go-html/node.go

package html

import (
	"html"
	"iter"
	"maps"
	"slices"
	"strconv"
	"strings"

	i18n "dappco.re/go/core/i18n"
)

// node.go: Node is anything renderable.
// Example: El("p", Text("page.body")) returns a Node that can be passed to Render().
type Node interface {
	Render(ctx *Context) string
}

// Compile-time interface checks.
var (
	_ Node = (*rawNode)(nil)
	_ Node = (*elNode)(nil)
	_ Node = (*textNode)(nil)
	_ Node = (*ifNode)(nil)
	_ Node = (*unlessNode)(nil)
	_ Node = (*entitledNode)(nil)
	_ Node = (*switchNode)(nil)
	_ Node = (*eachNode[any])(nil)
)

// renderNode renders a node while treating nil values as empty output.
func renderNode(n Node, ctx *Context) string {
	if n == nil {
		return ""
	}
	return n.Render(normaliseContext(ctx))
}

// renderNodeWithPath renders a node while preserving layout path prefixes for
// nested layouts that may be wrapped in conditional or switch nodes.
func renderNodeWithPath(n Node, ctx *Context, path string) string {
	if n == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	switch t := n.(type) {
	case *Layout:
		if t == nil {
			return ""
		}
		clone := *t
		clone.path = path
		return clone.Render(ctx)
	case interface{ renderWithPath(*Context, string) string }:
		return t.renderWithPath(ctx, path)
	case *ifNode:
		if t == nil || t.cond == nil || t.node == nil {
			return ""
		}
		if t.cond(ctx) {
			return renderNodeWithPath(t.node, ctx, path)
		}
		return ""
	case *unlessNode:
		if t == nil || t.cond == nil || t.node == nil {
			return ""
		}
		if !t.cond(ctx) {
			return renderNodeWithPath(t.node, ctx, path)
		}
		return ""
	case *entitledNode:
		if t == nil || t.node == nil {
			return ""
		}
		if ctx == nil || ctx.Entitlements == nil || !ctx.Entitlements(t.feature) {
			return ""
		}
		return renderNodeWithPath(t.node, ctx, path)
	case *switchNode:
		if t == nil || t.selector == nil || t.cases == nil {
			return ""
		}
		key := t.selector(ctx)
		if node, ok := t.cases[key]; ok {
			return renderNodeWithPath(node, ctx, path)
		}
		return ""
	default:
		return n.Render(ctx)
	}
}

// voidElements is the set of HTML elements that must not have a closing tag.
var voidElements = map[string]bool{
	"area":   true,
	"base":   true,
	"br":     true,
	"col":    true,
	"embed":  true,
	"hr":     true,
	"img":    true,
	"input":  true,
	"link":   true,
	"meta":   true,
	"source": true,
	"track":  true,
	"wbr":    true,
}

// escapeAttr escapes a string for use in an HTML attribute value.
func escapeAttr(s string) string {
	return html.EscapeString(s)
}

// --- rawNode ---

type rawNode struct {
	content string
}

// node.go: Raw creates a node that renders without escaping.
// Example: Raw("<strong>trusted</strong>") preserves the HTML verbatim.
func Raw(content string) Node {
	return &rawNode{content: content}
}

func (n *rawNode) Render(_ *Context) string {
	if n == nil {
		return ""
	}
	return n.content
}

// --- elNode ---

type elNode struct {
	tag      string
	children []Node
	attrs    map[string]string
}

// node.go: El creates an HTML element node with children.
// Example: El("nav", Text("nav.label")) renders a semantic element with nested nodes.
func El(tag string, children ...Node) Node {
	return &elNode{
		tag:      tag,
		children: children,
		attrs:    make(map[string]string),
	}
}

