import { NextApiRequest, NextApiResponse } from 'next'
import { IncomingForm, File as FormidableFile } from 'formidable'
import FormData from 'form-data'
import fs from 'fs'
import https from 'https'
import http from 'http'
import { URL } from 'url'

const MAX_FILE_SIZE = 50 * 1024 * 1024 // 50MB

export const config = {
  api: {
    bodyParser: false, // Disable bodyParser to handle multipart
  },
}

interface ParseResult {
  fields: Record<string, string[]>
  files: Record<string, FormidableFile[]>
}

export default async function handler(req: NextApiRequest, res: NextApiResponse) {
  if (req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' })
  }

  // Get target endpoint from query or use default
  const targetEndpoint = (req.query.endpoint as string) || 'https://void.cat/upload'

  try {
    // Parse multipart form data
    // formidable needs the raw Node.js IncomingMessage, which NextApiRequest extends
    const form = new IncomingForm({
      maxFileSize: MAX_FILE_SIZE,
      keepExtensions: true,
    })

    const parseResult = await new Promise<ParseResult>((resolve, reject) => {
      // Cast req to any to work with formidable - NextApiRequest extends IncomingMessage
      form.parse(req as any, (err, fields, files) => {
        if (err) {
          console.error('Formidable parse error:', err)
          reject(err)
        } else {
          resolve({ fields: fields as Record<string, string[]>, files: files as Record<string, FormidableFile[]> })
        }
      })
    })

    const { files } = parseResult

    // Get the file from the parsed form
    const fileField = files.file?.[0]
    if (!fileField) {
      return res.status(400).json({ error: 'No file provided' })
    }

    // Forward to target endpoint using https/http native modules
    // Support redirects (301, 302, 307, 308)
    const currentUrl = new URL(targetEndpoint)
    const MAX_REDIRECTS = 5

    let response: { statusCode: number; statusMessage: string; body: string }
    try {
      response = await new Promise<{ statusCode: number; statusMessage: string; body: string }>((resolve, reject) => {
        function makeRequest(url: URL, redirectCount: number, fileField: FormidableFile): void {
          if (redirectCount > MAX_REDIRECTS) {
            reject(new Error(`Too many redirects (max ${MAX_REDIRECTS})`))
            return
          }

          // Recreate FormData for each request (needed for redirects)
          const requestFormData = new FormData()
          const fileStream = fs.createReadStream(fileField.filepath)
          requestFormData.append('file', fileStream, {
            filename: fileField.originalFilename || fileField.newFilename || 'upload',
            contentType: fileField.mimetype || 'application/octet-stream',
          })

          const isHttps = url.protocol === 'https:'
          const clientModule = isHttps ? https : http
          const headers = requestFormData.getHeaders()
          const requestOptions = {
            hostname: url.hostname,
            port: url.port || (isHttps ? 443 : 80),
            path: url.pathname + url.search,
            method: 'POST',
            headers: headers,
            timeout: 30000, // 30 seconds timeout
          }

          const proxyRequest = clientModule.request(requestOptions, (proxyResponse) => {
            // Handle redirects (301, 302, 307, 308)
            const statusCode = proxyResponse.statusCode || 500
            if ((statusCode === 301 || statusCode === 302 || statusCode === 307 || statusCode === 308) && proxyResponse.headers.location) {
              const location = proxyResponse.headers.location
              let redirectUrl: URL
              try {
                // Handle relative and absolute URLs
                redirectUrl = new URL(location, url.toString())
                console.log('NIP-95 proxy redirect:', {
                  from: url.toString(),
                  to: redirectUrl.toString(),
                  statusCode,
                  redirectCount: redirectCount + 1,
                })
                // Drain the response before redirecting
                proxyResponse.resume()
                // Make new request to redirect location
                makeRequest(redirectUrl, redirectCount + 1, fileField)
                return
              } catch (urlError) {
                console.error('NIP-95 proxy invalid redirect URL:', {
                  location,
                  error: urlError instanceof Error ? urlError.message : 'Unknown error',
                })
                reject(new Error(`Invalid redirect URL: ${location}`))
                return
              }
            }

            let body = ''
            proxyResponse.setEncoding('utf8')
            proxyResponse.on('data', (chunk) => {
              body += chunk
            })
            proxyResponse.on('end', () => {
              resolve({
                statusCode: statusCode,
                statusMessage: proxyResponse.statusMessage || 'Internal Server Error',
                body: body,
              })
            })
            proxyResponse.on('error', (error) => {
              reject(error)
            })
          })

