package buffer

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

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

// TestInterface is a testing interface for byte encoding and decoding.
type TestInterface interface {
	io.WriterTo
	io.ReaderFrom
	encoding.BinaryMarshaler
	encoding.BinaryUnmarshaler
}

// TestInterfaceWriteAndRead 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 writen 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 TestInterfaceWriteAndRead(t *testing.T, input TestInterface) {

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

	data := []byte{}

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

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

	// 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, int(bytesWriten), len(data2), fmt.Errorf("invalid size: %T.WriteTo #bytes writen != %T.MarshalBinary #bytes generates", input, input))

	// 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 buffer != %T.MarshalBinary bytes generates", input, input))

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

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

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

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

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

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