Make Page an interface

The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue  #5074, "pages from other data sources".

But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.

Most notable changes:

* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
  This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
  This improves the taxonomy template `.Title` situation and make common template constructs much simpler.

See #5074
Fixes #5763
Fixes #5758
Fixes #5090
Fixes #5204
Fixes #4695
Fixes #5607
Fixes #5707
Fixes #5719
Fixes #3113
Fixes #5706
Fixes #5767
Fixes #5723
Fixes #5769
Fixes #5770
Fixes #5771
Fixes #5759
Fixes #5776
Fixes #5777
Fixes #5778

1 files changed, 553 insertions, 1807 deletions

diff --git a/hugolib/page.go b/hugolib/page.go
index 71070d1e8..24d659fb1 100644
--- a/hugolib/page.go
+++ b/hugolib/page.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// 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.
@@ -15,2012 +15,836 @@ package hugolib
 
 import (
 	"bytes"
-	"context"
-	"errors"
 	"fmt"
-	"math/rand"
-	"reflect"
-
-	"github.com/gohugoio/hugo/common/hugo"
-
-	"github.com/gohugoio/hugo/common/maps"
-	"github.com/gohugoio/hugo/common/urls"
-	"github.com/gohugoio/hugo/media"
-
-	"github.com/gohugoio/hugo/langs"
-
-	"github.com/gohugoio/hugo/related"
-
-	"github.com/bep/gitmap"
-
-	"github.com/gohugoio/hugo/helpers"
-	"github.com/gohugoio/hugo/hugolib/pagemeta"
-	"github.com/gohugoio/hugo/resources/resource"
-
-	"github.com/gohugoio/hugo/output"
-	"github.com/mitchellh/mapstructure"
-
 	"html/template"
-	"io"
+	"os"
 	"path"
 	"path/filepath"
-	"regexp"
 	"runtime"
+	"sort"
 	"strings"
-	"sync"
-	"time"
-	"unicode/utf8"
 
-	"github.com/gohugoio/hugo/compare"
-	"github.com/gohugoio/hugo/source"
+	"github.com/bep/gitmap"
 	"github.com/spf13/cast"
-)
 
-var (
-	cjk = regexp.MustCompile(`\p{Han}|\p{Hangul}|\p{Hiragana}|\p{Katakana}`)
+	"github.com/gohugoio/hugo/helpers"
 
-	// This is all the kinds we can expect to find in .Site.Pages.
-	allKindsInPages = []string{KindPage, KindHome, KindSection, KindTaxonomy, KindTaxonomyTerm}
+	"github.com/gohugoio/hugo/common/herrors"
+	"github.com/gohugoio/hugo/parser/metadecoders"
 
-	allKinds = append(allKindsInPages, []string{kindRSS, kindSitemap, kindRobotsTXT, kind404}...)
+	"github.com/gohugoio/hugo/parser/pageparser"
+	"github.com/pkg/errors"
 
-	// Assert that it implements the Eqer interface.
-	_ compare.Eqer = (*Page)(nil)
-	_ compare.Eqer = (*PageOutput)(nil)
+	"github.com/gohugoio/hugo/output"
 
-	// Assert that it implements the interface needed for related searches.
-	_ related.Document = (*Page)(nil)
+	"github.com/gohugoio/hugo/media"
+	"github.com/gohugoio/hugo/source"
 
-	// Page supports ref and relref
-	_ urls.RefLinker = (*Page)(nil)
+	"github.com/gohugoio/hugo/common/collections"
+	"github.com/gohugoio/hugo/common/text"
+	"github.com/gohugoio/hugo/resources"
+	"github.com/gohugoio/hugo/resources/page"
+	"github.com/gohugoio/hugo/resources/resource"
 )
 
