add routing rule for node

routing/rules/parser.go

@@ -0,0 +1,141 @@
+package rules
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/vulcand/predicate"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+const (
+	and = "and"
+	or  = "or"
+)
+
+type Parser = predicate.Parser
+
+// TreeBuilder defines the type for a Tree builder.
+type TreeBuilder func() *Tree
+
+// Tree represents the rules' tree structure.
+type Tree struct {
+	Matcher   string
+	Not       bool
+	Value     []string
+	RuleLeft  *Tree
+	RuleRight *Tree
+}
+
+// NewParser constructs a parser for the given matchers.
+func NewParser(matchers []string) (predicate.Parser, error) {
+	parserFuncs := make(map[string]interface{})
+
+	for _, matcherName := range matchers {
+		fn := func(value ...string) TreeBuilder {
+			return func() *Tree {
+				return &Tree{
+					Matcher: matcherName,
+					Value:   value,
+				}
+			}
+		}
+		parserFuncs[matcherName] = fn
+		parserFuncs[strings.ToLower(matcherName)] = fn
+		parserFuncs[strings.ToUpper(matcherName)] = fn
+		parserFuncs[cases.Title(language.Und).String(strings.ToLower(matcherName))] = fn
+	}
+
+	return predicate.NewParser(predicate.Def{
+		Operators: predicate.Operators{
+			AND: andFunc,
+			OR:  orFunc,
+			NOT: notFunc,
+		},
+		Functions: parserFuncs,
+	})
+}
+
+func andFunc(left, right TreeBuilder) TreeBuilder {
+	return func() *Tree {
+		return &Tree{
+			Matcher:   and,
+			RuleLeft:  left(),
+			RuleRight: right(),
+		}
+	}
+}
+
+func orFunc(left, right TreeBuilder) TreeBuilder {
+	return func() *Tree {
+		return &Tree{
+			Matcher:   or,
+			RuleLeft:  left(),
+			RuleRight: right(),
+		}
+	}
+}
+
+func invert(t *Tree) *Tree {
+	switch t.Matcher {
+	case or:
+		t.Matcher = and
+		t.RuleLeft = invert(t.RuleLeft)
+		t.RuleRight = invert(t.RuleRight)
+	case and:
+		t.Matcher = or
+		t.RuleLeft = invert(t.RuleLeft)
+		t.RuleRight = invert(t.RuleRight)
+	default:
+		t.Not = !t.Not
+	}
+
+	return t
+}
+
+func notFunc(elem TreeBuilder) TreeBuilder {
+	return func() *Tree {
+		return invert(elem())
+	}
+}
+
+// ParseMatchers returns the subset of matchers in the Tree matching the given matchers.
+func (tree *Tree) ParseMatchers(matchers []string) []string {
+	switch tree.Matcher {
+	case and, or:
+		return append(tree.RuleLeft.ParseMatchers(matchers), tree.RuleRight.ParseMatchers(matchers)...)
+	default:
+		for _, matcher := range matchers {
+			if tree.Matcher == matcher {
+				return lower(tree.Value)
+			}
+		}
+
+		return nil
+	}
+}
+
+// CheckRule validates the given rule.
+func CheckRule(rule *Tree) error {
+	if len(rule.Value) == 0 {
+		return fmt.Errorf("no args for matcher %s", rule.Matcher)
+	}
+
+	for _, v := range rule.Value {
+		if len(v) == 0 {
+			return fmt.Errorf("empty args for matcher %s, %v", rule.Matcher, rule.Value)
+		}
+	}
+
+	return nil
+}
+
+func lower(slice []string) []string {
+	var lowerStrings []string
+	for _, value := range slice {
+		lowerStrings = append(lowerStrings, strings.ToLower(value))
+	}
+
+	return lowerStrings
+}