export const DEFAULT_AGENT_ID = "main";
export const DEFAULT_MAIN_KEY = "main";
export const DEFAULT_ACCOUNT_ID = "default";

export type ParsedAgentSessionKey = {
  agentId: string;
  rest: string;
};

export function resolveAgentIdFromSessionKey(
  sessionKey: string | undefined | null,
): string {
  const parsed = parseAgentSessionKey(sessionKey);
  return normalizeAgentId(parsed?.agentId ?? DEFAULT_AGENT_ID);
}

export function normalizeAgentId(value: string | undefined | null): string {
  const trimmed = (value ?? "").trim();
  if (!trimmed) return DEFAULT_AGENT_ID;
  // Keep it path-safe + shell-friendly.
  if (/^[a-z0-9][a-z0-9_-]{0,63}$/i.test(trimmed)) return trimmed;
  // Best-effort fallback: collapse invalid characters to "-"
  return (
    trimmed
      .toLowerCase()
      .replace(/[^a-z0-9_-]+/g, "-")
      .replace(/^-+/, "")
      .replace(/-+$/, "")
      .slice(0, 64) || DEFAULT_AGENT_ID
  );
}

export function normalizeAccountId(value: string | undefined | null): string {
  const trimmed = (value ?? "").trim();
  if (!trimmed) return DEFAULT_ACCOUNT_ID;
  if (/^[a-z0-9][a-z0-9_-]{0,63}$/i.test(trimmed)) return trimmed;
  return (
    trimmed
      .toLowerCase()
      .replace(/[^a-z0-9_-]+/g, "-")
      .replace(/^-+/, "")
      .replace(/-+$/, "")
      .slice(0, 64) || DEFAULT_ACCOUNT_ID
  );
}

export function parseAgentSessionKey(
  sessionKey: string | undefined | null,
): ParsedAgentSessionKey | null {
  const raw = (sessionKey ?? "").trim();
  if (!raw) return null;
  const parts = raw.split(":").filter(Boolean);
  if (parts.length < 3) return null;
  if (parts[0] !== "agent") return null;
  const agentId = parts[1]?.trim();
  const rest = parts.slice(2).join(":");
  if (!agentId || !rest) return null;
  return { agentId, rest };
}

export function isSubagentSessionKey(
  sessionKey: string | undefined | null,
): boolean {
  const raw = (sessionKey ?? "").trim();
  if (!raw) return false;
  if (raw.toLowerCase().startsWith("subagent:")) return true;
  const parsed = parseAgentSessionKey(raw);
  return Boolean((parsed?.rest ?? "").toLowerCase().startsWith("subagent:"));
}

export function buildAgentMainSessionKey(params: {
  agentId: string;
  mainKey?: string | undefined;
}): string {
  const agentId = normalizeAgentId(params.agentId);
  const mainKey =
    (params.mainKey ?? DEFAULT_MAIN_KEY).trim() || DEFAULT_MAIN_KEY;
  return `agent:${agentId}:${mainKey}`;
}

export function buildAgentPeerSessionKey(params: {
  agentId: string;
  mainKey?: string | undefined;
  provider: string;
  peerKind?: "dm" | "group" | "channel" | null;
  peerId?: string | null;
}): string {
  const peerKind = params.peerKind ?? "dm";
  if (peerKind === "dm") {
    return buildAgentMainSessionKey({
      agentId: params.agentId,
      mainKey: params.mainKey,
    });
  }
  const provider = (params.provider ?? "").trim().toLowerCase() || "unknown";
  const peerId = (params.peerId ?? "").trim() || "unknown";
  return `agent:${normalizeAgentId(params.agentId)}:${provider}:${peerKind}:${peerId}`;
}

export function resolveThreadSessionKeys(params: {
  baseSessionKey: string;
  threadId?: string | null;
  parentSessionKey?: string;
  useSuffix?: boolean;
}): { sessionKey: string; parentSessionKey?: string } {
  const threadId = (params.threadId ?? "").trim();
  if (!threadId) {
    return { sessionKey: params.baseSessionKey, parentSessionKey: undefined };
  }
  const useSuffix = params.useSuffix ?? true;
  const sessionKey = useSuffix
    ? `${params.baseSessionKey}:thread:${threadId}`
    : params.baseSessionKey;
  return { sessionKey, parentSessionKey: params.parentSessionKey };
}