// node.go: Attr sets an attribute on an El node and returns the same node for chaining.
// Example: Attr(El("img"), "alt", "Logo") adds an escaped alt attribute.
//
// It recursively traverses wrappers like If, Unless, Entitled, Switch,
// and Each/EachSeq so the attribute lands on the rendered element.
func Attr(n Node, key, value string) Node {
	switch t := n.(type) {
	case *elNode:
		t.attrs[key] = value
	case *ifNode:
		Attr(t.node, key, value)
	case *unlessNode:
		Attr(t.node, key, value)
	case *entitledNode:
		Attr(t.node, key, value)
	case *switchNode:
		for caseKey, caseNode := range t.cases {
			t.cases[caseKey] = Attr(caseNode, key, value)
		}
	case interface{ setAttr(string, string) }:
		t.setAttr(key, value)
	}
	return n
}

// node.go: AriaLabel sets the aria-label attribute on an element node.
// Example: AriaLabel(El("button"), "Open menu").
func AriaLabel(n Node, label string) Node {
	return Attr(n, "aria-label", label)
}

// node.go: AriaDescribedBy sets the aria-describedby attribute on an element node.
// Example: AriaDescribedBy(El("input"), "help-text", "error-text").
// Multiple IDs are joined with spaces, matching the HTML attribute format.
func AriaDescribedBy(n Node, ids ...string) Node {
	return Attr(n, "aria-describedby", strings.Join(ids, " "))
}

// node.go: AriaLabelledBy sets the aria-labelledby attribute on an element node.
// Example: AriaLabelledBy(El("section"), "section-title").
// Multiple IDs are joined with spaces, matching the HTML attribute format.
func AriaLabelledBy(n Node, ids ...string) Node {
	return Attr(n, "aria-labelledby", strings.Join(ids, " "))
}

// node.go: AriaControls sets the aria-controls attribute on an element node.
// Example: AriaControls(El("button"), "menu-panel").
// Multiple IDs are joined with spaces, matching the HTML attribute format.
func AriaControls(n Node, ids ...string) Node {
	return Attr(n, "aria-controls", strings.Join(ids, " "))
}

// node.go: AriaCurrent sets the aria-current attribute on an element node.
// Example: AriaCurrent(El("a"), "page").
// An empty value leaves the node unchanged so callers can opt out cleanly.
func AriaCurrent(n Node, current string) Node {
	if current == "" {
		return n
	}
	return Attr(n, "aria-current", current)
}

// node.go: AriaBusy sets the aria-busy attribute on an element node.
// Example: AriaBusy(El("section"), true).
func AriaBusy(n Node, busy bool) Node {
	if busy {
		return Attr(n, "aria-busy", "true")
	}
	return Attr(n, "aria-busy", "false")
}

// node.go: AriaLive sets the aria-live attribute on an element node.
// Example: AriaLive(El("div"), "polite").
// An empty value leaves the node unchanged so callers can opt out cleanly.
func AriaLive(n Node, live string) Node {
	if live == "" {
		return n
	}
	return Attr(n, "aria-live", live)
}

// node.go: Role sets the role attribute on an element node.
// Example: Role(El("aside"), "complementary").
func Role(n Node, role string) Node {
	return Attr(n, "role", role)
}

// node.go: Lang sets the lang attribute on an element node.
// Example: Lang(El("html"), "en-GB").
func Lang(n Node, locale string) Node {
	return Attr(n, "lang", locale)
}

// node.go: Dir sets the dir attribute on an element node.
// Example: Dir(El("p"), "rtl").
func Dir(n Node, direction string) Node {
	return Attr(n, "dir", direction)
}

// node.go: Alt sets the alt attribute on an element node.
// Example: Alt(El("img"), "Product screenshot").
func Alt(n Node, text string) Node {
	return Attr(n, "alt", text)
}

// node.go: AltText sets the alt attribute on an element node.
// Example: AltText(El("img"), "Product screenshot").
func AltText(n Node, text string) Node {
	return Alt(n, text)
}

