#!/usr/bin/env node
// =============================================================
// adapters/lit/adapt.mjs — the Lit reference adapter (WHYNOT-WP-0002)
//
// Projects the technology-neutral IR (ir/) onto the Lit stack. Per
// adapters/ADAPTER_CONTRACT.md this is scaffold + drift-detect, never a rewrite:
//
//   • tokens (T06)      → FULLY generated, deterministic (this file, today)
//   • new component     → stub (T07)
//   • changed component → drift report (T07), never an overwrite
//
// Exit codes: 0 ok · 2 usage/config · 3 drift · 4 parity · 5 internal.
//
// Run via `make adapt-lit`. Tokens regenerate the :root block of
// src/styles/colors_and_type.css between generated markers; the hand-authored
// type/utility CSS after it is preserved untouched. Re-running with an unchanged
// ir/tokens.json is a no-op (byte-identical output).
// =============================================================
import { readFileSync, writeFileSync, existsSync } from "node:fs";
import { join, dirname } from "node:path";
import { fileURLToPath } from "node:url";

const REPO = join(dirname(fileURLToPath(import.meta.url)), "..", "..");
const TOKENS_JSON = join(REPO, "ir", "tokens.json");
const TOKEN_CSS = join(REPO, "src", "styles", "colors_and_type.css");

const BEGIN = "/* @generated tokens — regenerated by `make adapt-lit` from ir/tokens.json. DO NOT EDIT. */";
const END = "/* @end generated tokens */";

// ---------- tokens: ir/tokens.json (DTCG) → CSS custom properties ----------
function refToVar(value) {
  // {group.key} alias → var(--key). Literals pass through unchanged.
  const m = /^\{[A-Za-z0-9]+\.([A-Za-z0-9-]+)\}$/.exec(String(value).trim());
  return m ? `var(--${m[1]})` : value;
}

function renderRootBlock(tokens) {
  const lines = [BEGIN, ":root {"];
  for (const [group, entries] of Object.entries(tokens)) {
    lines.push(`  /* ${group} */`);
    for (const [key, tok] of Object.entries(entries)) {
      if (key === "$type") continue;
      lines.push(`  --${key}: ${refToVar(tok.$value)};`);
    }
  }
  lines.push("}", END);
  return lines.join("\n");
}

// Replace the current :root token region with the freshly generated block.
// First run (no markers): replace the first `:root { … }` via brace matching.
// Later runs: replace strictly between the @generated markers.
function spliceTokenBlock(css, block) {
  const b = css.indexOf(BEGIN);
  if (b !== -1) {
    const e = css.indexOf(END, b);
    if (e === -1) throw new Error("Found @generated marker without its @end — refusing to guess.");
    return css.slice(0, b) + block + css.slice(e + END.length);
  }
  const rootAt = css.indexOf(":root");
  if (rootAt === -1) throw new Error("No :root block in colors_and_type.css to replace.");
  let i = css.indexOf("{", rootAt), depth = 0;
  for (; i < css.length; i++) {
    if (css[i] === "{") depth++;
    else if (css[i] === "}" && --depth === 0) break;
  }
  return css.slice(0, rootAt) + block + css.slice(i + 1);
}

function generateTokens() {
  if (!existsSync(TOKENS_JSON)) {
    console.error("No ir/tokens.json — run `make ir` first.");
    process.exit(2);
  }
  const tokens = JSON.parse(readFileSync(TOKENS_JSON, "utf8"));
  const block = renderRootBlock(tokens);
  const before = existsSync(TOKEN_CSS) ? readFileSync(TOKEN_CSS, "utf8") : `${block}\n`;
  const after = existsSync(TOKEN_CSS) ? spliceTokenBlock(before, block) : `${block}\n`;
  const count = block.split("\n").filter((l) => l.trim().startsWith("--")).length;
  if (after === before) {
    console.log(`tokens: up to date (${count} custom properties, no change).`);
    return;
  }
  writeFileSync(TOKEN_CSS, after);
  console.log(`tokens: regenerated ${count} custom properties → src/styles/colors_and_type.css`);
}

function main() {
  generateTokens();
  // T07 will add: component stub scaffolding + drift reports here.
  console.log("adapt-lit: tokens done. (component scaffold + drift: T07)");
}

main();