package telegram

import (
	"context"
	"errors"
	"fmt"
	"html"
	"log/slog"
	"os"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/mymmrac/telego"
	"github.com/mymmrac/telego/telegoapi"
	tu "github.com/mymmrac/telego/telegoutil"

	"github.com/nextlevelbuilder/goclaw/internal/bus"
	"github.com/nextlevelbuilder/goclaw/internal/channels/typing"
)

// Error patterns for graceful handling (matching TS error constants in send.ts).
var (
	parseErrRe           = regexp.MustCompile(`(?i)can't parse entities|parse entities|find end of the entity`)
	messageNotModifiedRe = regexp.MustCompile(`(?i)message is not modified`)
	noTextToEditRe       = regexp.MustCompile(`(?i)no text in the message to edit`)
	threadNotFoundRe     = regexp.MustCompile(`(?i)message thread not found`)
	messageTooLongRe     = regexp.MustCompile(`(?i)message is too long|entities too long`)
	htmlTagRe            = regexp.MustCompile(`<[^>]*>`)
)

// extractMigrateChatID checks if a Telegram API error contains a group→supergroup
// migration indicator and returns the new chat ID, or 0 if not a migration error.
func extractMigrateChatID(err error) int64 {
	var apiErr *telegoapi.Error
	if errors.As(err, &apiErr) && apiErr.Parameters != nil && apiErr.Parameters.MigrateToChatID != 0 {
		return apiErr.Parameters.MigrateToChatID
	}
	return 0
}

const (
	sendMaxRetries     = 3
	sendRetryDelay     = 2 * time.Second
	maxSplitDepth      = 5               // max recursion depth for "message too long" splitting
	photoSizeThreshold = 5 * 1024 * 1024 // 5 MB — images larger than this are sent as documents to avoid Telegram compression
)

// stripHTML removes HTML tags and unescapes HTML entities for plain-text fallback.
func stripHTML(s string) string {
	return html.UnescapeString(htmlTagRe.ReplaceAllString(s, ""))
}

// isRetryableNetworkErr checks if a Telegram API error is a transient error
// worth retrying. Covers 429 rate limits, 5xx server errors, and transport failures.
func isRetryableNetworkErr(err error) bool {
	if err == nil {
		return false
	}
	// Check for Telegram API errors via typed error.
	var apiErr *telegoapi.Error
	if errors.As(err, &apiErr) {
		// 429 = rate limited (transient), 5xx = server error (transient)
		if apiErr.ErrorCode == 429 || apiErr.ErrorCode >= 500 {
			return true
		}
	}
	// Transport-level errors (timeout, reset, DNS, etc.)
	s := err.Error()
	return strings.Contains(s, "timeout") ||
		strings.Contains(s, "connection reset") ||
		strings.Contains(s, "broken pipe") ||
		strings.Contains(s, "EOF") ||
		strings.Contains(s, "lookup") // DNS resolution failure
}

// isPostConnectNetworkErr checks if the error likely occurred AFTER reaching the server
// (timeout, connection reset, EOF) vs before (DNS lookup failure, connection refused).
// Used to decide if a request may have landed despite the error.
func isPostConnectNetworkErr(err error) bool {
	if err == nil {
		return false
	}
	// Telegram 5xx means the server received the request.
	var apiErr *telegoapi.Error
	if errors.As(err, &apiErr) && apiErr.ErrorCode >= 500 {
		return true
	}
	s := err.Error()
	return (strings.Contains(s, "timeout") ||
		strings.Contains(s, "connection reset") ||
		strings.Contains(s, "broken pipe") ||
		strings.Contains(s, "EOF")) && !strings.Contains(s, "lookup")
}

// mediaSendMethods lists sendX calls that upload a file body and therefore
// need the longer sendMediaOverallTimeout budget. Keyed by the `name` argument
// passed to retrySend so no call site has to change when we bump the budget.
var mediaSendMethods = map[string]struct{}{
	"sendPhoto":      {},
	"sendVideo":      {},
	"sendAudio":      {},
	"sendVoice":      {},
	"sendDocument":   {},
	"sendMediaGroup": {},
}

