Sleep hypnogram: hover tooltip with exact times + darker REM colour

Add per-segment mouseover tooltip (stage, start–end clock, duration) to the
sleep timeline, matching the other trend charts. Darken REM from #8b5cf6 to
#7c3aed across the hypnogram, fallback bar, legends and SleepChart so it reads
distinctly from light sleep (#a78bfa).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/pages/HealthPage.jsx

@@ -1,4 +1,4 @@
-import { useState, useMemo } from 'react'
+import { useState, useMemo, useRef } from 'react'
 import { useQuery, keepPreviousData } from '@tanstack/react-query'
 import {
   AreaChart, Area, ComposedChart, Line, BarChart, Bar, ReferenceLine, ReferenceArea,
@@ -293,18 +293,22 @@ function BodyBatteryChart({ bb, hiresValues, sleepStart, sleepEnd, activities })
 
 // Proper sleep hypnogram: 4 horizontal lanes (Awake/REM/Light/Deep), time on X axis
 const SLEEP_LANE_ORDER = [1, 4, 2, 3]  // top→bottom: awake, rem, light, deep
-const SLEEP_STAGE_COLOR = { 0: '#6b7280', 1: '#eab308', 2: '#a78bfa', 3: '#6366f1', 4: '#8b5cf6' }
+const SLEEP_STAGE_COLOR = { 0: '#6b7280', 1: '#eab308', 2: '#a78bfa', 3: '#6366f1', 4: '#7c3aed' }
 const SLEEP_STAGE_LABEL = { 1: 'Awake', 2: 'Light', 3: 'Deep', 4: 'REM' }
 const LANE_H = 15
 
+const fmtClock = (ms) => new Date(ms).toLocaleTimeString('en-GB', { hour: '2-digit', minute: '2-digit' })
+
 function SleepHypnogram({ sleepStart, sleepEnd, stages }) {
+  const wrapRef = useRef(null)
+  const [tip, setTip] = useState(null)
   if (!sleepStart || !sleepEnd || !stages?.length) return null
   const startMs = new Date(sleepStart).getTime()
   const endMs   = new Date(sleepEnd).getTime()
   const windowMs = endMs - startMs
   if (windowMs <= 0) return null
 
-  // Build segments per lane
+  // Build segments per lane (keep each segment's real start/end for the tooltip)
   const segsByLane = {}
   SLEEP_LANE_ORDER.forEach(lv => { segsByLane[lv] = [] })
   stages.forEach(([tsMs, level], i) => {
@@ -313,9 +317,21 @@ function SleepHypnogram({ sleepStart, sleepEnd, stages }) {
     const left  = Math.max(0, (tsMs - startMs) / windowMs * 100)
     const right = Math.min(100, (nextTs - startMs) / windowMs * 100)
     const w = right - left
-    if (w > 0) segsByLane[level].push({ left, w })
+    if (w > 0) segsByLane[level].push({ left, w, level, startMs: tsMs, endMs: nextTs })
   })
 
+  const showTip = (seg, e) => {
+    const rect = wrapRef.current?.getBoundingClientRect()
+    if (!rect) return
+    setTip({
+      x: e.clientX - rect.left,
+      y: e.clientY - rect.top,
+      level: seg.level,
+      range: `${fmtClock(seg.startMs)}–${fmtClock(seg.endMs)}`,
+      mins: Math.max(1, Math.round((seg.endMs - seg.startMs) / 60000)),
+    })
+  }
+
   // Hour ticks
   const sh = new Date(startMs); sh.setMinutes(0, 0, 0); sh.setHours(sh.getHours() + 1)
   const ticks = []
@@ -327,6 +343,7 @@ function SleepHypnogram({ sleepStart, sleepEnd, stages }) {
 
