Add initial support for bucket lifecycle (#7563)

This PR is based off @sinhaashish's PR for object lifecycle
management, which includes support only for,
- Expiration of object
- Filter using object prefix (_not_ object tags)

N B the code for actual expiration of objects will be included in a
subsequent PR.

pkg/lifecycle/lifecycle_test.go

@@ -0,0 +1,160 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 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 lifecycle
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestParseLifecycleConfig(t *testing.T) {
+	// Test for  lifecycle config with more than 1000 rules
+	var manyRules []Rule
+	rule := Rule{
+		Status:     "Enabled",
+		Expiration: Expiration{Days: ExpirationDays(3)},
+	}
+	for i := 0; i < 1001; i++ {
+		manyRules = append(manyRules, rule)
+	}
+
+	manyRuleLcConfig, err := xml.Marshal(Lifecycle{Rules: manyRules})
+	if err != nil {
+		t.Fatal("Failed to marshal lifecycle config with more than 1000 rules")
+	}
+
+	// Test for lifecycle config with rules containing overlapping prefixes
+	rule1 := Rule{
+		Status:     "Enabled",
+		Expiration: Expiration{Days: ExpirationDays(3)},
+		Filter: Filter{
+			Prefix: "/a/b",
+		},
+	}
+	rule2 := Rule{
+		Status:     "Enabled",
+		Expiration: Expiration{Days: ExpirationDays(3)},
+		Filter: Filter{
+			Prefix: "/a/b/c",
+		},
+	}
+	overlappingRules := []Rule{rule1, rule2}
+	overlappingLcConfig, err := xml.Marshal(Lifecycle{Rules: overlappingRules})
+	if err != nil {
+		t.Fatal("Failed to marshal lifecycle config with rules having overlapping prefix")
+	}
+
+	testCases := []struct {
+		inputConfig string
+		expectedErr error
+	}{
+		{ // Valid lifecycle config
+			inputConfig: `<LifecycleConfiguration>
+	                              <Rule>
+	                              <Filter>
+	                                 <Prefix>prefix</Prefix>
+	                              </Filter>
+	                              <Status>Enabled</Status>
+	                              <Expiration><Days>3</Days></Expiration>
+	                              </Rule>
+                                      <Rule>
+	                              <Filter>
+	                                 <Prefix>another-prefix</Prefix>
+	                              </Filter>
+	                              <Status>Enabled</Status>
+	                              <Expiration><Days>3</Days></Expiration>
+	                              </Rule>
+	                              </LifecycleConfiguration>`,
+			expectedErr: nil,
+		},
+		{ // lifecycle config with no rules
+			inputConfig: `<LifecycleConfiguration>
+	                              </LifecycleConfiguration>`,
+			expectedErr: errLifecycleNoRule,
+		},
+		{ // lifecycle config with more than 1000 rules
+			inputConfig: string(manyRuleLcConfig),
+			expectedErr: errLifecycleTooManyRules,
+		},
+		{ // lifecycle config with rules having overlapping prefix
+			inputConfig: string(overlappingLcConfig),
+			expectedErr: errLifecycleOverlappingPrefix,
+		},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("Test %d", i+1), func(t *testing.T) {
+			var err error
+			if _, err = ParseLifecycleConfig(bytes.NewReader([]byte(tc.inputConfig))); err != tc.expectedErr {
+				t.Fatalf("%d: Expected %v but got %v", i+1, tc.expectedErr, err)
+			}
+
+		})
+
+	}
+}
+
+// TestMarshalLifecycleConfig checks if lifecycleconfig xml
+// marshaling/unmarshaling can handle output from each other
+func TestMarshalLifecycleConfig(t *testing.T) {
+	// Time at midnight UTC
+	midnightTS := ExpirationDate{time.Date(2019, time.April, 20, 0, 0, 0, 0, time.UTC)}
+	lc := Lifecycle{
+		Rules: []Rule{
+			{
+				Status:     "Enabled",
+				Filter:     Filter{Prefix: "prefix-1"},
+				Expiration: Expiration{Days: ExpirationDays(3)},
+			},
+			{
+				Status:     "Enabled",
+				Filter:     Filter{Prefix: "prefix-1"},
+				Expiration: Expiration{Date: ExpirationDate(midnightTS)},
+			},
+		},
+	}
+	b, err := xml.MarshalIndent(&lc, "", "\t")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var lc1 Lifecycle
+	err = xml.Unmarshal(b, &lc1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ruleSet := make(map[string]struct{})
+	for _, rule := range lc.Rules {
+		ruleBytes, err := xml.Marshal(rule)
+		if err != nil {
+			t.Fatal(err)
+		}
+		ruleSet[string(ruleBytes)] = struct{}{}
+	}
+	for _, rule := range lc1.Rules {
+		ruleBytes, err := xml.Marshal(rule)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, ok := ruleSet[string(ruleBytes)]; !ok {
+			t.Fatalf("Expected %v to be equal to %v, %v missing", lc, lc1, rule)
+		}
+	}
+}