package tape

import "fmt"
import "slices"
import "errors"
import "testing"
import "math/rand"

const largeNumberNTestRounds = 2048
const randStringBytes        = "-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

func TestI8(test *testing.T) {
	var buffer [16]byte
	_, err := EncodeI8[uint8](buffer[:], 5)
	if err != nil { test.Fatal(err) }
	_, err = EncodeI8[uint8](buffer[:0], 5)
	if err.Error() != "encoding int8: wrong buffer length" { test.Fatal(err) }
	_, _, err = DecodeI8[uint8](buffer[:])
	if err != nil { test.Fatal(err) }
	_, _, err = DecodeI8[uint8](buffer[:0])
	if err.Error() != "decoding int8: wrong buffer length" { test.Fatal(err) }
	
	for number := range uint8(255) {
		n, err := EncodeI8[uint8](buffer[:1], number)
		if err != nil { test.Fatal(err) }
		if correct, got := 1, n; correct != got {
			test.Fatal("not equal:", got)
		}
		decoded, n, err := DecodeI8[uint8](buffer[:1])
		if err != nil { test.Fatal(err) }
		if correct, got := 1, n; correct != got {
			test.Fatal("not equal:", got)
		}
		if decoded != number {
			test.Fatalf("%d != %d", decoded, number)
		}
	}
}

func TestI16(test *testing.T) {
	var buffer [16]byte
	_, err := EncodeI16[uint16](buffer[:], 5)
	if err != nil { test.Fatal(err) }
	_, err = EncodeI16[uint16](buffer[:0], 5)
	if err.Error() != "encoding int16: wrong buffer length" { test.Fatal(err) }
	_, _, err = DecodeI16[uint16](buffer[:])
	if err != nil { test.Fatal(err) }
	_, _, err = DecodeI16[uint16](buffer[:0])
	if err.Error() != "decoding int16: wrong buffer length" { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		number := uint16(rand.Int())
		n, err := EncodeI16[uint16](buffer[:2], number)
		if err != nil { test.Fatal(err) }
		if correct, got := 2, n; correct != got {
			test.Fatal("not equal:", got)
		}
		decoded, n, err := DecodeI16[uint16](buffer[:2])
		if err != nil { test.Fatal(err) }
		if correct, got := 2, n; correct != got {
			test.Fatal("not equal:", got)
		}
		if decoded != number {
			test.Fatalf("%d != %d", decoded, number)
		}
	}
}

func TestI32(test *testing.T) {
	var buffer [16]byte
	_, err := EncodeI32[uint32](buffer[:], 5)
	if err != nil { test.Fatal(err) }
	_, err = EncodeI32[uint32](buffer[:0], 5)
	if err.Error() != "encoding int32: wrong buffer length" { test.Fatal(err) }
	_, _, err = DecodeI32[uint32](buffer[:])
	if err != nil { test.Fatal(err) }
	_, _, err = DecodeI32[uint32](buffer[:0])
	if err.Error() != "decoding int32: wrong buffer length" { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		number := uint32(rand.Int())
		n, err := EncodeI32[uint32](buffer[:4], number)
		if err != nil { test.Fatal(err) }
		if correct, got := 4, n; correct != got {
			test.Fatal("not equal:", got)
		}
		decoded, n, err := DecodeI32[uint32](buffer[:4])
		if err != nil { test.Fatal(err) }
		if correct, got := 4, n; correct != got {
			test.Fatal("not equal:", got)
		}
		if decoded != number {
			test.Fatalf("%d != %d", decoded, number)
		}
	}
}

