/**
 * correction-memory.ts
 *
 * Reads and writes the per-workspace attempt history at
 * ~/.pisces/attempt-history.json.
 *
 * Provides:
 *  - appendAttempt() — validated write with silent drop on policy violation
 *  - getRecentGaps()  — compact gap summary for injection into calibration context
 */

import * as fs from "fs";
import * as path from "path";
import * as os from "os";
import { validateWrite, validateInject } from "./memory-policy";

// ─── Types ─────────────────────────────────────────────────────────────────

export interface AttemptRecord {
  /** Short ID — timestamp-based base36 for easy sorting */
  id: string;
  /** ISO 8601 timestamp */
  timestamp: string;
  /** Skill that triggered the attempt (e.g. "attempt") */
  skillName: string;
  /** Classified attempt type (e.g. "code", "essay", "generic") */
  attemptType: string;
  /** What the learner was trying to achieve (truncated to 200 chars for storage) */
  goal?: string;
  /** Specific gaps identified — populated after model grades (initially empty) */
  gaps: string[];
  /** Strengths identified — populated after model grades (initially empty) */
  strengths: string[];
  /** 0–100 composite score — set after model grades (optional at capture time) */
  score?: number;
}

// ─── Storage ───────────────────────────────────────────────────────────────

const HISTORY_DIR = path.join(os.homedir(), ".pisces");
const HISTORY_FILE = path.join(HISTORY_DIR, "attempt-history.json");
// Keep bounded to avoid unbounded growth
const MAX_RECORDS = 200;
// Gap summary budget (proxy for ≈150 tokens at ~4 chars/token)
const DEFAULT_MAX_CHARS = 600;

function load(): AttemptRecord[] {
  try {
    if (!fs.existsSync(HISTORY_FILE)) return [];
    return JSON.parse(fs.readFileSync(HISTORY_FILE, "utf-8")) as AttemptRecord[];
  } catch {
    return [];
  }
}

function save(records: AttemptRecord[]): void {
  try {
    fs.mkdirSync(HISTORY_DIR, { recursive: true });
    fs.writeFileSync(HISTORY_FILE, JSON.stringify(records.slice(-MAX_RECORDS), null, 2));
  } catch {
    // Non-fatal — history is valuable but never critical
  }
}

// ─── Public API ────────────────────────────────────────────────────────────

/**
 * Appends an attempt record to history after policy validation.
 * Silently drops the record if the policy check fails.
 */
export function appendAttempt(record: AttemptRecord): void {
  if (!validateWrite(record).allowed) return;
  const records = load();
  records.push(record);
  save(records);
}

/**
 * Updates gaps, strengths, and score on an existing record by ID.
 * Called by the turn_end write-back path after the model grades the attempt.
 * No-ops silently if the record is not found.
 */
export function updateAttemptRecord(
  id: string,
  updates: { gaps?: string[]; strengths?: string[]; score?: number }
): void {
  const records = load();
  const idx = records.findIndex((r) => r.id === id);
  if (idx === -1) return;
  records[idx] = { ...records[idx], ...updates };
  save(records);
}

/**
 * Returns a compact, deduplicated summary of unresolved gaps from recent
 * attempts, truncated to `maxChars` to fit within a context window budget.
 * Returns an empty string if there are no gaps or the summary fails policy.
 */
export function getRecentGaps(maxChars = DEFAULT_MAX_CHARS): string {
  const records = load();
  if (records.length === 0) return "";

  // Collect all gaps newest-first, then deduplicate
  const gaps: string[] = [];
  for (let i = records.length - 1; i >= 0; i--) {
    for (const gap of records[i].gaps) {
      gaps.push(gap);
    }
  }
  if (gaps.length === 0) return "";

  const unique = [...new Set(gaps)];

  // Build summary within budget
  const lines: string[] = [];
  let used = 0;
  const header = "Recent gaps to address:\n";
  used += header.length;

  for (const gap of unique) {
    const line = `- ${gap}`;
    if (used + line.length + 1 > maxChars) break;
    lines.push(line);
    used += line.length + 1;
  }

  if (lines.length === 0) return "";

  const summary = header + lines.join("\n");
  return validateInject(summary).allowed ? summary : "";
}