#!/usr/bin/env node
/**
 * Stop-event hook for brain governance observer (B3).
 * Reads JSON context from stdin (Claude Code Stop-event hook contract).
 * When the context provides `transcript_path`, the episode is derived from
 * the real session transcript via parseTranscript; otherwise it falls back
 * to best-effort defaults. Builds an episode with 5 mandatory fields
 * including primary_rationale (7 sub-fields per spec v1.1 §5.2.1),
 * sanitizes via PII filter, appends to docs/observer/episodes-YYYY-MM.jsonl.
 *
 * Never blocks the Stop-event — exits 0 on any error.
 *
 * Security Guidance #40: NO exec/execSync — pure fs + sanitize.
 * Per Pravila §16.2 + ADR-011 + spec v1.1 §5.2.1.
 */

import { appendFileSync, existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
import { join } from 'path';
import { sanitize, sanitizeWithCount } from './observer-pii-filter.mjs';
import { parseTranscript, extractLastUserPromptText } from './observer-transcript-parser.mjs';
import { detectMethodDirected, loadKnownNodes } from './observer-routing-detector.mjs';

const REQUIRED_FIELDS = ['task_id', 'timestamps', 'path_type', 'outcome', 'primary_rationale'];
const V2_FIELDS = [
  'schema_version',
  'decision_provenance',
  'environment',
  'task_size',
  'task_ref',
  // C-7: prompt_signal + events are always produced by parser and buildEpisodeFromContext,
  // but were previously unvalidated → a ctx-fallback path that dropped them would silently
  // write a malformed episode. Strict validation closes that gap.
  'prompt_signal',
  'events',
];
const OBSERVER_ERROR_FIELDS = ['schema_version', 'error_message', 'timestamps', 'task_id'];

const RATIONALE_FIELDS = [
  'step',
  'node_chosen',
  'triggers_matched',
  'candidates_considered',
  'boundaries_applied',
  'hard_floor',
  'task_classification',
];

/** Update the monthly PII counter JSON with counts from a single episode write. */
function bumpPiiCounter(counts, baseDir, month) {
  const counterPath = join(baseDir, 'docs', 'observer', '.pii-counters.json');
  let store = {};
  if (existsSync(counterPath)) {
    try { store = JSON.parse(readFileSync(counterPath, 'utf-8')); } catch { store = {}; }
  }
  store[month] = store[month] || {};
  for (const [k, n] of Object.entries(counts)) {
    if (n > 0) store[month][k] = (store[month][k] || 0) + n;
  }
  try { writeFileSync(counterPath, JSON.stringify(store, null, 2) + '\n', 'utf-8'); }
  catch { /* counter is informational — never fail the Stop-event */ }
}

function validateRationale(rationale) {
  for (const f of RATIONALE_FIELDS) {
    if (rationale[f] === undefined) {
      throw new Error(`primary_rationale field missing: ${f}`);
    }
  }
}

/**
 * Append a single episode to the monthly JSONL file.
 * Validates either a full schema-v2 episode or a minimal observer_error marker.
 * @param {object} episode - The episode object.
 * @param {string} baseDir - Repository root (default: process.cwd()).
 * @param {string} month   - YYYY-MM string for the file name (default: current UTC month).
 */
export function appendEpisode(episode, baseDir = process.cwd(), month = currentMonth()) {
  const dir = join(baseDir, 'docs', 'observer');
  if (!existsSync(dir)) {
    mkdirSync(dir, { recursive: true });
  }
  const file = join(dir, `episodes-${month}.jsonl`);

  if (episode && episode.observer_error === true) {
    for (const f of OBSERVER_ERROR_FIELDS) {
      if (episode[f] === undefined) {
        throw new Error(`observer_error marker field missing: ${f}`);
      }
    }
    const { sanitized: sanitizedErr, counts: countsErr } = sanitizeWithCount(episode);
    appendFileSync(file, JSON.stringify(sanitizedErr) + '\n', 'utf-8');
    bumpPiiCounter(countsErr, baseDir, month);
    return;
  }

  for (const f of REQUIRED_FIELDS) {
    if (episode[f] === undefined) {
      throw new Error(`required field missing: ${f}`);
    }
  }
  for (const f of V2_FIELDS) {
    if (episode[f] === undefined) {
      throw new Error(`schema v2 field missing: ${f}`);
    }
  }
  if (episode.schema_version !== 2) {
    throw new Error(`schema_version must be 2 (got ${episode.schema_version})`);
  }
  validateRationale(episode.primary_rationale);

  const { sanitized, counts } = sanitizeWithCount(episode);
  appendFileSync(file, JSON.stringify(sanitized) + '\n', 'utf-8');
  bumpPiiCounter(counts, baseDir, month);
}

