package s3manager_test

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"net/http"
	"reflect"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/request"
	"github.com/aws/aws-sdk-go/awstesting"
	"github.com/aws/aws-sdk-go/awstesting/unit"
	"github.com/aws/aws-sdk-go/internal/sdkio"
	"github.com/aws/aws-sdk-go/internal/sdkrand"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/aws/aws-sdk-go/service/s3/s3manager"
)

func dlLoggingSvc(data []byte) (*s3.S3, *[]string, *[]string) {
	var m sync.Mutex
	names := []string{}
	ranges := []string{}

	svc := s3.New(unit.Session)
	svc.Handlers.Send.Clear()
	svc.Handlers.Send.PushBack(func(r *request.Request) {
		m.Lock()
		defer m.Unlock()

		names = append(names, r.Operation.Name)
		ranges = append(ranges, *r.Params.(*s3.GetObjectInput).Range)

		rerng := regexp.MustCompile(`bytes=(\d+)-(\d+)`)
		rng := rerng.FindStringSubmatch(r.HTTPRequest.Header.Get("Range"))
		start, _ := strconv.ParseInt(rng[1], 10, 64)
		fin, _ := strconv.ParseInt(rng[2], 10, 64)
		fin++

		if fin > int64(len(data)) {
			fin = int64(len(data))
		}

		bodyBytes := data[start:fin]
		r.HTTPResponse = &http.Response{
			StatusCode: 200,
			Body:       ioutil.NopCloser(bytes.NewReader(bodyBytes)),
			Header:     http.Header{},
		}
		r.HTTPResponse.Header.Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d",
			start, fin-1, len(data)))
		r.HTTPResponse.Header.Set("Content-Length", fmt.Sprintf("%d", len(bodyBytes)))
	})

	return svc, &names, &ranges
}

func dlLoggingSvcNoChunk(data []byte) (*s3.S3, *[]string) {
	var m sync.Mutex
	names := []string{}

	svc := s3.New(unit.Session)
	svc.Handlers.Send.Clear()
	svc.Handlers.Send.PushBack(func(r *request.Request) {
		m.Lock()
		defer m.Unlock()

		names = append(names, r.Operation.Name)

		r.HTTPResponse = &http.Response{
			StatusCode: 200,
			Body:       ioutil.NopCloser(bytes.NewReader(data[:])),
			Header:     http.Header{},
		}
		r.HTTPResponse.Header.Set("Content-Length", fmt.Sprintf("%d", len(data)))
	})

	return svc, &names
}

func dlLoggingSvcNoContentRangeLength(data []byte, states []int) (*s3.S3, *[]string) {
	var m sync.Mutex
	names := []string{}
	var index int

	svc := s3.New(unit.Session)
	svc.Handlers.Send.Clear()
	svc.Handlers.Send.PushBack(func(r *request.Request) {
		m.Lock()
		defer m.Unlock()

		names = append(names, r.Operation.Name)

		var body io.Reader
		if states[index] < 400 {
			body = bytes.NewReader(data[:])
		} else {
			var buffer bytes.Buffer
			encoder := xml.NewEncoder(&buffer)
			_ = encoder.Encode(&mockErrorResponse)
			body = &buffer
		}

		r.HTTPResponse = &http.Response{
			StatusCode: states[index],
			Body:       ioutil.NopCloser(body),
			Header:     http.Header{},
		}
		index++
	})

	return svc, &names
}

func dlLoggingSvcContentRangeTotalAny(data []byte, states []int) (*s3.S3, *[]string) {
	var m sync.Mutex
	names := []string{}
	ranges := []string{}
	var index int

	svc := s3.New(unit.Session)
	svc.Handlers.Send.Clear()
	svc.Handlers.Send.PushBack(func(r *request.Request) {
		m.Lock()
		defer m.Unlock()

		names = append(names, r.Operation.Name)
		ranges = append(ranges, *r.Params.(*s3.GetObjectInput).Range)

		rerng := regexp.MustCompile(`bytes=(\d+)-(\d+)`)
		rng := rerng.FindStringSubmatch(r.HTTPRequest.Header.Get("Range"))
		start, _ := strconv.ParseInt(rng[1], 10, 64)
		fin, _ := strconv.ParseInt(rng[2], 10, 64)
		fin++

		if fin >= int64(len(data)) {
			fin = int64(len(data))
		}

		// Setting start and finish to 0 because this state of 1 is suppose to
		// be an error state of 416
		if index == len(states)-1 {
			start = 0
			fin = 0
		}

