Fix #5037: Pause hint timer while hints and solution dialog is open

[Kishan8548]

Explanation

Fixes #5037

Pause hint timer while hints and solution dialog is open

Context & Root Cause

Previously, HintHandlerProdImpl scheduled hints and solution availability on an uninterrupted countdown delay. If a learner opened the HintsAndSolutionDialogFragment to read an earlier hint or inspect a solution, the countdown timer for subsequent hints or solutions continued ticking in the background. As a result:

• Subsequent hints could unlock while the dialog was still visible.
• Learners could receive hints without spending active problem-solving time on the card itself.

Technical Implementation

1. Domain Timer State (HintHandlerProdImpl & HintHandlerDebugImpl):

   • Added pause() and resume() to the HintHandler interface.
   • In HintHandlerProdImpl, integrated OppiaClock to track the exact elapsed time prior to pausing. When resumed, the remaining duration (targetDelay - elapsedTime) is scheduled rather than restarting the full delay.
   • Handled edge cases: pausing when no timer is active, multiple sequential pauses, and resuming after the delay has already elapsed.
   • Updated HintHandlerDebugImpl with matching no-op / state-tracking methods.

2. Controller & Concurrency Layer:

   • Added pauseHintsAndSolutionTimer() and resumeHintsAndSolutionTimer() to both ExplorationProgressController and QuestionAssessmentProgressController.
   • Serialized pause/resume events via the existing actor message channels to guarantee thread safety and proper ordering with answer submissions and state transitions.

3. Lifecycle & UI Wiring:

   • Extended HintsAndSolutionListener with onHintsAndSolutionDialogShown() and onHintsAndSolutionDialogDismissed().
   • Connected HintsAndSolutionDialogFragment's onStart() and onDismiss() lifecycle methods to notify the listener.
   • Delegated these events from ExplorationActivity and QuestionPlayerActivity through their respective fragments down to ExplorationProgressController and QuestionAssessmentProgressController.

4. Testing & Verification:

   • Unit Tests: Added targeted tests in HintHandlerProdImplTest, HintHandlerDebugImplTest, ExplorationProgressControllerTest, and QuestionAssessmentProgressControllerTest covering pause before first hint, pause between hints, multiple pause/resume cycles, and solution timers.
   • DI / Modules: Updated HintsAndSolutionProdModuleTest and HintsAndSolutionDebugModuleTest with FakeOppiaClockModule to verify Dagger dependency graph integrity.
   • Local Verification: Ran all related unit tests and interaction tests (StateFragmentTest, ExplorationActivityTest, QuestionPlayerActivityTest) as well as all static checks (ktlint, checkstyle, buildifier), all of which passed.

Essential Checklist

• The PR title starts with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• The explanation section above starts with "Fixes #bugnum: " (If this PR fixes part of an issue, use instead: "Fixes part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

Disclosure of LLM Usage

• Did you use AI/LLMs when working on this PR? Type Yes or No.
  Yes
• If yes, describe the extent AI was used: Brainstorming architecture, implementing pause/resume logic, writing unit tests, and debugging Bazel build dependencies.

[github-actions]

