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

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 isAcpSessionKey(sessionKey: string | undefined | null): boolean {
  const raw = (sessionKey ?? "").trim();
  if (!raw) {
    return false;
  }
  const normalized = raw.toLowerCase();
  if (normalized.startsWith("acp:")) {
    return true;
  }
  const parsed = parseAgentSessionKey(raw);
  return Boolean((parsed?.rest ?? "").toLowerCase().startsWith("acp:"));
}

const THREAD_SESSION_MARKERS = [":thread:", ":topic:"];

export function resolveThreadParentSessionKey(
  sessionKey: string | undefined | null,
): string | null {
  const raw = (sessionKey ?? "").trim();
  if (!raw) {
    return null;
  }
  const normalized = raw.toLowerCase();
  let idx = -1;
  for (const marker of THREAD_SESSION_MARKERS) {
    const candidate = normalized.lastIndexOf(marker);
    if (candidate > idx) {
      idx = candidate;
    }
  }
  if (idx <= 0) {
    return null;
  }
  const parent = raw.slice(0, idx).trim();
  return parent ? parent : null;
}