1 files changed, 369 insertions, 0 deletions
diff --git a/resources/page/pagegroup.go b/resources/page/pagegroup.go
new file mode 100644
index 000000000..46d9bd174
--- /dev/null
+++ b/resources/page/pagegroup.go
@@ -0,0 +1,369 @@
+// 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 page
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/gohugoio/hugo/common/collections"
+
+	"github.com/gohugoio/hugo/resources/resource"
+)
+
+var (
+	_ collections.Slicer = PageGroup{}
+)
+
+// PageGroup represents a group of pages, grouped by the key.
+// The key is typically a year or similar.
+type PageGroup struct {
+	Key interface{}
+	Pages
+}
+
+type mapKeyValues []reflect.Value
+
+func (v mapKeyValues) Len() int      { return len(v) }
+func (v mapKeyValues) Swap(i, j int) { v[i], v[j] = v[j], v[i] }
+
+type mapKeyByInt struct{ mapKeyValues }
+
+func (s mapKeyByInt) Less(i, j int) bool { return s.mapKeyValues[i].Int() < s.mapKeyValues[j].Int() }
+
+type mapKeyByStr struct{ mapKeyValues }
+
+func (s mapKeyByStr) Less(i, j int) bool {
+	return s.mapKeyValues[i].String() < s.mapKeyValues[j].String()
+}
+
+func sortKeys(v []reflect.Value, order string) []reflect.Value {
+	if len(v) <= 1 {
+		return v
+	}
+
+	switch v[0].Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if order == "desc" {
+			sort.Sort(sort.Reverse(mapKeyByInt{v}))
+		} else {
+			sort.Sort(mapKeyByInt{v})
+		}
+	case reflect.String:
+		if order == "desc" {
+			sort.Sort(sort.Reverse(mapKeyByStr{v}))
+		} else {
+			sort.Sort(mapKeyByStr{v})
+		}
+	}
+	return v
+}
+
+// PagesGroup represents a list of page groups.
+// This is what you get when doing page grouping in the templates.
+type PagesGroup []PageGroup
+
+// Reverse reverses the order of this list of page groups.
+func (p PagesGroup) Reverse() PagesGroup {
+	for i, j := 0, len(p)-1; i < j; i, j = i+1, j-1 {
+		p[i], p[j] = p[j], p[i]
+	}
+
+	return p
+}
+
+var (
+	errorType   = reflect.TypeOf((*error)(nil)).Elem()
+	pagePtrType = reflect.TypeOf((*Page)(nil)).Elem()
+	pagesType   = reflect.TypeOf(Pages{})
+)
+
+// GroupBy groups by the value in the given field or method name and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+func (p Pages) GroupBy(key string, order ...string) (PagesGroup, error) {
+	if len(p) < 1 {
+		return nil, nil
+	}
+
+	direction := "asc"
+
+	if len(order) > 0 && (strings.ToLower(order[0]) == "desc" || strings.ToLower(order[0]) == "rev" || strings.ToLower(order[0]) == "reverse") {
+		direction = "desc"
+	}
+
+	var ft interface{}
+	m, ok := pagePtrType.MethodByName(key)
+	if ok {
+		if m.Type.NumOut() == 0 || m.Type.NumOut() > 2 {
+			return nil, errors.New(key + " is a Page method but you can't use it with GroupBy")
+		}
+		if m.Type.NumOut() == 1 && m.Type.Out(0).Implements(errorType) {
+			return nil, errors.New(key + " is a Page method but you can't use it with GroupBy")
+		}
+		if m.Type.NumOut() == 2 && !m.Type.Out(1).Implements(errorType) {
+			return nil, errors.New(key + " is a Page method but you can't use it with GroupBy")
+		}
+		ft = m
+	} else {
+		ft, ok = pagePtrType.Elem().FieldByName(key)
+		if !ok {
+			return nil, errors.New(key + " is neither a field nor a method of Page")
+		}
+	}
+
+	var tmp reflect.Value
+	switch e := ft.(type) {
+	case reflect.StructField:
+		tmp = reflect.MakeMap(reflect.MapOf(e.Type, pagesType))
+	case reflect.Method:
+		tmp = reflect.MakeMap(reflect.MapOf(e.Type.Out(0), pagesType))
+	}
+
+	for _, e := range p {
+		ppv := reflect.ValueOf(e)
+		var fv reflect.Value
+		switch ft.(type) {
+		case reflect.StructField:
+			fv = ppv.Elem().FieldByName(key)
+		case reflect.Method:
+			fv = ppv.MethodByName(key).Call([]reflect.Value{})[0]
+		}
+		if !fv.IsValid() {
+			continue
+		}
+		if !tmp.MapIndex(fv).IsValid() {
+			tmp.SetMapIndex(fv, reflect.MakeSlice(pagesType, 0, 0))
+		}
+		tmp.SetMapIndex(fv, reflect.Append(tmp.MapIndex(fv), ppv))
+	}
+
+	sortedKeys := sortKeys(tmp.MapKeys(), direction)
+	r := make([]PageGroup, len(sortedKeys))
+	for i, k := range sortedKeys {
+		r[i] = PageGroup{Key: k.Interface(), Pages: tmp.MapIndex(k).Interface().(Pages)}
+	}
+
+	return r, nil
+}
+
+// GroupByParam groups by the given page parameter key's value and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+func (p Pages) GroupByParam(key string, order ...string) (PagesGroup, error) {
+	if len(p) < 1 {
+		return nil, nil
+	}
+
+	direction := "asc"
+
+	if len(order) > 0 && (strings.ToLower(order[0]) == "desc" || strings.ToLower(order[0]) == "rev" || strings.ToLower(order[0]) == "reverse") {
+		direction = "desc"
+	}
+
+	var tmp reflect.Value
+	var keyt reflect.Type
+	for _, e := range p {
+		param := resource.GetParamToLower(e, key)
+		if param != nil {
+			if _, ok := param.([]string); !ok {
+				keyt = reflect.TypeOf(param)
+				tmp = reflect.MakeMap(reflect.MapOf(keyt, pagesType))
+				break
+			}
+		}
+	}
+	if !tmp.IsValid() {
+		return nil, errors.New("there is no such a param")
+	}
+
+	for _, e := range p {
+		param := resource.GetParam(e, key)
+
+		if param == nil || reflect.TypeOf(param) != keyt {
+			continue
+		}
+		v := reflect.ValueOf(param)
+		if !tmp.MapIndex(v).IsValid() {
+			tmp.SetMapIndex(v, reflect.MakeSlice(pagesType, 0, 0))
+		}
+		tmp.SetMapIndex(v, reflect.Append(tmp.MapIndex(v), reflect.ValueOf(e)))
+	}
+
+	var r []PageGroup
+	for _, k := range sortKeys(tmp.MapKeys(), direction) {
+		r = append(r, PageGroup{Key: k.Interface(), Pages: tmp.MapIndex(k).Interface().(Pages)})
+	}
+
+	return r, nil
+}
+
+func (p Pages) groupByDateField(sorter func(p Pages) Pages, formatter func(p Page) string, order ...string) (PagesGroup, error) {
+	if len(p) < 1 {
+		return nil, nil
+	}
+
+	sp := sorter(p)
+
+	if !(len(order) > 0 && (strings.ToLower(order[0]) == "asc" || strings.ToLower(order[0]) == "rev" || strings.ToLower(order[0]) == "reverse")) {
+		sp = sp.Reverse()
+	}
+
+	date := formatter(sp[0].(Page))
+	var r []PageGroup
+	r = append(r, PageGroup{Key: date, Pages: make(Pages, 0)})
+	r[0].Pages = append(r[0].Pages, sp[0])
+
+	i := 0
+	for _, e := range sp[1:] {
+		date = formatter(e.(Page))
+		if r[i].Key.(string) != date {
+			r = append(r, PageGroup{Key: date})
+			i++
+		}
+		r[i].Pages = append(r[i].Pages, e)
+	}
+	return r, nil
+}
+
+// GroupByDate groups by the given page's Date value in
+// the given format and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+// For valid format strings, see https://golang.org/pkg/time/#Time.Format
+func (p Pages) GroupByDate(format string, order ...string) (PagesGroup, error) {
+	sorter := func(p Pages) Pages {
+		return p.ByDate()
+	}
+	formatter := func(p Page) string {
+		return p.Date().Format(format)
+	}
+	return p.groupByDateField(sorter, formatter, order...)
