/**
 * Shared link handling utilities for the editor system.
 *
 * Used by content-editor (ProseMirror click handler), readonly-content
 * (react-markdown link component), and link-hover-card (Open button).
 */

import { isGlobalPath, isReservedSlug } from "@multica/core/paths";

/**
 * Top-level workspace-scoped routes. Used to detect "/{route}/..." paths that
 * were authored without a workspace slug — we prepend the current slug so they
 * resolve correctly under the new /{slug}/{route}/... URL shape.
 *
 * Why a hardcoded allowlist: the heuristic must be conservative. A path like
 * "/acme/issues/abc" already has a slug (first segment "acme" isn't a known
 * route), so leaving it alone is correct. A path like "/foo/bar" where "foo"
 * isn't a known route is ambiguous — we don't rewrite it, treating the author
 * as intentional. Only "/issues/..." style paths get auto-prefixed.
 */
const WORKSPACE_ROUTE_SEGMENTS = new Set([
  "usage",
  "issues",
  "projects",
  "autopilots",
  "agents",
  "chat",
  "inbox",
  "my-issues",
  "runtimes",
  "skills",
  "settings",
]);

/**
 * Report whether a path is a workspace-scoped app page — `/{slug}/...` where the
 * first segment is a slug a workspace could actually own.
 *
 * The app origin also serves things the app router does not own: `/api/*`,
 * `/uploads/*` (local-storage attachments, proxied by web), `/_next/*`,
 * `/favicon.ico`, and the pre-workspace routes. Every one of those first
 * segments is already a reserved slug, so the reserved list — the same one the
 * backend enforces at workspace creation — answers this question without a
 * parallel deny-list that has to be kept in sync with the backend's routes.
 */
function isWorkspaceScopedPath(pathname: string): boolean {
  const first = pathname.split("/")[1] ?? "";
  if (!first) return false;
  let segment: string;
  try {
    segment = decodeURIComponent(first);
  } catch {
    return false;
  }
  return !isReservedSlug(segment.toLowerCase());
}

/**
 * Convert an absolute URL that points at a workspace page on this deployment's
 * own app into the in-app path it addresses; `null` for anything else.
 *
 * An agent or a user pasting `https://<app-host>/acme/issues/123` means the same
 * destination as `/acme/issues/123`. Without this, the URL reads as external and
 * the desktop app hands it to the system browser instead of opening a tab
 * (MUL-5208).
 *
 * `appOrigin` is the deployment's public app URL, which only the platform layer
 * knows (web: the current origin; desktop: the connected environment's app URL).
 * See `useAppOrigin()`.
 */
export function toInternalAppPath(
  href: string,
  appOrigin?: string | null,
): string | null {
  if (!appOrigin) return null;
  let target: URL;
  let app: URL;
  try {
    target = new URL(href);
    app = new URL(appOrigin);
  } catch {
    return null;
  }
  if (target.origin !== app.origin) return null;
  // Opaque origins (file:, data:) compare equal to each other; only real web
  // origins identify the app.
  if (target.protocol !== "http:" && target.protocol !== "https:") return null;
  if (!isWorkspaceScopedPath(target.pathname)) return null;
  return `${target.pathname}${target.search}${target.hash}`;
}

/**
 * Open a link — internal paths dispatch multica:navigate, external open new tab.
 *
 * If `currentSlug` is provided and `href` is a workspace-scoped path lacking a
 * slug (e.g. "/issues/abc" instead of "/{slug}/issues/abc"), the slug is
 * prepended. This is for legacy markdown content authored before the URL
 * refactor, or future content where users forget the slug when pasting.
 *
 * `appOrigin` lets absolute URLs pointing back at this deployment take the same
 * internal route as a relative path.
 */
export function openLink(
  href: string,
  currentSlug?: string | null,
  appOrigin?: string | null,
): void {
  const internalPath = href.startsWith("/")
    ? href
    : toInternalAppPath(href, appOrigin);
  if (internalPath) {
    let path = internalPath;
    if (currentSlug && !isGlobalPath(path)) {
      const firstSegment = path.split("/")[1];
      if (firstSegment && WORKSPACE_ROUTE_SEGMENTS.has(firstSegment)) {
        // Path looks like /issues/abc (no slug) — prepend current slug.
        path = `/${currentSlug}${path}`;
      }
      // Otherwise the first segment is either already a slug (e.g. "acme" in
      // "/acme/issues") or something unknown (e.g. "/foo"). Leave it alone —
      // the user wrote what they meant.
    }
    window.dispatchEvent(
      new CustomEvent("multica:navigate", { detail: { path } }),
    );
  } else {
    window.open(href, "_blank", "noopener,noreferrer");
  }
}

/** Check if a href is a mention protocol link (should not be opened as a regular link). */
export function isMentionHref(href: string | null | undefined): href is string {
  return !!href && href.startsWith("mention://");
}