package workbench

import (
	"bytes"
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"time"
	"unicode/utf8"

	"aigateway.local/core/internal/platform/cryptox"
	"aigateway.local/core/internal/provider"
	"github.com/jackc/pgx/v5"
	"github.com/redis/go-redis/v9"
)

type NotificationInput struct {
	Name, WebhookURL string
	SigningSecret    *string
	EventPatterns    []string
	Enabled          bool
}

type NotificationService struct {
	assets       *Service
	cipher       cryptox.Cipher
	allowPrivate bool
	client       *http.Client
}

func NewNotificationService(assets *Service, cipher cryptox.Cipher, allowPrivate bool) *NotificationService {
	// One shared client for all deliveries: http.Client is safe for concurrent
	// use, and reusing the transport keeps TLS sessions and connections
	// warm instead of re-handshaking for every webhook.
	client := &http.Client{
		Timeout: 15 * time.Second,
		Transport: &http.Transport{
			DialContext:           safeToolDial(allowPrivate),
			TLSHandshakeTimeout:   5 * time.Second,
			ResponseHeaderTimeout: 10 * time.Second,
			MaxIdleConns:          64,
			MaxIdleConnsPerHost:   16,
			IdleConnTimeout:       90 * time.Second,
		},
		CheckRedirect: func(*http.Request, []*http.Request) error { return errors.New("Webhook 不允许重定向") },
	}
	return &NotificationService{assets: assets, cipher: cipher, allowPrivate: allowPrivate, client: client}
}

const channelSelect = `SELECT id::text,name,webhook_url,event_patterns,enabled,octet_length(encrypted_signing_secret)>0,revision,created_at,updated_at,encrypted_signing_secret,signing_secret_kek_version FROM gateway.notification_channels`

func scanChannel(row pgx.Row) (NotificationChannel, error) {
	var c NotificationChannel
	err := row.Scan(&c.ID, &c.Name, &c.WebhookURL, &c.EventPatterns, &c.Enabled, &c.HasSigningSecret, &c.Revision, &c.CreatedAt, &c.UpdatedAt, &c.EncryptedSigningSecret, &c.SigningSecretKEKVersion)
	return c, mapNotFound(err)
}
func (s *NotificationService) ListChannels(ctx context.Context) ([]NotificationChannel, error) {
	rows, err := s.assets.pool.Query(ctx, channelSelect+` ORDER BY updated_at DESC`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	items := []NotificationChannel{}
	for rows.Next() {
		c, err := scanChannel(rows)
		if err != nil {
			return nil, err
		}
		items = append(items, c)
	}
	return items, rows.Err()
}
func (s *NotificationService) GetChannel(ctx context.Context, id string) (NotificationChannel, error) {
	return scanChannel(s.assets.pool.QueryRow(ctx, channelSelect+` WHERE id=$1`, id))
}

