增加了getUnlimitWxa接口

src/WechatMp.ts

@@ -5,15 +5,49 @@ export class WechatMpInstance {
     appId: string;
     appSecret: string;
 
+    accessToken?: string;
+    refreshAcessTokenHandler?: any;
+
     constructor(appId: string, appSecret: string) {
         this.appId = appId;
         this.appSecret = appSecret;
+
+        this.refreshAccessToken();
+    }
+
+    private async access(url: string, init?: RequestInit) {
+        const response = await global.fetch(url, init);
+        
+        const { headers, status } = response;
+        if (![200, 201].includes(status)) {
+            throw new Error(`微信服务器返回不正确应答：${status}`);
+        }
+        const contentType = (headers as any)['Content-Type'] || headers.get('Content-Type')!;
+        if (contentType.includes('application/json')) {
+            const json = await response.json();
+            if (typeof json.errcode === 'number' && json.errcode !== 0) {
+                throw new Error(`调用微信接口返回出错，code是${json.errcode}，信息是${json.errmsg}`);
+            }
+            return json;
+        }
+        if (
+            contentType.includes('text')
+            || contentType.includes('xml')
+            || contentType.includes('html')
+        ) {
+            const data = await response.text();
+            return data;
+        }
+        if (contentType.includes('application/octet-stream')) {
+            return await response.arrayBuffer();
+        }
+
+        return response;
     }
 
     async code2Session(code: string) {        
-        const result = await global.fetch(`https://api.weixin.qq.com/sns/jscode2session?appid=${this.appId}&secret=${this.appSecret}&js_code=${code}&grant_type=authorization_code`);
-        const json = await result.json();
-        const { session_key, openid, unionid } = json;
+        const result = await this.access(`https://api.weixin.qq.com/sns/jscode2session?appid=${this.appId}&secret=${this.appSecret}&js_code=${code}&grant_type=authorization_code`);        
+        const { session_key, openid, unionid } = JSON.parse(result);    // 这里微信返回的数据竟然是text/plain
 
         return {
             sessionKey: session_key as string,
@@ -22,6 +56,17 @@ export class WechatMpInstance {
         };
     }
 
+    private async refreshAccessToken() {
+        const result = await this.access(`https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=${this.appId}&secret=${this.appSecret}`);
+        const { access_token, expires_in } = result;
+        this.accessToken = access_token;
+        // 生成下次刷新的定时器
+        this.refreshAcessTokenHandler = setTimeout(() => {
+            this.refreshAccessToken();
+        }, (expires_in - 10) * 1000);
+    }
+
+
     decryptData(sessionKey: string, encryptedData: string, iv: string, signature: string) {
         const skBuf = Buffer.from(sessionKey, 'base64');
         // const edBuf = Buffer.from(encryptedData, 'base64');
@@ -42,4 +87,37 @@ export class WechatMpInstance {
 
         return data;
     }
+
+    async getMpUnlimitWxaCode({ scene, page, envVersion, width, autoColor, lineColor, isHyaline }: {
+        scene: string;
+        page: string;
+        envVersion?: string;
+        width?: number;
+        autoColor?: boolean;
+        lineColor?: {
+            r: number;
+            g: number;
+            b: number;
+        };
+        isHyaline?: true;
+    }) {
+        const result = await this.access(`https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=${this.accessToken}`, {
+            method: 'POST',
+            headers: {
+                'Content-type': "application/json",
+                'Accept': 'image/jpg',
+            },
+            body: JSON.stringify({
+                // access_token: this.accessToken,
+                scene,
+                page,
+                env_version: envVersion,
+                width,
+                auto_color: autoColor,
+                line_color: lineColor,
+                is_hyaline: isHyaline,
+            })
+        });
+        return (await result.arrayBuffer()) as ArrayBuffer;
+    }
 };