import type {
  DaemonClient,
  FetchAgentHistoryOptions,
  FetchAgentHistoryPageInfo,
} from "@getpaseo/client/internal/daemon-client";
import { useInfiniteQuery } from "@tanstack/react-query";
import { useCallback, useMemo, useSyncExternalStore } from "react";
import { useTranslation } from "react-i18next";
import type { AggregatedAgent } from "@/hooks/use-aggregated-agents";
import { getHostRuntimeStore, isHostRuntimeConnected, useHosts } from "@/runtime/host-runtime";
import { buildAgentDirectoryState } from "@/utils/agent-directory-sync";
import { agentHistoryQueryKey, allAgentHistoryQueryKey } from "./agent-history-query-key";

const AGENT_HISTORY_PAGE_LIMIT = 200;
const AGENT_HISTORY_SORT: NonNullable<FetchAgentHistoryOptions["sort"]> = [
  { key: "updated_at", direction: "desc" },
];
const AGENT_HISTORY_ALL_HOSTS_FAILED_MESSAGE = "No connected hosts could load agent history";

export interface AgentHistoryResult {
  agents: AggregatedAgent[];
  isLoading: boolean;
  isInitialLoad: boolean;
  isRevalidating: boolean;
  isError: boolean;
  hasMore: boolean;
  isLoadingMore: boolean;
  refreshAll: () => Promise<void>;
  loadMore: () => void;
}

export interface AgentHistoryPage {
  agents: AggregatedAgent[];
  pageInfo: FetchAgentHistoryPageInfo;
}

export type AgentHistoryClient = Pick<DaemonClient, "fetchAgentHistory">;

export interface AgentHistoryHost {
  serverId: string;
  serverLabel: string;
  client: AgentHistoryClient;
}

interface AgentHistoryBatchPage {
  agents: AggregatedAgent[];
  pageInfoByServerId: Record<string, FetchAgentHistoryPageInfo>;
}

type AgentHistoryCursorByServerId = Record<string, string | null>;

export async function fetchAgentHistoryPage(input: {
  client: AgentHistoryClient;
  serverId: string;
  cursor: string | null;
}): Promise<AgentHistoryPage> {
  const payload = await input.client.fetchAgentHistory({
    sort: AGENT_HISTORY_SORT,
    page: input.cursor
      ? { limit: AGENT_HISTORY_PAGE_LIMIT, cursor: input.cursor }
      : { limit: AGENT_HISTORY_PAGE_LIMIT },
  });

  const { agents } = buildAgentDirectoryState({
    serverId: input.serverId,
    entries: payload.entries,
  });

  return {
    agents: Array.from(agents.values(), (agent) => ({
      id: agent.id,
      serverId: input.serverId,
      serverLabel: input.serverId,
      title: agent.title ?? null,
      status: agent.status,
      lastActivityAt: agent.lastActivityAt,
      cwd: agent.cwd,
      workspaceId: agent.workspaceId,
      provider: agent.provider,
      pendingPermissionCount: agent.pendingPermissions.length,
      requiresAttention: agent.requiresAttention,
      attentionReason: agent.attentionReason,
      attentionTimestamp: agent.attentionTimestamp ?? null,
      archivedAt: agent.archivedAt ?? null,
      createdAt: agent.createdAt,
      labels: agent.labels,
      projectPlacement: agent.projectPlacement,
    })),
    pageInfo: payload.pageInfo,
  };
}

function sortByLatestActivity(agents: AggregatedAgent[]): AggregatedAgent[] {
  return [...agents].sort((a, b) => b.lastActivityAt.getTime() - a.lastActivityAt.getTime());
}

function getNextAgentHistoryPageParam(
  page: AgentHistoryBatchPage,
): AgentHistoryCursorByServerId | null {
  const cursorByServerId: AgentHistoryCursorByServerId = {};
  for (const [serverId, pageInfo] of Object.entries(page.pageInfoByServerId)) {
    if (pageInfo.hasMore && pageInfo.nextCursor) {
      cursorByServerId[serverId] = pageInfo.nextCursor;
    }
  }

  return Object.keys(cursorByServerId).length > 0 ? cursorByServerId : null;
}

export async function fetchAgentHistoryBatch(input: {
  hosts: readonly AgentHistoryHost[];
  cursorByServerId: AgentHistoryCursorByServerId | null;
}): Promise<AgentHistoryBatchPage> {
  const cursorByServerId = input.cursorByServerId ?? {};
  const hasCursorFilter = Object.keys(cursorByServerId).length > 0;
  const hostsToFetch = hasCursorFilter
    ? input.hosts.filter((host) => Object.hasOwn(cursorByServerId, host.serverId))
    : input.hosts;

