add HTML rendering capabilities and helper functions

template.go

@@ -0,0 +1,141 @@
+package ron
+
+import (
+	"bytes"
+	"errors"
+	"html/template"
+	"io/fs"
+	"net/http"
+	"path/filepath"
+	"strings"
+)
+
+type (
+	templateCache map[string]*template.Template
+
+	TemplateData struct {
+		Data Data
+	}
+
+	OptionFunc func(*Render)
+	Render     struct {
+		EnableCache   bool
+		TemplatesPath string
+		Functions     template.FuncMap
+		templateCache templateCache
+	}
+)
+
+func DefaultHTMLRender() *Render {
+	return &Render{
+		EnableCache:   false,
+		TemplatesPath: "templates",
+		Functions:     make(template.FuncMap),
+		templateCache: make(templateCache),
+	}
+}
+
+func HTMLRender(opts ...OptionFunc) *Render {
+	config := DefaultHTMLRender()
+	return config.apply(opts...)
+}
+
+func (re *Render) apply(opts ...OptionFunc) *Render {
+	for _, opt := range opts {
+		if opt != nil {
+			opt(re)
+		}
+	}
+
+	return re
+}
+
+func (re *Render) Template(w http.ResponseWriter, tmpl string, td *TemplateData) error {
+	var tc templateCache
+	var err error
+
+	if td == nil {
+		td = &TemplateData{}
+	}
+
+	if re.EnableCache {
+		tc = re.templateCache
+	} else {
+		tc, err = re.createTemplateCache()
+		if err != nil {
+			return err
+		}
+	}
+
+	t, ok := tc[tmpl]
+	if !ok {
+		return errors.New("can't get template from cache")
+	}
+
+	buf := new(bytes.Buffer)
+	err = t.Execute(buf, td)
+	if err != nil {
+		return err
+	}
+
+	_, err = buf.WriteTo(w)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (re *Render) findHTMLFiles() ([]string, error) {
+	var files []string
+
+	err := filepath.WalkDir(re.TemplatesPath, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if !d.IsDir() && filepath.Ext(path) == ".gohtml" {
+			files = append(files, path)
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return files, nil
+}
+
+func (re *Render) createTemplateCache() (templateCache, error) {
+	cache := templateCache{}
+	var baseTemplates []string
+	var renderTemplates []string
+
+	templates, err := re.findHTMLFiles()
+	if err != nil {
+		return cache, err
+	}
+
+	for _, file := range templates {
+		filePathBase := filepath.Base(file)
+		if strings.Contains(filePathBase, "layout") || strings.Contains(filePathBase, "fragment") {
+			baseTemplates = append(baseTemplates, file)
+		}
+	}
+
+	for _, file := range templates {
+		filePathBase := filepath.Base(file)
+		if strings.Contains(filePathBase, "page") || strings.Contains(filePathBase, "component") {
+			renderTemplates = append(baseTemplates, file)
+			ts, err := template.New(filePathBase).Funcs(re.Functions).ParseFiles(append(baseTemplates, renderTemplates...)...)
+			if err != nil {
+				return cache, err
+			}
+			cache[filePathBase] = ts
+		}
+	}
+
+	return cache, nil
+}