/**
 * Proxy API client
 *
 * Handles API requests to GlyphDiff proxy API for fetching font metadata.
 * Provides error handling, pagination support, and type-safe responses.
 *
 * Proxy API normalizes font data from Google Fonts and Fontshare into a single
 * unified format, eliminating the need for client-side normalization.
 *
 * @see https://api.glyphdiff.com/api/v1/fonts
 */

import { api } from '$shared/api/api';
import { buildQueryString } from '$shared/lib/utils';
import type { QueryParams } from '$shared/lib/utils';
import type { UnifiedFont } from '../../model/types';
import type {
    FontCategory,
    FontSubset,
} from '../../model/types';

/**
 * Proxy API base URL
 */
const PROXY_API_URL = 'https://api.glyphdiff.com/api/v1/fonts' as const;

/**
 * Proxy API parameters
 *
 * Maps directly to the proxy API query parameters
 */
export interface ProxyFontsParams extends QueryParams {
    /**
     * Font provider filter ("google" or "fontshare")
     * Omit to fetch from both providers
     */
    provider?: 'google' | 'fontshare';

    /**
     * Font category filter
     */
    category?: FontCategory;

    /**
     * Character subset filter
     */
    subset?: FontSubset;

    /**
     * Search query (e.g., "roboto", "satoshi")
     */
    q?: string;

    /**
     * Sort order for results
     * "name" - Alphabetical by font name
     * "popularity" - Most popular first
     * "lastModified" - Recently updated first
     */
    sort?: 'name' | 'popularity' | 'lastModified';

    /**
     * Number of items to return (pagination)
     */
    limit?: number;

    /**
     * Number of items to skip (pagination)
     * Use for pagination: offset = (page - 1) * limit
     */
    offset?: number;
}

/**
 * Proxy API response
 *
 * Includes pagination metadata alongside font data
 */
export interface ProxyFontsResponse {
    /** Array of unified font objects */
    fonts: UnifiedFont[];

    /** Total number of fonts matching the query */
    total: number;

    /** Limit used for this request */
    limit: number;

    /** Offset used for this request */
    offset: number;
}

/**
 * Fetch fonts from proxy API
 *
 * @param params - Query parameters for filtering and pagination
 * @returns Promise resolving to proxy API response
 * @throws ApiError when request fails
 *
 * @example
 * ```ts
 * // Fetch all sans-serif fonts from Google
 * const response = await fetchProxyFonts({
 *     provider: 'google',
 *     category: 'sans-serif',
 *     limit: 50,
 *     offset: 0
 * });
 *
 * // Search fonts across all providers
 * const searchResponse = await fetchProxyFonts({
 *     q: 'roboto',
 *     limit: 20
 * });
 *
 * // Fetch fonts with pagination
 * const page1 = await fetchProxyFonts({ limit: 50, offset: 0 });
 * const page2 = await fetchProxyFonts({ limit: 50, offset: 50 });
 * ```
 */
export async function fetchProxyFonts(
    params: ProxyFontsParams = {},
): Promise<ProxyFontsResponse> {
    const queryString = buildQueryString(params);
    const url = `${PROXY_API_URL}${queryString}`;

    try {
        const response = await api.get<ProxyFontsResponse>(url);
        return response.data;
    } catch (error) {
        // Re-throw ApiError with context
        if (error instanceof Error) {
            throw error;
        }
        throw new Error(`Failed to fetch fonts from proxy API: ${String(error)}`);
    }
}

/**
 * Fetch font by ID
 *
 * Convenience function for fetching a single font by ID
 * Note: This fetches a page and filters client-side, which is not ideal
 * For production, consider adding a dedicated endpoint to the proxy API
 *
 * @param id - Font ID (family name for Google, slug for Fontshare)
 * @returns Promise resolving to font or undefined
 *
 * @example
 * ```ts
 * const roboto = await fetchProxyFontById('Roboto');
 * const satoshi = await fetchProxyFontById('satoshi');
 * ```
 */
export async function fetchProxyFontById(
    id: string,
): Promise<UnifiedFont | undefined> {
    const response = await fetchProxyFonts({ limit: 1000, q: id });
    return response.fonts.find(font => font.id === id);
}