feat(lua): add response header manipulation support for Lua scripts

- Introduce CandyHeaders struct wrapping HeaderMap with Arc<Mutex>
- Implement __index/__newindex metamethods for header access in Lua
- Support both bracket and dot notation (cd.header["Content-Type"], cd.header.content_type)
- Handle multi-value headers via Lua tables (e.g., Set-Cookie)
- Auto-convert underscores to hyphens in header names for Lua-friendly syntax

Author: DefectingCat

src/http/lua.rs

@@ -1,4 +1,4 @@
-use std::str::FromStr;
+use std::sync::{Arc, Mutex};
 
 use anyhow::{Context, anyhow};
 use axum::{
@@ -27,11 +27,116 @@ struct CandyRequest {
     /// Uri 在路由中被添加到上下文中
     uri: Uri,
 }
+
+/// HTTP 响应头包装器，支持 Lua 访问
+#[derive(Clone, Debug)]
+struct CandyHeaders {
+    headers: Arc<Mutex<HeaderMap>>,
+}
+
+impl CandyHeaders {
+    fn new(headers: HeaderMap) -> Self {
+        Self {
+            headers: Arc::new(Mutex::new(headers)),
+        }
+    }
+
+    /// 将 Lua 风格的 header 名转换为 HTTP header 名
+    /// 下划线转换为连字符，如 content_type -> Content-Type
+    fn normalize_header_name(key: &str) -> String {
+        key.replace('_', "-")
+    }
+}
+
+impl UserData for CandyHeaders {
+    fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
+        // __index: 读取 header
+        // 支持 cd.header["Content-Type"] 和 cd.header.content_type
+        methods.add_meta_method("__index", |lua, this, key: String| {
+            let normalized = Self::normalize_header_name(&key);
+            let headers = this.headers.lock().map_err(|e| {
+                mlua::Error::external(anyhow!("Failed to lock headers: {}", e))
+            })?;
+
+            // 查找 header (大小写不敏感)
+            let header_name = HeaderName::try_from(normalized.as_str())
+                .map_err(|e| mlua::Error::external(anyhow!("Invalid header name: {}", e)))?;
+
+            let values: Vec<String> = headers
+                .get_all(&header_name)
+                .iter()
+                .filter_map(|v| v.to_str().ok().map(|s| s.to_string()))
+                .collect();
+
+            if values.is_empty() {
+                Ok(mlua::Value::Nil)
+            } else if values.len() == 1 {
+                Ok(mlua::Value::String(lua.create_string(&values[0])?))
+            } else {
+                // 多值 header 返回 table
+                let table = lua.create_table()?;
+                for (i, v) in values.iter().enumerate() {
+                    table.set(i + 1, v.clone())?;
+                }
+                Ok(mlua::Value::Table(table))
+            }
+        });
+
+        // __newindex: 设置/删除 header
+        // cd.header["Content-Type"] = "text/plain"
+        // cd.header["Set-Cookie"] = {"a=1", "b=2"}
+        // cd.header["X-My-Header"] = nil  -- 删除
+        methods.add_meta_method_mut("__newindex", |_lua, this, (key, value): (String, mlua::Value)| {
+            let normalized = Self::normalize_header_name(&key);
+            let header_name = HeaderName::try_from(normalized.as_str())
+                .map_err(|e| mlua::Error::external(anyhow!("Invalid header name: {}", e)))?;
+
+            let mut headers = this.headers.lock().map_err(|e| {
+                mlua::Error::external(anyhow!("Failed to lock headers: {}", e))
+            })?;
+
+            // 先移除已有的值
+            headers.remove(&header_name);
+
+            match value {
+                mlua::Value::Nil => {
+                    // 删除 header，已经 remove 了，不需要额外操作
+                }
+                mlua::Value::String(s) => {
+                    let val = s.to_str()?;
+                    let header_value = HeaderValue::from_str(&val)
+                        .map_err(|e| mlua::Error::external(anyhow!("Invalid header value: {}", e)))?;
+                    headers.append(header_name.clone(), header_value);
+                }
+                mlua::Value::Table(t) => {
+                    // 多值 header
+                    for pair in t.pairs::<i32, mlua::String>() {
+                        let (_, v) = pair.map_err(|e| {
+                            mlua::Error::external(anyhow!("Invalid header value in table: {}", e))
+                        })?;
+                        let val = v.to_str()?;
+                        let header_value = HeaderValue::from_str(&val)
+                            .map_err(|e| mlua::Error::external(anyhow!("Invalid header value: {}", e)))?;
+                        headers.append(header_name.clone(), header_value);
+                    }
+                }
+                _ => {
+                    return Err(mlua::Error::external(anyhow!(
+                        "Header value must be string, table, or nil"
+                    )));
+                }
+            }
+
+            Ok(())
+        });
+    }
+}
+
 /// 为 Lua 脚本提供 HTTP 响应上下文
 #[derive(Clone, Debug)]
 struct CandyResponse {
     status: u16,
-    headers: HeaderMap,
+    headers: CandyHeaders,
     body: String,
 }
 // HTTP 请求上下文，可在 Lua 中使用
@@ -43,67 +148,72 @@ struct RequestContext {
 
