feature：implement qiniu upload image

lib/api/qiniu_api.dart

@@ -4,10 +4,11 @@ import 'package:dio/dio.dart';
 import 'package:flutter_picgo/utils/net.dart';
 
 class QiniuApi {
-  static const String BASE_URL = 'http://upload.qiniup.com/';
-
-  static Future upload(FormData data) async {
-    Response res = await NetUtils.getInstance().post(BASE_URL, data: data);
+  /// 上传
+  static Future upload(
+      String area, FormData data, Map<String, dynamic> headers) async {
+    Response res = await NetUtils.getInstance()
+        .post(getHost(area), data: data, options: Options(headers: headers));
     return res.data;
   }
 
@@ -15,15 +16,14 @@ class QiniuApi {
   /// https://developer.qiniu.com/kodo/manual/1208/upload-token
   /// https://pub.flutter-io.cn/packages/crypto
   static String generateUpToken(
-      String accessKey, String secretKey, String putPolicy) {
+      String accessKey, String secretKey, String encodePutPolicy) {
     //对 JSON 编码的上传策略进行URL 安全的 Base64 编码，得到待签名字符串：
-    var encodedPutPolicy = base64Encode(utf8.encode(putPolicy));
     // 使用访问密钥（AK/SK）对上一步生成的待签名字符串计算HMAC-SHA1签名：
     var hmacsha1 = Hmac(sha1, utf8.encode(secretKey));
-    var digest = hmacsha1.convert(utf8.encode(encodedPutPolicy));
+    var digest = hmacsha1.convert(utf8.encode(encodePutPolicy));
     // 对签名进行URL安全的Base64编码：
-    var encodeSign = base64Encode(digest.bytes);
-    return '$accessKey:$encodeSign:$encodedPutPolicy';
+    var encodeSign = urlSafeBase64Encode(digest.bytes);
+    return '$accessKey:$encodeSign:$encodePutPolicy';
   }
 
   /// 生成putPolicy
@@ -31,8 +31,34 @@ class QiniuApi {
   static String generatePutPolicy(String bucket, String key) {
     Map<String, dynamic> map = {
       'scope': '$bucket:$key',
-      'deadline': new DateTime.now().millisecondsSinceEpoch + 3600
+      'deadline': 1909497600 // 2030-07-06
     };
-    return json.encode(map);
+    return urlSafeBase64Encode(utf8.encode(json.encode(map)));
+  }
+
+  /// URL安全的Base64编码
+  /// https://developer.qiniu.com/kodo/manual/1231/appendix#urlsafe-base64
+  static String urlSafeBase64Encode(List<int> bytes) {
+    String str = base64Encode(bytes);
+    return str.replaceAll('+', '-').replaceAll('/', '_');
+  }
+
+  /// Access Area get Host
+  /// https://developer.qiniu.com/kodo/manual/1671/region-endpoint
+  static String getHost(String area) {
+    switch (area) {
+      case 'z0':
+        return 'https://upload.qiniup.com';
+      case 'z1':
+        return 'https://upload-z1.qiniup.com';
+      case 'z2':
+        return 'https://upload-z2.qiniup.com';
+      case 'na0':
+        return 'https://upload-na0.qiniup.com';
+      case 'as0':
+        return 'https://upload-as0.qiniup.com';
+      default:
+        return '';
+    }
   }
 }