-// Wraps a Page.
-type pageContainer interface {
-	page() *Page
-}
-
-const (
-	KindPage = "page"
-
-	// The rest are node types; home page, sections etc.
-
-	KindHome         = "home"
-	KindSection      = "section"
-	KindTaxonomy     = "taxonomy"
-	KindTaxonomyTerm = "taxonomyTerm"
-
-	// Temporary state.
-	kindUnknown = "unknown"
-
-	// The following are (currently) temporary nodes,
-	// i.e. nodes we create just to render in isolation.
-	kindRSS       = "RSS"
-	kindSitemap   = "sitemap"
-	kindRobotsTXT = "robotsTXT"
-	kind404       = "404"
-
-	pageResourceType = "page"
+var (
+	_ page.Page           = (*pageState)(nil)
+	_ collections.Grouper = (*pageState)(nil)
+	_ collections.Slicer  = (*pageState)(nil)
 )
 
-type Page struct {
-	*pageInit
-	*pageContentInit
-
-	// Kind is the discriminator that identifies the different page types
-	// in the different page collections. This can, as an example, be used
-	// to to filter regular pages, find sections etc.
-	// Kind will, for the pages available to the templates, be one of:
-	// page, home, section, taxonomy and taxonomyTerm.
-	// It is of string type to make it easy to reason about in
-	// the templates.
-	Kind string
-
-	// Since Hugo 0.18 we got rid of the Node type. So now all pages are ...
-	// pages (regular pages, home page, sections etc.).
-	// Sections etc. will have child pages. These were earlier placed in .Data.Pages,
-	// but can now be more intuitively also be fetched directly from .Pages.
-	// This collection will be nil for regular pages.
-	Pages Pages
-
-	// Since Hugo 0.32, a Page can have resources such as images and CSS associated
-	// with itself. The resource will typically be placed relative to the Page,
-	// but templates should use the links (Permalink and RelPermalink)
-	// provided by the Resource object.
-	Resources resource.Resources
-
-	// This is the raw front matter metadata that is going to be assigned to
-	// the Resources above.
-	resourcesMetadata []map[string]interface{}
-
-	// translations will contain references to this page in other language
-	// if available.
-	translations Pages
-
-	// A key that maps to translation(s) of this page. This value is fetched
-	// from the page front matter.
-	translationKey string
-
-	// Params contains configuration defined in the params section of page frontmatter.
-	params map[string]interface{}
-
-	// Content sections
-	contentv        template.HTML
-	summary         template.HTML
-	TableOfContents template.HTML
-
-	// Passed to the shortcodes
-	pageWithoutContent *PageWithoutContent
-
-	Aliases []string
-
-	Images []Image
-	Videos []Video
-
-	truncated bool
-	Draft     bool
-	Status    string
-
-	// PageMeta contains page stats such as word count etc.
-	PageMeta
-
-	// Markup contains the markup type for the content.
-	Markup string
-
-	extension   string
-	contentType string
-
-	Layout string
-
-	// For npn-renderable pages (see IsRenderable), the content itself
-	// is used as template and the template name is stored here.
-	selfLayout string
-
-	linkTitle string
-
-	// Content items.
-	pageContent
-
-	// whether the content is in a CJK language.
-	isCJKLanguage bool
-
-	// the content stripped for HTML
-	plain      string // TODO should be []byte
-	plainWords []string
-
-	// rendering configuration
-	renderingConfig *helpers.BlackFriday
-
-	// menus
-	pageMenus PageMenus
-
-	source.File
-
-	Position `json:"-"`
-
-	GitInfo *gitmap.GitInfo
-
-	// This was added as part of getting the Nodes (taxonomies etc.) to work as
-	// Pages in Hugo 0.18.
-	// It is deliberately named similar to Section, but not exported (for now).
-	// We currently have only one level of section in Hugo, but the page can live
-	// any number of levels down the file path.
-	// To support taxonomies like /categories/hugo etc. we will need to keep track
-	// of that information in a general way.
-	// So, sections represents the path to the content, i.e. a content file or a
-	// virtual content file in the situations where a taxonomy or a section etc.
-	// isn't accomanied by one.
-	sections []string
-
-	// Will only be set for sections and regular pages.
-	parent *Page
-
-	// When we create paginator pages, we create a copy of the original,
-	// but keep track of it here.
-	origOnCopy *Page
-
-	// Will only be set for section pages and the home page.
-	subSections Pages
-
-	s *Site
-
-	// Pulled over from old Node. TODO(bep) reorg and group (embed)
