/*
 * Minio Cloud Storage, (C) 2016 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package objcache

import (
	"bytes"
	"io"
	"testing"
	"time"
)

// TestObjectCache tests cases of object cache with expiry.
func TestObjExpiry(t *testing.T) {
	// Non exhaustive list of all object cache behavior cases.
	testCases := []struct {
		expiry    time.Duration
		cacheSize uint64
		err       error
		closeErr  error
	}{
		{
			expiry:    100 * time.Millisecond,
			cacheSize: 1024,
			err:       ErrKeyNotFoundInCache,
			closeErr:  nil,
		},
	}

	// Test case 1 validates running of GC.
	testCase := testCases[0]
	cache, err := New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	cache.OnEviction = func(key string) {}
	w, err := cache.Create("test", 1)
	if err != nil {
		t.Errorf("Test case 1 expected to pass, failed instead %s", err)
	}
	// Write a byte.
	w.Write([]byte("1"))
	if err = w.Close(); err != nil {
		t.Errorf("Test case 1 expected to pass, failed instead %s", err)
	}
	// Wait for 500 millisecond.
	time.Sleep(500 * time.Millisecond)
	// Setting objModTime to the beginning of golang's time.Time to avoid deletion of stale entry.
	fakeObjModTime := time.Time{}
	_, err = cache.Open("test", fakeObjModTime)
	if err != testCase.err {
		t.Errorf("Test case 1 expected %s, got instead %s", testCase.err, err)
	}
}

// TestObjCache - tests various cases for object cache behavior.
func TestObjCache(t *testing.T) {
	// Setting objModTime to the beginning of golang's time.Time to avoid deletion of stale entry.
	fakeObjModTime := time.Time{}

	// Non exhaustive list of all object cache behavior cases.
	testCases := []struct {
		expiry    time.Duration
		cacheSize uint64
		err       error
		closeErr  error
	}{
		// Validate if a key is not found in cache and Open fails.
		{
			expiry:    NoExpiry,
			cacheSize: 1024,
			err:       ErrKeyNotFoundInCache,
		},
		// Validate if cache indicates that it is full and Create fails.
		{
			expiry:    NoExpiry,
			cacheSize: 1,
			err:       ErrCacheFull,
		},
		// Validate if Create succeeds but Close fails to write to buffer.
		{
			expiry:    NoExpiry,
			cacheSize: 2,
			closeErr:  io.ErrShortBuffer,
		},
		// Validate that Create and Close succeed, making sure to update the cache.
		{
			expiry:    NoExpiry,
			cacheSize: 1024,
		},
		// Validate that Delete succeeds and Open fails with key not found in cache.
		{
			expiry:    NoExpiry,
			cacheSize: 1024,
			err:       ErrKeyNotFoundInCache,
		},
		// Validate OnEviction function is called upon entry delete.
		{
			expiry:    NoExpiry,
			cacheSize: 1024,
		},
		// Validate error excess data.
		{
			expiry:    NoExpiry,
			cacheSize: 5,
			closeErr:  ErrExcessData,
		},
		// Validate error excess data during write.
		{
			expiry:    NoExpiry,
			cacheSize: 2048,
			err:       ErrExcessData,
		},
	}

	// Test 1 validating Open failure.
	testCase := testCases[0]
	cache, err := New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	_, err = cache.Open("test", fakeObjModTime)
	if testCase.err != err {
		t.Errorf("Test case 2 expected to pass, failed instead %s", err)
	}

	// Test 2 validating Create failure.
	testCase = testCases[1]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	_, err = cache.Create("test", 2)
	if testCase.err != err {
		t.Errorf("Test case 2 expected to pass, failed instead %s", err)
	}

	// Test 3 validating Create succeeds and returns a writer.
	// Subsequently we Close() without writing any data, to receive
	// `io.ErrShortBuffer`
	testCase = testCases[2]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err := cache.Create("test", 1)
	if testCase.err != err {
		t.Errorf("Test case 3 expected to pass, failed instead %s", err)
	}
	if err = w.Close(); err != testCase.closeErr {
		t.Errorf("Test case 3 expected to pass, failed instead %s", err)
	}

