// lib/profiles/phase-signal-resolver.mjs
// v5.1.1 — extract per-phase signal from a brief's frontmatter.
//
// Decision A wiring: commands invoke this helper via Bash CLI shim
// (`node lib/profiles/phase-signal-resolver.mjs --brief <path> --phase <name> --json`)
// to obtain the {effort, model} pair for a specific pipeline phase.
//
// Sole source of truth for PHASE_SIGNAL_PHASES + EFFORT_LEVELS is
// lib/validators/brief-validator.mjs — re-imported here so the helper
// cannot drift from the schema validator.

import { readFileSync, existsSync } from 'node:fs';
import { parseDocument } from '../util/frontmatter.mjs';
import { PHASE_SIGNAL_PHASES, EFFORT_LEVELS } from '../validators/brief-validator.mjs';

/**
 * Resolve a brief's phase_signal entry for one phase.
 *
 * @param {object|null} briefFrontmatter  Parsed YAML frontmatter dict (or null/undefined).
 * @param {string} phase                  One of PHASE_SIGNAL_PHASES; anything else returns null.
 * @returns {{effort?: string, model?: string} | null}
 *
 * Never throws. Returns null on:
 *  - Falsy / non-object frontmatter
 *  - phase not in PHASE_SIGNAL_PHASES (e.g. 'brief' or 'continue')
 *  - Missing phase_signals array
 *  - No entry for the requested phase
 *
 * Returns partial `{effort}` (with `model: undefined`) when the signal omits model.
 */
export function resolvePhaseSignal(briefFrontmatter, phase) {
  if (!briefFrontmatter || typeof briefFrontmatter !== 'object') return null;
  if (typeof phase !== 'string' || !PHASE_SIGNAL_PHASES.includes(phase)) return null;
  const signals = briefFrontmatter.phase_signals;
  if (!Array.isArray(signals)) return null;
  for (const entry of signals) {
    if (entry && typeof entry === 'object' && entry.phase === phase) {
      const out = {};
      if ('effort' in entry && EFFORT_LEVELS.includes(entry.effort)) out.effort = entry.effort;
      if ('model' in entry) out.model = entry.model;
      return out;
    }
  }
  return null;
}

/**
 * Convenience wrapper: read a brief file, parse, and resolve a single phase.
 * Returns null on any read or parse failure (graceful degradation).
 */
export function resolvePhaseSignalFromFile(briefPath, phase) {
  if (typeof briefPath !== 'string' || briefPath.length === 0) return null;
  if (!existsSync(briefPath)) return null;
  let text;
  try { text = readFileSync(briefPath, 'utf-8'); } catch { return null; }
  const doc = parseDocument(text);
  if (!doc || !doc.valid) return null;
  const fm = doc.parsed && doc.parsed.frontmatter;
  return resolvePhaseSignal(fm, phase);
}

// CLI shim — mirrors lib/validators/brief-validator.mjs:168 pattern.
if (import.meta.url === `file://${process.argv[1]}`) {
  const args = process.argv.slice(2);
  const getArg = (name) => {
    const i = args.indexOf(name);
    return i >= 0 && i + 1 < args.length ? args[i + 1] : null;
  };
  const briefPath = getArg('--brief');
  const phase = getArg('--phase');
  if (!briefPath || !phase) {
    process.stderr.write('Usage: phase-signal-resolver.mjs --brief <path> --phase <name> [--json]\n');
    process.exit(2);
  }
  const result = resolvePhaseSignalFromFile(briefPath, phase);
  if (args.includes('--json')) {
    process.stdout.write(JSON.stringify(result) + '\n');
  } else if (result === null) {
    process.stdout.write('null\n');
  } else {
    const effort = 'effort' in result ? result.effort : '';
    const model = 'model' in result ? result.model : '';
    process.stdout.write(`effort=${effort} model=${model}\n`);
  }
  process.exit(0);
}