支付系统核心：配额限制与用户付费状态管理

- 添加 tokio 依赖用于异步测试
- 启用 User 结构体，添加 is_paid/is_admin/paid_expires_at 字段
- 添加 UpdatePaymentRequest 请求体
- insert_weather_data 集成配额检查逻辑
- 新增 get_user_by_id、count_user_weather_data、update_user_payment_status
- 添加 payment_fields 数据库迁移脚本

src/db.rs

@@ -1,28 +1,30 @@
 use sqlx::{PgPool, postgres::PgPoolOptions};
 use std::env;
 use std::error::Error;
+use chrono::Utc;
 
 // 从 models 模块引入 WeatherData 结构体
-use crate::models::{WeatherData, WeatherDataBrief, WeatherListResponse};
+use crate::models::{User, WeatherData, WeatherDataBrief, WeatherListResponse};
 
 // 用于插入weather_data的数据
-pub async fn insert_weather_data(pool: &PgPool, weather_data: &WeatherData) -> Result<i32, String> {
-    // 1. 根据 openid 查询 user_id (这部分逻辑不变)
-    let user_id = match sqlx::query_as::<_, (i32,)>("SELECT id FROM users WHERE openid = $1")
-        .bind(&weather_data.openid)
-        .fetch_optional(pool)
-        .await
-    {
-        Ok(Some((id,))) => id,
-        Ok(None) => {
-            return Err(format!("未找到openid为 {} 的用户", weather_data.openid));
+pub async fn insert_weather_data(pool: &PgPool, weather_data: &WeatherData, user_id: i32) -> Result<i32, String> {
+    // 配额检查：非付费用户数据条数限制
+    let user = get_user_by_id(pool, user_id).await?;
+    let is_paid_active = user.is_paid && (user.paid_expires_at.is_none() || user.paid_expires_at.unwrap() > Utc::now());
+    
+    if !is_paid_active {
+        let current_count = count_user_weather_data(pool, user_id).await?;
+        let limit: i64 = env::var("FREE_USER_DATA_LIMIT")
+            .unwrap_or_else(|_| "20".to_string())
+            .parse()
+            .unwrap_or(20);
+        
+        if current_count >= limit {
+            return Err("数据条数已达上限，请升级为付费用户".to_string());
         }
-        Err(e) => {
-            return Err(format!("查询用户失败: {}", e));
-        }
-    };
+    }
 
-    // 2. 准备插入数据的 SQL 语句 (SQL本身不变)
+    // 准备插入数据的 SQL 语句
     let insert_query = r#"
         INSERT INTO weather_data (
             user_id, title, date, hour, min, longitude, latitude, daysincejanfirst,
@@ -242,3 +244,68 @@ pub async fn delete_weather_data(
         Err(e) => Err(format!("删除天气数据失败: {}", e)),
     }
 }
+
+// 根据用户ID获取用户信息
+pub async fn get_user_by_id(pool: &PgPool, user_id: i32) -> Result<User, String> {
+    let query = r#"
+        SELECT 
+            id, name, openid, phone, type, desc, is_paid, is_admin, paid_expires_at
+        FROM users
+        WHERE id = $1
+    "#;
+
+    let row = match sqlx::query_as::<_, User>(query)
+        .bind(user_id)
+        .fetch_optional(pool)
+        .await
+    {
+        Ok(Some(row)) => row,
+        Ok(None) => return Err(format!("未找到ID为 {} 的用户", user_id)),
+        Err(e) => return Err(format!("查询用户信息失败: {}", e)),
+    };
+
+    Ok(row)
+}
+
+// 统计用户的天气数据条数
+pub async fn count_user_weather_data(pool: &PgPool, user_id: i32) -> Result<i64, String> {
+    let query = r#"
+        SELECT COUNT(*) FROM weather_data WHERE user_id = $1
+    "#;
+
+    let count = match sqlx::query_as::<_, (i64,)>(query)
+        .bind(user_id)
+        .fetch_one(pool)
+        .await
+    {
+        Ok((count,)) => count,
+        Err(e) => return Err(format!("查询天气数据条数失败: {}", e)),
+    };
+
+    Ok(count)
+}
+
+// 更新用户付费状态
+pub async fn update_user_payment_status(
+    pool: &PgPool,
+    user_id: i32,
+    is_paid: bool,
+    paid_expires_at: Option<chrono::DateTime<chrono::Utc>>,
+) -> Result<(), String> {
+    let query = r#"
+        UPDATE users 
+        SET is_paid = $1, paid_expires_at = $2 
+        WHERE id = $3
+    "#;
+
+    match sqlx::query(query)
+        .bind(is_paid)
+        .bind(paid_expires_at)
+        .bind(user_id)
+        .execute(pool)
+        .await
+    {
+        Ok(_) => Ok(()),
+        Err(e) => Err(format!("更新用户付费状态失败: {}", e)),
+    }
+}