// Renderer-side client for the encrypted local search index.
//
// The index is EVENT-DRIVEN: the renderer already holds the live JMAP push
// connection (WebSocket -> SSE -> polling, `lib/jmap/client.ts`'s
// setupPushNotifications), so the moment a StateChange announces new mail, a
// calendar change, a contact edit or a file upload, this posts to the reindex
// route. No polling loop, no background worker, no long-lived credential -
// just one more authenticated fetch from the place the push already arrives.
//
// Every function here is best-effort and never throws: a search index failing
// to update must never break the mail UI.

import { apiFetch } from '@/lib/browser-navigation';
import { debug } from '@/lib/debug';
import type { StateChange } from '@/lib/jmap/types';

export type IndexContentType = 'mail' | 'calendar' | 'contact' | 'file';

export interface IndexRunResult {
  ok: boolean;
  written?: Partial<Record<IndexContentType, number>>;
  skipped?: IndexContentType[];
  errors?: Array<{ contentType: IndexContentType; message: string }>;
  durationMs?: number;
  /** Set when the feature isn't available (not the desktop shell, no keyring, no binding). */
  unavailable?: boolean;
  error?: string;
}

/**
 * Maps JMAP `StateChange` type keys onto our content types.
 *
 * The transport is already type-generic - the WebSocket handler
 * (`client.ts:6308-6316`) and the SSE handler (`:6505`) pass the whole
 * `changed` map through untouched, and the WS subscribes with
 * `dataTypes: null` (every type) - so anything the server pushes arrives here.
 *
 * `Mailbox` is deliberately NOT mapped: a Mailbox state change is usually just
 * an unread-count move, and it fires constantly. `Email` covers the cases that
 * change indexable content.
 */
const STATE_TYPE_TO_CONTENT: Record<string, IndexContentType> = {
  Email: 'mail',
  Calendar: 'calendar',
  CalendarEvent: 'calendar',
  ContactCard: 'contact',
  AddressBook: 'contact',
  FileNode: 'file',
};

export function contentTypesFromStateChange(change: StateChange): IndexContentType[] {
  const out = new Set<IndexContentType>();
  for (const perAccount of Object.values(change.changed ?? {})) {
    for (const stateType of Object.keys(perAccount ?? {})) {
      const mapped = STATE_TYPE_TO_CONTENT[stateType];
      if (mapped) out.add(mapped);
    }
  }
  return [...out];
}

export interface IndexRequestOptions {
  types?: readonly IndexContentType[];
  /**
   * Per-type ids to index. Supply them whenever the renderer already knows
   * which objects changed - it turns the call into a couple of `Foo/get`s
   * instead of a windowed query. Mail is the frequent case and the one where
   * this matters.
   */
  ids?: Partial<Record<IndexContentType, string[]>>;
  /** Backfill the recent window for every supported type, and prune. */
  catchUp?: boolean;
  /** Retention window in days, or null to keep everything. Omitted = server
   *  default (1 year). Bounds the fetch AND the prune together. */
  windowDays?: number | null;
  /** Cookie slot of the account to index. Defaults to the server's first signed-in slot. */
  slot?: number;
}

let inFlight: Promise<IndexRunResult> | null = null;
/** Set once the server says the feature isn't there, so we stop asking. */
let knownUnavailable = false;

/**
 * Posts one index request. Single-flighted: a burst of deliveries coalesces
 * into the in-flight call rather than queueing N overlapping SQLite writers.
 */
export async function requestIndex(options: IndexRequestOptions = {}): Promise<IndexRunResult> {
  if (knownUnavailable) return { ok: false, unavailable: true };
  if (inFlight) return inFlight;

  const query = typeof options.slot === 'number' ? `?slot=${options.slot}` : '';
  const run = (async (): Promise<IndexRunResult> => {
    try {
      const response = await apiFetch(`/api/offline/reindex${query}`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          types: options.types,
          ids: options.ids,
          catchUp: options.catchUp === true,
          ...(options.windowDays !== undefined ? { windowDays: options.windowDays } : {}),
        }),
      });

