Added report functionality and Dropbox connection

lib/services/cloud_oauth_config.dart

@@ -24,14 +24,14 @@ class CloudOAuthConfig {
   // From a "Full Dropbox" access app at dropbox.com/developers/apps.
 
   /// The app's key (client ID for OAuth2 PKCE — no secret needed).
-  static const String? dropboxAppKey = null; // TODO: fill in
+  static const String? dropboxAppKey = 'id43qmk09hilpgk';
 
   /// Custom URL scheme redirect registered in the Dropbox app console.
   /// The scheme "mofueltaxback-dropbox" is already wired up in
   /// AndroidManifest.xml / Info.plist, so unless you have a reason to pick
   /// a different scheme, use exactly:
   /// "mofueltaxback-dropbox://oauth2redirect"
-  static const String? dropboxRedirectUri = null; // TODO: fill in
+  static const String? dropboxRedirectUri = 'mofueltaxback-dropbox://oauth2redirect';
 
   // --- OneDrive (Microsoft Graph) ---
   //

lib/services/fuel_report.dart

@@ -0,0 +1,81 @@
+import '../models/fuel_entry.dart';
+import '../models/vehicle.dart';
+
+/// One vehicle's totals within a [FuelReport]'s date range.
+class VehicleReportRow {
+  final Vehicle vehicle;
+  final int entryCount;
+  final double totalGallons;
+  final double totalCost;
+
+  VehicleReportRow({
+    required this.vehicle,
+    required this.entryCount,
+    required this.totalGallons,
+    required this.totalCost,
+  });
+}
+
+/// Per-vehicle fuel totals for entries with a receipt, dated within
+/// [startDate]–[endDate] inclusive. See [buildFuelReport].
+class FuelReport {
+  final DateTime startDate;
+  final DateTime endDate;
+  final List<VehicleReportRow> rows;
+
+  FuelReport({required this.startDate, required this.endDate, required this.rows});
+
+  double get totalGallons => rows.fold(0.0, (sum, r) => sum + r.totalGallons);
+  double get totalCost => rows.fold(0.0, (sum, r) => sum + r.totalCost);
+}
+
+/// Builds a per-vehicle fuel summary for [startDate]–[endDate] (inclusive,
+/// judged by each entry's purchase date, in local time), restricted to
+/// entries that actually have a receipt attached — a report meant to
+/// substantiate a fuel tax refund claim is only as good as the
+/// documentation behind each entry, so an entry logged without a photo
+/// isn't something the report should be claiming on your behalf. "Has a
+/// receipt" means a local copy or a cloud copy — [FuelEntry.receiptImagePath]
+/// or [FuelEntry.receiptDriveFileId] — not specifically an already-synced
+/// one, since sync status is a technical detail unrelated to whether the
+/// purchase is documented.
+///
+/// Vehicles with no qualifying entries in range are omitted rather than
+/// shown with an all-zero row. Rows are sorted by [Vehicle.displayLabel].
+FuelReport buildFuelReport({
+  required List<Vehicle> vehicles,
+  required List<FuelEntry> fuelEntries,
+  required DateTime startDate,
+  required DateTime endDate,
+}) {
+  final rangeStart = DateTime(startDate.year, startDate.month, startDate.day);
+  final rangeEndExclusive =
+      DateTime(endDate.year, endDate.month, endDate.day).add(const Duration(days: 1));
+
+  final vehiclesById = {for (final v in vehicles) v.id: v};
+  final entriesByVehicle = <String, List<FuelEntry>>{};
+
+  for (final entry in fuelEntries) {
+    final hasReceipt = entry.receiptImagePath != null || entry.receiptDriveFileId != null;
+    if (!hasReceipt) continue;
+    if (entry.date.isBefore(rangeStart) || !entry.date.isBefore(rangeEndExclusive)) continue;
+    (entriesByVehicle[entry.vehicleId] ??= []).add(entry);
+  }
+
+  final rows = <VehicleReportRow>[];
+  for (final entry in entriesByVehicle.entries) {
+    final vehicle = vehiclesById[entry.key];
+    // No matching (active) vehicle — e.g. deleted since — nothing sane to
+    // attribute these entries to.
+    if (vehicle == null) continue;
+    rows.add(VehicleReportRow(
+      vehicle: vehicle,
+      entryCount: entry.value.length,
+      totalGallons: entry.value.fold(0.0, (sum, e) => sum + e.gallons),
+      totalCost: entry.value.fold(0.0, (sum, e) => sum + e.totalCost),
+    ));
+  }
+  rows.sort((a, b) => a.vehicle.displayLabel.compareTo(b.vehicle.displayLabel));
+
+  return FuelReport(startDate: rangeStart, endDate: endDate, rows: rows);
+}

