import { VITE_ENVIRONMENT_NAMES } from '../constants'
import { prerender } from '../prerender'
import type { PrerenderHandler } from '../prerender'
import type { TanStackStartOutputConfig } from '../schema'
import type { PreviewServer, ResolvedConfig, ViteBuilder } from 'vite'

export async function prerenderWithVite({
  startConfig,
  builder,
}: {
  startConfig: TanStackStartOutputConfig
  builder: ViteBuilder
}) {
  const serverEnv = builder.environments[VITE_ENVIRONMENT_NAMES.server]

  if (!serverEnv) {
    throw new Error(
      `Vite's "${VITE_ENVIRONMENT_NAMES.server}" environment not found`,
    )
  }

  const clientEnv = builder.environments[VITE_ENVIRONMENT_NAMES.client]
  if (!clientEnv) {
    throw new Error(
      `Vite's "${VITE_ENVIRONMENT_NAMES.client}" environment not found`,
    )
  }

  const outputDir = clientEnv.config.build.outDir

  process.env.TSS_PRERENDERING = 'true'
  process.env.TSS_CLIENT_OUTPUT_DIR = outputDir

  const previewServer = await startPreviewServer(serverEnv.config)
  const baseUrl = getResolvedUrl(previewServer)

  const handler: PrerenderHandler = {
    getClientOutputDirectory() {
      return outputDir
    },
    getOrigin() {
      return baseUrl.origin
    },
    request(path, options) {
      const url = new URL(path, baseUrl)
      if (url.origin !== baseUrl.origin) {
        throw new Error(`Prerender request URL must be relative: ${path}`)
      }
      return fetch(new Request(url, options))
    },
    close() {
      return previewServer.close()
    },
  }

  return prerender({
    startConfig,
    handler,
  })
}

async function startPreviewServer(
  viteConfig: ResolvedConfig,
): Promise<PreviewServer> {
  const vite = await import('vite')

  try {
    return await vite.preview({
      configFile: viteConfig.configFile,
      preview: {
        port: 0,
        open: false,
      },
    })
  } catch (error) {
    throw new Error(
      'Failed to start the Vite preview server for prerendering',
      {
        cause: error,
      },
    )
  }
}

function getResolvedUrl(previewServer: PreviewServer): URL {
  const baseUrl = previewServer.resolvedUrls?.local[0]

  if (!baseUrl) {
    throw new Error('No resolved URL is available from the Vite preview server')
  }

  return new URL(baseUrl)
}