      // 404 = not the desktop shell (or the feature is gated off). Permanent for
      // this page load; stop asking so a busy mailbox doesn't post per delivery.
      if (response.status === 404) {
        knownUnavailable = true;
        return { ok: false, unavailable: true };
      }
      if (response.status === 503) {
        // No keyring / no native binding / no key channel. Also permanent for
        // this session, and the message is worth surfacing in Settings.
        knownUnavailable = true;
        const body = await response.json().catch(() => ({}));
        return { ok: false, unavailable: true, error: body?.error };
      }
      if (!response.ok) {
        const body = await response.json().catch(() => ({}));
        return { ok: false, error: body?.error || `HTTP ${response.status}` };
      }
      const body = await response.json();
      debug.log('push', '[index] reindex done', body?.written, body?.errors);
      return {
        ok: true,
        written: body?.written,
        skipped: body?.skipped,
        errors: body?.errors,
        durationMs: body?.durationMs,
      };
    } catch (error) {
      return { ok: false, error: error instanceof Error ? error.message : String(error) };
    } finally {
      inFlight = null;
    }
  })();

  inFlight = run;
  return run;
}

/**
 * The event-driven entry point, called from the push handler.
 *
 * `mailIds` lets the caller hand over the ids it already has (the refreshed
 * mailbox page), so the frequent mail case costs one `Email/get` rather than a
 * 30-day query. The other three types are rare events (a contact edit, a file
 * upload, a calendar change), so they fall back to their own bounded queries.
 */
export function indexOnStateChange(
  change: StateChange,
  opts: { mailIds?: string[]; slot?: number } = {},
): void {
  if (knownUnavailable) return;
  const types = contentTypesFromStateChange(change);
  if (types.length === 0) return;

  const ids: Partial<Record<IndexContentType, string[]>> = {};
  if (types.includes('mail') && opts.mailIds && opts.mailIds.length > 0) {
    ids.mail = opts.mailIds.slice(0, 100);
  }

  // Fire-and-forget on purpose: this runs inside the push handler, and the mail
  // UI must not wait on a search index.
  void requestIndex({ types, ids: Object.keys(ids).length > 0 ? ids : undefined, slot: opts.slot });
}

/**
 * Launch-time catch-up: backfills whatever changed while the app was closed,
 * for which no push event was ever delivered. Also the recovery path for the
 * polling transport, which has no signal for contacts or files at all
 * (`client.ts`'s buildStatePollingRequest polls Mailbox/Email/Calendar/
 * CalendarEvent/SieveScript only).
 */
export async function catchUpIndex(slot?: number, windowDays?: number | null): Promise<IndexRunResult> {
  return requestIndex({ catchUp: true, slot, windowDays });
}

// ── Retention setting ────────────────────────────────────────────────────
// Renderer-owned: the renderer already drives every index run, so keeping the
// choice here avoids a second source of truth on the server that could drift
// out of step with what the user last picked.

const RETENTION_KEY = 'vncmail:index:retention-days';
/** Matches DEFAULT_RETENTION_WINDOW_DAYS in lib/mail-index/reindex.ts. */
export const DEFAULT_RETENTION_DAYS = 365;

/** `null` = keep everything. */
export function getRetentionDays(): number | null {
  if (typeof window === 'undefined') return DEFAULT_RETENTION_DAYS;
  const raw = window.localStorage.getItem(RETENTION_KEY);
  if (raw === null) return DEFAULT_RETENTION_DAYS;
  if (raw === 'forever') return null;
  const parsed = Number.parseInt(raw, 10);
  return Number.isFinite(parsed) ? parsed : DEFAULT_RETENTION_DAYS;
}

export function setRetentionDays(days: number | null): void {
  if (typeof window === 'undefined') return;
  window.localStorage.setItem(RETENTION_KEY, days === null ? 'forever' : String(days));
}

export interface IndexStats {
  contentType: string;
  count: number;
  newest: string | null;
  indexedAt: number | null;
}

/** Reads per-type counts without searching. Used by the Settings panel. */
export async function fetchIndexStats(slot?: number): Promise<IndexStats[] | null> {
  const slotQuery = typeof slot === 'number' ? `&slot=${slot}` : '';
  try {
    const response = await apiFetch(`/api/offline/search?stats=true${slotQuery}`);
    if (!response.ok) return null;
    const body = await response.json();
    return Array.isArray(body?.stats) ? (body.stats as IndexStats[]) : [];
  } catch {
    return null;
  }
}

/** Resets the "don't ask again" latch - e.g. after the user signs in again. */
export function resetIndexAvailability(): void {
  knownUnavailable = false;
}