#include "lua/lua.hpp"

#include <optional>
#include <string_view>
#include <unordered_map>

#include <sol/sol.hpp>

#include "appfat.h"
#include "engine/assets.hpp"
#include "lua/modules/log.hpp"
#include "lua/modules/render.hpp"
#include "plrmsg.h"
#include "utils/console.h"
#include "utils/log.hpp"

namespace devilution {

namespace {

struct LuaState {
	sol::state sol;
	std::unordered_map<std::string, sol::bytecode> compiledScripts;
};

std::optional<LuaState> CurrentLuaState;

// A Lua function that we use to generate a `require` implementation.
constexpr std::string_view RequireGenSrc = R"(
function requireGen(loaded, loadFn)
  return function(packageName)
      local p = loaded[packageName]
      if p == nil then
          local loader = loadFn(packageName)
          if type(loader) == "string" then
            error(loader)
          end
          p = loader(packageName)
          loaded[packageName] = p
      end
      return p
  end
end
)";

sol::object LuaLoadScriptFromAssets(std::string_view packageName)
{
	LuaState &luaState = *CurrentLuaState;
	std::string path { packageName };
	std::replace(path.begin(), path.end(), '.', '\\');
	path.append(".lua");

	auto iter = luaState.compiledScripts.find(path);
	if (iter != luaState.compiledScripts.end()) {
		return luaState.sol.load(iter->second.as_string_view(), path, sol::load_mode::binary);
	}

	tl::expected<AssetData, std::string> assetData = LoadAsset(path);
	if (!assetData.has_value()) {
		sol::stack::push(luaState.sol.lua_state(), assetData.error());
		return sol::stack_object(luaState.sol.lua_state(), -1);
	}
	sol::load_result result = luaState.sol.load(std::string_view(*assetData), path, sol::load_mode::text);
	if (!result.valid()) {
		sol::stack::push(luaState.sol.lua_state(),
		    StrCat("Lua error when loading ", path, ": ", result.get<std::string>()));
		return sol::stack_object(luaState.sol.lua_state(), -1);
	}
	const sol::function fn = result;
	luaState.compiledScripts[path] = fn.dump();
	return result;
}

int LuaPrint(lua_State *state)
{
	const int n = lua_gettop(state);
	for (int i = 1; i <= n; i++) {
		size_t l;
		const char *s = luaL_tolstring(state, i, &l);
		if (i > 1)
			printInConsole("\t");
		printInConsole(std::string_view(s, l));
		lua_pop(state, 1);
	}
	printNewlineInConsole();
	return 0;
}

bool CheckResult(sol::protected_function_result result, bool optional)
{
	const bool valid = result.valid();
	if (!valid) {
		const std::string error = result.get_type() == sol::type::string
		    ? StrCat("Lua error: ", result.get<std::string>())
		    : "Unknown Lua error";
		if (!optional)
			app_fatal(error);
		LogError(error);
	}
	return valid;
}

void RunScript(std::string_view path, bool optional)
{
	tl::expected<AssetData, std::string> assetData = LoadAsset(path);

	if (!assetData.has_value()) {
		if (!optional)
			app_fatal(assetData.error());
		return;
	}

	CheckResult(CurrentLuaState->sol.safe_script(std::string_view(*assetData)), optional);
}

void LuaPanic(sol::optional<std::string> message)
{
	LogError("Lua is in a panic state and will now abort() the application:\n",
	    message.value_or("unknown error"));
}

} // namespace

void Sol2DebugPrintStack(lua_State *state)
{
	LogDebug("{}", sol::detail::debug::dump_types(state));
}

void Sol2DebugPrintSection(const std::string &message, lua_State *state)
{
	LogDebug("-- {} -- [ {} ]", message, sol::detail::debug::dump_types(state));
}

void LuaInitialize()
{
	CurrentLuaState.emplace(LuaState {
	    .sol = { sol::c_call<decltype(&LuaPanic), &LuaPanic> },
	    .compiledScripts = {},
	});
	sol::state &lua = CurrentLuaState->sol;
	lua.open_libraries(
	    sol::lib::base,
	    sol::lib::package,
	    sol::lib::coroutine,
	    sol::lib::table,
	    sol::lib::string,
	    sol::lib::math,
	    sol::lib::utf8);

#ifdef _DEBUG
	lua.open_libraries(sol::lib::debug);
#endif

	// Registering globals
	lua.set(
	    "print", LuaPrint,
	    "_VERSION", LUA_VERSION);

	// Registering devilutionx object table
	CheckResult(lua.safe_script(RequireGenSrc), /*optional=*/false);
	const sol::table loaded = lua.create_table_with(
	    "devilutionx.log", LuaLogModule(lua),
	    "devilutionx.render", LuaRenderModule(lua),
	    "devilutionx.message", [](std::string_view text) { EventPlrMsg(text, UiFlags::ColorRed); });
	lua["require"] = lua["requireGen"](loaded, LuaLoadScriptFromAssets);

	RunScript("lua\\init.lua", /*optional=*/false);
	RunScript("lua\\user.lua", /*optional=*/true);

	LuaEvent("OnGameBoot");
}

void LuaShutdown()
{
	CurrentLuaState = std::nullopt;
}

void LuaEvent(std::string_view name)
{
	const sol::state &lua = CurrentLuaState->sol;
	const auto trigger = lua.traverse_get<std::optional<sol::object>>("Events", name, "Trigger");
	if (!trigger.has_value() || !trigger->is<sol::protected_function>()) {
		LogError("Events.{}.Trigger is not a function", name);
		return;
	}
	const sol::protected_function fn = trigger->as<sol::protected_function>();
	CheckResult(fn(), /*optional=*/true);
}

sol::state &GetLuaState()
{
	return CurrentLuaState->sol;
}

} // namespace devilution