if 120 day haven't gone by yet, grade the user on how many days they have been using the app

my_app/lib/main.dart

@@ -3,6 +3,8 @@ import 'dart:convert';
 
 import 'dart:io';
 
+import 'dart:math';
+
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
@@ -15,16 +17,23 @@ import 'package:path_provider/path_provider.dart';
 
 class ReadWrite
 {
-  static Future<File> get_file() async
+  static Future<File> get_history_file() async
   {
     Directory? directory = await getApplicationDocumentsDirectory();
 
     return File("${directory.path}/history.json");
   }
 
+  static Future<File> get_first_time_file() async
+  {
+    Directory? directory = await getApplicationDocumentsDirectory();
+
+    return File("${directory.path}/first-time.json");
+  }
+
   static Future<List<DateTime>> read_history() async
   {
-    final file = await get_file();
+    final file = await get_history_file();
 
     List<List<int>> tuple_history = [];
     
@@ -63,7 +72,7 @@ class ReadWrite
 
   static Future<Null> writeTextFile(List<DateTime> history) async
   {
-    final file = await get_file();
+    final file = await get_history_file();
 
     var tuple_history = <List<int>>[];
 
@@ -76,6 +85,42 @@ class ReadWrite
 
     return null;
   }
+
+  static Future<DateTime> get_first_time() async
+  {
+    final file = await get_first_time_file();
+
+    DateTime first_time;
+    
+    try
+    {
+      var text = await file.readAsString();
+      
+      List<dynamic> readable = jsonDecode(text);
+      
+      int year = readable[0];
+      int month = readable[1];
+      int day = readable[2];
+
+      first_time = DateTime(year, month, day);
+
+      print('first time day found');
+    }
+    on PathNotFoundException
+    {
+      print('no first time day found, assuming today');
+      
+      DateTime now = DateTime.now();
+
+      List<int> writeable = <int>[now.year, now.month, now.day];
+
+      file.writeAsString(jsonEncode(writeable));
+
+      first_time = DateTime(now.year, now.month, now.day);
+    }
+
+    return first_time;
+  }
 }
 
 void main()
@@ -87,6 +132,8 @@ class MyAppState extends ChangeNotifier
 {
   var history = <DateTime>[];
   
+  DateTime first_time = DateTime(1999, 1, 1);
+
   var percentage = 0.0;
 
   MyAppState()
@@ -98,12 +145,22 @@ class MyAppState extends ChangeNotifier
 
       notifyListeners();
     });
+
+    ReadWrite.get_first_time().then((x) {
+      first_time = x;
+
+      recalculate_percentage();
+
+      notifyListeners();
+    });
   }
 
   void recalculate_percentage()
   {
     var now = DateTime.now();
     
+    now = DateTime(now.year, now.month, now.day);
+
     var cutoff = DateTime(now.year, now.month, now.day - 120);
 
     while (history.length > 0 && history[0].isBefore(cutoff))
@@ -111,14 +168,22 @@ class MyAppState extends ChangeNotifier
       history.removeAt(0);
     }
 
-    if (history.length > 0)
-    {
-      percentage = history.length / 120;
-    }
-    else
+    if (history.length == 0)
     {
       percentage = 0.0;
     }
+    else if (first_time.isAfter(cutoff))
+    {
+      // print("line 177: ${history.length} / ${now.difference(first_time).inDays}");
+
+      percentage = history.length / max(now.difference(first_time).inDays, 1);
+    }
+    else
+    {
+      percentage = history.length / 120;
+    }
+
+    // print("percentage = ${percentage}");
   }
 
   void incrementCounter() async
@@ -127,7 +192,7 @@ class MyAppState extends ChangeNotifier
 
     now = DateTime(now.year, now.month, now.day);
 
-    if (!history.contains(now))
+    if (history.length == 0 || history[history.length - 1] != now)
     {
       history.add(now);
 
@@ -145,7 +210,7 @@ class MyAppState extends ChangeNotifier
 
     now = DateTime(now.year, now.month, now.day);
 
-    if (history.contains(now))
+    if (history.length > 0 && history[history.length - 1] == now)
     {
       history.remove(now);
 
@@ -206,7 +271,18 @@ class MyHomePage extends StatelessWidget {
 
     var now = DateTime.now();
 
-    var then = DateTime(now.year, now.month, now.day - 120);
+    var cutoff = DateTime(now.year, now.month, now.day - 120);
+
+    DateTime startDate;
+
+    if (appState.first_time.isAfter(cutoff))
+    {
+      startDate = appState.first_time;
+    }
+    else
+    {
+      startDate = cutoff;
+    }
 
     var inverse_primary = theme.colorScheme.inversePrimary;
 
@@ -231,14 +307,17 @@ class MyHomePage extends StatelessWidget {
                 HeatMap(
                   defaultColor: inverse_primary,
                   colorMode: ColorMode.opacity,
+                  startDate: startDate,
                   endDate: now,
-                  startDate: then,
                   showText: false,
                   scrollable: false,
                   showColorTip: false,
                   datasets: {
+                    for (int i = 0; i < 120; i++)
+                      DateTime(now.year, now.month, now.day - i): 1,
+
                     for (DateTime dt in appState.history)
-                      dt: 1,
+                      dt: 2,
                   },
                   colorsets: {
                     1: primary,
@@ -288,6 +367,10 @@ class MyHomePage extends StatelessWidget {
                     ),
                   ],
                 ),
+
+                // SizedBox(height: 10),
+
+                // Text("(The denominator is ${now.difference(appState.first_time).inDays})"),
               ],
             ),
           ],