1 files changed, 331 insertions, 0 deletions
diff --git a/hugolib/pagesfromdata/pagesfromgotmpl.go b/hugolib/pagesfromdata/pagesfromgotmpl.go
new file mode 100644
index 000000000..4107f9e33
--- /dev/null
+++ b/hugolib/pagesfromdata/pagesfromgotmpl.go
@@ -0,0 +1,331 @@
+// Copyright 2024 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 pagesfromdata
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"path/filepath"
+
+	"github.com/gohugoio/hugo/common/maps"
+	"github.com/gohugoio/hugo/common/paths"
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/hugofs"
+	"github.com/gohugoio/hugo/identity"
+	"github.com/gohugoio/hugo/resources/page"
+	"github.com/gohugoio/hugo/resources/page/pagemeta"
+	"github.com/gohugoio/hugo/resources/resource"
+	"github.com/gohugoio/hugo/tpl"
+	"github.com/mitchellh/mapstructure"
+	"github.com/spf13/cast"
+)
+
+type PagesFromDataTemplateContext interface {
+	// AddPage adds a new page to the site.
+	// The first return value will always be an empty string.
+	AddPage(any) (string, error)
+
+	// AddResource adds a new resource to the site.
+	// The first return value will always be an empty string.
+	AddResource(any) (string, error)
+
+	// The site to which the pages will be added.
+	Site() page.Site
+
+	// The same template may be executed multiple times for multiple languages.
+	// The Store can be used to store state between these invocations.
+	Store() *maps.Scratch
+
+	// By default, the template will be executed for the language
+	// defined by the _content.gotmpl file (e.g. its mount definition).
+	// This method can be used to activate the template for all languages.
+	// The return value will always be an empty string.
+	EnableAllLanguages() string
+}
+
+var _ PagesFromDataTemplateContext = (*pagesFromDataTemplateContext)(nil)
+
+type pagesFromDataTemplateContext struct {
+	p *PagesFromTemplate
+}
+
+func (p *pagesFromDataTemplateContext) toPathMap(v any) (string, map[string]any, error) {
+	m, err := maps.ToStringMapE(v)
+	if err != nil {
+		return "", nil, err
+	}
+	pathv, ok := m["path"]
+	if !ok {
+		return "", nil, fmt.Errorf("path not set")
+	}
+	path, err := cast.ToStringE(pathv)
+	if err != nil || path == "" {
+		return "", nil, fmt.Errorf("invalid path %q", path)
+	}
+	return path, m, nil
+}
+
+func (p *pagesFromDataTemplateContext) AddPage(v any) (string, error) {
+	path, m, err := p.toPathMap(v)
+	if err != nil {
+		return "", err
+	}
+
+	if !p.p.buildState.checkHasChangedAndSetSourceInfo(path, m) {
+		return "", nil
+	}
+
+	pd := pagemeta.DefaultPageConfig
+	pd.IsFromContentAdapter = true
+
+	if err := mapstructure.WeakDecode(m, &pd); err != nil {
+		return "", fmt.Errorf("failed to decode page map: %w", err)
+	}
+
+	p.p.buildState.NumPagesAdded++
+
+	if err := pd.Validate(true); err != nil {
+		return "", err
+	}
+
+	return "", p.p.HandlePage(p.p, &pd)
+}
+
+func (p *pagesFromDataTemplateContext) AddResource(v any) (string, error) {
+	path, m, err := p.toPathMap(v)
+	if err != nil {
+		return "", err
+	}
+
+	if !p.p.buildState.checkHasChangedAndSetSourceInfo(path, m) {
+		return "", nil
+	}
+
+	var rd pagemeta.ResourceConfig
+	if err := mapstructure.WeakDecode(m, &rd); err != nil {
+		return "", err
+	}
+
+	p.p.buildState.NumResourcesAdded++
+
+	if err := rd.Validate(); err != nil {
+		return "", err
+	}
+
+	return "", p.p.HandleResource(p.p, &rd)
+}
+
+func (p *pagesFromDataTemplateContext) Site() page.Site {
+	return p.p.Site
+}
+
+func (p *pagesFromDataTemplateContext) Store() *maps.Scratch {
+	return p.p.store
+}
+
+func (p *pagesFromDataTemplateContext) EnableAllLanguages() string {
+	p.p.buildState.EnableAllLanguages = true
+	return ""
+}
+
+func NewPagesFromTemplate(opts PagesFromTemplateOptions) *PagesFromTemplate {
+	return &PagesFromTemplate{
+		PagesFromTemplateOptions: opts,
+		PagesFromTemplateDeps:    opts.DepsFromSite(opts.Site),
+		buildState: &BuildState{
+			sourceInfosCurrent: maps.NewCache[string, *sourceInfo](),
+		},
+		store: maps.NewScratch(),
+	}
+}
+
+type PagesFromTemplateOptions struct {
+	Site         page.Site
+	DepsFromSite func(page.Site) PagesFromTemplateDeps
+
+	DependencyManager identity.Manager
+
+	Watching bool
+
+	HandlePage     func(pt *PagesFromTemplate, p *pagemeta.PageConfig) error
+	HandleResource func(pt *PagesFromTemplate, p *pagemeta.ResourceConfig) error
+
+	GoTmplFi hugofs.FileMetaInfo
+}
+
+type PagesFromTemplateDeps struct {
+	TmplFinder tpl.TemplateParseFinder
+	TmplExec   tpl.TemplateExecutor
+}
+
+var _ resource.Staler = (*PagesFromTemplate)(nil)
+
+type PagesFromTemplate struct {
+	PagesFromTemplateOptions
+	PagesFromTemplateDeps
+	buildState *BuildState
+	store      *maps.Scratch
+}
+
+func (b *PagesFromTemplate) AddChange(id identity.Identity) {
+	b.buildState.ChangedIdentities = append(b.buildState.ChangedIdentities, id)
+}
+
+func (b *PagesFromTemplate) MarkStale() {
+	b.buildState.StaleVersion++
+}
+
+func (b *PagesFromTemplate) StaleVersion() uint32 {
+	return b.buildState.StaleVersion
+}
+
+type BuildInfo struct {
+	NumPagesAdded      uint64
+	NumResourcesAdded  uint64
+	EnableAllLanguages bool
+	ChangedIdentities  []identity.Identity
+	DeletedPaths       []string
+	Path               *paths.Path
+}
+
+type BuildState struct {
+	StaleVersion uint32
+
+	EnableAllLanguages bool
+
+	// Paths deleted in the current build.
