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// Copyright 2017 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 (
"context"
"errors"
"fmt"
"reflect"
"strings"
"github.com/gohugoio/hugo/common/hreflect"
"github.com/gohugoio/hugo/tpl"
)
// Apply takes a map, array, or slice and returns a new slice with the function fname applied over it.
func (ns *Namespace) Apply(ctx context.Context, seq interface{}, fname string, args ...interface{}) (interface{}, error) {
if seq == nil {
return make([]interface{}, 0), nil
}
if fname == "apply" {
return nil, errors.New("can't apply myself (no turtles allowed)")
}
seqv := reflect.ValueOf(seq)
seqv, isNil := indirect(seqv)
if isNil {
return nil, errors.New("can't iterate over a nil value")
}
fnv, found := ns.lookupFunc(fname)
if !found {
return nil, errors.New("can't find function " + fname)
}
switch seqv.Kind() {
case reflect.Array, reflect.Slice:
r := make([]interface{}, seqv.Len())
for i := 0; i < seqv.Len(); i++ {
vv := seqv.Index(i)
vvv, err := applyFnToThis(ctx, fnv, vv, args...)
if err != nil {
return nil, err
}
r[i] = vvv.Interface()
}
return r, nil
default:
return nil, fmt.Errorf("can't apply over %v", seq)
}
}
func applyFnToThis(ctx context.Context, fn, this reflect.Value, args ...interface{}) (reflect.Value, error) {
num := fn.Type().NumIn()
if num > 0 && fn.Type().In(0).Implements(hreflect.ContextInterface) {
args = append([]interface{}{ctx}, args...)
}
n := make([]reflect.Value, len(args))
for i, arg := range args {
if arg == "." {
n[i] = this
} else {
n[i] = reflect.ValueOf(arg)
}
}
if fn.Type().IsVariadic() {
num--
}
// TODO(bep) see #1098 - also see template_tests.go
/*if len(args) < num {
return reflect.ValueOf(nil), errors.New("Too few arguments")
} else if len(args) > num {
return reflect.ValueOf(nil), errors.New("Too many arguments")
}*/
for i := 0; i < num; i++ {
// AssignableTo reports whether xt is assignable to type targ.
if xt, targ := n[i].Type(), fn.Type().In(i); !xt.AssignableTo(targ) {
return reflect.ValueOf(nil), errors.New("called apply using " + xt.String() + " as type " + targ.String())
}
}
res := fn.Call(n)
if len(res) == 1 || res[1].IsNil() {
return res[0], nil
}
return reflect.ValueOf(nil), res[1].Interface().(error)
}
func (ns *Namespace) lookupFunc(fname string) (reflect.Value, bool) {
if !strings.ContainsRune(fname, '.') {
templ := ns.deps.Tmpl().(tpl.TemplateFuncGetter)
return templ.GetFunc(fname)
}
ss := strings.SplitN(fname, ".", 2)
// Namespace
nv, found := ns.lookupFunc(ss[0])
if !found {
return reflect.Value{}, false
}
fn, ok := nv.Interface().(func(...interface{}) (interface{}, error))
if !ok {
return reflect.Value{}, false
}
v, err := fn()
if err != nil {
panic(err)
}
nv = reflect.ValueOf(v)
// method
m := hreflect.GetMethodByName(nv, ss[1])
if m.Kind() == reflect.Invalid {
return reflect.Value{}, false
}
return m, true
}
// indirect is borrowed from the Go stdlib: 'text/template/exec.go'
func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
if v.IsNil() {
return v, true
}
if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
break
}
}
return v, false
}
func indirectInterface(v reflect.Value) (rv reflect.Value, isNil bool) {
for ; v.Kind() == reflect.Interface; v = v.Elem() {
if v.IsNil() {
return v, true
}
if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
break
}
}
return v, false
}
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