// Zentraler API-Client. Alles läuft über /api (im Dev leitet der Vite-Proxy an
// das Backend, in Produktion liefert derselbe FastAPI-Prozess API und SPA aus).
// Die Anmeldung liegt in einem HttpOnly-Cookie – deshalb IMMER credentials:"include"
// und kein Token im JavaScript.

const API_BASE = "/api";

// Wird bei einer abgelaufenen/ungültigen Sitzung (HTTP 401) gerufen, damit die
// Oberfläche nicht „angemeldet" bleibt, während jede Abfrage scheitert.
let beiAbmeldung = null;
export function setUnauthorizedHandler(fn) {
  beiAbmeldung = fn;
}

export class ApiError extends Error {
  constructor(message, status) {
    super(message);
    this.status = status;
  }
}

async function request(path, { method = "GET", body, form, formData, skipAuthHandler = false } = {}) {
  const headers = {};
  let payload;
  if (formData) {
    payload = formData; // Content-Type setzt der Browser selbst
  } else if (form) {
    headers["Content-Type"] = "application/x-www-form-urlencoded";
    payload = new URLSearchParams(form).toString();
  } else if (body !== undefined) {
    headers["Content-Type"] = "application/json";
    payload = JSON.stringify(body);
  }

  const resp = await fetch(`${API_BASE}${path}`, {
    method,
    headers,
    body: payload,
    credentials: "include",
  });

  // Abgelaufene Sitzung zentral behandeln – aber nicht beim Login selbst und
  // nicht bei der stillen Startprüfung (dort ist 401 = „noch nicht angemeldet").
  if (resp.status === 401 && path !== "/auth/login" && !skipAuthHandler) {
    beiAbmeldung?.();
  }

  if (resp.status === 204) return null;

  let data = null;
  const text = await resp.text();
  if (text) {
    try {
      data = JSON.parse(text);
    } catch {
      data = text;
    }
  }

  if (!resp.ok) {
    let detail;
    if (data && data.detail) {
      detail = Array.isArray(data.detail) ? data.detail.map((d) => d.msg).join(", ") : data.detail;
    } else if (resp.status === 502 || resp.status === 503 || resp.status === 504) {
      detail = `Server nicht erreichbar (${resp.status}).`;
    } else if (typeof data === "string" && data.trim().startsWith("<")) {
      detail = `Server-Fehler (${resp.status}).`;
    } else if (typeof data === "string" && data) {
      detail = data;
    } else {
      detail = `Fehler ${resp.status}`;
    }
    throw new ApiError(detail, resp.status);
  }
  return data;
}

/** Ortszeit als YYYY-MM-DD_HHMM für Dateinamen. */
function zeitstempel() {
  const jetzt = new Date();
  const zwei = (n) => String(n).padStart(2, "0");
  return (
    `${jetzt.getFullYear()}-${zwei(jetzt.getMonth() + 1)}-${zwei(jetzt.getDate())}` +
    `_${zwei(jetzt.getHours())}${zwei(jetzt.getMinutes())}`
  );
}

/** Datei (mit Sitzungs-Cookie) laden und im Browser als Download anbieten. */
export async function downloadFile(path, filename) {
  const resp = await fetch(`${API_BASE}${path}`, { credentials: "include" });
  if (!resp.ok) {
    throw new ApiError(`Download fehlgeschlagen (${resp.status})`, resp.status);
  }
  const blob = await resp.blob();
  const url = URL.createObjectURL(blob);
  const link = document.createElement("a");
  link.href = url;
  link.download = filename;
  document.body.appendChild(link);
  link.click();
  link.remove();
  URL.revokeObjectURL(url);
}

export { zeitstempel };

export const api = {
  // Auth
  login: (username, password) =>
    request("/auth/login", { method: "POST", form: { username, password } }),
  logout: () => request("/auth/logout", { method: "POST" }),
  me: (opts) => request("/auth/me", { skipAuthHandler: opts?.silent }),
  changePassword: (current_password, new_password) =>
    request("/auth/change-password", { method: "POST", body: { current_password, new_password } }),
  version: () => request("/version"),

  // Benutzer (Admin)
  listUsers: () => request("/users"),
  createUser: (body) => request("/users", { method: "POST", body }),
  updateUser: (id, body) => request(`/users/${id}`, { method: "PATCH", body }),
  deleteUser: (id) => request(`/users/${id}`, { method: "DELETE" }),

  // Einstellungen (je Benutzer)
  listSettings: () => request("/settings"),
  setSetting: (key, value) =>
    request(`/settings/${key}?value=${encodeURIComponent(value)}`, { method: "PUT" }),