func (s *NotificationService) SaveChannel(ctx context.Context, id string, input NotificationInput, actorID string, create bool) (NotificationChannel, error) {
	input.Name = strings.TrimSpace(input.Name)
	input.WebhookURL = strings.TrimSpace(input.WebhookURL)
	if input.Name == "" || len(input.Name) > 128 {
		return NotificationChannel{}, errors.New("通知通道名称格式无效")
	}
	validated, err := provider.ValidateBaseURL(ctx, input.WebhookURL, s.allowPrivate)
	if err != nil {
		return NotificationChannel{}, fmt.Errorf("Webhook 地址校验失败: %w", err)
	}
	input.WebhookURL = validated
	input.EventPatterns, err = normalizeStrings(input.EventPatterns, 100)
	if err != nil {
		return NotificationChannel{}, err
	}
	if len(input.EventPatterns) == 0 {
		return NotificationChannel{}, errors.New("至少配置一个事件模式")
	}
	for _, pattern := range input.EventPatterns {
		if strings.Count(pattern, "*") > 1 || (strings.Contains(pattern, "*") && !strings.HasSuffix(pattern, "*")) {
			return NotificationChannel{}, errors.New("事件模式仅允许末尾 * 通配")
		}
	}
	tx, err := s.assets.pool.Begin(ctx)
	if err != nil {
		return NotificationChannel{}, err
	}
	defer rollback(ctx, tx)
	var encrypted []byte
	var version int
	if input.SigningSecret != nil && *input.SigningSecret != "" {
		if len(*input.SigningSecret) > 4096 {
			return NotificationChannel{}, errors.New("签名密钥过长")
		}
		encrypted, version, err = s.cipher.Encrypt([]byte(*input.SigningSecret))
		if err != nil {
			return NotificationChannel{}, err
		}
	}
	if create {
		id, err = newUUID()
		if err != nil {
			return NotificationChannel{}, err
		}
		_, err = tx.Exec(ctx, `INSERT INTO gateway.notification_channels(id,name,webhook_url,encrypted_signing_secret,signing_secret_kek_version,event_patterns,enabled,created_by) VALUES($1,$2,$3,$4,$5,$6,$7,$8)`, id, input.Name, input.WebhookURL, encrypted, version, input.EventPatterns, input.Enabled, actorID)
	} else if input.SigningSecret == nil {
		tag, updateErr := tx.Exec(ctx, `UPDATE gateway.notification_channels SET name=$2,webhook_url=$3,event_patterns=$4,enabled=$5,revision=revision+1,updated_at=clock_timestamp() WHERE id=$1`, id, input.Name, input.WebhookURL, input.EventPatterns, input.Enabled)
		err = updateErr
		if err == nil && tag.RowsAffected() == 0 {
			return NotificationChannel{}, ErrNotFound
		}
	} else {
		tag, updateErr := tx.Exec(ctx, `UPDATE gateway.notification_channels SET name=$2,webhook_url=$3,encrypted_signing_secret=$4,signing_secret_kek_version=$5,event_patterns=$6,enabled=$7,revision=revision+1,updated_at=clock_timestamp() WHERE id=$1`, id, input.Name, input.WebhookURL, encrypted, version, input.EventPatterns, input.Enabled)
		err = updateErr
		if err == nil && tag.RowsAffected() == 0 {
			return NotificationChannel{}, ErrNotFound
		}
	}
	if err != nil {
		return NotificationChannel{}, err
	}
	event := "notification_channel.updated"
	if create {
		event = "notification_channel.created"
	}
	if err = emit(ctx, tx, event, "notification_channel", id, actorID, nil); err != nil {
		return NotificationChannel{}, err
	}
	if err = tx.Commit(ctx); err != nil {
		return NotificationChannel{}, err
	}
	return s.GetChannel(ctx, id)
}

func (s *NotificationService) DeleteChannel(ctx context.Context, id, actorID string) error {
	tx, err := s.assets.pool.Begin(ctx)
	if err != nil {
		return err
	}
	defer rollback(ctx, tx)
	tag, err := tx.Exec(ctx, `DELETE FROM gateway.notification_channels WHERE id=$1`, id)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	if err = emit(ctx, tx, "notification_channel.deleted", "notification_channel", id, actorID, nil); err != nil {
		return err
	}
	return tx.Commit(ctx)
}

const deliverySelect = `SELECT d.id::text,d.channel_id::text,c.name,d.event_id::text,d.event_type,d.status,d.last_error,d.payload,d.attempts,d.response_status,d.delivered_at,d.created_at,d.updated_at FROM gateway.notification_deliveries d JOIN gateway.notification_channels c ON c.id=d.channel_id`

func (s *NotificationService) ListDeliveries(ctx context.Context, limit int) ([]NotificationDelivery, error) {
	if limit < 1 {
		limit = 100
	}
	if limit > 500 {
		limit = 500
	}
	rows, err := s.assets.pool.Query(ctx, deliverySelect+` ORDER BY d.created_at DESC LIMIT $1`, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	items := []NotificationDelivery{}
	for rows.Next() {
		var d NotificationDelivery
		if err = rows.Scan(&d.ID, &d.ChannelID, &d.ChannelName, &d.EventID, &d.EventType, &d.Status, &d.LastError, &d.Payload, &d.Attempts, &d.ResponseStatus, &d.DeliveredAt, &d.CreatedAt, &d.UpdatedAt); err != nil {
			return nil, err
		}
		items = append(items, d)
	}
	return items, rows.Err()
}

