Add basic "post resource publish support"

Fixes #7146

resources/postpub/postpub.go

@@ -0,0 +1,177 @@
+// Copyright 2020 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 postpub
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+
+	"github.com/spf13/cast"
+
+	"github.com/gohugoio/hugo/common/maps"
+	"github.com/gohugoio/hugo/media"
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+type PostPublishedResource interface {
+	resource.ResourceTypeProvider
+	resource.ResourceLinksProvider
+	resource.ResourceMetaProvider
+	resource.ResourceParamsProvider
+	resource.ResourceDataProvider
+	resource.OriginProvider
+
+	MediaType() map[string]interface{}
+}
+
+const (
+	PostProcessPrefix = "__h_pp_l1"
+	PostProcessSuffix = "__e"
+)
+
+func NewPostPublishResource(id int, r resource.Resource) PostPublishedResource {
+	return &PostPublishResource{
+		prefix:   PostProcessPrefix + "_" + strconv.Itoa(id) + "_",
+		delegate: r,
+	}
+}
+
+// postPublishResource holds a Resource to be transformed post publishing.
+type PostPublishResource struct {
+	prefix   string
+	delegate resource.Resource
+}
+
+func (r *PostPublishResource) field(name string) string {
+	return r.prefix + name + PostProcessSuffix
+}
+
+func (r *PostPublishResource) Permalink() string {
+	return r.field("Permalink")
+}
+
+func (r *PostPublishResource) RelPermalink() string {
+	return r.field("RelPermalink")
+}
+
+func (r *PostPublishResource) Origin() resource.Resource {
+	return r.delegate
+}
+
+func (r *PostPublishResource) GetFieldString(pattern string) (string, bool) {
+	if r == nil {
+		panic("resource is nil")
+	}
+	prefixIdx := strings.Index(pattern, r.prefix)
+	if prefixIdx == -1 {
+		// Not a method on this resource.
+		return "", false
+	}
+
+	fieldAccessor := pattern[prefixIdx+len(r.prefix) : strings.Index(pattern, PostProcessSuffix)]
+
+	d := r.delegate
+	switch {
+	case fieldAccessor == "RelPermalink":
+		return d.RelPermalink(), true
+	case fieldAccessor == "Permalink":
+		return d.Permalink(), true
+	case fieldAccessor == "Name":
+		return d.Name(), true
+	case fieldAccessor == "Title":
+		return d.Title(), true
+	case fieldAccessor == "ResourceType":
+		return d.ResourceType(), true
+	case fieldAccessor == "Content":
+		content, err := d.(resource.ContentProvider).Content()
+		if err != nil {
+			return "", true
+		}
+		return cast.ToString(content), true
+	case strings.HasPrefix(fieldAccessor, "MediaType"):
+		return r.fieldToString(d.MediaType(), fieldAccessor), true
+	case fieldAccessor == "Data.Integrity":
+		return cast.ToString((d.Data().(map[string]interface{})["Integrity"])), true
+	default:
+		panic(fmt.Sprintf("unknown field accessor %q", fieldAccessor))
+	}
+
+}
+
+func (r *PostPublishResource) fieldToString(receiver interface{}, path string) string {
+	fieldname := strings.Split(path, ".")[1]
+
+	receiverv := reflect.ValueOf(receiver)
+	switch receiverv.Kind() {
+	case reflect.Map:
+		v := receiverv.MapIndex(reflect.ValueOf(fieldname))
+		return cast.ToString(v.Interface())
+	default:
+		v := receiverv.FieldByName(fieldname)
+		if !v.IsValid() {
+			method := receiverv.MethodByName(fieldname)
+			if method.IsValid() {
+				vals := method.Call(nil)
+				if len(vals) > 0 {
+					v = vals[0]
+				}
+
+			}
+		}
+
+		if v.IsValid() {
+			return cast.ToString(v.Interface())
+		}
+		return ""
+	}
+}
+
+func (r *PostPublishResource) Data() interface{} {
+	m := map[string]interface{}{
+		"Integrity": "",
+	}
+	insertFieldPlaceholders("Data", m, r.field)
+	return m
+}
+
+func (r *PostPublishResource) MediaType() map[string]interface{} {
+	m := structToMapWithPlaceholders("MediaType", media.Type{}, r.field)
+	return m
+}
+
+func (r *PostPublishResource) ResourceType() string {
+	return r.field("ResourceType")
+}
+
+func (r *PostPublishResource) Name() string {
+	return r.field("Name")
+}
+
+func (r *PostPublishResource) Title() string {
+	return r.field("Title")
+}
+
+func (r *PostPublishResource) Params() maps.Params {
+	panic(r.fieldNotSupported("Params"))
+}
+
+func (r *PostPublishResource) Content() (interface{}, error) {
+	return r.field("Content"), nil
+}
+
+func (r *PostPublishResource) fieldNotSupported(name string) string {
+	return fmt.Sprintf("method .%s is currently not supported in post-publish transformations.", name)
+}