-
-	Site *SiteInfo `json:"-"`
-
-	title       string
-	Description string
-	Keywords    []string
-	data        map[string]interface{}
-
-	pagemeta.PageDates
-
-	Sitemap Sitemap
-	pagemeta.URLPath
-	frontMatterURL string
-
-	permalink    string
-	relPermalink string
-
-	// relative target path without extension and any base path element
-	// from the baseURL or the language code.
-	// This is used to construct paths in the page resources.
-	relTargetPathBase string
-	// Is set to a forward slashed path if this is a Page resources living in a folder below its owner.
-	resourcePath string
-
-	// This is enabled if it is a leaf bundle (the "index.md" type) and it is marked as headless in front matter.
-	// Being headless means that
-	// 1. The page itself is not rendered to disk
-	// 2. It is not available in .Site.Pages etc.
-	// 3. But you can get it via .Site.GetPage
-	headless bool
-
-	layoutDescriptor output.LayoutDescriptor
-
-	scratch *maps.Scratch
-
-	// It would be tempting to use the language set on the Site, but in they way we do
-	// multi-site processing, these values may differ during the initial page processing.
-	language *langs.Language
-
-	lang string
-
-	// When in Fast Render Mode, we only render a sub set of the pages, i.e. the
-	// pages the user is working on. There are, however, situations where we need to
-	// signal other pages to be rendered.
-	forceRender bool
-
-	// The output formats this page will be rendered to.
-	outputFormats output.Formats
-
-	// This is the PageOutput that represents the first item in outputFormats.
-	// Use with care, as there are potential for inifinite loops.
-	mainPageOutput *PageOutput
-
-	targetPathDescriptorPrototype *targetPathDescriptor
-}
-
-func stackTrace(length int) string {
-	trace := make([]byte, length)
-	runtime.Stack(trace, true)
-	return string(trace)
-}
-
-func (p *Page) Data() interface{} {
-	return p.data
-}
-
-func (p *Page) initContent() {
-
-	p.contentInit.Do(func() {
-		// This careful dance is here to protect against circular loops in shortcode/content
-		// constructs.
-		// TODO(bep) context vs the remote shortcodes
-		ctx, cancel := context.WithTimeout(context.Background(), p.s.Timeout)
-		defer cancel()
-		c := make(chan error, 1)
-
-		p.contentInitMu.Lock()
-		defer p.contentInitMu.Unlock()
-
-		go func() {
-			var err error
-
-			err = p.prepareContent()
-			if err != nil {
-				c <- err
-				return
-			}
-
-			select {
-			case <-ctx.Done():
-				return
-			default:
-			}
-
-			if len(p.summary) == 0 {
-				if err = p.setAutoSummary(); err != nil {
-					err = p.errorf(err, "failed to set auto summary")
-				}
-			}
-			c <- err
-		}()
-
-		select {
-		case <-ctx.Done():
-			p.s.Log.WARN.Printf("Timed out creating content for page %q (.Content will be empty). This is most likely a circular shortcode content loop that should be fixed. If this is just a shortcode calling a slow remote service, try to set \"timeout=30000\" (or higher, value is in milliseconds) in config.toml.\n", p.pathOrTitle())
-		case err := <-c:
-			if err != nil {
-				p.s.SendError(err)
-			}
-		}
-	})
-
-}
-
-// This is sent to the shortcodes for this page. Not doing that will create an infinite regress. So,
-// shortcodes can access .Page.TableOfContents, but not .Page.Content etc.
-func (p *Page) withoutContent() *PageWithoutContent {
-	p.pageInit.withoutContentInit.Do(func() {
-		p.pageWithoutContent = &PageWithoutContent{Page: p}
-	})
-	return p.pageWithoutContent
-}
-
-func (p *Page) Content() (interface{}, error) {
-	return p.content(), nil
-}
-
-func (p *Page) Truncated() bool {
-	p.initContent()
-	return p.truncated
-}
-
-func (p *Page) content() template.HTML {
-	p.initContent()
-	return p.contentv
-}
-
-func (p *Page) Summary() template.HTML {
-	p.initContent()
-	return p.summary
-}
-
-// Sites is a convenience method to get all the Hugo sites/languages configured.
-func (p *Page) Sites() SiteInfos {
-	return p.s.owner.siteInfos()
-}
-
-// SearchKeywords implements the related.Document interface needed for fast page searches.
-func (p *Page) SearchKeywords(cfg related.IndexConfig) ([]related.Keyword, error) {
-
-	v, err := p.Param(cfg.Name)
-	if err != nil {
-		return nil, err
-	}
+var (
+	pageTypesProvider = resource.NewResourceTypesProvider(media.OctetType, pageResourceType)
+	nopPageOutput     = &pageOutput{pagePerOutputProviders: nopPagePerOutput}
+)
 