		bodyBytes := data[start:fin]

		r.HTTPResponse = &http.Response{
			StatusCode: states[index],
			Body:       ioutil.NopCloser(bytes.NewReader(bodyBytes)),
			Header:     http.Header{},
		}
		r.HTTPResponse.Header.Set("Content-Range", fmt.Sprintf("bytes %d-%d/*",
			start, fin-1))
		index++
	})

	return svc, &names
}

func dlLoggingSvcWithErrReader(cases []testErrReader) (*s3.S3, *[]string) {
	var m sync.Mutex
	names := []string{}
	var index int

	svc := s3.New(unit.Session, &aws.Config{
		MaxRetries: aws.Int(len(cases) - 1),
	})
	svc.Handlers.Send.Clear()
	svc.Handlers.Send.PushBack(func(r *request.Request) {
		m.Lock()
		defer m.Unlock()

		names = append(names, r.Operation.Name)

		c := cases[index]

		r.HTTPResponse = &http.Response{
			StatusCode: http.StatusOK,
			Body:       ioutil.NopCloser(&c),
			Header:     http.Header{},
		}
		r.HTTPResponse.Header.Set("Content-Range",
			fmt.Sprintf("bytes %d-%d/%d", 0, c.Len-1, c.Len))
		r.HTTPResponse.Header.Set("Content-Length", fmt.Sprintf("%d", c.Len))
		index++
	})

	return svc, &names
}

func TestDownloadOrder(t *testing.T) {
	s, names, ranges := dlLoggingSvc(buf12MB)

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})

	w := aws.NewWriteAtBuffer(make([]byte, len(buf12MB)))
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(len(buf12MB)), n; e != a {
		t.Errorf("expect %d buffer length, got %d", e, a)
	}

	expectCalls := []string{"GetObject", "GetObject", "GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}

	expectRngs := []string{"bytes=0-5242879", "bytes=5242880-10485759", "bytes=10485760-15728639"}
	if e, a := expectRngs, *ranges; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v ranges, got %v", e, a)
	}
}

func TestDownloadZero(t *testing.T) {
	s, names, ranges := dlLoggingSvc([]byte{})

	d := s3manager.NewDownloaderWithClient(s)
	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if n != 0 {
		t.Errorf("expect 0 bytes read, got %d", n)
	}
	expectCalls := []string{"GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}

	expectRngs := []string{"bytes=0-5242879"}
	if e, a := expectRngs, *ranges; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v ranges, got %v", e, a)
	}
}

func TestDownloadSetPartSize(t *testing.T) {
	s, names, ranges := dlLoggingSvc([]byte{1, 2, 3})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
		d.PartSize = 1
	})
	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(3), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject", "GetObject", "GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}
	expectRngs := []string{"bytes=0-0", "bytes=1-1", "bytes=2-2"}
	if e, a := expectRngs, *ranges; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v ranges, got %v", e, a)
	}
	expectBytes := []byte{1, 2, 3}
	if e, a := expectBytes, w.Bytes(); !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v bytes, got %v", e, a)
	}
}

func TestDownloadError(t *testing.T) {
	s, names, _ := dlLoggingSvc([]byte{1, 2, 3})

	num := 0
	s.Handlers.Send.PushBack(func(r *request.Request) {
		num++
		if num > 1 {
			r.HTTPResponse.StatusCode = 400
			r.HTTPResponse.Body = ioutil.NopCloser(bytes.NewReader([]byte{}))
		}
	})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
		d.PartSize = 1
	})
	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err == nil {
		t.Fatalf("expect error, got none")
	}
	aerr := err.(awserr.Error)
	if e, a := "BadRequest", aerr.Code(); e != a {
		t.Errorf("expect %s error code, got %s", e, a)
	}
	if e, a := int64(1), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject", "GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}
	expectBytes := []byte{1}
	if e, a := expectBytes, w.Bytes(); !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v bytes, got %v", e, a)
	}
}

func TestDownloadNonChunk(t *testing.T) {
	s, names := dlLoggingSvcNoChunk(buf2MB)