+	DeletedPaths []string
+
+	// Changed identities in the current build.
+	ChangedIdentities []identity.Identity
+
+	NumPagesAdded     uint64
+	NumResourcesAdded uint64
+
+	sourceInfosCurrent  *maps.Cache[string, *sourceInfo]
+	sourceInfosPrevious *maps.Cache[string, *sourceInfo]
+}
+
+func (b *BuildState) hash(v any) uint64 {
+	return identity.HashUint64(v)
+}
+
+func (b *BuildState) checkHasChangedAndSetSourceInfo(changedPath string, v any) bool {
+	h := b.hash(v)
+	si, found := b.sourceInfosPrevious.Get(changedPath)
+	if found {
+		b.sourceInfosCurrent.Set(changedPath, si)
+		if si.hash == h {
+			return false
+		}
+	} else {
+		si = &sourceInfo{}
+		b.sourceInfosCurrent.Set(changedPath, si)
+	}
+	si.hash = h
+	return true
+}
+
+func (b *BuildState) resolveDeletedPaths() {
+	if b.sourceInfosPrevious == nil {
+		b.DeletedPaths = nil
+		return
+	}
+	var paths []string
+	b.sourceInfosPrevious.ForEeach(func(k string, _ *sourceInfo) {
+		if _, found := b.sourceInfosCurrent.Get(k); !found {
+			paths = append(paths, k)
+		}
+	})
+
+	b.DeletedPaths = paths
+}
+
+func (b *BuildState) PrepareNextBuild() {
+	b.sourceInfosPrevious = b.sourceInfosCurrent
+	b.sourceInfosCurrent = maps.NewCache[string, *sourceInfo]()
+	b.StaleVersion = 0
+	b.DeletedPaths = nil
+	b.ChangedIdentities = nil
+	b.NumPagesAdded = 0
+	b.NumResourcesAdded = 0
+}
+
+type sourceInfo struct {
+	hash uint64
+}
+
+func (p PagesFromTemplate) CloneForSite(s page.Site) *PagesFromTemplate {
+	// We deliberately make them share the same DepenencyManager and Store.
+	p.PagesFromTemplateOptions.Site = s
+	p.PagesFromTemplateDeps = p.PagesFromTemplateOptions.DepsFromSite(s)
+	p.buildState = &BuildState{
+		sourceInfosCurrent: maps.NewCache[string, *sourceInfo](),
+	}
+	return &p
+}
+
+func (p PagesFromTemplate) CloneForGoTmpl(fi hugofs.FileMetaInfo) *PagesFromTemplate {
+	p.PagesFromTemplateOptions.GoTmplFi = fi
+	return &p
+}
+
+func (p *PagesFromTemplate) GetDependencyManagerForScope(scope int) identity.Manager {
+	return p.DependencyManager
+}
+
+func (p *PagesFromTemplate) Execute(ctx context.Context) (BuildInfo, error) {
+	defer func() {
+		p.buildState.PrepareNextBuild()
+	}()
+
+	f, err := p.GoTmplFi.Meta().Open()
+	if err != nil {
+		return BuildInfo{}, err
+	}
+	defer f.Close()
+
+	tmpl, err := p.TmplFinder.Parse(filepath.ToSlash(p.GoTmplFi.Meta().Filename), helpers.ReaderToString(f))
+	if err != nil {
+		return BuildInfo{}, err
+	}
+
+	data := &pagesFromDataTemplateContext{
+		p: p,
+	}
+
+	ctx = tpl.Context.DependencyManagerScopedProvider.Set(ctx, p)
+
+	if err := p.TmplExec.ExecuteWithContext(ctx, tmpl, io.Discard, data); err != nil {
+		return BuildInfo{}, err
+	}
+
+	if p.Watching {
+		p.buildState.resolveDeletedPaths()
+	}
+
+	bi := BuildInfo{
+		NumPagesAdded:      p.buildState.NumPagesAdded,
+		NumResourcesAdded:  p.buildState.NumResourcesAdded,
+		EnableAllLanguages: p.buildState.EnableAllLanguages,
+		ChangedIdentities:  p.buildState.ChangedIdentities,
+		DeletedPaths:       p.buildState.DeletedPaths,
+		Path:               p.GoTmplFi.Meta().PathInfo,
+	}
+
+	return bi, nil
+}
+
+//////////////