const urlJoin = require('url-join');
const CONFIG = require('../config/config');

// Serves the app actor at its canonical uri (`/as/actor/app`) with a Solid-OIDC dual
// personality, discriminated by the request's `JsonLdContext` header — same contract as
// the `/app` route (see app.service.js for the full story), but implemented as a
// standalone service with no dependency on the `app` service.
//
// WHY A SEPARATE SERVICE: the Solid-OIDC client_id IS the actor uri (the pod provider's
// auth-agent only returns the `Link: rel="interop:registeredAgent"` header when the
// requesting app's identity — the token's azp, i.e. this client_id — matches the
// registration's `registeredAgent`, which the pod stores under the actor uri). The
// adapter therefore fetches THIS path as the client metadata document. Routing the path
// to `app.get` deadlocked boot: `@activitypods/app`'s `awaitCreateComplete` polls the
// actor over HTTP while the `app` service is still starting, and an unregistered action
// 503s the poll it waits on. This service has no `started()` work and no dependencies,
// so it is routable long before the `app` service exists.
module.exports = {
  name: 'client-id-doc',
  actions: {
    get: {
      async handler(ctx) {
        const req = ctx.params && ctx.params.$req;
        const headers = (req && req.headers) || {};
        const jsonLdContextKey = Object.keys(headers).find(key => key.toLowerCase() === 'jsonldcontext');
        const isOidcClientIdDocument =
          jsonLdContextKey !== undefined && String(headers[jsonLdContextKey]).includes('solid/oidc-context.jsonld');

        if (isOidcClientIdDocument) {
          // The client_id must equal the fetched URI exactly. `req.url` is rewritten to
          // the alias remainder by moleculer-web; the raw path survives in `originalUrl`.
          const requestPath = String((req && (req.originalUrl || req.url)) || '/as/actor/app').split('?')[0];
          return {
            '@context': ['https://www.w3.org/ns/solid/oidc-context.jsonld'],
            client_id: urlJoin(CONFIG.HOME_URL, requestPath),
            redirect_uris: [urlJoin(CONFIG.FRONT_URL, 'login')],
            client_name: CONFIG.APP_NAME,
            client_uri: CONFIG.FRONT_URL
          };
        }

        return await ctx.call('ldp.resource.get', {
          resourceUri: urlJoin(CONFIG.HOME_URL, 'as/actor/app'),
          accept: 'application/ld+json',
          webId: 'system'
        });
      }
    }
  }
};