// retrySend wraps a Telegram send call with retry logic for transient network errors.
// Parse errors are NOT retried (handled by caller's HTML fallback).
// resetFn is called before each retry (e.g. to seek file handles back to start). Can be nil.
func (c *Channel) retrySend(ctx context.Context, name string, resetFn func(), fn func(context.Context) error) error {
	overall := sendOverallTimeout
	if _, isMedia := mediaSendMethods[name]; isMedia {
		overall = sendMediaOverallTimeout
	}
	ctx, cancel := context.WithTimeout(ctx, overall)
	defer cancel()

	var err error
	for attempt := 1; attempt <= sendMaxRetries; attempt++ {
		err = fn(ctx)
		if err == nil {
			return nil
		}
		// Don't retry parse errors — caller handles HTML fallback
		if parseErrRe.MatchString(err.Error()) {
			return err
		}
		if !isRetryableNetworkErr(err) || attempt == sendMaxRetries {
			return err
		}

		// If we hit a network-level connectivity issue (likely IPv6 routing),
		// arm sticky IPv4 fallback. Only triggers on "unreachable" — not timeouts
		// (which can be rate-limiting) or DNS errors (unrelated to IPv6).
		if strings.Contains(err.Error(), "unreachable") {
			c.enableIPv4Only()
		}

		// Honor Telegram's retry_after for 429 rate limit errors.
		delay := sendRetryDelay * time.Duration(attempt)
		var retryAPIErr *telegoapi.Error
		if errors.As(err, &retryAPIErr) && retryAPIErr.ErrorCode == 429 &&
			retryAPIErr.Parameters != nil && retryAPIErr.Parameters.RetryAfter > 0 {
			delay = time.Duration(retryAPIErr.Parameters.RetryAfter+1) * time.Second // +1s safety margin
		}

		slog.Warn("telegram send retry",
			"func", name, "attempt", attempt, "max", sendMaxRetries, "delay", delay, "error", err)
		if resetFn != nil {
			resetFn()
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-time.After(delay):
		}
	}
	return err
}

// Send delivers an outbound message to a Telegram chat.
// Supports text-only messages and messages with media attachments.
// Reads metadata for reply-to-message and forum thread routing.
func (c *Channel) Send(ctx context.Context, msg bus.OutboundMessage) error {
	if !c.IsRunning() {
		return fmt.Errorf("telegram bot not running")
	}

	// Use localKey for sync.Map lookups (composite key with topic suffix).
	localKey := msg.ChatID
	if lk := msg.Metadata["local_key"]; lk != "" {
		localKey = lk
	}

	// Parse raw Telegram chat ID (strips :topic:N suffix).
	chatID, err := parseRawChatID(localKey)
	if err != nil {
		return fmt.Errorf("invalid chat ID: %w", err)
	}

	// Parse reply/thread IDs from metadata.
	var replyToMsgID, threadID int
	if v := msg.Metadata["reply_to_message_id"]; v != "" {
		fmt.Sscanf(v, "%d", &replyToMsgID)
	}
	if v := msg.Metadata["message_thread_id"]; v != "" {
		fmt.Sscanf(v, "%d", &threadID)
	}

	// Fallback: extract threadID from localKey suffix (e.g. "-100123:topic:42").
	// This covers cases where metadata is absent, such as pairing approval notifications
	// routed via SendToChannel which only has a chatID string.
	if threadID == 0 {
		if idx := strings.Index(localKey, ":topic:"); idx > 0 {
			fmt.Sscanf(localKey[idx+7:], "%d", &threadID)
		} else if idx := strings.Index(localKey, ":thread:"); idx > 0 {
			fmt.Sscanf(localKey[idx+8:], "%d", &threadID)
		}
	}

	// Captured draft cleanup: if this message follows a DM stream that used the
	// draft transport, we must clear the stale draft as soon as this bubble is sent.
	if pID, ok := c.pendingDraftID.LoadAndDelete(localKey); ok {
		draftID := pID.(int)
		go func() {
			params := &telego.SendMessageDraftParams{
				ChatID:          chatID,
				DraftID:         draftID,
				Text:            "",
				MessageThreadID: resolveThreadIDForSend(threadID),
			}
			// Best-effort with Background ctx — caller ctx may already be cancelled.
			if err := c.bot.SendMessageDraft(context.Background(), params); err != nil {
				slog.Debug("telegram: draft clear failed (cosmetic)", "chat_id", chatID, "draft_id", draftID, "error", err)
			}
		}()
	}

	// Placeholder update (e.g. LLM retry notification): edit the placeholder
	// but keep it alive for the final response. Don't stop typing or cleanup.
	if msg.Metadata["placeholder_update"] == "true" {
		return c.updatePlaceholder(ctx, localKey, chatID, msg.Content, replyToMsgID, threadID)
	}