// node.go: Class sets the class attribute on an element node.
// Example: Class(El("div"), "card", "card--primary").
// Multiple class tokens are joined with spaces.
func Class(n Node, classes ...string) Node {
	return Attr(n, "class", strings.Join(classes, " "))
}

// node.go: AriaHidden sets the aria-hidden attribute on an element node.
// Example: AriaHidden(El("svg"), true).
func AriaHidden(n Node, hidden bool) Node {
	if hidden {
		return Attr(n, "aria-hidden", "true")
	}
	return n
}

// node.go: AriaExpanded sets the aria-expanded attribute on an element node.
// Example: AriaExpanded(El("button"), true).
func AriaExpanded(n Node, expanded bool) Node {
	if expanded {
		return Attr(n, "aria-expanded", "true")
	}
	return Attr(n, "aria-expanded", "false")
}

// node.go: AriaDisabled sets the aria-disabled attribute on an element node.
// Example: AriaDisabled(El("button"), true).
func AriaDisabled(n Node, disabled bool) Node {
	if disabled {
		return Attr(n, "aria-disabled", "true")
	}
	return Attr(n, "aria-disabled", "false")
}

// node.go: AriaPressed sets the aria-pressed attribute on an element node.
// Example: AriaPressed(El("button"), true).
func AriaPressed(n Node, pressed bool) Node {
	if pressed {
		return Attr(n, "aria-pressed", "true")
	}
	return Attr(n, "aria-pressed", "false")
}

// node.go: AriaSelected sets the aria-selected attribute on an element node.
// Example: AriaSelected(El("option"), true).
func AriaSelected(n Node, selected bool) Node {
	if selected {
		return Attr(n, "aria-selected", "true")
	}
	return Attr(n, "aria-selected", "false")
}

// node.go: TabIndex sets the tabindex attribute on an element node.
// Example: TabIndex(El("button"), 0).
func TabIndex(n Node, index int) Node {
	return Attr(n, "tabindex", strconv.Itoa(index))
}

// node.go: AutoFocus sets the autofocus attribute on an element node.
// Example: AutoFocus(El("input")).
func AutoFocus(n Node) Node {
	return Attr(n, "autofocus", "autofocus")
}

func (n *elNode) Render(ctx *Context) string {
	if n == nil {
		return ""
	}

	return n.renderWithPath(normaliseContext(ctx), "")
}

func (n *elNode) renderWithPath(ctx *Context, path string) string {
	if n == nil {
		return ""
	}

	var b strings.Builder

	b.WriteByte('<')
	b.WriteString(escapeHTML(n.tag))

	// Sort attribute keys for deterministic output.
	keys := slices.Collect(maps.Keys(n.attrs))
	slices.Sort(keys)
	for _, key := range keys {
		b.WriteByte(' ')
		b.WriteString(escapeHTML(key))
		b.WriteString(`="`)
		b.WriteString(escapeAttr(n.attrs[key]))
		b.WriteByte('"')
	}

	b.WriteByte('>')

	if voidElements[n.tag] {
		return b.String()
	}

	for i := range len(n.children) {
		b.WriteString(renderNodeWithPath(n.children[i], ctx, path))
	}

	b.WriteString("</")
	b.WriteString(escapeHTML(n.tag))
	b.WriteByte('>')

	return b.String()
}

// --- escapeHTML ---

// escapeHTML escapes a string for safe inclusion in HTML text content.
func escapeHTML(s string) string {
	return html.EscapeString(s)
}

// --- textNode ---

type textNode struct {
	key  string
	args []any
}

// node.go: Text creates a node that renders through the go-i18n grammar pipeline.
// Example: Text("page.title") renders translated text and escapes it for HTML.
// Output is HTML-escaped by default. Safe-by-default path.
func Text(key string, args ...any) Node {
	return &textNode{key: key, args: args}
}

func (n *textNode) Render(ctx *Context) string {
	if n == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	var text string
	if ctx.service != nil {
		text = ctx.service.T(n.key, n.args...)
	} else {
		text = i18n.T(n.key, n.args...)
	}
	return escapeHTML(text)
}

