feat: add working prototype for via

via.go

@@ -0,0 +1,224 @@
+// Package via provides a reactive web framework for Go.
+// It lets you build live, type-safe web interfaces without JavaScript.
+//
+// Via unifies routing, state, and UI reactivity through a simple mental model:
+// Go on the server — HTML in the browser — updated in real time via Datastar.
+package via
+
+import (
+	"crypto/rand"
+	_ "embed"
+	"encoding/hex"
+	"fmt"
+	"log"
+	"net/http"
+	"sync"
+
+	"github.com/go-via/via/h"
+	"github.com/starfederation/datastar-go/datastar"
+)
+
+//go:embed datastar.js
+var datastarJS []byte
+
+type config struct {
+	logLvl LogLevel
+}
+
+type LogLevel int
+
+const (
+	LogLevelError LogLevel = iota
+	LogLevelWarn
+	LogLevelInfo
+	LogLevelDebug
+)
+
+// via is the root application.
+// It manages page routing, user sessions, and SSE connections for live updates.
+type via struct {
+	cfg                  config
+	mux                  *http.ServeMux
+	contextRegistry      map[string]*Context
+	contextRegistryMutex sync.RWMutex
+	baseLayout           func(h.HTML5Props) h.H
+}
+
+func (v *via) logErr(c *Context, format string, a ...any) {
+	cRef := ""
+	if c != nil && c.id != "" {
+		cRef = fmt.Sprintf("via-ctx=%q ", c.id)
+	}
+	log.Printf("[error] %smsg=%q", cRef, fmt.Sprintf(format, a...))
+}
+
+func (v *via) logWarn(c *Context, format string, a ...any) {
+	cRef := ""
+	if c != nil && c.id != "" {
+		cRef = fmt.Sprintf("via-ctx=%q ", c.id)
+	}
+	if v.cfg.logLvl <= LogLevelWarn {
+		log.Printf("[warn] %smsg=%q", cRef, fmt.Sprintf(format, a...))
+	}
+}
+
+func (v *via) logInfo(c *Context, format string, a ...any) {
+	cRef := ""
+	if c != nil && c.id != "" {
+		cRef = fmt.Sprintf("via-ctx=%q ", c.id)
+	}
+	if v.cfg.logLvl >= LogLevelInfo {
+		log.Printf("[info] %smsg=%q", cRef, fmt.Sprintf(format, a...))
+	}
+}
+
+func (v *via) logDebug(c *Context, format string, a ...any) {
+	cRef := ""
+	if c != nil && c.id != "" {
+		cRef = fmt.Sprintf("via-ctx=%q ", c.id)
+	}
+	if v.cfg.logLvl == LogLevelDebug {
+		log.Printf("[debug] %smsg=%q", cRef, fmt.Sprintf(format, a...))
+	}
+}
+
+// Page registers a route and its associated page handler.
+// The handler receives a *Context to define UI, signals, and actions.
+//
+// Example:
+//
+//	v.Page("/", func(c *via.Context) {
+//		c.View(func() h.H {
+//			return h.H1(h.Text("Hello, Via!"))
+//		})
+//	})
+func (v *via) Page(route string, composeContext func(c *Context)) {
+	v.mux.HandleFunc("GET "+route, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		id := fmt.Sprintf("%s_/%s", route, genRandID())
+		c := newContext(id, v)
+		v.logDebug(c, "GET %s", route)
+		composeContext(c)
+		v.registerCtx(c.id, c)
+		// viewFn := c.view
+		// viewFnWithID := func() h.H {
+		// 	return h.Div(h.ID(c.id), viewFn())
+		// }
+		// c.view = viewFnWithID
+		view := v.baseLayout(h.HTML5Props{
+			Head: []h.H{
+				h.Meta(h.Data("signals", fmt.Sprintf("{'via-ctx':'%s'}", id))),
+				h.Meta(h.Data("init", "@get('/_sse')")),
+			},
+			Body: []h.H{h.Div(h.ID(c.id))},
+		})
+		_ = view.Render(w)
+	}))
+}
+
+func (v *via) registerCtx(id string, c *Context) {
+	v.contextRegistryMutex.Lock()
+	defer v.contextRegistryMutex.Unlock()
+	v.contextRegistry[id] = c
+}
+
+// func (a *App) unregisterCtx(id string) {
+// 	if _, ok := a.contextRegistry[id]; ok {
+// 		a.contextRegistryMutex.Lock()
+// 		defer a.contextRegistryMutex.Unlock()
+// 		delete(a.contextRegistry, id)
+// 	}
+// }
+
+func (v *via) getCtx(id string) (*Context, error) {
+	if c, ok := v.contextRegistry[id]; ok {
+		return c, nil
+	}
+	return nil, fmt.Errorf("ctx '%s' not found", id)
+}
+
+// Start starts the Via HTTP server on the given address.