   return (
     <div className="pl-10">
+      <div ref={wrapRef} className="relative" onMouseLeave={() => setTip(null)}>
         <div className="space-y-px">
           {SLEEP_LANE_ORDER.map(level => (
             <div key={level} className="relative flex items-center">
@@ -336,8 +353,10 @@ function SleepHypnogram({ sleepStart, sleepEnd, stages }) {
               </span>
               <div className="relative flex-1 rounded-sm overflow-hidden bg-gray-800/50" style={{ height: LANE_H }}>
                 {segsByLane[level].map((seg, i) => (
-                <div key={i} className="absolute top-0 h-full"
-                  style={{ left: `${seg.left}%`, width: `${seg.w}%`, backgroundColor: SLEEP_STAGE_COLOR[level] }} />
+                  <div key={i} className="absolute top-0 h-full cursor-pointer"
+                    style={{ left: `${seg.left}%`, width: `${seg.w}%`, backgroundColor: SLEEP_STAGE_COLOR[level] }}
+                    onMouseEnter={(e) => showTip(seg, e)}
+                    onMouseMove={(e) => showTip(seg, e)} />
                 ))}
                 {ticks.map((t, i) => (
                   <div key={i} className="absolute top-0 bottom-0 w-px bg-black/20 pointer-events-none"
@@ -347,6 +366,16 @@ function SleepHypnogram({ sleepStart, sleepEnd, stages }) {
             </div>
           ))}
         </div>
+        {tip && (
+          <div className="absolute z-20 pointer-events-none px-2 py-1 rounded-md bg-gray-900/95 border border-gray-700 shadow-lg whitespace-nowrap flex items-center gap-1.5"
+            style={{ left: tip.x, top: tip.y - 10, transform: 'translate(-50%, -100%)', fontSize: 11 }}>
+            <span className="inline-block w-2 h-2 rounded-sm" style={{ backgroundColor: SLEEP_STAGE_COLOR[tip.level] }} />
+            <span className="text-white font-medium">{SLEEP_STAGE_LABEL[tip.level]}</span>
+            <span className="text-gray-400">{tip.range}</span>
+            <span className="text-gray-500">· {tip.mins}m</span>
+          </div>
+        )}
+      </div>
       <div className="relative h-4 mt-1 ml-0">
         <span className="absolute left-0 text-gray-500" style={{ fontSize: 10 }}>
           {new Date(startMs).toLocaleTimeString('en-GB', { hour: '2-digit', minute: '2-digit' })}
@@ -370,7 +399,7 @@ function SleepStageFallbackBar({ deepS, remS, lightS, awakeS }) {
   if (!total) return null
   const segments = [
     { label: 'Deep',  s: deepS  || 0, color: '#6366f1' },
-    { label: 'REM',   s: remS   || 0, color: '#8b5cf6' },
+    { label: 'REM',   s: remS   || 0, color: '#7c3aed' },
     { label: 'Light', s: lightS || 0, color: '#a78bfa' },
     { label: 'Awake', s: awakeS || 0, color: '#eab308' },
   ].filter(seg => seg.s > 0)
@@ -485,7 +514,7 @@ function DailySnapshot({ day, snapshotWeight, avg30, intradayHr, bodyBattery, bb
               <div className="flex flex-wrap gap-x-5 gap-y-1.5 mt-2">
                 {[
                   ['Deep',  day.sleep_deep_s,  '#6366f1'],
-                  ['REM',   day.sleep_rem_s,   '#8b5cf6'],
+                  ['REM',   day.sleep_rem_s,   '#7c3aed'],
                   ['Light', day.sleep_light_s, '#a78bfa'],
                   ['Awake', day.sleep_awake_s, '#eab308'],
                 ].map(([label, secs, color]) => secs ? (
@@ -751,7 +780,7 @@ function SleepChart({ data, selectedDate, onDayClick }) {
             label={{ value: `avg ${avgSleep}h`, position: 'right', fill: '#a855f7', fontSize: 9 }} />
         )}
         <Bar dataKey="deep"  name="Deep"  stackId="a" fill="#6366f1" />
-        <Bar dataKey="rem"   name="REM"   stackId="a" fill="#8b5cf6" />
+        <Bar dataKey="rem"   name="REM"   stackId="a" fill="#7c3aed" />
         <Bar dataKey="light" name="Light" stackId="a" fill="#a78bfa" />
         <Bar dataKey="awake" name="Awake" stackId="a" fill="#eab308" radius={[2, 2, 0, 0]} />
       </BarChart>
@@ -1055,7 +1084,7 @@ export default function HealthPage() {
               <SleepChart data={metrics}
                 selectedDate={selDateForCharts} onDayClick={handleDayClick} />
               <div className="flex gap-4 mt-2">
-                {[['Deep','#6366f1'],['REM','#8b5cf6'],['Light','#a78bfa'],['Awake','#eab308']].map(([l,c]) => (
+                {[['Deep','#6366f1'],['REM','#7c3aed'],['Light','#a78bfa'],['Awake','#eab308']].map(([l,c]) => (
                   <div key={l} className="flex items-center gap-1.5">
                     <div className="w-2.5 h-2.5 rounded-sm" style={{ backgroundColor: c }} />
                     <span className="text-xs text-gray-400">{l}</span>