Tidy-up caching code

- Extracted common code for Gradle User Home and Project .gradle caches
  into abstract supertype.
- Improve error handling by checking error types

src/cache-project-dot-gradle.ts

@@ -1,94 +1,29 @@
 import path from 'path'
 import fs from 'fs'
-
-import * as core from '@actions/core'
-import * as cache from '@actions/cache'
-import {generateCacheKey} from './cache-utils'
+import {AbstractCache} from './cache-utils'
 
 const PATHS_TO_CACHE = [
     'configuration-cache' // Only configuration-cache is stored at present
 ]
-const CACHE_KEY = 'PROJECT_CACHE_KEY'
-const CACHE_RESULT = 'PROJECT_CACHE_RESULT'
 
-export async function restore(rootDir: string): Promise<void> {
-    if (projectDotGradleDirExists(rootDir)) {
-        core.info(
-            'Project .gradle directory already exists. Not restoring from cache.'
-        )
-        return
+export class ProjectDotGradleCache extends AbstractCache {
+    private rootDir: string
+    constructor(rootDir: string) {
+        super('project', 'Project .gradle directory')
+        this.rootDir = rootDir
     }
 
-    const cacheKey = generateCacheKey('project')
-
-    core.saveState(CACHE_KEY, cacheKey.key)
-
-    const cacheResult = await cache.restoreCache(
-        getCachePath(rootDir),
-        cacheKey.key,
-        cacheKey.restoreKeys
-    )
-
-    if (!cacheResult) {
-        core.info('Project .gradle cache not found. Will start with empty.')
-        return
+    protected cacheOutputExists(): boolean {
+        const dir = this.getProjectDotGradleDir()
+        return fs.existsSync(dir)
     }
 
-    core.info(`Project .gradle dir restored from cache key: ${cacheResult}`)
-    return
-}
-
-export async function save(rootDir: string): Promise<void> {
-    if (!projectDotGradleDirExists(rootDir)) {
-        core.debug('No project .gradle dir to cache.')
-        return
-    }
-
-    const cacheKey = core.getState(CACHE_KEY)
-    const cacheResult = core.getState(CACHE_RESULT)
-
-    if (!cacheKey) {
-        core.info(
-            'Project .gradle dir existed prior to cache restore. Not saving.'
-        )
-        return
-    }
-
-    if (cacheResult && cacheKey === cacheResult) {
-        core.info(
-            `Cache hit occurred on the cache key ${cacheKey}, not saving cache.`
-        )
-        return
-    }
-
-    core.info(`Caching project .gradle dir with cache key: ${cacheKey}`)
-    try {
-        await cache.saveCache(getCachePath(rootDir), cacheKey)
-    } catch (error) {
-        if (error.name === cache.ValidationError.name) {
-            throw error
-        } else if (error.name === cache.ReserveCacheError.name) {
-            core.info(error.message)
-        } else {
-            core.info(`[warning] ${error.message}`)
-        }
-    }
-
-    return
-}
-
-function getCachePath(rootDir: string): string[] {
-    const dir = getProjectDotGradleDir(rootDir)
-    return PATHS_TO_CACHE.map(x => path.resolve(dir, x))
-}
-
-function getProjectDotGradleDir(rootDir: string): string {
-    core.debug(`Resolving .gradle dir in ${rootDir}`)
-    return path.resolve(rootDir, '.gradle')
-}
-
-function projectDotGradleDirExists(rootDir: string): boolean {
-    const dir = getProjectDotGradleDir(rootDir)
-    core.debug(`Checking for existence of project .gradle dir: ${dir}`)
-    return fs.existsSync(dir)
+    protected getCachePath(): string[] {
+        const dir = this.getProjectDotGradleDir()
+        return PATHS_TO_CACHE.map(x => path.resolve(dir, x))
+    }
+
+    private getProjectDotGradleDir(): string {
+        return path.resolve(this.rootDir, '.gradle')
+    }
 }