 impl UserData for RequestContext {
     fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
-        // 元方法：实现属性访问 (cd.status)
+        // 元方法：实现属性访问 (cd.status, cd.header)
         // 注意：需要同时处理常量字段和动态属性
-        methods.add_meta_method("__index", |_, this, key: String| {
+        methods.add_meta_method("__index", |lua, this, key: String| {
             match key.as_str() {
                 // 动态属性
-                "status" => Ok(this.res.status),
+                "status" => lua.pack(this.res.status),
+                "header" => {
+                    // 返回 headers 对象
+                    lua.create_userdata(this.res.headers.clone())
+                        .map(mlua::Value::UserData)
+                }
                 // HTTP 方法常量
-                "HTTP_GET" => Ok(0u16),
-                "HTTP_HEAD" => Ok(1u16),
-                "HTTP_PUT" => Ok(2u16),
-                "HTTP_POST" => Ok(3u16),
-                "HTTP_DELETE" => Ok(4u16),
-                "HTTP_OPTIONS" => Ok(5u16),
-                "HTTP_MKCOL" => Ok(6u16),
-                "HTTP_COPY" => Ok(7u16),
-                "HTTP_MOVE" => Ok(8u16),
-                "HTTP_PROPFIND" => Ok(9u16),
-                "HTTP_PROPPATCH" => Ok(10u16),
-                "HTTP_LOCK" => Ok(11u16),
-                "HTTP_UNLOCK" => Ok(12u16),
-                "HTTP_PATCH" => Ok(13u16),
-                "HTTP_TRACE" => Ok(14u16),
+                "HTTP_GET" => lua.pack(0u16),
+                "HTTP_HEAD" => lua.pack(1u16),
+                "HTTP_PUT" => lua.pack(2u16),
+                "HTTP_POST" => lua.pack(3u16),
+                "HTTP_DELETE" => lua.pack(4u16),
+                "HTTP_OPTIONS" => lua.pack(5u16),
+                "HTTP_MKCOL" => lua.pack(6u16),
+                "HTTP_COPY" => lua.pack(7u16),
+                "HTTP_MOVE" => lua.pack(8u16),
+                "HTTP_PROPFIND" => lua.pack(9u16),
+                "HTTP_PROPPATCH" => lua.pack(10u16),
+                "HTTP_LOCK" => lua.pack(11u16),
+                "HTTP_UNLOCK" => lua.pack(12u16),
+                "HTTP_PATCH" => lua.pack(13u16),
+                "HTTP_TRACE" => lua.pack(14u16),
                 // HTTP 状态码常量 - 1xx
-                "HTTP_CONTINUE" => Ok(100u16),
-                "HTTP_SWITCHING_PROTOCOLS" => Ok(101u16),
+                "HTTP_CONTINUE" => lua.pack(100u16),
+                "HTTP_SWITCHING_PROTOCOLS" => lua.pack(101u16),
                 // HTTP 状态码常量 - 2xx
-                "HTTP_OK" => Ok(200u16),
-                "HTTP_CREATED" => Ok(201u16),
-                "HTTP_ACCEPTED" => Ok(202u16),
-                "HTTP_NO_CONTENT" => Ok(204u16),
-                "HTTP_PARTIAL_CONTENT" => Ok(206u16),
+                "HTTP_OK" => lua.pack(200u16),
+                "HTTP_CREATED" => lua.pack(201u16),
+                "HTTP_ACCEPTED" => lua.pack(202u16),
+                "HTTP_NO_CONTENT" => lua.pack(204u16),
+                "HTTP_PARTIAL_CONTENT" => lua.pack(206u16),
                 // HTTP 状态码常量 - 3xx
-                "HTTP_SPECIAL_RESPONSE" => Ok(300u16),
-                "HTTP_MOVED_PERMANENTLY" => Ok(301u16),
-                "HTTP_MOVED_TEMPORARILY" => Ok(302u16),
-                "HTTP_SEE_OTHER" => Ok(303u16),
-                "HTTP_NOT_MODIFIED" => Ok(304u16),
-                "HTTP_TEMPORARY_REDIRECT" => Ok(307u16),
+                "HTTP_SPECIAL_RESPONSE" => lua.pack(300u16),
+                "HTTP_MOVED_PERMANENTLY" => lua.pack(301u16),
+                "HTTP_MOVED_TEMPORARILY" => lua.pack(302u16),
+                "HTTP_SEE_OTHER" => lua.pack(303u16),