/**
 * Build a well-formed schema-v2 episode from a Claude Code Stop-event context.
 * Preferred path: when `transcriptText` is supplied, the episode is derived
 * from the real session transcript via parseTranscript. Fallback path: v2
 * defaults from `ctx` (an explicit ctx.primary_rationale is preserved verbatim).
 * @param {object} ctx - Raw context from stdin (may be partial).
 * @param {string|null} transcriptText - Raw transcript JSONL, if readable.
 * @returns {object} v2 episode.
 */
export function buildEpisodeFromContext(ctx = {}, transcriptText = null) {
  if (transcriptText) {
    return parseTranscript(transcriptText, ctx.session_id || ctx.sessionId || ctx.task_id);
  }
  const sid = ctx.session_id || ctx.sessionId || ctx.task_id || `unknown-${Date.now()}`;
  const now = new Date().toISOString();
  return {
    schema_version: 2,
    task_id: sid,
    task_ref: sid,
    timestamps: {
      started_at: ctx.started || ctx.started_at || now,
      ended_at: ctx.ended || ctx.ended_at || now,
    },
    path_type: ctx.path_type || 'regulated',
    outcome: ctx.result || ctx.outcome || 'unknown',
    prompt_signal: ctx.prompt_signal || 'neutral',
    decision_provenance: ctx.decision_provenance || { kind: 'autonomous', claude_would_have_chosen: null },
    environment: ctx.environment || {
      economy_level: null,
      model: null,
      post_compaction: false,
      session_turn: 0,
      parallel_session: false,
    },
    task_size: ctx.task_size || { tool_calls: 0, files_touched: 0, files: [] },
    primary_rationale: ctx.primary_rationale || {
      step: 1,
      node_chosen: ctx.node_chosen || ctx.skill_id || 'unknown',
      triggers_matched: [],
      candidates_considered: [],
      boundaries_applied: [],
      hard_floor: ctx.hard_floor || { invoked: false, rules: [] },
      task_classification: ctx.task_classification || 'other',
    },
    events: ctx.events || [],
  };
}

/**
 * Build a minimal observer_error marker — written instead of a silent skip
 * when the Stop-hook fails internally (spec §3 / §5.2).
 */
export function buildObserverError(ctx = {}, err) {
  const now = new Date().toISOString();
  return {
    schema_version: 2,
    observer_error: true,
    error_message: String((err && err.message) || err),
    timestamps: { started_at: now, ended_at: now },
    task_id: ctx.session_id || ctx.sessionId || ctx.task_id || `unknown-${Date.now()}`,
  };
}

/**
 * Routing-gate decision (spec §5.1, 3a). Pure — the CLI calls this.
 * Blocks the Stop-event (decision: block) when the user dictated a method
 * but the turn carries no routing tag. Skipped when stop_hook_active is true
 * (the gate fires at most once per turn — no infinite loop).
 * @returns {{block: boolean, reason: string|null}}
 */
export function routingGateDecision(episode, promptText, knownNodes, stopHookActive) {
  if (stopHookActive) return { block: false, reason: null };
  // user_chose_from_options is collaborative-choice from Claude-offered options —
  // not an externally directed method; no routing tag required (spec §11.4).
  if (episode && episode.decision_provenance && episode.decision_provenance.kind === 'user_chose_from_options') {
    return { block: false, reason: null };
  }
  const det = detectMethodDirected(promptText, knownNodes);
  if (!det.directed) return { block: false, reason: null };
  if (episode && episode.decision_provenance && episode.decision_provenance.kind === 'user_directed_method') {
    return { block: false, reason: null };
  }
  return {
    block: true,
    reason:
      `[observer routing-gate] Похоже, метод навязан пользователем (узел "${det.node}"), ` +
      `но routing-тег в этом ходе отсутствует. Добавь в свой ответ ровно одну строку:\n` +
      `<!-- routing: provenance=user_directed_method node=${det.node} ` +
      `counterfactual=<узел, который ты выбрал бы автономно> -->`,
  };
}

function currentMonth() {
  const d = new Date();
  return `${d.getUTCFullYear()}-${String(d.getUTCMonth() + 1).padStart(2, '0')}`;
}

// CLI entry point: read JSON context from stdin (Claude Code Stop-event hook contract)
if (process.argv[1] && process.argv[1].replace(/\\/g, '/').endsWith('/observer-stop-hook.mjs')) {
  const chunks = [];
  process.stdin.on('data', (c) => chunks.push(c));
  process.stdin.on('end', () => {
    let ctx = {};
    try {
      const raw = Buffer.concat(chunks).toString('utf-8');
      if (raw.trim()) ctx = JSON.parse(raw);
    } catch (_e) {
      // best-effort: build a minimal episode even if stdin is malformed
    }
    // Claude Code's Stop-event supplies transcript_path — the real source of
    // session data. Read it best-effort; fall back to ctx-only on any error.
    let transcriptText = null;
    const tp = ctx.transcript_path || ctx.transcriptPath;
    if (tp) {
      try {
        if (existsSync(tp)) transcriptText = readFileSync(tp, 'utf-8');
      } catch (_e) {
        transcriptText = null;
      }
    }
    try {
      const ep = buildEpisodeFromContext(ctx, transcriptText);
      // Always write the episode first — exit-0-safe (spec §5.1 step 1).
      appendEpisode(ep);
      // Then the routing-gate (spec §5.1 steps 2-4).
      if (transcriptText) {
        const promptText = extractLastUserPromptText(transcriptText);
        const gate = routingGateDecision(ep, promptText, loadKnownNodes(), ctx.stop_hook_active === true);
        if (gate.block) {
          process.stdout.write(JSON.stringify({ decision: 'block', reason: gate.reason }));
          process.exit(0);
        }
      }
      process.exit(0);
    } catch (err) {
      // Visible failure (spec §5.2): write an observer_error marker, never a silent skip.
      try {
        appendEpisode(buildObserverError(ctx, err));
      } catch (_e2) {
        // last-resort: even the marker failed — do not crash the Stop-event
      }
      console.error(`[observer-stop-hook] error: ${err.message}`);
      process.exit(0); // never block the Stop-event on an internal error
    }
  });
}