export type WhisperGateConfig = {
  enabled?: boolean;
  discordOnly?: boolean;
  listMode?: "human-list" | "agent-list";
  humanList?: string[];
  agentList?: string[];
  // backward compatibility
  bypassUserIds?: string[];
  endSymbols?: string[];
  noReplyProvider: string;
  noReplyModel: string;
};

export type Decision = {
  shouldUseNoReply: boolean;
  reason: string;
};

function getLastChar(input: string): string {
  const t = input.trim();
  return t.length ? t[t.length - 1] : "";
}

export function evaluateDecision(params: {
  config: WhisperGateConfig;
  channel?: string;
  senderId?: string;
  content?: string;
}): Decision {
  const { config } = params;

  if (config.enabled === false) {
    return { shouldUseNoReply: false, reason: "disabled" };
  }

  const channel = (params.channel || "").toLowerCase();
  if (config.discordOnly !== false && channel !== "discord") {
    return { shouldUseNoReply: false, reason: "non_discord" };
  }

  const mode = config.listMode || "human-list";
  const humanList = config.humanList || config.bypassUserIds || [];
  const agentList = config.agentList || [];

  const senderId = params.senderId || "";
  const inHumanList = !!senderId && humanList.includes(senderId);
  const inAgentList = !!senderId && agentList.includes(senderId);

  const lastChar = getLastChar(params.content || "");
  const hasEnd = !!lastChar && (config.endSymbols || []).includes(lastChar);

  if (mode === "human-list") {
    if (inHumanList) {
      return { shouldUseNoReply: false, reason: "human_list_sender" };
    }
    if (hasEnd) {
      return { shouldUseNoReply: false, reason: `end_symbol:${lastChar}` };
    }
    return { shouldUseNoReply: true, reason: "rule_match_no_end_symbol" };
  }

  // agent-list mode: listed senders require end symbol; others bypass requirement.
  if (!inAgentList) {
    return { shouldUseNoReply: false, reason: "non_agent_list_sender" };
  }
  if (hasEnd) {
    return { shouldUseNoReply: false, reason: `end_symbol:${lastChar}` };
  }
  return { shouldUseNoReply: true, reason: "agent_list_missing_end_symbol" };
}