// API client and shared application state.

export const state = {
  me: null,          // whoami response
  csrf: "",
  draft: null,       // the open changeset edits are staged into
  immediate: false,  // apply edits immediately instead of staging them
  rrtypes: null,
  listeners: new Set(),
};

export class APIError extends Error {
  constructor(status, body) {
    const e = (body && body.error) || {};
    super(e.message || ("HTTP " + status));
    this.status = status;
    this.code = e.code || "";
    this.details = e;
    this.result = e.result || null;
  }
}

let onUnauthorized = () => {};
export function setUnauthorizedHandler(fn) { onUnauthorized = fn; }

// With two-factor login, some actions (API tokens, users) need a code
// from the last few minutes. The server then answers totp_step_up (or
// totp_invalid for a wrong code); askCode asks for one, and the request is
// sent again with it. It returns null when the user cancels.
let askCode = null;
export function setCodePrompt(fn) { askCode = fn; }
const stepUpCodes = new Set(["totp_step_up", "totp_invalid"]);

// api calls the REST API. opts: {body, stage (bool), query, code}.
export async function api(method, path, opts = {}) {
  try {
    return await call(method, path, opts);
  } catch (e) {
    if (!askCode || e.status !== 403 || !stepUpCodes.has(e.code) || path.startsWith("/me/totp/disable")) throw e;
    const code = await askCode(e.code === "totp_invalid" ? e.message : "");
    if (!code) throw e;
    return api(method, path, { ...opts, code });
  }
}

async function call(method, path, opts) {
  const headers = { "Accept": "application/json" };
  let body;
  if (opts.body !== undefined) {
    headers["Content-Type"] = "application/json";
    body = JSON.stringify(opts.body);
  }
  if (method !== "GET" && state.csrf) headers["X-CSRF-Token"] = state.csrf;
  let url = "/api/v1" + path;
  if (opts.query) {
    const q = new URLSearchParams();
    for (const [k, v] of Object.entries(opts.query)) if (v !== undefined && v !== null && v !== "") q.set(k, v);
    const s = q.toString();
    if (s) url += (url.includes("?") ? "&" : "?") + s;
  }
  if (opts.stage) headers["X-Jarl-Changeset"] = String(opts.stage);
  if (opts.code) headers["X-Jarl-TOTP"] = opts.code;
  const resp = await fetch(url, { method, headers, body, credentials: "same-origin" });
  if (resp.status === 204) return null;
  const ct = resp.headers.get("Content-Type") || "";
  const data = ct.includes("application/json") ? await resp.json() : await resp.text();
  if (!resp.ok) {
    if (resp.status === 401 && !path.startsWith("/auth/login")) onUnauthorized();
    throw new APIError(resp.status, data);
  }
  return data;
}

export const get = (path, query) => api("GET", path, { query });

// stream GETs a newline-delimited JSON response (?stream=1 endpoints) and
// calls onEvent with each value as it arrives. It resolves at the end.
export async function stream(path, query, onEvent) {
  const q = new URLSearchParams(query || {});
  const resp = await fetch("/api/v1" + path + (q.toString() ? "?" + q : ""), { headers: { "Accept": "application/x-ndjson" }, credentials: "same-origin" });
  if (!resp.ok) {
    const ct = resp.headers.get("Content-Type") || "";
    const data = ct.includes("application/json") ? await resp.json() : await resp.text();
    if (resp.status === 401) onUnauthorized();
    throw new APIError(resp.status, data);
  }
  const reader = resp.body.getReader();
  const dec = new TextDecoder();
  let buf = "";
  for (;;) {
    const { value, done } = await reader.read();
    if (value) buf += dec.decode(value, { stream: true });
    let nl;
    while ((nl = buf.indexOf("\n")) >= 0) {
      const line = buf.slice(0, nl).trim();
      buf = buf.slice(nl + 1);
      if (line) onEvent(JSON.parse(line));
    }
    if (done) break;
  }
  if (buf.trim()) onEvent(JSON.parse(buf));
}

// draftQuery adds the draft changeset to a query, so reads show the
// configuration as it will be once the pending changes are applied.
export function draftQuery(query = {}) {
  if (state.draft && !state.immediate) return { ...query, changeset: state.draft.id };
  return query;
}

