150 lines
3.7 KiB
Go
150 lines
3.7 KiB
Go
/*
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Copyright 2016 Vulcand Authors
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package predicate
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import (
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"reflect"
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"strings"
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"github.com/gravitational/trace"
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)
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// GetStringMapValue is a helper function that returns property
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// from map[string]string or map[string][]string
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// the function returns empty value in case if key not found
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// In case if map is nil, returns empty value as well
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func GetStringMapValue(mapVal, keyVal interface{}) (interface{}, error) {
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key, ok := keyVal.(string)
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if !ok {
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return nil, trace.BadParameter("only string keys are supported")
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}
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switch m := mapVal.(type) {
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case map[string][]string:
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if len(m) == 0 {
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// to return nil with a proper type
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var n []string
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return n, nil
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}
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return m[key], nil
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case map[string]string:
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if len(m) == 0 {
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return "", nil
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}
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return m[key], nil
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default:
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return nil, trace.BadParameter("type %T is not supported", m)
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}
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}
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// BoolPredicate is a function without arguments that returns
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// boolean value when called
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type BoolPredicate func() bool
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// Equals can compare complex objects, e.g. arrays of strings
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// and strings together
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func Equals(a interface{}, b interface{}) BoolPredicate {
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return func() bool {
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switch aval := a.(type) {
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case string:
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bval, ok := b.(string)
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return ok && aval == bval
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case []string:
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bval, ok := b.([]string)
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if !ok {
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return false
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}
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if len(aval) != len(bval) {
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return false
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}
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for i := range aval {
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if aval[i] != bval[i] {
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return false
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}
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}
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return true
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default:
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return false
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}
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}
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}
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// Contains checks if string slice contains a string
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// Contains([]string{"a", "b"}, "b") -> true
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func Contains(a interface{}, b interface{}) BoolPredicate {
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return func() bool {
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aval, ok := a.([]string)
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if !ok {
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return false
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}
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bval, ok := b.(string)
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if !ok {
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return false
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}
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for _, v := range aval {
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if v == bval {
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return true
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}
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}
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return false
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}
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}
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// And is a boolean predicate that calls two boolean predicates
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// and returns result of && operation on their return values
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func And(a, b BoolPredicate) BoolPredicate {
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return func() bool {
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return a() && b()
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}
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}
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// Or is a boolean predicate that calls two boolean predicates
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// and returns result of || operation on their return values
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func Or(a, b BoolPredicate) BoolPredicate {
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return func() bool {
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return a() || b()
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}
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}
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// GetFieldByTag returns a field from the object based on the tag
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func GetFieldByTag(ival interface{}, tagName string, fieldNames []string) (interface{}, error) {
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if len(fieldNames) == 0 {
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return nil, trace.BadParameter("missing field names")
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}
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val := reflect.ValueOf(ival)
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if val.Kind() == reflect.Interface || val.Kind() == reflect.Ptr {
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val = val.Elem()
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}
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if val.Kind() != reflect.Struct {
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return nil, trace.NotFound("field name %v is not found", strings.Join(fieldNames, "."))
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}
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fieldName := fieldNames[0]
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rest := fieldNames[1:]
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valType := val.Type()
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for i := 0; i < valType.NumField(); i++ {
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tagValue := valType.Field(i).Tag.Get(tagName)
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parts := strings.Split(tagValue, ",")
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if parts[0] == fieldName {
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value := val.Field(i).Interface()
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if len(rest) == 0 {
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return value, nil
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}
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return GetFieldByTag(value, tagName, rest)
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}
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}
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return nil, trace.NotFound("field name %v is not found", strings.Join(fieldNames, "."))
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}
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