new MemoryFileSystem

Author: kataras

Diff for: README.md

@@ -10,6 +10,7 @@ Blocks is a, simple, Go-idiomatic view engine based on [html/template](https://p
 - Reload templates on development stage
 - Full Layouts and Blocks support
 - Automatic HTML comments removal
+- Memory File System
 - Markdown Content
 - Global [FuncMap](https://pkg.go.dev/html/template?tab=doc#FuncMap)
 

Diff for: blocks.go

@@ -573,10 +573,10 @@ func (v *Blocks) executeTemplate(w io.Writer, tmplName, layoutName string, data
 	return tmpl.Execute(w, data)
 }
 
-// ParseTemplate parses a template based on its "tmplName" name and returns the result.
+// TemplateString executes a template based on its "tmplName" name and returns its contents result.
 // Note that, this does not reload the templates on each call if Reload was set to true.
 // To refresh the templates you have to manually call the `Load` upfront.
-func (v *Blocks) ParseTemplate(tmplName, layoutName string, data any) (string, error) {
+func (v *Blocks) TemplateString(tmplName, layoutName string, data any) (string, error) {
 	b := v.bufferPool.Get()
 	// use the unexported method so it does not re-reload the templates on each partial one
 	// when Reload was set to true.
@@ -592,7 +592,7 @@ func (v *Blocks) PartialFunc(partialName string, data any) (template.HTML, error
 	// if err != nil {
 	// 	return "", err
 	// }
-	contents, err := v.ParseTemplate(partialName, "", data)
+	contents, err := v.TemplateString(partialName, "", data)
 	if err != nil {
 		return "", err
 	}

Diff for: fs.go

@@ -2,10 +2,13 @@ package blocks
 
 import (
 	"fmt"
+	"html/template"
+	"io"
 	"io/fs"
 	"net/http"
 	"os"
 	"path/filepath"
+	"time"
 )
 
 func getFS(fsOrDir any) fs.FS {
@@ -110,3 +113,121 @@ func (f *httpFS) ReadDir(name string) ([]fs.DirEntry, error) {
 
 	return entries, nil
 }
+
+// MemoryFileSystem is a custom file system that holds virtual/memory template files in memory.
+// It completes the fs.FS interface.
+type MemoryFileSystem struct {
+	files map[string]*memoryTemplateFile
+}
+
+// NewMemoryFileSystem creates a new VirtualFileSystem instance.
+// It comes with no files, use `ParseTemplate` to add new virtual/memory template files.
+// Usage:
+//
+//	vfs := NewVirtualFileSystem()
+//	err := vfs.ParseTemplate("example.html", []byte("Hello, World!"), nil)
+//	templates := New(vfs)
+//	templates.Load()
+func NewMemoryFileSystem() *MemoryFileSystem {
+	return &MemoryFileSystem{
+		files: make(map[string]*memoryTemplateFile),
+	}
+}
+
+var _ fs.FS = (*MemoryFileSystem)(nil)
+
+// ParseTemplate adds a new memory temlate to the file system.
+func (vfs *MemoryFileSystem) ParseTemplate(name string, contents []byte, funcMap template.FuncMap) error {
+	vfs.files[name] = &memoryTemplateFile{
+		name:     name,
+		contents: contents,
+		funcMap:  funcMap,
+	}
+	return nil
+}
+
+// Open implements the fs.FS interface.
+func (vfs *MemoryFileSystem) Open(name string) (fs.File, error) {
+	if file, exists := vfs.files[name]; exists {
+		file.reset() // Reset read position
+		return file, nil
+	}
+	return nil, fs.ErrNotExist
+}
+
+// memoryTemplateFile represents a memory file.
+type memoryTemplateFile struct {
+	name     string
+	contents []byte
+	funcMap  template.FuncMap
+	offset   int64
+}
+
+// Ensure memoryTemplateFile implements fs.File interface.
+var _ fs.File = (*memoryTemplateFile)(nil)
+
+func (vf *memoryTemplateFile) reset() {
+	vf.offset = 0
+}
+
+// Stat implements the fs.File interface, returning file info.
+func (vf *memoryTemplateFile) Stat() (fs.FileInfo, error) {
+	return &memoryFileInfo{
+		name: vf.name,
+		size: int64(len(vf.contents)),
+	}, nil
+}
+
+// Read implements the io.Reader interface.
+func (vf *memoryTemplateFile) Read(p []byte) (int, error) {
+	if vf.offset >= int64(len(vf.contents)) {
+		return 0, io.EOF
+	}
+	n := copy(p, vf.contents[vf.offset:])
+	vf.offset += int64(n)
+	return n, nil
+}
+
+// Close implements the io.Closer interface.
+func (vf *memoryTemplateFile) Close() error {
+	return nil
+}
+
+// memoryFileInfo provides file information for a memory file.
+type memoryFileInfo struct {
+	name string
+	size int64
+}
+
+// Ensure memoryFileInfo implements fs.FileInfo interface.
+var _ fs.FileInfo = (*memoryFileInfo)(nil)
+
+// Name returns the base name of the file.
+func (fi *memoryFileInfo) Name() string {
+	return fi.name
+}
+
+// Size returns the length in bytes for regular files.
+func (fi *memoryFileInfo) Size() int64 {
+	return fi.size
+}
+
+// Mode returns file mode bits.
+func (fi *memoryFileInfo) Mode() fs.FileMode {
+	return 0444 // Read-only
+}
+
+// ModTime returns modification time.
+func (fi *memoryFileInfo) ModTime() time.Time {
+	return time.Now()
+}
+
+// IsDir reports if the file is a directory.
+func (fi *memoryFileInfo) IsDir() bool {
+	return false
+}
+
+// Sys returns underlying data source (can return nil).
+func (fi *memoryFileInfo) Sys() interface{} {
+	return nil
+}