/**
 * OpenChamber deep-link vocabulary — the single source of truth for the `openchamber://`
 * URL scheme used across every native entry point: notification taps, home-screen / lock-
 * screen widgets, and (later) Live Activities. Anything that wants to drive navigation
 * builds a URL with {@link buildDeepLink} and anything that receives one parses it with
 * {@link parseDeepLink} into a typed {@link DeepLinkIntent}; the navigation layer
 * (deepLinkNavigation) is the only place that knows how to *apply* an intent.
 *
 * Keep this file pure (no React, no stores, no Capacitor) so it can be imported from any
 * context — including, eventually, a tiny encoder shared with the native widget/extension.
 */

const DEEP_LINK_SCHEME = 'openchamber';

export type SessionsFilter = 'all' | 'attention' | 'recent';
export type ViewTarget = 'files' | 'mcp' | 'instances' | 'update';

/**
 * Every navigable destination the app exposes to the outside world. New widget/notification
 * ideas should add a variant here first, then teach deepLinkNavigation how to apply it —
 * that keeps the "blocks" composable without leaking ad-hoc URL parsing into features.
 */
export type DeepLinkIntent =
  | { type: 'session'; sessionId: string; directory?: string }
  | { type: 'new-session'; directory?: string; projectId?: string; agent?: string; model?: string }
  | { type: 'sessions'; filter?: SessionsFilter }
  | { type: 'status' }
  | { type: 'settings'; section?: string }
  | { type: 'changes'; path?: string; staged?: boolean }
  | { type: 'view'; target: ViewTarget };

const trimSlashes = (value: string): string => value.replace(/^\/+|\/+$/g, '');

const segmentsOf = (url: URL): string[] => {
  // Custom-scheme URLs put the first route token in `host` (openchamber://session/<id>),
  // but be tolerant of authority-less forms (openchamber:/session/<id>) where it lands in
  // the pathname instead.
  const pathSegments = trimSlashes(url.pathname).split('/').filter(Boolean);
  if (url.host) {
    return [url.host, ...pathSegments];
  }
  return pathSegments;
};

/**
 * Parse a raw `openchamber://…` string into a typed intent, or `null` if it isn't a
 * recognised OpenChamber deep link. Tolerant by design: unknown routes return `null`
 * rather than throwing, so callers can fall back without a try/catch.
 */
export function parseDeepLink(raw: string | null | undefined): DeepLinkIntent | null {
  if (typeof raw !== 'string' || raw.length === 0) {
    return null;
  }

  let url: URL;
  try {
    url = new URL(raw);
  } catch {
    return null;
  }

  if (url.protocol !== `${DEEP_LINK_SCHEME}:`) {
    return null;
  }

  const segments = segmentsOf(url);
  const route = (segments[0] ?? '').toLowerCase();
  const rest = segments.slice(1);
  const query = url.searchParams;

  switch (route) {
    case 'session': {
      const sessionId = rest[0] || query.get('id') || '';
      if (!sessionId) {
        return null;
      }
      return { type: 'session', sessionId, directory: query.get('dir') ?? undefined };
    }

    case 'new':
    case 'new-session':
      return {
        type: 'new-session',
        directory: query.get('dir') ?? undefined,
        projectId: query.get('project') ?? undefined,
        agent: query.get('agent') ?? undefined,
        model: query.get('model') ?? undefined,
      };

    case 'sessions': {
      const filter = query.get('filter');
      return {
        type: 'sessions',
        filter: filter === 'attention' || filter === 'recent' || filter === 'all' ? filter : undefined,
      };
    }

    case 'status':
      return { type: 'status' };

    case 'settings':
      return { type: 'settings', section: rest[0] || query.get('section') || undefined };

    case 'changes':
      return {
        type: 'changes',
        path: rest.join('/') || query.get('path') || undefined,
        staged: query.get('staged') === 'true',
      };

    case 'view': {
      const target = (rest[0] || '').toLowerCase();
      // `changes` has its own richer intent (diff path); route the bare view token to it.
      if (target === 'changes') {
        return { type: 'changes' };
      }
      if (target === 'files' || target === 'mcp' || target === 'instances' || target === 'update') {
        return { type: 'view', target };
      }
      return null;
    }

    default:
      return null;
  }
}