Generate user avatar from email

app/(tabs)/you.tsx

@@ -4,6 +4,7 @@ import { useRouter } from 'expo-router';
 
 import { ThemedText } from '@/components/themed-text';
 import { ThemedView } from '@/components/themed-view';
+import { UserAvatar } from '@/components/user-avatar';
 import { IconSymbol } from '@/components/ui/icon-symbol';
 import { Colors } from '@/constants/theme';
 import { useColorScheme } from '@/hooks/use-color-scheme';
@@ -43,7 +44,7 @@ export default function YouScreen() {
         </View>
 
         <View style={styles.card}>
-          <IconSymbol name="person.fill" size={24} color={theme.primary} />
+          <UserAvatar email={session?.user.email} size={56} />
           <View style={styles.cardText}>
             <ThemedText style={styles.cardTitle}>{session?.user.email ?? 'Unknown user'}</ThemedText>
             <ThemedText style={styles.cardDescription}>Email</ThemedText>

components/user-avatar.tsx

@@ -0,0 +1,47 @@
+import { memo, useMemo } from 'react';
+import { StyleSheet, Text, View } from 'react-native';
+
+import { generateAvatarFromEmail } from '@/lib/avatar';
+
+type UserAvatarProps = {
+  email?: string | null;
+  size?: number;
+  testID?: string;
+};
+
+function UserAvatarComponent({ email, size = 52, testID }: UserAvatarProps) {
+  const avatar = useMemo(() => generateAvatarFromEmail(email), [email]);
+  const fontSize = Math.max(16, size * 0.42);
+
+  return (
+    <View
+      style={[
+        styles.container,
+        {
+          width: size,
+          height: size,
+          borderRadius: size / 2,
+          backgroundColor: avatar.backgroundColor,
+        },
+      ]}
+      accessibilityRole="image"
+      accessibilityLabel={email ? `Avatar for ${email}` : 'Avatar placeholder'}
+      testID={testID}
+    >
+      <Text style={[styles.initials, { color: avatar.foregroundColor, fontSize }]}>{avatar.initials}</Text>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    alignItems: 'center',
+    justifyContent: 'center',
+  },
+  initials: {
+    fontWeight: '700',
+    letterSpacing: 0.4,
+  },
+});
+
+export const UserAvatar = memo(UserAvatarComponent);

lib/avatar.ts

@@ -0,0 +1,95 @@
+import type { UserAvatarData } from '@/types';
+
+const DEFAULT_AVATAR: UserAvatarData = {
+  initials: '?',
+  backgroundColor: '#E0E7FF',
+  foregroundColor: '#312E81',
+};
+
+export function generateAvatarFromEmail(email?: string | null): UserAvatarData {
+  if (!email) {
+    return { ...DEFAULT_AVATAR };
+  }
+
+  const normalized = email.trim().toLowerCase();
+  if (!normalized) {
+    return { ...DEFAULT_AVATAR };
+  }
+
+  const initials = createInitials(normalized);
+  const hash = hashString(normalized);
+  const backgroundColor = hslToHex(hash % 360, 65, 72);
+  const foregroundColor = hslToHex((hash + 180) % 360, 45, 22);
+
+  return {
+    initials,
+    backgroundColor,
+    foregroundColor,
+  };
+}
+
+function createInitials(email: string) {
+  const localPart = email.split('@')[0];
+  const segments = localPart.split(/[^a-z0-9]+/i).filter(Boolean);
+
+  if (segments.length >= 2) {
+    return `${segments[0][0]}${segments[1][0]}`.toUpperCase();
+  }
+
+  if (segments.length === 1 && segments[0].length >= 2) {
+    return segments[0].slice(0, 2).toUpperCase();
+  }
+
+  return localPart.slice(0, 2).toUpperCase() || '?';
+}
+
+function hashString(value: string) {
+  let hash = 0;
+  for (let i = 0; i < value.length; i += 1) {
+    hash = (hash << 5) - hash + value.charCodeAt(i);
+    hash |= 0;
+  }
+
+  return Math.abs(hash);
+}
+
+function hslToHex(hue: number, saturation: number, lightness: number) {
+  const normalizedHue = ((hue % 360) + 360) % 360;
+  const s = saturation / 100;
+  const l = lightness / 100;
+
+  const c = (1 - Math.abs(2 * l - 1)) * s;
+  const x = c * (1 - Math.abs(((normalizedHue / 60) % 2) - 1));
+  const m = l - c / 2;
+
+  let r = 0;
+  let g = 0;
+  let b = 0;
+
+  if (normalizedHue >= 0 && normalizedHue < 60) {
+    r = c;
+    g = x;
+  } else if (normalizedHue >= 60 && normalizedHue < 120) {
+    r = x;
+    g = c;
+  } else if (normalizedHue >= 120 && normalizedHue < 180) {
+    g = c;
+    b = x;
+  } else if (normalizedHue >= 180 && normalizedHue < 240) {
+    g = x;
+    b = c;
+  } else if (normalizedHue >= 240 && normalizedHue < 300) {
+    r = x;
+    b = c;
+  } else {
+    r = c;
+    b = x;
+  }
+
+  const toHex = (value: number) => {
+    const channel = Math.round((value + m) * 255);
+    return channel.toString(16).padStart(2, '0');
+  };
+
+  return `#${toHex(r)}${toHex(g)}${toHex(b)}`;
+}

types/index.ts

@@ -53,3 +53,9 @@ export interface WeightEntryRecord {
   created_at: string;
 }
 
+export interface UserAvatarData {
+  initials: string;
+  backgroundColor: string;
+  foregroundColor: string;
+}
+