	// Stop thinking animation
	if stop, ok := c.stopThinking.Load(localKey); ok {
		if cf, ok := stop.(*thinkingCancel); ok {
			cf.Cancel()
		}
		c.stopThinking.Delete(localKey)
	}

	// Stop typing indicator controller (TTL keepalive)
	if ctrl, ok := c.typingCtrls.LoadAndDelete(localKey); ok {
		ctrl.(*typing.Controller).Stop()
	}

	// NO_REPLY cleanup: content is empty when agent suppresses reply (prompt injection, etc.).
	// Clean up placeholder, then return without sending any message.
	if msg.Content == "" && len(msg.Media) == 0 {
		if pID, ok := c.placeholders.Load(localKey); ok {
			c.placeholders.Delete(localKey)
			_ = c.deleteMessage(ctx, chatID, pID.(int))
		}
		return nil
	}

	// Handle media attachments if present
	if len(msg.Media) > 0 {
		// Delete placeholder since we're sending media
		if pID, ok := c.placeholders.Load(localKey); ok {
			c.placeholders.Delete(localKey)
			_ = c.deleteMessage(ctx, chatID, pID.(int))
		}
		err := c.sendMediaMessage(ctx, chatID, msg, replyToMsgID, threadID)
		// Migration fallback: group upgraded to supergroup — retry with new chat ID.
		if err != nil {
			if newChatID := extractMigrateChatID(err); newChatID != 0 {
				slog.Info("telegram: group migrated to supergroup (media send-path)",
					"old_chat_id", chatID, "new_chat_id", newChatID)
				c.migrateGroupChat(ctx, chatID, newChatID)
				return c.sendMediaMessage(ctx, newChatID, msg, replyToMsgID, threadID)
			}
		}
		return err
	}

	// TTS auto-apply: convert [[tts]] tagged responses to voice
	if c.audioMgr != nil && msg.Content != "" {
		isVoiceInbound := msg.Metadata["is_voice_inbound"] == "true"
		ttsResult, ttsErr := c.audioMgr.AutoApplyToText(ctx, msg.Content, "telegram", isVoiceInbound, "")
		if ttsErr != nil {
			slog.Debug("telegram: tts auto-apply error", "error", ttsErr)
		}
		if ttsResult != nil && ttsResult.AudioPath != "" {
			// Send voice message instead of text
			if err := c.sendVoice(ctx, tu.ID(chatID), ttsResult.AudioPath, "", replyToMsgID, threadID); err != nil {
				slog.Warn("telegram: tts auto-apply voice send failed, falling back to text", "error", err)
			} else {
				// Voice sent successfully
				strippedText := strings.TrimSpace(ttsResult.Text)
				if strippedText == "" {
					// Voice-only: delete placeholder (no text to show)
					if pID, ok := c.placeholders.LoadAndDelete(localKey); ok {
						if msgID, ok := pID.(int); ok && msgID > 0 {
							_ = c.deleteMessage(ctx, chatID, msgID)
						}
					}
					return nil
				}
				// Has remaining text: let normal flow handle placeholder edit
				msg.Content = strippedText
			}
		}
		// Update content with directives stripped (even if TTS not applied)
		if ttsResult != nil {
			msg.Content = ttsResult.Text
		}
	}

	// Text-only message
	htmlContent := markdownToTelegramHTML(msg.Content)
	chunks := chunkHTML(htmlContent, telegramMaxMessageLen)

	// If a stream message exists (stored by FinalizeStream), edit the first chunk
	// into it instead of deleting. This prevents the message from vanishing
	// when HTML conversion makes content exceed the size limit.
	startChunk := 0
	if pID, ok := c.placeholders.Load(localKey); ok {
		c.placeholders.Delete(localKey)
		msgID := pID.(int)