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})
	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(len(buf2MB)), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}

	count := 0
	for _, b := range w.Bytes() {
		count += int(b)
	}
	if count != 0 {
		t.Errorf("expect 0 count, got %d", count)
	}
}

func TestDownloadNoContentRangeLength(t *testing.T) {
	s, names := dlLoggingSvcNoContentRangeLength(buf2MB, []int{200, 416})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})
	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(len(buf2MB)), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject", "GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}

	count := 0
	for _, b := range w.Bytes() {
		count += int(b)
	}
	if count != 0 {
		t.Errorf("expect 0 count, got %d", count)
	}
}

func TestDownloadContentRangeTotalAny(t *testing.T) {
	s, names := dlLoggingSvcContentRangeTotalAny(buf2MB, []int{200, 416})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})
	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(len(buf2MB)), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject", "GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}

	count := 0
	for _, b := range w.Bytes() {
		count += int(b)
	}
	if count != 0 {
		t.Errorf("expect 0 count, got %d", count)
	}
}

func TestDownloadPartBodyRetry_SuccessRetry(t *testing.T) {
	s, names := dlLoggingSvcWithErrReader([]testErrReader{
		{Buf: []byte("ab"), Len: 3, Err: io.ErrUnexpectedEOF},
		{Buf: []byte("123"), Len: 3, Err: io.EOF},
	})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})

	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(3), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject", "GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}
	if e, a := "123", string(w.Bytes()); e != a {
		t.Errorf("expect %q response, got %q", e, a)
	}
}

func TestDownloadPartBodyRetry_SuccessNoRetry(t *testing.T) {
	s, names := dlLoggingSvcWithErrReader([]testErrReader{
		{Buf: []byte("abc"), Len: 3, Err: io.EOF},
	})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})

	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(3), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}
	if e, a := "abc", string(w.Bytes()); e != a {
		t.Errorf("expect %q response, got %q", e, a)
	}
}

func TestDownloadPartBodyRetry_FailRetry(t *testing.T) {
	s, names := dlLoggingSvcWithErrReader([]testErrReader{
		{Buf: []byte("ab"), Len: 3, Err: io.ErrUnexpectedEOF},
	})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 1
	})

	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})

	if err == nil {
		t.Fatalf("expect error, got none")
	}
	if e, a := "unexpected EOF", err.Error(); !strings.Contains(a, e) {
		t.Errorf("expect %q error message to be in %q", e, a)
	}
	if e, a := int64(2), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}
	if e, a := "ab", string(w.Bytes()); e != a {
		t.Errorf("expect %q response, got %q", e, a)
	}
}

func TestDownloadWithContextCanceled(t *testing.T) {
	d := s3manager.NewDownloader(unit.Session)

	params := s3.GetObjectInput{
		Bucket: aws.String("Bucket"),
		Key:    aws.String("Key"),
	}

	ctx := &awstesting.FakeContext{DoneCh: make(chan struct{})}
	ctx.Error = fmt.Errorf("context canceled")
	close(ctx.DoneCh)

	w := &aws.WriteAtBuffer{}

	_, err := d.DownloadWithContext(ctx, w, &params)
	if err == nil {
		t.Fatalf("expected error, did not get one")
	}
	aerr := err.(awserr.Error)
	if e, a := request.CanceledErrorCode, aerr.Code(); e != a {
		t.Errorf("expected error code %q, got %q", e, a)
	}
	if e, a := "canceled", aerr.Message(); !strings.Contains(a, e) {
		t.Errorf("expected error message to contain %q, but did not %q", e, a)
	}
}

func TestDownload_WithRange(t *testing.T) {
	s, names, ranges := dlLoggingSvc([]byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9})

	d := s3manager.NewDownloaderWithClient(s, func(d *s3manager.Downloader) {
		d.Concurrency = 10 // should be ignored
		d.PartSize = 1     // should be ignored
	})

	w := &aws.WriteAtBuffer{}
	n, err := d.Download(w, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
		Range:  aws.String("bytes=2-6"),
	})

	if err != nil {
		t.Fatalf("expect no error, got %v", err)
	}
	if e, a := int64(5), n; e != a {
		t.Errorf("expect %d bytes read, got %d", e, a)
	}
	expectCalls := []string{"GetObject"}
	if e, a := expectCalls, *names; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v API calls, got %v", e, a)
	}
	expectRngs := []string{"bytes=2-6"}
	if e, a := expectRngs, *ranges; !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v ranges, got %v", e, a)
	}
	expectBytes := []byte{2, 3, 4, 5, 6}
	if e, a := expectBytes, w.Bytes(); !reflect.DeepEqual(e, a) {
		t.Errorf("expect %v bytes, got %v", e, a)
	}
}

func TestDownload_WithFailure(t *testing.T) {
	svc := s3.New(unit.Session)
	svc.Handlers.Send.Clear()

