Introduced templating and views

templating/consts.go

@@ -0,0 +1,14 @@
+package templating
+
+var TEMPLATE_FORMATS = []string{".html", ".tmpl", ".gotmpl", ".gotemplate", ".gohtml", ".gohtmltemplate"}
+
+const TEMPLATE_GLOBAL_CONTEXT_NAME = "globals"
+const TEMPLATE_ROOT_NAME = "root"
+const TEMPLATE_LOCAL_CONTEXT_NAME = "locals"
+const TEMPLATE_GLOBAL_PREFIX = "_"
+const TEMPLATE_COMPONENT_DIRECTORY = "components"
+const TEMPLATE_HEAD = "head"
+const TEMPLATE_BODY = "body"
+const TEMPLATE_HEADERS = "headers"
+const ROOT_LAYOUT_NAME = "root"
+const DEFAULT_LAYOUT_NAME = "default"

templating/context.go

@@ -0,0 +1,148 @@
+package templating
+
+import (
+	"html/template"
+	"io/fs"
+	"path/filepath"
+	"slices"
+	"strings"
+)
+
+type TemplateContext struct {
+	//  WARNING: Path is a URL path, NOT a filesystem path
+	Path string
+	//  WARNING: The keys of these maps are template names, NOT filesystem paths
+	// The values are FS paths absolute from the root directory of the templates FS
+	locals  map[string]string
+	globals map[string]string
+}
+
+func NewTemplateContext(path string) TemplateContext {
+	return TemplateContext{
+		Path:    path,
+		locals:  make(map[string]string),
+		globals: make(map[string]string),
+	}
+}
+
+func (c *TemplateContext) Parse(fsys fs.FS) error {
+	fspath := PathToFSPath(c.Path)
+	entries, err := fs.ReadDir(fsys, fspath)
+
+	if err != nil {
+		return NewError(InvalidPathError, c.Path)
+	}
+
+	for _, e := range entries {
+		if e.IsDir() {
+			// INFO: components in the components directory can be overwritten
+			// by components in the base directory down below
+			// TODO: Maybe allow for subdirectories in the components directory?
+			if e.Name() == TEMPLATE_COMPONENT_DIRECTORY {
+				entries, err := fs.ReadDir(fsys, filepath.Join(fspath, e.Name()))
+				if err != nil {
+					return NewError(FileAccessError, filepath.Join(fspath, e.Name()))
+				}
+
+				for _, e := range entries {
+					ext := filepath.Ext(e.Name())
+
+					if !slices.Contains(TEMPLATE_FORMATS, ext) {
+						continue
+					}
+
+					name := strings.TrimSuffix(e.Name(), ext)
+					if strings.HasPrefix(e.Name(), TEMPLATE_GLOBAL_PREFIX) {
+						c.globals[name] = filepath.Join(fspath, TEMPLATE_COMPONENT_DIRECTORY, e.Name())
+					} else {
+						c.locals[name] = filepath.Join(fspath, TEMPLATE_COMPONENT_DIRECTORY, e.Name())
+					}
+				}
+				continue
+			}
+		}
+
+		ext := filepath.Ext(e.Name())
+
+		if !slices.Contains(TEMPLATE_FORMATS, ext) {
+			continue
+		}
+
+		name := strings.TrimSuffix(e.Name(), ext)
+		if strings.HasPrefix(e.Name(), TEMPLATE_GLOBAL_PREFIX) {
+			c.globals[name] = filepath.Join(fspath, e.Name())
+		} else {
+			c.locals[name] = filepath.Join(fspath, e.Name())
+		}
+	}
+
+	return nil
+}
+
+func (c *TemplateContext) SetGlobals(globals map[string]string) error {
+	// INFO: this allows for overwriting of existing global keys.
+	// Make sure to call this appopriately before or after Parse(), depending on your use case
+	for k, v := range globals {
+		c.globals[k] = v
+	}
+	return nil
+}
+
+func (c *TemplateContext) Globals() map[string]string {
+	return c.globals
+}
+
+func (c *TemplateContext) Template(fsys fs.FS, funcmap *template.FuncMap) (*template.Template, error) {
+	// TODO: locals need to be in order: root, head, body
+	t, err := readTemplates(fsys, nil, c.locals, funcmap)
+	if err != nil {
+		return nil, err
+	}
+
+	t, err = readTemplates(fsys, t, c.globals, funcmap)
+	if err != nil {
+		return nil, err
+	}
+
+	return t, nil
+}
+
+func readTemplates(fsys fs.FS, t *template.Template, paths map[string]string, funcmap *template.FuncMap) (*template.Template, error) {
+	for k, v := range paths {
+		text, err := fs.ReadFile(fsys, v)
+		if err != nil {
+			return nil, NewError(FileAccessError, v)
+		}
+
+		temp := template.New(k)
+
+		if funcmap != nil {
+			temp.Funcs(*funcmap)
+		}
+
+		temp, err = temp.Parse(string(text))
+		if err != nil {
+			return nil, err
+		}
+
+		if t == nil {
+			t = temp
+			continue
+		}
+
+		for _, template := range temp.Templates() {
+			_, err = t.AddParseTree(template.Name(), template.Tree)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		_, err = t.AddParseTree(temp.Name(), temp.Tree)
+		if err != nil {
+			return nil, err
+		}
+
+	}
+
+	return t, nil
+}

