fix(route): map small return gaps to Seoul

[ccjngwn]

What changed

• Treat return-route midpoint gaps of 15 minutes or less as Seoul(BASE) instead of querying city candidates.
• Added a service test that verifies WEST 15 maps to Seoul and does not call the city candidate lookup.

Why

A return route such as 03:00~10:00 -> 23:00~07:00 can produce a tiny remaining gap right before arrival, for example WEST 15. The city mapping table does not cover that range, so route creation failed before saving.

Validation

• ./gradlew test --tests com.cotato.cokerthon.domain.route.service.ReturnRouteServiceTest
• ./gradlew test

Summary by CodeRabbit

• Bug Fixes
  • Improved return-route selection near Seoul by falling back to Seoul when the route gap is 15 minutes or less.
  • Prevented unnecessary city searches in these short-gap scenarios, providing more consistent route results.

[coderabbitai]

📝 Walkthrough

Walkthrough

ReturnRouteService now selects Seoul for base directions or gaps of 15 minutes or less. Tests cover the WEST 15-minute case by asserting the saved checkpoint city and confirming no candidate-city lookup occurs.

Changes

Return-route Seoul fallback

Layer / File(s)	Summary
Fallback selection and validation src/main/java/com/cotato/cokerthon/domain/route/service/ReturnRouteService.java, src/test/java/com/cotato/cokerthon/domain/route/service/ReturnRouteServiceTest.java	Adds the 15-minute fallback threshold to pickRandomCity and tests that a WEST 15-minute route saves Seoul without querying city candidates.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: mapping small return gaps to Seoul.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/return-route-small-gap-seoul

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[coderabbitai]

🧹 Nitpick comments (1)

src/test/java/com/cotato/cokerthon/domain/route/service/ReturnRouteServiceTest.java (1)

131-160: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Add threshold boundary coverage.

This test validates WEST 15, but parameterized cases for -15 and 16 would also prove both-direction fallback and that candidate lookup resumes above the threshold.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@src/test/java/com/cotato/cokerthon/domain/route/service/ReturnRouteServiceTest.java`
around lines 131 - 160, Add parameterized boundary cases to
createReturnRouteMapsWest15MinutesToSeoulWithoutFindingCityCandidates (or
extract a shared parameterized test) covering gap values -15 and 16 in addition
to WEST 15. Assert -15 also falls back to the BASE/Seoul checkpoint without
candidate lookup, while 16 resumes
cityRepository.findAllByDirectionAndGapMinutes with the expected direction and
gap.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In
`@src/test/java/com/cotato/cokerthon/domain/route/service/ReturnRouteServiceTest.java`:
- Around line 131-160: Add parameterized boundary cases to
createReturnRouteMapsWest15MinutesToSeoulWithoutFindingCityCandidates (or
extract a shared parameterized test) covering gap values -15 and 16 in addition
to WEST 15. Assert -15 also falls back to the BASE/Seoul checkpoint without
candidate lookup, while 16 resumes
cityRepository.findAllByDirectionAndGapMinutes with the expected direction and
gap.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8f905509-49a7-4a82-bd75-4309ec6b4354

📥 Commits

Reviewing files that changed from the base of the PR and between 47aa53b and cea01df.

📒 Files selected for processing (2)

• src/main/java/com/cotato/cokerthon/domain/route/service/ReturnRouteService.java
• src/test/java/com/cotato/cokerthon/domain/route/service/ReturnRouteServiceTest.java