add WASM blazor-like thing

go/cmd/examples/go-wasm-web/app/pages.go

@@ -0,0 +1,193 @@
+// Package app holds the application's pages and components as standalone
+// functions (no central App struct). It is platform-neutral, so the SAME code
+// renders on the server (SSR) and hydrates on the client.
+//
+// Directives (processed by cmd/gowasmgen at build time):
+//
+//	//gowasm:page <path> [static] [layout=<name>]
+//	                                 marks a page factory as a route. `static`
+//	                                 pre-renders it on the server (SSR);
+//	                                 `layout=<name>` wraps it in a //gowasm:layout.
+//	//gowasm:layout <name>          marks a func(Deps, *VNode) *VNode as a named
+//	                                 layout that wraps a page's content.
+//	//gowasm:server                 (see server_counter.go) marks a component
+//	                                 that runs on the server; the generated
+//	                                 client stub makes calling it identical to
+//	                                 calling any other component.
+//
+// The Routes() map, StaticPaths set, and RouteLayout/LayoutFor dispatch are all
+// generated from these directives.
+package app
+
+//go:generate go run kjol/cmd/gowasmgen .
+
+import (
+	"strconv"
+
+	. "kjol/vdom"
+)
+
+// Deps are the client-only capabilities, injected so the pages stay neutral.
+type Deps struct {
+	Path     func() string
+	Navigate func(string)
+}
+
+func itoa(n int) string { return strconv.Itoa(n) }
+
+// Layout wraps a page's rendered content with shared chrome (nav, footer, …).
+// Layouts are declared with //gowasm:layout and selected per route via a page's
+// `layout=` directive; the generated LayoutFor dispatches by name.
+type Layout func(d Deps, content *VNode) *VNode
+
+// Shell renders the current route's page inside its declared layout. `routes` is
+// the generated route table; `d.Path()` selects both the page and its layout.
+func Shell(d Deps, routes map[string]func() *VNode) *VNode {
+	path := d.Path()
+	var content *VNode
+	if page := routes[path]; page != nil {
+		content = page()
+	} else {
+		content = notFound(path)
+	}
+	return LayoutFor(d, path, content)
+}
+
+func notFound(path string) *VNode {
+	return Div(
+		H2(Attr("class", "h4 mb-3"), Text("Page not found")),
+		P(Attr("class", "text-secondary"), Text("No route matches "+path+".")),
+	)
+}
+
+// --- layouts (selected per route via `layout=` in //gowasm:page) ---------
+
+// PublicLayout is the chrome for public/marketing pages: a light navbar with a
+// call-to-action into the app, and a footer. The func(Deps, *VNode) *VNode shape
+// is what //gowasm:layout expects.
+//
+//gowasm:layout public
+func PublicLayout(d Deps, content *VNode) *VNode {
+	return Div(
+		Nav(Attr("class", "navbar navbar-expand bg-light border-bottom mb-4"),
+			Div(Attr("class", "container"),
+				A(Attr("class", "navbar-brand fw-bold"), Attr("href", "/"), navigate(d, "/"), Text("gowasm")),
+				Ul(Attr("class", "navbar-nav ms-auto align-items-center"),
+					navItem(d, "/", "Home"),
+					navItem(d, "/about", "About"),
+					Li(Attr("class", "nav-item ms-2"),
+						A(Attr("class", "btn btn-sm btn-primary"), Attr("href", "/chart"),
+							navigate(d, "/chart"), Text("Open app →"))),
+				))),
+		Main(Attr("class", "container"),
+			content,
+			Footer(Attr("class", "text-secondary small border-top mt-5 pt-3"),
+				Text("gowasm public site — a tiny Blazor-like engine in Go.")),
+		),
+	)
+}
+
+// AppLayout is the chrome for the application itself: a dark app navbar listing
+// the app's sections, plus a link back to the public site.
