import {
  Capability,
  EventDirection,
  EventKind,
  MatrixCapabilities,
  WidgetEventCapability,
} from 'matrix-widget-api';

// Capability policy. Benign display capabilities are granted silently. Reading
// or sending events/state in the widget's OWN room can be granted by the user
// through the consent prompt (see classifyWidgetCapabilities). Everything else
// (other rooms' timelines, to-device, account data, uploads, user directory,
// delayed events, TURN servers) is always denied.
export const ALLOWED_WIDGET_CAPABILITIES: ReadonlySet<Capability> = new Set<Capability>([
  MatrixCapabilities.AlwaysOnScreen,
  MatrixCapabilities.RequiresClient,
  MatrixCapabilities.Screenshots,
]);

export const filterWidgetCapabilities = (requested: Set<Capability>): Set<Capability> =>
  new Set([...requested].filter((cap) => ALLOWED_WIDGET_CAPABILITIES.has(cap)));

export type WidgetUrlError = 'empty' | 'invalid' | 'not-https' | 'same-origin';

// A widget URL to ADD must be https and NOT our own origin: a same-origin frame
// with allow-same-origin + allow-scripts can break out of the sandbox against us.
export const validateWidgetUrl = (raw: string, appOrigin: string): WidgetUrlError | undefined => {
  const trimmed = raw.trim();
  if (!trimmed) return 'empty';
  let url: URL;
  try {
    url = new URL(trimmed);
  } catch {
    return 'invalid';
  }
  if (url.protocol !== 'https:') return 'not-https';
  if (url.origin === appOrigin) return 'same-origin';
  return undefined;
};

// Is an already-resolved (complete) widget URL safe to render in a sandboxed
// iframe that carries allow-same-origin? Rejects same-origin URLs (breakout).
export const isWidgetUrlSafe = (completeUrl: string, appOrigin: string): boolean => {
  try {
    return new URL(completeUrl).origin !== appOrigin;
  } catch {
    return false;
  }
};

export const generateWidgetId = (): string =>
  `lotus_${Date.now()}_${Math.random().toString(36).slice(2, 10)}`;

// State a widget may never write with the user's authority, even if approved:
// these change who can do what in the room, or its encryption/identity.
export const PROTECTED_STATE_TYPES: ReadonlySet<string> = new Set([
  'm.room.create',
  'm.room.power_levels',
  'm.room.join_rules',
  'm.room.history_visibility',
  'm.room.guest_access',
  'm.room.encryption',
  'm.room.member',
  'm.room.server_acl',
  'm.room.tombstone',
  'm.room.canonical_alias',
  'm.room.third_party_invite',
  'im.vector.modular.widgets',
  'm.widget',
]);

export type WidgetPermissionRequest = {
  capability: Capability;
  /** Plain-language description, e.g. "Send messages". */
  label: string;
  /** Sending as you (vs only reading). Shown with a warning tone. */
  sends: boolean;
};

export type ClassifiedCapabilities = {
  /** Granted without asking. */
  auto: Set<Capability>;
  /** Needs the user's OK. */
  ask: WidgetPermissionRequest[];
};

const FRIENDLY_EVENT_NAMES: Record<string, string> = {
  'm.room.message': 'messages',
  'm.reaction': 'reactions',
  'm.sticker': 'stickers',
  'm.room.redaction': 'message deletions',
  'm.room.name': 'the room name',
  'm.room.topic': 'the room topic',
  'm.room.avatar': 'the room avatar',
  'm.room.pinned_events': 'pinned messages',
  'm.room.member': 'the member list',
  'm.room.power_levels': 'room permissions',
};

const describeEventCapability = (cap: WidgetEventCapability): string => {
  const verb = cap.direction === EventDirection.Send ? 'Send' : 'See';
  const friendly = FRIENDLY_EVENT_NAMES[cap.eventType];
  const what =
    friendly ?? `“${cap.eventType}” ${cap.kind === EventKind.State ? 'state' : 'events'}`;
  let detail = '';
  if (cap.keyStr) {
    detail = cap.kind === EventKind.State ? ` (key “${cap.keyStr}”)` : ` of type “${cap.keyStr}”`;
  }
  if (cap.kind === EventKind.State && cap.direction === EventDirection.Send && friendly) {
    return `Change ${friendly}${detail}`;
  }
  return `${verb} ${what}${detail} in this room`;
};

/**
 * Split a widget's requested capabilities into those granted silently and
 * those the user may approve. Anything in neither list is denied outright.
 */
export const classifyWidgetCapabilities = (
  requested: Iterable<Capability>,
): ClassifiedCapabilities => {
  const list = [...requested];
  const auto = new Set(list.filter((cap) => ALLOWED_WIDGET_CAPABILITIES.has(cap)));
  const ask: WidgetPermissionRequest[] = [];
  WidgetEventCapability.findEventCapabilities(list).forEach((cap) => {
    if (cap.kind !== EventKind.Event && cap.kind !== EventKind.State) return;
    const sends = cap.direction === EventDirection.Send;
    if (sends && cap.kind === EventKind.State && PROTECTED_STATE_TYPES.has(cap.eventType)) return;
    ask.push({ capability: cap.raw, label: describeEventCapability(cap), sends });
  });
  return { auto, ask };
};

/**
 * Remembered approvals, per viewer (localStorage), keyed by room + widget id and
 * tied to the widget's URL: if the URL changes, the widget is asked again.
 */
export type StoredWidgetConsent = { url: string; allowed: Capability[]; denied: Capability[] };

export const widgetConsentKey = (roomId: string, widgetId: string): string =>
  `lotus.widgetConsent.${roomId}.${widgetId}`;

export const loadWidgetConsent = (
  roomId: string,
  widgetId: string,
  url: string,
): StoredWidgetConsent | undefined => {
  try {
    const raw = localStorage.getItem(widgetConsentKey(roomId, widgetId));
    if (!raw) return undefined;
    const parsed = JSON.parse(raw) as StoredWidgetConsent;
    if (parsed.url !== url || !Array.isArray(parsed.allowed) || !Array.isArray(parsed.denied)) {
      return undefined;
    }
    return parsed;
  } catch {
    return undefined;
  }
};

export const saveWidgetConsent = (
  roomId: string,
  widgetId: string,
  consent: StoredWidgetConsent,
) => {
  try {
    localStorage.setItem(widgetConsentKey(roomId, widgetId), JSON.stringify(consent));
  } catch {
    // Storage unavailable: the widget just asks again next time.
  }
};