		if msgID == -1 {
			// SIGNAL from stream: A message transport send likely landed but ID was never retrieved.
			// Swallow the first chunk ONLY if there are more chunks to come (minimizes visible duplicate).
			// If it is the ONLY chunk, we deliver it anyway to guarantee the user sees the answer.
			if len(chunks) > 1 {
				slog.Warn("telegram: ghost message detected, skipping first chunk of multi-chunk response", "chat_id", chatID)
				startChunk = 1
			}
		} else {
			err := c.editMessage(ctx, chatID, msgID, chunks[0])
			if err == nil {
				startChunk = 1 // first chunk edited into stream message
			} else if isPostConnectNetworkErr(err) && len(chunks) > 1 {
				// Mid-stream timeout/lost connection: the edit likely reached Telegram
				// but the response was lost. Swallow and skip chunk 0 ONLY for multi-chunk
				// messages where the rest of the answer is still coming.
				slog.Warn("telegram: final edit timed out or lost, skipping chunk 0 of multi-chunk response",
					"chat_id", chatID, "message_id", msgID, "error", err)
				startChunk = 1
			} else if isRetryableNetworkErr(err) {
				// Retryable error (429 rate limit, 5xx, network). The stream message
				// still exists with valid streamed content — don't delete it.
				// Sending fresh would also fail, so keep the stream message as-is.
				slog.Warn("telegram: final edit failed with retryable error, keeping stream message",
					"chat_id", chatID, "message_id", msgID, "error", err)
				return nil
			} else {
				// Edit failed definitely (400 rejection), or a single-chunk edit timed out.
				// For single-chunk answers, we delete (best-effort) and send fresh to
				// guarantee the user gets the content.
				_ = c.deleteMessage(ctx, chatID, msgID)
			}
		}
	}

	// Send remaining chunks (or all chunks if no stream message was edited).
	for i := startChunk; i < len(chunks); i++ {
		replyTo := 0
		if i == 0 {
			replyTo = replyToMsgID // only first chunk replies to user's message
		}
		if err := c.sendHTML(ctx, chatID, chunks[i], replyTo, threadID); err != nil {
			return err
		}
	}
	return nil
}

// sendMediaMessage sends a message with media attachments.
// Ref: TS src/telegram/send.ts → sendMessageTelegram with mediaUrl
func (c *Channel) sendMediaMessage(ctx context.Context, chatID int64, msg bus.OutboundMessage, replyTo, threadID int) error {
	chatIDObj := tu.ID(chatID)
	items, err := c.prepareTelegramMediaItems(msg)
	if err != nil {
		return err
	}

	for _, chunk := range chunkTelegramMediaItems(items) {
		if chunk.grouped {
			if err := c.sendTelegramMediaGroup(ctx, chatIDObj, chunk.items, replyTo, threadID); err != nil {
				return err
			}
			replyTo = 0
			for _, item := range chunk.items {
				if err := c.sendTelegramMediaFollowUp(ctx, chatID, item.followUpText, threadID); err != nil {
					return err
				}
			}
			continue
		}

		for _, item := range chunk.items {
			if err := c.sendSingleTelegramMediaItem(ctx, chatIDObj, item, replyTo, threadID); err != nil {
				return err
			}
			replyTo = 0
			if err := c.sendTelegramMediaFollowUp(ctx, chatID, item.followUpText, threadID); err != nil {
				return err
			}
		}
	}
	return nil
}

func (c *Channel) validateOutboundMediaSize(path string) error {
	info, err := os.Stat(path)
	if err != nil {
		return nil
	}

	maxBytes := c.outboundMediaMaxBytes()
	if info.Size() > maxBytes {
		return fmt.Errorf("outbound media too large for Telegram upload: %d bytes (limit %d)", info.Size(), maxBytes)
	}
	return nil
}

func (c *Channel) outboundMediaMaxBytes() int64 {
	if c.config.APIServer == "" {
		return officialAPIOutboundMaxBytes
	}
	if c.config.MediaMaxBytes > localAPIDefaultMaxBytes {
		return c.config.MediaMaxBytes
	}
	return localAPIDefaultMaxBytes
}

// sendHTML sends a single HTML message, falling back to plain text if Telegram rejects the HTML.
// replyTo and threadID are optional (0 = omit). General topic (1) is handled by resolveThreadIDForSend.
func (c *Channel) sendHTML(ctx context.Context, chatID int64, htmlContent string, replyTo, threadID int) error {
	return c.sendHTMLWithDepth(ctx, chatID, htmlContent, replyTo, threadID, 0)
}

func (c *Channel) updatePlaceholder(ctx context.Context, localKey string, chatID int64, content string, replyTo, threadID int) error {
	if strings.TrimSpace(content) == "" {
		return nil
	}
	htmlContent := html.EscapeString(content)
	if pID, ok := c.placeholders.Load(localKey); ok {
		_ = c.editMessage(ctx, chatID, pID.(int), htmlContent)
		return nil
	}

	msg, err := c.sendPlaceholder(ctx, chatID, htmlContent, replyTo, threadID)
	if err != nil {
		if newChatID := extractMigrateChatID(err); newChatID != 0 {
			slog.Info("telegram: group migrated to supergroup (placeholder update)",
				"old_chat_id", chatID, "new_chat_id", newChatID)
			c.migrateGroupChat(ctx, chatID, newChatID)
			msg, err = c.sendPlaceholder(ctx, newChatID, htmlContent, replyTo, threadID)
		}
		if err != nil {
			return err
		}
	}
	if msg != nil && msg.MessageID > 0 {
		c.placeholders.Store(localKey, msg.MessageID)
	}
	return nil
}

