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

package gengo

import (
	"five/compiler/parser"
	"strings"
	"testing"
)

func generate(t *testing.T, source string) string {
	t.Helper()
	file, errs := parser.Parse("test.prg", source)
	if len(errs) > 0 {
		for _, e := range errs {
			t.Errorf("parse error: %s", e)
		}
		t.FailNow()
	}
	return Generate(file)
}

func assertContains(t *testing.T, code, want string) {
	t.Helper()
	if !strings.Contains(code, want) {
		t.Errorf("generated code missing %q\n--- code ---\n%s", want, code)
	}
}

func TestGenerateHelloWorld(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   ? "Hello, World!"
   RETURN NIL
`)
	assertContains(t, code, "package main")
	assertContains(t, code, `import (`)
	assertContains(t, code, `"five/hbrt"`)
	assertContains(t, code, "func HB_MAIN(t *hbrt.Thread)")
	assertContains(t, code, "t.Frame(0, 0)")
	assertContains(t, code, "defer t.EndProc()")
	assertContains(t, code, `t.PushString("Hello, World!")`)
	assertContains(t, code, "t.Function(1)")
	assertContains(t, code, "t.PushNil()")
	assertContains(t, code, "t.RetValue()")
	assertContains(t, code, "func main()")
	assertContains(t, code, `vm.Run("MAIN")`)
}

func TestGenerateArithmetic(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   LOCAL n := 10
   RETURN n + 5
`)
	assertContains(t, code, "t.Frame(0, 1)")
	assertContains(t, code, "t.PushInt(10)")
	assertContains(t, code, "t.PopLocal(1)")
	assertContains(t, code, "t.PushLocal(1)") // n
	assertContains(t, code, "t.PushInt(5)")
	assertContains(t, code, "t.Plus()")
	assertContains(t, code, "t.RetValue()")
}

func TestGenerateIfElse(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   LOCAL n := 10
   IF n > 5
      ? "Big"
   ELSE
      ? "Small"
   ENDIF
   RETURN NIL
`)
	assertContains(t, code, "t.Greater()")
	assertContains(t, code, "if t.PopLogical()")
	assertContains(t, code, `t.PushString("Big")`)
	assertContains(t, code, "} else {")
	assertContains(t, code, `t.PushString("Small")`)
}

func TestGenerateDoWhile(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   LOCAL i := 0
   DO WHILE i < 10
      i++
   ENDDO
   RETURN i
`)
	assertContains(t, code, "for {")
	assertContains(t, code, "t.Less()")
	assertContains(t, code, "if !t.PopLogical() { break }")
	assertContains(t, code, "t.LocalAddInt(1, 1)") // i++
}

func TestGenerateForNext(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   LOCAL i, nSum := 0
   FOR i := 1 TO 10
      nSum += i
   NEXT
   RETURN nSum
`)
	assertContains(t, code, "t.Frame(0, 2)")
	assertContains(t, code, "for {")
	assertContains(t, code, "t.LessEqual()")
	assertContains(t, code, "t.LocalAdd(") // nSum += i
	assertContains(t, code, "t.LocalAddInt(") // i += 1
}

func TestGenerateMultipleFunctions(t *testing.T) {
	code := generate(t, `FUNCTION Double(n)
   RETURN n * 2

FUNCTION Main()
   ? Double(21)
   RETURN NIL
`)
	assertContains(t, code, "func HB_DOUBLE(t *hbrt.Thread)")
	assertContains(t, code, "func HB_MAIN(t *hbrt.Thread)")
	assertContains(t, code, "t.Frame(1, 0)") // Double has 1 param
	assertContains(t, code, "t.Mult()")
	assertContains(t, code, `t.PushSymbol(t.VM().FindSymbol("DOUBLE"))`)
}

func TestGenerateStringConcat(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   LOCAL cName := "World"
   ? "Hello, " + cName + "!"
   RETURN NIL
`)
	assertContains(t, code, `t.PushString("Hello, ")`)
	assertContains(t, code, "t.PushLocal(1)")
	assertContains(t, code, "t.Plus()")
	assertContains(t, code, `t.PushString("!")`)
}

func TestGenerateSymbolTable(t *testing.T) {
	code := generate(t, `FUNCTION Main()
   RETURN NIL

FUNCTION Helper()
   RETURN NIL
`)
	assertContains(t, code, `hbrt.Sym("MAIN"`)
	assertContains(t, code, `hbrt.Sym("HELPER"`)
	assertContains(t, code, "hbrt.FsFirst")
}

func TestGenerateImport(t *testing.T) {
	code := generate(t, `IMPORT "net/http"

FUNCTION Main()
   RETURN NIL
`)
	assertContains(t, code, `"net/http"`)
}