          // Set timeout on the request
          proxyRequest.setTimeout(30000, () => {
            proxyRequest.destroy()
            reject(new Error('Request timeout after 30 seconds'))
          })

          proxyRequest.on('error', (error) => {
            // Check for DNS errors specifically
            const errorCode = (error as NodeJS.ErrnoException).code
            if (errorCode === 'ENOTFOUND' || errorCode === 'EAI_AGAIN') {
              console.error('NIP-95 proxy DNS error:', {
                targetEndpoint,
                hostname: url.hostname,
                errorCode,
                errorMessage: error.message,
                suggestion: 'Check DNS resolution or network connectivity on the server',
              })
              reject(new Error(`DNS resolution failed for ${url.hostname}: ${error.message}`))
            } else {
              reject(error)
            }
          })

          requestFormData.on('error', (error) => {
            reject(error)
          })

          requestFormData.pipe(proxyRequest)
        }

        makeRequest(currentUrl, 0, fileField)
      })
    } catch (requestError) {
      // Clean up temporary file before returning error
      try {
        fs.unlinkSync(fileField.filepath)
      } catch (unlinkError) {
        console.error('Error deleting temp file:', unlinkError)
      }
      const errorMessage = requestError instanceof Error ? requestError.message : 'Unknown request error'
      const isDnsError = errorMessage.includes('DNS resolution failed') || errorMessage.includes('ENOTFOUND') || errorMessage.includes('EAI_AGAIN')

      console.error('NIP-95 proxy request error:', {
        targetEndpoint,
        hostname: currentUrl.hostname,
        error: errorMessage,
        isDnsError,
        fileSize: fileField.size,
        fileName: fileField.originalFilename,
        suggestion: isDnsError ? 'The server cannot resolve the domain name. Check DNS configuration and network connectivity.' : undefined,
      })

      // Return a more specific error message for DNS issues
      if (isDnsError) {
        return res.status(500).json({
          error: `DNS resolution failed for ${currentUrl.hostname}. The server cannot resolve the domain name. Please check DNS configuration and network connectivity.`,
        })
      }

      return res.status(500).json({
        error: `Failed to connect to upload endpoint: ${errorMessage}`,
      })
    }

    // Clean up temporary file
    try {
      fs.unlinkSync(fileField.filepath)
    } catch (unlinkError) {
      console.error('Error deleting temp file:', unlinkError)
    }

    if (response.statusCode < 200 || response.statusCode >= 300) {
      const errorText = response.body.substring(0, 200) // Limit log size
      console.error('NIP-95 proxy response error:', {
        targetEndpoint,
        finalUrl: currentUrl.toString(),
        status: response.statusCode,
        statusText: response.statusMessage,
        errorText: errorText,
      })

      // Provide more specific error messages for common HTTP status codes
      let userFriendlyError = errorText || `Upload failed: ${response.statusCode} ${response.statusMessage}`
      if (response.statusCode === 401) {
        userFriendlyError = 'Authentication required. This endpoint requires authorization headers.'
      } else if (response.statusCode === 403) {
        userFriendlyError = 'Access forbidden. This endpoint may require authentication or have restrictions.'
      } else if (response.statusCode === 405) {
        userFriendlyError = 'Method not allowed. This endpoint may not support POST requests or the URL may be incorrect.'
      } else if (response.statusCode === 413) {
        userFriendlyError = 'File too large. The file exceeds the maximum size allowed by this endpoint.'
      } else if (response.statusCode >= 500) {
        userFriendlyError = `Server error (${response.statusCode}). The endpoint server encountered an error.`
      }

      return res.status(response.statusCode).json({
        error: userFriendlyError,
      })
    }

    let result: unknown
    try {
      result = JSON.parse(response.body)
    } catch (parseError) {
      const errorMessage = parseError instanceof Error ? parseError.message : 'Invalid JSON response'
      console.error('NIP-95 proxy JSON parse error:', {
        targetEndpoint,
        error: errorMessage,
        bodyPreview: response.body.substring(0, 100),
      })
      return res.status(500).json({
        error: `Invalid upload response: ${errorMessage}`,
      })
    }

    return res.status(200).json(result)
  } catch (error) {
    console.error('NIP-95 proxy error:', error)
    return res.status(500).json({
      error: error instanceof Error ? error.message : 'Internal server error',
    })
  }
}