/**
 * TanStack Query data fetching layer.
 *
 * Handles async data fetching, caching, and invalidation for:
 * - Lore status (GitLab integration health)
 * - Bridge status (mapping counts, sync times)
 * - Sync/reconcile mutations
 *
 * Query keys are centralized here for consistent invalidation.
 */

import { useEffect } from "react";
import {
  QueryClient,
  useQuery,
  useMutation,
  useQueryClient,
  type UseQueryResult,
  type UseMutationResult,
} from "@tanstack/react-query";
import { invoke } from "@tauri-apps/api/core";
import type { UnlistenFn } from "@tauri-apps/api/event";
import { events } from "@/lib/bindings";
import type {
  LoreStatus,
  BridgeStatus,
  SyncResult,
  McError,
  FocusItem,
} from "@/lib/types";
import type { LoreItemsResponse } from "@/lib/bindings";

// --- Query Keys ---

export const queryKeys = {
  loreStatus: ["lore-status"] as const,
  bridgeStatus: ["bridge-status"] as const,
  loreItems: ["lore-items"] as const,
} as const;

// --- QueryClient Factory ---

/**
 * Create a configured QueryClient instance.
 *
 * Default options:
 * - retry: 1 (one retry on failure)
 * - refetchOnWindowFocus: true (refresh when user returns)
 */
export function createQueryClient(): QueryClient {
  return new QueryClient({
    defaultOptions: {
      queries: {
        retry: 1,
        refetchOnWindowFocus: true,
      },
    },
  });
}

// --- Event-Based Invalidation Hook ---

/**
 * Hook to set up query invalidation on Tauri events.
 *
 * Listens for:
 * - loreDataChanged: Invalidates lore and bridge status
 */
export function useQueryInvalidation(): void {
  const queryClient = useQueryClient();

  useEffect(() => {
    let cancelled = false;
    let unlisten: UnlistenFn | undefined;

    // Invalidate on lore data changes (typed event)
    events.loreDataChanged
      .listen(() => {
        queryClient.invalidateQueries({ queryKey: queryKeys.loreStatus });
        queryClient.invalidateQueries({ queryKey: queryKeys.bridgeStatus });
      })
      .then((fn) => {
        if (cancelled) {
          fn();
        } else {
          unlisten = fn;
        }
      });

    return () => {
      cancelled = true;
      if (unlisten) unlisten();
    };
  }, [queryClient]);
}

// --- Query Hooks ---

/**
 * Fetch lore integration status.
 *
 * Returns health, last sync time, and summary counts.
 * Stale time: 30 seconds (fresh data is important but not real-time)
 */
export function useLoreStatus(): UseQueryResult<LoreStatus, McError> {
  const queryClient = useQueryClient();

  // Set up event-based invalidation (typed event)
  useEffect(() => {
    let cancelled = false;
    let unlisten: UnlistenFn | undefined;

    events.loreDataChanged
      .listen(() => {
        queryClient.invalidateQueries({ queryKey: queryKeys.loreStatus });
      })
      .then((fn) => {
        if (cancelled) {
          fn();
        } else {
          unlisten = fn;
        }
      });

    return () => {
      cancelled = true;
      if (unlisten) unlisten();
    };
  }, [queryClient]);

  return useQuery({
    queryKey: queryKeys.loreStatus,
    queryFn: () => invoke<LoreStatus>("get_lore_status"),
    staleTime: 30 * 1000, // 30 seconds
  });
}

/**
 * Fetch bridge status (mapping counts, sync times).
 *
 * Stale time: 30 seconds
 */
export function useBridgeStatus(): UseQueryResult<BridgeStatus, McError> {
  const queryClient = useQueryClient();

  // Set up event-based invalidation (typed event)
  useEffect(() => {
    let cancelled = false;
    let unlisten: UnlistenFn | undefined;

    events.loreDataChanged
      .listen(() => {
        queryClient.invalidateQueries({ queryKey: queryKeys.bridgeStatus });
      })
      .then((fn) => {
        if (cancelled) {
          fn();
        } else {
          unlisten = fn;
        }
      });

    return () => {
      cancelled = true;
      if (unlisten) unlisten();
    };
  }, [queryClient]);

  return useQuery({
    queryKey: queryKeys.bridgeStatus,
    queryFn: () => invoke<BridgeStatus>("get_bridge_status"),
    staleTime: 30 * 1000, // 30 seconds
  });
}

// --- Mutation Hooks ---

/**
 * Trigger an incremental sync (process since_last_check events).
 *
 * On success, invalidates lore and bridge status queries.
 */
export function useSyncNow(): UseMutationResult<SyncResult, McError, void> {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: () => invoke<SyncResult>("sync_now"),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: queryKeys.loreStatus });
      queryClient.invalidateQueries({ queryKey: queryKeys.bridgeStatus });
    },
  });
}

/**
 * Trigger a full reconciliation pass.
 *
 * On success, invalidates lore and bridge status queries.
 */
export function useReconcile(): UseMutationResult<SyncResult, McError, void> {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: () => invoke<SyncResult>("reconcile"),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: queryKeys.loreStatus });
      queryClient.invalidateQueries({ queryKey: queryKeys.bridgeStatus });
    },
  });
}

// --- Lore Items Query ---

/**
 * Transform raw LoreItemsResponse into FocusItem array.
 */
function transformLoreItems(response: LoreItemsResponse): FocusItem[] {
  if (!response.success || !response.items) {
    return [];
  }

  return response.items.map((item) => ({
    id: item.id,
    title: item.title,
    type: item.item_type as FocusItem["type"],
    project: item.project,
    url: item.url,
    iid: item.iid,
    updatedAt: item.updated_at ?? null,
    contextQuote: null,
    requestedBy: item.requested_by ?? null,
    snoozedUntil: null,
  }));
}

/**
 * Fetch lore items and transform to FocusItem format.
 *
 * Returns work items from GitLab (reviews, issues, authored MRs).
 * Stale time: 30 seconds
 */
export function useLoreItems(): UseQueryResult<FocusItem[], McError> {
  const queryClient = useQueryClient();

  // Set up event-based invalidation (typed event)
  useEffect(() => {
    let cancelled = false;
    let unlisten: UnlistenFn | undefined;

    events.loreDataChanged
      .listen(() => {
        queryClient.invalidateQueries({ queryKey: queryKeys.loreItems });
      })
      .then((fn) => {
        if (cancelled) {
          fn();
        } else {
          unlisten = fn;
        }
      });

    return () => {
      cancelled = true;
      if (unlisten) unlisten();
    };
  }, [queryClient]);

  return useQuery({
    queryKey: queryKeys.loreItems,
    queryFn: async () => {
      const response = await invoke<LoreItemsResponse>("get_lore_items");
      return transformLoreItems(response);
    },
    staleTime: 30 * 1000, // 30 seconds
  });
}