Using LuaJIT library with V to load tables from Lua into structs

runtime.c.v

module luajit

#flag -I/usr/local/include/luajit-2.1
#flag -L/usr/local/lib
#flag -lluajit-5.1
#flag -lm
#include "lua.h"
#include "lauxlib.h"

pub struct C.lua_State {}

fn C.luaL_newstate() &C.lua_State
fn C.lua_getglobal(&C.lua_State, &char)
fn C.lua_istable(&C.lua_State, int) int
fn C.lua_gettable(&C.lua_State, int)
fn C.lua_isnoneornil(&C.lua_State, int) int
fn C.lua_pushstring(&C.lua_State, &char)
fn C.lua_tointeger(&C.lua_State, int) int
fn C.lua_tostring(&C.lua_State, int) &char
fn C.luaL_dostring(&C.lua_State, &char) int
fn C.lua_pop(&C.lua_State, int)
fn C.lua_close(&C.lua_State)

pub fn parse[T](code string) !T {
    mut typ := T{}
    lua_state := C.luaL_newstate()
    defer { C.lua_close(lua_state) }
    C.lua_getglobal(lua_state, c"config")
    if C.lua_istable(lua_state, -1) == 1 {
        return decode_state_into_type[T](T{}, lua_state, -2)
    }
    return typ
}

fn decode_state_into_type[T](_ T, lua_state &C.lua_State, stack_offset int) !T {
    mut typ := T{}
    $if T is $struct {
        $for field in T.fields {
            C.lua_pushstring(lua_state, &char(field.name.str))
            if C.lua_isnoneornil(lua_state, stack_offset) == 0 {
                C.lua_gettable(lua_state, stack_offset)
                $if field.typ is int {
                    typ.$(field.name) = C.lua_tointeger(lua_state, -1)
                    C.lua_pop(lua_state, 1)
                } $else $if field.typ is u8 {
                    typ.$(field.name) = C.lua_tointeger(lua_state, -1)
                    C.lua_pop(lua_state, 1)
                } $else $if field.typ is string {
                    typ.$(field.name) = unsafe { cstring_to_vstring(C.lua_tostring(lua_state, -1)) }
                    C.lua_pop(lua_state, 1)
                } $else $if field.is_struct {
                    if C.lua_istable(lua_state, -1) == 1 {
                        typ.$(field.name) = decode_state_into_type(typ.$(field.name), lua_state, -2)!
                    }
                }
            }
        }
    }
    return typ
}

runtime_test.v

module luajit

import term.ui as tui

struct Test{
	value int
	name  string
	extra int
}

fn test_parse() {
	c := parse[Test]("config = { value = 43384, name = 'thing' }") or { panic(err) }
	assert c == Test{ value: 43384, name: "thing" }
}

struct Config {
	leader_key                string
	relative_line_numbers     int
	insert_tabs_not_spaces    int
	selection_highlight_color tui.Color
}

fn test_parse_config_replacement() {
	config_in_lua := "config = { leader_key = ';', insert_tabs_not_spaces = 1, relative_line_numbers = 1, selection_highlight_color = { r = 22, g = 235, b = 225 } }"
	parsed_config := parse[Config](config_in_lua) or { panic(err) }
	assert parsed_config == Config {
		leader_key: ";", relative_line_numbers: 1, insert_tabs_not_spaces: 1, selection_highlight_color: tui.Color{ r: 22, g: 235, b: 225 }
	}

}