/**
 * Serves accounts (sign-up, sign-in, tokens, passwords) and user profiles,
 * with what each user posted, upvoted, follows and invited. A profile sent to
 * anyone but its user goes through `toPublicUser`, which drops the email.
 *
 * - `POST /api/users/register` — public, with a valid invite. Creates an
 *   account, sends the welcome email, and answers the user and their tokens.
 * - `POST /api/users/login` — public. Answers the user and their tokens;
 *   rate-limited per account.
 * - `GET /api/users/me` — signed in. Answers the caller's own user.
 * - `GET /api/users/me/media-token` — signed in. Answers a media token, for a
 *   session that predates them.
 * - `POST /api/users/request-password-reset` — public. Emails a reset link to
 *   the account with that address, if any; always answers 200.
 * - `POST /api/users/reset-password` — public, with a reset token. Sets a new
 *   password.
 * - `POST /api/users/me/change-password` — signed in, with the current
 *   password. Sets a new one, ending every other session, and answers fresh
 *   tokens.
 * - `PATCH /api/users/me` — signed in. Updates the caller's profile fields:
 *   description and email.
 * - `PATCH /api/users/:userId/role` — permission `user:manage`. Sets another
 *   user's role.
 * - `GET /api/users/search?q=` — public. Answers up to 8 users whose name
 *   starts with `q`, for @mention suggestions.
 * - `GET /api/users/by-id/:userId` — public. Answers a user's profile by id.
 * - `GET /api/users/:username/followed-users?page=&limit=` — public. Answers a
 *   page of the users they follow.
 * - `GET /api/users/:username/followed-playlists?page=&limit=` — public.
 *   Answers a page of the public playlists they follow.
 * - `GET /api/users/:username/playlists?page=&limit=` — optional sign-in.
 *   Answers a page of their playlists, the private ones only to themselves.
 * - `GET /api/users/:username/invitees` — public. Answers the tree of users
 *   they invited.
 * - `GET /api/users/:username` — public. Answers a user's profile.
 * - `GET /api/users/:username/dumps?page=&limit=` — optional sign-in. Answers a
 *   page of their dumps, the private ones only to themselves.
 * - `GET /api/users/:username/votes?page=&limit=` — optional sign-in. Answers a
 *   page of the dumps they upvoted, private ones only to themselves.
 *
 * @module
 */

import { Router } from "@oak/oak";

import { type APIResponse, type PaginatedData } from "../../shared/api.ts";
import { APIException } from "../lib/api-exception.ts";
import {
  type AuthResponse,
  type AuthTokens,
  type Invitee,
  isRole,
  type MediaTokenResponse,
  type PublicUser,
  type SelfUser,
  type UserSuggestion,
} from "../../shared/user.ts";
import type { Dump } from "../../shared/dump.ts";
import {
  fieldOf,
  isLoginUserRequest,
  isRegisterUserRequest,
  isUpdateUserRequest,
  validateRegisterUserRequest,
} from "../validators/user.ts";
import type { Playlist } from "../../shared/playlist.ts";
import { toPublicUser, toSelfUser, type User } from "../model/user.ts";

import { createJWT, createMediaToken } from "../lib/jwt.ts";
import { hashPassword, verifyPassword } from "../lib/password.ts";
import { type RateLimit, takeToken } from "../lib/rate-limit.ts";
import {
  type AuthContext,
  authMiddleware,
  requirePermission,
} from "../middleware/auth.ts";
import { parseOptionalAuth } from "../lib/auth.ts";
import { parsePagination } from "../lib/pagination.ts";
import {
  createUser,
  getInviteTree,
  getUserById,
  getUserByUsername,
  searchUsers,
  updateUser,
} from "../services/user-service.ts";
import { claimInvite, releaseInvite } from "../services/invite-service.ts";
import {
  requestPasswordReset,
  resetPassword,
} from "../services/password-reset-service.ts";
import { isEmailEnabled, sendEmail } from "../services/email-service.ts";
import { FROM_EMAIL, OG_SITE_NAME, WELCOME_EMAIL_BODY } from "../config.ts";
import { VALIDATION } from "../../shared/validation.ts";
import { marked } from "marked";
import { broadcastUserUpdated } from "../services/ws-service.ts";
import {
  getDumpsByUser,
  getVotedDumpsByUser,
} from "../services/dump-service.ts";
import { listPlaylistsByUser } from "../services/playlist-service.ts";
import {
  getFollowedPlaylistsByUser,
  getFollowedUsersByUser,
} from "../services/follow-service.ts";

// Hashed once, at startup, for the sign-ins of usernames that don't exist.
const UNKNOWN_USER_HASH: Promise<string> = hashPassword(crypto.randomUUID());

/**
 * Mounted by `api/main.ts` behind the error, Open Graph and CORS middleware.
 * An `APIException` thrown by a handler becomes the JSON error response there.
 */
const router: Router = new Router({ prefix: "/api/users" });

/** Allows a burst of 10 login attempts per account, then one every 30s. */
const LOGIN_LIMIT: RateLimit = { capacity: 10, refill: 1 / 30 };

