add support for caching

src/cache-save.ts

@@ -0,0 +1,61 @@
+import * as core from '@actions/core';
+import * as cache from '@actions/cache';
+
+import fs from 'fs';
+import {State} from './cache-distributions/cache-distributor';
+
+async function run() {
+  try {
+    const cache = core.getInput('cache');
+    if (cache) {
+      await saveCache();
+    }
+  } catch (error) {
+    const err = error as Error;
+    core.setFailed(err.message);
+  }
+}
+
+async function saveCache() {
+  const cacheDirPaths = JSON.parse(
+    core.getState(State.CACHE_PATHS)
+  ) as string[];
+  core.debug(`paths for caching are ${cacheDirPaths.join(', ')}`);
+  if (!isCacheDirectoryExists(cacheDirPaths)) {
+    throw new Error('Cache directories do not exist');
+  }
+  const primaryKey = core.getState(State.STATE_CACHE_PRIMARY_KEY);
+  const matchedKey = core.getState(State.CACHE_MATCHED_KEY);
+
+  if (!primaryKey) {
+    core.warning('Error retrieving key from state.');
+    return;
+  } else if (matchedKey === primaryKey) {
+    // no change in target directories
+    core.info(
+      `Cache hit occurred on the primary key ${primaryKey}, not saving cache.`
+    );
+    return;
+  }
+  try {
+    await cache.saveCache(cacheDirPaths, primaryKey);
+    core.info(`Cache saved with the key: ${primaryKey}`);
+  } catch (error) {
+    const err = error as Error;
+    if (err.name === cache.ReserveCacheError.name) {
+      core.info(err.message);
+    } else {
+      throw error;
+    }
+  }
+}
+
+function isCacheDirectoryExists(cacheDirectory: string[]) {
+  const result = cacheDirectory.reduce((previousValue, currentValue) => {
+    return previousValue || fs.existsSync(currentValue);
+  }, false);
+
+  return result;
+}
+
+run();