first commit

internal/pkg/wechat/wechat.go

@@ -0,0 +1,75 @@
+// Package wechat 封装微信小程序相关调用（此处为 code2session 实现）。
+package wechat
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+
+	"portal-mini-go/internal/pkg/errors"
+)
+
+const code2SessionURL = "https://api.weixin.qq.com/sns/jscode2session"
+
+// SessionInfo 是 code2session 返回的会话信息。
+type SessionInfo struct {
+	OpenID     string
+	UnionID    string
+	SessionKey string
+}
+
+// Client 微信调用客户端。凭证（appid/secret）由调用方按请求传入，
+// 不再依赖静态配置，方便后台动态纳管多个小程序。
+type Client struct {
+	client *http.Client
+}
+
+func NewClient() *Client {
+	return &Client{client: &http.Client{}}
+}
+
+// Code2Session 用 appID + secret + 登录 code 换取 openid / session_key。
+func (c *Client) Code2Session(ctx context.Context, appID, secret, code string) (*SessionInfo, error) {
+	q := url.Values{}
+	q.Set("appid", appID)
+	q.Set("secret", secret)
+	q.Set("js_code", code)
+	q.Set("grant_type", "authorization_code")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, code2SessionURL+"?"+q.Encode(), nil)
+	if err != nil {
+		return nil, errors.Wrap(50000, "build wechat request", err)
+	}
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, errors.Wrap(50000, "call wechat code2session", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, errors.Wrap(50000, "read wechat response", err)
+	}
+
+	var r struct {
+		OpenID     string `json:"openid"`
+		UnionID    string `json:"unionid"`
+		SessionKey string `json:"session_key"`
+		ErrCode    int    `json:"errcode"`
+		ErrMsg     string `json:"errmsg"`
+	}
+	if err := json.Unmarshal(body, &r); err != nil {
+		return nil, errors.Wrap(50000, "decode wechat response", err)
+	}
+	if r.ErrCode != 0 {
+		slog.Warn("wechat code2session error", slog.Int("errcode", r.ErrCode), slog.String("errmsg", r.ErrMsg))
+		return nil, errors.Wrap(50000, fmt.Sprintf("wechat code2session: %s", r.ErrMsg), nil)
+	}
+
+	return &SessionInfo{OpenID: r.OpenID, UnionID: r.UnionID, SessionKey: r.SessionKey}, nil
+}