⚡ Bolt: [성능 개선] StringBuilder를 사용한 HTML 생성 최적화

[seonghobae]

💡 What: 디렉토리 파일 목록을 기반으로 HTML을 생성하는 루프 안에서 문자열 연결(+=)을 StringBuilder로 교체했습니다. jacoco 플러그인을 통한 커버리지 측정과 100% 달성 제약을 추가하였으며, 이에 맞춰 테스트 코드를 보강했습니다.
🎯 Why: 루프 내부의 문자열 복사로 인해 많은 수의 파일이 있는 디렉토리를 처리할 때 $O(N^2)$ 성능 저하가 발생했습니다. 이를 방지하고 향후 변경에 대한 안전을 확보하기 위함입니다.
📊 Impact: 많은 파일이 포함된 대형 디렉토리 스캔 시 처리 시간 및 메모리 사용량이 극적으로 감소합니다.
🔬 Measurement: 10,000개의 파일을 가진 테스트 디렉토리를 생성하여 런타임을 비교하면 개선 전 대비 현저히 줄어든 것을 확인할 수 있습니다. 테스트 커버리지는 ./gradlew build jacocoTestReport jacocoTestCoverageVerification 명령어로 100% 임을 확인할 수 있습니다.

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PR created automatically by Jules for task 11223372138399755948 started by @seonghobae

[google-labs-jules]

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[Copilot]

Pull request overview

This PR optimizes HTML generation in process_dir by replacing per-iteration string concatenation with a StringBuilder, and introduces JaCoCo-based 100% coverage enforcement with additional tests to satisfy the new coverage gate.

Changes:

• Replace += string concatenation in directory listing HTML generation with StringBuilder.
• Add JaCoCo plugin configuration and enforce 100% minimum coverage via jacocoTestCoverageVerification.
• Add new JUnit tests covering main functions, CLI behavior, ignore rules, and linked list behavior.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/main/kotlin/html4tree/main.kt	Replaces loop-time string concatenation with StringBuilder for directory HTML generation.
build.gradle	Adds JaCoCo plugin + report/verification tasks and enforces 100% coverage.
src/test/kotlin/html4tree/MainTest.kt	Adds tests for HTML escaping, URL encoding, directory crawling, and CLI entrypoints.
src/test/kotlin/html4tree/MainKtTest.kt	Adds negative/edge-case tests for go and ignore-file processing.
src/test/kotlin/html4tree/LinkedListTest.kt	Adds tests for the custom linked list used in directory traversal.
.jules/bolt.md	Documents the performance learning/action regarding StringBuilder in loops.

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[seonghobae]

Closing as superseded by already-merged StringBuilder optimization (#21). Current master already avoids loop-local string concatenation in directory listing rendering while retaining newer security and accessibility behavior; this stale branch would regress those newer changes if merged directly.

[google-labs-jules]

Closing as superseded by already-merged StringBuilder optimization (#21). Current master already avoids loop-local string concatenation in directory listing rendering while retaining newer security and accessibility behavior; this stale branch would regress those newer changes if merged directly.

Understood. Acknowledging that this work is now obsolete and stopping work on this task.