func (c *Channel) sendPlaceholder(ctx context.Context, chatID int64, htmlContent string, replyTo, threadID int) (*telego.Message, error) {
	tgMsg := tu.Message(tu.ID(chatID), htmlContent)
	tgMsg.ParseMode = telego.ModeHTML
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		tgMsg.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		tgMsg.ReplyParameters = &telego.ReplyParameters{
			MessageID:                replyTo,
			AllowSendingWithoutReply: true,
		}
	}

	var sent *telego.Message
	err := c.retrySend(ctx, "sendMessage", nil, func(ctx context.Context) error {
		var sendErr error
		sent, sendErr = c.bot.SendMessage(ctx, tgMsg)
		return sendErr
	})
	return sent, err
}

func (c *Channel) sendHTMLWithDepth(ctx context.Context, chatID int64, htmlContent string, replyTo, threadID, depth int) error {
	tgMsg := tu.Message(tu.ID(chatID), htmlContent)
	tgMsg.ParseMode = telego.ModeHTML

	// TS ref: buildTelegramThreadParams() — General topic (1) must be omitted.
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		tgMsg.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		tgMsg.ReplyParameters = &telego.ReplyParameters{
			MessageID:                replyTo,
			AllowSendingWithoutReply: true, // don't fail if replied-to message was deleted
		}
	}

	err := c.retrySend(ctx, "sendMessage", nil, func(ctx context.Context) error {
		_, e := c.bot.SendMessage(ctx, tgMsg)
		return e
	})

	if err != nil {
		// Case 0: Group migrated to supergroup — update DB and retry with new chat ID.
		if newChatID := extractMigrateChatID(err); newChatID != 0 {
			slog.Info("telegram: group migrated to supergroup (send-path)",
				"old_chat_id", chatID, "new_chat_id", newChatID)
			c.migrateGroupChat(ctx, chatID, newChatID)
			if depth < maxSplitDepth {
				return c.sendHTMLWithDepth(ctx, newChatID, htmlContent, replyTo, threadID, depth+1)
			}
			return fmt.Errorf("migration retry depth exceeded: %w", err)
		}

		errStr := err.Error()

		// Case 1: Message too long. Split into smaller chunks and send individually.
		if messageTooLongRe.MatchString(errStr) {
			if depth >= maxSplitDepth {
				return fmt.Errorf("max split depth (%d) exceeded: %w", maxSplitDepth, err)
			}
			slog.Warn("Telegram rejected message as too long, splitting further", "len", len(htmlContent), "depth", depth)
			newMaxLen := len(htmlContent) / 2
			if newMaxLen < 100 {
				return err // too small to split meaningfully
			}

			innerChunks := chunkHTML(htmlContent, newMaxLen)
			for i, chunk := range innerChunks {
				r := 0
				if i == 0 {
					r = replyTo
				}
				if sendErr := c.sendHTMLWithDepth(ctx, chatID, chunk, r, threadID, depth+1); sendErr != nil {
					return sendErr
				}
			}
			return nil
		}

		// Case 2: Parse error. Fallback to plain text.
		if parseErrRe.MatchString(errStr) {
			slog.Warn("HTML parse failed, falling back to plain text", "error", err)
			tgMsg.ParseMode = ""
			tgMsg.Text = stripHTML(htmlContent)
			_, err = c.bot.SendMessage(ctx, tgMsg)

			// If plain text is STILL too long, split it.
			if err != nil && messageTooLongRe.MatchString(err.Error()) {
				slog.Warn("Plain text fallback too long, splitting further", "len", len(tgMsg.Text))
				innerChunks := chunkPlainText(tgMsg.Text, 4000) // use default safe limit
				for i, chunk := range innerChunks {
					msg := tu.Message(tu.ID(chatID), chunk)
					msg.ReplyParameters = tgMsg.ReplyParameters
					if i > 0 {
						msg.ReplyParameters = nil
					}
					msg.MessageThreadID = tgMsg.MessageThreadID
					_, err = c.bot.SendMessage(ctx, msg)
					if err != nil {
						return err
					}
				}
				return nil
			}
		}

