export type AgentActivityTraceKind = "activity" | "think";
export type AgentActivityTraceStatus = "live" | "done";

export type AgentActivityTraceItem = Readonly<{
  id: string;
  kind: AgentActivityTraceKind;
  status: AgentActivityTraceStatus;
  label: string;
  text?: string;
  startedAt?: number;
  tool?: string;
}>;

const THINKING_TEXT_LIMIT = 8_000;

export function emptyActivityTrace(): readonly AgentActivityTraceItem[] {
  return [];
}

export function appendActivityTraceThinking(
  rows: readonly AgentActivityTraceItem[],
  text: string,
): readonly AgentActivityTraceItem[] {
  if (!text) return rows;
  const last = rows.at(-1);
  if (last?.kind === "think" && last.status === "live") {
    return rows.map((row, index) => (
      index === rows.length - 1
        ? { ...row, text: `${row.text ?? ""}${text}`.slice(0, THINKING_TEXT_LIMIT) }
        : row
    ));
  }
  const frozen = freezeLiveThink(rows);
  const thinkCount = frozen.filter((row) => row.kind === "think").length;
  return [
    ...frozen,
    {
      id: `think-${thinkCount + 1}`,
      kind: "think",
      status: "live",
      label: "思考",
      text: text.slice(0, THINKING_TEXT_LIMIT),
    },
  ];
}

export function startActivityTraceStep(
  rows: readonly AgentActivityTraceItem[],
  tool: string,
  label: string,
  startedAt = Date.now(),
): readonly AgentActivityTraceItem[] {
  const frozen = freezeLiveThink(rows);
  const last = frozen.at(-1);
  if (last?.kind === "activity" && last.status === "live" && last.tool === tool) {
    return frozen;
  }
  const closed = frozen.map((row) => (
    row.kind === "activity" && row.status === "live" ? { ...row, status: "done" as const } : row
  ));
  const toolCount = closed.filter((row) => row.kind === "activity" && row.tool === tool).length;
  return [
    ...closed,
    {
      id: `activity-${tool}-${toolCount + 1}`,
      kind: "activity",
      status: "live",
      label,
      startedAt,
      tool,
    },
  ];
}

export function completeActivityTraceStep(
  rows: readonly AgentActivityTraceItem[],
  tool: string,
  label?: string,
): readonly AgentActivityTraceItem[] {
  for (let index = rows.length - 1; index >= 0; index -= 1) {
    const row = rows[index];
    if (row?.kind === "activity" && row.tool === tool && row.status === "live") {
      return rows.map((item, current) => (
        current === index
          ? { ...item, status: "done" as const, label: label ?? item.label }
          : item
      ));
    }
  }
  return rows;
}

export function freezeLiveThink(
  rows: readonly AgentActivityTraceItem[],
): readonly AgentActivityTraceItem[] {
  return rows.map((row) => (
    row.kind === "think" && row.status === "live" ? { ...row, status: "done" as const } : row
  ));
}

export function completeActivityTrace(
  rows: readonly AgentActivityTraceItem[],
): readonly AgentActivityTraceItem[] {
  return freezeLiveThink(rows).map((row) => (
    row.status === "live" ? { ...row, status: "done" as const } : row
  ));
}