func matchesEvent(patterns []string, eventType string) bool {
	for _, pattern := range patterns {
		if pattern == "*" || pattern == eventType {
			return true
		}
		if strings.HasSuffix(pattern, "*") && strings.HasPrefix(eventType, strings.TrimSuffix(pattern, "*")) {
			return true
		}
	}
	return false
}

func (s *NotificationService) ensureDelivery(ctx context.Context, channel NotificationChannel, eventID, eventType string, payload json.RawMessage) (NotificationDelivery, error) {
	id, err := newUUID()
	if err != nil {
		return NotificationDelivery{}, err
	}
	var d NotificationDelivery
	err = s.assets.pool.QueryRow(ctx, `INSERT INTO gateway.notification_deliveries(id,channel_id,event_id,event_type,payload,status) VALUES($1,$2,$3,$4,$5,'pending') ON CONFLICT(channel_id,event_id) DO UPDATE SET updated_at=gateway.notification_deliveries.updated_at RETURNING id::text,channel_id::text,$6,event_id::text,event_type,status,last_error,payload,attempts,response_status,delivered_at,created_at,updated_at`, id, channel.ID, eventID, eventType, payload, channel.Name).Scan(&d.ID, &d.ChannelID, &d.ChannelName, &d.EventID, &d.EventType, &d.Status, &d.LastError, &d.Payload, &d.Attempts, &d.ResponseStatus, &d.DeliveredAt, &d.CreatedAt, &d.UpdatedAt)
	return d, err
}

func (s *NotificationService) deliver(ctx context.Context, channel NotificationChannel, delivery NotificationDelivery) error {
	body, _ := json.Marshal(map[string]any{"event_id": delivery.EventID, "event_type": delivery.EventType, "occurred_at": delivery.CreatedAt.UTC().Format(time.RFC3339Nano), "payload": json.RawMessage(delivery.Payload)})
	request, err := http.NewRequestWithContext(ctx, http.MethodPost, channel.WebhookURL, bytes.NewReader(body))
	if err != nil {
		return err
	}
	request.Header.Set("Content-Type", "application/json")
	request.Header.Set("X-Gateway-Event-ID", delivery.EventID)
	if len(channel.EncryptedSigningSecret) > 0 {
		secret, decryptErr := s.cipher.Decrypt(channel.EncryptedSigningSecret, channel.SigningSecretKEKVersion)
		if decryptErr != nil {
			return decryptErr
		}
		mac := hmac.New(sha256.New, secret)
		_, _ = mac.Write(body)
		request.Header.Set("X-Gateway-Signature", "sha256="+hex.EncodeToString(mac.Sum(nil)))
	}
	response, requestErr := s.client.Do(request)
	status := 0
	if response != nil {
		status = response.StatusCode
		_, _ = io.Copy(io.Discard, io.LimitReader(response.Body, 64<<10))
		response.Body.Close()
	}
	success := requestErr == nil && status >= 200 && status < 300
	message := ""
	if requestErr != nil {
		message = requestErr.Error()
	} else if !success {
		message = fmt.Sprintf("Webhook 返回 HTTP %d", status)
	}
	if len(message) > 1000 {
		// 按字节截断可能切半多字节 rune;无效 UTF-8 会被 PostgreSQL 拒绝,
		// 使投递记录无法更新,事件永远重试。
		cut := message[:1000]
		for len(cut) > 0 && !utf8.RuneStart(cut[len(cut)-1]) {
			cut = cut[:len(cut)-1]
		}
		message = cut
	}
	_, dbErr := s.assets.pool.Exec(context.WithoutCancel(ctx), `UPDATE gateway.notification_deliveries SET status=$2,attempts=attempts+1,response_status=nullif($3,0),last_error=$4,delivered_at=CASE WHEN $2='delivered' THEN clock_timestamp() ELSE delivered_at END,updated_at=clock_timestamp() WHERE id=$1`, delivery.ID, map[bool]string{true: "delivered", false: "failed"}[success], status, message)
	if dbErr != nil {
		return dbErr
	}
	if !success {
		return errors.New(message)
	}
	return nil
}

