From b5bbde8acbd93e6310cfc991a50b92611e8d2337 Mon Sep 17 00:00:00 2001
From: Per Magnus Petersen <magnus@pmagnus.dk>
Date: Thu, 17 Sep 2026 14:49:25 +0200
Subject: [PATCH] Show midnight price change in page title

---
 Makefile             |  9 ++++++++-
 app/main.py          | 40 ++++++++++++++++++++++++++++++++++++----
 tests/test_health.py |  8 +++++++-
 3 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 7025c43..2ad0032 100644
--- a/Makefile
+++ b/Makefile
@@ -4,8 +4,9 @@ export
 VENV := .venv
 UVICORN := $(VENV)/bin/uvicorn
 TEST_DEPS := $(VENV)/.test-deps
+K3S_BTCDATA_PORT := 4100
 
-.PHONY: clean run run-local run-citadel tailwind test venv
+.PHONY: clean run run-local run-citadel run-k3s tailwind test venv
 
 venv: $(UVICORN)
 
@@ -26,6 +27,12 @@ run-local: venv
 run-citadel: venv
 	BTCDATA_URL=$(BTCDATA_URL) $(UVICORN) app.main:app --host 0.0.0.0 --port 4000 --reload
 
+run-k3s: venv
+	kubectl -n btcdata port-forward service/btcdata $(K3S_BTCDATA_PORT):4101 & \
+	port_forward_pid=$$!; \
+	trap 'kill $$port_forward_pid' EXIT INT TERM; \
+	BTCDATA_URL=http://127.0.0.1:$(K3S_BTCDATA_PORT) $(UVICORN) app.main:app --host 0.0.0.0 --port 4000 --reload
+
 tailwind:
 	npm run css:watch
 
diff --git a/app/main.py b/app/main.py
index 243a53c..b99bf38 100644
--- a/app/main.py
+++ b/app/main.py
@@ -78,14 +78,45 @@ HOME_HTML = """\
 </div>
 <script>
 (function() {
+  let currentPrice = null;
+  let midnightPrice = null;
+
+  function formatPriceChange(change) {
+    const sign = change > 0 ? '+' : change < 0 ? '-' : '±';
+    const amount = Math.abs(change).toLocaleString('da-DK', {
+      minimumFractionDigits: 2,
+      maximumFractionDigits: 2,
+    });
+    return sign + '$' + amount;
+  }
+
   function updateTitleFromPrice() {
     const priceDisplay = document.getElementById('price-display');
     const price = priceDisplay && priceDisplay.dataset.titlePrice;
-    if (price) {
+    const priceValue = priceDisplay && Number(priceDisplay.dataset.priceValue);
+    if (price && Number.isFinite(priceValue)) {
+      currentPrice = priceValue;
+    }
+    if (price && currentPrice !== null && midnightPrice !== null) {
+      const change = currentPrice - midnightPrice;
+      const formattedChange = formatPriceChange(change);
+      document.title = price + ' | ' + formattedChange;
+    } else if (price) {
       document.title = price + ' | BTC Price';
     }
   }
 
+  function updateMidnightPrice(candles) {
+    const midnight = new Date();
+    midnight.setHours(0, 0, 0, 0);
+    const midnightSeconds = Math.floor(midnight.getTime() / 1000);
+    const firstToday = candles.find(candle => candle.time >= midnightSeconds);
+    if (firstToday) {
+      midnightPrice = firstToday.open;
+      updateTitleFromPrice();
+    }
+  }
+
   const pricePanel = document.getElementById('price-panel');
   new MutationObserver(updateTitleFromPrice).observe(pricePanel, {
     childList: true,
@@ -93,7 +124,7 @@ HOME_HTML = """\
   });
   updateTitleFromPrice();
 
-  function initChart(containerId, endpoint, intervalMs) {
+  function initChart(containerId, endpoint, intervalMs, onData) {
     const container = document.getElementById(containerId);
     const chart = LightweightCharts.createChart(container, {
       layout: { background: { type: 'solid', color: '#ffffff' }, textColor: '#6b7280' },
@@ -118,6 +149,7 @@ HOME_HTML = """\
             close: parseFloat(c.close),
           })).sort((a, b) => a.time - b.time);
           series.setData(data);
+          if (onData) onData(data);
           chart.timeScale().fitContent();
         })
         .catch(e => console.error('Chart fetch error:', e));
@@ -130,7 +162,7 @@ HOME_HTML = """\
   }
 
   initChart('chart-minute', '/api/kraken-minute', 60 * 1000);
-  initChart('chart-hour', '/api/kraken-hour', 5 * 60 * 1000);
+  initChart('chart-hour', '/api/kraken-hour', 5 * 60 * 1000, updateMidnightPrice);
 })();
 </script>
 </body>
@@ -250,7 +282,7 @@ def price_json_to_html(text: str) -> str:
 
     formatted_price = f'${da_fmt(",.2f", p)}'
     html = (
-        f'<div id="price-display" data-title-price="{formatted_price}">'
+        f'<div id="price-display" data-title-price="{formatted_price}" data-price-value="{p}">'
         '<div class="bg-white rounded-2xl shadow-sm border border-gray-200 p-6">'
         '<div class="text-center">'
         f'<p class="text-4xl font-bold {color}">{formatted_price}</p>'
diff --git a/tests/test_health.py b/tests/test_health.py
index fbc6517..fd1500c 100644
--- a/tests/test_health.py
+++ b/tests/test_health.py
@@ -37,7 +37,12 @@ def test_home_updates_title_from_latest_price():
 
     assert response.status_code == 200
     assert "new MutationObserver(updateTitleFromPrice)" in response.text
-    assert "document.title = price + ' | BTC Price'" in response.text
+    assert "currentPrice - midnightPrice" in response.text
+    assert "document.title = price + ' | ' + formattedChange" in response.text
+    assert '<h1 class="text-3xl font-bold text-gray-900">BTC Price</h1>' in response.text
+    assert "page-title" not in response.text
+    assert "formatPriceChange(change)" in response.text
+    assert "midnight.setHours(0, 0, 0, 0)" in response.text
 
 
 def test_price_fragment_exposes_formatted_price_for_title():
@@ -46,6 +51,7 @@ def test_price_fragment_exposes_formatted_price_for_title():
     )
 
     assert 'data-title-price="$67.432,10"' in html
+    assert 'data-price-value="67432.1"' in html
     assert ">$67.432,10</p>" in html