-	return cfg.ToKeywords(v)
+// pageContext provides contextual information about this page, for error
+// logging and similar.
+type pageContext interface {
+	posOffset(offset int) text.Position
+	wrapError(err error) error
+	getRenderingConfig() *helpers.BlackFriday
 }
 
-// PubDate is when this page was or will be published.
-// NOTE: This is currently used for search only and is not meant to be used
-// directly in templates. We need to consolidate the dates in this struct.
-// TODO(bep) see https://github.com/gohugoio/hugo/issues/3854
-func (p *Page) PubDate() time.Time {
-	if !p.PublishDate.IsZero() {
-		return p.PublishDate
+// wrapErr adds some context to the given error if possible.
+func wrapErr(err error, ctx interface{}) error {
+	if pc, ok := ctx.(pageContext); ok {
+		return pc.wrapError(err)
 	}
-	return p.Date
+	return err
 }
 
-func (*Page) ResourceType() string {
-	return pageResourceType
-}
-
-func (p *Page) RSSLink() template.URL {
-	f, found := p.outputFormats.GetByName(output.RSSFormat.Name)
-	if !found {
-		return ""
-	}
-	return template.URL(newOutputFormat(p, f).Permalink())
+type pageSiteAdapter struct {
+	p page.Page
+	s *Site
 }
 
-func (p *Page) createLayoutDescriptor() output.LayoutDescriptor {
-	var section string
-
-	switch p.Kind {
-	case KindSection:
-		// In Hugo 0.22 we introduce nested sections, but we still only
-		// use the first level to pick the correct template. This may change in
-		// the future.
-		section = p.sections[0]
-	case KindTaxonomy, KindTaxonomyTerm:
-		section = p.s.taxonomiesPluralSingular[p.sections[0]]
-	default:
-	}
-
-	return output.LayoutDescriptor{
-		Kind:    p.Kind,
-		Type:    p.Type(),
-		Lang:    p.Lang(),
-		Layout:  p.Layout,
-		Section: section,
+func (pa pageSiteAdapter) GetPage(ref string) (page.Page, error) {
+	p, err := pa.s.getPageNew(pa.p, ref)
+	if p == nil {
+		// The nil struct has meaning in some situations, mostly to avoid breaking
+		// existing sites doing $nilpage.IsDescendant($p), which will always return
+		// false.
+		p = page.NilPage
 	}
+	return p, err
 }
 
-// pageInit lazy initializes different parts of the page. It is extracted
-// into its own type so we can easily create a copy of a given page.
-type pageInit struct {
-	languageInit        sync.Once
-	pageMenusInit       sync.Once
-	pageMetaInit        sync.Once
-	renderingConfigInit sync.Once
-	withoutContentInit  sync.Once
-}
+type pageState struct {
+	// This slice will be of same length as the number of global slice of output
+	// formats (for all sites).
+	pageOutputs []*pageOutput
 
