package chat

import (
	"context"
	"encoding/json"
	"regexp"
	"strings"
	"time"

	"veza-backend-api/internal/models"

	"github.com/google/uuid"
	"go.uber.org/zap"
)

var mentionRegex = regexp.MustCompile(`@(\w+)`)

func (h *MessageHandler) HandleSendMessage(ctx context.Context, client *Client, msg *IncomingMessage) {
	if msg.ConversationID == nil {
		client.SendJSON(NewErrorResponse("conversation_id is required"))
		return
	}
	if msg.Content == "" {
		client.SendJSON(NewErrorResponse("content is required"))
		return
	}

	// F474: live chat rate limit 1 msg/3s when conversation is a live stream room
	action := "send_message"
	if h.permissions.IsLiveRoom(ctx, *msg.ConversationID) {
		action = "send_live_message"
	}
	if !h.rateLimiter.Allow(client.UserID, action) {
		client.SendJSON(NewErrorResponse("rate limit exceeded"))
		return
	}

	if !h.permissions.CanSend(ctx, client.UserID, *msg.ConversationID) {
		client.SendJSON(NewErrorResponse("not allowed to send messages in this conversation"))
		return
	}

	md := make(map[string]interface{})
	if len(msg.Attachments) > 0 {
		md["attachments"] = msg.Attachments
	}
	var mentionIDs []string
	if h.userRepo != nil {
		matches := mentionRegex.FindAllStringSubmatch(msg.Content, -1)
		seen := make(map[string]bool)
		for _, m := range matches {
			if len(m) < 2 || seen[m[1]] {
				continue
			}
			username := strings.TrimSpace(m[1])
			if username == "" {
				continue
			}
			u, err := h.userRepo.GetUserByUsername(ctx, username)
			if err != nil || u == nil {
				continue
			}
			if u.ID != client.UserID && u.ID != uuid.Nil {
				mentionIDs = append(mentionIDs, u.ID.String())
				seen[m[1]] = true
			}
		}
		if len(mentionIDs) > 0 {
			md["mentions"] = mentionIDs
		}
	}
	var metadata []byte
	if len(md) > 0 {
		metadata, _ = json.Marshal(md)
	}

	chatMsg := &models.ChatMessage{
		ID:              uuid.New(),
		ConversationID:  *msg.ConversationID,
		SenderID:        client.UserID,
		Content:         msg.Content,
		MessageType:     "text",
		ParentMessageID: msg.ParentMessageID,
		ReplyToID:       msg.ParentMessageID, // DB column; same as parent for threading
		Status:          "sent",
		Metadata:        metadata,
		CreatedAt:       time.Now(),
		UpdatedAt:       time.Now(),
	}

	if err := h.msgRepo.Create(ctx, chatMsg); err != nil {
		h.logger.Error("Failed to save message",
			zap.Error(err),
			zap.String("user_id", client.UserID.String()))
		client.SendJSON(NewErrorResponse("failed to send message"))
		return
	}

	client.SendJSON(NewActionConfirmedResponse("message_sent", true))

	outgoing := NewNewMessageResponse(
		chatMsg.ConversationID,
		chatMsg.ID,
		chatMsg.SenderID,
		client.Username,
		chatMsg.Content,
		chatMsg.CreatedAt,
		msg.Attachments,
		chatMsg.ParentMessageID,
	)

	data, _ := json.Marshal(outgoing)
	h.hub.BroadcastToRoom(*msg.ConversationID, data, nil)

	if h.pubsub != nil {
		_ = h.pubsub.Publish(ctx, *msg.ConversationID, data)
	}

	// v0.9.6: Notify mentioned users
	for _, idStr := range mentionIDs {
		mentionedID, err := uuid.Parse(idStr)
		if err != nil {
			continue
		}
		mentionEvt := NewMentionedInMessageResponse(
			chatMsg.ConversationID,
			chatMsg.ID,
			client.UserID,
			chatMsg.Content,
		)
		mentionData, _ := json.Marshal(mentionEvt)
		h.hub.SendToUser(mentionedID, mentionData)
	}
}

func (h *MessageHandler) HandleEditMessage(ctx context.Context, client *Client, msg *IncomingMessage) {
	if msg.MessageID == nil || msg.ConversationID == nil {
		client.SendJSON(NewErrorResponse("message_id and conversation_id are required"))
		return
	}
	if msg.NewContent == "" {
		client.SendJSON(NewErrorResponse("new_content is required"))
		return
	}

	chatMsg, err := h.msgRepo.GetByID(ctx, *msg.MessageID)
	if err != nil {
		client.SendJSON(NewErrorResponse("message not found"))
		return
	}

	if chatMsg.SenderID != client.UserID {
		client.SendJSON(NewErrorResponse("can only edit your own messages"))
		return
	}

	now := time.Now()
	chatMsg.Content = msg.NewContent
	chatMsg.IsEdited = true
	chatMsg.EditedAt = &now

	if err := h.msgRepo.Update(ctx, chatMsg); err != nil {
		h.logger.Error("Failed to update message", zap.Error(err))
		client.SendJSON(NewErrorResponse("failed to edit message"))
		return
	}

	client.SendJSON(NewActionConfirmedResponse("message_edited", true))

	outgoing := NewMessageEditedResponse(
		chatMsg.ID,
		chatMsg.ConversationID,
		client.UserID,
		now,
		msg.NewContent,
	)

	data, _ := json.Marshal(outgoing)
	h.hub.BroadcastToRoom(*msg.ConversationID, data, nil)

	if h.pubsub != nil {
		_ = h.pubsub.Publish(ctx, *msg.ConversationID, data)
	}
}

func (h *MessageHandler) HandleDeleteMessage(ctx context.Context, client *Client, msg *IncomingMessage) {
	if msg.MessageID == nil || msg.ConversationID == nil {
		client.SendJSON(NewErrorResponse("message_id and conversation_id are required"))
		return
	}

	chatMsg, err := h.msgRepo.GetByID(ctx, *msg.MessageID)
	if err != nil {
		client.SendJSON(NewErrorResponse("message not found"))
		return
	}

	isModerator := h.permissions.CanModerate(ctx, client.UserID, *msg.ConversationID)
	if chatMsg.SenderID != client.UserID && !isModerator {
		client.SendJSON(NewErrorResponse("can only delete your own messages"))
		return
	}

	if err := h.msgRepo.SoftDelete(ctx, *msg.MessageID); err != nil {
		h.logger.Error("Failed to delete message", zap.Error(err))
		client.SendJSON(NewErrorResponse("failed to delete message"))
		return
	}

	client.SendJSON(NewActionConfirmedResponse("message_deleted", true))

	outgoing := NewMessageDeletedResponse(
		*msg.MessageID,
		*msg.ConversationID,
		client.UserID,
		time.Now(),
	)

	data, _ := json.Marshal(outgoing)
	h.hub.BroadcastToRoom(*msg.ConversationID, data, nil)

	if h.pubsub != nil {
		_ = h.pubsub.Publish(ctx, *msg.ConversationID, data)
	}
}