// --- ifNode ---

type ifNode struct {
	cond func(*Context) bool
	node Node
}

// node.go: If renders child only when condition is true.
// Example: If(func(*Context) bool { return true }, Raw("shown")).
func If(cond func(*Context) bool, node Node) Node {
	return &ifNode{cond: cond, node: node}
}

func (n *ifNode) Render(ctx *Context) string {
	if n == nil || n.cond == nil || n.node == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	if n.cond(ctx) {
		return renderNodeWithPath(n.node, ctx, "")
	}
	return ""
}

// --- unlessNode ---

type unlessNode struct {
	cond func(*Context) bool
	node Node
}

// node.go: Unless renders child only when condition is false.
// Example: Unless(func(*Context) bool { return true }, Raw("hidden")).
func Unless(cond func(*Context) bool, node Node) Node {
	return &unlessNode{cond: cond, node: node}
}

func (n *unlessNode) Render(ctx *Context) string {
	if n == nil || n.cond == nil || n.node == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	if !n.cond(ctx) {
		return renderNodeWithPath(n.node, ctx, "")
	}
	return ""
}

// --- entitledNode ---

type entitledNode struct {
	feature string
	node    Node
}

// node.go: Entitled renders child only when entitlement is granted.
// Example: Entitled("premium", Raw("paid feature")).
// Content is absent, not hidden. If no entitlement function is set on the
// context, access is denied by default.
func Entitled(feature string, node Node) Node {
	return &entitledNode{feature: feature, node: node}
}

func (n *entitledNode) Render(ctx *Context) string {
	if n == nil || n.node == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	if ctx.Entitlements == nil || !ctx.Entitlements(n.feature) {
		return ""
	}
	return renderNodeWithPath(n.node, ctx, "")
}

// --- switchNode ---

type switchNode struct {
	selector func(*Context) string
	cases    map[string]Node
}

// node.go: Switch renders based on runtime selector value.
// Example: Switch(selector, map[string]Node{"desktop": Raw("wide")}).
func Switch(selector func(*Context) string, cases map[string]Node) Node {
	return &switchNode{selector: selector, cases: cases}
}

func (n *switchNode) Render(ctx *Context) string {
	if n == nil || n.selector == nil || n.cases == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	key := n.selector(ctx)
	if node, ok := n.cases[key]; ok {
		return renderNodeWithPath(node, ctx, "")
	}
	return ""
}

// --- eachNode ---

type eachNode[T any] struct {
	items iter.Seq[T]
	fn    func(T) Node
}

// node.go: Each iterates items and renders each via fn.
// Example: Each(items, func(item Item) Node { return El("li", Text(item.Name)) }).
func Each[T any](items []T, fn func(T) Node) Node {
	return EachSeq(slices.Values(items), fn)
}

// node.go: EachSeq iterates an iter.Seq and renders each via fn.
// Example: EachSeq(slices.Values(items), renderItem).
func EachSeq[T any](items iter.Seq[T], fn func(T) Node) Node {
	return &eachNode[T]{items: items, fn: fn}
}

func (n *eachNode[T]) Render(ctx *Context) string {
	if n == nil || n.items == nil || n.fn == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	var b strings.Builder
	for item := range n.items {
		b.WriteString(renderNodeWithPath(n.fn(item), ctx, ""))
	}
	return b.String()
}

func (n *eachNode[T]) renderWithPath(ctx *Context, path string) string {
	if n == nil || n.items == nil || n.fn == nil {
		return ""
	}

	var b strings.Builder
	for item := range n.items {
		b.WriteString(renderNodeWithPath(n.fn(item), ctx, path))
	}
	return b.String()
}

func (n *eachNode[T]) setAttr(key, value string) {
	if n == nil || n.fn == nil {
		return
	}

	prev := n.fn
	n.fn = func(item T) Node {
		return Attr(prev(item), key, value)
	}
}