import { defineConfig, type HtmlTagDescriptor, type Plugin } from 'vite'
import react from '@vitejs/plugin-react'
import tailwindcss from '@tailwindcss/vite'
import path from 'node:path'

import siteConfiguration from './site.json'

// https://vitejs.dev/config/
export default defineConfig({
  plugins: [
    react(),
    tailwindcss(),
    siteConfigurationPlugin(siteConfiguration),
  ],
  resolve: {
    alias: {
      '@': path.resolve(__dirname, './src'),
    },
  },
})

type SiteConfiguration = {
  title?: string
  description?: string
  language?: string
  robots?: { index?: boolean }
  icons?: { icon?: string }
  openGraph?: { image?: string }
  analytics?: { googleAnalyticsId?: string }
  customScripts?: {
    headStart?: string
    headEnd?: string
    bodyStart?: string
    bodyEnd?: string
  }
  accessibility?: { addBypassLinks?: boolean }
}

/** Applies /site.json to the generated document shell. */
function siteConfigurationPlugin(config: SiteConfiguration): Plugin {
  function sanitizeHtmlValue(value: string | undefined): string {
    return value?.replace(/[^a-zA-Z0-9_-]/g, '') || ''
  }
  function escapeHtmlText(value: string): string {
    return value.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
  }
  function replaceHtmlCommentSlot(html: string, slotName: string, content: string): string {
    return html.replace(`<!-- ${slotName} -->`, content)
  }

  const title = config.title ?? 'App'
  const description = config.description ?? ''
  const favicon = config.icons?.icon ?? ''
  const socialImage = config.openGraph?.image ?? ''
  const language = sanitizeHtmlValue(config.language) || 'en'
  const googleAnalyticsId = sanitizeHtmlValue(config.analytics?.googleAnalyticsId)
  const headStart = config.customScripts?.headStart ?? ''
  const headEnd = config.customScripts?.headEnd ?? ''
  const bodyStart = config.customScripts?.bodyStart ?? ''
  const bodyEnd = config.customScripts?.bodyEnd ?? ''
  const robotsTxt = config.robots?.index === false ? 'User-agent: *\nDisallow: /\n' : ''

  return {
    name: 'site-configuration',
    configureServer(server) {
      server.middlewares.use((req, res, next) => {
        if (!robotsTxt || req.url?.split('?')[0] !== '/robots.txt') return next()

        res.setHeader('Content-Type', 'text/plain; charset=utf-8')
        res.end(robotsTxt)
      })
    },
    generateBundle() {
      if (!robotsTxt) return

      this.emitFile({
        type: 'asset',
        fileName: 'robots.txt',
        source: robotsTxt,
      })
    },
    transformIndexHtml: {
      order: 'pre',
      handler(html) {
        let result = html
        result = replaceHtmlCommentSlot(result, 'site:lang', language)
        result = replaceHtmlCommentSlot(result, 'site:title', escapeHtmlText(title))
        result = replaceHtmlCommentSlot(result, 'site:head-start', headStart)
        result = replaceHtmlCommentSlot(result, 'site:head-end', headEnd)
        result = replaceHtmlCommentSlot(result, 'site:body-start', bodyStart)
        result = replaceHtmlCommentSlot(result, 'site:body-end', bodyEnd)

        const tags: HtmlTagDescriptor[] = []
        if (description) {
          tags.push({ tag: 'meta', attrs: { name: 'description', content: description }, injectTo: 'head' })
        }
        if (config.robots?.index === false) {
          tags.push({ tag: 'meta', attrs: { name: 'robots', content: 'noindex, nofollow' }, injectTo: 'head' })
        }
        if (favicon) {
          tags.push({ tag: 'link', attrs: { rel: 'icon', href: favicon }, injectTo: 'head' })
        }
        if (title) {
          tags.push({ tag: 'meta', attrs: { property: 'og:title', content: title }, injectTo: 'head' })
        }
        if (description) {
          tags.push({ tag: 'meta', attrs: { property: 'og:description', content: description }, injectTo: 'head' })
        }
        if (socialImage) {
          tags.push(
            { tag: 'meta', attrs: { property: 'og:image', content: socialImage }, injectTo: 'head' },
            { tag: 'meta', attrs: { name: 'twitter:card', content: 'summary_large_image' }, injectTo: 'head' },
            { tag: 'meta', attrs: { name: 'twitter:image', content: socialImage }, injectTo: 'head' },
          )
        }

        if (googleAnalyticsId) {
          tags.push(
            {
              tag: 'script',
              attrs: {
                async: true,
                src: `https://www.googletagmanager.com/gtag/js?id=${googleAnalyticsId}`,
              },
              injectTo: 'head',
            },
            {
              tag: 'script',
              children: `
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', ${JSON.stringify(googleAnalyticsId)});
`,
              injectTo: 'head',
            },
          )
        }

        if (config.accessibility?.addBypassLinks) {
          tags.push(
            {
              tag: 'style',
              children: `
  .bypass-link {
    position: fixed;
    top: 8px;
    left: 8px;
    z-index: 2147483647;
    transform: translateY(-150%);
    border-radius: 6px;
    background: #111827;
    color: #fff;
    padding: 8px 12px;
    font: 600 14px/1.2 system-ui, sans-serif;
    text-decoration: none;
  }
  .bypass-link:focus {
    transform: translateY(0);
  }
`,
              injectTo: 'head',
            },
            {
              tag: 'a',
              attrs: { class: 'bypass-link', href: '#root' },
              children: 'Skip to content',
              injectTo: 'body-prepend',
            },
          )
        }

        return { html: result, tags }
      },
    },
  }
}