// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// FRB (Five Runtime Binary) RTL functions.
//
// PRG Usage:
//   pMod := FrbLoad("module.frb")    // load module
//   FrbDo(pMod, "MYFUNC", args...)   // call function
//   FrbUnload(pMod)                   // unload
//
//   // Or one-shot:
//   result := FrbRun("module.frb", arg1, arg2)

package hbrtl

import (
	"five/hbrt"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// findFiveExe locates the 'five' compiler binary
func findFiveExe() string {
	// 1. Check same directory as running executable
	if exe, err := os.Executable(); err == nil {
		dir := filepath.Dir(exe)
		fiveExe := filepath.Join(dir, "five")
		if _, err := os.Stat(fiveExe); err == nil {
			return fiveExe
		}
	}
	// 2. Check PATH
	if p, err := exec.LookPath("five"); err == nil {
		return p
	}
	// 3. Check current directory
	if _, err := os.Stat("./five"); err == nil {
		abs, _ := filepath.Abs("./five")
		return abs
	}
	return "five" // hope it's in PATH
}

// FRBLOAD(cFileName) → pModule
func FrbLoadFunc(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	filename := t.Local(1).AsString()
	mod, err := hbrt.FrbLoad(t.VM(), filename)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FrbLoad error: %v\n", err)
		t.RetNil()
		return
	}
	t.RetPointer(mod)
}

// FRBDO(pModule, cFuncName [, args...]) → xResult
func FrbDoFunc(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	modVal := t.Local(1)
	funcName := strings.ToUpper(t.Local(2).AsString())

	// Look up function: module-local scope first, then VM global
	var fn func(*hbrt.Thread)
	if modVal.IsPointer() {
		if mod, ok := modVal.AsPointer().(*hbrt.FrbModule); ok {
			fn = mod.FindFunc(funcName)
		}
	}
	if fn == nil {
		sym := t.VM().FindSymbol(funcName)
		if sym != nil {
			fn = sym.Func
		}
	}
	if fn == nil {
		t.RetNil()
		return
	}

	// Push args for the function
	for i := 3; i <= nParams; i++ {
		t.PushValue(t.Local(i))
	}
	t.PendingParams2(nParams - 2)
	fn(t)

	t.PushValue(t.GetRetValue())
	t.RetValue()
}

// FRBUNLOAD(pModule) → NIL
func FrbUnloadFunc(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	v := t.Local(1)
	if !v.IsNil() && v.IsPointer() {
		if mod, ok := v.AsPointer().(*hbrt.FrbModule); ok {
			hbrt.FrbUnload(mod)
		}
	}
	t.RetNil()
}

// FRBCOMPILE(cPrgSource) → pModule
// Compile PRG source string to FRB module in memory.
func FrbCompileFunc(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	source := t.Local(1).AsString()
	fiveExe := findFiveExe()
	mod, err := hbrt.FrbCompileSource(t.VM(), source, fiveExe)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FrbCompile error: %v\n", err)
		t.RetNil()
		return
	}
	t.RetPointer(mod)
}

// FRBEXEC(cPrgSource [, args...]) → xResult
// Compile PRG source, run Main(), unload — all in one call.
func FrbExecFunc(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	source := t.Local(1).AsString()
	fiveExe := findFiveExe()
	mod, err := hbrt.FrbCompileSource(t.VM(), source, fiveExe)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FrbExec error: %v\n", err)
		t.RetNil()
		return
	}
	defer hbrt.FrbUnload(mod)

	// Find and execute MAIN
	sym := t.VM().FindSymbol("MAIN")
	if sym == nil || sym.Func == nil {
		t.RetNil()
		return
	}

	for i := 2; i <= nParams; i++ {
		t.PushValue(t.Local(i))
	}
	t.PendingParams2(nParams - 1)
	sym.Func(t)

	t.PushValue(t.GetRetValue())
	t.RetValue()
}

// FRBRUN(cFileName [, args...]) → xResult
// Load, execute startup function, unload — all in one call.
func FrbRunFunc(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	filename := t.Local(1).AsString()
	mod, err := hbrt.FrbLoad(t.VM(), filename)
	if err != nil {
		t.RetNil()
		return
	}
	defer hbrt.FrbUnload(mod)

	// Find MAIN symbol
	sym := t.VM().FindSymbol("MAIN")
	if sym == nil || sym.Func == nil {
		t.RetNil()
		return
	}

	// Push args
	for i := 2; i <= nParams; i++ {
		t.PushValue(t.Local(i))
	}
	t.PendingParams2(nParams - 1)
	sym.Func(t)

	t.PushValue(t.GetRetValue())
	t.RetValue()
}