// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

package app

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
	"github.com/mattermost/mattermost/server/public/shared/request"
)

// summarizePostsJSONSchema is the structured output schema for the LLM summarization response.
// Defined at package level to avoid re-allocating on every call.
var summarizePostsJSONSchema = map[string]any{
	"type": "object",
	"properties": map[string]any{
		"highlights": map[string]any{
			"type":        "array",
			"items":       map[string]any{"type": "string"},
			"description": "Key discussion points, decisions, or important information",
		},
		"action_items": map[string]any{
			"type":        "array",
			"items":       map[string]any{"type": "string"},
			"description": "Tasks, todos, or action items mentioned",
		},
	},
	"required":             []any{"highlights", "action_items"},
	"additionalProperties": false,
}

// SummarizePosts generates an AI summary of posts with highlights and action items
func (a *App) SummarizePosts(rctx request.CTX, userID string, posts []*model.Post, channelName, teamName string, agentID string) (*model.AIRecapSummaryResponse, *model.AppError) {
	if len(posts) == 0 {
		return &model.AIRecapSummaryResponse{Highlights: []string{}, ActionItems: []string{}}, nil
	}

	// Get site URL for permalink generation
	siteURL := a.GetSiteURL()

	// Build conversation context from posts and collect post IDs
	conversationText, postIDs := buildConversationTextWithIDs(posts)

	systemPrompt := "You are an expert at analyzing team conversations and extracting key information. Your task is to summarize a conversation from a Mattermost channel, identifying the most important highlights and any actionable items. Return ONLY valid JSON with 'highlights' and 'action_items' keys, each containing an array of strings. If there are no highlights or action items, return empty arrays. Do not make up information - only include items explicitly mentioned in the conversation."

	userPrompt := fmt.Sprintf(`Analyze the following conversation from the "%s" channel and provide a summary.

Site URL: %s
Team Name: %s

Conversation:
%s

Available Post IDs: %s

Return a JSON object with:
- "highlights": array of key discussion points, decisions, or important information
- "action_items": array of tasks, todos, or action items mentioned

IMPORTANT INSTRUCTIONS:
1. When your summary includes a user's username, prepend an @ symbol to the username. For example if you return a highlight with text '<username> sent an update about project xyz', where <username> is 'john.smith', you should phrase is as '@john.smith sent an update about project xyz'.

2. For EACH highlight and action item, you MUST append a permalink to cite the source. The permalink should reference the most relevant post from the conversation. Format the permalink at the END of each item as: [PERMALINK:%s/%s/pl/<POST_ID>] where <POST_ID> is one of the available post IDs provided above. Choose the post ID that is most relevant to that specific highlight or action item.

Example format: "Team decided to migrate to microservices architecture [PERMALINK:%s/%s/pl/abc123xyz]"

Your response must be compacted valid JSON only, with no additional text, formatting, nor code blocks.`, channelName, siteURL, teamName, conversationText, strings.Join(postIDs, ", "), siteURL, teamName, siteURL, teamName)

	// Create bridge client
	sessionUserID := ""
	if session := rctx.Session(); session != nil {
		sessionUserID = session.UserId
	}
	requestUserID := userID
	if sessionUserID != "" {
		requestUserID = sessionUserID
	}
	completionRequest := BridgeCompletionRequest{
		Operation:       BridgeOperationRecapSummary,
		ClientOperation: "recaps",
		Messages: []BridgeMessage{
			{Role: "system", Message: systemPrompt},
			{Role: "user", Message: userPrompt},
		},
		JSONOutputFormat: summarizePostsJSONSchema,
		OperationSubType: "summarize_channel",
		UserID:           requestUserID,
		ChannelID:        posts[0].ChannelId,
	}

	rctx.Logger().Debug("Calling AI agent for post summarization",
		mlog.String("channel_name", channelName),
		mlog.String("user_id", userID),
		mlog.String("agent_id", agentID),
		mlog.Int("post_count", len(posts)),
	)

	completion, err := a.ch.agentsBridge.AgentCompletion(sessionUserID, agentID, completionRequest)
	if err != nil {
		return nil, model.NewAppError("SummarizePosts", "app.ai.summarize.agent_call_failed", nil, err.Error(), http.StatusInternalServerError)
	}

	var summary model.AIRecapSummaryResponse
	if err := json.Unmarshal([]byte(completion), &summary); err != nil {
		return nil, model.NewAppError("SummarizePosts", "app.ai.summarize.parse_failed", nil, err.Error(), http.StatusInternalServerError)
	}

	// Ensure arrays are never nil
	if summary.Highlights == nil {
		summary.Highlights = []string{}
	}
	if summary.ActionItems == nil {
		summary.ActionItems = []string{}
	}

	rctx.Logger().Debug("AI summarization successful",
		mlog.String("channel_name", channelName),
		mlog.Int("highlights_count", len(summary.Highlights)),
		mlog.Int("action_items_count", len(summary.ActionItems)),
	)

	return &summary, nil
}

func buildConversationTextWithIDs(posts []*model.Post) (string, []string) {
	var sb strings.Builder
	postIDs := make([]string, 0, len(posts))

	for _, post := range posts {
		// Collect post ID
		postIDs = append(postIDs, post.Id)

		// Posts should have Username populated by the caller
		// For posts without username, use UserId as fallback
		username := ""
		if usernameProp := post.GetProp("username"); usernameProp != nil {
			if usernameStr, ok := usernameProp.(string); ok {
				username = usernameStr
			}
		}
		if username == "" {
			username = post.UserId
		}
		sb.WriteString(fmt.Sprintf("[%s] %s (Post ID: %s): %s\n",
			time.UnixMilli(post.CreateAt).Format("15:04"),
			username,
			post.Id,
			post.Message))
	}
	return sb.String(), postIDs
}