// ---- drafts

const draftKey = () => "jarl.draft." + (state.me ? state.me.user.id : "");
const immediateKey = () => "jarl.immediate." + (state.me ? state.me.user.id : "");

export function onChange(fn) { state.listeners.add(fn); return () => state.listeners.delete(fn); }
export function notify() { for (const fn of state.listeners) fn(); }

// loadDraft restores the user's draft changeset if it is still open.
export async function loadDraft() {
  state.immediate = localStorage.getItem(immediateKey()) === "1";
  const id = localStorage.getItem(draftKey());
  state.draft = null;
  if (id) {
    try {
      const cs = await get("/changesets/" + id);
      if (cs.status === "open") state.draft = cs;
    } catch { /* gone */ }
  }
  if (!state.draft) {
    // Pick up the newest open changeset made in the web UI.
    try {
      const list = await get("/changesets", { status: "open", mine: 1, limit: 20 });
      const web = list.find((c) => c.via === "web");
      if (web) state.draft = web;
    } catch { /* ignore */ }
  }
  if (state.draft) localStorage.setItem(draftKey(), state.draft.id);
  notify();
}

export function setImmediate(on) {
  state.immediate = on;
  localStorage.setItem(immediateKey(), on ? "1" : "0");
  notify();
}

export async function refreshDraft() {
  if (!state.draft) return;
  try {
    const cs = await get("/changesets/" + state.draft.id);
    state.draft = cs.status === "open" ? cs : null;
  } catch { state.draft = null; }
  if (!state.draft) localStorage.removeItem(draftKey());
  notify();
}

export function useDraft(cs) {
  state.draft = cs;
  if (cs) localStorage.setItem(draftKey(), cs.id); else localStorage.removeItem(draftKey());
  notify();
}

async function ensureDraft() {
  if (state.draft) return state.draft;
  const cs = await api("POST", "/changesets", { body: { description: "" } });
  cs.fresh = true;
  useDraft(cs);
  return cs;
}

// dropFreshDraft discards a draft that was created for an edit the server
// then rejected, so no empty changeset is left open.
async function dropFreshDraft(cs) {
  if (!cs.fresh || (state.draft && state.draft.id !== cs.id) || (state.draft && (state.draft.ops || []).length)) return;
  try { await api("POST", "/changesets/" + cs.id + "/discard"); } catch { /* leave it */ }
  useDraft(null);
}

// change sends a configuration change: staged into the draft changeset,
// or applied at once when immediate mode is on (or opts.immediate).
// It returns the API response.
export async function change(method, path, body, opts = {}) {
  if (state.immediate || opts.immediate) {
    const r = await api(method, path, { body, query: opts.query });
    notify();
    return r;
  }
  const cs = await ensureDraft();
  try {
    const r = await api(method, path, { body, stage: cs.id, query: opts.query });
    if (r && r.changeset) state.draft = r.changeset;
    notify();
    return r;
  } catch (e) {
    if (e.status === 409 && /is (applied|discarded)/.test(e.message)) {
      useDraft(null);
      return change(method, path, body, opts);
    }
    await dropFreshDraft(cs);
    throw e;
  }
}

// changeMany submits several requests ({op, id, data}) together.
export async function changeMany(ops, description, opts = {}) {
  if (state.immediate || opts.immediate) {
    const r = await api("POST", "/apply", { body: { ops, description } });
    notify();
    return r;
  }
  const cs = await ensureDraft();
  let r;
  try {
    r = await api("POST", "/changesets/" + cs.id + "/ops", { body: { ops } });
  } catch (e) {
    await dropFreshDraft(cs);
    throw e;
  }
  if (r && r.changeset) state.draft = r.changeset;
  notify();
  return r;
}

// describeResult turns a mutation response into a short message.
export function describeResult(r) {
  if (!r) return "Done";
  if (r.staged) {
    const n = (r.added || []).length;
    return "Staged " + (n === 1 ? "1 change" : n + " changes") + " — review and apply under Changes";
  }
  if (r.applied) return "Applied (changeset #" + r.changeset_id + ")";
  if (r.dry_run) return "Dry run OK";
  return "Done";
}

export function can(resource, write) {
  const me = state.me;
  if (!me) return false;
  if (me.admin) return true;
  return (me.user.grants || []).some((g) =>
    (g.resource === "*" || g.resource === resource) && (!write || g.access === "write"));
}

export async function rrtypes() {
  if (!state.rrtypes) state.rrtypes = await get("/catalog/rrtypes");
  return state.rrtypes;
}