templating/engine.go

@@ -0,0 +1,148 @@
+package templating
+
+import (
+	"html/template"
+	"io"
+	"io/fs"
+	"sync"
+)
+
+const (
+	ASSETS_URL_PREFIX = "/assets"
+)
+
+type Engine struct {
+	// NOTE: LayoutRegistry and TemplateRegistry have their own syncronization & cache and do not require a mutex here
+	LayoutRegistry   *LayoutRegistry
+	TemplateRegistry *TemplateRegistry
+
+	mu         *sync.Mutex
+	FuncMap    template.FuncMap
+	GlobalData map[string]interface{}
+}
+
+// INFO: We pass the app here to be able to access the config and other data for functions
+// which also means we must reload the engine if the app changes
+func NewEngine(layouts, templates *fs.FS) *Engine {
+	e := Engine{
+		mu:               &sync.Mutex{},
+		LayoutRegistry:   NewLayoutRegistry(*layouts),
+		TemplateRegistry: NewTemplateRegistry(*templates),
+		FuncMap:          make(template.FuncMap),
+	}
+	e.funcs()
+	return &e
+}
+
+func (e *Engine) funcs() error {
+	e.mu.Lock()
+	e.mu.Unlock()
+	return nil
+}
+
+func (e *Engine) Globals(data map[string]interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if e.GlobalData == nil {
+		e.GlobalData = data
+	} else {
+		for k, v := range data {
+			(e.GlobalData)[k] = v
+		}
+	}
+}
+
+func (e *Engine) Load() error {
+	wg := sync.WaitGroup{}
+	wg.Add(2)
+
+	go func() {
+		defer wg.Done()
+		e.LayoutRegistry.Load()
+	}()
+
+	go func() {
+		defer wg.Done()
+		e.TemplateRegistry.Load()
+	}()
+
+	wg.Wait()
+	return nil
+}
+
+func (e *Engine) Reload() error {
+	wg := sync.WaitGroup{}
+	wg.Add(2)
+
+	go func() {
+		defer wg.Done()
+		e.LayoutRegistry.Reset()
+	}()
+
+	go func() {
+		defer wg.Done()
+		e.TemplateRegistry.Reset()
+	}()
+
+	wg.Wait()
+	return nil
+}
+
+// INFO: fn is a function that returns either one value or two values, the second one being an error
+func (e *Engine) AddFunc(name string, fn interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	e.FuncMap[name] = fn
+}
+
+func (e *Engine) AddFuncs(funcs map[string]interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	for k, v := range funcs {
+		e.FuncMap[k] = v
+	}
+}
+
+func (e *Engine) Render(out io.Writer, path string, ld map[string]interface{}, layout ...string) error {
+	// TODO: check if a reload is needed if files on disk have changed
+	gd := e.GlobalData
+	if e.GlobalData != nil {
+		for k, v := range ld {
+			gd[k] = v
+		}
+	}
+
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	var l *template.Template
+	if layout == nil || len(layout) == 0 {
+		lay, err := e.LayoutRegistry.Default(&e.FuncMap)
+		if err != nil {
+			return err
+		}
+		l = lay
+	} else {
+		lay, err := e.LayoutRegistry.Layout(layout[0], &e.FuncMap)
+		if err != nil {
+			return err
+		}
+		l = lay
+	}
+
+	lay, err := l.Clone()
+	if err != nil {
+		return err
+	}
+
+	err = e.TemplateRegistry.Add(path, lay, &e.FuncMap)
+	if err != nil {
+		return err
+	}
+
+	err = lay.Execute(out, gd)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