-type pageContentInit struct {
-	contentInitMu  sync.Mutex
-	contentInit    sync.Once
-	plainInit      sync.Once
-	plainWordsInit sync.Once
-}
+	// This will be shifted out when we start to render a new output format.
+	*pageOutput
 
-func (p *Page) resetContent() {
-	p.pageContentInit = &pageContentInit{}
+	// Common for all output formats.
+	*pageCommon
 }
 
-// IsNode returns whether this is an item of one of the list types in Hugo,
-// i.e. not a regular content page.
-func (p *Page) IsNode() bool {
-	return p.Kind != KindPage
-}
+// Eq returns whether the current page equals the given page.
+// This is what's invoked when doing `{{ if eq $page $otherPage }}`
+func (p *pageState) Eq(other interface{}) bool {
+	pp, err := unwrapPage(other)
+	if err != nil {
+		return false
+	}
 
-// IsHome returns whether this is the home page.
-func (p *Page) IsHome() bool {
-	return p.Kind == KindHome
+	return p == pp
 }
 
-// IsSection returns whether this is a section page.
-func (p *Page) IsSection() bool {
-	return p.Kind == KindSection
+func (p *pageState) GitInfo() *gitmap.GitInfo {
+	return p.gitInfo
 }
 
-// IsPage returns whether this is a regular content page.
-func (p *Page) IsPage() bool {
-	return p.Kind == KindPage
+func (p *pageState) MarshalJSON() ([]byte, error) {
+	return page.MarshalPageToJSON(p)
 }
 
-// BundleType returns the bundle type: "leaf", "branch" or an empty string if it is none.
-// See https://gohugo.io/content-management/page-bundles/
-func (p *Page) BundleType() string {
-	if p.IsNode() {
-		return "branch"
-	}
-
-	var source interface{} = p.File
-	if fi, ok := source.(*fileInfo); ok {
-		switch fi.bundleTp {
-		case bundleBranch:
-			return "branch"
-		case bundleLeaf:
-			return "leaf"
+func (p *pageState) Pages() page.Pages {
+	p.pagesInit.Do(func() {
+		if p.pages != nil {
+			return
 		}
-	}
-
-	return ""
-}
 
-func (p *Page) MediaType() media.Type {
-	return media.OctetType
-}
+		var pages page.Pages
 
-type PageMeta struct {
-	wordCount      int
-	fuzzyWordCount int
-	readingTime    int
-	Weight         int
-}
-
-type Position struct {
-	PrevPage      *Page
-	NextPage      *Page
-	PrevInSection *Page
-	NextInSection *Page
-}
+		switch p.Kind() {
+		case page.KindPage:
+		case page.KindHome:
+			pages = p.s.RegularPages()
+		case page.KindTaxonomy:
+			termInfo := p.getTaxonomyNodeInfo()
+			taxonomy := p.s.Taxonomies[termInfo.plural].Get(termInfo.termKey)
+			pages = taxonomy.Pages()
+		case page.KindTaxonomyTerm:
+			plural := p.getTaxonomyNodeInfo().plural
+			// A list of all page.KindTaxonomy pages with matching plural
+			for _, p := range p.s.findPagesByKind(page.KindTaxonomy) {
+				if p.SectionsEntries()[0] == plural {
+					pages = append(pages, p)
+				}
+			}
+		case kind404, kindSitemap, kindRobotsTXT:
+			pages = p.s.Pages()
+		}
 
-type Pages []*Page
+		p.pages = pages
+	})
 
-func (ps Pages) String() string {
-	return fmt.Sprintf("Pages(%d)", len(ps))
+	return p.pages
 }
 
