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elem.go
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package elem
import (
"fmt"
"sort"
"strings"
"github.com/chasefleming/elem-go/attrs"
)
// List of HTML5 void elements. Void elements, also known as self-closing or empty elements,
// are elements that don't have a closing tag because they can't contain any content.
// For example, the <img> tag cannot wrap text or other tags, it stands alone, so it doesn't have a closing tag.
var voidElements = map[string]struct{}{
"area": {},
"base": {},
"br": {},
"col": {},
"command": {},
"embed": {},
"hr": {},
"img": {},
"input": {},
"keygen": {},
"link": {},
"meta": {},
"param": {},
"source": {},
"track": {},
"wbr": {},
}
// List of boolean attributes. Boolean attributes can't have literal values. The presence of an boolean
// attribute represents the "true" value. To represent the "false" value, the attribute has to be omitted.
// See https://html.spec.whatwg.org/multipage/indices.html#attributes-3 for reference
var booleanAttrs = map[string]struct{}{
attrs.AllowFullscreen: {},
attrs.Async: {},
attrs.Autofocus: {},
attrs.Autoplay: {},
attrs.Checked: {},
attrs.Controls: {},
attrs.Defer: {},
attrs.Disabled: {},
attrs.Ismap: {},
attrs.Loop: {},
attrs.Multiple: {},
attrs.Muted: {},
attrs.Novalidate: {},
attrs.Open: {},
attrs.Playsinline: {},
attrs.Readonly: {},
attrs.Required: {},
attrs.Selected: {},
}
type CSSGenerator interface {
GenerateCSS() string // TODO: Change to CSS()
}
type RenderOptions struct {
// DisableHtmlPreamble disables the doctype preamble for the HTML tag if it exists in the rendering tree
DisableHtmlPreamble bool
StyleManager CSSGenerator
}
type Node interface {
RenderTo(builder *strings.Builder, opts RenderOptions)
Render() string
RenderWithOptions(opts RenderOptions) string
}
// NoneNode represents a node that renders nothing.
type NoneNode struct{}
// RenderTo for NoneNode does nothing.
func (n NoneNode) RenderTo(builder *strings.Builder, opts RenderOptions) {
// Intentionally left blank to render nothing
}
// Render for NoneNode returns an empty string.
func (n NoneNode) Render() string {
return ""
}
// RenderWithOptions for NoneNode returns an empty string.
func (n NoneNode) RenderWithOptions(opts RenderOptions) string {
return ""
}
type TextNode string
func (t TextNode) RenderTo(builder *strings.Builder, opts RenderOptions) {
builder.WriteString(string(t))
}
func (t TextNode) Render() string {
return string(t)
}
func (t TextNode) RenderWithOptions(opts RenderOptions) string {
return string(t)
}
type RawNode string
func (r RawNode) RenderTo(builder *strings.Builder, opts RenderOptions) {
builder.WriteString(string(r))
}
func (r RawNode) Render() string {
return string(r)
}
func (t RawNode) RenderWithOptions(opts RenderOptions) string {
return string(t)
}
type CommentNode string
func (c CommentNode) RenderTo(builder *strings.Builder, opts RenderOptions) {
builder.WriteString("<!-- ")
builder.WriteString(string(c))
builder.WriteString(" -->")
}
func (c CommentNode) Render() string {
return c.RenderWithOptions(RenderOptions{})
}
func (c CommentNode) RenderWithOptions(opts RenderOptions) string {
var builder strings.Builder
c.RenderTo(&builder, opts)
return builder.String()
}
type Element struct {
Tag string
Attrs attrs.Props
Children []Node
}
func (e *Element) RenderTo(builder *strings.Builder, opts RenderOptions) {
// The HTML tag needs a doctype preamble in order to ensure
// browsers don't render in legacy/quirks mode
// https://developer.mozilla.org/en-US/docs/Glossary/Doctype
if !opts.DisableHtmlPreamble && e.Tag == "html" {
builder.WriteString("<!DOCTYPE html>")
}
isFragment := e.Tag == "fragment"
// Start with opening tag
if !isFragment {
builder.WriteString("<")
builder.WriteString(e.Tag)
}
// Sort the keys for consistent order
keys := make([]string, 0, len(e.Attrs))
for k := range e.Attrs {
keys = append(keys, k)
}
sort.Strings(keys)
// Append the attributes to the builder
for _, k := range keys {
e.renderAttrTo(k, builder)
}
// If it's a void element, close it and return
if _, exists := voidElements[e.Tag]; exists {
builder.WriteString(`>`)
return
}
if !isFragment {
// Close opening tag
builder.WriteString(`>`)
}
// Build the content
for _, child := range e.Children {
child.RenderTo(builder, opts)
}
if !isFragment {
// Append closing tag
builder.WriteString(`</`)
builder.WriteString(e.Tag)
builder.WriteString(`>`)
}
}
// return string representation of given attribute with its value
func (e *Element) renderAttrTo(attrName string, builder *strings.Builder) {
if _, exists := booleanAttrs[attrName]; exists {
// boolean attribute presents its name only if the value is "true"
if e.Attrs[attrName] == "true" {
builder.WriteString(` `)
builder.WriteString(attrName)
}
} else {
// regular attribute has a name and a value
attrVal := e.Attrs[attrName]
// A necessary check to to avoid adding extra quotes around values that are already single-quoted
// An example is '{"quantity": 5}'
isSingleQuoted := strings.HasPrefix(attrVal, "'") && strings.HasSuffix(attrVal, "'")
builder.WriteString(` `)
builder.WriteString(attrName)
builder.WriteString(`=`)
if !isSingleQuoted {
builder.WriteString(`"`)
}
builder.WriteString(attrVal)
if !isSingleQuoted {
builder.WriteString(`"`)
}
}
}
func (e *Element) Render() string {
return e.RenderWithOptions(RenderOptions{})
}
func (e *Element) RenderWithOptions(opts RenderOptions) string {
var builder strings.Builder
e.RenderTo(&builder, opts)
if opts.StyleManager != nil {
htmlContent := builder.String()
cssContent := opts.StyleManager.GenerateCSS()
// Define the <style> element with the generated CSS content
styleElement := fmt.Sprintf("<style>%s</style>", cssContent)
// Check if a <head> tag exists in the HTML content
headStartIndex := strings.Index(htmlContent, "<head>")
headEndIndex := strings.Index(htmlContent, "</head>")
if headStartIndex != -1 && headEndIndex != -1 {
// If <head> exists, inject the style content just before </head>
beforeHead := htmlContent[:headEndIndex]
afterHead := htmlContent[headEndIndex:]
modifiedHTML := beforeHead + styleElement + afterHead
return modifiedHTML
} else {
// If <head> does not exist, create it and inject the style content
// Assuming <html> tag exists and injecting <head> immediately after <html>
htmlTagEnd := strings.Index(htmlContent, ">") + 1
if htmlTagEnd > 0 {
beforeHTML := htmlContent[:htmlTagEnd]
afterHTML := htmlContent[htmlTagEnd:]
modifiedHTML := beforeHTML + "<head>" + styleElement + "</head>" + afterHTML
return modifiedHTML
}
}
}
// Return the original HTML content if no modifications were made
return builder.String()
}
func newElement(tag string, attrs attrs.Props, children ...Node) *Element {
return &Element{
Tag: tag,
Attrs: attrs,
Children: children,
}
}