import { NextResponse } from 'next/server';
import { getServerSession } from 'next-auth';
import { authOptions } from "@/app/api/auth/options";
import { getEmailContent, shouldUseGraphAPI } from '@/lib/services/email-service';
import { logger } from '@/lib/logger';

/**
 * Route API pour télécharger une pièce jointe d'un email
 * GET /api/courrier/[id]/attachment/[attachmentIndex]
 */
export async function GET(
  request: Request,
  context: { params: Promise<{ id: string; attachmentIndex: string }> }
) {
  try {
    const params = await context.params;
    const { id: emailId, attachmentIndex } = params;
    
    // Authenticate user
    const session = await getServerSession(authOptions);
    if (!session || !session.user?.id) {
      return NextResponse.json(
        { error: "Not authenticated" },
        { status: 401 }
      );
    }

    // Validate parameters
    if (!emailId || !attachmentIndex) {
      return NextResponse.json(
        { error: "Missing email ID or attachment index" },
        { status: 400 }
      );
    }

    const attachmentIdx = parseInt(attachmentIndex, 10);
    if (isNaN(attachmentIdx) || attachmentIdx < 0) {
      return NextResponse.json(
        { error: "Invalid attachment index" },
        { status: 400 }
      );
    }

    // Get query parameters
    const { searchParams } = new URL(request.url);
    const folder = searchParams.get("folder") || "INBOX";
    const accountId = searchParams.get("accountId") || undefined;

    logger.debug('[ATTACHMENT] Fetching attachment', {
      userIdHash: Buffer.from(session.user.id).toString('base64').slice(0, 12),
      emailId,
      attachmentIndex: attachmentIdx,
      folder,
      accountIdHash: accountId ? Buffer.from(accountId).toString('base64').slice(0, 12) : 'default',
    });

    // Check if this is a Microsoft Graph account
    const graphCheck = await shouldUseGraphAPI(session.user.id, accountId);
    
    let attachmentBuffer: Buffer;
    let contentType: string;
    let filename: string;
    
    if (graphCheck.useGraph && graphCheck.mailCredentialId) {
      // Use Microsoft Graph API to fetch attachment
      logger.debug('[ATTACHMENT] Fetching attachment via Microsoft Graph API', {
        emailId,
        attachmentIndex: attachmentIdx,
        mailCredentialIdHash: graphCheck.mailCredentialId ? Buffer.from(graphCheck.mailCredentialId).toString('base64').slice(0, 12) : null,
      });
      
      try {
        // First, get the email to find the attachment ID
        const email = await getEmailContent(session.user.id, emailId, folder, accountId);
        
        if (!email.attachments || email.attachments.length === 0) {
          return NextResponse.json(
            { error: "Email has no attachments" },
            { status: 404 }
          );
        }
        
        if (attachmentIdx >= email.attachments.length) {
          return NextResponse.json(
            { error: "Attachment index out of range" },
            { status: 404 }
          );
        }
        
        // For Graph API, we need to fetch the attachment separately
        // The attachment should have an ID or we need to fetch it from the message
        const attachment = email.attachments[attachmentIdx];
        filename = attachment.filename || `attachment-${attachmentIdx}`;
        contentType = attachment.contentType || 'application/octet-stream';
        
        // If attachment has content (from cache), use it
        if (attachment.content) {
          attachmentBuffer = Buffer.from(attachment.content, 'base64');
        } else {
          // Need to fetch from Graph API - try to get attachment ID from email metadata
          // First, re-fetch the email to get attachment IDs if available
          logger.debug('[ATTACHMENT] Attachment content not cached, fetching from Graph API', {
            emailId,
            attachmentIndex: attachmentIdx,
            mailCredentialIdHash: graphCheck.mailCredentialId ? Buffer.from(graphCheck.mailCredentialId).toString('base64').slice(0, 12) : null,
          });
          
          try {
            // Re-fetch the email with full attachment data
            const { fetchGraphEmail, fetchGraphAttachment } = await import('@/lib/services/microsoft-graph-mail');
            const graphMessage = await fetchGraphEmail(graphCheck.mailCredentialId, emailId);
            
            if (!graphMessage.attachments || attachmentIdx >= graphMessage.attachments.length) {
              return NextResponse.json(
                { error: "Attachment not found" },
                { status: 404 }
              );
            }
            
            const graphAttachment = graphMessage.attachments[attachmentIdx];
            
