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// Package gomponents provides components of DOM nodes for Go, that can render to an HTML Document.
// The primary interface is a Node, which has a single function Render, which should render
// the Node to a string. Furthermore, NodeFunc is a function which implements the Node interface
// by calling itself on Render.
// All DOM elements and attributes can be created by using the El and Attr functions.
// The package also provides a lot of convenience functions for creating elements and attributes
// with the most commonly used parameters. If they don't suffice, a fallback to El and Attr is always possible.
package gomponents
import (
"fmt"
"html/template"
"io"
"strings"
)
// Node is a DOM node that can Render itself to a string representation.
type Node interface {
Render() string
}
// NodeFunc is render function that is also a Node.
type NodeFunc func() string
func (n NodeFunc) Render() string {
return n()
}
// String satisfies fmt.Stringer.
func (n NodeFunc) String() string {
return n.Render()
}
// El creates an element DOM Node with a name and child Nodes.
// Use this if no convenience creator exists.
func El(name string, children ...Node) NodeFunc {
return func() string {
var b, attrString, childrenString strings.Builder
b.WriteString("<")
b.WriteString(name)
if len(children) == 0 {
b.WriteString("/>")
return b.String()
}
for _, c := range children {
if _, ok := c.(attr); ok {
attrString.WriteString(c.Render())
} else {
childrenString.WriteString(c.Render())
}
}
b.WriteString(attrString.String())
if childrenString.Len() == 0 {
b.WriteString("/>")
return b.String()
}
b.WriteString(">")
b.WriteString(childrenString.String())
b.WriteString("</")
b.WriteString(name)
b.WriteString(">")
return b.String()
}
}
// Attr creates an attr DOM Node.
// If one parameter is passed, it's a name-only attribute (like "required").
// If two parameters are passed, it's a name-value attribute (like `class="header"`).
// More parameter counts make Attr panic.
// Use this if no convenience creator exists.
func Attr(name string, value ...string) Node {
switch len(value) {
case 0:
return attr{name: name}
case 1:
return attr{name: name, value: &value[0]}
default:
panic("attribute must be just name or name and value pair")
}
}
type attr struct {
name string
value *string
}
func (a attr) Render() string {
if a.value == nil {
return fmt.Sprintf(" %v", a.name)
}
return fmt.Sprintf(` %v="%v"`, a.name, *a.value)
}
// String satisfies fmt.Stringer.
func (a attr) String() string {
return a.Render()
}
// Text creates a text DOM Node that Renders the escaped string t.
func Text(t string) NodeFunc {
return func() string {
return template.HTMLEscaper(t)
}
}
// Textf creates a text DOM Node that Renders the interpolated and escaped string t.
func Textf(format string, a ...interface{}) NodeFunc {
return func() string {
return template.HTMLEscaper(fmt.Sprintf(format, a...))
}
}
// Raw creates a raw Node that just Renders the unescaped string t.
func Raw(t string) NodeFunc {
return func() string {
return t
}
}
// Write to the given io.Writer, returning any error.
func Write(w io.Writer, n Node) error {
_, err := w.Write([]byte(n.Render()))
return err
}
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