+//
+//gowasm:layout app
+func AppLayout(d Deps, content *VNode) *VNode {
+	return Div(
+		Nav(Attr("class", "navbar navbar-expand navbar-dark bg-dark mb-4"),
+			Div(Attr("class", "container"),
+				A(Attr("class", "navbar-brand fw-bold"), Attr("href", "/chart"), navigate(d, "/chart"), Text("gowasm · app")),
+				Ul(Attr("class", "navbar-nav me-auto"),
+					navItem(d, "/chart", "Chart"),
+					navItem(d, "/server", "Server")),
+				Ul(Attr("class", "navbar-nav"),
+					navItem(d, "/", "Home")),
+			)),
+		Main(Attr("class", "container"), content),
+	)
+}
+
+// navItem is a nav link that carries an active state on the current route.
+func navItem(d Deps, path, label string) *VNode {
+	cls := "nav-link"
+	if d.Path() == path {
+		cls += " active"
+	}
+	return Li(Attr("class", "nav-item"),
+		A(Attr("class", cls), Attr("href", path), navigate(d, path), Text(label)))
+}
+
+// navigate intercepts a link click for client-side SPA navigation. On the server
+// Navigate is nil, so the anchor falls back to a normal navigation.
+func navigate(d Deps, path string) Mod {
+	return OnEvent(EVENT_CLICK, func(e Event) {
+		if d.Navigate != nil {
+			e.PreventDefault()
+			d.Navigate(path)
+		}
+	})
+}
+
+// Counter is a presentational client component; state is owned by the caller.
+func Counter(label string, count *Signal[int]) *VNode {
+	return Div(Attr("class", "counter card mb-2"),
+		Div(Attr("class", "card-body py-2 d-flex align-items-center"),
+			Span(Attr("class", "me-2 fw-semibold"), Text(label+": ")),
+			Strong(Attr("class", "badge text-bg-primary me-2"), Text(itoa(count.Get()))),
+			Div(Attr("class", "btn-group btn-group-sm ms-auto"),
+				Button(Attr("class", "btn btn-outline-secondary"),
+					On(EVENT_CLICK, func() { count.Update(func(v int) int { return v - 1 }) }), Text("−")),
+				Button(Attr("class", "btn btn-outline-primary"),
+					On(EVENT_CLICK, func() { count.Update(func(v int) int { return v + 1 }) }), Text("+")),
+			)))
+}
+
+//gowasm:page / static layout=public
+func HomePage(d Deps) func() *VNode {
+	a := NewSignal(0)
+	b := NewSignal(0)
+	return func() *VNode {
+		return Div(
+			H2(Attr("class", "h4 mb-3"), Text("Home — component composition")),
+			P(Attr("class", "text-secondary"), Text("Two counters; the total is derived across them. Server-rendered, then hydrated.")),
+			Counter("Apples", a),
+			Counter("Bananas", b),
+			Div(Attr("class", "alert alert-info d-flex justify-content-between align-items-center mt-3"),
+				Span(Text("Combined total: ")),
+				Strong(Attr("class", "fs-5"), Text(itoa(a.Get()+b.Get())))),
+		)
+	}
+}
+
+//gowasm:page /about static layout=public
+func AboutPage(d Deps) func() *VNode {
+	return func() *VNode {
+		return Div(
+			H2(Attr("class", "h4 mb-3"), Text("About")),
+			P(Attr("class", "lead"),
+				Text("Components are standalone functions; calling a server component looks "+
+					"identical to calling a client one — the //gowasm:server directive and the "+
+					"build-time codegen wire up the round-trip. Static routes are SSR'd; the rest "+
+					"render on the client.")),
+		)
+	}
+}
+
+//gowasm:page /server layout=app
+func ServerPage(d Deps) func() *VNode {
+	// ServerCounter is a server component — but calling it is just like calling
+	// any component. On the client this resolves to a generated stub that mounts
+	// it over /rsc; on the server it's the real function. (Not `static`: the
+	// client renders the stub, which round-trips, so there's nothing stable to
+	// pre-render + hydrate.)
+	counter := ServerCounter()
+	return func() *VNode {
+		return Div(
+			H2(Attr("class", "h4 mb-3"), Text("Server component")),
+			P(Attr("class", "text-secondary"),
+				Text("This counter runs on the server. Its state lives there; clicks round-trip "+
+					"and the returned render merges into the DOM. The call site is identical to a "+
+					"client component.")),
+			counter(),
+		)
+	}
+}