/**
 * @file ai-routers.js
 * @description Named AI Router profiles — an endpoint (9Router, OpenRouter, a
 * self-hosted gateway) plus the model names to use against it, saved once and
 * attached to a lane when that lane is created.
 *
 * A profile is exactly what the two CLIs need to talk to a router and nothing
 * more: `baseUrl`, `apiKey`, a default `model`, and one slot per tier mirroring
 * the env keys Claude Code reads. Per-tier slots because a router may expose a
 * different id per tier — and the `model` field fills every one of them,
 * because the common case is a single symbolic name for everything.
 *
 * Profiles are stored one JSON file per profile under
 * `<CLAUDE_HOME>/agenthub-routers/` (dir 0700, files 0600), the same shape and
 * the same reasoning as `cc-profiles.js`: they hold a live API key, so **no
 * route ever returns key material** — `listRouters` reports `hasKey` and
 * nothing else about it.
 *
 * `native` is a built-in profile rather than a branch in the caller: it carries
 * empty connection fields and the vendor's own model names, so "switch back to
 * native" is the same single write path as "switch to a router". It cannot be
 * edited, removed, or shadowed by a saved profile.
 *
 * `testRouter` is the one thing here that talks to the network: the smallest
 * real request a claude lane would make, so "saved" and "actually works" stop
 * being the same claim. It is deliberately NOT a generic proxy — see the note
 * on its stored-key fallback.
 *
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const path = require("node:path");

const { getClaudeHome } = require("./claude-home");

/**
 * A profile's `name` is its filename, so the charset is deliberately narrow.
 * What the user reads and edits is `label`, which accepts spaces and diacritics
 * precisely because it never touches a path. Same split as cc-profiles.js.
 */
const NAME_RE = /^[a-zA-Z0-9][a-zA-Z0-9._-]{0,39}$/;

const LABEL_MIN = 3;
const LABEL_MAX = 60;

/** The per-tier model overrides Claude Code reads, in the order the UI shows them. */
const MODEL_SLOTS = ["opus", "sonnet", "haiku", "smallFast", "subagent"];

const BUILTIN_NAME = "native";

/**
 * The vendor's own defaults, used when a lane is set back to native. Empty
 * connection fields rather than absent ones: the native reference settings.json
 * sets both to "", and an absent key would let a user-level router base URL
 * leak into a lane that asked for native.
 */
const NATIVE = Object.freeze({
  name: BUILTIN_NAME,
  label: "Native",
  builtin: true,
  baseUrl: "",
  apiKey: "",
  model: "claude-sonnet-5",
  models: Object.freeze({
    opus: "claude-opus-5",
    sonnet: "claude-sonnet-5",
    haiku: "claude-haiku-4-5-20251001",
    smallFast: "claude-haiku-4-5-20251001",
    subagent: "claude-haiku-4-5-20251001",
  }),
});

function err(code, message) {
  const e = new Error(message);
  e.code = code;
  return e;
}

function routersDir() {
  return path.join(getClaudeHome(), "agenthub-routers");
}

function routerFile(name) {
  if (typeof name !== "string" || !NAME_RE.test(name)) {
    throw err("EBADNAME", "name must be 1-40 chars of letters, digits, dot, dash or underscore");
  }
  return path.join(routersDir(), `${name}.json`);
}

function readJson(file) {
  let raw;
  try {
    raw = fs.readFileSync(file, "utf8");
  } catch {
    return null;
  }
  try {
    return JSON.parse(raw);
  } catch {
    throw err("EBADJSON", `${file} is not valid JSON - fix it by hand first`);
  }
}

/** Write JSON at 0600 through a temp file, so a crash never truncates the original. */
function writeJson(file, value) {
  fs.mkdirSync(path.dirname(file), { recursive: true, mode: 0o700 });
  const tmp = `${file}.agenthub-tmp`;
  fs.writeFileSync(tmp, `${JSON.stringify(value, null, 2)}\n`, { mode: 0o600 });
  fs.renameSync(tmp, file);
}

/** Reduce any text to the narrow NAME_RE charset, for use as a filename. */
function slugify(text) {
  const base = String(text || "")
    .normalize("NFD")
    .replace(/[\u0300-\u036f]/g, "") // drop the combining accents NFD split off
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "")
    .slice(0, 32);
  return NAME_RE.test(base) ? base : "router";
}

