Move most code under lib

lib/condition/condition.go

@@ -0,0 +1,53 @@
+package condition
+
+import (
+	"fmt"
+	"github.com/google/cel-go/cel"
+	"strings"
+)
+
+type Condition struct {
+	Expression *cel.Ast
+}
+
+const (
+	OperatorOr  = "||"
+	OperatorAnd = "&&"
+)
+
+func FromStrings(env *cel.Env, operator string, conditions ...string) (*cel.Ast, error) {
+	var asts []*cel.Ast
+	for _, c := range conditions {
+		ast, issues := env.Compile(c)
+		if issues != nil && issues.Err() != nil {
+			return nil, fmt.Errorf("condition %s: %s", issues.Err(), c)
+		}
+		asts = append(asts, ast)
+	}
+
+	return Merge(env, operator, asts...)
+}
+
+func Merge(env *cel.Env, operator string, conditions ...*cel.Ast) (*cel.Ast, error) {
+	if len(conditions) == 0 {
+		return nil, nil
+	} else if len(conditions) == 1 {
+		return conditions[0], nil
+	}
+	var asts []string
+	for _, c := range conditions {
+		ast, err := cel.AstToString(c)
+		if err != nil {
+			return nil, err
+		}
+		asts = append(asts, "("+ast+")")
+	}
+
+	condition := strings.Join(asts, " "+operator+" ")
+	ast, issues := env.Compile(condition)
+	if issues != nil && issues.Err() != nil {
+		return nil, issues.Err()
+	}
+
+	return ast, nil
+}