		// Case 3: Thread not found. Re-check err (may have changed after Case 2 fallback).
		if err != nil && tgMsg.MessageThreadID != 0 && threadNotFoundRe.MatchString(err.Error()) {
			slog.Warn("thread not found, retrying without message_thread_id", "thread_id", tgMsg.MessageThreadID)
			tgMsg.MessageThreadID = 0
			_, err = c.bot.SendMessage(ctx, tgMsg)
		}
	}
	return err
}

// sendPhoto sends a photo message.
func (c *Channel) sendPhoto(ctx context.Context, chatID telego.ChatID, filePath, caption string, replyTo, threadID int) error {
	file, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("open photo %s: %w", filePath, err)
	}
	defer file.Close()

	params := &telego.SendPhotoParams{
		ChatID:  chatID,
		Photo:   telego.InputFile{File: file},
		Caption: caption,
	}
	if caption != "" {
		params.ParseMode = telego.ModeHTML
	}
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		params.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		params.ReplyParameters = &telego.ReplyParameters{MessageID: replyTo, AllowSendingWithoutReply: true}
	}

	err = c.retrySend(ctx, "sendPhoto", func() { file.Seek(0, 0) }, func(ctx context.Context) error {
		_, e := c.bot.SendPhoto(ctx, params)
		return e
	})
	if err != nil && parseErrRe.MatchString(err.Error()) {
		slog.Warn("sendPhoto: HTML parse failed, retrying with plain text caption", "error", err)
		file.Seek(0, 0)
		params.ParseMode = ""
		params.Caption = stripHTML(params.Caption)
		_, err = c.bot.SendPhoto(ctx, params)
	}
	if err != nil && params.MessageThreadID != 0 && threadNotFoundRe.MatchString(err.Error()) {
		slog.Warn("sendPhoto: thread not found, retrying without thread", "thread_id", params.MessageThreadID)
		file.Seek(0, 0)
		params.MessageThreadID = 0
		_, err = c.bot.SendPhoto(ctx, params)
	}
	return err
}

// sendVideo sends a video message.
func (c *Channel) sendVideo(ctx context.Context, chatID telego.ChatID, filePath, caption string, replyTo, threadID int) error {
	file, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("open video %s: %w", filePath, err)
	}
	defer file.Close()

	params := &telego.SendVideoParams{
		ChatID:  chatID,
		Video:   telego.InputFile{File: file},
		Caption: caption,
	}
	if caption != "" {
		params.ParseMode = telego.ModeHTML
	}
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		params.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		params.ReplyParameters = &telego.ReplyParameters{MessageID: replyTo, AllowSendingWithoutReply: true}
	}

	err = c.retrySend(ctx, "sendVideo", func() { file.Seek(0, 0) }, func(ctx context.Context) error {
		_, e := c.bot.SendVideo(ctx, params)
		return e
	})
	if err != nil && parseErrRe.MatchString(err.Error()) {
		slog.Warn("sendVideo: HTML parse failed, retrying with plain text caption", "error", err)
		file.Seek(0, 0)
		params.ParseMode = ""
		params.Caption = stripHTML(params.Caption)
		_, err = c.bot.SendVideo(ctx, params)
	}
	if err != nil && params.MessageThreadID != 0 && threadNotFoundRe.MatchString(err.Error()) {
		slog.Warn("sendVideo: thread not found, retrying without thread", "thread_id", params.MessageThreadID)
		file.Seek(0, 0)
		params.MessageThreadID = 0
		_, err = c.bot.SendVideo(ctx, params)
	}
	return err
}

// sendAudio sends an audio message.
func (c *Channel) sendAudio(ctx context.Context, chatID telego.ChatID, filePath, caption string, replyTo, threadID int) error {
	file, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("open audio %s: %w", filePath, err)
	}
	defer file.Close()

	params := &telego.SendAudioParams{
		ChatID:  chatID,
		Audio:   telego.InputFile{File: file},
		Caption: caption,
	}
	if caption != "" {
		params.ParseMode = telego.ModeHTML
	}
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		params.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		params.ReplyParameters = &telego.ReplyParameters{MessageID: replyTo, AllowSendingWithoutReply: true}
	}

	err = c.retrySend(ctx, "sendAudio", func() { file.Seek(0, 0) }, func(ctx context.Context) error {
		_, e := c.bot.SendAudio(ctx, params)
		return e
	})
	if err != nil && parseErrRe.MatchString(err.Error()) {
		slog.Warn("sendAudio: HTML parse failed, retrying with plain text caption", "error", err)
		file.Seek(0, 0)
		params.ParseMode = ""
		params.Caption = stripHTML(params.Caption)
		_, err = c.bot.SendAudio(ctx, params)
	}
	if err != nil && params.MessageThreadID != 0 && threadNotFoundRe.MatchString(err.Error()) {
		slog.Warn("sendAudio: thread not found, retrying without thread", "thread_id", params.MessageThreadID)
		file.Seek(0, 0)
		params.MessageThreadID = 0
		_, err = c.bot.SendAudio(ctx, params)
	}
	return err
}

