Additional tools for gardening.

tools/gardening/lib/src/cache_new.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:io';
+import 'logger.dart';
+import 'try.dart';
+
+typedef Future<String> FetchDataFunction();
+typedef Future<String> WithCacheFunction(FetchDataFunction fetchData,
+    [String key]);
+typedef WithCacheFunction CreateCacheFunction(
+    {String overrideKey, Duration duration});
+
+CreateCacheFunction initCache(Uri baseUri, [Logger logger]) {
+  final cache = new Cache(baseUri, logger);
+  logger ??= new StdOutLogger(Level.warning);
+
+  return ({String overrideKey, Duration duration}) {
+    if (duration == null) {
+      duration = new Duration(hours: 24);
+    }
+
+    return (FetchDataFunction call, [String key]) async {
+      if (overrideKey != null) {
+        key = overrideKey;
+      }
+
+      if (key == null || key.isEmpty) {
+        logger.warning("Key is null or empty - cannot cache result");
+      } else {
+        // format key
+        key = key.replaceAll("/", "_").replaceAll(".", "_");
+
+        Try<CacheResult> readResult = await cache.read(key, duration);
+        if (!readResult.isError && readResult.value.hasResult) {
+          logger.debug("Found key $key in cache");
+          return readResult.value.result;
+        }
+        if (readResult.isError) {
+          logger.error("Error when reading from cache", readResult.error,
+              readResult.stackTrace);
+        }
+      }
+
+      logger.debug("Could not find key $key in cache");
+
+      // we have to make a call
+      String result = await call();
+
+      // insert/update the cache
+      if (key != null && !key.isEmpty) {
+        await cache.write(key, result);
+      }
+
+      return result;
+    };
+  };
+}
+
+CreateCacheFunction noCache() {
+  return ({String overrideKey, Duration duration}) {
+    return (FetchDataFunction fetchData, [String key]) {
+      return fetchData();
+    };
+  };
+}
+
+/// Simple cache for caching data.
+class Cache {
+  // TODO(mkroghj) use this instead of cache.dart
+  Uri base;
+  Logger logger;
+
+  Cache(this.base, this.logger);
+
+  Map<String, String> memoryCache = <String, String>{};
+
+  /// Checks if key [path] is in cache
+  Future<bool> containsKey(String path, [Duration duration]) async {
+    if (memoryCache.containsKey(path)) return true;
+
+    File file = new File.fromUri(base.resolve(path));
+    if (await file.exists()) {
+      return duration == null
+          ? true
+          : new DateTime.now().difference(await file.lastModified()) <=
+              duration;
+    }
+
+    return false;
+  }
+
+  /// Try reading [path] from cache
+  Future<Try<CacheResult>> read(String path, [Duration duration]) async {
+    if (memoryCache.containsKey(path)) {
+      logger.debug('Found $path in memory cache');
+      return new Try.from(new CacheResult(memoryCache[path]));
+    }
+
+    File file = new File.fromUri(base.resolve(path));
+
+    if (!(await file.exists())) {
+      logger.debug('Could not find file $path in file cache');
+      return new Try.from(new CacheResult.noResult());
+    }
+
+    if (duration != null &&
+        new DateTime.now().difference(await file.lastModified()) > duration) {
+      logger.debug('File $path was found but the information is too stale,'
+          'for the duration: $duration');
+      return new Try.from(new CacheResult.noResult());
+    }
+
+    return tryStartAsync(() async {
+      logger.debug('Found $path in file cache');
+      var text = await file.readAsString();
+      memoryCache[path] = text;
+      return new CacheResult(text);
+    });
+  }
+
+  /// Store [text] as the cache data for [path].
+  Future write(String path, String text) async {
+    logger.debug('Creating $path in file cache');
+    File file = new File.fromUri(base.resolve(path));
+    if (!await file.exists()) {
+      await file.create(recursive: true);
+    }
+    await file.writeAsString(text);
+    memoryCache[path] = text;
+  }
+
+  /// Clears the cache at [baseUri]
+  Future clearCache(Uri baseUri) async {
+    await new Directory(baseUri.toFilePath()).delete(recursive: true);
+  }
+}
+
+class CacheResult {
+  final bool hasResult;
+  final String result;
+
+  CacheResult.noResult()
+      : hasResult = false,
+        result = null {}
+
+  CacheResult(this.result) : hasResult = true {}
+}