templating: Rework timers

go.mod

@@ -10,7 +10,6 @@ require (
 	github.com/gliderlabs/ssh v0.3.5
 	github.com/go-sql-driver/mysql v1.6.0
 	github.com/gorilla/csrf v1.7.1
-	github.com/gorilla/mux v1.8.0
 	github.com/gorilla/sessions v1.2.1
 	github.com/gorilla/websocket v1.5.0
 	github.com/julienschmidt/httprouter v1.3.0

go.sum

@@ -20,8 +20,6 @@ github.com/go-sql-driver/mysql v1.6.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LB
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/gorilla/csrf v1.7.1 h1:Ir3o2c1/Uzj6FBxMlAUB6SivgVMy1ONXwYgXn+/aHPE=
 github.com/gorilla/csrf v1.7.1/go.mod h1:+a/4tCmqhG6/w4oafeAZ9pEa3/NZOWYVbD9fV0FwIQA=
-github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
-github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=
 github.com/gorilla/securecookie v1.1.1 h1:miw7JPhV+b/lAHSXz4qd/nN9jRiAFV5FwjeKyCS8BvQ=
 github.com/gorilla/securecookie v1.1.1/go.mod h1:ra0sb63/xPlUeL+yeDciTfxMRAA+MP+HVt/4epWDjd4=
 github.com/gorilla/sessions v1.2.1 h1:DHd3rPN5lE3Ts3D8rKkQ8x/0kqfeNmBAaiSi+o7FsgI=
@@ -99,6 +97,7 @@ golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.4.0 h1:7mTAgkunk3fr4GAloyyCasadO6h9zSsQZbwvcaIciV4=
 golang.org/x/tools v0.4.0/go.mod h1:UE5sM2OK9E/d67R0ANs2xJizIymRP5gJU295PvKXxjQ=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

internal/dis/component/server/cron/cron.go

@@ -119,18 +119,18 @@ func (control *Cron) Start(ctx context.Context, signal <-chan struct{}) <-chan s
 		run()
 		zerolog.Ctx(ctx).Debug().Msg("Cron() beginnning scheduling")
 
-		timer := timex.NewTimer()
+		t := timex.NewTimer()
+		defer timex.ReleaseTimer(t)
 		for {
-			timex.StopTimer(timer)
-			timer.Reset(control.Config.CronInterval)
+			timex.StopTimer(t)
+			t.Reset(control.Config.CronInterval)
 
 			select {
-			case <-timer.C:
+			case <-t.C:
 				zerolog.Ctx(ctx).Debug().Msg("Cron() timer fired")
 			case <-signal:
 				zerolog.Ctx(ctx).Debug().Msg("Cron() received signal")
 			case <-ctx.Done():
-				timex.StopTimer(timer)
 				return
 			}
 

internal/dis/component/server/templating/base.go

@@ -3,6 +3,7 @@ package templating
 import (
 	"context"
 	_ "embed"
+	"encoding/json"
 	"fmt"
 	"html/template"
 	"net/http"
@@ -11,6 +12,7 @@ import (
 
 	"github.com/FAU-CDI/wisski-distillery/pkg/httpx"
 	"github.com/FAU-CDI/wisski-distillery/pkg/pools"
+	"github.com/FAU-CDI/wisski-distillery/pkg/timex"
 	"github.com/gorilla/csrf"
 	"github.com/rs/zerolog"
 )
@@ -30,8 +32,21 @@ func (tpl *Template[C]) Template() *template.Template {
 	return baseTemplate
 }
 
+// LazyContext is like the lazy context
+func (tpl *Template[C]) LazyContext(r *http.Request, f func() (C, error), funcs ...FlagFunc) (ctx *tContext[C]) {
+	ctx = tpl.context(r, funcs...)
+	ctx.startLazy(f)
+	return ctx
+}
+
 // Context generates the context to pass to an instance of the template returned by Template.
 func (tpl *Template[C]) Context(r *http.Request, c C, funcs ...FlagFunc) (ctx *tContext[C]) {
+	ctx = tpl.context(r, funcs...)
+	ctx.start(c, nil) // setup the request
+	return ctx
+}
+
+func (tpl *Template[C]) context(r *http.Request, funcs ...FlagFunc) (ctx *tContext[C]) {
 	// create a new context
 	ctx = new(tContext[C])
 
