import {
  LocalSource,
  RemoteSource,
  HubSource,
  type ShardSource,
} from "./source";

// A serializable description of a data source — the shape we persist, pass to
// use_source, and rebuild a live ShardSource from. `sites` on a hub spec is a
// subset allowlist of member siteIds (undefined = federate every member).
export type SourceSpec =
  | { kind: "hub"; url: string; sites?: string[] }
  | { kind: "remote"; url: string }
  | { kind: "local"; dir: string };

// Resolve the data-source spec from flags or env. Precedence: hub > remote >
// local > positional > default. All logging goes to stderr — stdout is the MCP
// JSON-RPC channel and must not be polluted.
//
//   --hub <url>     | TRANSCRIPT_HUB_URL     federate over a hub's member sites
//   --remote <url>  | TRANSCRIPT_SITE_URL    one deployed site origin
//   --local <dir>   | TRANSCRIPT_LOCAL_DIR   a composed public dir on disk
//   <positional>    an http(s) URL → remote, otherwise a local dir
//   (default)       ./export/public
export function resolveSourceSpec(argv: string[]): SourceSpec {
  const flag = (name: string): string | undefined => {
    const i = argv.indexOf(name);
    return i >= 0 && i + 1 < argv.length ? argv[i + 1] : undefined;
  };

  const hub = flag("--hub") ?? process.env.TRANSCRIPT_HUB_URL;
  if (hub) return { kind: "hub", url: hub };

  const remote =
    flag("--remote") ?? flag("--url") ?? process.env.TRANSCRIPT_SITE_URL;
  if (remote) return { kind: "remote", url: remote };

  const local = flag("--local") ?? process.env.TRANSCRIPT_LOCAL_DIR;
  if (local) return { kind: "local", dir: local };

  const positional = argv.find((a) => !a.startsWith("-"));
  if (positional) {
    return /^https?:\/\//i.test(positional)
      ? { kind: "remote", url: positional }
      : { kind: "local", dir: positional };
  }

  return { kind: "local", dir: "export/public" };
}

// Build a live ShardSource from a spec.
export function buildSource(spec: SourceSpec): ShardSource {
  switch (spec.kind) {
    case "hub":
      return new HubSource(spec.url, spec.sites);
    case "remote":
      return new RemoteSource(spec.url);
    case "local":
      return new LocalSource(spec.dir);
  }
}

// Thin compatibility wrapper: resolve a spec and build it in one call.
export function resolveSource(argv: string[]): ShardSource {
  return buildSource(resolveSourceSpec(argv));
}