package lang

import (
	"strings"
	"testing"
)

func TestResultQuestionPropagatesGoError(t *testing.T) {
	prog, err := Parse(`package demo
import strconv
fun parse(value: String): Result<Int, Error> {
    val parsed = strconv.atoi(value)?
    return Result.Ok(parsed)
}`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{"parsed, gotlinError1 := strconv.Atoi(value)", "if gotlinError1 != nil {", "GotlinResult[int]{Err: gotlinError1}", "GotlinResult[int]{Value: parsed}"} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestGoValueAndErrorReturnConvertsToResult(t *testing.T) {
	prog, err := Parse(`package demo
import strconv
fun parse(value: String): Result<Int, Error> { return strconv.atoi(value) }
fun assign(value: String) { val result: Result<Int, Error> = strconv.atoi(value); println(result.unwrapOr(0)) }`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{
		"value, err := strconv.Atoi(value)",
		"GotlinResult[int]{Value: value, Err: err}",
		"var result GotlinResult[int] = func() GotlinResult[int]",
	} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestGoErrorOnlyReturnConvertsToUnitResult(t *testing.T) {
	prog, err := Parse(`package demo
import os
fun changeDirectory(path: String): Result<Unit, Error> { return os.chdir(path) }`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{
		"func changeDirectory(path string) GotlinResult[struct{}]",
		"err := os.Chdir(path)",
		"GotlinResult[struct{}]{Err: err}",
	} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestResultQuestionPropagatesGotlinResult(t *testing.T) {
	prog, err := Parse(`package demo
import errors
fun inner(ok: Boolean): Result<String, Error> { if (!ok) { return Result.Err(errors.new("failed")) }; return Result.Ok("ok") }
fun outer(): Result<String, Error> { val value = inner(true)?; return Result.Ok(value) }`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{"gotlinResult1 := inner(true)", "gotlinResult1.Err", "value := gotlinResult1.Value"} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestResultUnwrapAndUnwrapOr(t *testing.T) {
	prog, err := Parse(`package demo
fun value(result: Result<String, Error>): String { return result.unwrapOr("fallback") }
fun required(result: Result<String, Error>): String { return result.unwrap() }`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{"gotlinResultUnwrapOr(result, \"fallback\")", "gotlinResultUnwrap(result)"} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestQuestionRequiresResultFunction(t *testing.T) {
	prog, err := Parse(`package demo
import strconv
fun parse(value: String): Int { val parsed = strconv.atoi(value)?; return parsed }`)
	if err != nil {
		t.Fatal(err)
	}
	_, err = GenerateGo(prog)
	if err == nil || !strings.Contains(err.Error(), "returning Result") {
		t.Fatalf("unexpected error: %v", err)
	}
}

func TestQuestionUseKeepsReferencedVariableLive(t *testing.T) {
	prog, err := Parse(`package demo
import strconv
fun parse(value: String): Result<Int, Error> {
    val input = value
    val parsed = strconv.atoi(input)?
    return Result.Ok(parsed)
}`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(string(out), "input := value") || strings.Contains(string(out), "_ = value") {
		t.Fatalf("variable used by ? expression was removed:\n%s", out)
	}
}