// Copyright 2019 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.

package iotest

import (
	"bytes"
	"errors"
	"fmt"
	"log"
	"strings"
	"testing"
)

type errWriter struct {
	err error
}

func (w errWriter) Write([]byte) (int, error) {
	return 0, w.err
}

func TestWriteLogger(t *testing.T) {
	olw := log.Writer()
	olf := log.Flags()
	olp := log.Prefix()

	// Revert the original log settings before we exit.
	defer func() {
		log.SetFlags(olf)
		log.SetPrefix(olp)
		log.SetOutput(olw)
	}()

	lOut := new(strings.Builder)
	log.SetPrefix("lw: ")
	log.SetOutput(lOut)
	log.SetFlags(0)

	lw := new(strings.Builder)
	wl := NewWriteLogger("write:", lw)
	if _, err := wl.Write([]byte("Hello, World!")); err != nil {
		t.Fatalf("Unexpectedly failed to write: %v", err)
	}

	if g, w := lw.String(), "Hello, World!"; g != w {
		t.Errorf("WriteLogger mismatch\n\tgot:  %q\n\twant: %q", g, w)
	}
	wantLogWithHex := fmt.Sprintf("lw: write: %x\n", "Hello, World!")
	if g, w := lOut.String(), wantLogWithHex; g != w {
		t.Errorf("WriteLogger mismatch\n\tgot:  %q\n\twant: %q", g, w)
	}
}

func TestWriteLogger_errorOnWrite(t *testing.T) {
	olw := log.Writer()
	olf := log.Flags()
	olp := log.Prefix()

	// Revert the original log settings before we exit.
	defer func() {
		log.SetFlags(olf)
		log.SetPrefix(olp)
		log.SetOutput(olw)
	}()

	lOut := new(strings.Builder)
	log.SetPrefix("lw: ")
	log.SetOutput(lOut)
	log.SetFlags(0)

	lw := errWriter{err: errors.New("Write Error!")}
	wl := NewWriteLogger("write:", lw)
	if _, err := wl.Write([]byte("Hello, World!")); err == nil {
		t.Fatalf("Unexpectedly succeeded to write: %v", err)
	}

	wantLogWithHex := fmt.Sprintf("lw: write: %x: %v\n", "", "Write Error!")
	if g, w := lOut.String(), wantLogWithHex; g != w {
		t.Errorf("WriteLogger mismatch\n\tgot:  %q\n\twant: %q", g, w)
	}
}

func TestReadLogger(t *testing.T) {
	olw := log.Writer()
	olf := log.Flags()
	olp := log.Prefix()

	// Revert the original log settings before we exit.
	defer func() {
		log.SetFlags(olf)
		log.SetPrefix(olp)
		log.SetOutput(olw)
	}()

	lOut := new(strings.Builder)
	log.SetPrefix("lr: ")
	log.SetOutput(lOut)
	log.SetFlags(0)

	data := []byte("Hello, World!")
	p := make([]byte, len(data))
	lr := bytes.NewReader(data)
	rl := NewReadLogger("read:", lr)

	n, err := rl.Read(p)
	if err != nil {
		t.Fatalf("Unexpectedly failed to read: %v", err)
	}

	if g, w := p[:n], data; !bytes.Equal(g, w) {
		t.Errorf("ReadLogger mismatch\n\tgot:  %q\n\twant: %q", g, w)
	}

	wantLogWithHex := fmt.Sprintf("lr: read: %x\n", "Hello, World!")
	if g, w := lOut.String(), wantLogWithHex; g != w {
		t.Errorf("ReadLogger mismatch\n\tgot:  %q\n\twant: %q", g, w)
	}
}

func TestReadLogger_errorOnRead(t *testing.T) {
	olw := log.Writer()
	olf := log.Flags()
	olp := log.Prefix()

	// Revert the original log settings before we exit.
	defer func() {
		log.SetFlags(olf)
		log.SetPrefix(olp)
		log.SetOutput(olw)
	}()

	lOut := new(strings.Builder)
	log.SetPrefix("lr: ")
	log.SetOutput(lOut)
	log.SetFlags(0)

	data := []byte("Hello, World!")
	p := make([]byte, len(data))

	lr := ErrReader(errors.New("io failure"))
	rl := NewReadLogger("read", lr)
	n, err := rl.Read(p)
	if err == nil {
		t.Fatalf("Unexpectedly succeeded to read: %v", err)
	}

	wantLogWithHex := fmt.Sprintf("lr: read %x: io failure\n", p[:n])
	if g, w := lOut.String(), wantLogWithHex; g != w {
		t.Errorf("ReadLogger mismatch\n\tgot:  %q\n\twant: %q", g, w)
	}
}