-// Used in tests.
-func (ps Pages) shuffle() {
-	for i := range ps {
-		j := rand.Intn(i + 1)
-		ps[i], ps[j] = ps[j], ps[i]
+// RawContent returns the un-rendered source content without
+// any leading front matter.
+func (p *pageState) RawContent() string {
+	if p.source.parsed == nil {
+		return ""
 	}
-}
-
-func (ps Pages) findPagePosByFilename(filename string) int {
-	for i, x := range ps {
-		if x.Filename() == filename {
-			return i
-		}
+	start := p.source.posMainContent
+	if start == -1 {
+		start = 0
 	}
-	return -1
+	return string(p.source.parsed.Input()[start:])
 }
 
-func (ps Pages) removeFirstIfFound(p *Page) Pages {
-	ii := -1
-	for i, pp := range ps {
-		if pp == p {
-			ii = i
-			break
-		}
-	}
+func (p *pageState) Resources() resource.Resources {
+	p.resourcesInit.Do(func() {
 
-	if ii != -1 {
-		ps = append(ps[:ii], ps[ii+1:]...)
-	}
-	return ps
-}
+		sort := func() {
+			sort.SliceStable(p.resources, func(i, j int) bool {
+				ri, rj := p.resources[i], p.resources[j]
+				if ri.ResourceType() < rj.ResourceType() {
+					return true
+				}
 
-func (ps Pages) findPagePosByFilnamePrefix(prefix string) int {
-	if prefix == "" {
-		return -1
-	}
+				p1, ok1 := ri.(page.Page)
+				p2, ok2 := rj.(page.Page)
 
-	lenDiff := -1
-	currPos := -1
-	prefixLen := len(prefix)
+				if ok1 != ok2 {
+					return ok2
+				}
 
-	// Find the closest match
-	for i, x := range ps {
-		if strings.HasPrefix(x.Filename(), prefix) {
-			diff := len(x.Filename()) - prefixLen
-			if lenDiff == -1 || diff < lenDiff {
-				lenDiff = diff
-				currPos = i
-			}
-		}
-	}
-	return currPos
-}
+				if ok1 {
+					return page.DefaultPageSort(p1, p2)
+				}
 
-// findPagePos Given a page, it will find the position in Pages
-// will return -1 if not found
-func (ps Pages) findPagePos(page *Page) int {
-	for i, x := range ps {
-		if x.Filename() == page.Filename() {
-			return i
+				return ri.RelPermalink() < rj.RelPermalink()
+			})
 		}
-	}
-	return -1
-}
 
-func (p *Page) Plain() string {
-	p.initContent()
-	p.initPlain(true)
-	return p.plain
-}
+		sort()
 
-func (p *Page) initPlain(lock bool) {
-	p.plainInit.Do(func() {
-		if lock {
-			p.contentInitMu.Lock()
-			defer p.contentInitMu.Unlock()
+		if len(p.m.resourcesMetadata) > 0 {
+			resources.AssignMetadata(p.m.resourcesMetadata, p.resources...)
+			sort()
 		}
-		p.plain = helpers.StripHTML(string(p.contentv))
-	})
-}
-
-func (p *Page) PlainWords() []string {
-	p.initContent()
-	p.initPlainWords(true)
-	return p.plainWords
-}
 
-func (p *Page) initPlainWords(lock bool) {
-	p.plainWordsInit.Do(func() {
-		if lock {
-			p.contentInitMu.Lock()
-			defer p.contentInitMu.Unlock()
-		}
-		p.plainWords = strings.Fields(p.plain)
 	})
+	return p.resources
 }
 
