export type WhisperGateConfig = {
  enabled?: boolean;
  discordOnly?: boolean;
  listMode?: "human-list" | "agent-list";
  humanList?: string[];
  agentList?: string[];
  channelPolicies?: Record<
    string,
    {
      listMode?: "human-list" | "agent-list";
      humanList?: string[];
      agentList?: string[];
      endSymbols?: 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] : "";
}

function resolvePolicy(config: WhisperGateConfig, channelId?: string) {
  const globalMode = config.listMode || "human-list";
  const globalHuman = config.humanList || config.bypassUserIds || [];
  const globalAgent = config.agentList || [];
  const globalEnd = config.endSymbols || ["🔚"];

  if (!channelId) {
    return { listMode: globalMode, humanList: globalHuman, agentList: globalAgent, endSymbols: globalEnd };
  }

  const cp = config.channelPolicies || {};
  const scoped = cp[channelId];
  if (!scoped) {
    return { listMode: globalMode, humanList: globalHuman, agentList: globalAgent, endSymbols: globalEnd };
  }

  return {
    listMode: scoped.listMode || globalMode,
    humanList: scoped.humanList || globalHuman,
    agentList: scoped.agentList || globalAgent,
    endSymbols: scoped.endSymbols || globalEnd,
  };
}

export function evaluateDecision(params: {
  config: WhisperGateConfig;
  channel?: string;
  channelId?: 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 policy = resolvePolicy(config, params.channelId);

  const mode = policy.listMode;
  const humanList = policy.humanList;
  const agentList = policy.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 && policy.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" };
}