+}
+
+// GroupByPublishDate groups by the given page's PublishDate value in
+// the given format and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+// For valid format strings, see https://golang.org/pkg/time/#Time.Format
+func (p Pages) GroupByPublishDate(format string, order ...string) (PagesGroup, error) {
+	sorter := func(p Pages) Pages {
+		return p.ByPublishDate()
+	}
+	formatter := func(p Page) string {
+		return p.PublishDate().Format(format)
+	}
+	return p.groupByDateField(sorter, formatter, order...)
+}
+
+// GroupByExpiryDate groups by the given page's ExpireDate value in
+// the given format and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+// For valid format strings, see https://golang.org/pkg/time/#Time.Format
+func (p Pages) GroupByExpiryDate(format string, order ...string) (PagesGroup, error) {
+	sorter := func(p Pages) Pages {
+		return p.ByExpiryDate()
+	}
+	formatter := func(p Page) string {
+		return p.ExpiryDate().Format(format)
+	}
+	return p.groupByDateField(sorter, formatter, order...)
+}
+
+// GroupByParamDate groups by a date set as a param on the page in
+// the given format and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+// For valid format strings, see https://golang.org/pkg/time/#Time.Format
+func (p Pages) GroupByParamDate(key string, format string, order ...string) (PagesGroup, error) {
+	sorter := func(p Pages) Pages {
+		var r Pages
+		for _, e := range p {
+			param := resource.GetParamToLower(e, key)
+			if _, ok := param.(time.Time); ok {
+				r = append(r, e)
+			}
+		}
+		pdate := func(p1, p2 Page) bool {
+			p1p, p2p := p1.(Page), p2.(Page)
+			return resource.GetParamToLower(p1p, key).(time.Time).Unix() < resource.GetParamToLower(p2p, key).(time.Time).Unix()
+		}
+		pageBy(pdate).Sort(r)
+		return r
+	}
+	formatter := func(p Page) string {
+		return resource.GetParamToLower(p, key).(time.Time).Format(format)
+	}
+	return p.groupByDateField(sorter, formatter, order...)
+}
+
+// Slice is not meant to be used externally. It's a bridge function
+// for the template functions. See collections.Slice.
+func (p PageGroup) Slice(in interface{}) (interface{}, error) {
+	switch items := in.(type) {
+	case PageGroup:
+		return items, nil
+	case []interface{}:
+		groups := make(PagesGroup, len(items))
+		for i, v := range items {
+			g, ok := v.(PageGroup)
+			if !ok {
+				return nil, fmt.Errorf("type %T is not a PageGroup", v)
+			}
+			groups[i] = g
+		}
+		return groups, nil
+	default:
+		return nil, fmt.Errorf("invalid slice type %T", items)
+	}
+}
+
+// Len returns the number of pages in the page group.
+func (psg PagesGroup) Len() int {
+	l := 0
+	for _, pg := range psg {
+		l += len(pg.Pages)
+	}
+	return l
+}
+
+// ToPagesGroup tries to convert seq into a PagesGroup.
+func ToPagesGroup(seq interface{}) (PagesGroup, error) {
+	switch v := seq.(type) {
+	case nil:
+		return nil, nil
+	case PagesGroup:
+		return v, nil
+	case []PageGroup:
+		return PagesGroup(v), nil
+	case []interface{}:
+		l := len(v)
+		if l == 0 {
+			break
+		}
+		switch v[0].(type) {
+		case PageGroup:
+			pagesGroup := make(PagesGroup, l)
+			for i, ipg := range v {
+				if pg, ok := ipg.(PageGroup); ok {
+					pagesGroup[i] = pg
+				} else {
+					return nil, fmt.Errorf("unsupported type in paginate from slice, got %T instead of PageGroup", ipg)
+				}
+			}
+			return pagesGroup, nil
+		}
+	}
+
+	return nil, nil
+}