package buffer

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

	"github.com/google/go-cmp/cmp"
	"github.com/stretchr/testify/require"
)

// 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))
}