Issue search support elasticsearch (#9428)

* Issue search support elasticsearch

* Fix lint

* Add indexer name on app.ini

* add a warnning on SearchIssuesByKeyword

* improve code

vendor/github.com/olivere/elastic/v7/suggester_context.go

@@ -0,0 +1,124 @@
+// Copyright 2012-present Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+import "errors"
+
+// SuggesterContextQuery is used to define context information within
+// a suggestion request.
+type SuggesterContextQuery interface {
+	Source() (interface{}, error)
+}
+
+// ContextSuggester is a fast suggester for e.g. type-ahead completion that supports filtering and boosting based on contexts.
+// See https://www.elastic.co/guide/en/elasticsearch/reference/7.0/suggester-context.html
+// for more details.
+type ContextSuggester struct {
+	Suggester
+	name           string
+	prefix         string
+	field          string
+	size           *int
+	contextQueries []SuggesterContextQuery
+}
+
+// Creates a new context suggester.
+func NewContextSuggester(name string) *ContextSuggester {
+	return &ContextSuggester{
+		name:           name,
+		contextQueries: make([]SuggesterContextQuery, 0),
+	}
+}
+
+func (q *ContextSuggester) Name() string {
+	return q.name
+}
+
+func (q *ContextSuggester) Prefix(prefix string) *ContextSuggester {
+	q.prefix = prefix
+	return q
+}
+
+func (q *ContextSuggester) Field(field string) *ContextSuggester {
+	q.field = field
+	return q
+}
+
+func (q *ContextSuggester) Size(size int) *ContextSuggester {
+	q.size = &size
+	return q
+}
+
+func (q *ContextSuggester) ContextQuery(query SuggesterContextQuery) *ContextSuggester {
+	q.contextQueries = append(q.contextQueries, query)
+	return q
+}
+
+func (q *ContextSuggester) ContextQueries(queries ...SuggesterContextQuery) *ContextSuggester {
+	q.contextQueries = append(q.contextQueries, queries...)
+	return q
+}
+
+// contextSuggesterRequest is necessary because the order in which
+// the JSON elements are routed to Elasticsearch is relevant.
+// We got into trouble when using plain maps because the text element
+// needs to go before the completion element.
+type contextSuggesterRequest struct {
+	Prefix     string      `json:"prefix"`
+	Completion interface{} `json:"completion"`
+}
+
+// Creates the source for the context suggester.
+func (q *ContextSuggester) Source(includeName bool) (interface{}, error) {
+	cs := &contextSuggesterRequest{}
+
+	if q.prefix != "" {
+		cs.Prefix = q.prefix
+	}
+
+	suggester := make(map[string]interface{})
+	cs.Completion = suggester
+
+	if q.field != "" {
+		suggester["field"] = q.field
+	}
+	if q.size != nil {
+		suggester["size"] = *q.size
+	}
+	switch len(q.contextQueries) {
+	case 0:
+	case 1:
+		src, err := q.contextQueries[0].Source()
+		if err != nil {
+			return nil, err
+		}
+		suggester["contexts"] = src
+	default:
+		ctxq := make(map[string]interface{})
+		for _, query := range q.contextQueries {
+			src, err := query.Source()
+			if err != nil {
+				return nil, err
+			}
+			// Merge the dictionary into ctxq
+			m, ok := src.(map[string]interface{})
+			if !ok {
+				return nil, errors.New("elastic: context query is not a map")
+			}
+			for k, v := range m {
+				ctxq[k] = v
+			}
+		}
+		suggester["contexts"] = ctxq
+	}
+
+	if !includeName {
+		return cs, nil
+	}
+
+	source := make(map[string]interface{})
+	source[q.name] = cs
+	return source, nil
+}