/**
 * Service for fetching Google Fonts
 *
 * Integrates with TanStack Query for caching, deduplication,
 * and automatic refetching.
 *
 * Uses reactive query args pattern for Svelte 5 compatibility.
 */

import type {
    FontCategory,
    FontSubset,
} from '$entities/Font';
import { fetchGoogleFonts } from '$entities/Font/api/googleFonts';
import { normalizeGoogleFonts } from '$entities/Font/api/normalize';
import type { UnifiedFont } from '$entities/Font/api/normalize';
import type { QueryFunction } from '@tanstack/svelte-query';
import {
    createQuery,
    useQueryClient,
} from '@tanstack/svelte-query';

/**
 * Google Fonts query parameters
 */
export interface GoogleFontsQueryParams {
    /** Font category filter */
    category?: FontCategory;
    /** Character subset filter */
    subset?: FontSubset;
    /** Sort order */
    sort?: 'popularity' | 'alpha' | 'date';
    /** Search query (for specific font) */
    search?: string;
    /** Force refetch even if cached */
    forceRefetch?: boolean;
}

/**
 * Query key factory for Google Fonts
 * Generates consistent query keys for cache management
 */
export function getGoogleFontsQueryKey(
    params: GoogleFontsQueryParams,
): readonly unknown[] {
    return ['googleFonts', params];
}

/**
 * Query function for fetching Google Fonts
 * Handles caching, loading states, and errors
 */
export const fetchGoogleFontsQuery: QueryFunction<
    UnifiedFont[],
    readonly unknown[]
> = async ({ queryKey }) => {
    const params = queryKey[1] as GoogleFontsQueryParams;

    try {
        const response = await fetchGoogleFonts({
            category: params.category,
            subset: params.subset,
            sort: params.sort,
        });

        const normalizedFonts = normalizeGoogleFonts(response.items);
        return normalizedFonts;
    } catch (error) {
        // User-friendly error messages
        if (error instanceof Error) {
            if (error.message.includes('Failed to fetch')) {
                throw new Error(
                    'Unable to connect to Google Fonts. Please check your internet connection and try again.',
                );
            }
            if (error.message.includes('404')) {
                throw new Error('Font not found in Google Fonts catalog.');
            }
            throw new Error(
                'Failed to load fonts from Google Fonts. Please try again later.',
            );
        }
        throw new Error('An unexpected error occurred while fetching fonts.');
    }
};

/**
 * Create a Google Fonts query hook
 * Use this in Svelte components to fetch Google Fonts with caching
 *
 * @param params - Query parameters
 * @returns Query result with data, loading state, and error
 *
 * @example
 * ```svelte
 * <script lang="ts">
 *   let { category }: { category?: FontCategory } = $props();
 *
 *   const query = useGoogleFontsQuery({ category });
 *
 *   if ($query.isLoading) {
 *     return <LoadingSpinner />;
 *   }
 *
 *   if ($query.error) {
 *     return <ErrorMessage message={$query.error.message} />;
 *   }
 *
 *   const fonts = $query.data ?? [];
 * </script>
 *
 * {#each fonts as font}
 *   <FontCard {font} />
 * {/each}
 * ```
 */
export function useGoogleFontsQuery(params: GoogleFontsQueryParams = {}) {
    const queryClient = useQueryClient();

    const query = createQuery(() => ({
        queryKey: getGoogleFontsQueryKey(params),
        queryFn: fetchGoogleFontsQuery,
        staleTime: 5 * 60 * 1000, // 5 minutes
        gcTime: 10 * 60 * 1000, // 10 minutes
    }));

    return query;
}

/**
 * Prefetch Google Fonts
 * Fetch fonts in background without showing loading state
 *
 * @param params - Query parameters for prefetch
 *
 * @example
 * ```ts
 * // Prefetch fonts when user hovers over button
 * function onMouseEnter() {
 *     prefetchGoogleFonts({ category: 'sans-serif' });
 * }
 * ```
 */
export async function prefetchGoogleFonts(
    params: GoogleFontsQueryParams = {},
): Promise<void> {
    const queryClient = useQueryClient();

    await queryClient.prefetchQuery({
        queryKey: getGoogleFontsQueryKey(params),
        queryFn: fetchGoogleFontsQuery,
        staleTime: 5 * 60 * 1000,
    });
}

/**
 * Invalidate Google Fonts cache
 * Forces refetch on next query
 *
 * @param params - Query parameters to invalidate (all if not provided)
 *
 * @example
 * ```ts
 * // Invalidate all Google Fonts cache
 * invalidateGoogleFonts();
 *
 * // Invalidate specific category cache
 * invalidateGoogleFonts({ category: 'sans-serif' });
 * ```
 */
export function invalidateGoogleFonts(
    params?: GoogleFontsQueryParams,
): void {
    const queryClient = useQueryClient();

    if (params) {
        queryClient.invalidateQueries({
            queryKey: getGoogleFontsQueryKey(params),
        });
    } else {
        queryClient.invalidateQueries({
            queryKey: ['googleFonts'],
        });
    }
}

/**
 * Cancel Google Fonts queries
 * Abort in-flight requests
 *
 * @param params - Query parameters to cancel (all if not provided)
 *
 * @example
 * ```ts
 * // Cancel all Google Fonts queries
 * cancelGoogleFontsQueries();
 * ```
 */
export function cancelGoogleFontsQueries(
    params?: GoogleFontsQueryParams,
): void {
    const queryClient = useQueryClient();

    if (params) {
        queryClient.cancelQueries({
            queryKey: getGoogleFontsQueryKey(params),
        });
    } else {
        queryClient.cancelQueries({
            queryKey: ['googleFonts'],
        });
    }
}