	// Test 4 validates Create and Close succeeds successfully caching
	// the writes.
	testCase = testCases[3]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err = cache.Create("test", 5)
	if testCase.err != err {
		t.Errorf("Test case 4 expected to pass, failed instead %s", err)
	}
	// Write '5' bytes.
	w.Write([]byte("Hello"))
	// Close to successfully save into cache.
	if err = w.Close(); err != nil {
		t.Errorf("Test case 4 expected to pass, failed instead %s", err)
	}
	r, err := cache.Open("test", fakeObjModTime)
	if err != nil {
		t.Errorf("Test case 4 expected to pass, failed instead %s", err)
	}
	// Reads everything stored for key "test".
	cbytes := make([]byte, 5)
	_, err = r.ReadAt(cbytes, 0)
	if err != nil {
		t.Errorf("Test case 4 expected to pass, failed instead %s", err)
	}
	// Validate if read bytes match.
	if !bytes.Equal(cbytes, []byte("Hello")) {
		t.Errorf("Test case 4 expected to pass. wanted \"Hello\", got %s", string(cbytes))
	}

	// Test 5 validates Delete succeeds and Open fails with err
	testCase = testCases[4]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err = cache.Create("test", 5)
	if err != nil {
		t.Errorf("Test case 5 expected to pass, failed instead %s", err)
	}
	// Write '5' bytes.
	w.Write([]byte("Hello"))
	// Close to successfully save into cache.
	if err = w.Close(); err != nil {
		t.Errorf("Test case 5 expected to pass, failed instead %s", err)
	}
	// Delete the cache entry.
	cache.Delete("test")
	_, err = cache.Open("test", fakeObjModTime)
	if testCase.err != err {
		t.Errorf("Test case 5 expected to pass, failed instead %s", err)
	}

	// Test 6 validates OnEviction being called upon Delete is being invoked.
	testCase = testCases[5]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err = cache.Create("test", 5)
	if err != nil {
		t.Errorf("Test case 6 expected to pass, failed instead %s", err)
	}
	// Write '5' bytes.
	w.Write([]byte("Hello"))
	// Close to successfully save into cache.
	if err = w.Close(); err != nil {
		t.Errorf("Test case 6 expected to pass, failed instead %s", err)
	}
	var deleteKey string
	cache.OnEviction = func(key string) {
		deleteKey = key
	}
	// Delete the cache entry.
	cache.Delete("test")
	if deleteKey != "test" {
		t.Errorf("Test case 6 expected to pass, wanted \"test\", got %s", deleteKey)
	}

	// Test 7 validates rejecting requests when excess data is being saved.
	testCase = testCases[6]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err = cache.Create("test1", 5)
	if err != nil {
		t.Errorf("Test case 7 expected to pass, failed instead %s", err)
	}
	// Write '5' bytes.
	w.Write([]byte("Hello"))
	// Close to successfully save into cache.
	if err = w.Close(); err != nil {
		t.Errorf("Test case 7 expected to pass, failed instead %s", err)
	}
	_, err = cache.Create("test2", 1)
	if err != ErrCacheFull {
		t.Errorf("Test case 7 expected to pass, failed instead %s", err)
	}

	// Test 8 validates rejecting Writes which write excess data.
	testCase = testCases[7]
	cache, err = New(testCase.cacheSize, testCase.expiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err = cache.Create("test1", 5)
	if err != nil {
		t.Errorf("Test case 8 expected to pass, failed instead %s", err)
	}
	// Write '5' bytes.
	n, err := w.Write([]byte("Hello"))
	if err != nil {
		t.Errorf("Test case 8 expected to pass, failed instead %s", err)
	}
	if n != 5 {
		t.Errorf("Test case 8 expected 5 bytes written, instead found %d", n)
	}
	// Write '1' more byte, should return error.
	n, err = w.Write([]byte("W"))
	if n == 0 && err != testCase.err {
		t.Errorf("Test case 8 expected to fail with ErrExcessData, but failed with %s instead", err)
	}
}

// TestStateEntryPurge - tests if objCache purges stale entry and returns ErrKeyNotFoundInCache.
func TestStaleEntryPurge(t *testing.T) {
	cache, err := New(1024, NoExpiry)
	if err != nil {
		t.Fatalf("Unable to create new objcache")
	}

	w, err := cache.Create("test", 5)
	if err != nil {
		t.Errorf("Test case expected to pass, failed instead %s", err)
	}
	// Write '5' bytes.
	w.Write([]byte("Hello"))
	// Close to successfully save into cache.
	if err = w.Close(); err != nil {
		t.Errorf("Test case expected to pass, failed instead %s", err)
	}

	_, err = cache.Open("test", time.Now().AddDate(0, 0, 1).UTC())
	if err != ErrKeyNotFoundInCache {
		t.Errorf("Test case expected to return ErrKeyNotFoundInCache, instead returned %s", err)
	}
}