func (s *NotificationService) RetryDelivery(ctx context.Context, id string) error {
	var d NotificationDelivery
	err := s.assets.pool.QueryRow(ctx, deliverySelect+` WHERE d.id=$1`, id).Scan(&d.ID, &d.ChannelID, &d.ChannelName, &d.EventID, &d.EventType, &d.Status, &d.LastError, &d.Payload, &d.Attempts, &d.ResponseStatus, &d.DeliveredAt, &d.CreatedAt, &d.UpdatedAt)
	if err != nil {
		return mapNotFound(err)
	}
	channel, err := s.GetChannel(ctx, d.ChannelID)
	if err != nil {
		return err
	}
	return s.deliver(ctx, channel, d)
}

type NotificationDispatcher struct {
	service                 *NotificationService
	inbox                   *InboxService
	redis                   *redis.Client
	stream, group, consumer string
	logger                  *slog.Logger
}

func NewNotificationDispatcher(service *NotificationService, client *redis.Client, stream, consumer string, logger *slog.Logger) *NotificationDispatcher {
	return &NotificationDispatcher{service: service, redis: client, stream: stream, group: "gateway-notifications-v1", consumer: consumer, logger: logger}
}

// SetInbox wires the in-app inbox materializer (M8 P4). 为 nil 时站内消息不落库,
// Webhook 投递不受影响。handle 内幂等:inbox 以 (source_event_id, 收件人) 去重。
func (d *NotificationDispatcher) SetInbox(inbox *InboxService) { d.inbox = inbox }
func (d *NotificationDispatcher) Run(ctx context.Context) error {
	if err := d.redis.XGroupCreateMkStream(ctx, d.stream, d.group, "$").Err(); err != nil && !strings.Contains(err.Error(), "BUSYGROUP") {
		return err
	}
	delay := time.Duration(0)
	for {
		// Compensate for events claimed by a previous iteration (or a crashed
		// worker) that were never acknowledged. XReadGroup ">" never re-reads
		// the pending list, so without this pass those events would be silently
		// dropped for good.
		if err := d.reclaim(ctx); err != nil {
			if ctx.Err() != nil {
				return nil
			}
			if d.logger != nil {
				d.logger.Error("notification pending reclaim failed; will retry", "error", err)
			}
		}
		streams, err := d.redis.XReadGroup(ctx, &redis.XReadGroupArgs{Group: d.group, Consumer: d.consumer, Streams: []string{d.stream, ">"}, Count: 20, Block: 5 * time.Second}).Result()
		if errors.Is(err, redis.Nil) {
			delay = 0
			continue
		}
		if err != nil {
			if ctx.Err() != nil {
				return nil
			}
			if d.logger != nil {
				d.logger.Error("notification stream read failed; backing off", "error", err)
			}
			// Reconnect with backoff instead of killing the worker: a transient
			// Redis blip must not take the notification worker down and let the
			// stream trim every queued event.
			if !d.wait(ctx, &delay) {
				return nil
			}
			continue
		}
		delay = 0
		for _, stream := range streams {
			for _, message := range stream.Messages {
				if err = d.handle(ctx, message); err != nil {
					// Do not acknowledge: the event stays in the pending list and
					// is retried by the reclaim pass above.
					if d.logger != nil {
						d.logger.Error("notification event failed; will retry", "stream_id", message.ID, "error", err)
					}
					continue
				}
				if err = d.redis.XAck(ctx, d.stream, d.group, message.ID).Err(); err != nil {
					if ctx.Err() != nil {
						return nil
					}
					// An ack failure must not drop a successfully handled event;
					// it is reclaimed and re-acked on the next pass (handle is
					// idempotent via the delivery table).
					if d.logger != nil {
						d.logger.Error("notification ack failed; will retry via reclaim", "stream_id", message.ID, "error", err)
					}
					continue
				}
			}
		}
	}
}

