/**
 * 标准 Tool Call 的纯状态机。
 *
 * `call_id` 是唯一关联键，只允许声明性 choice、confirm、input 在合法生命周期内迁移；
 * 本模块不渲染、不写 Store、不联网，实际结果发送由 Runtime Action/outbox 完成。
 */
import type {
  JsonObject,
  ToolCallCancel,
  ToolCallFinalStatus,
  ToolCallRequest,
  ToolCallResult,
} from "@/runtime/protocol/lineup-v1";

export type ToolCallStatus = "pending" | "submitted" | ToolCallFinalStatus;

export type ToolCallRecord = {
  call_id: string;
  conversation_id: string;
  /** Runtime binding for ordinary MiniApp Tools; absent for Interact calls. */
  app_scope?: string;
  instance_id?: string;
  request: ToolCallRequest;
  status: ToolCallStatus;
  created_at: string;
  updated_at: string;
  result?: JsonObject;
  submission?: JsonObject;
  error?: string;
};

export type ToolCallTransition =
  | { disposition: "accepted"; record: ToolCallRecord }
  | { disposition: "duplicate" | "invalid_transition" | "missing"; record?: ToolCallRecord };

/**
 * Platform-neutral state machine for trusted standard interaction calls.
 * It has no UI, persistence, Transport, capability, or side-effect handler;
 * later M1 tasks connect those boundaries through this explicit lifecycle.
 */
export class ToolCallStateMachine {
  private readonly calls = new Map<string, ToolCallRecord>();

  public receive(request: ToolCallRequest, conversationID: string, receivedAt: string): ToolCallTransition {
    const existing = this.calls.get(request.call_id);
    if (existing) return { disposition: "duplicate", record: copy(existing) };
    const expired = request.expires_at !== undefined && Date.parse(request.expires_at) <= Date.parse(receivedAt);
    const record: ToolCallRecord = {
      call_id: request.call_id,
      conversation_id: conversationID,
      request: { ...request, data: { ...request.data } },
      status: expired ? "expired" : "pending",
      created_at: receivedAt,
      updated_at: receivedAt,
    };
    this.calls.set(record.call_id, record);
    return { disposition: "accepted", record: copy(record) };
  }

  public submit(callID: string, updatedAt: string, submission: JsonObject = {}): ToolCallTransition {
    const record = this.calls.get(callID);
    if (record?.request.expires_at && Date.parse(record.request.expires_at) <= Date.parse(updatedAt) && (record.status === "pending" || record.status === "submitted")) {
      record.status = "expired";
      record.updated_at = updatedAt;
      return { disposition: "invalid_transition", record: copy(record) };
    }
    return this.transition(callID, updatedAt, ["pending"], record => {
      record.status = "submitted";
      record.submission = { ...submission };
    });
  }

  public complete(result: ToolCallResult, updatedAt: string): ToolCallTransition {
    return this.transition(result.call_id, updatedAt, ["submitted"], record => {
      record.status = result.status;
      record.result = { ...result.result };
      record.error = result.error;
    });
  }

  public cancel(cancel: ToolCallCancel, updatedAt: string): ToolCallTransition {
    return this.transition(cancel.call_id, updatedAt, ["pending", "submitted"], record => {
      record.status = "cancelled";
      record.error = cancel.reason || undefined;
    });
  }

  public expireCall(callID: string, now: string): ToolCallTransition {
    const record = this.calls.get(callID);
    if (!record) return { disposition: "missing" };
    if ((record.status !== "pending" && record.status !== "submitted") || !record.request.expires_at || Date.parse(record.request.expires_at) > Date.parse(now)) {
      return { disposition: "invalid_transition", record: copy(record) };
    }
    record.status = "expired";
    record.updated_at = now;
    return { disposition: "accepted", record: copy(record) };
  }

  public expire(now: string): readonly ToolCallRecord[] {
    const changed: ToolCallRecord[] = [];
    const nowTime = Date.parse(now);
    for (const record of this.calls.values()) {
      if ((record.status === "pending" || record.status === "submitted") && record.request.expires_at && Date.parse(record.request.expires_at) <= nowTime) {
        record.status = "expired";
        record.updated_at = now;
        changed.push(copy(record));
      }
    }
    return changed;
  }

  public get(callID: string): ToolCallRecord | undefined {
    const record = this.calls.get(callID);
    return record ? copy(record) : undefined;
  }

  public snapshot(): readonly ToolCallRecord[] {
    return [...this.calls.values()].map(copy);
  }

  public reset(): void {
    this.calls.clear();
  }

  /** Restores trusted local cache records for the current conversation only. */
  public restore(records: readonly ToolCallRecord[], now: string): void {
    this.calls.clear();
    for (const record of records) {
      if (!isRestoreableRecord(record) || this.calls.has(record.call_id)) continue;
      const restored = copy(record);
      if ((restored.status === "pending" || restored.status === "submitted") && restored.request.expires_at && Date.parse(restored.request.expires_at) <= Date.parse(now)) {
        restored.status = "expired";
        restored.updated_at = now;
      }
      this.calls.set(restored.call_id, restored);
    }
  }

  private transition(
    callID: string,
    updatedAt: string,
    allowed: readonly ToolCallStatus[],
    apply: (record: ToolCallRecord) => void,
  ): ToolCallTransition {
    const record = this.calls.get(callID);
    if (!record) return { disposition: "missing" };
    if (!allowed.includes(record.status)) return { disposition: "invalid_transition", record: copy(record) };
    apply(record);
    record.updated_at = updatedAt;
    return { disposition: "accepted", record: copy(record) };
  }
}

function isRestoreableRecord(value: unknown): value is ToolCallRecord {
  if (!value || typeof value !== "object" || Array.isArray(value)) return false;
  const record = value as Partial<ToolCallRecord>;
  if (typeof record.call_id !== "string" || !record.call_id || typeof record.conversation_id !== "string" || !record.conversation_id || !record.request || typeof record.request !== "object") return false;
  if (record.request.call_id !== record.call_id || !["choice", "confirm", "input"].includes(record.request.tool) || !record.request.data || typeof record.request.data !== "object" || Array.isArray(record.request.data)) return false;
  if (!["pending", "submitted", "completed", "failed", "cancelled", "expired"].includes(record.status ?? "") || typeof record.created_at !== "string" || typeof record.updated_at !== "string") return false;
  return !Number.isNaN(Date.parse(record.created_at)) && !Number.isNaN(Date.parse(record.updated_at));
}

function copy(record: ToolCallRecord): ToolCallRecord {
  return {
    ...record,
    request: { ...record.request, data: { ...record.request.data } },
    ...(record.result ? { result: { ...record.result } } : {}),
    ...(record.submission ? { submission: { ...record.submission } } : {}),
  };
}