package buffer

import (
	"bytes"
	"encoding"
	"fmt"
	"io"
	"reflect"
	"testing"
	"unsafe"

	"github.com/google/go-cmp/cmp"
	"github.com/stretchr/testify/require"
	"github.com/tuneinsight/lattigo/v6/utils"
)

// binarySerializer is a testing interface for byte encoding and decoding.
type binarySerializer interface {
	BinarySize() int
	io.WriterTo
	io.ReaderFrom
	encoding.BinaryMarshaler
	encoding.BinaryUnmarshaler
}

// RequireSerializerCorrect tests that:
//   - input and output implement TestInterface
//   - input.WriteTo(io.Writer) writes a number of bytes on the writer equal to the number of bytes generated by input.MarshalBinary()
//   - input.WriteTo buffered bytes are equal to the bytes generated by input.MarshalBinary()
//   - output.ReadFrom(io.Reader) reads a number of bytes on the reader equal to the number of bytes written using input.WriteTo(io.Writer)
//   - applies require.Equalf between the original and reconstructed object for
//   - all the above WriteTo, ReadFrom, MarhsalBinary and UnmarshalBinary do not return an error
func RequireSerializerCorrect(t *testing.T, input binarySerializer) {

	// Allocates a new object of the underlying type of input
	output := reflect.New(reflect.TypeOf(input).Elem()).Elem().Addr().Interface().(binarySerializer)

	data := []byte{}

	buf := bytes.NewBuffer(data) // Compliant to io.Writer and io.Reader

	// Check io.Writer
	bytesWritten, err := input.WriteTo(buf)
	require.NoError(t, err)

	require.Equal(t, int(bytesWritten), input.BinarySize(), fmt.Errorf("invalid size: %T.WriteTo #bytes written = %d != %T.BinarySize = %d", input, bytesWritten, input, input.BinarySize()))

	// Checks that #bytes written = len(buffer)
	require.Equal(t, len(buf.Bytes()), int(bytesWritten), fmt.Errorf("invalid size: %T.WriteTo len(buf.Bytes()) = %d != %T.WriteTo #bytes written = %d", input, len(buf.Bytes()), input, bytesWritten))

	// Check encoding.BinaryMarshaler
	data2, err := input.MarshalBinary()
	require.NoError(t, err)

	// Check that #bytes written with io.Writer = #bytes generates by encoding.BinaryMarshaler
	require.Equal(t, len(data2), int(bytesWritten), fmt.Errorf("invalid size: %T.MarshalBinary #bytes generated = %d != %T.WriteTo #bytes written = %d", input, len(data2), input, bytesWritten))

	// Check that bytes written with io.Writer = bytes generates by encoding.BinaryMarshaler
	require.True(t, bytes.Equal(buf.Bytes(), data2), fmt.Errorf("invalid encoding: %T.WriteTo buf.Bytes() != %T.MarshalBinary bytes generated", input, input))

	// Check io.Reader
	bytesRead, err := output.ReadFrom(buf)
	require.NoError(t, err)

	// Check that #bytes read with io.Reader = #bytes written with io.Writer
	require.Equal(t, bytesRead, bytesWritten, fmt.Errorf("invalid encoding: %T.ReadFrom #bytes read = %d != %T.WriteTo #bytes written = %d", input, bytesRead, input, bytesWritten))

	// Deep equal output = input
	require.True(t, cmp.Equal(input, output))

	// Check encoding.BinaryUnmarshaler
	output = reflect.New(reflect.TypeOf(input).Elem()).Elem().Addr().Interface().(binarySerializer)

	require.NoError(t, output.UnmarshalBinary(data2))

	// Deep equal output = input
	require.True(t, cmp.Equal(input, output))
}

// EqualAsUint64 casts &T to an *uint64 and performs a comparison.
// User must ensure that T can be stored in an uint64.
func EqualAsUint64[T any](a, b T) bool {
	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	return *(*uint64)(unsafe.Pointer(&a)) == *(*uint64)(unsafe.Pointer(&b))
}

// EqualAsUint64Slice casts &[]T into *[]uint64 and performs a comparison.
// User must ensure that T can be stored in an uint64.
func EqualAsUint64Slice[T any](a, b []T) bool {

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	aU64 := *(*[]uint64)(unsafe.Pointer(&a))

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	bU64 := *(*[]uint64)(unsafe.Pointer(&b))

	if len(aU64) != len(bU64) {
		return false
	}

	if utils.Alias1D(aU64, bU64) {
		return true
	}

	for i := range aU64 {
		if aU64[i] != bU64[i] {
			return false
		}
	}

	return true
}

// EqualAsUint32Slice casts &[]T into *[]uint32 and performs a comparison.
// User must ensure that T can be stored in an uint32.
func EqualAsUint32Slice[T any](a, b []T) bool {

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	aU32 := *(*[]uint32)(unsafe.Pointer(&a))

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	bU32 := *(*[]uint32)(unsafe.Pointer(&b))

	if len(aU32) != len(bU32) {
		return false
	}

	if utils.Alias1D(aU32, bU32) {
		return true
	}

	for i := range aU32 {
		if aU32[i] != bU32[i] {
			return false
		}
	}

	return true
}

// EqualAsUint16Slice casts &[]T into *[]uint16 and performs a comparison.
// User must ensure that T can be stored in an uint16.
func EqualAsUint16Slice[T any](a, b []T) bool {

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	aU16 := *(*[]uint16)(unsafe.Pointer(&a))

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	bU16 := *(*[]uint16)(unsafe.Pointer(&b))

	if len(aU16) != len(bU16) {
		return false
	}

	if utils.Alias1D(aU16, bU16) {
		return true
	}

	for i := range aU16 {
		if aU16[i] != bU16[i] {
			return false
		}
	}

	return true
}

// EqualAsUint8Slice casts &[]T into *[]uint8 and performs a comparison.
// User must ensure that T can be stored in an uint8.
func EqualAsUint8Slice[T any](a, b []T) bool {

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	aU8 := *(*[]uint8)(unsafe.Pointer(&a))

	/* #nosec G103 -- behavior and consequences well understood, pointer type cast */
	bU8 := *(*[]uint8)(unsafe.Pointer(&b))

	if len(aU8) != len(bU8) {
		return false
	}

	if utils.Alias1D(aU8, bU8) {
		return true
	}

	for i := range aU8 {
		if aU8[i] != bU8[i] {
			return false
		}
	}

	return true
}