tag : break apart into smaller files of related function

tag/query.go

@@ -0,0 +1,43 @@
+package tag
+
+import "strings"
+
+type Operator string
+
+const (
+	SINGLE Operator = ""
+	OR     Operator = ","
+	AND    Operator = "+"
+	WILD   Operator = "*"
+)
+
+type Query struct {
+	Op   Operator
+	Tags []string
+}
+
+// TODO: only accepts one kind of syntax at a time
+func parseQuery(query string) Query {
+	// initialize for the single tag case:
+	q := Query{
+		Op:   SINGLE,
+		Tags: []string{query},
+	}
+	// count a missing tag as WILD:
+	if query == "" {
+		// TODO: somewhat abusing this concept for the empty query case:
+		q.Op = WILD
+		return q
+	}
+	// NOTE: will match OR first
+	ops := []Operator{OR, AND}
+	for _, op := range ops {
+		if s := strings.Split(query, string(op)); len(s) > 1 {
+			q.Op = op
+			q.Tags = s
+			break
+		}
+
+	}
+	return q
+}