Add proper support for logging from lua

docs/wip-plugins.md

@@ -55,7 +55,30 @@ The official manual for them is available [here](https://www.lua.org/manual/5.4/
 
 ### Chatterino API
 
-All Chatterino functions are exposed in a global table called `c2`. The following functions are available
+All Chatterino functions are exposed in a global table called `c2`. The following members are available:
+
+#### `log(level, args...)`
+
+Writes a message to the Chatterino log. The `level` argument should be a
+`LogLevel` member. All `args` should be convertible to a string with
+`tostring()`.
+
+Example:
+```
+c2.log(c2.LogLevel.Warning, "Hello, this should show up in the Chatterino log by default")
+
+c2.log(c2.LogLevel.Debug, "Hello world")
+-- Equivalent to doing qCDebug(chatterinoLua) << "[pluginDirectory:Plugin Name]" << "Hello, world"; from C++
+```
+
+#### `LogLevel` enum
+
+This table describes log levels available to Lua Plugins. The values behind the names may change, do not count on them. It has the following keys:
+
+- `Debug`
+- `Info`
+- `Warning`
+- `Critical`
 
 #### `register_command(name, handler)`
 
@@ -139,3 +162,7 @@ execfile("./stuff.lua") -- executes Plugins/name/stuff.lua
 execfile("../stuff.lua") -- tries to load Plugins/stuff.lua and errors
 execfile("luac.out") -- tried to load Plugins/name/luac.out and errors because it contains non-utf8 data
 ```
+
+#### `print(Args...)`
+
+The `print` global function is equivalent to calling `c2.log(c2.LogLevel.Debug, Args...)`

src/controllers/plugins/LuaApi.cpp

@@ -15,6 +15,7 @@
 #    include "lualib.h"
 
 #    include <QFileInfo>
+#    include <QLoggingCategory>
 #    include <QTextCodec>
 
 // NOLINTBEGIN(*vararg)
@@ -102,6 +103,63 @@ int c2_system_msg(lua_State *L)
     return 1;
 }
 
+namespace {
+    void logHelper(lua_State *L, Plugin *pl, QDebug stream, int argc)
+    {
+        stream.noquote();
+        stream << "[" + pl->codename + ":" + pl->meta.name + "]";
+        for (int i = 1; i <= argc; i++)
+        {
+            stream << lua::toString(L, i);
+        }
+        lua_pop(L, argc);
+    }
+
+}  // namespace
+
+int c2_log(lua_State *L)
+{
+    auto *pl = getApp()->plugins->getPluginByStatePtr(L);
+    if (pl == nullptr)
+    {
+        luaL_error(L, "print: internal error: no plugin?");
+        return 0;
+    }
+    auto logc = lua_gettop(L) - 1;
+    // this is the expansion of qCDebug() macro
+    auto temp =
+        (QMessageLogger(QT_MESSAGELOG_FILE, QT_MESSAGELOG_LINE,
+                        QT_MESSAGELOG_FUNC, chatterinoLua().categoryName()));
+
+    LogLevel lvl{};
+    if (!lua::pop(L, &lvl, 1))
+    {
+        luaL_error(L, "Invalid log level, use one from c2.LogLevel.");
+        return 0;
+    }
+    QDebug stream{(QString *)nullptr};
+    switch (lvl)
+    {
+        case LogLevel::Debug:
+            stream = temp.debug();
+            break;
+        case LogLevel::Critical:
+            stream = temp.critical();
+            break;
+        case LogLevel::Info:
+            stream = temp.info();
+            break;
+        case LogLevel::Warning:
+            stream = temp.warning();
+            break;
+        default:
+            assert(false && "if this happens magic_enum must have failed us");
+            break;
+    }
+    logHelper(L, pl, stream, logc);
+    return 0;
+}
+
 int g_load(lua_State *L)
 {
     auto countArgs = lua_gettop(L);
@@ -207,6 +265,24 @@ int g_dofile(lua_State *L)
     return lua_gettop(L);
 }
 
+int g_print(lua_State *L)
+{
+    auto *pl = getApp()->plugins->getPluginByStatePtr(L);
+    if (pl == nullptr)
+    {
+        luaL_error(L, "print: internal error: no plugin?");
+        return 0;
+    }
+    auto argc = lua_gettop(L);
+    // this is the expansion of qCDebug() macro
+    auto stream =
+        (QMessageLogger(QT_MESSAGELOG_FILE, QT_MESSAGELOG_LINE,
+                        QT_MESSAGELOG_FUNC, chatterinoLua().categoryName())
+             .debug());
+    logHelper(L, pl, stream, argc);
+    return 0;
+}
+
 }  // namespace chatterino::lua::api
 // NOLINTEND(*vararg)
 #endif

src/controllers/plugins/LuaApi.hpp

@@ -9,11 +9,16 @@ namespace chatterino::lua::api {
 int c2_register_command(lua_State *L);
 int c2_send_msg(lua_State *L);
 int c2_system_msg(lua_State *L);
+int c2_log(lua_State *L);
 
 int g_load(lua_State *L);
 int g_dofile(lua_State *L);
+int g_print(lua_State *L);
 // NOLINTEND(readability-identifier-naming)
 
+// Represents "calls" to qCDebug, qCInfo ...
+enum LogLevel { Debug, Info, Warning, Critical };
+
 }  // namespace chatterino::lua::api
 
 #endif

src/controllers/plugins/PluginController.cpp

@@ -147,15 +147,20 @@ void PluginController::openLibrariesFor(lua_State *L,
         {"system_msg", lua::api::c2_system_msg},
         {"register_command", lua::api::c2_register_command},
         {"send_msg", lua::api::c2_send_msg},
+        {"log", lua::api::c2_log},
         {nullptr, nullptr},
     };
     lua_pushglobaltable(L);
     auto global = lua_gettop(L);
 
-    // count of elements in C2LIB - 1 (to account for terminator)
+    // count of elements in C2LIB + LogLevel
-    lua::pushEmptyTable(L, 3);
+    auto c2libIdx = lua::pushEmptyTable(L, 5);
 
     luaL_setfuncs(L, c2Lib, 0);
+
+    lua::pushEnumTable<lua::api::LogLevel>(L);
+    lua_setfield(L, c2libIdx, "LogLevel");
+
     lua_setfield(L, global, "c2");
 
     // ban functions
@@ -177,6 +182,8 @@ void PluginController::openLibrariesFor(lua_State *L,
 
         // chatterino dofile is way more similar to require() than dofile()
         {"execfile", lua::api::g_dofile},
+
+        {"print", lua::api::g_print},
         {nullptr, nullptr},
     };
     luaL_setfuncs(L, replacementFuncs, 0);