Coverage Report

Results

Number of files assessed: 22
Overall Coverage: 0.00%
Coverage Analysis: PASS ✅

Exempted coverage

Files exempted from coverage

File	Exemption Reason
ExplorationFragment.kt app/src/main/java/org/oppia/android/app/player/exploration/ExplorationFragment.kt	This file is exempted from having a test file; skipping coverage check.
ExplorationFragmentPresenter.kt app/src/main/java/org/oppia/android/app/player/exploration/ExplorationFragmentPresenter.kt	This file is exempted from having a test file; skipping coverage check.
ExplorationActivity.kt app/src/main/java/org/oppia/android/app/player/exploration/ExplorationActivity.kt	This file is incompatible with code coverage tooling; skipping coverage check.
ExplorationActivityPresenter.kt app/src/main/java/org/oppia/android/app/player/exploration/ExplorationActivityPresenter.kt	This file is exempted from having a test file; skipping coverage check.
StateFragmentPresenter.kt app/src/main/java/org/oppia/android/app/player/state/StateFragmentPresenter.kt	This file is exempted from having a test file; skipping coverage check.
StateFragmentTestActivityPresenter.kt app/src/main/java/org/oppia/android/app/player/state/testing/StateFragmentTestActivityPresenter.kt	This file is exempted from having a test file; skipping coverage check.
StateFragmentTestActivity.kt app/src/main/java/org/oppia/android/app/player/state/testing/StateFragmentTestActivity.kt	This file is exempted from having a test file; skipping coverage check.
StateFragment.kt app/src/main/java/org/oppia/android/app/player/state/StateFragment.kt	This file is incompatible with code coverage tooling; skipping coverage check.
HintsAndSolutionDialogFragmentPresenter.kt app/src/main/java/org/oppia/android/app/hintsandsolution/HintsAndSolutionDialogFragmentPresenter.kt	This file is exempted from having a test file; skipping coverage check.
HintsAndSolutionDialogFragment.kt app/src/main/java/org/oppia/android/app/hintsandsolution/HintsAndSolutionDialogFragment.kt	This file is exempted from having a test file; skipping coverage check.
HintsAndSolutionListener.kt app/src/main/java/org/oppia/android/app/hintsandsolution/HintsAndSolutionListener.kt	This file is exempted from having a test file; skipping coverage check.
QuestionPlayerFragment.kt app/src/main/java/org/oppia/android/app/topic/questionplayer/QuestionPlayerFragment.kt	This file is exempted from having a test file; skipping coverage check.
QuestionPlayerActivityPresenter.kt app/src/main/java/org/oppia/android/app/topic/questionplayer/QuestionPlayerActivityPresenter.kt	This file is exempted from having a test file; skipping coverage check.
QuestionPlayerFragmentPresenter.kt app/src/main/java/org/oppia/android/app/topic/questionplayer/QuestionPlayerFragmentPresenter.kt	This file is exempted from having a test file; skipping coverage check.
QuestionPlayerActivity.kt app/src/main/java/org/oppia/android/app/topic/questionplayer/QuestionPlayerActivity.kt	This file is incompatible with code coverage tooling; skipping coverage check.
QuestionAssessmentProgressController.kt domain/src/main/java/org/oppia/android/domain/question/QuestionAssessmentProgressController.kt	This file is incompatible with code coverage tooling; skipping coverage check.
ExplorationProgressController.kt domain/src/main/java/org/oppia/android/domain/exploration/ExplorationProgressController.kt	This file is incompatible with code coverage tooling; skipping coverage check.
HintHandlerDebugImpl.kt domain/src/main/java/org/oppia/android/domain/hintsandsolution/HintHandlerDebugImpl.kt	This file is incompatible with code coverage tooling; skipping coverage check.
HintHandler.kt domain/src/main/java/org/oppia/android/domain/hintsandsolution/HintHandler.kt	This file is exempted from having a test file; skipping coverage check.
HintsAndSolutionDebugModule.kt domain/src/main/java/org/oppia/android/domain/hintsandsolution/HintsAndSolutionDebugModule.kt	This file is incompatible with code coverage tooling; skipping coverage check.
HintsAndSolutionProdModule.kt domain/src/main/java/org/oppia/android/domain/hintsandsolution/HintsAndSolutionProdModule.kt	This file is incompatible with code coverage tooling; skipping coverage check.
HintHandlerProdImpl.kt domain/src/main/java/org/oppia/android/domain/hintsandsolution/HintHandlerProdImpl.kt	This file is incompatible with code coverage tooling; skipping coverage check.

Refer test_file_exemptions.textproto for the comprehensive list of file exemptions and their required coverage percentages.

To learn more, visit the Oppia Android Code Coverage wiki page

[Kishan8548]

@adhiamboperes PTAL

I've opened this draft PR with the implementation for pausing and resuming the hint timer when the hints/solution dialog is open, along with unit tests for HintHandler and controllers. Looking forward to your feedback to ensure we're going in the right direction!