import {
  buildMessagingTarget,
  ensureTargetId,
  requireTargetKind,
  type MessagingTarget,
  type MessagingTargetKind,
  type MessagingTargetParseOptions,
} from "../channels/targets.js";

export type DiscordTargetKind = MessagingTargetKind;

export type DiscordTarget = MessagingTarget;

type DiscordTargetParseOptions = MessagingTargetParseOptions;

export function parseDiscordTarget(
  raw: string,
  options: DiscordTargetParseOptions = {},
): DiscordTarget | undefined {
  const trimmed = raw.trim();
  if (!trimmed) return undefined;
  const mentionMatch = trimmed.match(/^<@!?(\d+)>$/);
  if (mentionMatch) {
    return buildMessagingTarget("user", mentionMatch[1], trimmed);
  }
  if (trimmed.startsWith("user:")) {
    const id = trimmed.slice("user:".length).trim();
    return id ? buildMessagingTarget("user", id, trimmed) : undefined;
  }
  if (trimmed.startsWith("channel:")) {
    const id = trimmed.slice("channel:".length).trim();
    return id ? buildMessagingTarget("channel", id, trimmed) : undefined;
  }
  if (trimmed.startsWith("discord:")) {
    const id = trimmed.slice("discord:".length).trim();
    return id ? buildMessagingTarget("user", id, trimmed) : undefined;
  }
  if (trimmed.startsWith("@")) {
    const candidate = trimmed.slice(1).trim();
    const id = ensureTargetId({
      candidate,
      pattern: /^\d+$/,
      errorMessage: "Discord DMs require a user id (use user:<id> or a <@id> mention)",
    });
    return buildMessagingTarget("user", id, trimmed);
  }
  if (/^\d+$/.test(trimmed)) {
    if (options.defaultKind) {
      return buildMessagingTarget(options.defaultKind, trimmed, trimmed);
    }
    throw new Error(
      options.ambiguousMessage ??
        `Ambiguous Discord recipient "${trimmed}". Use "user:${trimmed}" for DMs or "channel:${trimmed}" for channel messages.`,
    );
  }
  return buildMessagingTarget("channel", trimmed, trimmed);
}

export function resolveDiscordChannelId(raw: string): string {
  const target = parseDiscordTarget(raw, { defaultKind: "channel" });
  return requireTargetKind({ platform: "Discord", target, kind: "channel" });
}