Add search highlight formatter: plain. (#1683)

* Add search highlight formatter: plain.

* Fix copyright year.

* Revert copyright year on 2 formatters.

* Use different highlight before/after tags.

search/highlight/format/plain/plain.go

@@ -0,0 +1,89 @@
+//  Copyright (c) 2022 Couchbase, 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 plain
+
+import (
+	"github.com/blevesearch/bleve/v2/registry"
+	"github.com/blevesearch/bleve/v2/search/highlight"
+)
+
+const Name = "plain"
+
+const defaultPlainHighlightBefore = "<start>"
+const defaultPlainHighlightAfter = "<end>"
+
+type FragmentFormatter struct {
+	before string
+	after  string
+}
+
+func NewFragmentFormatter(before, after string) *FragmentFormatter {
+	return &FragmentFormatter{
+		before: before,
+		after:  after,
+	}
+}
+
+func (a *FragmentFormatter) Format(f *highlight.Fragment, orderedTermLocations highlight.TermLocations) string {
+	rv := ""
+	curr := f.Start
+	for _, termLocation := range orderedTermLocations {
+		if termLocation == nil {
+			continue
+		}
+		// make sure the array positions match
+		if !termLocation.ArrayPositions.Equals(f.ArrayPositions) {
+			continue
+		}
+		if termLocation.Start < curr {
+			continue
+		}
+		if termLocation.End > f.End {
+			break
+		}
+		// add the stuff before this location
+		rv += string(f.Orig[curr:termLocation.Start])
+		// start the highlight tag
+		rv += a.before
+		// add the term itself
+		rv += string(f.Orig[termLocation.Start:termLocation.End])
+		// end the highlight tag
+		rv += a.after
+		// update current
+		curr = termLocation.End
+	}
+	// add any remaining text after the last token
+	rv += string(f.Orig[curr:f.End])
+
+	return rv
+}
+
+func Constructor(config map[string]interface{}, cache *registry.Cache) (highlight.FragmentFormatter, error) {
+	before := defaultPlainHighlightBefore
+	beforeVal, ok := config["before"].(string)
+	if ok {
+		before = beforeVal
+	}
+	after := defaultPlainHighlightAfter
+	afterVal, ok := config["after"].(string)
+	if ok {
+		after = afterVal
+	}
+	return NewFragmentFormatter(before, after), nil
+}
+
+func init() {
+	registry.RegisterFragmentFormatter(Name, Constructor)
+}

search/highlight/format/plain/plain_test.go

@@ -0,0 +1,80 @@
+//  Copyright (c) 2022 Couchbase, 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 plain
+
+import (
+	"testing"
+
+	"github.com/blevesearch/bleve/v2/search"
+	"github.com/blevesearch/bleve/v2/search/highlight"
+)
+
+func TestPlainFragmentFormatter(t *testing.T) {
+	tests := []struct {
+		fragment *highlight.Fragment
+		tlm      search.TermLocationMap
+		output   string
+		start    string
+		end      string
+	}{
+		{
+			fragment: &highlight.Fragment{
+				Orig:  []byte("the quick brown fox"),
+				Start: 0,
+				End:   19,
+			},
+			tlm: search.TermLocationMap{
+				"quick": []*search.Location{
+					{
+						Pos:   2,
+						Start: 4,
+						End:   9,
+					},
+				},
+			},
+			output: "the <b>quick</b> brown fox",
+			start:  "<b>",
+			end:    "</b>",
+		},
+		{
+			fragment: &highlight.Fragment{
+				Orig:  []byte("the quick brown fox"),
+				Start: 0,
+				End:   19,
+			},
+			tlm: search.TermLocationMap{
+				"quick": []*search.Location{
+					{
+						Pos:   2,
+						Start: 4,
+						End:   9,
+					},
+				},
+			},
+			output: "the <em>quick</em> brown fox",
+			start:  "<em>",
+			end:    "</em>",
+		},
+	}
+
+	for _, test := range tests {
+		plainFormatter := NewFragmentFormatter(test.start, test.end)
+		otl := highlight.OrderTermLocations(test.tlm)
+		result := plainFormatter.Format(test.fragment, otl)
+		if result != test.output {
+			t.Errorf("expected `%s`, got `%s`", test.output, result)
+		}
+	}
+}