-// Param is a convenience method to do lookups in Page's and Site's Params map,
-// in that order.
-//
-// This method is also implemented on Node and SiteInfo.
-func (p *Page) Param(key interface{}) (interface{}, error) {
-	keyStr, err := cast.ToStringE(key)
-	if err != nil {
-		return nil, err
-	}
-
-	keyStr = strings.ToLower(keyStr)
-	result, _ := p.traverseDirect(keyStr)
-	if result != nil {
-		return result, nil
-	}
-
-	keySegments := strings.Split(keyStr, ".")
-	if len(keySegments) == 1 {
-		return nil, nil
-	}
-
-	return p.traverseNested(keySegments)
-}
-
-func (p *Page) traverseDirect(key string) (interface{}, error) {
-	keyStr := strings.ToLower(key)
-	if val, ok := p.params[keyStr]; ok {
-		return val, nil
+func (p *pageState) HasShortcode(name string) bool {
+	if p.shortcodeState == nil {
+		return false
 	}
 
-	return p.Site.Params[keyStr], nil
+	return p.shortcodeState.nameSet[name]
 }
 
-func (p *Page) traverseNested(keySegments []string) (interface{}, error) {
-	result := traverse(keySegments, p.params)
-	if result != nil {
-		return result, nil
-	}
-
-	result = traverse(keySegments, p.Site.Params)
-	if result != nil {
-		return result, nil
-	}
-
-	// Didn't find anything, but also no problems.
-	return nil, nil
+func (p *pageState) Site() page.Site {
+	return &p.s.Info
 }
 
-func traverse(keys []string, m map[string]interface{}) interface{} {
-	// Shift first element off.
-	firstKey, rest := keys[0], keys[1:]
-	result := m[firstKey]
-
-	// No point in continuing here.
-	if result == nil {
-		return result
-	}
-
-	if len(rest) == 0 {
-		// That was the last key.
-		return result
+func (p *pageState) String() string {
+	if sourceRef := p.sourceRef(); sourceRef != "" {
+		return fmt.Sprintf("Page(%s)", sourceRef)
 	}
-
-	// That was not the last key.
-	return traverse(rest, cast.ToStringMap(result))
+	return fmt.Sprintf("Page(%q)", p.Title())
 }
 
-func (p *Page) Author() Author {
-	authors := p.Authors()
-
-	for _, author := range authors {
-		return author
-	}
-	return Author{}
+// IsTranslated returns whether this content file is translated to
+// other language(s).
+func (p *pageState) IsTranslated() bool {
+	p.s.h.init.translations.Do()
+	return len(p.translations) > 0
 }
 
-func (p *Page) Authors() AuthorList {
-	authorKeys, ok := p.params["authors"]
-	if !ok {
-		return AuthorList{}
-	}
-	authors := authorKeys.([]string)
-	if len(authors) < 1 || len(p.Site.Authors) < 1 {
-		return AuthorList{}
-	}
-
-	al := make(AuthorList)
-	for _, author := range authors {
-		a, ok := p.Site.Authors[author]
-		if ok {
-			al[author] = a
+// TranslationKey returns the key used to map language translations of this page.
+// It will use the translationKey set in front matter if set, or the content path and
+// filename (excluding any language code and extension), e.g. "about/index".
+// The Page Kind is always prepended.
+func (p *pageState) TranslationKey() string {
+	p.translationKeyInit.Do(func() {
+		if p.m.translationKey != "" {
+			p.translationKey = p.Kind() + "/" + p.m.translationKey
+		} else if p.IsPage() && p.File() != nil {
+			p.translationKey = path.Join(p.Kind(), filepath.ToSlash(p.File().Dir()), p.File().TranslationBaseName())
+		} else if p.IsNode() {
+			p.translationKey = path.Join(p.Kind(), p.SectionsPath())
 		}
-	}
-	return al
-}
 
-func (p *Page) UniqueID() string {
-	return p.File.UniqueID()
-}
-
-// Returns the page as summary and main.
-func (p *Page) setUserDefinedSummary(rawContentCopy []byte) (*summaryContent, error) {
-
-	sc, err := splitUserDefinedSummaryAndContent(p.Markup, rawContentCopy)
-
-	if err != nil {
-		return nil, err
-	}
-
-	if sc == nil {
-		// No divider found
-		return nil, nil
-	}
+	})
 
