// lib/plan/synthesis-digest-schema.mjs
// Digest-output JSON schema contract for the synthesis-agent (NW3 / S12).
//
// The synthesis-agent (agents/synthesis-agent.md) ingests the trekplan Phase-5/7
// exploration outputs and emits a trailing fenced ```json block carrying the
// findings DIGEST that main currently writes inline in Phase 7. Shape:
//
//   { "agent": "synthesis-agent",
//     "task": "<task being planned>",
//     "architecture_model": "<prose mental model of the codebase>",
//     "reusable_code":   [ { ref, note? }, ... ],
//     "contradictions":  [ "<overlap/contradiction between agents>", ... ],
//     "risks":           [ { risk, severity? }, ... ],
//     "gaps":            [ "<unknown → becomes a plan assumption>", ... ],
//     "sources":         [ { finding, origin: "codebase" | "research" }, ... ] }
//
// This codifies the contract so a delegated synthesis path could VALIDATE the
// digest (not merely JSON.parse it) and re-ask on schema failure, and so the
// measurement harness has a fixed quality contract to compare inline-vs-delegated
// digests against.
//
// Load-bearing fields (what Phase 8 deep-planning consumes): task,
// architecture_model, and the five synthesis arrays. Each `sources` entry must
// be origin-tagged codebase|research (Phase 7 rule 7). Descriptive fields and
// unknown top-level keys are tolerated (forward-compat, mirroring
// review-validator.mjs / findings-schema.mjs).
//
// 3-layer pattern (Content → Raw-text → CLI shim) mirroring the other validators.

import { readFileSync, existsSync } from 'node:fs';
import { issue, fail } from '../util/result.mjs';

// Origin tag for every synthesised finding (Phase 7 rule 7: codebase vs research).
export const ORIGIN_VALUES = Object.freeze(['codebase', 'research']);

// The fields Phase 8 depends on. Descriptive fields (note/severity) are not here
// on purpose: their absence should not trigger a re-ask.
export const DIGEST_REQUIRED_FIELDS = Object.freeze([
  'task',
  'architecture_model',
  'reusable_code',
  'contradictions',
  'risks',
  'gaps',
  'sources',
]);

// The five synthesis arrays + their stable not-an-array error codes.
const ARRAY_FIELDS = Object.freeze([
  ['reusable_code', 'DIGEST_REUSABLE_NOT_ARRAY'],
  ['contradictions', 'DIGEST_CONTRADICTIONS_NOT_ARRAY'],
  ['risks', 'DIGEST_RISKS_NOT_ARRAY'],
  ['gaps', 'DIGEST_GAPS_NOT_ARRAY'],
  ['sources', 'DIGEST_SOURCES_NOT_ARRAY'],
]);

// Last fenced ```json … ``` block, so prose above it never confuses the parser.
const JSON_FENCE_GLOBAL = /```json[ \t]*\r?\n([\s\S]*?)```/gi;

/**
 * Extract the inner body of the LAST fenced `json` block in `text`.
 * @param {string} text
 * @returns {string|null} the JSON source, or null if no json fence is present.
 */
export function extractDigestBlock(text) {
  if (typeof text !== 'string') return null;
  JSON_FENCE_GLOBAL.lastIndex = 0;
  let last = null;
  let m;
  while ((m = JSON_FENCE_GLOBAL.exec(text)) !== null) {
    last = m[1];
  }
  return last;
}

function isNonEmptyString(v) {
  return typeof v === 'string' && v.length > 0;
}

/**
 * Validate an already-parsed digest payload against the schema.
 * Accumulates every error (so a re-ask can name all problems at once).
 * @param {unknown} payload
 * @returns {import('../util/result.mjs').Result}
 */
export function validateDigest(payload) {
  if (payload === null || typeof payload !== 'object' || Array.isArray(payload)) {
    return fail(issue(
      'DIGEST_NOT_OBJECT',
      `Digest must be a JSON object, got ${Array.isArray(payload) ? 'array' : typeof payload}`,
    ));
  }

  const errors = [];
  const warnings = [];

  if (!isNonEmptyString(payload.agent)) {
    warnings.push(issue('DIGEST_MISSING_AGENT', 'Digest should carry a non-empty "agent" name'));
  }

  if (!isNonEmptyString(payload.task)) {
    errors.push(issue('DIGEST_MISSING_TASK', 'Digest "task" must be a non-empty string'));
  }

  if (!isNonEmptyString(payload.architecture_model)) {
    errors.push(issue(
      'DIGEST_MISSING_ARCHITECTURE',
      'Digest "architecture_model" must be a non-empty string (the synthesised mental model)',
    ));
  }

  for (const [field, code] of ARRAY_FIELDS) {
    if (!Array.isArray(payload[field])) {
      errors.push(issue(code, `Digest "${field}" must be an array, got ${typeof payload[field]}`));
    }
  }

  // Origin-tag check — only when sources actually is an array.
  if (Array.isArray(payload.sources)) {
    payload.sources.forEach((s, i) => {
      const origin = s && typeof s === 'object' ? s.origin : undefined;
      if (!ORIGIN_VALUES.includes(origin)) {
        errors.push(issue(
          'DIGEST_SOURCE_BAD_ORIGIN',
          `sources[${i}].origin must be one of ${ORIGIN_VALUES.join('|')}, got ${JSON.stringify(origin)}`,
          'Tag every synthesised finding as codebase or research (Phase 7 rule 7).',
          `sources[${i}]`,
        ));
      }
    });
  }

  return { valid: errors.length === 0, errors, warnings, parsed: payload };
}

/**
 * Validate a synthesis-agent's raw output: extract the last json fence, parse it,
 * then schema-validate. Parse-stage failures get stable codes so they flow
 * through the same bounded re-ask path as schema failures.
 * @param {string} rawText
 * @returns {import('../util/result.mjs').Result}
 */
export function validateAgentOutput(rawText) {
  const block = extractDigestBlock(rawText);
  if (block === null) {
    return fail(issue(
      'DIGEST_NO_JSON_BLOCK',
      'No trailing fenced ```json block found in synthesis-agent output',
      'The synthesis-agent must end its output with a single ```json digest block.',
    ));
  }
  let parsed;
  try {
    parsed = JSON.parse(block);
  } catch (e) {
    return fail(issue('DIGEST_PARSE_ERROR', `Digest JSON block did not parse: ${e.message}`));
  }
  return validateDigest(parsed);
}

// ---- CLI shim ----------------------------------------------------------------

if (import.meta.url === `file://${process.argv[1]}`) {
  const args = process.argv.slice(2);
  const filePath = args.find((a) => !a.startsWith('--'));
  if (!filePath) {
    process.stderr.write('Usage: synthesis-digest-schema.mjs [--json] <agent-output.txt|.md>\n');
    process.exit(2);
  }
  if (!existsSync(filePath)) {
    process.stderr.write(`synthesis-digest-schema: file not found: ${filePath}\n`);
    process.exit(2);
  }
  const r = validateAgentOutput(readFileSync(filePath, 'utf-8'));
  if (args.includes('--json')) {
    process.stdout.write(JSON.stringify({ valid: r.valid, errors: r.errors, warnings: r.warnings }, null, 2) + '\n');
  } else {
    process.stdout.write(`synthesis-digest-schema: ${r.valid ? 'PASS' : 'FAIL'} ${filePath}\n`);
    for (const e of r.errors) process.stderr.write(`  ERROR  [${e.code}] ${e.message}\n`);
    for (const w of r.warnings) process.stderr.write(`  WARN   [${w.code}] ${w.message}\n`);
  }
  process.exit(r.valid ? 0 : 1);
}