From fe2680609274d50ef77b6ee84dd4c0c68bac67d0 Mon Sep 17 00:00:00 2001
From: Steven Allen <steven@stebalien.com>
Date: Fri, 3 Jan 2020 18:08:28 -0800
Subject: [PATCH] test(gateway): test the lazy seeker

---
 core/corehttp/lazyseek_test.go | 137 +++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)
 create mode 100644 core/corehttp/lazyseek_test.go

diff --git a/core/corehttp/lazyseek_test.go b/core/corehttp/lazyseek_test.go
new file mode 100644
index 00000000000..144e57d0f27
--- /dev/null
+++ b/core/corehttp/lazyseek_test.go
@@ -0,0 +1,137 @@
+package corehttp
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"strings"
+	"testing"
+)
+
+type badSeeker struct {
+	io.ReadSeeker
+}
+
+var badSeekErr = fmt.Errorf("I'm a bad seeker")
+
+func (bs badSeeker) Seek(offset int64, whence int) (int64, error) {
+	off, err := bs.ReadSeeker.Seek(0, io.SeekCurrent)
+	if err != nil {
+		panic(err)
+	}
+	return off, badSeekErr
+}
+
+func TestLazySeekerError(t *testing.T) {
+	underlyingBuffer := strings.NewReader("fubar")
+	s := &lazySeeker{
+		reader: badSeeker{underlyingBuffer},
+		size:   underlyingBuffer.Size(),
+	}
+	off, err := s.Seek(0, io.SeekEnd)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if off != s.size {
+		t.Fatal("expected to seek to the end")
+	}
+
+	// shouldn't have actually seeked.
+	b, err := ioutil.ReadAll(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(b) != 0 {
+		t.Fatal("expected to read nothing")
+	}
+
+	// shouldn't need to actually seek.
+	off, err = s.Seek(0, io.SeekStart)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if off != 0 {
+		t.Fatal("expected to seek to the start")
+	}
+	b, err = ioutil.ReadAll(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(b) != "fubar" {
+		t.Fatal("expected to read string")
+	}
+
+	// should fail the second time.
+	off, err = s.Seek(0, io.SeekStart)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if off != 0 {
+		t.Fatal("expected to seek to the start")
+	}
+	// right here...
+	b, err = ioutil.ReadAll(s)
+	if err == nil {
+		t.Fatalf("expected an error, got output %s", string(b))
+	}
+	if err != badSeekErr {
+		t.Fatalf("expected a bad seek error, got %s", err)
+	}
+	if len(b) != 0 {
+		t.Fatalf("expected to read nothing")
+	}
+}
+
+func TestLazySeeker(t *testing.T) {
+	underlyingBuffer := strings.NewReader("fubar")
+	s := &lazySeeker{
+		reader: underlyingBuffer,
+		size:   underlyingBuffer.Size(),
+	}
+	expectByte := func(b byte) {
+		t.Helper()
+		var buf [1]byte
+		n, err := io.ReadFull(s, buf[:])
+		if err != nil {
+			t.Fatal(err)
+		}
+		if n != 1 {
+			t.Fatalf("expected to read one byte, read %d", n)
+		}
+		if buf[0] != b {
+			t.Fatalf("expected %b, got %b", b, buf[0])
+		}
+	}
+	expectSeek := func(whence int, off, expOff int64, expErr string) {
+		t.Helper()
+		n, err := s.Seek(off, whence)
+		if expErr == "" {
+			if err != nil {
+				t.Fatal("unexpected seek error: ", err)
+			}
+		} else {
+			if err == nil || err.Error() != expErr {
+				t.Fatalf("expected %s, got %s", err, expErr)
+			}
+		}
+		if n != expOff {
+			t.Fatalf("expected offset %d, got, %d", expOff, n)
+		}
+	}
+
+	expectSeek(io.SeekEnd, 0, s.size, "")
+	b, err := ioutil.ReadAll(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(b) != 0 {
+		t.Fatal("expected to read nothing")
+	}
+	expectSeek(io.SeekEnd, -1, s.size-1, "")
+	expectByte('r')
+	expectSeek(io.SeekStart, 0, 0, "")
+	expectByte('f')
+	expectSeek(io.SeekCurrent, 1, 2, "")
+	expectByte('b')
+	expectSeek(io.SeekCurrent, -100, 3, "invalid seek offset")
+}