package discord

import (
	"context"
	"fmt"
	"log/slog"
	"path/filepath"
	"strings"
	"time"

	"github.com/bwmarrin/discordgo"

	"github.com/nextlevelbuilder/goclaw/internal/audio"
	"github.com/nextlevelbuilder/goclaw/internal/bus"
	"github.com/nextlevelbuilder/goclaw/internal/channels"
	"github.com/nextlevelbuilder/goclaw/internal/channels/media"
	"github.com/nextlevelbuilder/goclaw/internal/channels/typing"
	"github.com/nextlevelbuilder/goclaw/internal/store"
	"github.com/nextlevelbuilder/goclaw/internal/systemmessages"
	"github.com/nextlevelbuilder/goclaw/internal/tools"
)

// handleMessage processes incoming Discord messages.
func (c *Channel) handleMessage(_ *discordgo.Session, m *discordgo.MessageCreate) {
	ctx := context.Background()
	ctx = store.WithTenantID(ctx, c.TenantID())
	// Ignore bot's own messages
	if m.Author == nil || m.Author.ID == c.botUserID {
		return
	}

	// Ignore bot messages
	if m.Author.Bot {
		return
	}

	senderID := m.Author.ID
	displayName := resolveDisplayName(m)
	authorLabel := discordAuthorLabel(m.Author, m.Member)

	channelID := m.ChannelID
	isDM := m.GuildID == ""

	// DM/Group policy check
	peerKind := "group"
	if isDM {
		peerKind = "direct"
	}

	// Pre-compute mention flag for groups so policy gating can suppress
	// pairing replies when the bot was not addressed.
	mentioned := false
	if !isDM {
		for _, u := range m.Mentions {
			if u.ID == c.botUserID {
				mentioned = true
				break
			}
		}
		if !mentioned && m.ReferencedMessage != nil &&
			m.ReferencedMessage.Author != nil &&
			m.ReferencedMessage.Author.ID == c.botUserID {
			mentioned = true
		}
	}

	if isDM {
		if !c.checkDMPolicy(ctx, senderID, channelID) {
			return
		}
	} else {
		if !c.checkGroupPolicy(ctx, senderID, channelID, mentioned) {
			slog.Debug("discord group message rejected by policy",
				"user_id", senderID,
				"username", displayName,
			)
			return
		}
	}

	// Handle bot commands (writer management, etc.) before further processing.
	if c.tryHandleCommand(m) {
		return
	}

	// Build content
	content := m.Content

	// Build reply context if replying to another message.
	if m.ReferencedMessage != nil {
		author := "unknown"
		if m.ReferencedMessage.Author != nil {
			author = discordAuthorLabel(m.ReferencedMessage.Author, m.ReferencedMessage.Member)
		}
		body := channels.Truncate(m.ReferencedMessage.Content, 500)
		replyCtx := fmt.Sprintf("[Replying to %s]\n%s\n[/Replying]", author, body)
		if content != "" {
			content = replyCtx + "\n\n" + content
		} else {
			content = replyCtx
		}
	}

	// Resolve media attachments (download files, classify types)
	maxBytes := c.config.MediaMaxBytes
	if maxBytes <= 0 {
		maxBytes = defaultMediaMaxBytes
	}
	mediaList := resolveMedia(m.Attachments, maxBytes)

	// Download media from replied-to message and merge (reply first, current second).
	if m.ReferencedMessage != nil && len(m.ReferencedMessage.Attachments) > 0 {
		replyMedia := resolveMedia(m.ReferencedMessage.Attachments, maxBytes)
		for i := range replyMedia {
			replyMedia[i].FromReply = true
		}
		mediaList = append(replyMedia, mediaList...)
	}

