/**
 * Console 用户认证:用户名密码登录 + HMAC 签名会话 cookie。
 * cookie 值: base64url(payload) "." hex(HMAC-SHA256(sessionSecret, payload))
 */

import { hmacSha256Hex, timingSafeEqualHex, verifyPassword } from "../../shared/src/index.ts";
import type { Env } from "./env.ts";
import { getSessionSecret } from "./db.ts";
import { nowIso, readJson } from "./util.ts";
import { Hono } from "hono";

/** # 成员变量: 会话 cookie 名称 **/
export const SESSION_COOKIE = "wmh_session";

/** # 成员变量: 会话有效期(秒),默认 7 天 **/
const SESSION_TTL_SECONDS = 7 * 24 * 3600;

/** # 成员变量: 会话 payload **/
interface SessionPayload {
  uid: string;
  username: string;
  exp: number;
}

/** # 函数
 * 签发会话 token
 */
export async function issueSessionToken(env: Env, uid: string, username: string): Promise<string> {
  const payload: SessionPayload = {
    uid,
    username,
    exp: Math.floor(Date.now() / 1000) + SESSION_TTL_SECONDS,
  };
  const body = base64UrlEncode(JSON.stringify(payload));
  const secret = await getSessionSecret(env);
  const sig = await hmacSha256Hex(secret, body);
  return `${body}.${sig}`;
}

/** # 函数
 * 校验会话 token,返回 payload;无效/过期返回 null
 */
export async function verifySessionToken(
  env: Env,
  token: string | undefined,
): Promise<SessionPayload | null> {
  if (!token) return null;
  const dot = token.lastIndexOf(".");
  if (dot <= 0) return null;
  const body = token.slice(0, dot);
  const sig = token.slice(dot + 1);
  const secret = await getSessionSecret(env);
  const expected = await hmacSha256Hex(secret, body);
  if (!timingSafeEqualHex(expected, sig)) return null;
  let payload: SessionPayload;
  try {
    payload = JSON.parse(base64UrlDecode(body)) as SessionPayload;
  } catch {
    return null;
  }
  if (!payload?.uid || typeof payload.exp !== "number") return null;
  if (payload.exp < Math.floor(Date.now() / 1000)) return null;
  return payload;
}

/** # 函数
 * 从 Request 中取会话 cookie
 */
export function readSessionCookie(request: Request): string | undefined {
  const cookie = request.headers.get("Cookie") ?? "";
  for (const part of cookie.split(";")) {
    const [k, ...rest] = part.trim().split("=");
    if (k === SESSION_COOKIE) return rest.join("=");
  }
  return undefined;
}

/** # 函数
 * 构造 Set-Cookie 会话头
 */
export function sessionSetCookie(token: string): string {
  return `${SESSION_COOKIE}=${token}; Path=/; HttpOnly; SameSite=Strict; Max-Age=${SESSION_TTL_SECONDS}`;
}

/** # 函数
 * 构造清除会话 cookie 头
 */
export function clearSessionCookie(): string {
  return `${SESSION_COOKIE}=; Path=/; HttpOnly; SameSite=Strict; Max-Age=0`;
}

function base64UrlEncode(s: string): string {
  const bytes = new TextEncoder().encode(s);
  let bin = "";
  for (const b of bytes) bin += String.fromCharCode(b);
  return btoa(bin).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

function base64UrlDecode(s: string): string {
  const b64 = s.replace(/-/g, "+").replace(/_/g, "/");
  const bin = atob(b64 + "=".repeat((4 - (b64.length % 4)) % 4));
  const bytes = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) bytes[i] = bin.charCodeAt(i);
  return new TextDecoder().decode(bytes);
}

/** # 函数
 * 装配认证路由:POST /login、POST /logout、GET /me
 */
export function authRoutes() {
  const app = new Hono<{ Bindings: Env }>();

  /** 登录:用户名密码 → 签名会话 cookie。默认账号 admin/admin(首次启动自动播种) */
  app.post("/login", async (c) => {
    const { username, password } = await readJson<{ username?: string; password?: string }>(c.req.raw);
    if (!username || !password) {
      return c.json({ error: "username and password required" }, 400);
    }
    const user = await c.env.DB.prepare("SELECT id, username, password_hash FROM users WHERE username = ?")
      .bind(username)
      .first<{ id: string; username: string; password_hash: string }>();
    if (!user || !(await verifyPassword(password, user.password_hash))) {
      return c.json({ error: "invalid username or password" }, 401);
    }
    const token = await issueSessionToken(c.env, user.id, user.username);
    c.header("Set-Cookie", sessionSetCookie(token));
    return c.json({ ok: true, user: { id: user.id, username: user.username } });
  });

  /** 登出:清除会话 cookie */
  app.post("/logout", (c) => {
    c.header("Set-Cookie", clearSessionCookie());
    return c.json({ ok: true });
  });

  /** 当前登录用户信息(用户名以库内为准:v2.9.0 起支持改用户名,旧会话 cookie 的 payload 可能是旧名) */
  app.get("/me", async (c) => {
    const payload = await verifySessionToken(c.env, readSessionCookie(c.req.raw));
    if (!payload) return c.json({ error: "unauthorized" }, 401);
    const row = await c.env.DB.prepare("SELECT username FROM users WHERE id = ?")
      .bind(payload.uid)
      .first<{ username: string }>();
    return c.json({ user: { id: payload.uid, username: row?.username ?? payload.username }, now: nowIso() });
  });

  return app;
}