feature：add upyun image strategy and api

Author: hackycy

lib/api/upyun_api.dart

@@ -0,0 +1,38 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:crypto/crypto.dart';
+import 'package:dio/dio.dart';
+
+class UpyunApi {
+  static const BASE_URL = 'http://v0.api.upyun.com';
+
+  static const String operatorKey = 'operatorKey';
+  static const String passwordKey = 'passwordKey';
+}
+
+class UpyunInterceptor extends InterceptorsWrapper {
+
+  @override
+  Future onRequest(RequestOptions options) async {
+    if (options.path.contains(UpyunApi.BASE_URL)) {
+      /// 请求方式，如：GET、POST、PUT、HEAD 等
+      String method = options.method.toLowerCase();
+      String path = options.uri.path;
+      String date = HttpDate.format(DateTime.now());
+      String pwdMd5 = '${md5.convert(options.extra[UpyunApi.passwordKey])}';
+      String operator = options.extra[UpyunApi.operatorKey];
+
+      /// 签名构造
+      var hmacsha1 = Hmac(sha1, utf8.encode(pwdMd5));
+      var auth = hmacsha1.convert(utf8.encode('$method&$path&$date')); 
+      String realAuth = base64.encode(auth.bytes);
+      /// Add Common Header
+      options.headers.addAll({
+        'Date': date,
+        'Authorization': 'UPYUN $operator:$realAuth',
+      });
+    }
+    return options;
+  }
+}

lib/utils/strategy/impl/upyun_image_upload.dart

@@ -0,0 +1,19 @@
+import 'package:flutter_picgo/model/uploaded.dart';
+import 'dart:io';
+
+import 'package:flutter_picgo/utils/strategy/image_upload_strategy.dart';
+
+class UpyunImageUpload implements ImageUploadStrategy {
+  @override
+  Future<Uploaded> delete(Uploaded uploaded) {
+      // TODO: implement delete
+      throw UnimplementedError();
+    }
+
+  @override
+  Future<Uploaded> upload(File file, String renameImage) {
+    // TODO: implement upload
+    throw UnimplementedError();
+  }
+
+}

lib/utils/strategy/upload_strategy_factory.dart

@@ -8,6 +8,7 @@ import 'package:flutter_picgo/utils/strategy/impl/niupic_image_upload.dart';
 import 'package:flutter_picgo/utils/strategy/impl/qiniu_image_upload.dart';
 import 'package:flutter_picgo/utils/strategy/impl/smms_image_upload.dart';
 import 'package:flutter_picgo/utils/strategy/impl/tcyun_image_upload.dart';
+import 'package:flutter_picgo/utils/strategy/impl/upyun_image_upload.dart';
 import 'package:flutter_picgo/utils/strings.dart';
 
 class UploadStrategyFactory {
@@ -43,6 +44,9 @@ class UploadStrategyFactory {
       } else if (type == PBTypeKeys.lsky) {
         /// 兰空
         cache[type] = new LskyImageUpload();
+      } else if (type == PBTypeKeys.upyun) {
+        /// 又拍云
+        cache[type] = new UpyunImageUpload();
       }
     }
     return cache[type];