import { accentHex } from "./accent";
import type { ChannelGroup } from "./channelGroups";
import { CONTRACT } from "./corpus";
import type { Manifest } from "./manifest";
import type { Site } from "./site";
import type { SocialLink } from "./settings";

// The public site descriptor served at `/site.json` on every export bundle.
//
// This is the federation contract: a hub PWA reads this from any export-site
// origin (same-origin for the built-in pool, CORS cross-origin for user-added
// externals) to learn a site's branding, channels, and freshness WITHOUT a
// second roundtrip. It is emitted regardless of whether the instance ships a
// PWA — a "dumb instance" (no service worker / not installable) is still fully
// federatable through this file.
//
// Deliberately excludes operational/internal config (cloudflareProject,
// relatedSites): only public presentation fields belong here.

export const SITE_DESCRIPTOR_VERSION = CONTRACT.siteDescriptor;

// One channel a site exposes, with the slug that gives it a collision-free
// identity across sites (display names collide, slugs don't).
export type PublicChannel = {
  slug: string;
  name: string;
  count: number;
  groupId?: string;
};

export type PublicSiteDescriptor = {
  // Contract version — a hub rejects a descriptor whose contract it doesn't
  // understand. Bump when the shape changes incompatibly.
  contract: number;
  siteId: string;
  siteTitle: string;
  siteDescription: string;
  headerTitle: string;
  homeTagline: string;
  accent?: string;
  // Absolute public URL of this deployment (self-reference), when configured.
  siteUrl?: string;
  // The intended hub parent this site belongs under (resolved: site override
  // ?? family default). Lets a standalone site link to its hub and lets a hub
  // tell member sites (that name it) from arbitrary added origins.
  hubUrl?: string;
  // Whether this instance ships an installable PWA (service worker + manifest).
  // A hub can badge federated sites that are independently installable.
  pwa: boolean;
  // Resolved social links (site override ?? global default).
  socialLinks: SocialLink[];
  groups: ChannelGroup[];
  defaultGroupId: string;
  channels: PublicChannel[];
  // Mirror of the summaries manifest's generatedAt — the freshness/staleness
  // signal a hub uses to invalidate cached cross-origin shards.
  generatedAt: string;
  // The summaries MANIFEST_VERSION at build time, so a hub can detect a shard
  // shape it doesn't understand.
  summariesVersion: number;
};

// Build the public descriptor from a Site plus the site's just-composed
// summaries manifest (source of channels/groups/generatedAt) and the resolved
// social links. `pwa`/`hubUrl` are resolved by the caller (they depend on
// build-time config + settings) and passed in.
export function buildSiteDescriptor(
  site: Site,
  manifest: Manifest,
  socialLinks: SocialLink[],
  opts: { pwa: boolean; hubUrl?: string },
): PublicSiteDescriptor {
  const channels: PublicChannel[] = manifest.channels
    .filter((c): c is typeof c & { slug: string } => typeof c.slug === "string")
    .map((c) => ({
      slug: c.slug,
      name: c.name,
      count: c.count,
      ...(c.groupId ? { groupId: c.groupId } : {}),
    }));
  return {
    contract: SITE_DESCRIPTOR_VERSION,
    siteId: site.siteId,
    siteTitle: site.siteTitle,
    siteDescription: site.siteDescription,
    headerTitle: site.headerTitle,
    homeTagline: site.homeTagline,
    // Always a hex on the wire: an accent id means nothing to another hub.
    ...(accentHex(site.accent) ? { accent: accentHex(site.accent) } : {}),
    ...(site.siteUrl ? { siteUrl: site.siteUrl } : {}),
    ...(opts.hubUrl ? { hubUrl: opts.hubUrl } : {}),
    pwa: opts.pwa,
    socialLinks,
    groups: site.groups,
    defaultGroupId: site.defaultGroupId,
    channels,
    generatedAt: manifest.generatedAt,
    summariesVersion: manifest.version,
  };
}