// sendVoice sends an audio file as a voice message (inline playable bubble).
// Telegram supports OGG (Opus), MP3, and M4A for voice messages.
func (c *Channel) sendVoice(ctx context.Context, chatID telego.ChatID, filePath, caption string, replyTo, threadID int) error {
	file, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("open voice %s: %w", filePath, err)
	}
	defer file.Close()

	params := &telego.SendVoiceParams{
		ChatID:  chatID,
		Voice:   telego.InputFile{File: file},
		Caption: caption,
	}
	if caption != "" {
		params.ParseMode = telego.ModeHTML
	}
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		params.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		params.ReplyParameters = &telego.ReplyParameters{MessageID: replyTo, AllowSendingWithoutReply: true}
	}

	err = c.retrySend(ctx, "sendVoice", func() { file.Seek(0, 0) }, func(ctx context.Context) error {
		_, e := c.bot.SendVoice(ctx, params)
		return e
	})
	if err != nil && parseErrRe.MatchString(err.Error()) {
		slog.Warn("sendVoice: HTML parse failed, retrying with plain text caption", "error", err)
		file.Seek(0, 0)
		params.ParseMode = ""
		params.Caption = stripHTML(params.Caption)
		_, err = c.bot.SendVoice(ctx, params)
	}
	if err != nil && params.MessageThreadID != 0 && threadNotFoundRe.MatchString(err.Error()) {
		slog.Warn("sendVoice: thread not found, retrying without thread", "thread_id", params.MessageThreadID)
		file.Seek(0, 0)
		params.MessageThreadID = 0
		_, err = c.bot.SendVoice(ctx, params)
	}
	return err
}

// isVoiceCompatible returns true if content-type is supported by Telegram SendVoice.
// Supported: OGG (Opus), MP3, M4A per Telegram Bot API docs.
func isVoiceCompatible(ct string) bool {
	return ct == "audio/ogg" || ct == "audio/mpeg" || ct == "audio/mp3" ||
		ct == "audio/m4a" || ct == "audio/x-m4a"
}

// sendDocument sends a document/file message.
func (c *Channel) sendDocument(ctx context.Context, chatID telego.ChatID, filePath, caption string, replyTo, threadID int) error {
	file, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("open document %s: %w", filePath, err)
	}
	defer file.Close()

	params := &telego.SendDocumentParams{
		ChatID:   chatID,
		Document: telego.InputFile{File: file},
		Caption:  caption,
	}
	if caption != "" {
		params.ParseMode = telego.ModeHTML
	}
	if sendThreadID := resolveThreadIDForSend(threadID); sendThreadID > 0 {
		params.MessageThreadID = sendThreadID
	}
	if replyTo > 0 {
		params.ReplyParameters = &telego.ReplyParameters{MessageID: replyTo, AllowSendingWithoutReply: true}
	}

	err = c.retrySend(ctx, "sendDocument", func() { file.Seek(0, 0) }, func(ctx context.Context) error {
		_, e := c.bot.SendDocument(ctx, params)
		return e
	})
	if err != nil && parseErrRe.MatchString(err.Error()) {
		slog.Warn("sendDocument: HTML parse failed, retrying with plain text caption", "error", err)
		file.Seek(0, 0)
		params.ParseMode = ""
		params.Caption = stripHTML(params.Caption)
		_, err = c.bot.SendDocument(ctx, params)
	}
	if err != nil && params.MessageThreadID != 0 && threadNotFoundRe.MatchString(err.Error()) {
		slog.Warn("sendDocument: thread not found, retrying without thread", "thread_id", params.MessageThreadID)
		file.Seek(0, 0)
		params.MessageThreadID = 0
		_, err = c.bot.SendDocument(ctx, params)
	}
	return err
}