/**
 * Returns a new session token and media token for `user`, as sign-up, sign-in
 * and a password change answer them.
 */
async function issueTokens(user: User): Promise<AuthTokens> {
  return {
    token: await createJWT({
      userId: user.id,
      username: user.username,
      role: user.role,
    }),
    mediaToken: await createMediaToken(user.id),
  };
}

router.post("/register", async (ctx) => {
  const body: unknown = await ctx.request.body.json();

  if (!isRegisterUserRequest(body)) {
    throw new APIException(
      400,
      validateRegisterUserRequest(body) ?? "Invalid request",
    );
  }

  // Claimed before the async account creation, so that one invite can't open
  // two accounts, and handed back if the creation fails.
  const inviterId = claimInvite(body.inviteToken);

  let user;
  try {
    user = await createUser(body, inviterId);
  } catch (err) {
    releaseInvite(body.inviteToken);
    throw err;
  }

  // Not awaited: a slow or failing SMTP server mustn't hold up the sign-up.
  if (isEmailEnabled()) {
    const emailMarkdown = WELCOME_EMAIL_BODY
      .replaceAll("{{username}}", user.username)
      .replaceAll("{{site_name}}", OG_SITE_NAME);
    sendEmail({
      from: FROM_EMAIL,
      to: user.email,
      subject: `Welcome to ${OG_SITE_NAME}`,
      text: emailMarkdown,
      html: await marked(emailMarkdown),
    }).catch((err) => console.error("[register] welcome email failed:", err));
  }

  const responseBody: APIResponse<AuthResponse> = {
    success: true,
    data: { ...await issueTokens(user), user: toSelfUser(user) },
  };
  ctx.response.status = 201;
  ctx.response.body = responseBody;
});

router.post("/login", async (ctx) => {
  const body: unknown = await ctx.request.body.json();

  if (!isLoginUserRequest(body)) {
    throw new APIException(400, "Invalid request");
  }

  // Per account, so guessing one user's password is slow however many
  // connections it comes from.
  if (!takeToken(`login:${body.username.toLowerCase()}`, LOGIN_LIMIT)) {
    throw new APIException(
      429,
      "Too many login attempts — try again in a minute",
    );
  }

  let user;
  try {
    user = getUserByUsername(body.username);
  } catch {
    user = undefined;
  }
  // An unknown username gets the same answer as a wrong password, after the
  // same work, so neither the message nor the timing tells which exist.
  const valid = await verifyPassword(
    body.password,
    user?.passwordHash ?? await UNKNOWN_USER_HASH,
  );
  if (!user || !valid) {
    throw new APIException(401, "Invalid username or password");
  }

  const responseBody: APIResponse<AuthResponse> = {
    success: true,
    data: { ...await issueTokens(user), user: toSelfUser(user) },
  };
  ctx.response.body = responseBody;
});

router.get("/me", authMiddleware, (ctx: AuthContext) => {
  const responseBody: APIResponse<SelfUser> = {
    success: true,
    data: toSelfUser(getUserById(ctx.state.user.userId)),
  };
  ctx.response.body = responseBody;
});

router.get("/me/media-token", authMiddleware, async (ctx: AuthContext) => {
  const responseBody: APIResponse<MediaTokenResponse> = {
    success: true,
    data: { mediaToken: await createMediaToken(ctx.state.user.userId) },
  };
  ctx.response.body = responseBody;
});

// Answers the same whatever happens, so it can't tell which addresses have an
// account.
router.post("/request-password-reset", async (ctx) => {
  const body: unknown = await ctx.request.body.json();
  const email = fieldOf(body, "email");
  const trimmed = typeof email === "string" ? email.trim() : "";
  if (trimmed) {
    await requestPasswordReset(trimmed).catch((err) =>
      console.error("[request-password-reset]", err)
    );
  }
  const responseBody: APIResponse<null> = { success: true, data: null };
  ctx.response.body = responseBody;
});

router.post("/reset-password", async (ctx) => {
  const body: unknown = await ctx.request.body.json();
  const token = fieldOf(body, "token");
  const newPassword = fieldOf(body, "newPassword");
  if (typeof token !== "string" || typeof newPassword !== "string") {
    throw new APIException(400, "Invalid request");
  }
  await resetPassword(token, newPassword);
  const responseBody: APIResponse<null> = { success: true, data: null };
  ctx.response.body = responseBody;
});

router.post("/me/change-password", authMiddleware, async (ctx: AuthContext) => {
  const body: unknown = await ctx.request.body.json();
  const currentPassword = fieldOf(body, "currentPassword");
  const newPassword = fieldOf(body, "newPassword");

  if (typeof currentPassword !== "string" || typeof newPassword !== "string") {
    throw new APIException(400, "Invalid request");
  }

  if (
    newPassword.length < VALIDATION.PASSWORD_MIN ||
    newPassword.length > VALIDATION.PASSWORD_MAX
  ) {
    throw new APIException(
      400,
      `Password must be ${VALIDATION.PASSWORD_MIN}–${VALIDATION.PASSWORD_MAX} characters`,
    );
  }

  const user = getUserById(ctx.state.user.userId);
  const valid = await verifyPassword(currentPassword, user.passwordHash);
  if (!valid) {
    throw new APIException(403, "Current password is incorrect");
  }