lib/services/fuel_report_pdf.dart

@@ -0,0 +1,85 @@
+import 'dart:typed_data';
+
+import 'package:intl/intl.dart';
+import 'package:pdf/pdf.dart';
+import 'package:pdf/widgets.dart' as pw;
+
+import 'fuel_report.dart';
+
+final _dateFormat = DateFormat.yMMMd();
+final _currencyFormat = NumberFormat.simpleCurrency();
+
+/// Renders [report] as a single-page-friendly PDF: a per-vehicle table
+/// (VIN, nickname, entry count, gallons, total cost) plus a grand-total
+/// row, suitable for attaching to a fuel tax refund submission or handing
+/// to a printer.
+Future<Uint8List> buildFuelReportPdf(FuelReport report) async {
+  final doc = pw.Document();
+
+  doc.addPage(
+    pw.MultiPage(
+      pageFormat: PdfPageFormat.letter,
+      header: (context) => pw.Column(
+        crossAxisAlignment: pw.CrossAxisAlignment.start,
+        children: [
+          pw.Text('Fuel Report', style: pw.TextStyle(fontSize: 20, fontWeight: pw.FontWeight.bold)),
+          pw.Text(
+            '${_dateFormat.format(report.startDate)} – ${_dateFormat.format(report.endDate)}',
+            style: const pw.TextStyle(fontSize: 12, color: PdfColors.grey700),
+          ),
+          pw.SizedBox(height: 16),
+        ],
+      ),
+      build: (context) => [
+        if (report.rows.isEmpty)
+          pw.Text('No vehicles had a receipted fuel entry in this date range.')
+        else
+          pw.TableHelper.fromTextArray(
+            headers: ['Vehicle', 'VIN', 'Entries', 'Gallons', 'Total Cost'],
+            data: [
+              for (final row in report.rows)
+                [
+                  row.vehicle.nickname?.trim().isNotEmpty == true ? row.vehicle.nickname! : '—',
+                  row.vehicle.vin,
+                  row.entryCount.toString(),
+                  row.totalGallons.toStringAsFixed(3),
+                  _currencyFormat.format(row.totalCost),
+                ],
+            ],
+            cellAlignments: const {
+              2: pw.Alignment.centerRight,
+              3: pw.Alignment.centerRight,
+              4: pw.Alignment.centerRight,
+            },
+            headerAlignments: const {
+              2: pw.Alignment.centerRight,
+              3: pw.Alignment.centerRight,
+              4: pw.Alignment.centerRight,
+            },
+            headerStyle: pw.TextStyle(fontWeight: pw.FontWeight.bold),
+            cellPadding: const pw.EdgeInsets.symmetric(horizontal: 8, vertical: 6),
+          ),
+        pw.SizedBox(height: 12),
+        pw.Divider(),
+        pw.Row(
+          mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
+          children: [
+            pw.Text('Total', style: pw.TextStyle(fontWeight: pw.FontWeight.bold)),
+            pw.Text(
+              '${report.totalGallons.toStringAsFixed(3)} gal · ${_currencyFormat.format(report.totalCost)}',
+              style: pw.TextStyle(fontWeight: pw.FontWeight.bold),
+            ),
+          ],
+        ),
+      ],
+    ),
+  );
+
+  return doc.save();
+}
+
+/// `fuel-report-<start>-<end>.pdf`, e.g. `fuel-report-20260101-20260331.pdf`.
+String fuelReportFileName(FuelReport report) {
+  final fmt = DateFormat('yyyyMMdd');
+  return 'fuel-report-${fmt.format(report.startDate)}-${fmt.format(report.endDate)}.pdf';
+}