#!/usr/bin/env node
// Regenerates the devlog data module from the last few commits. The client has
// no build step, so the list the main menu shows has to live in the tree; this
// script keeps it current and is run by the pre-commit hook (and by hand with
// `node scripts/generate-devlog.js`).
//
// The file is written only when it changes, so an unchanged history does not
// touch the working tree.

import { execFileSync } from "node:child_process";
import { readFileSync, writeFileSync } from "node:fs";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";

const ROOT = dirname(dirname(fileURLToPath(import.meta.url)));
const OUT = join(ROOT, "client", "js", "devlog_data.js");
// How many commits the Devlog shows.
const COUNT = 10;
// Field separator inside a commit record and the record separator between
// commits. Neither byte is legal in a git commit message.
const FIELD = "\x1f";
const RECORD = "\x1e";

function lastCommits() {
  const pretty = `--pretty=format:%h${FIELD}%cs${FIELD}%s${FIELD}%b${RECORD}`;
  const out = execFileSync("git", ["log", `-n${COUNT}`, pretty], {
    cwd: ROOT,
    encoding: "utf8",
  });
  return out
    .split(RECORD)
    // `git log` puts a newline between records; drop the leading ones.
    .map((record) => record.replace(/^\n+/, ""))
    .filter((record) => record.trim().length > 0)
    .map((record) => {
      const [hash, date, subject, body = ""] = record.split(FIELD);
      return {
        hash: hash.trim(),
        date: date.trim(),
        subject: subject.trim(),
        body: body.trim(),
      };
    });
}

function source(commits) {
  return (
    "// Generated by scripts/generate-devlog.js from `git log`; do not edit.\n" +
    "// The pre-commit hook refreshes it so the main menu shows the latest commits.\n" +
    `export const DEVLOG = ${JSON.stringify(commits, null, 2)};\n`
  );
}

let commits;
try {
  commits = lastCommits();
} catch (error) {
  console.warn(`generate-devlog: could not read the git history (${error.message})`);
  process.exit(0);
}

const next = source(commits);
let previous = "";
try {
  previous = readFileSync(OUT, "utf8");
} catch {
  // First run: the file does not exist yet.
}
if (next === previous) {
  console.log(`generate-devlog: ${OUT} is already up to date (${commits.length} commits)`);
} else {
  writeFileSync(OUT, next);
  console.log(`generate-devlog: wrote ${commits.length} commits to ${OUT}`);
}