  const settledPages = await Promise.allSettled(
    hostsToFetch.map(async (host) => {
      const page = await fetchAgentHistoryPage({
        client: host.client,
        serverId: host.serverId,
        cursor: cursorByServerId[host.serverId] ?? null,
      });
      return { host, page };
    }),
  );
  const pages = settledPages.flatMap((result) =>
    result.status === "fulfilled" ? [result.value] : [],
  );
  if (pages.length === 0) {
    throw new Error(AGENT_HISTORY_ALL_HOSTS_FAILED_MESSAGE);
  }

  const agents = pages.flatMap(({ host, page }) =>
    page.agents.map((agent) => Object.assign({}, agent, { serverLabel: host.serverLabel })),
  );
  const pageInfoByServerId = Object.fromEntries(
    pages.map(({ host, page }) => [host.serverId, page.pageInfo]),
  );

  return {
    agents: sortByLatestActivity(agents),
    pageInfoByServerId,
  };
}

export function useAgentHistory(options: {
  serverId?: string | null;
  enabled?: boolean;
}): AgentHistoryResult {
  const { t } = useTranslation();
  const daemons = useHosts();
  const runtime = getHostRuntimeStore();
  const runtimeVersion = useSyncExternalStore(
    (onStoreChange) => runtime.subscribeAll(onStoreChange),
    () => runtime.getVersion(),
    () => runtime.getVersion(),
  );
  const serverId = useMemo(() => {
    const value = options.serverId;
    return typeof value === "string" && value.trim().length > 0 ? value.trim() : null;
  }, [options.serverId]);
  const enabled = options.enabled ?? true;
  const targetHosts = useMemo(() => {
    void runtimeVersion;
    const serverLabelById = new Map(daemons.map((daemon) => [daemon.serverId, daemon.label]));
    const serverIds = serverId ? [serverId] : daemons.map((daemon) => daemon.serverId);
    const hosts: AgentHistoryHost[] = [];

    for (const targetServerId of serverIds) {
      const snapshot = runtime.getSnapshot(targetServerId);
      const client = runtime.getClient(targetServerId);
      if (!client || !isHostRuntimeConnected(snapshot)) {
        continue;
      }
      hosts.push({
        serverId: targetServerId,
        serverLabel: serverLabelById.get(targetServerId) ?? targetServerId,
        client,
      });
    }

    return hosts;
  }, [daemons, runtime, runtimeVersion, serverId]);
  const targetServerIds = useMemo(() => targetHosts.map((host) => host.serverId), [targetHosts]);
  const queryKey = useMemo(
    () => (serverId ? agentHistoryQueryKey(serverId) : allAgentHistoryQueryKey(targetServerIds)),
    [serverId, targetServerIds],
  );
  const serverLabelById = useMemo(
    () => new Map(daemons.map((daemon) => [daemon.serverId, daemon.label])),
    [daemons],
  );

  const historyQuery = useInfiniteQuery<
    AgentHistoryBatchPage,
    Error,
    { pages: AgentHistoryBatchPage[] },
    readonly unknown[],
    AgentHistoryCursorByServerId | null
  >({
    queryKey,
    enabled: Boolean(enabled && targetHosts.length > 0),
    staleTime: 30_000,
    initialPageParam: null,
    getNextPageParam: getNextAgentHistoryPageParam,
    queryFn: async ({ pageParam }) => {
      if (targetHosts.length === 0) {
        throw new Error(t("workspace.terminal.hostDisconnected"));
      }
      return fetchAgentHistoryBatch({
        hosts: targetHosts,
        cursorByServerId: pageParam,
      });
    },
  });
  const {
    data,
    fetchNextPage,
    hasNextPage,
    isError,
    isFetching,
    isFetchingNextPage,
    isLoading,
    refetch,
  } = historyQuery;

  const refreshAll = useCallback(async () => {
    if (!enabled || targetHosts.length === 0) {
      return;
    }
    await refetch();
  }, [enabled, refetch, targetHosts.length]);

  const loadMore = useCallback(() => {
    if (!enabled || targetHosts.length === 0 || !hasNextPage || isFetchingNextPage) {
      return;
    }
    void fetchNextPage();
  }, [enabled, fetchNextPage, hasNextPage, isFetchingNextPage, targetHosts.length]);

  const agents = useMemo(() => {
    const historyAgents = (data?.pages ?? []).flatMap((page) => page.agents);
    const labelledAgents = historyAgents.map((agent) =>
      Object.assign({}, agent, {
        serverLabel: serverLabelById.get(agent.serverId) ?? agent.serverLabel,
      }),
    );
    return sortByLatestActivity(labelledAgents);
  }, [data?.pages, serverLabelById]);
  const isInitialLoad = isLoading && agents.length === 0;
  const isRevalidating = isFetching && !isFetchingNextPage && agents.length > 0;

  return {
    agents,
    isLoading,
    isInitialLoad,
    isRevalidating,
    isError,
    hasMore: hasNextPage,
    isLoadingMore: isFetchingNextPage,
    refreshAll,
    loadMore,
  };
}