+func (v *via) Start(addr string) {
+	v.logInfo(nil, "via started")
+	log.Fatalf("via failed: %v", http.ListenAndServe(addr, v.mux))
+}
+
+// New creates a new Via application with default configuration.
+func New() *via {
+	mux := http.NewServeMux()
+	app := &via{
+		mux:             mux,
+		contextRegistry: make(map[string]*Context),
+		cfg:             config{logLvl: LogLevelDebug},
+		baseLayout:      h.HTML5,
+	}
+
+	app.mux.HandleFunc("GET /favicon.ico", func(w http.ResponseWriter, r *http.Request) {})
+
+	app.mux.HandleFunc("GET /_datastar.js", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/javascript")
+		_, _ = w.Write(datastarJS)
+	})
+
+	app.mux.HandleFunc("GET /_sse", func(w http.ResponseWriter, r *http.Request) {
+		var sigs map[string]any
+		_ = datastar.ReadSignals(r, &sigs)
+		cID, _ := sigs["via-ctx"].(string)
+		c, err := app.getCtx(cID)
+		if err != nil {
+			app.logErr(nil, "failed to render page: %v", err)
+			return
+		}
+		c.sse = datastar.NewSSE(w, r)
+		app.logDebug(c, "SSE connection established")
+		c.Sync()
+		<-c.sse.Context().Done()
+		c.sse = nil
+		app.logDebug(c, "SSE connection closed")
+	})
+	app.mux.HandleFunc("GET /_action/{id}", func(w http.ResponseWriter, r *http.Request) {
+		actionID := r.PathValue("id")
+		var sigs map[string]any
+		_ = datastar.ReadSignals(r, &sigs)
+		cID, _ := sigs["via-ctx"].(string)
+		app.logDebug(nil, "GET /_action/%s via-ctx=%s", actionID, cID)
+		active_ctx_count := 0
+		inactive_ctx_count := 0
+		for _, c := range app.contextRegistry {
+			if c.sse != nil {
+				active_ctx_count++
+				continue
+			}
+			inactive_ctx_count++
+		}
+		app.logDebug(nil, "active_ctx_count=%d inactive_ctx_count=%d", active_ctx_count, inactive_ctx_count)
+		c, err := app.getCtx(cID)
+		if err != nil {
+			app.logErr(nil, "action '%s' failed: %v", actionID, err)
+			return
+		}
+		actionFn, err := c.getActionFn(actionID)
+		if err != nil {
+			app.logDebug(c, "action '%s' failed: %v", actionID, err)
+			return
+		}
+		// log err if actionFn panics
+		defer func() {
+			if r := recover(); r != nil {
+				app.logErr(c, "action '%s' failed: %v", actionID, r)
+			}
+		}()
+		c.signalsMux.Lock()
+		defer c.signalsMux.Unlock()
+		app.logDebug(c, "signals=%v", sigs)
+		c.injectSignals(sigs)
+		actionFn()
+
+	})
+	return app
+}
+
+func genRandID() string {
+	b := make([]byte, 16)
+	rand.Read(b)
+	return hex.EncodeToString(b)[:8]
+}