package tape

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.Error() != "encoding int8: wrong buffer length" { 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.Error() != "decoding int8: wrong buffer length" { test.Fatal(err) }
	_, err = DecodeI8[uint8](buffer[:0])
	if err.Error() != "decoding int8: wrong buffer length" { test.Fatal(err) }
	
	for number := range uint8(255) {
		err := EncodeI8[uint8](buffer[:1], number)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI8[uint8](buffer[:1])
		if err != nil { test.Fatal(err) }
		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.Error() != "encoding int16: wrong buffer length" { 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.Error() != "decoding int16: wrong buffer length" { 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())
		err := EncodeI16[uint16](buffer[:2], number)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI16[uint16](buffer[:2])
		if err != nil { test.Fatal(err) }
		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.Error() != "encoding int32: wrong buffer length" { 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.Error() != "decoding int32: wrong buffer length" { 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())
		err := EncodeI32[uint32](buffer[:4], number)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI32[uint32](buffer[:4])
		if err != nil { test.Fatal(err) }
		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.Error() != "encoding int64: wrong buffer length" { 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.Error() != "decoding int64: wrong buffer length" { 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())
		err := EncodeI64[uint64](buffer[:8], number)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI64[uint64](buffer[:8])
		if err != nil { test.Fatal(err) }
		if decoded != number {
			test.Fatalf("%d != %d", decoded, number)
		}
	}
}

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 TestI8Array(test *testing.T) {
	var buffer [64]byte
	err := EncodeI8Array[uint8](buffer[:], []uint8 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int8: wrong buffer length") { test.Fatal(err) }
	err = EncodeI8Array[uint8](buffer[:0], []uint8 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int8: wrong buffer length") { test.Fatal(err) }
	_, err = DecodeI8Array[uint8](buffer[:])
	if err != nil { test.Fatal(err) }
	_, err = DecodeI8Array[uint8](buffer[:0])
	if err != nil { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		array := randInts[uint8](rand.Intn(16))
		length, _ := I8ArraySize(array)
		if length != len(array) { test.Fatalf("%d != %d", length, len(array)) }
		err := EncodeI8Array[uint8](buffer[:length], array)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI8Array[uint8](buffer[:length])
		if err != nil { test.Fatal(err) }
		if !slices.Equal(decoded, array) {
			test.Fatalf("%v != %v", decoded, array)
		}
	}
}

func TestI16Array(test *testing.T) {
	var buffer [128]byte
	err := EncodeI16Array[uint16](buffer[:], []uint16 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int16: wrong buffer length") { test.Fatal(err) }
	err = EncodeI16Array[uint16](buffer[:0], []uint16 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int16: wrong buffer length") { test.Fatal(err) }
	_, err = DecodeI16Array[uint16](buffer[:])
	if err != nil { test.Fatal(err) }
	_, err = DecodeI16Array[uint16](buffer[:0])
	if err != nil { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		array := randInts[uint16](rand.Intn(16))
		length, _ := I16ArraySize(array)
		if length != 2 * len(array) { test.Fatalf("%d != %d", length, 2 * len(array)) }
		err := EncodeI16Array[uint16](buffer[:length], array)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI16Array[uint16](buffer[:length])
		if err != nil { test.Fatal(err) }
		if !slices.Equal(decoded, array) {
			test.Fatalf("%v != %v", decoded, array)
		}
	}
}

func TestI32Array(test *testing.T) {
	var buffer [256]byte
	err := EncodeI32Array[uint32](buffer[:], []uint32 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int32: wrong buffer length") { test.Fatal(err) }
	err = EncodeI32Array[uint32](buffer[:0], []uint32 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int32: wrong buffer length") { test.Fatal(err) }
	_, err = DecodeI32Array[uint32](buffer[:])
	if err != nil { test.Fatal(err) }
	_, err = DecodeI32Array[uint32](buffer[:0])
	if err != nil { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		array := randInts[uint32](rand.Intn(16))
		length, _ := I32ArraySize(array)
		if length != 4 * len(array) { test.Fatalf("%d != %d", length, 4 * len(array)) }
		err := EncodeI32Array[uint32](buffer[:length], array)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI32Array[uint32](buffer[:length])
		if err != nil { test.Fatal(err) }
		if !slices.Equal(decoded, array) {
			test.Fatalf("%v != %v", decoded, array)
		}
	}
}

func TestI64Array(test *testing.T) {
	var buffer [512]byte
	err := EncodeI64Array[uint64](buffer[:], []uint64 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int64: wrong buffer length") { test.Fatal(err) }
	err = EncodeI64Array[uint64](buffer[:0], []uint64 { 0, 4, 50, 19 })
	if !errIs(err, ErrWrongBufferLength, "encoding []int64: wrong buffer length") { test.Fatal(err) }
	_, err = DecodeI64Array[uint64](buffer[:])
	if err != nil { test.Fatal(err) }
	_, err = DecodeI64Array[uint64](buffer[:0])
	if err != nil { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		array := randInts[uint64](rand.Intn(16))
		length, _ := I64ArraySize(array)
		if length != 8 * len(array) { test.Fatalf("%d != %d", length, 8 * len(array)) }
		err := EncodeI64Array[uint64](buffer[:length], array)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeI64Array[uint64](buffer[:length])
		if err != nil { test.Fatal(err) }
		if !slices.Equal(decoded, array) {
			test.Fatalf("%v != %v", decoded, array)
		}
	}
}

func TestStringArray(test *testing.T) {
	var buffer [8192]byte
	err := EncodeStringArray[string](buffer[:], []string { "0", "4", "50", "19" })
	if !errIs(err, ErrWrongBufferLength, "encoding []string: wrong buffer length") { test.Fatal(err) }
	err = EncodeStringArray[string](buffer[:0], []string { "0", "4", "50", "19" })
	if !errIs(err, ErrWrongBufferLength, "encoding []string: wrong buffer length") { test.Fatal(err) }
	_, err = DecodeStringArray[string](buffer[:0])
	if err != nil { test.Fatal(err) }
	
	for _ = range largeNumberNTestRounds {
		array := randStrings[string](rand.Intn(16), 16)
		length, _ := StringArraySize(array)
		// TODO test length
		err := EncodeStringArray[string](buffer[:length], array)
		if err != nil { test.Fatal(err) }
		decoded, err := DecodeStringArray[string](buffer[:length])
		if err != nil { test.Fatal(err) }
		if !slices.Equal(decoded, array) {
			test.Fatalf("%v != %v", decoded, array)
		}
	}
}

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
}