import * as path from "node:path"
import { writeFile } from "node:fs/promises"
import { defineConfig } from "@rspress/core"
import type { RspressPlugin, SocialLink, UserConfig } from "@rspress/core"
import { pluginSitemap } from "@rspress/plugin-sitemap"
import { DOUYIN_ICON } from "./theme/lib/social-icons"

/**
 * Which deployment this build targets.
 *
 * The two builds differ in more than colour: `onixbyte.cn` is hosted in
 * mainland China, so its build points every absolute URL at the `.cn` origin
 * and omits links to sites that are not reliably reachable from there.
 *
 * Build with `pnpm build:com` / `pnpm build:cn` — see `package.json`. Both
 * write to `doc_build`, so run and deploy them one at a time.
 */
export type SiteTarget = "com" | "cn"

const ORIGINS: Record<SiteTarget, string> = {
  com: "https://onixbyte.com",
  cn: "https://onixbyte.cn",
}

/** Every locale the site is published in, default first for each target. */
const LANGS = ["en-gb", "zh-hans"] as const

/**
 * Locale served from the unprefixed routes.
 *
 * `.com` leads with English; `.cn` leads with Chinese, so a visitor landing on
 * the bare domain gets the language that site exists for. The other locale then
 * moves to a prefix — on `.cn`, English lives at `/en-gb/`.
 */
const DEFAULT_LANG: Record<SiteTarget, string> = {
  com: "en-gb",
  cn: "zh-hans",
}

/** hreflang and Open Graph locale codes, keyed by Rspress lang. */
const HREFLANG: Record<string, string> = { "en-gb": "en-GB", "zh-hans": "zh-Hans" }
const OG_LOCALE: Record<string, string> = { "en-gb": "en_GB", "zh-hans": "zh_CN" }

/** Language-switcher labels, keyed by Rspress lang. */
const LOCALE_LABELS: Record<string, string> = {
  "en-gb": "English (Great Britain)",
  "zh-hans": "简体中文",
}

/** Site title and description, keyed by Rspress lang. */
const LOCALE_META: Record<string, { title: string; description: string }> = {
  "en-gb": {
    title: "OnixByte",
    description:
      "OnixByte builds self-developed SaaS products and delivers custom software engineering services.",
  },
  "zh-hans": {
    title: "OnixByte",
    description: "曜珀科技自主研发 SaaS 产品，并提供定制化软件开发服务。",
  },
}

/**
 * Social links, split by whether they are reliably reachable from mainland
 * China. The `.cn` build renders only the `domestic` set.
 *
 * To move a link between builds, move it between these two arrays — nothing
 * else needs to change.
 */
const SOCIAL_LINKS: Record<"domestic" | "international", SocialLink[]> = {
  domestic: [
    {
      icon: "github",
      mode: "link",
      content: "https://github.com/onixbyte-opensource",
    },
    {
      // Rspress has no preset Douyin icon, so the artwork is supplied inline —
      // see `theme/lib/social-icons.ts` for the expected markup.
      icon: { svg: DOUYIN_ICON },
      mode: "link",
      content: "https://v.douyin.com/8PlxMzXors0/",
    },
  ],
  international: [
    {
      icon: "x",
      mode: "link",
      content: "https://x.com/onixbyte",
    },
  ],
}

/**
 * Per-route sitemap priorities.
 *
 * `loc` is deliberately absent. The plugin builds a full entry (including `loc`)
 * and then spreads `customMaps[routePath]` over it, so `loc` is genuinely
 * optional — its own documentation shows entries without one. The published
 * type nonetheless marks `loc` as required, so the assertion at the call site
 * bridges that mismatch. `SitemapOverrides` is what keeps the priority values
 * themselves checked.
 */
type CustomMapsOption = NonNullable<Parameters<typeof pluginSitemap>[0]["customMaps"]>
type SitemapOverrides = Record<string, Omit<CustomMapsOption[string], "loc">>

const PRIORITISED_ROUTES = [
  ["/products/", "1.0"],
  ["/services/", "1.0"],
  ["/opensource-projects/", "0.8"],
] as const

/**
 * Builds the override map for a target.
 *
 * The keys are full route paths, so they depend on which locale is unprefixed —
 * `/products/` means English on `.com` and Chinese on `.cn`.
 */
function sitemapPriorities(localePrefix: (lang: string) => string): SitemapOverrides {
  return Object.fromEntries(
    LANGS.flatMap((lang) =>
      PRIORITISED_ROUTES.map(([routePath, priority]) => [
        `${localePrefix(lang)}${routePath}`,
        { priority },
      ])
    )
  ) satisfies SitemapOverrides
}