	// Process media: STT, document extraction, build tags
	var mediaFiles []bus.MediaFile
	if len(mediaList) > 0 {
		var extraContent strings.Builder
		for i := range mediaList {
			mi := &mediaList[i]

			switch mi.Type {
			case media.TypeAudio, media.TypeVoice:
				var transcript string
				var sttErr error
				if c.audioMgr != nil {
					sttCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
					res, err := c.audioMgr.Transcribe(sttCtx, audio.STTInput{FilePath: mi.FilePath, MimeType: "audio/ogg"}, audio.STTOptions{})
					cancel()
					if err == nil && res != nil {
						transcript = res.Text
					} else {
						sttErr = err
					}
				}
				if sttErr != nil {
					slog.Warn("discord: STT transcription failed",
						"type", mi.Type, "error", sttErr,
					)
				} else {
					mi.Transcript = transcript
				}

			case media.TypeDocument:
				if mi.FileName != "" && mi.FilePath != "" {
					docContent, err := media.ExtractDocumentContent(mi.FilePath, mi.FileName)
					if err != nil {
						slog.Warn("discord: document extraction failed", "file", mi.FileName, "error", err)
					} else if docContent != "" {
						extraContent.WriteString("\n\n" + docContent)
					}
				}
			}

			if mi.FilePath != "" {
				mediaFiles = append(mediaFiles, bus.MediaFile{
					Path:     mi.FilePath,
					MimeType: mi.ContentType,
					Filename: mi.FileName,
				})
			}
		}

		// Build media tags AFTER processing so transcript fields are populated.
		mediaTags := media.BuildMediaTags(mediaList)
		if mediaTags != "" {
			if content != "" {
				content = mediaTags + "\n\n" + content
			} else {
				content = mediaTags
			}
		}

		if extraContent.String() != "" {
			content += extraContent.String()
		}
	}

	if content == "" {
		content = "[empty message]"
	}

	// Mention gating: in groups, only respond when bot is @mentioned (default true).
	// When not mentioned, record message to pending history for later context.
	// `mentioned` was pre-computed above for policy gating.
	if peerKind == "group" && c.RequireMention() {
		if !mentioned {
			// Collect media file paths for group history context.
			var mediaPaths []string
			for _, mf := range mediaFiles {
				if mf.Path != "" {
					mediaPaths = append(mediaPaths, mf.Path)
				}
			}
			parentHistoryKey := c.parentHistoryKeyForChannel(ctx, channelID)
			c.GroupHistory().Record(channelID, channels.HistoryEntry{
				Sender:           authorLabel,
				SenderID:         senderID,
				Body:             content,
				ParentHistoryKey: parentHistoryKey,
				Media:            mediaPaths,
				Timestamp:        m.Timestamp,
				MessageID:        m.ID,
			}, c.HistoryLimit())

			// Collect contact even when bot is not mentioned (cache prevents DB spam).
			if cc := c.ContactCollector(); cc != nil {
				cc.EnsureContact(ctx, c.Type(), c.Name(), senderID, senderID, displayName, m.Author.Username, "group", "user", "", "")
				cc.EnsureContactWithMetadata(ctx, c.Type(), c.Name(), channelID, "", c.resolveCachedChannelTitle(channelID), "", "group", "group", "", "", c.cachedContactMetadata(channelID))
			}

			slog.Debug("discord group message recorded (no mention)",
				"channel_id", channelID,
				"user_id", senderID,
				"username", displayName,
			)
			return
		}
	}

	slog.Debug("discord message received",
		"sender_id", senderID,
		"channel_id", channelID,
		"is_dm", isDM,
		"preview", channels.Truncate(content, 50),
	)

	// Send typing indicator with keepalive + TTL safety net.
	// Discord typing expires after 10s, so keepalive every 9s.
	// TTL auto-stops after 60s to prevent stuck indicators.
	typingCtrl := typing.New(typing.Options{
		MaxDuration:       60 * time.Second,
		KeepaliveInterval: 9 * time.Second,
		StartFn: func() error {
			return c.session.ChannelTyping(channelID)
		},
	})
	// Stop previous typing controller for this channel (if any)
	if prev, ok := c.typingCtrls.Load(channelID); ok {
		prev.(*typing.Controller).Stop()
	}
	c.typingCtrls.Store(channelID, typingCtrl)
	typingCtrl.Start()

