// Copyright 20011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file contains tests of the GobEncoder/GobDecoder support.

package gob

import (
	"bytes"
	"fmt"
	"os"
	"strings"
	"testing"
)

// Types that implement the GobEncoder/Decoder interfaces.

type ByteStruct struct {
	a byte // not an exported field
}

type StringStruct struct {
	s string // not an exported field
}

type Gobber int

type ValueGobber string // encodes with a value, decodes with a pointer.

// The relevant methods

func (g *ByteStruct) GobEncode() ([]byte, os.Error) {
	b := make([]byte, 3)
	b[0] = g.a
	b[1] = g.a + 1
	b[2] = g.a + 2
	return b, nil
}

func (g *ByteStruct) GobDecode(data []byte) os.Error {
	if g == nil {
		return os.ErrorString("NIL RECEIVER")
	}
	// Expect N sequential-valued bytes.
	if len(data) == 0 {
		return os.EOF
	}
	g.a = data[0]
	for i, c := range data {
		if c != g.a+byte(i) {
			return os.ErrorString("invalid data sequence")
		}
	}
	return nil
}

func (g *StringStruct) GobEncode() ([]byte, os.Error) {
	return []byte(g.s), nil
}

func (g *StringStruct) GobDecode(data []byte) os.Error {
	// Expect N sequential-valued bytes.
	if len(data) == 0 {
		return os.EOF
	}
	a := data[0]
	for i, c := range data {
		if c != a+byte(i) {
			return os.ErrorString("invalid data sequence")
		}
	}
	g.s = string(data)
	return nil
}

func (g *Gobber) GobEncode() ([]byte, os.Error) {
	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
}

func (g *Gobber) GobDecode(data []byte) os.Error {
	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
	return err
}

func (v ValueGobber) GobEncode() ([]byte, os.Error) {
	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
}

func (v *ValueGobber) GobDecode(data []byte) os.Error {
	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
	return err
}

// Structs that include GobEncodable fields.

type GobTest0 struct {
	X int // guarantee we have  something in common with GobTest*
	G *ByteStruct
}

type GobTest1 struct {
	X int // guarantee we have  something in common with GobTest*
	G *StringStruct
}

type GobTest2 struct {
	X int    // guarantee we have  something in common with GobTest*
	G string // not a GobEncoder - should give us errors
}

type GobTest3 struct {
	X int     // guarantee we have  something in common with GobTest*
	G *Gobber // TODO: should be able to satisfy interface without a pointer
}

type GobTest4 struct {
	X int // guarantee we have  something in common with GobTest*
	V ValueGobber
}

type GobTest5 struct {
	X int // guarantee we have  something in common with GobTest*
	V *ValueGobber
}

type GobTestIgnoreEncoder struct {
	X int // guarantee we have  something in common with GobTest*
}

func TestGobEncoderField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTest0)
	err = dec.Decode(x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if x.G.a != 'A' {
		t.Errorf("expected 'A' got %c", x.G.a)
	}
	// Now a field that's not a structure.
	b.Reset()
	gobber := Gobber(23)
	err = enc.Encode(GobTest3{17, &gobber})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	y := new(GobTest3)
	err = dec.Decode(y)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if *y.G != 23 {
		t.Errorf("expected '23 got %d", *y.G)
	}
}

// As long as the fields have the same name and implement the
// interface, we can cross-connect them.  Not sure it's useful
// and may even be bad but it works and it's hard to prevent
// without exposing the contents of the object, which would
// defeat the purpose.
func TestGobEncoderFieldsOfDifferentType(t *testing.T) {
	// first, string in field to byte in field
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTest0)
	err = dec.Decode(x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if x.G.a != 'A' {
		t.Errorf("expected 'A' got %c", x.G.a)
	}
	// now the other direction, byte in field to string in field
	b.Reset()
	err = enc.Encode(GobTest0{17, &ByteStruct{'X'}})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	y := new(GobTest1)
	err = dec.Decode(y)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if y.G.s != "XYZ" {
		t.Fatalf("expected `XYZ` got %c", y.G.s)
	}
}

// Test that we can encode a value and decode into a pointer.
func TestGobEncoderValueEncoder(t *testing.T) {
	// first, string in field to byte in field
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(GobTest4{17, ValueGobber("hello")})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTest5)
	err = dec.Decode(x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if *x.V != "hello" {
		t.Errorf("expected `hello` got %s", x.V)
	}
}

func TestGobEncoderFieldTypeError(t *testing.T) {
	// GobEncoder to non-decoder: error
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := &GobTest2{}
	err = dec.Decode(x)
	if err == nil {
		t.Fatal("expected decode error for mismatched fields (encoder to non-decoder)")
	}
	if strings.Index(err.String(), "type") < 0 {
		t.Fatal("expected type error; got", err)
	}
	// Non-encoder to GobDecoder: error
	b.Reset()
	err = enc.Encode(GobTest2{17, "ABC"})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	y := &GobTest1{}
	err = dec.Decode(y)
	if err == nil {
		t.Fatal("expected decode error for mistmatched fields (non-encoder to decoder)")
	}
	if strings.Index(err.String(), "type") < 0 {
		t.Fatal("expected type error; got", err)
	}
}

// Even though ByteStruct is a struct, it's treated as a singleton at the top level.
func TestGobEncoderStructSingleton(t *testing.T) {
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(&ByteStruct{'A'})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(ByteStruct)
	err = dec.Decode(x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if x.a != 'A' {
		t.Errorf("expected 'A' got %c", x.a)
	}
}

func TestGobEncoderNonStructSingleton(t *testing.T) {
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	g := Gobber(1234) // TODO: shouldn't need to take the address here.
	err := enc.Encode(&g)
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	var x Gobber
	err = dec.Decode(&x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if x != 1234 {
		t.Errorf("expected 1234 got %c", x)
	}
}

func TestGobEncoderIgnoreStructField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestIgnoreEncoder)
	err = dec.Decode(x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if x.X != 17 {
		t.Errorf("expected 17 got %c", x.X)
	}
}

func TestGobEncoderIgnoreNonStructField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	gobber := Gobber(23)
	err := enc.Encode(GobTest3{17, &gobber})
	if err != nil {
		t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestIgnoreEncoder)
	err = dec.Decode(x)
	if err != nil {
		t.Fatal("decode error:", err)
	}
	if x.X != 17 {
		t.Errorf("expected 17 got %c", x.X)
	}
}