templating/errors.go

@@ -0,0 +1,21 @@
+package templating
+
+import "errors"
+
+var InvalidPathError = errors.New("Invalid path. Must be a directory.")
+var NoTemplateError = errors.New("No template found for this name")
+var InvalidTemplateError = errors.New("invalid template")
+var FileAccessError = errors.New("could not stat file or directory")
+
+type FSError[T error] struct {
+	File string
+	Err  T
+}
+
+func NewError[T error](t T, file string) FSError[T] {
+	return FSError[T]{File: file, Err: t}
+}
+
+func (e FSError[T]) Error() string {
+	return e.Err.Error() + ": " + e.File
+}

templating/helpers.go

@@ -0,0 +1,32 @@
+package templating
+
+import "strings"
+
+func PathToFSPath(p string) string {
+	if p == "/" {
+		return "."
+	}
+
+	p = strings.TrimPrefix(p, "/")
+	p = strings.TrimSuffix(p, "/")
+
+	return p
+}
+
+func FSPathToPath(p string) string {
+	if p == "." {
+		return "/"
+	}
+
+	p = strings.TrimPrefix(p, ".")
+
+	if !strings.HasPrefix(p, "/") {
+		p = "/" + p
+	}
+
+	if !strings.HasSuffix(p, "/") {
+		p = p + "/"
+	}
+
+	return p
+}

templating/layout_registry.go

@@ -0,0 +1,108 @@
+package templating
+
+import (
+	"html/template"
+	"io/fs"
+	"sync"
+
+	"github.com/Theodor-Springmann-Stiftung/musenalm/helpers"
+	"github.com/yalue/merged_fs"
+)
+
+// TODO: Implement Handler interface, maybe in template? But then template would need to know about the layout registry
+// Function signature: func (t *templateHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)
+// A static Handler could incoporate both the layout registry and the template registry and serve templates that dont need any data
+// INFO: this ist thread-safe and safe to call in a handler or middleware
+type LayoutRegistry struct {
+	layoutsFS fs.FS
+	once      sync.Once
+	// INFO: Layout & cache keys are template directory names
+	layouts map[string]TemplateContext
+	// WARNING: maybe this is too early for caching?
+	cache sync.Map
+}
+
+func NewLayoutRegistry(routes fs.FS) *LayoutRegistry {
+	return &LayoutRegistry{
+		layoutsFS: routes,
+	}
+}
+
+// NOTE: Upon registering a new layout dir, we return a new LayoutRegistry
+func (r *LayoutRegistry) Register(fs fs.FS) *LayoutRegistry {
+	return NewLayoutRegistry(merged_fs.MergeMultiple(fs, r.layoutsFS))
+}
+
+func (r *LayoutRegistry) Reset() error {
+	r.cache.Clear()
+	r.once = sync.Once{}
+	return nil
+}
+
+func (r *LayoutRegistry) Load() error {
+	r.once.Do(func() {
+		err := r.load()
+		helpers.Assert(err, "Error loading layouts. Exiting.")
+	})
+
+	return nil
+}
+
+func (r *LayoutRegistry) load() error {
+	layouts := make(map[string]TemplateContext)
+	rootcontext := NewTemplateContext(".")
+	err := rootcontext.Parse(r.layoutsFS)
+	if err != nil {
+		return err
+	}
+
+	globals := rootcontext.Globals()
+
+	entries, err := fs.ReadDir(r.layoutsFS, ".")
+	if err != nil {
+		return NewError(FileAccessError, ".")
+	}
+
+	for _, e := range entries {
+		if !e.IsDir() || e.Name() == TEMPLATE_COMPONENT_DIRECTORY {
+			continue
+		}
+
+		url := FSPathToPath(e.Name())
+		context := NewTemplateContext(url)
+		context.SetGlobals(globals)
+		context.Parse(r.layoutsFS)
+
+		layouts[e.Name()] = context
+	}
+
+	r.layouts = layouts
+	return nil
+}
+
+func (r *LayoutRegistry) Layout(name string, funcmap *template.FuncMap) (*template.Template, error) {
+	cached, ok := r.cache.Load(name)
+	if ok {
+		return cached.(*template.Template), nil
+	}
+
+	// TODO: What todo on errors?
+	r.Load()
+	context, ok := r.layouts[name]
+	if !ok {
+		return nil, NewError(NoTemplateError, name)
+	}
+
+	t, err := context.Template(r.layoutsFS, funcmap)
+	if err != nil {
+		return nil, err
+	}
+
+	r.cache.Store(name, t)
+
+	return t, nil
+}
+
+func (r *LayoutRegistry) Default(funcmap *template.FuncMap) (*template.Template, error) {
+	return r.Layout(DEFAULT_LAYOUT_NAME, funcmap)
+}

