ElasticSearch support (Beta) (#31)

.editorconfig

@@ -5,3 +5,7 @@ root = true
 [{go.mod,go.sum,*.go,.gitmodules}]
 indent_style = tab
 indent_size = 4
+
+[*.json]
+indent_style = space
+indent_size = 2

README.md

@@ -390,6 +390,42 @@ func (l *LowerCaseEmail) VisitEq(first, second string) (*bson.D, error) {
 
 You can of course use the `FieldTypes` and `CustomQueryBuilder` together.
 
+#### Elastic Search (Open Search)
+
+The following examples shows how to generate a Elastic Search Query with this library.
+
+```go
+package example
+import epsearchast_v3 "github.com/elasticpath/epcc-search-ast-helper/external/epsearchast/v3"
+import epsearchast_v3_els "github.com/elasticpath/epcc-search-ast-helper/external/epsearchast/v3/els"
+
+func Example(ast *epsearchast_v3.AstNode, tenantBoundaryId string)  (string, error) {
+   // Not Shown: Validation
+
+   // Create query builder
+   var qb epsearchast_v3.SemanticReducer[epsearchast_v3_els.JsonObject] = epsearchast_v3_els.LowerCaseEmail{}
+
+   // Create Query Object
+   queryObj, err := epsearchast_v3.SemanticReduceAst(ast, qb)
+
+   if err != nil {
+      return nil, err
+   }
+
+   ...
+}
+
+type LowerCaseEmail struct {
+   epsearchast_v3_els.DefaultElsQueryBuilder
+}
+
+func (l *LowerCaseEmail) VisitEq(first, second string) (*bson.D, error) {
+   ....
+}
+
+```
+
+
 ### FAQ
 
 #### Design

external/epsearchast/v3/els/els_query_builder.go

@@ -0,0 +1,192 @@
+package epsearchast_v3_els
+
+import (
+	epsearchast_v3 "github.com/elasticpath/epcc-search-ast-helper/external/epsearchast/v3"
+	"strings"
+)
+
+type DefaultElsQueryBuilder struct {
+	OpTypeToFieldNames map[string]*OperatorTypeToMultiFieldName
+}
+
+type JsonObject map[string]interface{}
+
+// Elastic Search can encode data in multiple formats using multi fields
+// https://www.elastic.co/guide/en/elasticsearch/reference/current/multi-fields.html
+
+type OperatorTypeToMultiFieldName struct {
+	// The field name to use for equality operators (eq, in)
+	Equality string
+
+	// The field name to use for relational operators (lt, gt, le, ge)
+	Relational string
+
+	// The field name to use for text fields (nothing yet)
+	Text string
+
+	// The field name for use with array fields (not yet)
+	Array string
+
+	// The field name for wild card fields
+	Wildcard string
+}
+
+var _ epsearchast_v3.SemanticReducer[JsonObject] = (*DefaultElsQueryBuilder)(nil)
+
+func (d DefaultElsQueryBuilder) PostVisitAnd(rs []*JsonObject) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"bool": map[string]interface{}{
+			"must": rs,
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitIn(args ...string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"terms": map[string]interface{}{
+			d.getFieldMapping(args[0]).Equality: args[1:],
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitEq(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"term": map[string]interface{}{
+			d.getFieldMapping(first).Equality: second,
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitText(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"match_phrase": map[string]interface{}{
+			d.getFieldMapping(first).Text: second,
+		},
+	}), nil
+}
+
+// Useful doc: https://www.elastic.co/guide/en/elasticsearch/reference/7.17/query-dsl-range-query.html
+
+func (d DefaultElsQueryBuilder) VisitLe(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"range": map[string]interface{}{
+			d.getFieldMapping(first).Relational: map[string]interface{}{
+				"lte": second,
+			},
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitLt(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"range": map[string]interface{}{
+			d.getFieldMapping(first).Relational: map[string]interface{}{
+				"lt": second,
+			},
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitGe(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"range": map[string]interface{}{
+			d.getFieldMapping(first).Relational: map[string]interface{}{
+				"gte": second,
+			},
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitGt(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"range": map[string]interface{}{
+			d.getFieldMapping(first).Relational: map[string]interface{}{
+				"gt": second,
+			},
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitLike(first, second string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"wildcard": map[string]interface{}{
+			d.getFieldMapping(first).Wildcard: d.EscapeWildcardString(second),
+		},
+	}), nil
+}
+
+func (d DefaultElsQueryBuilder) VisitIsNull(first string) (*JsonObject, error) {
+	return (*JsonObject)(&map[string]interface{}{
+		"bool": map[string]interface{}{
+			"must_not": map[string]interface{}{
+				"exists": map[string]interface{}{
+					"field": d.getFieldMapping(first).Equality,
+				},
+			},
+		},
+	}), nil
+}
+
+// getFieldMapping returns the field name to use for a given operator type, the struct is always guaranteed to return f, if nothing was set.
+func (d DefaultElsQueryBuilder) getFieldMapping(f string) *OperatorTypeToMultiFieldName {
+	var o *OperatorTypeToMultiFieldName
+
+	if d.OpTypeToFieldNames[f] == nil {
+		o = &OperatorTypeToMultiFieldName{
+			Equality:   f,
+			Relational: f,
+			Text:       f,
+			Array:      f,
+			Wildcard:   f,
+		}
+	}
+
+	if v, ok := d.OpTypeToFieldNames[f]; ok {
+		o = &OperatorTypeToMultiFieldName{
+			Equality:   v.Equality,
+			Relational: v.Relational,
+			Text:       v.Text,
+			Array:      v.Array,
+			Wildcard:   v.Wildcard,
+		}
+
+		if o.Equality == "" {
+			o.Equality = f
+		}
+
+		if o.Relational == "" {
+			o.Relational = f
+		}
+
+		if o.Text == "" {
+			o.Text = f
+		}
+
+		if o.Array == "" {
+			o.Array = f
+		}
+
+		if o.Wildcard == "" {
+			o.Wildcard = f
+		}
+	}
+
+	return o
+}
+
+func (d DefaultElsQueryBuilder) EscapeWildcardString(s string) string {
+	str := strings.ReplaceAll(s, "?", `\?`)
+	str = strings.ReplaceAll(str, "*", `\*`)
+
+	if strings.HasPrefix(str, `\*`) {
+		str = str[1:]
+	}
+
+	if strings.HasSuffix(str, `\*`) {
+		str = str[:len(str)-2] + "*"
+	}
+
+	return str
+}
+
+// Generate an implementation of SemanticReducer[JsonObject] for the Elasticsearch query builder.