package lang

import (
	"strings"
	"testing"
)

func TestGenerateRustStyleEnumAndExhaustiveMatch(t *testing.T) {
	prog, err := Parse(`
package demo
enum PaymentResult { Accepted(String), Rejected(String), Pending }
fun describe(result: PaymentResult): String {
    var description = ""
    match (result) {
        PaymentResult::Accepted(id) -> { description = id }
        PaymentResult::Rejected(reason) -> { description = reason }
        PaymentResult::Pending -> { description = "pending" }
    }
    return description
}
fun main() { println(describe(PaymentResult::Accepted("p1"))) }
`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{"type PaymentResult interface", "type PaymentResultAccepted struct", "&PaymentResultAccepted{Value0: \"p1\"}", "case *PaymentResultRejected:", "reason := gotlinMatch1.Value0"} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestRejectNonExhaustiveEnumMatch(t *testing.T) {
	prog, err := Parse(`package demo
enum Result { Ok, Error(String) }
fun use(result: Result) { match (result) { Result::Ok -> { println("ok") } } }`)
	if err != nil {
		t.Fatal(err)
	}
	_, err = GenerateGo(prog)
	if err == nil || !strings.Contains(err.Error(), "missing Error") {
		t.Fatalf("expected exhaustive-match error, got %v", err)
	}
}

func TestRejectWrongVariantPayloadCount(t *testing.T) {
	prog, err := Parse(`package demo
enum Outcome { Ok(String) }
fun main() { val result = Outcome::Ok() }`)
	if err != nil {
		t.Fatal(err)
	}
	_, err = GenerateGo(prog)
	if err == nil || !strings.Contains(err.Error(), "expects 1 values") {
		t.Fatalf("expected payload error, got %v", err)
	}
}

func TestPayloadlessEnumUsesExactVariantStrings(t *testing.T) {
	prog, err := Parse(`package demo
enum Status { PendingReservation, Initiated }
fun main() { println(Status::PendingReservation) }`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{`type Status string`, `StatusPendingReservation`, `"PendingReservation"`, `StatusInitiated`, `"Initiated"`} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestGenerateExhaustiveMatchExpression(t *testing.T) {
	prog, err := Parse(`package demo
enum AccountType { BASIC, SAVINGS }
fun interestRate(accountType: AccountType): Double {
    return match (accountType) {
        AccountType::BASIC -> 0.0
        AccountType::SAVINGS -> 0.02
    }
}`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{"func() float64", "case AccountTypeBASIC:", "return 0.0", "case AccountTypeSAVINGS:", "return 0.02", `panic("unreachable exhaustive match")`} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestGeneratePayloadMatchExpression(t *testing.T) {
	prog, err := Parse(`package demo
enum Outcome { Success(String), Failure(String) }
fun message(outcome: Outcome): String {
    return match (outcome) {
        Outcome::Success(value) -> value
        Outcome::Failure(reason) -> reason
    }
}`)
	if err != nil {
		t.Fatal(err)
	}
	out, err := GenerateGo(prog)
	if err != nil {
		t.Fatal(err)
	}
	for _, want := range []string{"switch gotlinMatch", "value := gotlinMatch", "return value", "return reason"} {
		if !strings.Contains(string(out), want) {
			t.Fatalf("missing %q:\n%s", want, out)
		}
	}
}

func TestRejectInvalidMatchExpression(t *testing.T) {
	for _, test := range []struct {
		source string
		want   string
	}{
		{`package demo enum State { On, Off } fun value(state: State): Int { return match (state) { State::On -> 1 } }`, "missing Off"},
		{`package demo enum State { On, Off } fun value(state: State): Int { return match (state) { State::On -> 1 State::Off -> "off" } }`, "has type String, expected Int"},
	} {
		prog, err := Parse(test.source)
		if err != nil {
			t.Fatal(err)
		}
		_, err = GenerateGo(prog)
		if err == nil || !strings.Contains(err.Error(), test.want) {
			t.Fatalf("expected %q, got %v", test.want, err)
		}
	}
}