
					"lease_expires_at": expiresAt, "updated_at": now,
				})
			if result.Error != nil {
				return result.Error
			}
			if result.RowsAffected == 1 {
				candidates[index].Status = constants.OutboxStatusDelivering
				candidates[index].LeaseOwner = &r.options.Owner
				candidates[index].LeaseExpiresAt = &expiresAt
				claimed = append(claimed, candidates[index])
			}
		}
		return nil
	})
	return claimed, err
}

// RenewLease 仅允许当前租约所有者续租投递中的事件。
func (r *Relay) RenewLease(ctx context.Context, eventID uint) (bool, error) {
	now := r.options.Now().UTC()
	result := r.db.WithContext(ctx).Model(&model.OutboxEvent{}).
		Where("id = ? AND status = ? AND lease_owner = ? AND lease_expires_at > ?",
			eventID, constants.OutboxStatusDelivering, r.options.Owner, now).
		Updates(map[string]any{"lease_expires_at": now.Add(r.options.LeaseDuration), "updated_at": now})
	return result.RowsAffected == 1, result.Error
}

// MarkDelivered 仅允许当前租约所有者把事件标记为已投递。
func (r *Relay) MarkDelivered(ctx context.Context, eventID uint) error {
	now := r.options.Now().UTC()
	result := r.db.WithContext(ctx).Model(&model.OutboxEvent{}).
		Where("id = ? AND status = ? AND lease_owner = ?", eventID, constants.OutboxStatusDelivering, r.options.Owner).
		Updates(map[string]any{
			"status": constants.OutboxStatusDelivered, "delivered_at": now,
			"lease_owner": nil, "lease_expires_at": nil, "last_error_code": "",
			"last_error_summary": "", "updated_at": now,
		})
	if result.Error != nil {
		return result.Error
	}
	if result.RowsAffected != 1 {
		return stderrors.New("Outbox 投递完成条件不满足")
	}
	return nil
}

// MarkFailed 记录安全错误并退避；达到上限后保留最终失败事实。
func (r *Relay) MarkFailed(ctx context.Context, event model.OutboxEvent, code, summary string) error {
	return r.markFailed(ctx, event, code, summary, false)
}

func (r *Relay) markFailed(ctx context.Context, event model.OutboxEvent, code, summary string, permanent bool) error {
	now := r.options.Now().UTC()
	retryCount := event.RetryCount + 1
	status := constants.OutboxStatusPending
	nextAttemptAt := now.Add(backoff(retryCount))
	if permanent || retryCount >= event.MaxRetries {
		status = constants.OutboxStatusFailed
		nextAttemptAt = now
		r.logger.Error("Outbox 事件停止自动重试",
			zap.String("event_id", event.EventID), zap.String("correlation_id", event.CorrelationID),
			zap.String("error_code", code), zap.Bool("permanent", permanent))
	}
	result := r.db.WithContext(ctx).Model(&model.OutboxEvent{}).
		Where("id = ? AND status = ? AND lease_owner = ?", event.ID, constants.OutboxStatusDelivering, r.options.Owner).
		Updates(map[string]any{
			"status": status, "retry_count": retryCount, "next_attempt_at": nextAttemptAt,
			"lease_owner": nil, "lease_expires_at": nil, "last_error_code": code,
			"last_error_summary": summary, "updated_at": now,
		})
	if result.Error != nil {
		return result.Error
	}
	if result.RowsAffected != 1 {
		return stderrors.New("Outbox 失败更新条件不满足")
	}
	return nil
}

func deliveryEnvelope(event model.OutboxEvent) DeliveryEnvelope {
	return DeliveryEnvelope{
		EventID: event.EventID, EventType: event.EventType, PayloadVersion: event.PayloadVersion,
		AggregateType: event.AggregateType, AggregateID: event.AggregateID,
		ResourceType: event.ResourceType, ResourceID: event.ResourceID, BusinessKey: event.BusinessKey,
		RequestID: event.RequestID, CorrelationID: event.CorrelationID,
		Payload: sonic.NoCopyRawMessage(event.Payload),
	}
}

func backoff(retryCount int) time.Duration {
	delay := float64(constants.OutboxBaseRetryDelay) * math.Pow(2, float64(retryCount-1))
	if delay > float64(constants.OutboxMaxRetryDelay) {
		return constants.OutboxMaxRetryDelay
	}
	return time.Duration(delay)
}

// EventConsumer 是业务消费者公开实现的事件处理边界。
type EventConsumer interface {
	Consume(ctx context.Context, envelope DeliveryEnvelope) error
}

// ConsumerRegistry 按稳定事件类型分发到业务消费者。
type ConsumerRegistry struct {
	mu        sync.RWMutex
	consumers map[string]EventConsumer
}

// NewConsumerRegistry 创建空消费者注册表。
func NewConsumerRegistry() *ConsumerRegistry {
	return &ConsumerRegistry{consumers: map[string]EventConsumer{}}
}

// Register 注册一个由业务 PRD 拥有的事件消费者。
func (r *ConsumerRegistry) Register(eventType string, consumer EventConsumer) error {
	if eventType == "" || consumer == nil {
		return stderrors.New("Outbox 消费者注册信息不完整")
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	if _, exists := r.consumers[eventType]; exists {
		return stderrors.New("Outbox 事件类型重复注册")
	}
	r.consumers[eventType] = consumer
	return nil
}

// Consume 将公共信封交给对应业务消费者；公共层不实现业务副作用。
func (r *ConsumerRegistry) Consume(ctx context.Context, envelope DeliveryEnvelope) error {
	r.mu.RLock()
	consumer := r.consumers[envelope.EventType]
	r.mu.RUnlock()
	if consumer == nil {
		return stderrors.New("Outbox 事件消费者尚未注册")
	}
	return consumer.Consume(ctx, envelope)
}

// Handler 是公共 Outbox Asynq 任务 Handler。
type Handler struct {
	consumer EventConsumer
}

// NewHandler 创建公共 Outbox Asynq Handler。
func NewHandler(consumer EventConsumer) *Handler {
	return &Handler{consumer: consumer}
}

// Handle 解析结构化信封并调用公开消费者边界。
func (h *Handler) Handle(ctx context.Context, task *asynq.Task) error {
	var envelope DeliveryEnvelope
	if err := sonic.Unmarshal(task.Payload(), &envelope); err != nil {
		return err
	}
	if envelope.EventID == "" || envelope.EventType == "" || envelope.PayloadVersion <= 0 {
		return stderrors.New("Outbox 事件信封不完整")
	}
	return h.consumer.Consume(ctx, envelope)
}