feat: ThemeContext

app/_layout.tsx

@@ -1,7 +1,8 @@
 import { Slot } from 'expo-router';
 import React, { useEffect } from 'react';
-import { initDatabase } from '../services/database';
+import { addCategory, initDatabase } from '../services/database';
 import { AuthProvider } from './contexts/AuthContext';
+import { ThemeProvider } from './contexts/ThemeContext';
 
 export default function _layout() {
 
@@ -12,7 +13,9 @@ export default function _layout() {
   console.log("layout called")
   return (
     <AuthProvider>
-      <Slot />
+      <ThemeProvider>
+        <Slot />
+      </ThemeProvider>
     </AuthProvider>
   )
 }

app/contexts/ThemeContext.tsx

@@ -0,0 +1,97 @@
+import {useContext, createContext, useState, useEffect} from "react"
+import AsyncStorage from "@react-native-async-storage/async-storage"
+import { useColorScheme } from "react-native";
+import themeColors from "../../constants/colors";
+
+
+interface ThemeProps {
+  isSystemTheme?: boolean
+  theme: "light" | "dark";
+  colors: typeof themeColors.light & typeof themeColors.dark;
+  applySystemTheme?: () => void;
+  applyTheme?: (theme: "light" | "dark") => void;
+}
+
+const THEME_KEY = "THEME"
+const SYSTEM_THEME_KEY = "SYSTEM_THEME"
+
+const ThemeContext = createContext<ThemeProps>({theme: "light", colors: themeColors.light})
+
+export const useTheme = () => {
+  return useContext(ThemeContext)
+}
+
+export const ThemeProvider = ({children} : any) => {
+  const currentSystemTheme = useColorScheme()
+  const [isSystemTheme, setIsSystemTheme] = useState<boolean>(true);
+  const [theme, setTheme] = useState<"light" | "dark">("light");
+  const [colors, setColors] = useState<typeof themeColors.light & typeof themeColors.dark>(themeColors.light)
+
+  useEffect(() => {
+    console.log("effect called")
+    const loadTheme = async () => {
+      try {
+        const is_system_theme = await AsyncStorage.getItem(SYSTEM_THEME_KEY)
+        const saved_theme = await AsyncStorage.getItem(THEME_KEY);
+
+        if(is_system_theme !== "false"){//We will use !== false bacause system theme should be used if unspecified
+          applySystemTheme();
+          return;
+        }
+
+        if(saved_theme === "light" || saved_theme === "dark"){
+          applyTheme(saved_theme);
+        }
+
+      } catch (error) {
+        console.error(error)
+      }
+    } 
+    loadTheme();
+  }, [currentSystemTheme])
+
+
+  const applySystemTheme = () => {
+    const storeSystemTheme = async () => {
+      console.log("applySystemTheme")
+      await AsyncStorage.setItem(SYSTEM_THEME_KEY, "true")
+    }
+
+    storeSystemTheme();
+    setIsSystemTheme(true)
+    applyThemeInternal(currentSystemTheme ?? "light")
+  }
+
+  const applyThemeInternal = (theme: "light" | "dark") => {
+    const storeTheme = async (theme: "light" | "dark") => {
+      await AsyncStorage.setItem(THEME_KEY, theme)
+    }
+
+    setTheme(theme);
+    storeTheme(theme);
+    setColors(themeColors[theme])
+  }
+
+  const applyTheme = (theme: "light" | "dark") => {
+    const unsetSytemTheme = async () => {
+      AsyncStorage.setItem(SYSTEM_THEME_KEY, "false");
+    }
+    unsetSytemTheme()
+    setIsSystemTheme(false);
+    applyThemeInternal(theme);
+  }
+
+  const value = {
+    isSystemTheme: isSystemTheme,
+    applyTheme: applyTheme,
+    applySystemTheme: applySystemTheme,
+    theme: theme,
+    colors: colors,
+  }
+
+  return (
+    <ThemeContext.Provider value={value}>
+      {children}
+    </ThemeContext.Provider>
+  )
+}