@@ -45,16 +60,9 @@ func (tpl *Template[C]) Context(r *http.Request, c C, funcs ...FlagFunc) (ctx *t
 	// generate the rest of the options
 	ctx.Runtime.Flags = ctx.Runtime.Flags.Apply(r, tpl.p.funcs...)
 	ctx.Runtime.Flags = ctx.Runtime.Flags.Apply(r, funcs...)
-
-	// if the context has a runtime flags embed, then set the field properly
-	if tpl.p.hasRuntimeFlagsEmbed {
-		reflect.ValueOf(&c).Elem().
-			FieldByName(runtimeFlagsName).
-			Set(reflect.ValueOf(ctx.Runtime))
-	}
+	ctx.updateEmbedded = tpl.p.hasRuntimeFlagsEmbed
 
 	// the main template
-	ctx.cMain = c
 	ctx.tMain = tpl.p.tpl
 
 	// the footer template
@@ -126,22 +134,62 @@ func (tw *Template[C]) HTMLHandlerWithFlags(f func(r *http.Request) (C, []FlagFu
 // Callers may not retain references beyond the invocation of the template.
 // Callers must not rely on the internal structure of this tContext.
 type tContext[C any] struct {
-	Runtime RuntimeFlags // underlying flags
+	Runtime        RuntimeFlags // underlying flags
+	updateEmbedded bool         // should we automatically update an embedded RuntimeFlags inside the context?
 
 	ctx context.Context // underlying context for render
 
 	// the main template and context
-	tMain *template.Template
-	cMain C
+	eMain    chan error // are we done?
+	cWaiting bool
+	tMain    *template.Template
+	cMain    C
 
 	// the footer template and context
 	tFooter *template.Template
 	cFooter RuntimeFlags
 }
 
+func (ctx *tContext[C]) start(c C, err error) {
+	ctx.cMain = c
+	ctx.eMain = make(chan error, 1)
+	ctx.eMain <- err
+}
+
+func (ctx *tContext[C]) startLazy(f func() (C, error)) {
+	ctx.eMain = make(chan error, 1)
+	go func() {
+		defer close(ctx.eMain)
+
+		// compute the result, storing the error
+		var err error
+		ctx.cMain, err = f()
+		ctx.eMain <- err
+	}()
+}
+
+const mainDelay = time.Second
+
 // Main renders the main template.
 func (ctx *tContext[C]) Main() (template.HTML, error) {
-	return ctx.renderSafe("main", ctx.tMain, ctx.cMain)
+	timer := timex.NewTimer()
+	defer timex.ReleaseTimer(timer)
+
+	timer.Reset(mainDelay)
+	select {
+
+	case err := <-ctx.eMain:
+		// we received the result within the given time
+		// so we can render it immediatly
+		ctx.cWaiting = false
+		return ctx.doMain(err)
+
+	case <-timer.C:
+		// the template is taking longer than expected.
+		// we should display a spinner, and do something later
+		ctx.cWaiting = true
+		return timeWait, nil
+	}
 }
 
 // Footer renders the footer template
@@ -149,6 +197,52 @@ func (ctx *tContext[C]) Footer() (template.HTML, error) {
 	return ctx.renderSafe("footer", ctx.tFooter, ctx.cFooter)
 }
 
+const (
+	timeWait   = "Loading"
+	errUnknown = "An unknown error occured, see the server log for details. "
+)
+
+func (ctx *tContext[C]) doMain(err error) (template.HTML, error) {
+	zerolog.Ctx(ctx.ctx).Info().Msg("doMain")
+	if err != nil {
+		zerolog.Ctx(ctx.ctx).Err(err).Msg("error lazy loading template")
+		return errUnknown, nil
+	}
+
+	// if the context has a runtime flags embed, then set the field properly
+	if ctx.updateEmbedded {
+		reflect.ValueOf(&ctx.cMain).Elem().
+			FieldByName(runtimeFlagsName).
+			Set(reflect.ValueOf(ctx.Runtime))
+	}
+
+	return ctx.renderSafe("main", ctx.tMain, ctx.cMain)
+}
+
+func (ctx *tContext[C]) AfterBody() (template.HTML, error) {
+	zerolog.Ctx(ctx.ctx).Info().Msg("AfterBody()")
+	// everything was done already
+	if !ctx.cWaiting {
+		return "", nil
+	}
+
+	// wait for the result to appear
+	res, err := ctx.doMain(<-ctx.eMain)
+	if err != nil {
+		return "", err
+	}
+
+	str, err := json.Marshal(string(res))
+	if err != nil {
+		return "", err
+	}
+
+	fix := "<script>document.getElementById('main').innerHTML=" + string(str) + "</script>"
+
+	// hook that is called after the body is complete
+	return template.HTML(fix), nil
+}
+
 const renderSafeError = "Error displaying page. See server log for details. "
 
