// The last coverage run of each suite, for Grafana (#394): lines the tests reach and lines there
// are, by suite and part, as a file node-exporter's textfile collector serves to Prometheus.
//
//   node scripts/coverage-metrics.ts        (scripts/coverage.sh runs it after each report)
//
// Suites: `cargo` (the cargo tests, target/coverage/cargo), `browser` (the browser suite against an
// instrumented ipx and ipx-directory, target/coverage/api) and `page` (web/src under the browser
// suite, target/coverage/page). Parts: the crate, or `page`. Each run writes every suite that has
// a report, so one suite's run leaves the others' numbers as they were.
import fs from 'node:fs';
import path from 'node:path';

const COVERAGE = path.join(import.meta.dirname, '..', 'target', 'coverage');
// node-exporter reads it as /host/... (it mounts / at /host), on /mnt/fast beside its appdata.
const OUT = process.env.IPX_COVERAGE_TEXTFILE ?? '/mnt/fast/appdata/node-exporter/textfile';

type Count = { covered: number, total: number };
type Suite = { parts: Map<string, Count>, at: number };

/// The crate a path in cargo-llvm-cov's summary belongs to: directory/src/... is ipx-directory's.
const crateOf = (file: string) => file.startsWith('directory/') ? 'ipx-directory' : file.startsWith('feed/') ? 'ipx-feed' : 'ipx';

function add(parts: Map<string, Count>, part: string, covered: number, total: number) {
  const c = parts.get(part) ?? { covered: 0, total: 0 };
  c.covered += covered; c.total += total;
  parts.set(part, c);
}

/// cargo-llvm-cov's summary: a line a file, Lines and Missed Lines its 8th and 9th columns.
function rust(dir: string): Suite | null {
  const file = path.join(COVERAGE, dir, 'summary.txt');
  if (!fs.existsSync(file)) return null;
  const parts = new Map<string, Count>();
  for (const line of fs.readFileSync(file, 'utf8').split('\n')) {
    const cols = line.trim().split(/\s+/);
    if (cols.length < 10 || !cols[0]!.endsWith('.rs')) continue;
    const lines = Number(cols[7]), missed = Number(cols[8]);
    if (Number.isFinite(lines) && Number.isFinite(missed)) add(parts, crateOf(cols[0]!), lines - missed, lines);
  }
  return { parts, at: fs.statSync(file).mtimeMs / 1000 };
}

function page(): Suite | null {
  const file = path.join(COVERAGE, 'page', 'summary.json');
  if (!fs.existsSync(file)) return null;
  const { lines } = JSON.parse(fs.readFileSync(file, 'utf8')) as { lines: ({ file: string } & Count)[] };
  const parts = new Map<string, Count>();
  for (const l of lines) add(parts, 'page', l.covered, l.total);
  return { parts, at: fs.statSync(file).mtimeMs / 1000 };
}

const suites: [string, Suite | null][] = [['cargo', rust('cargo')], ['browser', rust('api')], ['page', page()]];
const out = [
  '# HELP ipx_coverage_lines Lines of iPX the tests reached and lines there are, as each suite\'s last coverage run found them (#394).',
  '# TYPE ipx_coverage_lines gauge',
];
for (const [suite, s] of suites) if (s) for (const [part, c] of s.parts) {
  out.push(`ipx_coverage_lines{suite="${suite}",part="${part}",state="covered"} ${c.covered}`);
  out.push(`ipx_coverage_lines{suite="${suite}",part="${part}",state="total"} ${c.total}`);
}
out.push('# HELP ipx_coverage_run_timestamp_seconds When each suite\'s last coverage report was made.');
out.push('# TYPE ipx_coverage_run_timestamp_seconds gauge');
for (const [suite, s] of suites) if (s) out.push(`ipx_coverage_run_timestamp_seconds{suite="${suite}"} ${Math.round(s.at)}`);

fs.mkdirSync(OUT, { recursive: true });
// Written aside and renamed in, so a scrape never reads half a file.
const file = path.join(OUT, 'ipx_coverage.prom');
fs.writeFileSync(file + '.tmp', out.join('\n') + '\n');
fs.renameSync(file + '.tmp', file);
console.log(`coverage for Grafana: ${file}`);
for (const [suite, s] of suites) if (s) for (const [part, c] of s.parts)
  console.log(`  ${suite} ${part}: ${(100 * c.covered / c.total).toFixed(1)}% of ${c.total} lines`);