From e523415348450207832e76363d83048c6f06ad1e Mon Sep 17 00:00:00 2001
From: sanine-a <sanine.not@pm.me>
Date: Sat, 12 Dec 2020 22:12:36 -0600
Subject: add param table parsing function

---
 src/common.h    | 21 +++++++++++++++++++++
 src/honey_lua.c | 26 ++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/src/common.h b/src/common.h
index cb0ba45..03d6944 100644
--- a/src/common.h
+++ b/src/common.h
@@ -153,6 +153,27 @@ typedef enum {
  */
 int honey_lua_parse_arguments(lua_State* L, unsigned int n, ...);
 
+/** @brief Process a param table.
+ *
+ * Please ensure that the param table is on top of the stack before calling this function.
+ *
+ * The first m elements of the param table are required, and their absence from 
+ * the table will trigger an error.
+ *
+ * The variadic portion of this function expects arguments as 
+ * param_name_1, function1, (void*) data1, param_name_2, function_2, (void*) data_2, ...
+ *
+ * Each function should be of the form void (*)(lua_State*, void*)
+ *
+ * @param[in] L The lua state to parse the table from.
+ * @param[in] n The number of params to parse.
+ * @param[in] m The number of required params.
+ * @param[inout] ... Variadic list of param processing functions, as described above.
+ *
+ * @returns Nothing, but throws a lua error if a required argument is not found.
+ */
+void honey_lua_parse_params(lua_State* L, int n, int m, ...);
+
 /** @brief Wrap C objects for lua. */
 typedef struct honey_lua_element {
     char* name;
diff --git a/src/honey_lua.c b/src/honey_lua.c
index f3ca0a5..ff1d82d 100644
--- a/src/honey_lua.c
+++ b/src/honey_lua.c
@@ -247,6 +247,32 @@ int honey_lua_parse_arguments(lua_State* L, unsigned int n, ...)
     return index;
 }
 
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+void honey_lua_parse_params(lua_State* L, int n, int m, ...)
+{
+    int table_index = lua_gettop(L);
+    
+    va_list args;
+    va_start(args, m);
+
+    for (int i=0; i<n; i++) {
+        const char* param = va_arg(args, const char*);
+        void (*function)(lua_State*, void*) = va_arg(args, void (*)(lua_State*, void*));
+        void* data = va_arg(args, void*);
+        
+        lua_getfield(L, table_index, param);
+        if (lua_isnil(L, -1) && n < m)
+            honey_lua_throw_error
+                (L, "required parameter '%s' was not found in param table!", param);
+
+        function(L, data);
+        lua_pop(L, 1);
+    }
+
+    va_end(args);
+}
+
 /* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *
  * Table creation functions
-- 
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