import type {
  AgentGenerationProject,
  AgentGenerationProjectPersistedState,
} from "@/types/agent";

interface ApiResponse<T = unknown> {
  success: boolean;
  data?: T;
  error?: string;
  status?: number;
}

const AGENT_PROJECT_REQUEST_TIMEOUT_MS = 15_000;

async function fetchAgentProjectApi<T>(
  input: RequestInfo | URL,
  init?: RequestInit
): Promise<ApiResponse<T>> {
  const controller = new AbortController();
  const timeoutId = globalThis.setTimeout(
    () => controller.abort(),
    AGENT_PROJECT_REQUEST_TIMEOUT_MS
  );

  try {
    const response = await fetch(input, {
      ...init,
      signal: controller.signal,
    });
    const result = await response.json();
    if (!response.ok) result.status = response.status;
    return result;
  } finally {
    globalThis.clearTimeout(timeoutId);
  }
}

type CreateProjectPayload = {
  title?: string;
  description?: string | null;
  thumbnail?: string | null;
  projectState?: AgentGenerationProjectPersistedState;
};

const pendingCreations = new Map<string, {
  id: string;
  promise?: Promise<ApiResponse<AgentGenerationProject>>;
}>();

function pendingCreationStorage(key: string, value?: string | null) {
  try {
    if (typeof sessionStorage === "undefined") return null;
    if (value === undefined) return sessionStorage.getItem(key);
    if (value === null) sessionStorage.removeItem(key);
    else sessionStorage.setItem(key, value);
  } catch {
    // Keep the in-memory request identity when browser storage is unavailable.
  }
  return null;
}

function getAgentProjectRequestErrorMessage(error: unknown, fallback: string) {
  if (error instanceof DOMException && error.name === "AbortError") {
    return `${fallback}：请求超时`;
  }
  return fallback;
}

export const agentProjectService = {
  async getProjects(): Promise<ApiResponse<AgentGenerationProject[]>> {
    try {
      return await fetchAgentProjectApi<AgentGenerationProject[]>(
        "/api/agent-projects",
        { cache: "no-store" }
      );
    } catch (error) {
      return {
        success: false,
        error: getAgentProjectRequestErrorMessage(
          error,
          "获取生图项目列表失败"
        ),
      };
    }
  },

  async getProject(id: string): Promise<ApiResponse<AgentGenerationProject>> {
    try {
      return await fetchAgentProjectApi<AgentGenerationProject>(
        `/api/agent-projects/${id}`,
        { cache: "no-store" }
      );
    } catch (error) {
      return {
        success: false,
        error: getAgentProjectRequestErrorMessage(error, "获取生图项目失败"),
      };
    }
  },

  async createProject(
    payload: CreateProjectPayload,
    options: { creationKey?: string } = {}
  ): Promise<ApiResponse<AgentGenerationProject>> {
    const key = `agent-project:create:${options.creationKey || JSON.stringify(payload)}`;
    let pending = pendingCreations.get(key);
    if (!pending) {
      pending = { id: pendingCreationStorage(key) || crypto.randomUUID() };
      pendingCreations.set(key, pending);
      pendingCreationStorage(key, pending.id);
    }
    if (pending.promise) return pending.promise;
    const current = pending;
    const clearPending = () => {
      pendingCreations.delete(key);
      pendingCreationStorage(key, null);
    };
    current.promise = (async () => {
      try {
        const result = await fetchAgentProjectApi<AgentGenerationProject>(
          "/api/agent-projects",
          {
            method: "POST",
            headers: { "Content-Type": "application/json" },
            body: JSON.stringify({ ...payload, id: current.id }),
          }
        );
        if (result.success || (result.status && result.status < 500)) {
          clearPending();
          return result;
        }
      } catch {
        // A lost response does not establish whether the project was created.
      }
      const recovered = await agentProjectService.getProject(current.id);
      if (recovered.success && recovered.data) {
        clearPending();
        return recovered;
      }
      if (recovered.status === 401) return recovered;
      return {
        success: false,
        error: "创建结果尚未确认，请重试核对或打开历史项目；重试不会重复创建。",
      };
    })().finally(() => { current.promise = undefined; });
    return current.promise;
  },

  async updateProject(
    id: string,
    payload: {
      title?: string;
      description?: string | null;
      thumbnail?: string | null;
      projectState?: AgentGenerationProjectPersistedState;
    }
  ): Promise<ApiResponse<AgentGenerationProject>> {
    try {
      return await fetchAgentProjectApi<AgentGenerationProject>(
        `/api/agent-projects/${id}`,
        {
          method: "PUT",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify(payload),
        }
      );
    } catch (error) {
      return {
        success: false,
        error: getAgentProjectRequestErrorMessage(error, "保存生图项目失败"),
      };
    }
  },

  async deleteProject(id: string): Promise<ApiResponse> {
    try {
      return await fetchAgentProjectApi(`/api/agent-projects/${id}`, {
        method: "DELETE",
      });
    } catch (error) {
      return {
        success: false,
        error: getAgentProjectRequestErrorMessage(error, "删除生图项目失败"),
      };
    }
  },
};