// reclaim re-processes pending stream entries that have been idle longer than
// the threshold. handle is idempotent (deliveries are keyed by channel+event),
// so re-running it only creates the delivery rows that were never created or
// updates attempts on ones already recorded.
func (d *NotificationDispatcher) reclaim(ctx context.Context) error {
	for {
		messages, cursor, err := d.redis.XAutoClaim(ctx, &redis.XAutoClaimArgs{
			Stream:   d.stream,
			Group:    d.group,
			Consumer: d.consumer,
			MinIdle:  30 * time.Second,
			Start:    "0",
			Count:    20,
		}).Result()
		if err != nil {
			return err
		}
		for _, message := range messages {
			if err = d.handle(ctx, message); err != nil {
				if d.logger != nil {
					d.logger.Warn("notification pending retry failed", "stream_id", message.ID, "error", err)
				}
				continue
			}
			if err = d.redis.XAck(ctx, d.stream, d.group, message.ID).Err(); err != nil {
				return err
			}
		}
		if cursor == "0-0" {
			break
		}
	}
	return nil
}

// wait sleeps with exponential backoff, capping at 30s. It returns false when
// the context is cancelled.
func (d *NotificationDispatcher) wait(ctx context.Context, delay *time.Duration) bool {
	const max = 30 * time.Second
	if *delay == 0 {
		*delay = 200 * time.Millisecond
	} else {
		*delay *= 2
		if *delay > max {
			*delay = max
		}
	}
	timer := time.NewTimer(*delay)
	defer timer.Stop()
	select {
	case <-ctx.Done():
		return false
	case <-timer.C:
		return true
	}
}
func (d *NotificationDispatcher) handle(ctx context.Context, message redis.XMessage) error {
	eventID := fmt.Sprint(message.Values["event_id"])
	eventType := fmt.Sprint(message.Values["event_type"])
	payload := json.RawMessage(fmt.Sprint(message.Values["payload"]))
	// M8 P4:物化站内消息。失败与 webhook 同语义——事件留在 pending,由 reclaim 重试;
	// inbox 幂等(ON CONFLICT)保证重放不产生重复消息。
	if d.inbox != nil {
		if err := d.inbox.Materialize(ctx, eventID, eventType, payload); err != nil {
			return err
		}
	}
	channels, err := d.service.ListChannels(ctx)
	if err != nil {
		return err
	}
	selectedChannelID := payloadValue(payload, "notification_channel_id")
	if selectedChannelID == "null" {
		selectedChannelID = ""
	}
	for _, channel := range channels {
		if selectedChannelID != "" && channel.ID != selectedChannelID {
			continue
		}
		if !channel.Enabled || !matchesEvent(channel.EventPatterns, eventType) {
			continue
		}
		delivery, deliveryErr := d.service.ensureDelivery(ctx, channel, eventID, eventType, payload)
		if deliveryErr != nil {
			return deliveryErr
		}
		if delivery.Status == "delivered" {
			continue
		}
		if deliveryErr = d.service.deliver(ctx, channel, delivery); deliveryErr != nil {
			// 投递失败必须让事件留在 pending 列表由 reclaim 重试;但重试预算
			// 耗尽后放弃自动重试(投递记录保留 failed 状态,管理端可人工重试),
			// 否则永久失败的 Webhook 会让事件无限期卡在 pending,阻塞该事件
			// 的其它通道投递与站内消息。
			if delivery.Attempts >= webhookMaxAttempts {
				if d.logger != nil {
					d.logger.Error("webhook delivery exhausted retries; manual retry available in admin",
						"channel", channel.Name, "event_id", eventID, "attempts", delivery.Attempts, "error", deliveryErr)
				}
				continue
			}
			return deliveryErr
		}
	}
	return nil
}

// webhookMaxAttempts 是单条投递记录的自动重试上限;deliver 每次失败 attempts+1。
const webhookMaxAttempts = 10