	reqCount := int64(0)
	startingByte := 0
	svc.Handlers.Send.PushBack(func(r *request.Request) {
		switch atomic.LoadInt64(&reqCount) {
		case 1:
			// Give a chance for the multipart chunks to be queued up
			time.Sleep(1 * time.Second)

			r.HTTPResponse = &http.Response{
				Header: http.Header{},
				Body:   ioutil.NopCloser(&bytes.Buffer{}),
			}
			r.Error = awserr.New("ConnectionError", "some connection error", nil)
			r.Retryable = aws.Bool(false)

		default:
			body := bytes.NewReader(make([]byte, s3manager.DefaultDownloadPartSize))
			r.HTTPResponse = &http.Response{
				StatusCode:    http.StatusOK,
				Status:        http.StatusText(http.StatusOK),
				ContentLength: int64(body.Len()),
				Body:          ioutil.NopCloser(body),
				Header:        http.Header{},
			}
			r.HTTPResponse.Header.Set("Content-Length", strconv.Itoa(body.Len()))
			r.HTTPResponse.Header.Set("Content-Range",
				fmt.Sprintf("bytes %d-%d/%d", startingByte, body.Len()-1, body.Len()*10))

			startingByte += body.Len()
			if reqCount > 0 {
				// sleep here to ensure context switching between goroutines
				time.Sleep(25 * time.Millisecond)
			}
		}

		atomic.AddInt64(&reqCount, 1)
	})

	d := s3manager.NewDownloaderWithClient(svc, func(d *s3manager.Downloader) {
		d.Concurrency = 2
	})

	w := &aws.WriteAtBuffer{}
	params := s3.GetObjectInput{
		Bucket: aws.String("Bucket"),
		Key:    aws.String("Key"),
	}

	// Expect this request to exit quickly after failure
	_, err := d.Download(w, &params)
	if err == nil {
		t.Fatalf("expect error, got none")
	}

	if atomic.LoadInt64(&reqCount) > 3 {
		t.Errorf("expect no more than 3 requests, but received %d", reqCount)
	}
}

func TestDownloadBufferStrategy(t *testing.T) {
	cases := map[string]struct {
		partSize     int64
		strategy     *recordedWriterReadFromProvider
		expectedSize int64
	}{
		"no strategy": {
			partSize:     s3manager.DefaultDownloadPartSize,
			expectedSize: 10 * sdkio.MebiByte,
		},
		"partSize modulo bufferSize == 0": {
			partSize: 5 * sdkio.MebiByte,
			strategy: &recordedWriterReadFromProvider{
				WriterReadFromProvider: s3manager.NewPooledBufferedWriterReadFromProvider(int(sdkio.MebiByte)), // 1 MiB
			},
			expectedSize: 10 * sdkio.MebiByte, // 10 MiB
		},
		"partSize modulo bufferSize > 0": {
			partSize: 5 * 1024 * 1204, // 5 MiB
			strategy: &recordedWriterReadFromProvider{
				WriterReadFromProvider: s3manager.NewPooledBufferedWriterReadFromProvider(2 * int(sdkio.MebiByte)), // 2 MiB
			},
			expectedSize: 10 * sdkio.MebiByte, // 10 MiB
		},
	}

	for name, tCase := range cases {
		t.Logf("starting case: %v", name)

		expected := getTestBytes(int(tCase.expectedSize))

		svc, _, _ := dlLoggingSvc(expected)

		d := s3manager.NewDownloaderWithClient(svc, func(d *s3manager.Downloader) {
			d.PartSize = tCase.partSize
			if tCase.strategy != nil {
				d.BufferProvider = tCase.strategy
			}
		})

		buffer := aws.NewWriteAtBuffer(make([]byte, len(expected)))

		n, err := d.Download(buffer, &s3.GetObjectInput{
			Bucket: aws.String("bucket"),
			Key:    aws.String("key"),
		})
		if err != nil {
			t.Errorf("failed to download: %v", err)
		}

		if e, a := len(expected), int(n); e != a {
			t.Errorf("expected %v, got %v downloaded bytes", e, a)
		}

		if e, a := expected, buffer.Bytes(); !bytes.Equal(e, a) {
			t.Errorf("downloaded bytes did not match expected")
		}

		if tCase.strategy != nil {
			if e, a := tCase.strategy.callbacksVended, tCase.strategy.callbacksExecuted; e != a {
				t.Errorf("expected %v, got %v", e, a)
			}
		}
	}
}

