feat: add cache cleanup functionality

We go through the cache each time the build ends and check if each image has been referenced during the current build.
If it was we keep it, if not this likely means the image is not needed anymore and we evict it

src/index.ts

@@ -1,6 +1,6 @@
 import { createFilter, dataToEsm } from '@rollup/pluginutils'
 import { Plugin, ResolvedConfig } from 'vite'
-import { put as cachePut, tmp } from 'cacache'
+import { put as cachePut, tmp, ls as listCache, rm as removeFromCache } from 'cacache'
 import fs from 'fs/promises'
 import { join, relative } from 'path'
 import findCacheDir from 'find-cache-dir'
@@ -36,6 +36,9 @@ export function imagetools(userOptions: Partial<PluginOptions> = {}): Plugin {
     // wether to actually transform the images, disabled in devmode by default
     let transformImages: boolean
 
+    // this set keeps track of all cacheId we have used during the build
+    let totalImages = new Set()
+
     const filter = createFilter(pluginOptions.include, pluginOptions.exclude)
 
     const directives = [...pluginOptions.customDirectives, ...Object.values(builtinDiretcives)]
@@ -51,7 +54,7 @@ export function imagetools(userOptions: Partial<PluginOptions> = {}): Plugin {
         },
         async load(id) {
             const src = new URL(id, 'file://')
-            
+
             if (!filter(src.href)) return null
 
             // get all parameters from the url query string
@@ -62,7 +65,9 @@ export function imagetools(userOptions: Partial<PluginOptions> = {}): Plugin {
 
 
             const outputMetadatas = await Promise.all(pipelineConfigs.map(async config => {
-                const cacheId = JSON.stringify(config) // each image is addressed by its configuration                
+                const cacheId = JSON.stringify(config) + src.href // each image is addressed by its configuration                
+
+                totalImages.add(cacheId)
 
                 let data: Uint8Array | undefined
                 let metadata: Record<string, any> = {}
@@ -121,9 +126,9 @@ export function imagetools(userOptions: Partial<PluginOptions> = {}): Plugin {
                     const dir = await tmp.mkdir(pluginOptions.cache)
                     const tmpFile = join(dir, `${fileName}.${metadata.format}`)
 
-                    await fs.writeFile(tmpFile, data || '')
+                    await fs.writeFile(tmpFile, data || '')
 
-                    metadata.src = relative(viteConfig.root,tmpFile)
+                    metadata.src = relative(viteConfig.root, tmpFile)
                 }
 
                 return metadata
@@ -169,5 +174,20 @@ export function imagetools(userOptions: Partial<PluginOptions> = {}): Plugin {
                 return null
             }
         },
+        // cleanup the cache on build end
+        async buildEnd() {
+            if (pluginOptions.cache) {
+                const cachedImages = await listCache(pluginOptions.cache)
+
+                // we will delete all images that are in the cache that have not been referenced during the current build.
+                // This means that the image is likely not needed anymore
+                for (const key in cachedImages) {
+                    if (!totalImages.has(key)) {
+                        await removeFromCache(pluginOptions.cache, key)
+                        console.log(`deleted image ${key} from cache`);
+                    }
+                }
+            }
+        }
     }
 }