 func (ctx *tContext[C]) renderSafe(name string, t *template.Template, c any) (template.HTML, error) {
@@ -170,7 +264,7 @@ func (ctx *tContext[C]) renderSafe(name string, t *template.Template, c any) (te
 					Str("uri", ctx.Runtime.RequestURI).
 					Str("name", name).
 					Str("panic", fmt.Sprint(r)).
-					Msg("templating.Main(): template panic()ed")
+					Msg("renderSafe: template panic()ed")
 			}
 		}()
 

internal/dis/component/server/templating/src/base.html

@@ -12,7 +12,7 @@
         <nav class="pure-menu pure-menu-horizontal">
             <ul class="pure-menu-list" role="menubar">
                 {{ range .Runtime.Menu }}
-                <li class="pure-menu-item{{ if .Active }} pure-menu-selected{{ end }}">
+                <li class="pure-menu-item{{ if .Active }} pure-menu-selected{{ end }}" role="menuitem">
                     <a href="{{ .Path }}" class="pure-menu-link">{{ .Title }}</a>
                 </li>
                 {{ end }}
@@ -35,7 +35,7 @@
             {{ end }}
         </header>
         <main>
-            <div class="pure-g">
+            <div class="pure-g" id="main">
                 {{ .Main }}
             </div>
         </main>
@@ -44,7 +44,7 @@
             {{ .Footer }}
         </footer>
 
-
+        {{ .AfterBody }}
         {{ .Runtime.Flags.Assets.Scripts }}
     </body>
 

pkg/cancel/anyways.go

@@ -3,6 +3,8 @@ package cancel
 import (
 	"context"
 	"time"
+
+	"github.com/FAU-CDI/wisski-distillery/pkg/timex"
 )
 
 // Anyways behaves like context.WithTimeout, except that if the Done() channel of ctx is closed before Anyways is called, the returned context's Done() channel is only closed after timeout.
@@ -22,8 +24,9 @@ func Anyways(ctx context.Context, timeout time.Duration) (context.Context, conte
 	// start waiting for the timer (or the cancel to be called)
 	finish := make(chan struct{})
 	go func() {
-		t := time.NewTimer(timeout)
-		defer t.Stop()
+		t := timex.NewTimer()
+		t.Reset(timeout)
+		defer timex.ReleaseTimer(t)
 
 		defer close(any.done)
 

pkg/httpx/html.go

@@ -3,10 +3,14 @@ package httpx
 import (
 	"html/template"
 	"net/http"
+	"time"
 
+	"github.com/FAU-CDI/wisski-distillery/pkg/timex"
 	"github.com/rs/zerolog"
 )
 
+const HTMLFlushInterval = time.Second / 10
+
 // WriteHTML writes a html response of type T to w.
 // If an error occured, writes an error response instead.
 func WriteHTML[T any](result T, err error, template *template.Template, templateName string, w http.ResponseWriter, r *http.Request) (e error) {
@@ -17,17 +21,39 @@ func WriteHTML[T any](result T, err error, template *template.Template, template
 		}
 	}()
 
+	// create a synced respone writer
+	sw := &SyncedResponseWriter{ResponseWriter: w}
+
+	done := make(chan struct{})
+	defer close(done)
+
+	// and regularly flush it until the end of the function
+	go func() {
+		timer := timex.NewTimer()
+		defer timex.ReleaseTimer(timer)
+
+		for {
+			timer.Reset(HTMLFlushInterval)
+			select {
+			case <-timer.C:
+				sw.Flush()
+			case <-done:
+				return
+			}
+		}
+	}()
+
 	// intercept any errors
-	if HTMLInterceptor.Intercept(w, r, err) {
+	if HTMLInterceptor.Intercept(sw, r, err) {
 		return nil
 	}
 
