feat: add wechat mini program support (#658)

* feat: add wechat mini program support

Signed-off-by: Steve0x2a <stevesough@gmail.com>

* fix: accept suggestions.

Signed-off-by: Steve0x2a <stevesough@gmail.com>

* fix: error message and code level modification

Signed-off-by: Steve0x2a <stevesough@gmail.com>

* fix: simplify the use process

Signed-off-by: Steve0x2a <stevesough@gmail.com>

idp/wechat_miniprogram.go

@@ -0,0 +1,82 @@
+// Copyright 2022 The Casdoor Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package idp
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+
+	"golang.org/x/oauth2"
+)
+
+type WeChatMiniProgramIdProvider struct {
+	Client *http.Client
+	Config *oauth2.Config
+}
+
+func NewWeChatMiniProgramIdProvider(clientId string, clientSecret string) *WeChatMiniProgramIdProvider {
+	idp := &WeChatMiniProgramIdProvider{}
+
+	config := idp.getConfig(clientId, clientSecret)
+	idp.Config = config
+	idp.Client = &http.Client{}
+	return idp
+}
+
+func (idp *WeChatMiniProgramIdProvider) SetHttpClient(client *http.Client) {
+	idp.Client = client
+}
+
+func (idp *WeChatMiniProgramIdProvider) getConfig(clientId string, clientSecret string) *oauth2.Config {
+	var config = &oauth2.Config{
+		ClientID:     clientId,
+		ClientSecret: clientSecret,
+	}
+
+	return config
+}
+
+type WeChatMiniProgramSessionResponse struct {
+	Openid     string `json:"openid"`
+	SessionKey string `json:"session_key"`
+	Unionid    string `json:"unionid"`
+	Errcode    int    `json:"errcode"`
+	Errmsg     string `json:"errmsg"`
+}
+
+func (idp *WeChatMiniProgramIdProvider) GetSessionByCode(code string) (*WeChatMiniProgramSessionResponse, error) {
+	sessionUri := fmt.Sprintf("https://api.weixin.qq.com/sns/jscode2session?appid=%s&secret=%s&js_code=%s&grant_type=authorization_code", idp.Config.ClientID, idp.Config.ClientSecret, code)
+	sessionResponse, err := idp.Client.Get(sessionUri)
+	if err != nil {
+		return nil, err
+	}
+	defer sessionResponse.Body.Close()
+	data, err := ioutil.ReadAll(sessionResponse.Body)
+	if err != nil {
+		return nil, err
+	}
+	var session WeChatMiniProgramSessionResponse
+	err = json.Unmarshal(data, &session)
+	if err != nil {
+		return nil, err
+	}
+	if session.Errcode != 0 {
+		return nil, fmt.Errorf("err: %s", session.Errmsg)
+	}
+	return &session, nil
+
+}