	// Send placeholder "Thinking..." message.
	// Key by inbound message ID (not channel ID) to avoid race conditions
	// when multiple messages arrive in the same channel concurrently.
	placeholder, err := c.session.ChannelMessageSend(channelID, "Thinking...")
	if err == nil {
		c.placeholders.Store(m.ID, placeholder.ID)
	}

	// Strip bot @mention from content — it's just the trigger, not meaningful.
	content = strings.ReplaceAll(content, "<@"+c.botUserID+">", "")
	content = strings.TrimSpace(content)

	threadBackfill := threadBackfillResult{}
	if peerKind == "group" && mentioned {
		threadBackfill = c.backfillThreadHistory(ctx, m, maxBytes)
		if len(threadBackfill.Media) > 0 {
			mediaFiles = append(threadBackfill.Media, mediaFiles...)
		}
	}
	hasThreadBackfill := threadBackfill.Context != "" || len(threadBackfill.Media) > 0

	// Build final content with group context.
	finalContent := content
	if peerKind == "group" {
		annotated := fmt.Sprintf("[From: %s (<@%s>)]\n%s", displayName, senderID, content)
		if threadBackfill.Context != "" {
			annotated = threadBackfill.Context + "\n\n" + annotated
		}
		if c.HistoryLimit() > 0 && !hasThreadBackfill {
			finalContent = c.GroupHistory().BuildContext(channelID, annotated, c.HistoryLimit())
		} else {
			finalContent = annotated
		}
		// Collect media from pending history entries (sent before this @mention).
		// Original filename not retained by CollectMedia; use disk basename so
		// persistMedia's sanitizer gets a meaningful stem instead of UUID fallback.
		if !hasThreadBackfill {
			histMediaPaths := c.GroupHistory().CollectMedia(channelID)
			for _, p := range histMediaPaths {
				mediaFiles = append(mediaFiles, bus.MediaFile{Path: p, Filename: filepath.Base(p)})
			}
		}
	}

	metadata := map[string]string{
		"message_id":      m.ID,
		"user_id":         senderID,
		"username":        m.Author.Username,
		"display_name":    channels.SanitizeDisplayName(displayName),
		"guild_id":        m.GuildID,
		"channel_id":      channelID,
		"is_dm":           fmt.Sprintf("%t", isDM),
		"placeholder_key": m.ID, // keyed by inbound message ID for placeholder lookup
	}
	if !isDM {
		if title := c.resolveCachedGroupDisplayTitle(channelID); title != "" {
			metadata[tools.MetaChatTitle] = title
		}
	}

	targetAgentID := c.targetAgentID(mediaList)

	// Collect contact for processed messages (DM + group-mentioned).
	if cc := c.ContactCollector(); cc != nil {
		cc.EnsureContact(ctx, c.Type(), c.Name(), senderID, senderID, displayName, m.Author.Username, peerKind, "user", "", "")
		if peerKind == "group" {
			cc.EnsureContactWithMetadata(ctx, c.Type(), c.Name(), channelID, "", c.resolveCachedChannelTitle(channelID), "", "group", "group", "", "", c.cachedContactMetadata(channelID))
		}
	}

	// Publish directly to bus (to preserve MediaFile MIME types)
	c.Bus().PublishInbound(bus.InboundMessage{
		Channel:  c.Name(),
		SenderID: senderID,
		ChatID:   channelID,
		Content:  finalContent,
		Media:    mediaFiles,
		PeerKind: peerKind,
		UserID:   senderID,
		AgentID:  targetAgentID,
		TenantID: c.TenantID(),
		Metadata: metadata,
	})

