// ── canonical identifiers ────────────────────────────────────────────

const CANONICAL_KEY  = "confidence-engine-investigation";
const LEGACY_KEY     = "confidence-engine-session";
const SCHEMA_VERSION = 1;

import { restartSnapshot } from "../restart-investigation.js";

// Multi-Investigation key prefix (v0.60c)
const INVESTIGATION_PREFIX = "confidence-engine-investigation:";

// ── helpers ──────────────────────────────────────────────────────────

function safeGet(storage, key) {
  if (!storage || typeof storage.getItem !== "function") return null;
  try { return storage.getItem(key); } catch (_) { return null; }
}

function isPlainObject(value) {
  return (
    value !== null &&
    typeof value === "object" &&
    !Array.isArray(value) &&
    Object.prototype.toString.call(value) === "[object Object]"
  );
}

// ── loadInvestigation (identity-aware) ───────────────────────────────

/**
 * Returns the persisted investigation snapshot keyed by durable id
 * (normalised to current schema), or null when no usable state exists.
 *
 * When called without an id argument, reads from the legacy singleton key
 * for backward-compatible consumers that have not yet migrated.
 */
export function loadInvestigation(id) {
  const storage = _getTargetStorage();
  if (!storage) return null;

  // — identity-aware contract: select by durable id —
  if (id != null) {
    const raw = safeGet(storage, `${INVESTIGATION_PREFIX}${id}`);
    if (raw === null) return null;
    try {
      const parsed = JSON.parse(raw);
      if (isPlainObject(parsed)) {
        if (!("schemaVersion" in parsed)) parsed.schemaVersion = SCHEMA_VERSION;
        return parsed;
      }
    } catch (_) { return null; }
    return null;
  }

  // — backward-compatible singleton path (no id supplied) —
  // 1 – canonical key first
  let raw = safeGet(storage, CANONICAL_KEY);
  if (raw !== null) {
    try {
      const parsed = JSON.parse(raw);
      if (isPlainObject(parsed)) {
        if (!("schemaVersion" in parsed)) parsed.schemaVersion = SCHEMA_VERSION;
        return parsed;
      }
    } catch (_) { /* malformed — fall through to legacy */ }
  }

  // 2 – legacy fallback
  const legacyStorage = _getLegacyStorage();
  if (!legacyStorage) return null;

  raw = safeGet(legacyStorage, LEGACY_KEY);
  if (raw === null) return null;
  let parsed;
  try {
    parsed = JSON.parse(raw);
  } catch (_) { return null; }

  if (!isPlainObject(parsed)) return null;

  // Normalise schemaVersion for legacy data
  if (!("schemaVersion" in parsed)) parsed.schemaVersion = SCHEMA_VERSION;

  // Migrate into canonical key
  _persist(storage, CANONICAL_KEY, JSON.stringify(parsed));

  return parsed;
}

// ── saveInvestigation (identity-aware) ───────────────────────────────

/**
 * Persists the supplied snapshot under its durable id key.
 * The caller's object is never mutated.
 *
 * When called without an id argument, writes to the legacy singleton key
 * for backward-compatible consumers that have not yet migrated.
 */
export function saveInvestigation(snapshot, id) {
  const storage = _getTargetStorage();
  if (!storage) return; // silently no-op in non-browser

  try {
    const record = JSON.parse(JSON.stringify(snapshot));
    record.schemaVersion = SCHEMA_VERSION;
    const key = id != null ? `${INVESTIGATION_PREFIX}${id}` : CANONICAL_KEY;
    _persist(storage, key, JSON.stringify(record));
  } catch (_) { /* storage errors must not crash caller */ }
}

// ── clearInvestigation (identity-aware) ──────────────────────────────

/**
 * Removes a specific investigation by durable id.
 * When called without an id, clears the legacy singleton keys only.
 */
export function clearInvestigation(id) {
  const storage = _getTargetStorage();
  if (!storage) return;
  if (id != null) {
    try { storage.removeItem(`${INVESTIGATION_PREFIX}${id}`); } catch (_) {}
  } else {
    try { storage.removeItem(CANONICAL_KEY); } catch (_) {}
    const legacyStorage = _getLegacyStorage();
    if (legacyStorage) {
      try { legacyStorage.removeItem(LEGACY_KEY); } catch (_) {}
    }
  }
}

// ── listInvestigations (durable-ID only) ───────────────────────

/**
 * Enumerates all durable-ID Investigation records and returns lightweight summaries.
 * Skips malformed entries; excludes legacy singleton, sessionStorage state, unrelated keys.
 */
export function listInvestigations() {
  const storage = _getTargetStorage();
  if (!storage) return [];

  const summaries = [];

  for (let i = 0; i < storage.length; i++) {
    const key = storage.key(i);
    if (!key || !key.startsWith(INVESTIGATION_PREFIX)) continue;

    try {
      const raw = safeGet(storage, key);
      if (!raw) continue;
      const record = JSON.parse(raw);
      if (!isPlainObject(record)) continue;
      if (!record.id) continue;

      summaries.push({
        id: record.id,
        scenario: record.scenario ?? null,
        updatedAt: record.updatedAt ?? null,
        investigationRevision: record.investigationRevision ?? 0,
        reportExists: !!record.investigationReport,
        reportGeneratedFromRevision: record.investigationReport
          ? record.investigationReport.generatedFromRevision ?? null
          : null,
      });
    } catch (_) {
      // Malformed durable-ID entry — skip silently
    }
  }

  summaries.sort((a, b) => {
    const ta = a.updatedAt ?? "";
    const tb = b.updatedAt ?? "";
    if (ta > tb) return -1;
    if (ta < tb) return 1;
    return a.id > b.id ? -1 : 1;
  });

  return summaries;
}

// ── restartInvestigation (semantic reset within container) ───────────

/**
 * Resets the Investigation to a clean state suitable for a new reasoning pass.
 *
 * Preserved: id, scenario, schemaVersion (container-level identity/framing).
 * Reset: situationGraph → null, selectedQuestion → null, summary → null,
 *        focusedContributions → [], findings → [], investigationReport → null,
 *        investigationRevision → 0, updatedAt → new ISO timestamp.
 */
export function restartInvestigation(id) {
  const storage = _getTargetStorage();
  if (!storage) return;

  try {
    const key = id != null ? `${INVESTIGATION_PREFIX}${id}` : CANONICAL_KEY;
    const raw = safeGet(storage, key);
    if (raw === null) return; // nothing to restart
    const record = JSON.parse(raw);
    if (!isPlainObject(record)) return;

    _persist(storage, key, JSON.stringify(restartSnapshot(record)));
  } catch (_) { /* storage errors must not crash caller */ }
}

// ── internals ────────────────────────────────────────────────────────

function _persist(storage, key, value) {
  try { storage.setItem(key, value); } catch (_) {}
}

function _getTargetStorage() {
  if (typeof globalThis.window === "undefined") return null;
  const s = globalThis.window.localStorage;
  if (!s || typeof s.getItem !== "function") return null;
  return s;
}

function _getLegacyStorage() {
  if (typeof globalThis.window === "undefined") return null;
  const s = globalThis.window.sessionStorage;
  if (!s || typeof s.getItem !== "function") return null;
  return s;
}