import {
  createReadStream,
  existsSync,
  mkdtempSync,
  readdirSync,
  statSync,
  writeFileSync,
} from "node:fs";
import { createServer } from "node:http";
import { homedir, tmpdir } from "node:os";
import { extname, join, normalize } from "node:path";
import { extractFile } from "@electron/asar";
import esbuild from "esbuild";
import { root, sharedLib, svelte } from "../esbuild.config.mjs";

const port = Number(process.env.PORT ?? 4174);

const ASAR_CANDIDATES = [
  process.env.OBSIDIAN_ASAR,
  "/Applications/Obsidian.app/Contents/Resources/obsidian.asar",
  join(homedir(), "Applications/Obsidian.app/Contents/Resources/obsidian.asar"),
  "/opt/Obsidian/resources/obsidian.asar",
  "/usr/lib/obsidian/resources/obsidian.asar",
].filter(Boolean);

function findAppCss() {
  for (const candidate of ASAR_CANDIDATES) {
    if (!existsSync(candidate)) {
      continue;
    }
    try {
      const path = join(mkdtempSync(join(tmpdir(), "beaver-app-")), "app.css");
      writeFileSync(path, extractFile(candidate, "app.css"));
      return path;
    } catch {
      /* try the next candidate */
    }
  }
  console.warn(
    "preview: could not read app.css from an Obsidian install. Set OBSIDIAN_ASAR to point at obsidian.asar; without it the chrome will not match the real app."
  );
  return null;
}

function findTheme() {
  if (process.env.THEME) {
    return process.env.THEME;
  }
  const vault = process.env.VAULT;
  if (!vault) {
    return null;
  }
  const themes = join(vault, ".obsidian/themes");
  if (!existsSync(themes)) {
    return null;
  }
  for (const name of readdirSync(themes)) {
    const css = join(themes, name, "theme.css");
    if (existsSync(css)) {
      return css;
    }
  }
  return null;
}

const appCss = findAppCss();
const theme = findTheme();

const ctx = await esbuild.context({
  bundle: true,
  conditions: ["svelte", "browser"],
  entryPoints: [join(root, "preview/entry.ts")],
  format: "iife",
  logLevel: "info",
  mainFields: ["svelte", "browser", "module", "main"],
  outfile: join(root, "preview/bundle.js"),
  plugins: [
    sharedLib({ obsidian: join(root, "tests/obsidian-stub.ts") }),
    svelte(),
  ],
  sourcemap: "inline",
  target: "es2022",
});
await ctx.rebuild();
await ctx.watch();

const TYPES = {
  ".css": "text/css; charset=utf-8",
  ".html": "text/html; charset=utf-8",
  ".js": "text/javascript; charset=utf-8",
};

createServer((request, response) => {
  const url = decodeURIComponent((request.url ?? "/").split("?")[0]);
  const external = { "/app.css": appCss, "/theme.css": theme };

  if (url in external) {
    const file = external[url];
    if (!file) {
      response.writeHead(200, { "content-type": TYPES[".css"] }).end("");
      return;
    }
    response.writeHead(200, {
      "cache-control": "no-store",
      "content-type": TYPES[".css"],
    });
    createReadStream(file).pipe(response);
    return;
  }

  const file = join(root, normalize(url === "/" ? "/preview/index.html" : url));
  if (
    !(file.startsWith(root) && existsSync(file)) ||
    statSync(file).isDirectory()
  ) {
    response.writeHead(404).end("not found");
    return;
  }
  response.writeHead(200, {
    "cache-control": "no-store",
    "content-type": TYPES[extname(file)] ?? "application/octet-stream",
  });
  createReadStream(file).pipe(response);
}).listen(port, () => {
  console.log(`preview: http://localhost:${port}/`);
});