	// Clear pending history after sending to agent.
	if peerKind == "group" {
		c.GroupHistory().Clear(channelID)
	}
}

func (c *Channel) targetAgentID(mediaList []media.MediaInfo) string {
	targetAgentID := c.AgentID()
	if c.config.VoiceAgentID == "" {
		return targetAgentID
	}
	for _, mi := range mediaList {
		if mi.Type == media.TypeAudio || mi.Type == media.TypeVoice {
			slog.Debug("discord: routing voice inbound to speaking agent",
				"agent_id", c.config.VoiceAgentID, "media_type", mi.Type,
			)
			return c.config.VoiceAgentID
		}
	}
	return targetAgentID
}

// checkGroupPolicy evaluates the group policy for a sender, with pairing support.
// When RequireMention is enabled, pairing replies only fire if the bot was
// explicitly addressed — otherwise the bot stays silent in the channel.
func (c *Channel) checkGroupPolicy(ctx context.Context, senderID, channelID string, mentioned bool) bool {
	result := c.CheckGroupPolicy(ctx, senderID, channelID, c.config.GroupPolicy)
	switch result {
	case channels.PolicyAllow:
		return true
	case channels.PolicyNeedsPairing:
		if c.RequireMention() && !mentioned {
			return false
		}
		groupSenderID := fmt.Sprintf("group:%s", channelID)
		c.sendPairingReply(ctx, groupSenderID, channelID)
		return false
	default:
		return false
	}
}

// checkDMPolicy evaluates the DM policy for a sender, handling pairing flow.
func (c *Channel) checkDMPolicy(ctx context.Context, senderID, channelID string) bool {
	result := c.CheckDMPolicy(ctx, senderID, c.config.DMPolicy)
	switch result {
	case channels.PolicyAllow:
		return true
	case channels.PolicyNeedsPairing:
		c.sendPairingReply(ctx, senderID, channelID)
		return false
	default:
		slog.Debug("discord DM rejected by policy", "sender_id", senderID, "policy", c.config.DMPolicy)
		return false
	}
}

// sendPairingReply sends a pairing code to the user via DM.
func (c *Channel) sendPairingReply(ctx context.Context, senderID, channelID string) {
	ps := c.PairingService()
	if ps == nil {
		return
	}

	if !c.CanSendPairingNotif(senderID, pairingDebounceTime) {
		return
	}

	code, err := ps.RequestPairing(ctx, senderID, c.Name(), channelID, "default", nil)
	if err != nil {
		slog.Debug("discord pairing request failed", "sender_id", senderID, "error", err)
		return
	}

	replyText := c.SystemMessage("", systemmessages.KeyPairingAccountRequired, systemmessages.Vars{
		"platform":  "Discord",
		"sender_id": senderID,
		"code":      code,
	})

	if _, err := c.session.ChannelMessageSend(channelID, replyText); err != nil {
		slog.Warn("failed to send discord pairing reply", "error", err)
	} else {
		c.MarkPairingNotifSent(senderID)
		slog.Info("discord pairing reply sent", "sender_id", senderID, "code", code)
	}
}

// resolveDisplayName returns the best available display name for a Discord message author.
// Priority: server nickname > global display name > username.
func resolveDisplayName(m *discordgo.MessageCreate) string {
	if m == nil {
		return ""
	}
	return discordDisplayName(m.Author, m.Member)
}

func discordAuthorLabel(user *discordgo.User, member *discordgo.Member) string {
	display := discordDisplayName(user, member)
	if display == "" {
		display = "unknown"
	}
	handle := discordHandle(user)
	if handle == "" && user != nil {
		handle = user.Username
	}
	if user == nil || user.ID == "" {
		if handle == "" {
			return display
		}
		return fmt.Sprintf("%s (@%s)", display, handle)
	}
	if handle == "" {
		return fmt.Sprintf("%s (id: %s)", display, user.ID)
	}
	return fmt.Sprintf("%s (@%s, id: %s)", display, handle, user.ID)
}

func discordDisplayName(user *discordgo.User, member *discordgo.Member) string {
	if member != nil {
		if member.Nick != "" {
			return member.Nick
		}
		if member.User != nil {
			if member.User.GlobalName != "" {
				return member.User.GlobalName
			}
			if member.User.Username != "" {
				return member.User.Username
			}
		}
	}
	if user == nil {
		return ""
	}
	if user.GlobalName != "" {
		return user.GlobalName
	}
	return user.Username
}

