import { readFile, writeFile, mkdir, rm, copyFile } from "node:fs/promises";
import { createHash } from "node:crypto";
import { resolve, extname } from "node:path";
import { execFile } from "node:child_process";
import { promisify } from "node:util";
import { load } from "cheerio";
import { convert } from "./convert.mjs";
import { configureBrowser } from "./browser.mjs";
import { serve } from "./server.mjs";

const root = resolve(import.meta.dirname, "..");
process.chdir(root);
const exec = promisify(execFile);
const publication = JSON.parse(await readFile("publication.json", "utf8"));
if (typeof publication.preview !== "boolean") throw new Error("publication.preview must explicitly select preview or publication mode.");
const source = await readFile("spec.md", "utf8");
const { html, diagrams, report } = convert(source, publication);
await rm("dist", { recursive: true, force: true });
await mkdir("dist/assets", { recursive: true });
await mkdir(".build/cache", { recursive: true });
await copyFile("styles/spec.css", "dist/assets/spec.css");
await copyFile("static/favicon.svg", "dist/assets/favicon.svg");
await copyFile("spec.md", "dist/spec.md");
await writeFile(".build/source.html", html);
const browserPath = await configureBrowser();
await writeFile(".build/puppeteer.json", JSON.stringify({ headless: true, args: ["--no-sandbox"], ...(browserPath ? { executablePath: browserPath } : {}) }));
await writeFile(".build/mermaid.json", JSON.stringify({ theme: "neutral", flowchart: { htmlLabels: false }, fontFamily: "Arial, sans-serif" }));
for (const diagram of diagrams) {
  await writeFile(`.build/${diagram.name}.mmd`, diagram.source);
  await exec(process.execPath, ["node_modules/@mermaid-js/mermaid-cli/src/cli.js", "-i", `.build/${diagram.name}.mmd`, "-o", `dist/assets/${diagram.name}.svg`, "-p", ".build/puppeteer.json", "-c", ".build/mermaid.json", "-b", "transparent"], { maxBuffer: 2 ** 20 });
}
const server = await serve(".build", { mounts: {
  "/node_modules/respec/": resolve("node_modules/respec"),
  "/assets/": resolve("dist/assets"),
} });
let rendered;
try {
  const { toHTML } = await import("respec");
  rendered = await toHTML(new URL("source.html", server.url).href, {
    timeout: 120_000,
    // Renders this repo's own source; the sandbox cannot start on hosts that
    // restrict unprivileged user namespaces.
    disableSandbox: true,
    onError: error => console.error("ReSpec error:", error.message),
    onWarning: warning => console.warn("ReSpec warning:", warning.message),
  });
} finally { await server.close(); }
if (rendered.errors.length) throw new Error(`ReSpec reported ${rendered.errors.length} error(s).`);
report.respecWarnings = rendered.warnings.map(w => w.message);
await writeFile(".build/respec.html", rendered.html);

// Cache build-time upstream resources, and ship all actual rendering dependencies locally.
const downloads = new Map();
async function download(url) {
  const key = createHash("sha256").update(url).digest("hex");
  const file = `.build/cache/${key}`;
  try { return await readFile(file); } catch {}
  const response = await fetch(url, { signal: AbortSignal.timeout(30_000) });
  if (!response.ok) throw new Error(`Download failed: ${response.status} ${url}`);
  const bytes = Buffer.from(await response.arrayBuffer());
  await writeFile(file, bytes);
  return bytes;
}
async function localize(url, css = false) {
  if (downloads.has(url)) return downloads.get(url);
  const task = (async () => {
    const key = createHash("sha256").update(url).digest("hex").slice(0, 16);
    const extension = css ? ".css" : extname(new URL(url).pathname) || ".bin";
    const name = `upstream-${key}${extension}`;
    let bytes = await download(url);
    if (css) {
      let text = bytes.toString();
      const pattern = /url\(\s*(?:"([^"]*)"|'([^']*)'|([^\s)]*))\s*\)/g;
      const matches = [...text.matchAll(pattern)];
      for (const match of matches.reverse()) {
        const target = match[1] ?? match[2] ?? match[3];
        if (!target || target.startsWith("data:") || target.startsWith("#")) continue;
        const absolute = new URL(target, url).href;
        const path = await localize(absolute, /\.css(?:[?#]|$)/.test(absolute));
        text = text.slice(0, match.index) + `url("${path}")` + text.slice(match.index + match[0].length);
      }
      const imports = [...text.matchAll(/@import\s+["']([^"']+)["']/g)];
      for (const match of imports.reverse()) {
        const path = await localize(new URL(match[1], url).href, true);
        text = text.slice(0, match.index) + `@import url("${path}")` + text.slice(match.index + match[0].length);
      }
      bytes = Buffer.from(text);
    }
    await writeFile(`dist/assets/${name}`, bytes);
    return name;
  })();
  downloads.set(url, task);
  return task;
}
const $ = load(rendered.html);
$("head").append('<link rel="icon" href="assets/favicon.svg" type="image/svg+xml">');
// No authoring engine, analytics, remote executable, or JS needed to read the document.
$("script, link[rel=preconnect], link[rel=dns-prefetch], link[rel=preload], link[rel=modulepreload]").remove();
// ReSpec's conformance plugin inserts an h1 even in an unnumbered front-matter section.
$("#conformance > h1").replaceWith("<h2>Conformance</h2>");
$("link[rel=stylesheet]").each((_, el) => {
  if (!$(el).attr("href")) $(el).remove();
});
for (const el of $("link[rel=stylesheet]").toArray()) {
  const href = $(el).attr("href");
  if (/^https?:/.test(href)) $(el).attr("href", `assets/${await localize(href, true)}`);
  else if (/^\//.test(href)) throw new Error(`Unexpected absolute stylesheet path: ${href}`);
}
$('link[rel=stylesheet][href="assets/spec.css"]').appendTo("head");
$('meta[name="color-scheme"]').attr("content", "light");
for (const el of $("img[src]").toArray()) {
  const src = $(el).attr("src");
  if (/^https?:/.test(src)) $(el).attr("src", `assets/${await localize(src)}`);
}
$("table").each((_, table) => { $(table).wrap('<div class="table-scroll" tabindex="0" role="region" aria-label="Scrollable specification table"></div>'); });
// Match prose reference labels against ReSpec's actual numbering, rather than trusting our arithmetic.
for (const el of $("a.source-section-ref").toArray()) {
  const id = $(el).attr("href").slice(1);
  const actual = $(`#${id}`).find(".secno").first().text().trim().replace(/\.$/, "");
  if (!actual) throw new Error(`No generated section number for ${id}`);
  $(el).text(actual);
}
report.externalAssets = [...downloads.keys()];
await writeFile("dist/index.html", $.html());
await writeFile("dist/build-report.json", JSON.stringify(report, null, 2) + "\n");
console.log(`Built dist/index.html: ${report.sectionCount} sections, ${report.definitionCount} definitions, ${diagrams.length} diagram(s).`);
console.log(`Unresolved source references: ${report.unresolvedSourceReferences.join(", ") || "none"}.`);
console.log(`Publication placeholders: ${report.publicationPlaceholders.join(", ") || "none"}.`);
console.log(`${publication.preview ? "Local preview" : "Publication"} build. Nothing uploaded by this build.`);