/**
 * Import ChatGPT conversations from exported conversations.json file
 */

import { NextResponse } from 'next/server';
import { getAdminAuth, getAdminDb } from '@/lib/firebase/admin';

interface ChatGPTMessage {
  id: string;
  author: {
    role: string;
    name?: string;
  };
  content: {
    content_type: string;
    parts: string[];
  };
  create_time?: number;
  update_time?: number;
}

interface ChatGPTConversation {
  id: string;
  title: string;
  create_time: number;
  update_time?: number;
  mapping: Record<string, {
    id: string;
    message?: ChatGPTMessage;
    parent?: string;
    children: string[];
  }>;
}

export async function POST(request: Request) {
  try {
    // Authenticate user
    const authHeader = request.headers.get('Authorization');
    if (!authHeader?.startsWith('Bearer ')) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
    }

    const idToken = authHeader.split('Bearer ')[1];
    const adminAuth = getAdminAuth();
    const adminDb = getAdminDb();
    
    let userId: string;
    try {
      const decodedToken = await adminAuth.verifyIdToken(idToken);
      userId = decodedToken.uid;
    } catch (error) {
      return NextResponse.json({ error: 'Invalid token' }, { status: 401 });
    }

    const body = await request.json();
    const { conversations, projectId } = body;

    if (!conversations || !Array.isArray(conversations)) {
      return NextResponse.json({ error: 'Invalid conversations data' }, { status: 400 });
    }

    console.log(`[ChatGPT Import] Processing ${conversations.length} conversations for user ${userId}`);

    const importedConversations: Array<{ id: string; title: string; messageCount: number }> = [];
    const batch = adminDb.batch();
    let batchCount = 0;

    for (const conv of conversations) {
      try {
        const conversation = conv as ChatGPTConversation;
        
        // Extract messages from mapping
        const messages: Array<{
          role: string;
          content: string;
          timestamp?: number;
        }> = [];

        // Find the root and traverse the conversation tree
        for (const [key, node] of Object.entries(conversation.mapping)) {
          if (node.message && node.message.author.role !== 'system') {
            const content = node.message.content.parts.join('\n');
            if (content.trim()) {
              messages.push({
                role: node.message.author.role,
                content: content,
                timestamp: node.message.create_time,
              });
            }
          }
        }

        // Sort messages by timestamp (if available) or keep order
        messages.sort((a, b) => {
          if (a.timestamp && b.timestamp) {
            return a.timestamp - b.timestamp;
          }
          return 0;
        });

        // Store in Firestore
        const importRef = adminDb.collection('chatgptImports').doc();
        const importData = {
          userId,
          projectId: projectId || null,
          conversationId: conversation.id,
          title: conversation.title || 'Untitled Conversation',
          messageCount: messages.length,
          messages,
          createdAt: conversation.create_time 
            ? new Date(conversation.create_time * 1000).toISOString()
            : new Date().toISOString(),
          importedAt: new Date().toISOString(),
        };

        batch.set(importRef, importData);
        batchCount++;

        importedConversations.push({
          id: conversation.id,
          title: conversation.title,
          messageCount: messages.length,
        });

        // Firestore batch limit is 500 operations
        if (batchCount >= 500) {
          await batch.commit();
          batchCount = 0;
        }
      } catch (error) {
        console.error(`[ChatGPT Import] Error processing conversation ${conv.id}:`, error);
        // Continue with other conversations
      }
    }

    // Commit remaining batch
    if (batchCount > 0) {
      await batch.commit();
    }

    console.log(`[ChatGPT Import] Successfully imported ${importedConversations.length} conversations`);

    return NextResponse.json({
      success: true,
      imported: importedConversations.length,
      conversations: importedConversations,
    });
  } catch (error) {
    console.error('[ChatGPT Import] Error:', error);
    return NextResponse.json(
      {
        error: 'Failed to import conversations',
        details: error instanceof Error ? error.message : String(error),
      },
      { status: 500 }
    );
  }
}