Extract cache key generation into common function

src/cache-utils.ts

@@ -1,8 +1,5 @@
 import * as core from '@actions/core'
-
-export function truncateArgs(args: string): string {
-    return args.trim().replace(/\s+/g, ' ').substr(0, 400)
-}
+import * as github from '@actions/github'
 
 export function isCacheReadEnabled(cacheName: string): boolean {
     const configValue = getCacheEnabledValue(cacheName)
@@ -26,3 +23,29 @@ function getCacheEnabledValue(cacheName: string): string {
         `Invalid cache-enabled parameter '${configValue}'. Valid values are ['true', 'false', 'read-only']`
     )
 }
+
+export function generateCacheKey(cacheName: string): CacheKey {
+    const cacheKeySeed = process.env[`CACHE_KEY_SEED`] || ''
+    const runnerOs = process.env[`RUNNER_OS`] || ''
+    const cacheKeyPrefix = `${cacheKeySeed}${runnerOs}|${cacheName}|`
+
+    const args = truncateArgs(core.getInput('arguments'))
+    const cacheKeyWithArgs = `${cacheKeyPrefix}${args}|`
+
+    const cacheKey = `${cacheKeyWithArgs}${github.context.sha}`
+    return new CacheKey(cacheKey, [cacheKeyWithArgs, cacheKeyPrefix])
+}
+
+function truncateArgs(args: string): string {
+    return args.trim().replace(/\s+/g, ' ').substr(0, 400)
+}
+
+export class CacheKey {
+    key: string
+    restoreKeys: string[]
+
+    constructor(key: string, restoreKeys: string[]) {
+        this.key = key
+        this.restoreKeys = restoreKeys
+    }
+}