import * as fs from 'fs'
import { NextConfig } from 'next'
import type { PageMapCache } from 'nextra/dist/page-map.mjs'
import * as path from 'path'
import { Configuration } from 'webpack'
import { PagesMetadata } from '../shared/lib/PagesMetadata'
import { LoadedUnbodyConfig } from './types'
import { setupThemeConfig } from './utils/setupThemeConfig'

const findNextraLoaders = (config: Configuration) => {
  return (config.module?.rules || []).filter(
    (rule) =>
      typeof rule === 'object' &&
      'use' in rule! &&
      Array.isArray(rule.use) &&
      typeof rule.use[1] === 'object' &&
      rule.use[1]?.loader === 'nextra/loader' &&
      rule.use[1].options &&
      !(rule.use[1].options as any)?.isMetaImport,
  )
}

export const extendWebpackConfig = async ({
  config,
  nextConfig,
}: {
  config: LoadedUnbodyConfig
  nextConfig: NextConfig
}) => {
  let replacedThemeConfig = false

  let pageMapCache: PageMapCache = null as any

  return (webpackConfig: Configuration, options: any): Configuration => {
    const newConfig = nextConfig.webpack!(
      webpackConfig,
      options,
    ) as Configuration

    const nextraLoaders = findNextraLoaders(newConfig)
    const loaderOptions = (nextraLoaders[0] as any).use[1].options as Record<
      string,
      any
    >

    pageMapCache = loaderOptions.pageMapCache

    if (config.setupComponents && !replacedThemeConfig) {
      const themeConfig = loaderOptions.themeConfig

      if (!themeConfig)
        throw new Error(
          'themeConfig is not set in your nextra config. Please make sure you either have a themeConfig or disable the component injection by setting "setupComponents" to false.',
        )

      const newPath = setupThemeConfig({
        config,
        originalPath: require.resolve(themeConfig, {
          paths: [config.projectDir],
        }),
      })

      nextraLoaders.forEach((loader) => {
        ;(loader as any).use[1].options.themeConfig = newPath
        replacedThemeConfig = true
      })
    }

    newConfig.plugins!.push({
      apply: (compiler) => {
        compiler.hooks.afterCompile.tap('UnbodySearch', (compilation) => {
          const pages = pageMapCache.get()?.items || []
          const pagesMetadata = PagesMetadata.fromPageMap(pages)
          const json = pagesMetadata.toJson()
          fs.writeFileSync(
            path.join(config.dir, 'pages-metadata.json'),
            JSON.stringify(json, null, 2),
          )
        })
      },
    })

    return newConfig
  }
}