func TestI64(test *testing.T) {
	var buffer [16]byte
	_, err := EncodeI64[uint64](buffer[:], 5)
	if err != nil { test.Fatal(err) }
	_, err = EncodeI64[uint64](buffer[:0], 5)
	if err.Error() != "encoding int64: wrong buffer length" { test.Fatal(err) }
	_, _, err = DecodeI64[uint64](buffer[:])
	if err != nil { test.Fatal(err) }
	_, _, err = DecodeI64[uint64](buffer[:0])
	if err.Error() != "decoding int64: wrong buffer length" { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		number := uint64(rand.Int())
		n, err := EncodeI64[uint64](buffer[:8], number)
		if err != nil { test.Fatal(err) }
		if correct, got := 8, n; correct != got {
			test.Fatal("not equal:", got)
		}
		decoded, n, err := DecodeI64[uint64](buffer[:8])
		if err != nil { test.Fatal(err) }
		if correct, got := 8, n; correct != got {
			test.Fatal("not equal:", got)
		}
		if decoded != number {
			test.Fatalf("%d != %d", decoded, number)
		}
	}
}

func TestGBEU(test *testing.T) {
	var buffer = [16]byte {
		255, 255, 255, 255,
		255, 255, 255, 255,
		255, 255, 255, 255,
		255, 255, 255, 255,
	}
	_, err := EncodeGBEU[uint64](buffer[:0], 5)
	if err == nil { test.Fatal("no error") }
	if err.Error() != "encoding GBEU: wrong buffer length" { test.Fatal(err) }
	_, err = EncodeGBEU[uint64](buffer[:2], 5555555)
	if err == nil { test.Fatal("no error") }
	if err.Error() != "encoding GBEU: wrong buffer length" { test.Fatal(err) }
	_, _, err = DecodeGBEU[uint64](buffer[:0])
	if err == nil { test.Fatal("no error") }
	if err.Error() != "decoding GBEU: GBEU not terminated" { test.Fatal(err) }

	n, err := EncodeGBEU[uint64](buffer[:], 0x97)
	if err != nil { test.Fatal(err) }
	if correct, got := 2, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := []byte { 0x81, 0x17 }, buffer[:2]; !slices.Equal(correct, got) {
		message := "not equal:"
		for _, item := range got {
			message = fmt.Sprintf("%s %x", message, item)
		}
		test.Fatal(message)
	}
	decoded, n, err := DecodeGBEU[uint64](buffer[:])
	if err != nil { test.Fatal(err) }
	if correct, got := 2, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := uint64(0x97), decoded; correct != got {
		test.Fatalf("not equal: %x", got)
	}

	n, err = EncodeGBEU[uint64](buffer[:], 0x123456)
	if err != nil { test.Fatal(err) }
	if correct, got := 3, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := []byte { 0xc8, 0xe8, 0x56 }, buffer[:3]; !slices.Equal(correct, got) {
		message := "not equal:"
		for _, item := range got {
			message = fmt.Sprintf("%s %x", message, item)
		}
		test.Fatal(message)
	}
	decoded, n, err = DecodeGBEU[uint64](buffer[:])
	if err != nil { test.Fatal(err) }
	if correct, got := 3, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := uint64(0x123456), decoded; correct != got {
		test.Fatalf("not equal: %x", got)
	}

	maxGBEU64 := []byte { 0x81, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F }
	n, err = EncodeGBEU[uint64](buffer[:], 0xFFFFFFFFFFFFFFFF)
	if err != nil { test.Fatal(err) }
	if correct, got := 10, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := maxGBEU64, buffer[:10]; !slices.Equal(correct, got) {
		message := "not equal:"
		for _, item := range got {
			message = fmt.Sprintf("%s %x", message, item)
		}
		test.Fatal(message)
	}
	decoded, n, err = DecodeGBEU[uint64](buffer[:])
	if err != nil { test.Fatal(err) }
	if correct, got := 10, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := uint64(0xFFFFFFFFFFFFFFFF), decoded; correct != got {
		test.Fatalf("not equal: %x", got)
	}