-	p.summary = helpers.BytesToHTML(sc.summary)
+	return p.translationKey
 
-	return sc, nil
 }
 
-// Make this explicit so there is no doubt about what is what.
-type summaryContent struct {
-	summary []byte
-	content []byte
+// AllTranslations returns all translations, including the current Page.
+func (p *pageState) AllTranslations() page.Pages {
+	p.s.h.init.translations.Do()
+	return p.allTranslations
 }
 
-func splitUserDefinedSummaryAndContent(markup string, c []byte) (sc *summaryContent, err error) {
-	defer func() {
-		if r := recover(); r != nil {
-			err = fmt.Errorf("summary split failed: %s", r)
-		}
-	}()
-
-	startDivider := bytes.Index(c, internalSummaryDividerBaseBytes)
-
-	if startDivider == -1 {
-		return
-	}
-
-	startTag := "p"
-	switch markup {
-	case "asciidoc":
-		startTag = "div"
-
-	}
-
-	// Walk back and forward to the surrounding tags.
-	start := bytes.LastIndex(c[:startDivider], []byte("<"+startTag))
-	end := bytes.Index(c[startDivider:], []byte("</"+startTag))
-
-	if start == -1 {
-		start = startDivider
-	} else {
-		start = startDivider - (startDivider - start)
-	}
-
-	if end == -1 {
-		end = startDivider + len(internalSummaryDividerBase)
-	} else {
-		end = startDivider + end + len(startTag) + 3
-	}
-
-	var addDiv bool
-
-	switch markup {
-	case "rst":
-		addDiv = true
-	}
-
-	withoutDivider := append(c[:start], bytes.Trim(c[end:], "\n")...)
-
-	var summary []byte
-
-	if len(withoutDivider) > 0 {
-		summary = bytes.TrimSpace(withoutDivider[:start])
-	}
-
-	if addDiv {
-		// For the rst
-		summary = append(append([]byte(nil), summary...), []byte("</div>")...)
-	}
-
-	if err != nil {
-		return
-	}
+// Translations returns the translations excluding the current Page.
+func (p *pageState) Translations() page.Pages {
+	p.s.h.init.translations.Do()
+	return p.translations
+}
 
-	sc = &summaryContent{
-		summary: summary,
-		content: bytes.TrimSpace(withoutDivider),
+func (p *pageState) getRenderingConfig() *helpers.BlackFriday {
+	if p.m.renderingConfig == nil {
+		return p.s.ContentSpec.BlackFriday
 	}
-
-	return
+	return p.m.renderingConfig
 }
 
-func (p *Page) setAutoSummary() error {
-	var summary string
-	var truncated bool
-	// This careful init dance could probably be refined, but it is purely for performance
-	// reasons. These "plain" methods are expensive if the plain content is never actually
-	// used.
-	p.initPlain(false)
-	if p.isCJKLanguage {
-		p.initPlainWords(false)
-		summary, truncated = p.s.ContentSpec.TruncateWordsByRune(p.plainWords)
-	} else {
-		summary, truncated = p.s.ContentSpec.TruncateWordsToWholeSentence(p.plain)
+func (ps *pageState) initCommonProviders(pp pagePaths) error {
+	if ps.IsPage() {
+		ps.posNextPrev = &nextPrev{init: ps.s.init.prevNext}
+		ps.posNextPrevSection = &nextPrev{init: ps.s.init.prevNextInSection}
+		ps.InSectionPositioner = newPagePositionInSection(ps.posNextPrevSection)
+		ps.Positioner = newPagePosition(ps.posNextPrev)
 	}
-	p.summary = template.HTML(summary)
-	p.truncated = truncated
 
-	return nil
-
-}
+	ps.OutputFormatsProvider = pp
+	ps.targetPathDescriptor = pp.targetPathDescriptor
+	ps.RefProvider = newPageRef(ps)
+	ps.SitesProvider = &ps.s.Info
 
-func (p *Pag