var randBytes = func() []byte {
	rr := rand.New(rand.NewSource(0))
	b := make([]byte, 10*sdkio.MebiByte)

	if _, err := sdkrand.Read(rr, b); err != nil {
		panic(fmt.Sprintf("failed to read random bytes, %v", err))
	}
	return b
}()

func getTestBytes(size int) []byte {
	if len(randBytes) >= size {
		return randBytes[:size]
	}

	b := append(randBytes, getTestBytes(size-len(randBytes))...)
	return b
}

type testErrReader struct {
	Buf []byte
	Err error
	Len int64

	off int
}

func (r *testErrReader) Read(p []byte) (int, error) {
	to := len(r.Buf) - r.off

	n := copy(p, r.Buf[r.off:to])
	r.off += n

	if n < len(p) {
		return n, r.Err

	}

	return n, nil
}

func TestDownloadBufferStrategy_Errors(t *testing.T) {
	expected := getTestBytes(int(10 * sdkio.MebiByte))

	svc, _, _ := dlLoggingSvc(expected)
	strat := &recordedWriterReadFromProvider{
		WriterReadFromProvider: s3manager.NewPooledBufferedWriterReadFromProvider(int(2 * sdkio.MebiByte)),
	}

	d := s3manager.NewDownloaderWithClient(svc, func(d *s3manager.Downloader) {
		d.PartSize = 5 * sdkio.MebiByte
		d.BufferProvider = strat
		d.Concurrency = 1
	})

	seenOps := make(map[string]struct{})
	svc.Handlers.Send.PushFront(func(*request.Request) {})
	svc.Handlers.Send.AfterEachFn = func(item request.HandlerListRunItem) bool {
		r := item.Request

		if r.Operation.Name != "GetObject" {
			return true
		}

		input := r.Params.(*s3.GetObjectInput)

		fingerPrint := fmt.Sprintf("%s/%s/%s/%s", r.Operation.Name, *input.Bucket, *input.Key, *input.Range)
		if _, ok := seenOps[fingerPrint]; ok {
			return true
		}
		seenOps[fingerPrint] = struct{}{}

		regex := regexp.MustCompile(`bytes=(\d+)-(\d+)`)
		rng := regex.FindStringSubmatch(*input.Range)
		start, _ := strconv.ParseInt(rng[1], 10, 64)
		fin, _ := strconv.ParseInt(rng[2], 10, 64)

		_, _ = io.Copy(ioutil.Discard, r.Body)
		r.HTTPResponse = &http.Response{
			StatusCode:    200,
			Body:          aws.ReadSeekCloser(&badReader{err: io.ErrUnexpectedEOF}),
			ContentLength: fin - start,
		}

		return false
	}

	buffer := aws.NewWriteAtBuffer(make([]byte, len(expected)))

	n, err := d.Download(buffer, &s3.GetObjectInput{
		Bucket: aws.String("bucket"),
		Key:    aws.String("key"),
	})
	if err != nil {
		t.Errorf("failed to download: %v", err)
	}

	if e, a := len(expected), int(n); e != a {
		t.Errorf("expected %v, got %v downloaded bytes", e, a)
	}

	if e, a := expected, buffer.Bytes(); !bytes.Equal(e, a) {
		t.Errorf("downloaded bytes did not match expected")
	}

	if e, a := strat.callbacksVended, strat.callbacksExecuted; e != a {
		t.Errorf("expected %v, got %v", e, a)
	}
}

type recordedWriterReadFromProvider struct {
	callbacksVended   uint32
	callbacksExecuted uint32
	s3manager.WriterReadFromProvider
}

func (r *recordedWriterReadFromProvider) GetReadFrom(writer io.Writer) (s3manager.WriterReadFrom, func()) {
	w, cleanup := r.WriterReadFromProvider.GetReadFrom(writer)

	atomic.AddUint32(&r.callbacksVended, 1)
	return w, func() {
		atomic.AddUint32(&r.callbacksExecuted, 1)
		cleanup()
	}
}

type badReader struct {
	err error
}

func (b *badReader) Read(p []byte) (int, error) {
	tb := getTestBytes(len(p))
	copy(p, tb)

	return len(p), b.err
}

var mockErrorResponse = struct {
	XMLName xml.Name `xml:"Error"`
	Code    string   `xml:"Code"`
	Message string   `xml:"Message"`
}{
	Code:    "MOCK_S3_ERROR_CODE",
	Message: "Mocked S3 Error Message",
}