  // Changing the password revokes every token issued before it, this
  // session's included, so hand back fresh ones for the client to keep.
  const updated = await updateUser(ctx.state.user.userId, {
    password: newPassword,
  });
  const responseBody: APIResponse<AuthTokens> = {
    success: true,
    data: await issueTokens(updated),
  };
  ctx.response.body = responseBody;
});

router.patch("/me", authMiddleware, async (ctx: AuthContext) => {
  const body: unknown = await ctx.request.body.json();
  if (!isUpdateUserRequest(body)) {
    throw new APIException(400, "Invalid request");
  }
  // Only the profile fields: a stolen token alone must not change the role,
  // the password (which needs the current one) or the username (which is
  // fixed).
  const updated = await updateUser(ctx.state.user.userId, {
    description: body.description,
    email: body.email,
  });
  const publicUser = toPublicUser(updated);
  broadcastUserUpdated(publicUser);
  const responseBody: APIResponse<PublicUser> = {
    success: true,
    data: publicUser,
  };
  ctx.response.body = responseBody;
});

router.patch(
  "/:userId/role",
  authMiddleware,
  requirePermission("user:manage"),
  async (ctx: AuthContext<"/:userId/role">) => {
    const body: unknown = await ctx.request.body.json();
    const role = fieldOf(body, "role");
    if (!isRole(role)) {
      throw new APIException(400, "Invalid role");
    }
    // So that an admin can't demote themselves by mistake and leave no admin.
    if (ctx.params.userId === ctx.state.user.userId) {
      throw new APIException(400, "Cannot change your own role");
    }
    const updated = await updateUser(ctx.params.userId, { role });
    const publicUser = toPublicUser(updated);
    broadcastUserUpdated(publicUser);
    const responseBody: APIResponse<PublicUser> = {
      success: true,
      data: publicUser,
    };
    ctx.response.body = responseBody;
  },
);

router.get("/search", (ctx) => {
  const q = (ctx.request.url.searchParams.get("q") ?? "").trim();
  const responseBody: APIResponse<UserSuggestion[]> = {
    success: true,
    data: searchUsers(q, 8),
  };
  ctx.response.body = responseBody;
});

router.get("/by-id/:userId", (ctx) => {
  const responseBody: APIResponse<PublicUser> = {
    success: true,
    data: toPublicUser(getUserById(ctx.params.userId)),
  };
  ctx.response.body = responseBody;
});

router.get("/:username/followed-users", (ctx) => {
  const user = getUserByUsername(ctx.params.username);
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const { items, hasMore } = getFollowedUsersByUser(user.id, page, limit);
  const responseBody: APIResponse<PaginatedData<PublicUser>> = {
    success: true,
    data: {
      items: items.map(toPublicUser),
      hasMore,
    },
  };
  ctx.response.body = responseBody;
});

router.get("/:username/followed-playlists", (ctx) => {
  const user = getUserByUsername(ctx.params.username);
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const { items, hasMore } = getFollowedPlaylistsByUser(user.id, page, limit);
  const responseBody: APIResponse<PaginatedData<Playlist>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = responseBody;
});

router.get("/:username/playlists", async (ctx) => {
  const user = getUserByUsername(ctx.params.username);
  const requestingUserId = await parseOptionalAuth(ctx);
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const { items, hasMore } = listPlaylistsByUser(
    user.id,
    requestingUserId,
    page,
    limit,
  );
  const responseBody: APIResponse<PaginatedData<Playlist>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = responseBody;
});

router.get("/:username/invitees", (ctx) => {
  const user = getUserByUsername(ctx.params.username);
  const responseBody: APIResponse<Invitee[]> = {
    success: true,
    data: getInviteTree(user.id),
  };
  ctx.response.body = responseBody;
});

router.get("/:username", (ctx) => {
  const responseBody: APIResponse<PublicUser> = {
    success: true,
    data: toPublicUser(getUserByUsername(ctx.params.username)),
  };
  ctx.response.body = responseBody;
});

router.get("/:username/dumps", async (ctx) => {
  const user = getUserByUsername(ctx.params.username);
  const requestingUserId = await parseOptionalAuth(ctx);
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const includePrivate = requestingUserId === user.id;
  const { items, hasMore } = getDumpsByUser(
    user.id,
    page,
    limit,
    includePrivate,
  );
  const responseBody: APIResponse<PaginatedData<Dump>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = responseBody;
});

router.get("/:username/votes", async (ctx) => {
  const user = getUserByUsername(ctx.params.username);
  const requestingUserId = await parseOptionalAuth(ctx);
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const { items, hasMore } = getVotedDumpsByUser(
    user.id,
    page,
    limit,
    requestingUserId,
  );
  const responseBody: APIResponse<PaginatedData<Dump>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = responseBody;
});

export default router;