github.com/graemephi/kahugo@v0.62.3-0.20211121071557-d78c0423784d/tpl/collections/symdiff.go (about)

     1  // Copyright 2018 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package collections
    15  
    16  import (
    17  	"fmt"
    18  	"reflect"
    19  
    20  	"github.com/pkg/errors"
    21  )
    22  
    23  // SymDiff returns the symmetric difference of s1 and s2.
    24  // Arguments must be either a slice or an array of comparable types.
    25  func (ns *Namespace) SymDiff(s2, s1 interface{}) (interface{}, error) {
    26  	ids1, err := collectIdentities(s1)
    27  	if err != nil {
    28  		return nil, err
    29  	}
    30  	ids2, err := collectIdentities(s2)
    31  	if err != nil {
    32  		return nil, err
    33  	}
    34  
    35  	var slice reflect.Value
    36  	var sliceElemType reflect.Type
    37  
    38  	for i, s := range []interface{}{s1, s2} {
    39  		v := reflect.ValueOf(s)
    40  
    41  		switch v.Kind() {
    42  		case reflect.Array, reflect.Slice:
    43  			if i == 0 {
    44  				sliceType := v.Type()
    45  				sliceElemType = sliceType.Elem()
    46  				slice = reflect.MakeSlice(sliceType, 0, 0)
    47  			}
    48  
    49  			for i := 0; i < v.Len(); i++ {
    50  				ev, _ := indirectInterface(v.Index(i))
    51  				key := normalize(ev)
    52  
    53  				// Append if the key is not in their intersection.
    54  				if ids1[key] != ids2[key] {
    55  					v, err := convertValue(ev, sliceElemType)
    56  					if err != nil {
    57  						return nil, errors.WithMessage(err, "symdiff: failed to convert value")
    58  					}
    59  					slice = reflect.Append(slice, v)
    60  				}
    61  			}
    62  		default:
    63  			return nil, fmt.Errorf("arguments to symdiff must be slices or arrays")
    64  		}
    65  	}
    66  
    67  	return slice.Interface(), nil
    68  }