import { net } from 'electron'
import { Readable } from 'node:stream'
import { byteStringResponseHeaders } from './response-headers.js'

export const fetchNetwork: typeof fetch = async (input, init) => {
  const request = new Request(input, init)
  if (request.redirect !== 'manual') return net.fetch(request)
  if (request.method !== 'GET') throw new Error('Ручные переходы доступны только для загрузки файлов')
  // net.fetch rejects manual redirects before it can return their status and headers.
  return new Promise<Response>((resolve, reject) => {
    const client = net.request({
      url: request.url,
      method: 'GET',
      redirect: 'manual',
      credentials: request.credentials,
    })
    let body: Readable | null = null
    const cleanup = () => request.signal.removeEventListener('abort', abort)
    const fail = (error: unknown) => {
      cleanup()
      reject(error)
      client.abort()
    }
    const abort = () => {
      const error = request.signal.reason
      body?.destroy(error instanceof Error ? error : new Error('Загрузка отменена'))
      fail(error)
    }
    const headersOf = (values: Record<string, string | string[]>) => {
      const headers = new Headers()
      for (const [name, entries] of Object.entries(byteStringResponseHeaders(values)))
        for (const value of entries) headers.append(name, value)
      return headers
    }
    client.on('error', fail)
    client.on('redirect', (status, _method, url, values) => {
      try {
        const headers = headersOf(values)
        headers.set('Location', new URL(url).href)
        resolve(new Response(null, { status, headers }))
        cleanup()
        client.abort()
      } catch (error) {
        fail(error)
      }
    })
    client.on('response', (response) => {
      try {
        body = response as unknown as Readable
        body.once('end', cleanup)
        body.once('close', () => {
          cleanup()
          if (!body!.readableEnded) client.abort()
        })
        const empty = [204, 205, 304].includes(response.statusCode)
        const stream = empty ? null : Readable.toWeb(body) as ReadableStream<Uint8Array>
        resolve(new Response(stream, {
          status: response.statusCode,
          headers: headersOf(response.headers),
        }))
        if (empty) body.resume()
      } catch (error) {
        fail(error)
      }
    })
    try {
      for (const [name, value] of request.headers) client.setHeader(name, value)
      request.signal.addEventListener('abort', abort, { once: true })
      if (request.signal.aborted) abort()
      else client.end()
    } catch (error) {
      fail(error)
    }
  })
}