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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 | /** * Image Preloading Hook * * Preload images before they're needed in the UI. * Useful for image galleries, slideshows, or critical images. * * @example * // Single image * const { isLoaded, isLoading } = useImagePreload({ src: heroImage }); * * @example * // Multiple images with progress * const { isLoaded, progress, hasError } = useImagePreload({ * src: [img1, img2, img3], * onLoad: () => console.log('All images loaded'), * }); */ import { useEffect, useState, useCallback, useRef } from 'react'; interface UseImagePreloadOptions { /** Image URL or array of URLs to preload */ src: string | string[]; /** Callback when all images are loaded */ onLoad?: () => void; /** Callback when an image fails to load */ onError?: (error: Error) => void; /** Whether to start preloading immediately (default: true) */ enabled?: boolean; } interface ImagePreloadState { /** Whether images are currently loading */ isLoading: boolean; /** Whether all images have loaded successfully */ isLoaded: boolean; /** Whether any image failed to load */ hasError: boolean; /** Loading progress (0-100) */ progress: number; /** Number of images loaded */ loadedCount: number; /** Total number of images */ totalCount: number; /** Error message if any */ error: string | null; } interface UseImagePreloadReturn extends ImagePreloadState { /** Manually trigger preloading (useful when enabled=false) */ preload: () => void; /** Reset state and cancel pending loads */ reset: () => void; } const initialState: ImagePreloadState = { isLoading: false, isLoaded: false, hasError: false, progress: 0, loadedCount: 0, totalCount: 0, error: null, }; export function useImagePreload({ src, onLoad, onError, enabled = true, }: UseImagePreloadOptions): UseImagePreloadReturn { const [state, setState] = useState<ImagePreloadState>(initialState); const abortControllerRef = useRef<AbortController | null>(null); const onLoadRef = useRef(onLoad); const onErrorRef = useRef(onError); // Keep callbacks refs updated onLoadRef.current = onLoad; onErrorRef.current = onError; const preload = useCallback(() => { // Cancel any pending loads if (abortControllerRef.current) { abortControllerRef.current.abort(); } abortControllerRef.current = new AbortController(); const { signal } = abortControllerRef.current; const sources = Array.isArray(src) ? src : [src]; const total = sources.length; if (total === 0) { setState({ isLoading: false, isLoaded: true, hasError: false, progress: 100, loadedCount: 0, totalCount: 0, error: null, }); onLoadRef.current?.(); return; } setState({ isLoading: true, isLoaded: false, hasError: false, progress: 0, loadedCount: 0, totalCount: total, error: null, }); let loadedCount = 0; let errorMessage: string | null = null; const promises = sources.map( (imgSrc) => new Promise<void>((resolve, reject) => { // Check if aborted before starting if (signal.aborted) { reject(new Error('Aborted')); return; } const img = new Image(); // Handle abort signal signal.addEventListener('abort', () => { img.src = ''; reject(new Error('Aborted')); }); img.onload = () => { loadedCount++; setState((prev) => ({ ...prev, loadedCount, progress: (loadedCount / total) * 100, })); resolve(); }; img.onerror = () => { errorMessage = `Failed to load image: ${imgSrc}`; reject(new Error(errorMessage)); }; img.src = imgSrc; }) ); Promise.all(promises) .then(() => { if (signal.aborted) return; setState({ isLoading: false, isLoaded: true, hasError: false, progress: 100, loadedCount: total, totalCount: total, error: null, }); onLoadRef.current?.(); }) .catch((error) => { if (signal.aborted || error.message === 'Aborted') return; setState({ isLoading: false, isLoaded: false, hasError: true, progress: (loadedCount / total) * 100, loadedCount, totalCount: total, error: errorMessage || error.message, }); onErrorRef.current?.(error); }); }, [src]); const reset = useCallback(() => { if (abortControllerRef.current) { abortControllerRef.current.abort(); } setState(initialState); }, []); // Auto-preload when enabled changes or src changes useEffect(() => { if (enabled) { preload(); } return () => { if (abortControllerRef.current) { abortControllerRef.current.abort(); } }; }, [enabled, preload]); return { ...state, preload, reset, }; } /** * Preload a single image and return a promise * Utility function for imperative use */ export function preloadImage(src: string): Promise<HTMLImageElement> { return new Promise((resolve, reject) => { const img = new Image(); img.onload = () => resolve(img); img.onerror = () => reject(new Error(`Failed to load image: ${src}`)); img.src = src; }); } /** * Preload multiple images and return when all are loaded * Utility function for imperative use */ export async function preloadImages( sources: string[], onProgress?: (progress: number) => void ): Promise<HTMLImageElement[]> { let loaded = 0; const total = sources.length; const results = await Promise.all( sources.map((src) => preloadImage(src).then((img) => { loaded++; onProgress?.((loaded / total) * 100); return img; }) ) ); return results; } export default useImagePreload; |