/**
 * Anthropic Subscription Usage Extension
 *
 * Zeigt die aktuellen Rate-Limit-Auslastungen für Anthropic claude.ai
 * Pro/Max Subscriptions live im TUI Footer an.
 *
 * Endpunkt: https://api.anthropic.com/api/oauth/usage
 * Nur aktiv wenn OAuth-Token vorhanden (sk-ant-oat... = Subscription).
 *
 * Anzeige: Footer-Status via ctx.ui.setStatus()
 * Update:  nach agent_end + model_select + /usage Command
 */

import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";

const USAGE_URL = "https://api.anthropic.com/api/oauth/usage";
const STATUS_KEY = "anthropic-usage";
const FETCH_TIMEOUT_MS = 8000;

// ─── Typen ───────────────────────────────────────────────────────────────────

interface RateWindow {
  utilization: number;       // 0–100
  resets_at: string | null;  // ISO-8601 oder null
}

interface UsageResponse {
  five_hour?: RateWindow | null;
  seven_day?: RateWindow | null;
  seven_day_opus?: RateWindow | null;
  seven_day_sonnet?: RateWindow | null;
  [key: string]: RateWindow | null | undefined;
}

// ─── Hilfsfunktionen ─────────────────────────────────────────────────────────

function formatTimeUntil(isoString: string | null): string {
  if (!isoString) return "—";
  const diffMs = new Date(isoString).getTime() - Date.now();
  if (diffMs <= 0) return "jetzt";
  const totalMin = Math.floor(diffMs / 60_000);
  const h = Math.floor(totalMin / 60);
  const m = totalMin % 60;
  const d = Math.floor(h / 24);
  if (d > 0) return `${d}d${h % 24}h`;
  if (h === 0) return `${m}m`;
  if (m === 0) return `${h}h`;
  return `${h}h${m}m`;
}

function bar(pct: number, width = 8): string {
  const filled = Math.round((pct / 100) * width);
  return "█".repeat(filled) + "░".repeat(width - filled);
}

function colorForPct(pct: number, text: string, theme: any): string {
  if (pct >= 90) return theme.fg("error", text);
  if (pct >= 70) return theme.fg("warning", text);
  return theme.fg("success", text);
}

function fmtWindowShort(label: string, w: RateWindow, theme: any): string {
  const pct = Math.round(w.utilization);
  const reset = formatTimeUntil(w.resets_at);
  const indicator = colorForPct(pct, `${bar(pct)} ${pct}%`, theme);
  return `${theme.fg("dim", label)} ${indicator} ${theme.fg("dim", `↺${reset}`)}`;
}

function formatStatus(data: UsageResponse, theme: any): string {
  const parts: string[] = [];

  if (data.five_hour?.utilization != null)
    parts.push(fmtWindowShort("5h", data.five_hour, theme));
  if (data.seven_day?.utilization != null)
    parts.push(fmtWindowShort("7d", data.seven_day, theme));

  // Optionale Modell-spezifische Fenster (falls belegt)
  if (data.seven_day_opus?.utilization)
    parts.push(fmtWindowShort("opus", data.seven_day_opus, theme));
  if (data.seven_day_sonnet?.utilization)
    parts.push(fmtWindowShort("sonnet", data.seven_day_sonnet, theme));

  if (parts.length === 0) return theme.fg("dim", "☁ keine Usage-Daten");
  return `☁ ${parts.join("  ")}`;
}

// ─── Fetch ───────────────────────────────────────────────────────────────────

async function fetchUsage(token: string): Promise<UsageResponse | null> {
  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), FETCH_TIMEOUT_MS);
  try {
    const res = await fetch(USAGE_URL, {
      headers: {
        Authorization: `Bearer ${token}`,
        "Content-Type": "application/json",
      },
      signal: controller.signal,
    });
    if (!res.ok) return null;
    return (await res.json()) as UsageResponse;
  } catch {
    return null;
  } finally {
    clearTimeout(timeout);
  }
}

// ─── Extension ───────────────────────────────────────────────────────────────

export default function (pi: ExtensionAPI) {

  async function getOAuthToken(ctx: any): Promise<string | null> {
    const model = ctx.model;
    if (!model || model.provider !== "anthropic") return null;
    if (!ctx.modelRegistry.isUsingOAuth(model)) return null;
    return (await ctx.modelRegistry.getApiKeyForProvider("anthropic")) ?? null;
  }

  async function refresh(ctx: any): Promise<void> {
    if (!ctx.hasUI) return;

    const token = await getOAuthToken(ctx);
    if (!token) {
      ctx.ui.setStatus(STATUS_KEY, undefined);
      return;
    }

    const data = await fetchUsage(token);
    if (!data) {
      ctx.ui.setStatus(STATUS_KEY, ctx.ui.theme.fg("dim", "☁ usage: Fehler"));
      return;
    }

    ctx.ui.setStatus(STATUS_KEY, formatStatus(data, ctx.ui.theme));
  }

  pi.on("session_start", async (_e, ctx) => { await refresh(ctx); });
  pi.on("agent_end",     async (_e, ctx) => { await refresh(ctx); });
  pi.on("model_select",  async (_e, ctx) => { await refresh(ctx); });

  // ── /usage Command ────────────────────────────────────────────────────────

  pi.registerCommand("usage", {
    description: "Anthropic Subscription Usage anzeigen (Pro/Max)",
    handler: async (_args, ctx) => {
      const token = await getOAuthToken(ctx);
      if (!token) {
        ctx.ui.notify(
          "Kein OAuth-Token — nur für claude.ai Pro/Max Subscriptions",
          "warning"
        );
        return;
      }

      ctx.ui.notify("Lade Usage-Daten…", "info");
      const data = await fetchUsage(token);
      if (!data) {
        ctx.ui.notify("Fetch fehlgeschlagen", "error");
        return;
      }

      const lines: string[] = ["Anthropic Subscription Usage\n"];

      const fmtDetail = (label: string, w: RateWindow) => {
        const pct = w.utilization.toFixed(1);
        const reset = formatTimeUntil(w.resets_at);
        lines.push(`${label.padEnd(12)} ${bar(w.utilization, 14)} ${pct}%   ↺ ${reset}`);
      };

      if (data.five_hour?.utilization != null) fmtDetail("5h-Fenster", data.five_hour);
      if (data.seven_day?.utilization != null)  fmtDetail("7d-Fenster", data.seven_day);
      if (data.seven_day_opus?.utilization)      fmtDetail("7d Opus",    data.seven_day_opus);
      if (data.seven_day_sonnet?.utilization)    fmtDetail("7d Sonnet",  data.seven_day_sonnet);

      if (lines.length === 1) lines.push("Keine Daten verfügbar");

      ctx.ui.notify(lines.join("\n"), "info");
      ctx.ui.setStatus(STATUS_KEY, formatStatus(data, ctx.ui.theme));
    },
  });
}