# LuaJIT Go Wrapper

This is a Go wrapper for LuaJIT that makes it easy to embed Lua in your Go applications. We've focused on making it both performant and developer-friendly, with an API that feels natural to use.

## What's This For?

This wrapper lets you run Lua code from Go and easily pass data back and forth between the two languages. You might want this if you're:
- Adding scripting support to your application
- Building a game engine
- Creating a configuration system
- Writing an embedded rules engine
- Building test automation tools

## Get Started

First, grab the package:
```bash
go get git.sharkk.net/Sky/LuaJIT-to-Go
```

You'll need LuaJIT's development files, but don't worry - we include libraries for Windows and Linux in the vendor directory.

Here's the simplest thing you can do:
```go
L := luajit.New()
defer L.Close()
defer L.Cleanup()

err := L.DoString(`print("Hey from Lua!")`)
```

## Working with Bytecode

Need even more performance? You can compile your Lua code to bytecode and reuse it:

```go
// Compile once
bytecode, err := L.CompileBytecode(`
    local function calculate(x)
        return x * x + x + 1
    end
    return calculate(10)
`, "calc")

// Execute many times
for i := 0; i < 1000; i++ {
    err := L.LoadAndRunBytecode(bytecode, "calc")
}

// Or do both at once
err := L.CompileAndRun(`return "hello"`, "greeting")
```

### When to Use Bytecode

Bytecode execution is consistently faster than direct execution:

```
Benchmark                           Ops/sec         Comparison
----------------------------------------------------------------------------
BenchmarkSimpleDoString             2,561,012        Base
BenchmarkSimplePrecompiledBytecode  3,828,841        +49.5% faster
BenchmarkFunctionCallDoString       2,021,098        Base
BenchmarkFunctionCallPrecompiled    3,482,074        +72.3% faster
BenchmarkLoopDoString                 188,119        Base
BenchmarkLoopPrecompiled              211,081        +12.2% faster
BenchmarkTableOperationsDoString       84,086        Base
BenchmarkTableOperationsPrecompiled    93,655        +11.4% faster
BenchmarkComplexScript                 33,133        Base
BenchmarkComplexScriptPrecompiled      41,044        +23.9% faster
```

Use bytecode when you:
- Have code that runs frequently
- Need maximum performance
- Want to precompile your Lua code
- Are distributing Lua code to many instances

## Registering Go Functions

Want to call Go code from Lua? It's straightforward:
```go
// This function adds two numbers and returns the result
adder := func(s *luajit.State) int {
    sum := s.ToNumber(1) + s.ToNumber(2)
    s.PushNumber(sum)
    return 1  // we're returning one value
}

L.RegisterGoFunction("add", adder)
```

Now in Lua:
```lua
result = add(40, 2)  -- result = 42
```

## Working with Tables

Lua tables are pretty powerful - they're like a mix of Go's maps and slices. We make it easy to work with them:

```go
// Go → Lua
stuff := map[string]interface{}{
    "name": "Arthur Dent",
    "age": 30,
    "items": []float64{1, 2, 3},
}
L.PushTable(stuff)

// Lua → Go
L.GetGlobal("some_table")
result, err := L.ToTable(-1)
```

## Error Handling

We provide useful errors instead of mysterious panics:
```go
if err := L.DoString("this isn't valid Lua!"); err != nil {
    if luaErr, ok := err.(*luajit.LuaError); ok {
        fmt.Printf("Error: %s\n", luaErr.Message)
    }
}
```

## Memory Management

The wrapper uses a custom table pooling system to reduce GC pressure when handling many tables:

```go
// Tables are pooled and reused internally for better performance
for i := 0; i < 1000; i++ {
    L.GetGlobal("table")
    table, _ := L.ToTable(-1)
    // Use table...
    L.Pop(1)
    // Table is automatically returned to pool
}
```

## Best Practices

- Always use `defer L.Close()` and `defer L.Cleanup()` to prevent memory leaks
- Each Lua state should stick to one goroutine
- For concurrent operations, create multiple states
- You can share functions between states safely
- Keep an eye on your stack management - pop as many items as you push
- Use bytecode for frequently executed code paths
- Consider compiling critical Lua code to bytecode at startup

## Advanced Features

### Bytecode Serialization

You can serialize bytecode for distribution or caching:

```go
// Compile once
bytecode, _ := L.CompileBytecode(complexScript, "module")

// Save to file
ioutil.WriteFile("module.luac", bytecode, 0644)

// Later, load from file
bytecode, _ := ioutil.ReadFile("module.luac")
L.LoadAndRunBytecode(bytecode, "module")
```

### Closures and Upvalues

Bytecode properly preserves closures and upvalues:

```go
code := `
    local counter = 0
    return function()
        counter = counter + 1
        return counter
    end
`

bytecode, _ := L.CompileBytecode(code, "counter")
L.LoadAndRunBytecodeWithResults(bytecode, "counter", 1)
L.SetGlobal("increment")

// Later...
L.GetGlobal("increment")
L.Call(0, 1)  // Returns 1
L.Pop(1)

L.GetGlobal("increment")
L.Call(0, 1)  // Returns 2
```

## Need Help?

Check out the tests in the repository - they're full of examples. If you're stuck, open an issue! We're here to help.

## License

MIT Licensed - do whatever you want with it!