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Smooth route click (#9)

Browse Source 
* misc

* Ugly, but works!

* refactor server

* better names

* document the server logic

* Remove refreshPage, no longer used

* refactor ws client
This commit is contained in:
Sridhar Ratnakumar 2021-04-22 10:34:01 -04:00 committed by GitHub
parent 0f3f2b5932
commit 7c7df0cb63
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3 changed files with 84 additions and 45 deletions
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2
bin/run-via-tmux
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@ -1,4 +1,4 @@
#!/usr/bin/env bash
set -xe
PROJECT=$(basename `pwd`)
tmux new-session -A -s $PROJECT bin/run
exec tmux new-session -A -s $PROJECT bin/run

8
src/Ema/Example/Ex03_Diary.hs
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@ -110,7 +110,7 @@ mainWith folder = do
render :: Diary -> Route -> LByteString
render diary r = do
Tailwind.layout (H.title "My Diary") $
Tailwind.layout (H.title pageTitle) $
H.div ! A.class_ "container mx-auto" $ do
let heading =
H.header
@ -125,7 +125,13 @@ render diary r = do
heading $ show day
routeElem Index "Back to Index"
maybe "not found" renderOrg (Map.lookup day diary)
H.footer ! A.class_ "mt-2 text-center border-t-2 text-gray-500" $ do
"Powered by "
H.a ! A.href "https://github.com/srid/ema" ! A.target "blank_" $ "Ema"
where
pageTitle = case r of
Index -> "My Diary"
OnDay day -> show day <> " -- My Diary"
routeElem r' w =
H.a ! A.class_ "text-xl text-purple-500 hover:underline" ! routeHref r' $ w
routeHref r' =

109
src/Ema/Server.hs
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@ -4,6 +4,7 @@
-- | TODO: Refactor this module
module Ema.Server where
import Control.Concurrent.Async (race)
import Control.Exception (try)
import Data.LVar (LVar)
import qualified Data.LVar as LVar
@ -33,18 +34,41 @@ runServerWithWebSocketHotReload port model render = do
WS.withPingThread conn 30 (pure ()) $ do
subId <- LVar.addListener model
let log s = putTextLn $ "[" <> show subId <> "] :: " <> s
log "ws connected"
let loop = do
msg <- WS.receiveData conn
let r :: route =
log "ws:connected"
let askClientForRoute = do
msg :: Text <- WS.receiveData conn
pure $
msg
& pathInfoFromWsMsg
& routeFromPathInfo
& fromMaybe (error "invalid route from ws")
log $ "Browser requests next HTML for: " <> show r
val <- LVar.listenNext model subId
WS.sendTextData conn $ routeHtml val r
log $ "Sent HTML for " <> show r
loop = do
-- Notice that we @askClientForRoute@ in succession twice here.
-- The first route will be the route the client intends to observe
-- for changes on. The second route, *if* it is sent, indicates
-- that the client wants to *switch* to that route. This proecess
-- repeats ad infinitum: i.e., the third route is for observing
-- changes, the fourth route is for switching to, and so on.
watchingRoute <- askClientForRoute
log $ "[Watch]: <~~ " <> show watchingRoute
-- Listen *until* either we get a new value, or the client requests
-- to switch to a new route.
race (LVar.listenNext model subId) askClientForRoute >>= \case
Left newHtml -> do
-- The page the user is currently viewing has changed. Send
-- the new HTML to them.
WS.sendTextData conn $ routeHtml newHtml watchingRoute
log $ "[Watch]: ~~> " <> show watchingRoute
loop
Right nextRoute -> do
-- The user clicked on a route link; send them the HTML for
-- that route this time, ignoring what we are watching
-- currently (we expect the user to initiate a watch route
-- request immediately following this).
log $ "[Switch]: <~~ " <> show nextRoute
html <- LVar.get model
WS.sendTextData conn $ routeHtml html nextRoute
log $ "[Switch]: ~~> " <> show nextRoute
loop
try loop >>= \case
Right () -> pure ()
@ -77,6 +101,11 @@ wsClientShim =
encodeUtf8
[text|
<script type="module">
// Replace the DOM with a new raw HTML
//
// This function tries to trigger evaluation of <script> tags in the
// HTML, but for some reason it doesn't seem to work reliably.
// cf. the shims in Ema.Helper.Tailwind
// https://stackoverflow.com/a/47614491/55246
function setInnerHtml(elm, html) {
elm.innerHTML = html;
@ -89,29 +118,6 @@ wsClientShim =
});
}
// Unused, right now.
function refreshPage() {
// The setTimeout is necessary, otherwise reload will hang forever (at
// least on Brave browser)
//
// The delayedRefresh trick (5000 and 2000) is for cases when the
// server hasn't reloaded fast enough, but the browser hangs forever
// in reload refresh state.
//
// FIXME: This is not enough. Cancel and retry the reload, as it is
// normal to have longer sessions of ghcid in error state while the
// user fixes their code.
setTimeout(function() {
window.location.reload();
}, 5000);
setTimeout(function() {
window.location.reload();
}, 2000);
setTimeout(function() {
window.location.reload();
}, 100);
};
// Ema Status indicator
const messages = {
connected: "Connected",
@ -138,7 +144,7 @@ wsClientShim =
document.getElementById("ema-indicator").style.display = "none";
};
// WebSocket logic
// WebSocket logic: watching for server changes & route switching
function init() {
console.log("ema: Opening ws conn");
window.connecting();
@ -146,29 +152,56 @@ wsClientShim =
// Call this, then the server will send update *once*. Call again for
// continous monitoring.
function watchRoute() {
function watchCurrentRoute() {
console.log(`ema: ⏿ Observing changes to $${document.location.pathname}`);
ws.send(document.location.pathname);
};
function switchRoute(path) {
console.log(`ema: → Switching to $${path}`);
ws.send(path);
}
ws.onopen = () => {
// window.connected();
window.hideIndicator();
console.log("ema: Observing server for changes");
watchRoute();
watchCurrentRoute();
};
ws.onclose = () => {
console.log("ema: closed; reconnecting ..");
window.reloading();
// Reconnect after 1s, which is typical time it takes for ghcid to reboot.
// Then, retry in another 1s. Ideally we need an exponential retry logic.
setTimeout(init, 1000);
// refreshPage();
};
ws.onmessage = evt => {
console.log("ema: Resetting HTML body")
console.log("ema: ✍ Replacing DOM")
setInnerHtml(document.documentElement, evt.data);
watchRoute();
// Intercept route click events, and ask server for its HTML whilst
// managing history state.
document.body.addEventListener(`click`, e => {
const origin = e.target.closest("a");
if (origin) {
if (window.location.host === origin.host) {
document.body.classList.add("opacity-20");
window.history.pushState({}, "", origin.pathname);
switchRoute(origin.pathname);
e.preventDefault();
};
}
});
// Continue observing
watchCurrentRoute();
};
window.onbeforeunload = evt => { ws.close(); };
window.onpagehide = evt => { ws.close(); };
// When the user clicks the back button, resume watching the URL in
// the addressback, which has the effect of loading it immediately.
window.onpopstate = function(e) {
document.body.classList.add("opacity-20");
watchCurrentRoute();
};
};
window.onpageshow = init;