Implement NTP-based time synchronization

[hanxuan-lin]

NTP-based time synchronization to prevent users from bypassing timeline validation by manipulating their device time.

Summary by CodeRabbit

• New Features
  • App time now syncs with a trusted server for more accurate current time across the app.
• Bug Fixes
  • More reliable determination of past vs. upcoming events, ensuring correct visibility of event lists, details, and actions.
• Refactor
  • Standardized event “ended” checks and centralized time retrieval for consistent behavior.
• Chores
  • Added a time synchronization dependency and initialized it during app startup.

[coderabbitai]

Walkthrough

Introduces ServerTimeService for NTP-based time sync, initializes it during app startup, and updates time usage: TimezoneService now derives current time from ServerTimeService. Event screens switch past-event checks from direct DateTime.now() comparisons to hasEnded. Adds ntp dependency. No public API signatures changed.

Changes

Cohort / File(s)	Summary of changes
Event screens: past-event logic lib/features/event/presentation/screens/booked_events_screen.dart, lib/features/event/presentation/screens/event_detail_screen.dart, lib/features/event/presentation/screens/event_screen.dart	Replace end-time checks using DateTime.now() with hasEnded for filtering and UI conditionals; sorting and other flows unchanged.
Time services: introduction and integration lib/shared/infrastructure/services/server_time_service.dart, lib/shared/infrastructure/services/timezone_service.dart	Add ServerTimeService singleton with NTP sync, cached offset, and getAccurateNow(). Update TimezoneService.stockholmNow() to use ServerTimeService for accurate UTC time before converting to Stockholm.
App startup initialization lib/main.dart	Import and await ServerTimeService.instance.initialize() after timezone init, before service locator setup.
Dependencies pubspec.yaml	Add ntp: ^2.0.0 dependency.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant App as main.dart
  participant TZ as TimezoneService
  participant ST as ServerTimeService
  participant NTP as NTP Server

  rect rgba(221,238,255,0.5)
  note over App: App startup
  App->>TZ: initialize timezones
  App->>ST: initialize()
  activate ST
  ST->>NTP: fetch current time (timeout 5s)
  alt success
    NTP-->>ST: ntpTime
    ST-->>ST: compute offset (ntp - device)
  else failure
    ST-->>ST: set zero offset
  end
  deactivate ST
  App->>App: continue startup
  end

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sequenceDiagram
  autonumber
  participant UI as Event/Timezone callers
  participant TZ as TimezoneService
  participant ST as ServerTimeService

  rect rgba(232,252,244,0.6)
  note over UI: Need current Stockholm time
  UI->>TZ: stockholmNow()
  TZ->>ST: getAccurateNow()
  ST-->>TZ: accurateUtcNow (with cached offset)
  TZ-->>UI: tz.TZDateTime(Stockholm)
  end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• Timeline validation for student sessions application timeslot booking #21 — Introduced TimezoneService.stockholmNow(); this PR modifies that service to source time from ServerTimeService, aligning with earlier time-handling changes.

Suggested reviewers

• Hugo-Persson

Poem

A rabbit checked the ticking sky, ⏱️
Synced with clouds where NTPs fly.
No more guessing “now” by ear—
Stockholm’s time is crystal-clear.
Events that ended hop aside,
The accurate clock’s our guide.
Thump-thump—bugs can’t hide! 🐇✨

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title succinctly and accurately captures the primary change—adding NTP-based time synchronization—without extraneous detail, making it clear to reviewers what the main feature of the PR is.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix-timeline-validation

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[github-actions]

PR Preview Action v1.6.2
🚀 View preview at https://careerfairsystems.github.io/arkad-app-flutter/pr-preview/pr-33/
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[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 6d48262 and 61cbf8a.

⛔ Files ignored due to path filters (1)

• pubspec.lock is excluded by !**/*.lock

📒 Files selected for processing (7)

• lib/features/event/presentation/screens/booked_events_screen.dart (1 hunks)
• lib/features/event/presentation/screens/event_detail_screen.dart (1 hunks)
• lib/features/event/presentation/screens/event_screen.dart (1 hunks)
• lib/main.dart (2 hunks)
• lib/shared/infrastructure/services/server_time_service.dart (1 hunks)
• lib/shared/infrastructure/services/timezone_service.dart (2 hunks)
• pubspec.yaml (1 hunks)

🧰 Additional context used

📓 Path-based instructions (3)

lib/**/presentation/screens/**/*.dart

📄 CodeRabbit inference engine (CLAUDE.md)

lib/**/presentation/screens/**/*.dart: Reset command state in initState using addPostFrameCallback to avoid stale UI state
Use GoRouter context.go/push/pop for navigation; do not use Navigator directly
Only navigate after a command isCompleted and has no error
Invoke ViewModel methods for actions; never execute commands directly from UI

Files:

• lib/features/event/presentation/screens/event_detail_screen.dart
• lib/features/event/presentation/screens/booked_events_screen.dart
• lib/features/event/presentation/screens/event_screen.dart

**/*.dart

📄 CodeRabbit inference engine (CLAUDE.md)

**/*.dart: Use snake_case for file names, PascalCase for classes, camelCase for variables, and _prefix for private members
Wrap debug logging with kDebugMode and avoid production prints of sensitive data

Files:

• lib/features/event/presentation/screens/event_detail_screen.dart
• lib/features/event/presentation/screens/booked_events_screen.dart
• lib/features/event/presentation/screens/event_screen.dart
• lib/shared/infrastructure/services/timezone_service.dart
• lib/main.dart
• lib/shared/infrastructure/services/server_time_service.dart

pubspec.yaml

📄 CodeRabbit inference engine (CLAUDE.md)

Never use 'any' for dependencies; specify version ranges (e.g., dio: ^5.x)

Files:

• pubspec.yaml

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: Build Flutter Web

[coderabbitai]

⚠️ Potential issue | 🔴 Critical

Replace unsupported Sentry logging API

Sentry.logger and SentryLogAttribute are not part of sentry_flutter 9.6.0, so this block will not compile. Please switch to a supported API (e.g., Sentry.captureMessage with SentryLevel.info, or a breadcrumb) or drop the structured attributes.