func discordHandle(user *discordgo.User) string {
	if user == nil {
		return ""
	}
	handle := strings.TrimSpace(user.Username)
	if handle == "" {
		return ""
	}
	if user.Discriminator != "" && user.Discriminator != "0" {
		return handle + "#" + user.Discriminator
	}
	return handle
}

func (c *Channel) resolveCachedChannelTitle(channelID string) string {
	if c == nil || c.session == nil || c.session.State == nil || channelID == "" {
		return ""
	}
	ch, err := c.session.State.Channel(channelID)
	if err != nil || ch == nil {
		return ""
	}
	return channels.SanitizeDisplayName(ch.Name)
}

func (c *Channel) cachedContactMetadata(channelID string) map[string]string {
	if c == nil || c.session == nil || c.session.State == nil || channelID == "" {
		return nil
	}
	ch, err := c.session.State.Channel(channelID)
	if err != nil || ch == nil {
		return nil
	}
	return discordContactMetadata(ch, func(id string) *discordgo.Channel {
		parent, _ := c.session.State.Channel(id)
		return parent
	})
}

func (c *Channel) ResolveGroupTitle(_ context.Context, channelID string) (string, error) {
	if title := c.resolveCachedChannelTitle(channelID); title != "" {
		return title, nil
	}
	return "", fmt.Errorf("discord channel title not cached")
}

func (c *Channel) ResolveGroupTitles(ctx context.Context, channelIDs []string) (map[string]string, error) {
	if c == nil || c.session == nil || len(channelIDs) == 0 {
		return map[string]string{}, nil
	}
	remaining := make(map[string]struct{}, len(channelIDs))
	titles := make(map[string]string, len(channelIDs))
	for _, id := range channelIDs {
		if id == "" {
			continue
		}
		if title := c.resolveCachedChannelTitle(id); title != "" {
			titles[id] = title
			continue
		}
		remaining[id] = struct{}{}
	}
	if len(remaining) == 0 {
		return titles, nil
	}

	var guildIDs []string
	if c.session.State != nil {
		c.session.State.RLock()
		guildIDs = make([]string, 0, len(c.session.State.Guilds))
		for _, guild := range c.session.State.Guilds {
			if guild != nil && guild.ID != "" {
				guildIDs = append(guildIDs, guild.ID)
			}
		}
		c.session.State.RUnlock()
	}

	for _, guildID := range guildIDs {
		select {
		case <-ctx.Done():
			return titles, nil
		default:
		}
		lookupCtx, cancel := context.WithTimeout(ctx, 750*time.Millisecond)
		guildChannels, err := c.session.GuildChannels(guildID, discordgo.WithContext(lookupCtx))
		cancel()
		if err != nil {
			slog.Debug("discord channel title batch lookup failed", "guild_id", guildID, "error", err)
			continue
		}
		for _, ch := range guildChannels {
			if ch == nil {
				continue
			}
			if _, ok := remaining[ch.ID]; !ok {
				continue
			}
			if title := channels.SanitizeDisplayName(ch.Name); title != "" {
				titles[ch.ID] = title
				delete(remaining, ch.ID)
			}
		}
		if len(remaining) == 0 {
			break
		}
	}
	for id := range remaining {
		select {
		case <-ctx.Done():
			return titles, nil
		default:
		}
		lookupCtx, cancel := context.WithTimeout(ctx, 750*time.Millisecond)
		ch, err := c.session.Channel(id, discordgo.WithContext(lookupCtx))
		cancel()
		if err != nil {
			slog.Debug("discord channel title direct lookup failed", "channel_id", id, "error", err)
			continue
		}
		if ch == nil {
			continue
		}
		if title := channels.SanitizeDisplayName(ch.Name); title != "" {
			titles[id] = title
		}
	}
	return titles, nil
}