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// Copyright 2019 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package collections
import (
"reflect"
"strings"
"github.com/gohugoio/hugo/common/hreflect"
"github.com/gohugoio/hugo/common/maps"
"github.com/pkg/errors"
)
// Merge creates a copy of the final parameter and merges the preceding
// parameters into it in reverse order.
// Currently only maps are supported. Key handling is case insensitive.
func (ns *Namespace) Merge(params ...interface{}) (interface{}, error) {
if len(params) < 2 {
return nil, errors.New("merge requires at least two parameters")
}
var err error
result := params[len(params)-1]
for i := len(params) - 2; i >= 0; i-- {
result, err = ns.merge(params[i], result)
if err != nil {
return nil, err
}
}
return result, nil
}
// merge creates a copy of dst and merges src into it.
func (ns *Namespace) merge(src, dst interface{}) (interface{}, error) {
vdst, vsrc := reflect.ValueOf(dst), reflect.ValueOf(src)
if vdst.Kind() != reflect.Map {
return nil, errors.Errorf("destination must be a map, got %T", dst)
}
if !hreflect.IsTruthfulValue(vsrc) {
return dst, nil
}
if vsrc.Kind() != reflect.Map {
return nil, errors.Errorf("source must be a map, got %T", src)
}
if vsrc.Type().Key() != vdst.Type().Key() {
return nil, errors.Errorf("incompatible map types, got %T to %T", src, dst)
}
return mergeMap(vdst, vsrc).Interface(), nil
}
func caseInsensitiveLookup(m, k reflect.Value) (reflect.Value, bool) {
if m.Type().Key().Kind() != reflect.String || k.Kind() != reflect.String {
// Fall back to direct lookup.
v := m.MapIndex(k)
return v, hreflect.IsTruthfulValue(v)
}
for _, key := range m.MapKeys() {
if strings.EqualFold(k.String(), key.String()) {
return m.MapIndex(key), true
}
}
return reflect.Value{}, false
}
func mergeMap(dst, src reflect.Value) reflect.Value {
out := reflect.MakeMap(dst.Type())
// If the destination is Params, we must lower case all keys.
_, lowerCase := dst.Interface().(maps.Params)
// Copy the destination map.
for _, key := range dst.MapKeys() {
v := dst.MapIndex(key)
out.SetMapIndex(key, v)
}
// Add all keys in src not already in destination.
// Maps of the same type will be merged.
for _, key := range src.MapKeys() {
sv := src.MapIndex(key)
dv, found := caseInsensitiveLookup(dst, key)
if found {
// If both are the same map key type, merge.
dve := dv.Elem()
if dve.Kind() == reflect.Map {
sve := sv.Elem()
if sve.Kind() != reflect.Map {
continue
}
if dve.Type().Key() == sve.Type().Key() {
out.SetMapIndex(key, mergeMap(dve, sve))
}
}
} else {
if lowerCase && key.Kind() == reflect.String {
key = reflect.ValueOf(strings.ToLower(key.String()))
}
out.SetMapIndex(key, sv)
}
}
return out
}
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