const MINECRAFT_USERNAME = /^[A-Za-z0-9_]{3,16}$/;
const MINECRAFT_UUID = /^[0-9a-f]{32}$/i;
const DISCORD_NICKNAME_LIMIT = 32;

export interface JavaProfile {
  uuid: string;
  username: string;
}

export async function lookupJavaProfile(
  username: string,
  request: typeof fetch = fetch,
): Promise<JavaProfile | null> {
  const candidate = username.trim();
  if (!MINECRAFT_USERNAME.test(candidate)) return null;

  const response = await request(
    `https://api.mojang.com/users/profiles/minecraft/${encodeURIComponent(candidate)}`,
    { headers: { accept: "application/json" }, cache: "no-store" },
  );

  if (response.status === 204 || response.status === 404) return null;
  if (!response.ok) throw new Error(`Mojang profile lookup failed (${response.status})`);

  const profile: unknown = await response.json();
  if (!profile || typeof profile !== "object") return null;
  const { id, name } = profile as { id?: unknown; name?: unknown };
  if (typeof id !== "string" || !MINECRAFT_UUID.test(id)) return null;
  if (typeof name !== "string" || !MINECRAFT_USERNAME.test(name)) return null;

  return { uuid: id.toLowerCase(), username: name };
}

export function formatDiscordNickname(firstName: string, minecraftUsername: string) {
  const suffix = ` (${minecraftUsername})`;
  const availableCharacters = DISCORD_NICKNAME_LIMIT - [...suffix].length;
  const shortenedName = [...firstName.trim()].slice(0, Math.max(1, availableCharacters)).join("").trimEnd();
  return `${shortenedName}${suffix}`;
}

export function formatManagedDiscordNickname(
  firstName: string,
  minecraftUsername: string | null,
) {
  if (minecraftUsername) return formatDiscordNickname(firstName, minecraftUsername);
  return formatDiscordNickname(firstName, "TBD");
}

export interface DiscordGuildIdentity {
  id: string;
  username: string;
  globalName: string | null;
  nickname: string | null;
}

export async function getGuildMemberIdentity(
  input: { guildId: string; discordUserId: string; botToken: string },
  request: typeof fetch = fetch,
): Promise<DiscordGuildIdentity> {
  const response = await request(
    `https://discord.com/api/v10/guilds/${input.guildId}/members/${input.discordUserId}`,
    {
      headers: {
        authorization: `Bot ${input.botToken}`,
        accept: "application/json",
      },
      cache: "no-store",
    },
  );
  if (!response.ok) throw new Error(`Discord guild member lookup failed (${response.status})`);

  const payload: unknown = await response.json();
  if (!payload || typeof payload !== "object") throw new Error("Discord guild member lookup returned invalid data");
  const member = payload as { nick?: unknown; user?: unknown };
  if (!member.user || typeof member.user !== "object") throw new Error("Discord guild member lookup omitted user data");
  const user = member.user as { id?: unknown; username?: unknown; global_name?: unknown };
  if (typeof user.id !== "string" || typeof user.username !== "string") {
    throw new Error("Discord guild member lookup returned invalid user data");
  }

  return {
    id: user.id,
    username: user.username,
    globalName: typeof user.global_name === "string" ? user.global_name : null,
    nickname: typeof member.nick === "string" ? member.nick : null,
  };
}

export async function updateGuildNickname(
  input: {
    guildId: string;
    discordUserId: string;
    nickname: string;
    botToken: string;
  },
  request: typeof fetch = fetch,
) {
  const response = await request(
    `https://discord.com/api/v10/guilds/${input.guildId}/members/${input.discordUserId}`,
    {
      method: "PATCH",
      headers: {
        authorization: `Bot ${input.botToken}`,
        "content-type": "application/json",
      },
      body: JSON.stringify({ nick: input.nickname }),
    },
  );

  if (!response.ok) {
    throw new Error(`Discord nickname update failed (${response.status})`);
  }
}