add thumbnail generation

src/lib/thumbnails.ts

@@ -0,0 +1,145 @@
+import crypto from 'crypto'
+import fs from 'fs'
+import path from 'path'
+import { spawn } from 'child_process'
+import sharp from 'sharp'
+
+const CACHE_DIR = path.resolve(process.cwd(), '.thumbnails')
+const THUMBNAIL_WIDTH = 400
+const JPEG_QUALITY = 75
+
+/** Ensure the cache directory exists. */
+function ensureCacheDir(): void {
+  if (!fs.existsSync(CACHE_DIR)) {
+    fs.mkdirSync(CACHE_DIR, { recursive: true })
+  }
+}
+
+/** Compute a stable cache filename from libraryId + absolute file path. */
+function cacheKey(libraryId: string, absoluteFilePath: string): string {
+  return crypto
+    .createHash('sha1')
+    .update(libraryId + ':' + absoluteFilePath)
+    .digest('hex')
+}
+
+/** Return the cache path for a given source file, or null if the cache is stale/missing. */
+function getCachedPath(cacheFile: string, sourcePath: string): string | null {
+  try {
+    const cacheStat = fs.statSync(cacheFile)
+    const sourceStat = fs.statSync(sourcePath)
+    if (cacheStat.mtimeMs >= sourceStat.mtimeMs) {
+      return cacheFile
+    }
+  } catch {
+    // Cache miss
+  }
+  return null
+}
+
+/** Generate a thumbnail from an image using sharp. */
+async function generateImageThumbnail(src: string, dest: string): Promise<void> {
+  const tmp = dest + '.tmp'
+  await sharp(src)
+    .resize(THUMBNAIL_WIDTH)
+    .jpeg({ quality: JPEG_QUALITY })
+    .toFile(tmp)
+  fs.renameSync(tmp, dest)
+}
+
+/** Run a child process and collect stderr. Resolves on exit code 0, rejects otherwise. */
+function run(bin: string, args: string[]): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const child = spawn(bin, args, { stdio: ['ignore', 'ignore', 'pipe'] })
+    let stderr = ''
+    child.stderr.on('data', (chunk: Buffer) => { stderr += chunk.toString() })
+    child.on('error', (err) => reject(new Error(`Failed to spawn ${bin}: ${err.message}`)))
+    child.on('close', (code) => {
+      if (code === 0) resolve()
+      else reject(new Error(`${bin} exited with code ${code}: ${stderr.slice(0, 200)}`))
+    })
+  })
+}
+
+/** Get video duration in seconds via ffprobe. */
+async function getVideoDuration(src: string): Promise<number> {
+  return new Promise((resolve, reject) => {
+    const args = [
+      '-v', 'quiet',
+      '-print_format', 'json',
+      '-show_format',
+      src,
+    ]
+    const child = spawn('ffprobe', args, { stdio: ['ignore', 'pipe', 'ignore'] })
+    let stdout = ''
+    child.stdout.on('data', (chunk: Buffer) => { stdout += chunk.toString() })
+    child.on('error', (err) => reject(new Error(`Failed to spawn ffprobe: ${err.message}`)))
+    child.on('close', (code) => {
+      if (code !== 0) return reject(new Error(`ffprobe exited with code ${code}`))
+      try {
+        const json = JSON.parse(stdout) as { format?: { duration?: string } }
+        const duration = parseFloat(json.format?.duration ?? '0')
+        resolve(isNaN(duration) ? 0 : duration)
+      } catch {
+        reject(new Error('Failed to parse ffprobe output'))
+      }
+    })
+  })
+}
+
+/** Generate a thumbnail from a video using ffmpeg. */
+async function generateVideoThumbnail(src: string, dest: string): Promise<void> {
+  const tmp = dest + '.tmp'
+
+  // Seek to 10% of the video duration for a representative frame
+  let offset = 0
+  try {
+    const duration = await getVideoDuration(src)
+    offset = Math.max(0, duration * 0.1)
+  } catch {
+    // If ffprobe fails, fall back to seeking to 0
+  }
+
+  const args = [
+    '-y',                        // overwrite output
+    '-ss', String(offset),       // seek before input (fast)
+    '-i', src,
+    '-frames:v', '1',
+    '-q:v', '5',
+    '-vf', `scale=${THUMBNAIL_WIDTH}:-1`,
+    '-f', 'image2',              // explicit output format (avoids ffmpeg guessing from .tmp extension)
+    tmp,
+  ]
+
+  await run('ffmpeg', args)
+  fs.renameSync(tmp, dest)
+}
+
+/**
+ * Returns the absolute path to a cached thumbnail JPEG for the given file.
+ * Generates it on first call (or when the source has been modified).
+ * Throws on failure — callers should map this to a 404.
+ */
+export async function getThumbnailPath(
+  absoluteFilePath: string,
+  libraryId: string,
+  mediaType: 'image' | 'video'
+): Promise<string> {
+  ensureCacheDir()
+
+  const key = cacheKey(libraryId, absoluteFilePath)
+  const cacheFile = path.join(CACHE_DIR, key + '.jpg')
+
+  // Return from cache if fresh
+  const cached = getCachedPath(cacheFile, absoluteFilePath)
+  if (cached) return cached
+
+  // Generate
+  if (mediaType === 'image') {
+    await generateImageThumbnail(absoluteFilePath, cacheFile)
+  } else {
+    await generateVideoThumbnail(absoluteFilePath, cacheFile)
+  }
+
+  return cacheFile
+}