	n, err = EncodeGBEU[uint64](buffer[:], 11)
	if err != nil { test.Fatal(err) }
	if correct, got := 1, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := byte(0xb), buffer[0]; correct != got {
		test.Fatal("not equal:", got)
	}
	decoded, n, err = DecodeGBEU[uint64](buffer[:])
	if err != nil { test.Fatal(err) }
	if correct, got := 1, n; correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := uint64(0xb), decoded; correct != got {
		test.Fatalf("not equal: %x", got)
	}
	
	for _ = range largeNumberNTestRounds {
		buffer = [16]byte { }
		number := uint64(rand.Int())
		_, err := EncodeGBEU[uint64](buffer[:], number)
		if err != nil { test.Fatal(err) }
		decoded, _, err := DecodeGBEU[uint64](buffer[:])
		if err != nil { test.Fatal(err) }
		if decoded != number {
			test.Error("not equal:")
			test.Errorf("%d != %d", decoded, number)
			test.Errorf("%x != %x", decoded, number)
			test.Fatal(buffer)
		}
	}
}

func TestGBEUSize(test *testing.T) {
	if correct, got := 3, GBEUSize(uint(0x100000)); correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := 3, GBEUSize(uint(0x123456)); correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := 4, GBEUSize(uint(0x223456)); correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := 1, GBEUSize(uint(0)); correct != got {
		test.Fatal("not equal:", got)
	}
	if correct, got := 1, GBEUSize(uint(127)); correct != got {
		test.Fatal("not equal:", got)
	}
}

func TestString(test *testing.T) {
	var buffer [16]byte
	_, err := EncodeString[string](buffer[:], "hello")
	if !errIs(err, ErrWrongBufferLength, "encoding string: wrong buffer length") { test.Fatal(err) }
	_, err = EncodeString[string](buffer[:0], "hello")
	if !errIs(err, ErrWrongBufferLength, "encoding string: wrong buffer length") { test.Fatal(err) }
	_, _, err = DecodeString[string](buffer[:])
	if err != nil { test.Fatal(err) }
	_, _, err = DecodeString[string](buffer[:0])
	if err != nil { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		length := rand.Intn(16)
		str := randString(length)
		_, err := EncodeString[string](buffer[:length], str)
		if err != nil { test.Fatal(err) }
		decoded, _, err := DecodeString[string](buffer[:length])
		if err != nil { test.Fatal(err) }
		if decoded != str {
			test.Fatalf("%s != %s", decoded, str)
		}
	}
}

func TestU16CastSafe(test *testing.T) {
	number, ok := U16CastSafe(90_000)
	if ok { test.Fatalf("false positive: %v, %v", number, ok) }
	number, ok = U16CastSafe(-478)
	if ok { test.Fatalf("false positive: %v, %v", number, ok) }
	number, ok = U16CastSafe(3870)
	if !ok { test.Fatalf("false negative: %v, %v", number, ok) }
	if got, correct := number, uint16(3870); got != correct {
		test.Fatalf("not equal: %v %v", got, correct)
	}
	number, ok = U16CastSafe(0)
	if !ok { test.Fatalf("false negative: %v, %v", number, ok) }
	if got, correct := number, uint16(0); got != correct {
		test.Fatalf("not equal: %v %v", got, correct)
	}
}

func randString(length int) string {
	buffer := make([]byte, length)
	for index := range buffer {
		buffer[index] = randStringBytes[rand.Intn(len(randStringBytes))]
	}
	return string(buffer)
}

func randInts[T interface { ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 }] (length int) []T {
	buffer := make([]T, length)
	for index := range buffer {
		buffer[index] = T(rand.Int())
	}
	return buffer
}

func randStrings[T interface { ~string }] (length, maxItemLength int) []T {
	buffer := make([]T, length)
	for index := range buffer {
		buffer[index] = T(randString(rand.Intn(maxItemLength)))
	}
	return buffer
}

func errIs(err error, wraps error, description string) bool {
	return err != nil && (wraps == nil || errors.Is(err, wraps)) && err.Error() == description
}