#!/usr/bin/env node
// gen-readme-shortcuts.mjs — regenerate README.md's shortcut + tips section
// from src/lib/shortcuts.ts (the single source of truth used by the in-app
// help overlay).
//
// Usage:
//   node scripts/gen-readme-shortcuts.mjs           # rewrite README
//   node scripts/gen-readme-shortcuts.mjs --check   # exit 1 if README would change
//
// To extend: add or edit entries in src/lib/shortcuts.ts, then run this
// script. The README marker block <!-- SHORTCUTS:START --> ... <!-- SHORTCUTS:END -->
// is replaced atomically; the rest of the README is left alone.

import { readFile, writeFile, mkdtemp, rm } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join, dirname, resolve } from "node:path";
import { fileURLToPath, pathToFileURL } from "node:url";

const HERE = dirname(fileURLToPath(import.meta.url));
const REPO_ROOT = resolve(HERE, "..");
const SHORTCUTS_TS = join(REPO_ROOT, "src", "lib", "shortcuts.ts");
const README_PATH = join(REPO_ROOT, "README.md");

const START_MARKER = "<!-- SHORTCUTS:START -->";
const END_MARKER = "<!-- SHORTCUTS:END -->";

const CHECK_MODE = process.argv.includes("--check");

// ----------------------------------------------------------------------------
// Load shortcuts.ts as data. The file is pure data exports — no React, no
// runtime imports — so we can strip TypeScript-only syntax with regex, drop
// the result into a temp .mjs file, and dynamically import it. Cheaper than
// pulling in tsx/esbuild as a devDep just for this one script.
// ----------------------------------------------------------------------------
async function loadShortcutsModule() {
  const src = await readFile(SHORTCUTS_TS, "utf8");
  // Strip `export interface { ... }` blocks (handles nested braces by
  // walking; the file has flat interfaces today so a brace-counter is enough).
  const stripped = stripInterfaceDecls(src)
    // Drop `: TypeAnnotation` on the export declarations
    // (e.g. `export const SHORTCUT_SECTIONS: ShortcutSection[] = [...]`).
    .replace(/^(export\s+const\s+\w+)\s*:\s*[^=]+?=/gm, "$1 =");

  const dir = await mkdtemp(join(tmpdir(), "tiletopia-genreadme-"));
  const tmpFile = join(dir, "shortcuts.mjs");
  try {
    await writeFile(tmpFile, stripped, "utf8");
    return await import(pathToFileURL(tmpFile).href);
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
}

function stripInterfaceDecls(src) {
  let out = "";
  let i = 0;
  while (i < src.length) {
    const match = src.slice(i).match(/^export\s+interface\s+\w+\s*\{/m);
    if (!match) {
      out += src.slice(i);
      break;
    }
    const localStart = src.indexOf(match[0], i);
    out += src.slice(i, localStart);
    // Walk braces to find the end of the interface block.
    let depth = 0;
    let j = localStart + match[0].length - 1; // points at the opening `{`
    for (; j < src.length; j++) {
      const c = src[j];
      if (c === "{") depth++;
      else if (c === "}") {
        depth--;
        if (depth === 0) {
          j++;
          break;
        }
      }
    }
    i = j;
  }
  return out;
}

// ----------------------------------------------------------------------------
// Render the markdown block. Mirrors the README's existing table style:
//   - 2-column `| Key | Action |` table
//   - keys wrapped in backticks
//   - description in plain prose
// Tips render as a `#### Title` heading plus a paragraph.
// ----------------------------------------------------------------------------
function renderBlock({ SHORTCUT_SECTIONS, TIPS }) {
  const lines = [];
  lines.push("");
  lines.push("#### Keyboard shortcuts");
  lines.push("");
  for (const section of SHORTCUT_SECTIONS) {
    lines.push(`**${section.title}**`);
    lines.push("");
    lines.push("| Key | Action |");
    lines.push("|---|---|");
    for (const item of section.items) {
      lines.push(`| \`${escapeCell(item.keys)}\` | ${escapeCell(item.description)} |`);
    }
    lines.push("");
  }
  lines.push("#### Tips");
  lines.push("");
  for (const tip of TIPS) {
    lines.push(`- **${escapeInline(tip.title)}** — ${escapeInline(tip.body)}`);
  }
  lines.push("");
  return lines.join("\n");
}

// Cell values must not contain raw pipes (would break the table) or newlines.
function escapeCell(s) {
  return s.replace(/\|/g, "\\|").replace(/\n/g, " ");
}

// Body text gets newlines collapsed but pipes kept (lists, not tables).
function escapeInline(s) {
  return s.replace(/\n/g, " ");
}

// ----------------------------------------------------------------------------
// Splice the generated block into the README between the markers.
// ----------------------------------------------------------------------------
function spliceReadme(readme, block) {
  const startIdx = readme.indexOf(START_MARKER);
  const endIdx = readme.indexOf(END_MARKER);
  if (startIdx === -1 || endIdx === -1) {
    throw new Error(
      `README.md is missing one of the markers (${START_MARKER} / ${END_MARKER}). ` +
        "Add them around the section you want regenerated.",
    );
  }
  if (endIdx < startIdx) {
    throw new Error(`${END_MARKER} appears before ${START_MARKER} in README.md`);
  }
  const before = readme.slice(0, startIdx + START_MARKER.length);
  const after = readme.slice(endIdx);
  return `${before}\n${block}\n${after}`;
}

// ----------------------------------------------------------------------------
// Main.
// ----------------------------------------------------------------------------
const mod = await loadShortcutsModule();
const block = renderBlock(mod);
const readme = await readFile(README_PATH, "utf8");
const next = spliceReadme(readme, block);

if (CHECK_MODE) {
  if (next !== readme) {
    process.stderr.write(
      "README.md is out of sync with src/lib/shortcuts.ts. " +
        "Run `pnpm gen:readme` to regenerate.\n",
    );
    process.exit(1);
  }
  process.stdout.write("README.md is in sync with src/lib/shortcuts.ts.\n");
  process.exit(0);
}

if (next === readme) {
  process.stdout.write("README.md already up to date.\n");
} else {
  await writeFile(README_PATH, next, "utf8");
  process.stdout.write("README.md regenerated.\n");
}