templating/template_registry.go

@@ -0,0 +1,120 @@
+package templating
+
+import (
+	"html/template"
+	"io/fs"
+	"os"
+	"strings"
+	"sync"
+
+	"github.com/Theodor-Springmann-Stiftung/musenalm/helpers"
+	"github.com/yalue/merged_fs"
+)
+
+// INFO: this ist thread-safe and safe to call in a handler or middleware
+type TemplateRegistry struct {
+	routesFS fs.FS
+	once     sync.Once
+	// INFO: Template & cache keys are directory routing paths, with '/' as root
+	// INFO: we don't need a mutex here since this is set in Load() protected by Once().
+	templates map[string]TemplateContext
+	cache     sync.Map
+}
+
+func NewTemplateRegistry(routes fs.FS) *TemplateRegistry {
+	return &TemplateRegistry{
+		routesFS: routes,
+	}
+}
+
+// INFO: This returns a new TemplateRegistry with the new fs added to the existing fs,
+// merging with the existing FS, possibly overwriting existing files.
+func (r *TemplateRegistry) Register(path string, fs fs.FS) *TemplateRegistry {
+	return NewTemplateRegistry(merged_fs.MergeMultiple(fs, r.routesFS))
+}
+
+func (r *TemplateRegistry) Reset() error {
+	r.cache.Clear()
+	r.once = sync.Once{}
+	return nil
+}
+
+func (r *TemplateRegistry) Load() error {
+	r.once.Do(func() {
+		err := r.load()
+		helpers.Assert(err, "Error loading templates. Exiting.")
+	})
+	return nil
+}
+
+// TODO: Throw errors
+// TODO: what if there is no template in the directory above?
+// What if a certain path is or should uncallable since it has no index or body?
+func (r *TemplateRegistry) load() error {
+	templates := make(map[string]TemplateContext)
+	fs.WalkDir(r.routesFS, ".", func(path string, d fs.DirEntry, err error) error {
+		if !d.IsDir() {
+			return nil
+		}
+
+		url := FSPathToPath(path)
+		tc := NewTemplateContext(url)
+
+		if path != "." {
+			pathelem := strings.Split(path, string(os.PathSeparator))
+			pathabove := strings.Join(pathelem[:len(pathelem)-1], string(os.PathSeparator))
+			pathabove = FSPathToPath(pathabove)
+
+			global, ok := templates[pathabove]
+			if ok {
+				tc.SetGlobals(global.Globals())
+			}
+		}
+
+		tc.Parse(r.routesFS)
+
+		templates[url] = tc
+
+		return nil
+	})
+
+	r.templates = templates
+	return nil
+}
+
+// This function takes a template (typically a layout) and adds all the templates of
+// a given directory path to it. This is useful for adding a layout to a template.
+func (r *TemplateRegistry) Add(path string, t *template.Template, funcmap *template.FuncMap) error {
+	temp, ok := r.cache.Load(path)
+	if !ok {
+		r.Load()
+		tc, ok := r.templates[path]
+		if !ok {
+			return NewError(NoTemplateError, path)
+		}
+
+		template, err := tc.Template(r.routesFS, funcmap)
+		if err != nil {
+			return err
+		}
+
+		r.cache.Store(path, template)
+
+		return r.Add(path, t, funcmap)
+	}
+
+	casted := temp.(*template.Template)
+	for _, st := range casted.Templates() {
+		_, err := t.AddParseTree(st.Name(), st.Tree)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// TODO: get for a specific component
+func (r *TemplateRegistry) Get(path string) error {
+	return nil
+}