1 files changed, 96 insertions, 0 deletions
diff --git a/mapr/selectcondition.go b/mapr/selectcondition.go
new file mode 100644
index 0000000..1882b7e
--- /dev/null
+++ b/mapr/selectcondition.go
@@ -0,0 +1,96 @@
+package mapr
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// AggregateOperation is to specify the aggregate operation type.
+type AggregateOperation int
+
+// Aggregate operation types
+const (
+	UndefAggregateOperation AggregateOperation = iota
+	Count                   AggregateOperation = iota
+	Sum                     AggregateOperation = iota
+	Min                     AggregateOperation = iota
+	Max                     AggregateOperation = iota
+	Last                    AggregateOperation = iota
+	Avg                     AggregateOperation = iota
+	Len                     AggregateOperation = iota
+)
+
+// Represents a parsed "select" clause, used by mapr.Query.
+type selectCondition struct {
+	Field        string
+	FieldStorage string
+	Operation    AggregateOperation
+}
+
+func (sc selectCondition) String() string {
+	return fmt.Sprintf("selectCondition(Field:%s,FieldStorage:%s,Operation:%v)",
+		sc.Field,
+		sc.FieldStorage,
+		sc.Operation)
+}
+
+func makeSelectConditions(tokens []token) ([]selectCondition, error) {
+	var sel []selectCondition
+
+	// Parse select aggregation, e.g. sum(foo)
+	parse := func(token token) (selectCondition, error) {
+		var sc selectCondition
+		tokenStr := strings.ToLower(token.str)
+
+		if !strings.Contains(tokenStr, "(") && !strings.Contains(tokenStr, ")") {
+			sc.Field = tokenStr
+			sc.FieldStorage = tokenStr
+			sc.Operation = Last
+			return sc, nil
+		}
+
+		a := strings.Split(tokenStr, "(")
+		if len(a) != 2 {
+			return sc, errors.New(invalidQuery + "Can't parse 'select' aggregation: " + token.str)
+		}
+		agg := a[0] // Aggregation, e.g. 'sum'
+
+		b := strings.Split(a[1], ")")
+		if len(b) != 2 {
+			return sc, errors.New(invalidQuery + "Can't parse 'select' field name from aggregation: " + token.str)
+		}
+		sc.Field = b[0]            // Field name, e.g. 'foo'
+		sc.FieldStorage = tokenStr // e.g. 'sum(foo)'
+
+		switch agg {
+		case "count":
+			sc.Operation = Count
+		case "sum":
+			sc.Operation = Sum
+		case "min":
+			sc.Operation = Min
+		case "max":
+			sc.Operation = Max
+		case "last":
+			sc.Operation = Last
+		case "avg":
+			sc.Operation = Avg
+		case "len":
+			sc.Operation = Len
+		default:
+			return sc, errors.New(invalidQuery + "Unknown aggregation in 'select' clause: " + agg)
+		}
+
+		return sc, nil
+	}
+
+	for _, token := range tokens {
+		sc, err := parse(token)
+		if err != nil {
+			return nil, err
+		}
+		sel = append(sel, sc)
+	}
+	return sel, nil
+}