Refactor frontends rules

Signed-off-by: Emile Vauge <emile@vauge.com>

rules.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"errors"
+	"github.com/gorilla/mux"
+	"reflect"
+	"strings"
+)
+
+// Rules holds rule parsing and configuration
+type Rules struct {
+	route *serverRoute
+}
+
+func (r *Rules) host(host string) *mux.Route {
+	return r.route.route.Host(host)
+}
+
+func (r *Rules) path(path string) *mux.Route {
+	return r.route.route.Path(path)
+}
+
+func (r *Rules) pathPrefix(path string) *mux.Route {
+	return r.route.route.PathPrefix(path)
+}
+
+func (r *Rules) pathStrip(path string) *mux.Route {
+	r.route.stripPrefix = path
+	return r.route.route.Path(path)
+}
+
+func (r *Rules) pathPrefixStrip(path string) *mux.Route {
+	r.route.stripPrefix = path
+	return r.route.route.PathPrefix(path)
+}
+
+func (r *Rules) methods(methods ...string) *mux.Route {
+	return r.route.route.Methods(methods...)
+}
+
+func (r *Rules) headers(headers ...string) *mux.Route {
+	return r.route.route.Headers(headers...)
+}
+
+func (r *Rules) headersRegexp(headers ...string) *mux.Route {
+	return r.route.route.HeadersRegexp(headers...)
+}
+
+// Parse parses rules expressions
+func (r *Rules) Parse(expression string) (*mux.Route, error) {
+	functions := map[string]interface{}{
+		"Host":            r.host,
+		"Path":            r.path,
+		"PathStrip":       r.pathStrip,
+		"PathPrefix":      r.pathPrefix,
+		"PathPrefixStrip": r.pathPrefixStrip,
+		"Methods":         r.methods,
+		"Headers":         r.headers,
+		"HeadersRegexp":   r.headersRegexp,
+	}
+	f := func(c rune) bool {
+		return c == ':' || c == '='
+	}
+	// get function
+	parsedFunctions := strings.FieldsFunc(expression, f)
+	if len(parsedFunctions) != 2 {
+		return nil, errors.New("Error parsing rule: " + expression)
+	}
+	parsedFunction, ok := functions[parsedFunctions[0]]
+	if !ok {
+		return nil, errors.New("Error parsing rule: " + expression + ". Unknow function: " + parsedFunctions[0])
+	}
+
+	fargs := func(c rune) bool {
+		return c == ',' || c == ';'
+	}
+	// get function
+	parsedArgs := strings.FieldsFunc(parsedFunctions[1], fargs)
+	if len(parsedArgs) == 0 {
+		return nil, errors.New("Error parsing args from rule: " + expression)
+	}
+
+	inputs := make([]reflect.Value, len(parsedArgs))
+	for i := range parsedArgs {
+		inputs[i] = reflect.ValueOf(parsedArgs[i])
+	}
+	method := reflect.ValueOf(parsedFunction)
+	if method.IsValid() {
+		return method.Call(inputs)[0].Interface().(*mux.Route), nil
+	}
+	return nil, errors.New("Method not found: " + parsedFunctions[0])
+}