#!/usr/bin/env node
import fs from 'node:fs';
import path from 'node:path';
import yaml from 'yaml';

const ROOT = path.resolve('src/Api/StellaOps.Api.OpenApi');
const BASELINE = path.join(ROOT, 'baselines', 'stella-baseline.yaml');
const CURRENT = path.join(ROOT, 'stella.yaml');
const OUTPUT = path.join(ROOT, 'CHANGELOG.md');

function panic(message) {
  console.error(`[api:changelog] ${message}`);
  process.exit(1);
}

function loadSpec(file) {
  if (!fs.existsSync(file)) {
    panic(`Spec not found: ${file}`);
  }
  return yaml.parse(fs.readFileSync(file, 'utf8'));
}

function enumerateOps(spec) {
  const ops = new Map();
  for (const [route, methods] of Object.entries(spec.paths || {})) {
    for (const [method, operation] of Object.entries(methods || {})) {
      const lower = method.toLowerCase();
      if (!['get','post','put','delete','patch','head','options','trace'].includes(lower)) continue;
      const id = `${lower.toUpperCase()} ${route}`;
      ops.set(id, operation || {});
    }
  }
  return ops;
}

function diffSpecs(oldSpec, newSpec) {
  const oldOps = enumerateOps(oldSpec);
  const newOps = enumerateOps(newSpec);
  const additive = [];
  const breaking = [];

  for (const id of newOps.keys()) {
    if (!oldOps.has(id)) {
      additive.push(id);
    }
  }
  for (const id of oldOps.keys()) {
    if (!newOps.has(id)) {
      breaking.push(id);
    }
  }
  return { additive: additive.sort(), breaking: breaking.sort() };
}

function renderMarkdown(diff) {
  const lines = [];
  lines.push('# API Changelog');
  lines.push('');
  const date = new Date().toISOString();
  lines.push(`Generated: ${date}`);
  lines.push('');
  lines.push('## Additive Operations');
  if (diff.additive.length === 0) {
    lines.push('- None');
  } else {
    diff.additive.forEach((op) => lines.push(`- ${op}`));
  }
  lines.push('');
  lines.push('## Breaking Operations');
  if (diff.breaking.length === 0) {
    lines.push('- None');
  } else {
    diff.breaking.forEach((op) => lines.push(`- ${op}`));
  }
  lines.push('');
  return lines.join('\n');
}

function main() {
  if (!fs.existsSync(BASELINE)) {
    console.log('[api:changelog] baseline missing; skipping');
    return;
  }
  const diff = diffSpecs(loadSpec(BASELINE), loadSpec(CURRENT));
  const markdown = renderMarkdown(diff);
  fs.writeFileSync(OUTPUT, markdown, 'utf8');
  console.log(`[api:changelog] wrote changelog to ${OUTPUT}`);
}

main();