Reuse legacy cache stat results in cache statistics

[Copilot]

Canonical issue

System-linked.

Outcome

Legacy cache statistics now reuse a single filesystem stat per *_analysis.md file while preserving identical category counts, sizes, and oldest/newest timestamps.

• Service change
  • CacheService._analyze_legacy_cache_stats now materializes (path, stat) pairs once and reuses the cached metadata for size and mtime aggregation.
• Regression coverage
  • Strengthens the existing unit test to assert one Path.stat() call per legacy analysis file and unchanged oldest/newest timestamp output.

markdown_file_stats = [
    (file_path, file_path.stat())
    for file_path in category_dir.glob("*_analysis.md")
]

for _file_path, file_stats in markdown_file_stats:
    category_size += file_stats.st_size
    mtime = file_stats.st_mtime

Scope

• Included:
  • src/youtube_extension/backend/services/cache_service.py
  • tests/unit/test_cache_service.py
• Explicitly excluded:
  • Enhanced cache paths
  • Cache lookup / invalidation behavior
  • API surface changes

Risk

• Risk level: low
• Failure mode:
  • Legacy cache stats could report incorrect size or timestamp aggregation if stat reuse changed the loop semantics.
• Rollback:
  • Revert the cache-service loop and regression test changes in this PR.

Verification

List exact automated and manual checks, tied to the current head SHA.

• Focused tests
• Required CI
• Review threads resolved

Production evidence

Not applicable. This is an internal backend cache-statistics refactor with no production UI, deploy, or runtime contract change.

Agent handoff

• One canonical issue is linked
• No competing PR implements the same issue
• Acceptance criteria are satisfied
• Required checks pass on the current head
• Human decision is requested only for product, security, irreversible infrastructure, or production approval

• Fixes Reuse legacy cache file stat results to avoid duplicate syscalls #2029

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Project	Deployment	Actions	Updated
v0-uvai	Ready	Preview, v0	Sep 18, 2026 10:05pm UTC

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Pull request overview

Refactors legacy cache statistics to reuse a single filesystem stat() call per *_analysis.md file while keeping aggregate counts/sizes/timestamps identical.

Changes:

• Materialize (path, stat) pairs once in CacheService._analyze_legacy_cache_stats and reuse metadata for aggregation.
• Strengthen unit test to assert exactly one Path.stat() call per legacy analysis file.
• Extend unit test to assert unchanged oldest_cache / newest_cache outputs using controlled mtimes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/youtube_extension/backend/services/cache_service.py	Reuses pre-fetched stat results instead of calling Path.stat() inside the aggregation loop.
tests/unit/test_cache_service.py	Adds regression assertions for stat() call counts and for oldest/newest timestamps based on deterministic mtimes.

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[groupthinking]

@copilot Fix the code for all comments in this review comment.

When a review comment includes a suggested change, apply the suggestion exactly.

Do not make changes beyond what is described in the linked review comment.

[github-actions]

🔍 PR Validation

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