test: add coverage for internal/analytics + binder-ambiguity fix (#8)

[detour1999]

Summary

Closes #8.

First tests for the `internal/analytics` package. Also carries a small incidental fix to `queries.go` that the tests surfaced.

What's tested

Real SQLite fixture → real parquet export → real DuckDB queries. No mocks.

• `Exporter.Export` — parquet round-trip produces a non-empty file at the expected path
• `SessionsParquetHasSource` — missing file → false; fresh file → true; synthetic legacy file (pre-feat: plugin architecture for multi-source session support #6 schema, no source column) → false
• `GetSummary`, `GetTokensByDay`, `GetTopProjects`, `GetTokensByModel` — full query coverage over a multi-source fixture; aggregations verified against known totals
• `GetTokensBySource`, `GetSessionsBySource` — multi-source aggregation
• Missing-cache error paths for all six query methods
• Legacy parquet + source query → clean error (not misleading rows)

The legacy-parquet tests use a synthetic `legacySessionRecord` written directly via `parquet-go` to simulate a pre-multi-source cache.

Incidental fix

The `COALESCE(source, 'claude-code') as source ... GROUP BY COALESCE(source, ...)` fallback in `GetTokensBySource`/`GetSessionsBySource` was aspirational: on a legacy parquet without a source column, DuckDB's binder shadowed the missing column with the SELECT alias named `source` and errored inside the COALESCE with a confusing message.

Renamed the alias to `source_out` and switched to `GROUP BY 1` so the error is now the honest "Referenced column source not found in FROM clause." `rows.Scan` is positional, so Go-side struct mapping is unchanged.

The COALESCE fallback still can't rescue legacy parquets (DuckDB errors at bind-time regardless), but callers hit the `SessionsParquetHasSource + rebuild` guard in the TUI before running these queries. The test suite documents this.

Test plan

• 12 new tests passing
• Full suite green under `-race -count=1`

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Summary by CodeRabbit

• Bug Fixes

  • Improved analytics queries for compatibility with both current and legacy session data.
  • Fixed source-based token and session breakdowns when analyzing older cached data.
  • Improved handling of missing or incompatible analytics data, with clearer failure behavior.

• Tests

  • Expanded coverage for analytics exports, summaries, daily trends, and breakdowns by project, model, and source.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 87e0b23 and 302bb23.

📒 Files selected for processing (2)

• internal/analytics/analytics_test.go
• internal/analytics/queries.go

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Walkthrough

Analytics tests now use SQLite, Parquet, and DuckDB fixtures. They verify exports, schema detection, aggregations, legacy-cache behavior, and missing-cache errors. Source queries now use explicit aliases and positional grouping for legacy Parquet compatibility.

Changes

Analytics coverage and compatibility

Layer / File(s)	Summary
Analytics fixtures and Parquet schema coverage internal/analytics/analytics_test.go	Tests seed varied sessions, verify Parquet export, and detect current, legacy, and missing cache schemas.
Source query compatibility internal/analytics/queries.go, internal/analytics/analytics_test.go	Source token and session queries use source_out with positional grouping. Legacy-cache tests verify source-query errors.
Aggregation and cache error validation internal/analytics/analytics_test.go	Integration tests validate summary, daily, project, model, and source aggregations. Missing-cache tests verify error returns.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

• 2389-research/ccvault#10: Covers related analytics cache availability and query error handling.

Poem

A rabbit checks each cache with care,
Parquet rows hop everywhere.
Sources group by names anew,
Legacy paths behave as due.
Missing files now raise a sound—
Clean analytics all around!

✨ 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 test/analytics-coverage

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