#!/usr/bin/env node
/*
 * Write contrib/shaders/*.kdl from the presets in contrib/shadertoy.html.
 *
 * The page is the source: it is where the presets are written, previewed and
 * conformance-tested, and a second copy maintained by hand would be a second
 * copy maintained badly. tests/test_shader_presets.py regenerates into a temp
 * directory and fails if the committed files have drifted, so "I edited the
 * page and forgot" is a failing test rather than a stale example.
 *
 *   contrib/gen-shaders            write the files
 *   contrib/gen-shaders --check    say whether they are current, write nothing
 */
"use strict";
const fs = require("fs");
const path = require("path");

const here = __dirname;
const html = fs.readFileSync(path.join(here, "shadertoy.html"), "utf8");
const script = html.split("<script>")[1].split("</script>")[0];
/* Everything up to the DOM: the presets and nothing that needs a browser. */
const prelude = script.slice(0, script.indexOf("/* ---- the chain UI"));
const PRESETS = new Function(prelude + "; return PRESETS;")();

/* "built-ins, as expressions" is a heading, not a filename: the qualifier is
 * dropped so the file is built-ins-scanlines.kdl and not a sentence. */
const slug = (s) => s.toLowerCase().replace(/,.*$/, "")
  .replace(/[^a-z0-9]+/g, "-").replace(/(^-|-$)/g, "");

function render(group, name, chain) {
  const body = chain.map((p) => {
    const color = p.op === "tint" ? ` color="${p.color}"` : "";
    return `    ${p.op}${color} amount="${p.amount}"`;
  }).join("\n");
  return `// ${name} — ${group}
//
// Generated from contrib/shadertoy.html by contrib/gen-shaders; edit the
// preset there, where you can see what it does, and run that again.
//
// Drop this into ~/.config/slosh/config.kdl (a running session picks it up
// when you save), or point $SLOSH_CONFIG at this file. To hang it off a
// pane state instead of every pane, put the same passes inside one:
//
//     states { unfocused { ... } }

shaders {
${body}
}
`;
}

const outDir = process.argv.includes("--out")
  ? process.argv[process.argv.indexOf("--out") + 1]
  : path.join(here, "shaders");
const check = process.argv.includes("--check");

if (!check) fs.mkdirSync(outDir, { recursive: true });

let stale = [];
let count = 0;
for (const [group, entries] of Object.entries(PRESETS)) {
  for (const [name, chain] of Object.entries(entries)) {
    const file = path.join(outDir, `${slug(group)}-${slug(name)}.kdl`);
    const text = render(group, name, chain);
    count++;
    if (check) {
      let have = null;
      try { have = fs.readFileSync(file, "utf8"); } catch { /* missing */ }
      if (have !== text) stale.push(path.basename(file));
    } else {
      fs.writeFileSync(file, text);
    }
  }
}

if (check) {
  /* A file nobody generates any more is as stale as one that has changed. */
  const want = new Set();
  for (const [group, entries] of Object.entries(PRESETS))
    for (const name of Object.keys(entries))
      want.add(`${slug(group)}-${slug(name)}.kdl`);
  for (const f of fs.readdirSync(outDir))
    if (f.endsWith(".kdl") && !want.has(f)) stale.push(`${f} (no longer a preset)`);

  if (stale.length) {
    console.error("stale, run contrib/gen-shaders:\n  " + stale.join("\n  "));
    process.exit(1);
  }
  console.log(`${count} preset files are current`);
} else {
  console.log(`wrote ${count} files to ${path.relative(process.cwd(), outDir)}`);
}