// cases.mjs: the module corpus (corpus.json) read into the bytes a sink passes, and the
// checks every runner makes of what came back. For Node; no dependency.
//
// A case's payload is a path below wai/, or {"hex"}; its set is null, one file, {"external"}
// (a file the corpus names by digest and does not hold, read from the --external
// directory), or a list of [name, file] pairs passed as waism §5's file sequence: for each
// file in order, the name's length in one byte, the name, the file's length in four bytes
// little-endian, and the file.

import { createHash } from 'node:crypto';
import { readFileSync } from 'node:fs';
import { dirname, join, resolve } from 'node:path';

export function sha256(b) {
  return createHash('sha256').update(b).digest('hex');
}

function file(v, wai, external) {
  if (typeof v === 'string') return new Uint8Array(readFileSync(join(wai, v)));
  if (v && typeof v.hex === 'string') return new Uint8Array(Buffer.from(v.hex, 'hex'));
  if (v && typeof v.file === 'string') return new Uint8Array(readFileSync(join(wai, v.file)));
  if (v && typeof v.external === 'string') {
    if (!external) throw new Error(`${v.external} is an external file, and no --external directory was given`);
    return new Uint8Array(readFileSync(join(external, v.external)));
  }
  throw new Error(`not a file: ${JSON.stringify(v)}`);
}

function set(v, wai, external) {
  if (v === null) return new Uint8Array(0);
  if (!Array.isArray(v)) return file(v, wai, external);
  const parts = [];
  for (const [name, what] of v) {
    const b = file(what, wai, external);
    const n = Buffer.from(name, 'utf8');
    if (n.length < 1 || n.length > 255) throw new Error(`a name of ${n.length} bytes`);
    const len = Buffer.alloc(4);
    len.writeUInt32LE(b.length);
    parts.push(Buffer.from([n.length]), n, len, b);
  }
  return new Uint8Array(Buffer.concat(parts));
}

/** The cases of a corpus.json, with their bytes. */
export function loadCases(corpusPath, { external = null, only = null } = {}) {
  const doc = JSON.parse(readFileSync(corpusPath, 'utf8'));
  if (doc.format !== 'waism-module-corpus/1') throw new Error(`${corpusPath}: not a waism-module-corpus/1`);
  const wai = dirname(dirname(resolve(corpusPath)));
  const cases = [];
  for (const c of doc.cases) {
    if (only && !c.name.startsWith(only)) continue;
    try {
      cases.push({ name: c.name, cap: c.capability, payload: file(c.payload, wai, external), set: set(c.set, wai, external), expect: c.expect });
    } catch (e) {
      throw new Error(`${c.name}: ${e.message}`);
    }
  }
  return cases;
}

/** A result as one line of the run digest: sha256:<hex>, refuse:<code> or sink:<code>. */
export function outcomeLine(r) {
  if (r.output) return `sha256:${sha256(r.output)}`;
  if (r.refused !== undefined) return `refuse:${r.refused}`;
  return `sink:${r.sink}`;
}

/** Whether a result is the one the case states. */
export function holds(c, r) {
  if (c.expect.sha256 !== undefined) return !!r.output && sha256(r.output) === c.expect.sha256;
  return r.refused === c.expect.refuse;
}

/** The check of one run: each case its corpus outcome, and the run digest. */
export function judge(cases, results) {
  const lines = [];
  let wrong = 0;
  const report = [];
  cases.forEach((c, i) => {
    const r = results[i];
    const line = outcomeLine(r);
    lines.push(`${c.name} ${line}\n`);
    if (!holds(c, r)) {
      wrong++;
      const want = c.expect.sha256 !== undefined ? `sha256:${c.expect.sha256}` : `refuse:${c.expect.refuse}`;
      report.push(`  ${c.name}: ${line}${r.detail ? ` (${r.detail})` : ''}, not ${want}`);
    }
  });
  return { wrong, report, digest: sha256(Buffer.from(lines.join(''), 'utf8')) };
}