/** `base`, or `base-2`, `base-3`… — the first that is neither taken nor built in. */
function freeName(base) {
  let name = base;
  for (
    let n = 2;
    name === BUILTIN_NAME || fs.existsSync(path.join(routersDir(), `${name}.json`));
  ) {
    name = `${base}-${n}`;
    n += 1;
  }
  return name;
}

function normalizeLabel(label) {
  const clean = typeof label === "string" ? label.trim() : "";
  if (clean.length < LABEL_MIN || clean.length > LABEL_MAX || /[\u0000-\u001f\u007f]/.test(clean)) {
    throw err(
      "EBADLABEL",
      `label must be ${LABEL_MIN}-${LABEL_MAX} characters and no control characters`
    );
  }
  return clean;
}

/**
 * A router endpoint is an http(s) URL and nothing else. A `file:` or
 * `javascript:` base URL is never a router — it is a mistake, or an attempt to
 * point a CLI somewhere it should not go.
 */
function normalizeBaseUrl(baseUrl) {
  const raw = typeof baseUrl === "string" ? baseUrl.trim() : "";
  if (!raw) throw err("EBADURL", "baseUrl is required");
  let parsed;
  try {
    parsed = new URL(raw);
  } catch {
    throw err("EBADURL", `not a valid URL: ${raw}`);
  }
  if (parsed.protocol !== "http:" && parsed.protocol !== "https:") {
    throw err("EBADURL", "baseUrl must be http:// or https://");
  }
  return raw.replace(/\/+$/, "");
}

/** A model name is free text — a router names its own models — but not blank. */
function normalizeModel(model) {
  const clean = typeof model === "string" ? model.trim() : "";
  if (!clean || clean.length > 200 || /[\u0000-\u001f\u007f]/.test(clean)) {
    throw err("EBADMODEL", "model must be 1-200 characters and no control characters");
  }
  return clean;
}

/**
 * Fill every slot from `model`, keeping any the caller set explicitly. This
 * is what makes "one symbolic name for every tier" — the 9Router case — a
 * single field to type instead of six.
 */
function normalizeModels(model, models) {
  const given = models && typeof models === "object" ? models : {};
  const out = {};
  for (const slot of MODEL_SLOTS) {
    out[slot] = given[slot] === undefined ? model : normalizeModel(given[slot]);
  }
  return out;
}

function assertNotBuiltin(name) {
  if (name === BUILTIN_NAME) {
    throw err("EBUILTIN", `'${BUILTIN_NAME}' is the built-in profile and cannot be changed`);
  }
}

/** Read one stored profile (key included), or null when it does not exist. */
function readRouter(name) {
  const stored = readJson(routerFile(name));
  return stored && typeof stored === "object" ? stored : null;
}

/** The browser-safe view: everything except the key, plus whether one is set. */
function publicView(profile) {
  const { apiKey, ...rest } = profile;
  return { ...rest, hasKey: Boolean(apiKey) };
}

/**
 * Every saved profile, with the built-in native one first.
 * @returns `{ items }` — key material is never included.
 */
function listRouters() {
  let names = [];
  try {
    names = fs
      .readdirSync(routersDir())
      .filter((f) => f.endsWith(".json"))
      .map((f) => f.slice(0, -5));
  } catch {
    /* nothing saved yet */
  }

  const items = [publicView(NATIVE)];
  for (const name of names.sort()) {
    if (!NAME_RE.test(name) || name === BUILTIN_NAME) continue;
    let stored;
    try {
      stored = readRouter(name);
    } catch {
      continue; // a corrupt profile file is skipped, not fatal for the list
    }
    if (!stored) continue;
    items.push(publicView({ ...stored, name, builtin: false }));
  }
  return { items };
}

/**
 * One profile INCLUDING its key — for the server's own writers only. No route
 * may return this shape; `listRouters` is what the browser sees.
 */
function getRouter(name) {
  if (name === BUILTIN_NAME) return { ...NATIVE, models: { ...NATIVE.models } };
  const stored = readRouter(name);
  if (!stored) throw err("ENOTFOUND", `no router profile named '${name}'`);
  return { ...stored, name, builtin: false };
}

/**
 * @param {{label:string, baseUrl:string, apiKey?:string, model:string,
 *   models?:Record<string,string>}} input
 * @returns the browser-safe view of what was saved
 */
function createRouter(input = {}) {
  const label = normalizeLabel(input.label);
  const slug = slugify(label);
  assertNotBuiltin(slug);

  const model = normalizeModel(input.model);
  const profile = {
    label,
    baseUrl: normalizeBaseUrl(input.baseUrl),
    apiKey: typeof input.apiKey === "string" ? input.apiKey.trim() : "",
    model,
    models: normalizeModels(model, input.models),
    savedAt: new Date().toISOString(),
  };

  const name = freeName(slug);
  writeJson(routerFile(name), profile);
  return publicView({ ...profile, name, builtin: false });
}