/** Strips the language prefix, always returning a leading slash. */
function bareRoutePath(localePrefix: (lang: string) => string, routePath: string, lang: string) {
  const prefix = localePrefix(lang)
  const rest = prefix && routePath.startsWith(prefix) ? routePath.slice(prefix.length) : routePath
  return rest.startsWith("/") ? rest : `/${rest}`
}

/**
 * Writes `robots.txt` at build time.
 *
 * It cannot live in `docs/public/`, because a single static file would have to
 * carry the wrong origin for one of the two targets.
 */
function pluginRobots(origin: string): RspressPlugin {
  return {
    name: "plugin-onixbyte-robots",
    async afterBuild(config: UserConfig) {
      const outDir = path.resolve(process.cwd(), config.outDir ?? "doc_build")
      const body = ["User-agent: *", "Allow: /", "", `Sitemap: ${origin}/sitemap.xml`, ""].join(
        "\n"
      )
      await writeFile(path.join(outDir, "robots.txt"), body, "utf8")
    },
  }
}

export function createConfig(target: SiteTarget): UserConfig {
  const origin = ORIGINS[target]
  const defaultLang = DEFAULT_LANG[target]
  const socialLinks = [
    ...SOCIAL_LINKS.domestic,
    ...(target === "cn" ? [] : SOCIAL_LINKS.international),
  ]

  /** Rspress drops the prefix from the default locale's routes. */
  const localePrefix = (lang: string) => (lang === defaultLang ? "" : `/${lang}`)

  return defineConfig({
    root: path.join(__dirname, "docs"),
    title: LOCALE_META[defaultLang].title,
    description: LOCALE_META[defaultLang].description,
    icon: "/onixbyte-icon.svg",
    logo: {
      light: "/onixbyte-light-logo.svg",
      dark: "/onixbyte-dark-logo.svg",
    },
    /**
     * Per-route `<head>` additions.
     *
     * `og:title`, `og:description`, `description` and `og:type` are
     * deliberately absent: the theme's `HeadTags` already emits them from the
     * page title and site description, and site-level `head` entries do not
     * take part in its de-duplication — adding them here would produce
     * duplicate tags.
     */
    head: [
      (route) => {
        const canonical = `${origin}${route.routePath}`
        const bare = bareRoutePath(localePrefix, route.routePath, route.lang)
        const otherLang = LANGS.find((lang) => lang !== route.lang) ?? route.lang
        const alternate = `${origin}${localePrefix(otherLang)}${bare === "/" ? "/" : bare}`
        const defaultUrl = `${origin}${bare === "/" ? "/" : bare}`

        return [
          `<link rel="canonical" href="${canonical}">`,
          `<link rel="alternate" hreflang="${HREFLANG[route.lang]}" href="${canonical}">`,
          `<link rel="alternate" hreflang="${HREFLANG[otherLang]}" href="${alternate}">`,
          `<link rel="alternate" hreflang="x-default" href="${defaultUrl}">`,
          `<meta property="og:url" content="${canonical}">`,
          `<meta property="og:site_name" content="OnixByte">`,
          `<meta property="og:locale" content="${OG_LOCALE[route.lang]}">`,
          `<meta property="og:image" content="${origin}/og-image.png">`,
          `<meta name="twitter:card" content="summary_large_image">`,
        ].join("")
      },
    ],
    themeConfig: {
      // NOTE: `footer` is intentionally not set — the site footer is the
      // `SiteFooter` component wired through the Layout `bottom` slot. Setting
      // `footer.message` here would render the built-in `HomeFooter` on top of
      // it on the home page only.
      //
      // `nav` and `sidebar` are also intentionally not set: supplying either
      // switches off auto-generation and would make every `_nav.json` and
      // `_meta.json` inert.
      socialLinks,
      lastUpdated: true,
    },
    markdown: {
      showLineNumbers: true,
    },
    lang: defaultLang,
    // The default locale is listed first so the language switcher leads with it.
    locales: [defaultLang, ...LANGS.filter((lang) => lang !== defaultLang)].map((lang) => ({
      lang,
      label: LOCALE_LABELS[lang],
      ...LOCALE_META[lang],
    })),
    // Local full-text search. This is already the Rspress v2 default; stated
    // explicitly so the intent is visible. The index is emitted per locale to
    // `static/search_index.<lang>.<hash>.json` at build time.
    search: {
      mode: "local",
      codeBlocks: true,
    },
    plugins: [
      pluginSitemap({
        siteUrl: origin,
        defaultChangeFreq: "weekly",
        defaultPriority: "0.5",
        // Double assertion rather than a plain cast: the plugin's `Sitemap` type
        // requires `loc`, so the two types do not overlap enough for a single
        // assertion. See `sitemapPriorities` above for why omitting it is right.
        customMaps: sitemapPriorities(localePrefix) as unknown as CustomMapsOption,
      }),
      pluginRobots(origin),
    ],
  })
}

export default createConfig("com")