            // If still no contentBytes, try fetching by attachment ID
            if (!graphAttachment.contentBytes && graphAttachment.id) {
              const attachmentData = await fetchGraphAttachment(
                graphCheck.mailCredentialId,
                emailId,
                graphAttachment.id
              );
              attachmentBuffer = Buffer.from(attachmentData.contentBytes, 'base64');
            } else if (graphAttachment.contentBytes) {
              attachmentBuffer = Buffer.from(graphAttachment.contentBytes, 'base64');
            } else {
              logger.error('[ATTACHMENT] Graph API attachment has no content and no ID', {
                emailId,
                attachmentIndex: attachmentIdx,
              });
              return NextResponse.json(
                { error: "Attachment content not available" },
                { status: 404 }
              );
            }
          } catch (fetchError) {
            logger.error('[ATTACHMENT] Error fetching attachment from Graph API', {
              emailId,
              attachmentIndex: attachmentIdx,
              error: fetchError instanceof Error ? fetchError.message : String(fetchError),
            });
            return NextResponse.json(
              { error: "Failed to fetch attachment from Microsoft Graph API" },
              { status: 500 }
            );
          }
        }
      } catch (error) {
        logger.error('[ATTACHMENT] Error fetching Graph API attachment', {
          emailId,
          attachmentIndex: attachmentIdx,
          error: error instanceof Error ? error.message : String(error),
        });
        return NextResponse.json(
          { error: "Failed to fetch attachment from Microsoft Graph API" },
          { status: 500 }
        );
      }
    } else {
      // Use IMAP (standard flow)
      // Fetch the email content (which includes attachments)
      const email = await getEmailContent(session.user.id, emailId, folder, accountId);

      // Check if email has attachments
      if (!email.attachments || email.attachments.length === 0) {
        return NextResponse.json(
          { error: "Email has no attachments" },
          { status: 404 }
        );
      }

      // Check if attachment index is valid
      if (attachmentIdx >= email.attachments.length) {
        return NextResponse.json(
          { error: "Attachment index out of range" },
          { status: 404 }
        );
      }

      const attachment = email.attachments[attachmentIdx];
      filename = attachment.filename || `attachment-${attachmentIdx}`;
      contentType = attachment.contentType || 'application/octet-stream';

      // Check if attachment has content
      if (!attachment.content) {
        logger.error('[ATTACHMENT] Attachment has no content', {
          emailId,
          attachmentIndex: attachmentIdx,
          filename: attachment.filename,
        });
        return NextResponse.json(
          { error: "Attachment content not available" },
          { status: 404 }
        );
      }

      // Decode base64 content
      try {
        attachmentBuffer = Buffer.from(attachment.content, 'base64');
      } catch (error) {
        logger.error('[ATTACHMENT] Error decoding base64 content', {
          emailId,
          attachmentIndex: attachmentIdx,
          error: error instanceof Error ? error.message : String(error),
        });
        return NextResponse.json(
          { error: "Failed to decode attachment content" },
          { status: 500 }
        );
      }
    }

    // Get filename, sanitize it for safe download
    const sanitizedFilename = filename.replace(/[^a-zA-Z0-9._-]/g, '_');

    logger.debug('[ATTACHMENT] Serving attachment', {
      emailId,
      attachmentIndex: attachmentIdx,
      filename: sanitizedFilename,
      contentType,
      size: attachmentBuffer.length,
    });

    // Return the attachment as a downloadable file
    return new NextResponse(attachmentBuffer, {
      status: 200,
      headers: {
        'Content-Type': contentType,
        'Content-Disposition': `attachment; filename="${sanitizedFilename}"`,
        'Content-Length': attachmentBuffer.length.toString(),
        'Cache-Control': 'private, max-age=3600', // Cache for 1 hour
      },
    });
  } catch (error) {
    logger.error('[ATTACHMENT] Error fetching attachment', {
      error: error instanceof Error ? error.message : String(error),
    });
    return NextResponse.json(
      { error: "Failed to fetch attachment", message: error instanceof Error ? error.message : 'Unknown error' },
      { status: 500 }
    );
  }
}