+                "HTTP_NOT_MODIFIED" => lua.pack(304u16),
+                "HTTP_TEMPORARY_REDIRECT" => lua.pack(307u16),
                 // HTTP 状态码常量 - 4xx
-                "HTTP_BAD_REQUEST" => Ok(400u16),
-                "HTTP_UNAUTHORIZED" => Ok(401u16),
-                "HTTP_PAYMENT_REQUIRED" => Ok(402u16),
-                "HTTP_FORBIDDEN" => Ok(403u16),
-                "HTTP_NOT_FOUND" => Ok(404u16),
-                "HTTP_NOT_ALLOWED" => Ok(405u16),
-                "HTTP_NOT_ACCEPTABLE" => Ok(406u16),
-                "HTTP_REQUEST_TIMEOUT" => Ok(408u16),
-                "HTTP_CONFLICT" => Ok(409u16),
-                "HTTP_GONE" => Ok(410u16),
-                "HTTP_UPGRADE_REQUIRED" => Ok(426u16),
-                "HTTP_TOO_MANY_REQUESTS" => Ok(429u16),
-                "HTTP_CLOSE" => Ok(444u16),
-                "HTTP_ILLEGAL" => Ok(451u16),
+                "HTTP_BAD_REQUEST" => lua.pack(400u16),
+                "HTTP_UNAUTHORIZED" => lua.pack(401u16),
+                "HTTP_PAYMENT_REQUIRED" => lua.pack(402u16),
+                "HTTP_FORBIDDEN" => lua.pack(403u16),
+                "HTTP_NOT_FOUND" => lua.pack(404u16),
+                "HTTP_NOT_ALLOWED" => lua.pack(405u16),
+                "HTTP_NOT_ACCEPTABLE" => lua.pack(406u16),
+                "HTTP_REQUEST_TIMEOUT" => lua.pack(408u16),
+                "HTTP_CONFLICT" => lua.pack(409u16),
+                "HTTP_GONE" => lua.pack(410u16),
+                "HTTP_UPGRADE_REQUIRED" => lua.pack(426u16),
+                "HTTP_TOO_MANY_REQUESTS" => lua.pack(429u16),
+                "HTTP_CLOSE" => lua.pack(444u16),
+                "HTTP_ILLEGAL" => lua.pack(451u16),
                 // HTTP 状态码常量 - 5xx
-                "HTTP_INTERNAL_SERVER_ERROR" => Ok(500u16),
-                "HTTP_METHOD_NOT_IMPLEMENTED" => Ok(501u16),
-                "HTTP_BAD_GATEWAY" => Ok(502u16),
-                "HTTP_SERVICE_UNAVAILABLE" => Ok(503u16),
-                "HTTP_GATEWAY_TIMEOUT" => Ok(504u16),
-                "HTTP_VERSION_NOT_SUPPORTED" => Ok(505u16),
-                "HTTP_INSUFFICIENT_STORAGE" => Ok(507u16),
+                "HTTP_INTERNAL_SERVER_ERROR" => lua.pack(500u16),
+                "HTTP_METHOD_NOT_IMPLEMENTED" => lua.pack(501u16),
+                "HTTP_BAD_GATEWAY" => lua.pack(502u16),
+                "HTTP_SERVICE_UNAVAILABLE" => lua.pack(503u16),
+                "HTTP_GATEWAY_TIMEOUT" => lua.pack(504u16),
+                "HTTP_VERSION_NOT_SUPPORTED" => lua.pack(505u16),
+                "HTTP_INSUFFICIENT_STORAGE" => lua.pack(507u16),
                 _ => Err(mlua::Error::external(anyhow!(
                     "attempt to index unknown field: {}",
                     key
@@ -194,7 +304,7 @@ pub async fn lua(
                 },
                 res: CandyResponse {
                     status: 200,
-                    headers: HeaderMap::new(),
+                    headers: CandyHeaders::new(HeaderMap::new()),
                     body: "".to_string(),
                 },
             },
@@ -217,6 +327,15 @@ pub async fn lua(
     let mut response = Response::builder();
     let body = Body::from(res.body);
     response = response.status(res.status);
+
+    // 添加响应头
+    let headers = response.headers_mut().unwrap();
+    if let Ok(guard) = res.headers.headers.lock() {
+        for (name, value) in guard.iter() {
+            headers.append(name.clone(), value.clone());
+        }
+    }
+
     let response = response
         .body(body)
         .with_context(|| "Failed to build HTTP response with lua")?;