import { readFile, writeFile } from 'node:fs/promises'
import path from 'node:path'
import { createRequire } from 'node:module'
import * as esbuild from 'esbuild'

const require = createRequire(import.meta.url)
const scriptDir = import.meta.dirname
const mobileRoot = path.resolve(scriptDir, '..')
const outputPath = path.join(mobileRoot, 'src', 'terminal', 'terminal-webview-engine.generated.ts')
/**
 * The stylesheet is written beside the engine rather than inside it because the two have different
 * consumers. The WebView document needs both, as text; the web page needs the CSS and must never
 * resolve the 612 KiB engine string, which is unusable under the shell's `script-src 'self'` and
 * is the largest module the session route's closure would otherwise carry. One file each is what
 * lets the page import one without reaching the other.
 */
const cssOutputPath = path.join(
  mobileRoot,
  'src',
  'terminal',
  'terminal-webview-engine-css.generated.ts'
)
const target = 'chrome74'

const packages = ['@xterm/xterm', '@xterm/addon-unicode11', '@xterm/addon-webgl']

async function readPackageVersion(packageName) {
  // Why: a package.json module specifier must use '/' — path.join emits '\' on
  // Windows, yielding an unresolvable bare specifier that fails postinstall there.
  const packageJsonPath = require.resolve(`${packageName}/package.json`)
  const packageJson = JSON.parse(await readFile(packageJsonPath, 'utf8'))
  return `${packageName}@${packageJson.version}`
}

function htmlText(value, closingTag) {
  return value.replace(new RegExp(`</${closingTag}`, 'gi'), `<\\/${closingTag}`)
}

async function buildEngineJs() {
  const result = await esbuild.build({
    stdin: {
      contents: `
        import { Terminal } from '@xterm/xterm'
        import { Unicode11Addon } from '@xterm/addon-unicode11'
        import { WebglAddon } from '@xterm/addon-webgl'

        // Why: xterm reaches for these runtime APIs on the terminal-bringup path,
        // and esbuild lowers syntax but not runtime APIs. Guarded shims let the
        // chrome74-syntax bundle actually run on old WebViews (the #7030 goal)
        // instead of throwing at construction and only surfacing the error overlay.

        // WeakRef (Chrome 84+): lazily constructed in window-tracking paths.
        // Strong retention is fine for a single-document terminal WebView.
        if (typeof window.WeakRef === 'undefined') {
          window.WeakRef = function WeakRefShim(target) { this.__target = target }
          window.WeakRef.prototype.deref = function () { return this.__target }
        }

        // structuredClone (Chrome 98+): xterm clones its plain-data DEC-mode default
        // objects at Terminal construction; a JSON round-trip clones those correctly
        // (any undefined-valued keys drop, but every reader treats absent == undefined).
        if (typeof window.structuredClone === 'undefined') {
          window.structuredClone = function (value) { return JSON.parse(JSON.stringify(value)) }
        }

        // Element.prototype.replaceChildren (Chrome 86+): used on the row/selection
        // render path; polyfill via remove-all + append (Chrome 54+, under the floor).
        if (typeof Element !== 'undefined' && !Element.prototype.replaceChildren) {
          Element.prototype.replaceChildren = function () {
            while (this.firstChild) this.removeChild(this.firstChild)
            this.append.apply(this, arguments)
          }
        }

        window.Terminal = Terminal
        window.Unicode11Addon = { Unicode11Addon }
        window.WebglAddon = { WebglAddon }
      `,
      resolveDir: mobileRoot,
      sourcefile: 'terminal-webview-engine-entry.js'
    },
    bundle: true,
    format: 'iife',
    minify: true,
    platform: 'browser',
    target,
    legalComments: 'none',
    write: false,
    logLevel: 'silent'
  })

  return result.outputFiles[0].text
}

async function main() {
  const [engineJs, rawEngineCss, ...versions] = await Promise.all([
    buildEngineJs(),
    readFile(require.resolve('@xterm/xterm/css/xterm.css'), 'utf8'),
    ...packages.map(readPackageVersion)
  ])
  // Why: the no-external-URL regression gate bans http(s):// anywhere in the
  // terminal document. These xmlns URIs live inside data: URLs (never fetched);
  // percent-encoding the scheme colon satisfies the gate and URI-decodes back
  // before the SVG is parsed.
  const engineCss = rawEngineCss
    .replace(/\/\*[\s\S]*?\*\//g, '')
    .replace(/http:\/\/www\.w3\.org\/2000\/svg/g, 'http%3A//www.w3.org/2000/svg')

  const header = [
    '// Generated by scripts/build-terminal-webview-engine.mjs.',
    `// Packages: ${versions.join(', ')}.`,
    `// Target: ${target}. Do not edit by hand; regenerate via pnpm postinstall.`
  ]
  await Promise.all([
    writeFile(
      outputPath,
      [
        ...header,
        `export const XTERM_ENGINE_JS = ${JSON.stringify(htmlText(engineJs, 'script'))}`,
        ''
      ].join('\n')
    ),
    writeFile(
      cssOutputPath,
      [
        ...header,
        `export const XTERM_ENGINE_CSS = ${JSON.stringify(htmlText(engineCss, 'style'))}`,
        ''
      ].join('\n')
    )
  ])
}

await main()