/**
 * The SRS Worker, from the CLI side: one base URL and one read-side payload.
 *
 * `SRS_API` points a script at a `wrangler dev` instance instead of production
 * — the same switch close-solved.ts uses for its `/admin/solved` push, which is
 * why the default lives here rather than in either script.
 *
 * The payload is narrowed with a guard rather than cast: D1 is the only source
 * of SRS truth, so if the Worker answers something else the caller must say so
 * out loud, not render half a dashboard off undefined fields.
 */
import { STAGES, TEMPERATURES, type Stage, type Temperature } from "../api/src/srs.ts";

export const SRS_API = process.env.SRS_API ?? "https://srs-api.prdlk.workers.dev";

// The rungs and the bands come straight from the Worker's domain module — the
// same import work.ts makes for WINDOWS — so a change to either vocabulary
// reaches this dashboard without a second list to remember.
export { STAGES, TEMPERATURES, type Stage, type Temperature };

export interface Phase {
  milestone: number;
  name: string;
  core_done: number;
  core_total: number;
  optional_done: number;
  optional_total: number;
  deferred_done: number;
  deferred_total: number;
}

export interface Topic {
  issue: number;
  name: string;
  milestone: number | null;
  week: number | null;
  taught: boolean;
  total: number;
  done: number;
  retired: number;
  due: number;
  last: string | null;
  age: number | null;
  temperature: Temperature;
}

export interface Stats {
  generated: string;
  campaign: { day: number; week: number; start: string; days: number };
  phases: Phase[];
  ladder: Record<Stage, number>;
  difficulty: { difficulty: string; total: number; done: number }[];
  topics: Topic[];
  /** week is the 1-based campaign week — the Worker converts from ISO. */
  gates: { week: number; issue: number | null; pass_rate: number | null; closed_on: string | null }[];
  streak: number;
  queue: { date: string; due: number }[];
  /** Every campaign day, zeros and future days included. */
  heat: { date: string; attempts: number; passes: number }[];
}

function isStats(value: unknown): value is Stats {
  if (typeof value !== "object" || value === null) return false;
  const v = value as Record<string, unknown>;
  return (
    typeof v.campaign === "object" &&
    v.campaign !== null &&
    typeof v.ladder === "object" &&
    v.ladder !== null &&
    typeof v.streak === "number" &&
    Array.isArray(v.phases) &&
    Array.isArray(v.difficulty) &&
    Array.isArray(v.topics) &&
    Array.isArray(v.gates) &&
    Array.isArray(v.queue) &&
    Array.isArray(v.heat)
  );
}

/** GET /api/stats. Throws with the reason; there is no local substitute. */
export async function fetchStats(signal?: AbortSignal): Promise<Stats> {
  const res = await fetch(`${SRS_API}/api/stats`, { signal });
  if (!res.ok) throw new Error(`GET /api/stats -> ${res.status} ${await res.text()}`);
  const body: unknown = await res.json();
  if (!isStats(body)) throw new Error("GET /api/stats -> unrecognised payload shape");
  return body;
}