 	// write out the response as html
-	w.Header().Set("Content-Type", "text/html")
-	w.WriteHeader(http.StatusOK)
+	sw.Header().Set("Content-Type", "text/html")
+	sw.WriteHeader(http.StatusOK)
 
 	// minify html!
-	minifier := MinifyHTMLWriter(w)
+	minifier := MinifyHTMLWriter(sw)
 	defer minifier.Close()
 
 	// and return the template

pkg/httpx/sync.go

@@ -0,0 +1,47 @@
+package httpx
+
+import (
+	"net/http"
+	"sync"
+)
+
+// SyncedResponseWriter wraps a http ResponseWriter to syncronize all actions
+type SyncedResponseWriter struct {
+	m sync.Mutex
+	http.ResponseWriter
+}
+
+func (rw *SyncedResponseWriter) Header() http.Header {
+	rw.m.Lock()
+	defer rw.m.Unlock()
+
+	return rw.ResponseWriter.Header()
+}
+
+func (rw *SyncedResponseWriter) Write(data []byte) (int, error) {
+	rw.m.Lock()
+	defer rw.m.Unlock()
+
+	return rw.ResponseWriter.Write(data)
+}
+
+func (rw *SyncedResponseWriter) WriteHeader(statusCode int) {
+	rw.m.Lock()
+	defer rw.m.Unlock()
+
+	rw.ResponseWriter.WriteHeader(statusCode)
+}
+
+// Flush flushes any partial output to the underlying ResponseWriter.
+// If the wrapped ResponseWriter does not implement flush, the function performs no operation.
+func (rw *SyncedResponseWriter) Flush() {
+	f, ok := rw.ResponseWriter.(http.Flusher)
+	if !ok {
+		return
+	}
+
+	rw.m.Lock()
+	defer rw.m.Unlock()
+
+	f.Flush()
+}

pkg/timex/timex.go

@@ -3,18 +3,28 @@ package timex
 
 import (
 	"context"
+	"sync"
 	"time"
 )
 
-// NewTimer creates a new timer with undefined interval.
-// The timer is stopped.
-func NewTimer() *time.Timer {
-	timer := time.NewTimer(time.Second)
-	StopTimer(timer)
-	return timer
+var tPool = sync.Pool{
+	New: func() any {
+		timer := time.NewTimer(time.Second)
+		StopTimer(timer)
+		return timer
+	},
 }
 
-// StopTimer stops t and drains the C channel.
+// NewTimer returns an unusued timer from an internal timer pool.
+// The timer is guaranteed to be stopped; meaning a call to timer.Reset() should be made before using it.
+func NewTimer() *time.Timer {
+	return tPool.Get().(*time.Timer)
+}
+
+// StopTimer stops the given timer and drains the underlying channel.
+// This prevents it from firing, until a call to Reset() is made.
+//
+// If the timer is not running, StopTimer does nothing.
 func StopTimer(t *time.Timer) {
 	t.Stop()
 
@@ -25,6 +35,12 @@ func StopTimer(t *time.Timer) {
 	}
 }
 
+// ReleaseTimer stops t and returns it to the pool of timers.
+func ReleaseTimer(t *time.Timer) {
+	StopTimer(t)
+	tPool.Put(t)
+}
+
 // TickContext is like [time.Tick], but closes the returned channel once the context closes.
 // As such it can be recovered by the garbage collector; see [time.TickContext].
 //
@@ -34,24 +50,26 @@ func TickContext(c context.Context, d time.Duration) <-chan time.Time {
 		return nil
 	}
 
-	timer := make(chan time.Time, 1)
-	timer <- time.Now()
+	ticker := make(chan time.Time, 1)
+	ticker <- time.Now()
 	go func() {
-		t := time.NewTicker(d)
-		defer t.Stop()
-		defer close(timer)
+		defer close(ticker)
+
+		timer := NewTimer()
+		defer ReleaseTimer(timer)
 
 		for {
+			timer.Reset(d)
+
 			select {
-			case tick := <-t.C:
-				timer <- tick
+			case tick := <-timer.C:
+				ticker <- tick
 			case <-c.Done():
 				return
 			}
 		}
-
 	}()
-	return timer
+	return ticker
 }
 
 // TickUntilFunc invokes f every d until either context is closed, or f returns true.