  // Konten
  listAccounts: () => request("/accounts"),
  getAccount: (id) => request(`/accounts/${id}`),
  createAccount: (body) => request("/accounts", { method: "POST", body }),
  updateAccount: (id, body) => request(`/accounts/${id}`, { method: "PATCH", body }),
  deleteAccount: (id) => request(`/accounts/${id}`, { method: "DELETE" }),

  // Kategorien (Gruppen + Kategorien)
  listCategories: () => request("/categories"),
  createGroup: (body) => request("/categories/groups", { method: "POST", body }),
  updateGroup: (id, body) => request(`/categories/groups/${id}`, { method: "PATCH", body }),
  deleteGroup: (id) => request(`/categories/groups/${id}`, { method: "DELETE" }),
  createCategory: (body) => request("/categories", { method: "POST", body }),
  updateCategory: (id, body) => request(`/categories/${id}`, { method: "PATCH", body }),
  deleteCategory: (id) => request(`/categories/${id}`, { method: "DELETE" }),

  // Transaktionen
  listTransactions: (params = {}) => {
    const qs = new URLSearchParams();
    for (const [k, v] of Object.entries(params)) {
      if (v !== undefined && v !== null && v !== "") qs.set(k, v);
    }
    const s = qs.toString();
    return request(`/transactions${s ? `?${s}` : ""}`);
  },
  getTransaction: (id) => request(`/transactions/${id}`),
  createTransaction: (body) => request("/transactions", { method: "POST", body }),
  updateTransaction: (id, body) => request(`/transactions/${id}`, { method: "PATCH", body }),
  deleteTransaction: (id) => request(`/transactions/${id}`, { method: "DELETE" }),

  // Wechselkurse
  rateStatus: () => request("/rates/status"),
  convertRate: (amountCents, from, to, on) => {
    const qs = new URLSearchParams({ amount_cents: amountCents, from_currency: from, to_currency: to });
    if (on) qs.set("on", on);
    return request(`/rates/convert?${qs.toString()}`);
  },

  // Budget
  budgetCurrent: () => request("/budget/current"),
  budget: (label) => request(`/budget/${label}`),
  budgetTemplate: () => request("/budget/template"),
  setTemplateCategory: (catId, cents) =>
    request(`/budget/template/category/${catId}?planned_cents=${cents}`, { method: "PUT" }),
  setMonthCategory: (label, catId, cents) =>
    request(`/budget/${label}/category/${catId}?planned_cents=${cents}`, { method: "PUT" }),
  resetMonth: (label) => request(`/budget/${label}`, { method: "DELETE" }),
  createIncome: (body) => request("/budget/income", { method: "POST", body }),
  updateIncome: (id, body) => request(`/budget/income/${id}`, { method: "PATCH", body }),
  deleteIncome: (id) => request(`/budget/income/${id}`, { method: "DELETE" }),

  // Dashboard
  dashboardLayout: () => request("/dashboard/layout"),
  saveDashboardLayout: (layout) => request("/dashboard/layout", { method: "PUT", body: layout }),
  resetDashboardLayout: () => request("/dashboard/layout", { method: "DELETE" }),
  cardBudgetDonut: () => request("/dashboard/budget-donut"),
  cardBudgetProgress: () => request("/dashboard/budget-progress"),
  cardIncomeExpense: () => request("/dashboard/income-expense"),
  cardBalances: () => request("/dashboard/balances"),
  cardNetWorth: (days) => request(`/dashboard/net-worth${days ? `?days=${days}` : ""}`),
  cardRecent: (limit) => request(`/dashboard/recent${limit ? `?limit=${limit}` : ""}`),

  // CSV-Import
  importPresets: () => request("/imports/presets"),
  importTemplates: () => request("/imports/templates"),
  createImportTemplate: (body) => request("/imports/templates", { method: "POST", body }),
  updateImportTemplate: (id, body) => request(`/imports/templates/${id}`, { method: "PATCH", body }),
  deleteImportTemplate: (id) => request(`/imports/templates/${id}`, { method: "DELETE" }),
  importRaw: (formData) => request("/imports/raw", { method: "POST", formData }),
  importPreview: (formData) => request("/imports/preview", { method: "POST", formData }),
  importCommit: (body) => request("/imports/commit", { method: "POST", body }),
  importBatches: () => request("/imports/batches"),
  undoImportBatch: (id) => request(`/imports/batches/${id}`, { method: "DELETE" }),

  // PDF/Bild-Beleg
  documentPreview: (formData) => request("/documents/preview", { method: "POST", formData }),
};