// EditMessage edits an existing message's text by chat id string, applying the
// same markdown→HTML rendering as outbound sends. Implements channels.MessageEditor
// so the agent's `message` tool (action=edit) can flip status markers in place.
// The bot must be an admin with edit rights in the target chat/channel.
func (c *Channel) EditMessage(ctx context.Context, chatID string, messageID int, content string) error {
	id, err := strconv.ParseInt(chatID, 10, 64)
	if err != nil {
		return fmt.Errorf("invalid telegram chat id %q: %w", chatID, err)
	}
	html := markdownToTelegramHTML(content)
	err = c.editMessage(ctx, id, messageID, html)
	// Media messages (photo/document with a caption, e.g. a receipt image with a
	// status line) have no text — editMessageText returns "there is no text in the
	// message to edit". Fall back to editing the caption instead.
	if err != nil && noTextToEditRe.MatchString(err.Error()) {
		return c.editMessageCaption(ctx, id, messageID, html)
	}
	return err
}

// ReactToMessage sets a single emoji reaction on a message (implements
// channels.MessageReactor). Only Telegram-supported reaction emojis are allowed
// — ✅/❌ are not among them, so callers must pass e.g. 👍. Reacting to the bot's
// own status post is allowed.
func (c *Channel) ReactToMessage(ctx context.Context, chatID string, messageID int, emoji string) error {
	if !telegramSupportedEmojis[emoji] {
		return fmt.Errorf("emoji %q is not a supported Telegram reaction", emoji)
	}
	id, err := parseRawChatID(chatID)
	if err != nil {
		return fmt.Errorf("invalid telegram chat id %q: %w", chatID, err)
	}
	return c.bot.SetMessageReaction(ctx, &telego.SetMessageReactionParams{
		ChatID:    tu.ID(id),
		MessageID: messageID,
		Reaction: []telego.ReactionType{
			&telego.ReactionTypeEmoji{Type: telego.ReactionEmoji, Emoji: emoji},
		},
	})
}

// editMessageCaption edits the caption of a media message (photo/document).
func (c *Channel) editMessageCaption(ctx context.Context, chatID int64, messageID int, htmlCaption string) error {
	editCap := &telego.EditMessageCaptionParams{
		ChatID:    tu.ID(chatID),
		MessageID: messageID,
		Caption:   htmlCaption,
		ParseMode: telego.ModeHTML,
	}
	return c.retrySend(ctx, "editMessageCaption", nil, func(ctx context.Context) error {
		_, err := c.bot.EditMessageCaption(ctx, editCap)
		if err != nil && messageNotModifiedRe.MatchString(err.Error()) {
			return nil
		}
		return err
	})
}

// PostToTopic posts a message into a forum topic (thread) and returns the sent
// message id, so the agent can remember it and edit that exact post later.
// Implements channels.TopicMessagePoster. Applies the same markdown→HTML render
// as regular sends. threadID <= 0 posts to the group's General topic.
func (c *Channel) PostToTopic(ctx context.Context, chatID string, threadID int, content string) (int, error) {
	id, err := strconv.ParseInt(chatID, 10, 64)
	if err != nil {
		return 0, fmt.Errorf("invalid telegram chat id %q: %w", chatID, err)
	}
	msg := tu.Message(tu.ID(id), markdownToTelegramHTML(content))
	msg.ParseMode = telego.ModeHTML
	if threadID > 0 {
		msg.MessageThreadID = threadID
	}
	var sentID int
	err = c.retrySend(ctx, "sendMessage", nil, func(ctx context.Context) error {
		sent, e := c.bot.SendMessage(ctx, msg)
		if e != nil {
			return e
		}
		if sent != nil {
			sentID = sent.MessageID
		}
		return nil
	})
	return sentID, err
}

// editMessage edits an existing message's text.
// Uses retrySend since edits are idempotent and may fail on transient network issues.
func (c *Channel) editMessage(ctx context.Context, chatID int64, messageID int, htmlText string) error {
	editMsg := tu.EditMessageText(tu.ID(chatID), messageID, htmlText)
	editMsg.ParseMode = telego.ModeHTML

	return c.retrySend(ctx, "editMessage", nil, func(ctx context.Context) error {
		_, err := c.bot.EditMessageText(ctx, editMsg)
		if err != nil {
			// Ignore "message is not modified" errors (idempotent edit)
			if messageNotModifiedRe.MatchString(err.Error()) {
				return nil
			}
			return err
		}
		return nil
	})
}

// deleteMessage deletes a message from the chat.
func (c *Channel) deleteMessage(ctx context.Context, chatID int64, messageID int) error {
	return c.bot.DeleteMessage(ctx, &telego.DeleteMessageParams{
		ChatID:    tu.ID(chatID),
		MessageID: messageID,
	})
}