// Byte-snapshot harness for product wire formats: assert an emitted artifact
// (workflow YAML, manifest JSON, compose file) matches a committed fixture
// byte-for-byte, so unintended emission changes show up as a reviewable diff.
// Refresh deliberately: UPDATE_SNAPSHOTS=1 bun test <suite> rewrites fixtures;
// commit the diff with the change that caused it. Framework-free (plain throw),
// so it works under bun:test, vitest, or bare scripts alike.
import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
import { dirname } from "node:path";

const UPDATE_HINT = "run UPDATE_SNAPSHOTS=1 bun test to (re)write it, then commit the fixture";

function updating(): boolean {
  const v = process.env.UPDATE_SNAPSHOTS;
  return v !== undefined && v !== "" && v !== "0" && v.toLowerCase() !== "false";
}

function firstDiffLine(actual: string, expected: string): string {
  const a = actual.split("\n");
  const e = expected.split("\n");
  for (let i = 0; i < Math.max(a.length, e.length); i++) {
    if (a[i] !== e[i]) {
      return `line ${i + 1}: snapshot ${JSON.stringify(e[i] ?? "<missing>")}, actual ${JSON.stringify(a[i] ?? "<missing>")}`;
    }
  }
  return "content differs";
}

export function expectByteSnapshot(actual: string, fixturePath: string): void {
  if (updating()) {
    mkdirSync(dirname(fixturePath), { recursive: true });
    writeFileSync(fixturePath, actual);
    return;
  }
  if (!existsSync(fixturePath)) {
    throw new Error(`no committed snapshot at ${fixturePath} — ${UPDATE_HINT}.`);
  }
  const expected = readFileSync(fixturePath, "utf8");
  if (actual !== expected) {
    throw new Error(
      `emitted bytes differ from the committed snapshot ${fixturePath} (${firstDiffLine(actual, expected)}). If the change is intended, ${UPDATE_HINT}.`,
    );
  }
}