/**
 * Merge changes into a saved profile. The `name` never changes — a lane stores
 * it, and renaming would orphan that lane. An omitted `apiKey` keeps the stored
 * one: the edit form cannot show a key, so it cannot send one back either.
 */
function updateRouter(name, changes = {}) {
  assertNotBuiltin(name);
  const stored = readRouter(name);
  if (!stored) throw err("ENOTFOUND", `no router profile named '${name}'`);

  const model = changes.model === undefined ? stored.model : normalizeModel(changes.model);
  const next = {
    ...stored,
    label: changes.label === undefined ? stored.label : normalizeLabel(changes.label),
    baseUrl: changes.baseUrl === undefined ? stored.baseUrl : normalizeBaseUrl(changes.baseUrl),
    apiKey:
      typeof changes.apiKey === "string" && changes.apiKey.trim()
        ? changes.apiKey.trim()
        : stored.apiKey,
    model,
    models:
      changes.model === undefined && changes.models === undefined
        ? stored.models
        : normalizeModels(model, changes.models ?? stored.models),
    savedAt: new Date().toISOString(),
  };

  writeJson(routerFile(name), next);
  return publicView({ ...next, name, builtin: false });
}

function removeRouter(name) {
  assertNotBuiltin(name);
  const file = routerFile(name);
  if (!fs.existsSync(file)) throw err("ENOTFOUND", `no router profile named '${name}'`);
  fs.rmSync(file);
  return { removed: name };
}

/** How long a connection test waits before calling the endpoint dead. */
const TEST_TIMEOUT_MS = 15_000;

/** Enough of a failing router's own words to be actionable, not enough to flood. */
const TEST_BODY_MAX = 300;

/**
 * Probe a router endpoint with the smallest real request a claude lane makes:
 * one Anthropic-style message capped at a single output token.
 *
 * Deliberately the CLAUDE wire shape and not Codex's `responses` one. A profile
 * is not tool-specific, so a test has to pick; `/v1/messages` is what a claude
 * lane's eight env keys point at, and it is the path a router has to serve for
 * this feature to work at all.
 *
 * **The stored key is only ever sent to the endpoint it was stored against.**
 * A blank `apiKey` falls back to the saved profile named by `name` — but only
 * when the submitted `baseUrl` still matches the saved one. Without that check
 * this route would be a way to make the server POST a saved API key to any URL
 * a browser names, which is exactly the leak `listRouters` exists to prevent.
 *
 * A router that answers is a success even when it answers with an error: the
 * outcome is reported (`ok`, `status`, `message`), never thrown. Only bad INPUT
 * throws.
 *
 * @param {{name?:string, baseUrl:string, apiKey?:string, model:string}} input
 * @returns {Promise<{ok:boolean, status:number|null, message:string}>}
 */
async function testRouter(input = {}) {
  const baseUrl = normalizeBaseUrl(input.baseUrl);
  const model = normalizeModel(input.model);

  let apiKey = typeof input.apiKey === "string" ? input.apiKey.trim() : "";
  if (!apiKey && input.name) {
    const stored = readRouter(input.name);
    if (stored && normalizeBaseUrl(stored.baseUrl || "") === baseUrl) apiKey = stored.apiKey || "";
  }
  if (!apiKey) throw err("EBADKEY", "enter the API key to test this endpoint");

  let res;
  try {
    res = await fetch(`${baseUrl}/v1/messages`, {
      method: "POST",
      headers: {
        "content-type": "application/json",
        // Both, because routers disagree on which one they read, and it is the
        // same key going to the same endpoint either way.
        "x-api-key": apiKey,
        authorization: `Bearer ${apiKey}`,
        "anthropic-version": "2023-06-01",
      },
      body: JSON.stringify({
        model,
        max_tokens: 1,
        messages: [{ role: "user", content: "ping" }],
      }),
      signal: AbortSignal.timeout(TEST_TIMEOUT_MS),
    });
  } catch (e) {
    // Unreachable, DNS failure, TLS refusal, timeout — a real answer about the
    // endpoint, so it is a result and not a 500.
    //
    // `cause` first: node's fetch reports every transport failure as the same
    // useless "fetch failed", and hides the part the user can act on
    // (ECONNREFUSED, ENOTFOUND, a TLS error) one level down.
    return {
      ok: false,
      status: null,
      message: e.name === "TimeoutError" ? "timed out" : (e.cause && e.cause.message) || e.message,
    };
  }

  const body = await res.text().catch(() => "");
  return {
    ok: res.ok,
    status: res.status,
    message: res.ok ? model : body.slice(0, TEST_BODY_MAX) || res.statusText,
  };
}

module.exports = {
  listRouters,
  getRouter,
  createRouter,
  updateRouter,
  removeRouter,
  testRouter,
  MODEL_SLOTS,
  BUILTIN_NAME,
  NATIVE,
};