[diegosouzapw]

#3500 (slice 2) — usage_history / daily_usage_summary cluster

The biggest slice: /api/usage/analytics had 15 inline queries + 2 CTE builders, and /api/settings/export-json had 3 full-table reads. All moved into a new src/lib/db/usageAnalytics.ts (18 fns + 2 CTE builders) plus a getFallbackStats helper on callLogStats.ts. Queries byte-identical.

Validation

• ✅ db-rules gate OK — KNOWN_RAW_SQL 10 → 8; both routes 0 db-markers
• ✅ TDD: 21/21 (temp SQLite + resetDbInstance() teardown)
• ✅ typecheck:core clean; lint 0 errors
• ℹ️ usageAnalytics.ts (873 LOC, flat query module) frozen in file-size-baseline — consistent with the other large db/ modules already there; the 800 cap targets god-components.

Part of #3500. Combined with slices 1 & 3, the call_logs / usage / gamification clusters are now gate-clean.

[gemini-code-assist]

Code Review

This pull request refactors database interactions by extracting inline raw SQL queries from the /api/usage/analytics and /api/settings/export-json route handlers into a new domain module, src/lib/db/usageAnalytics.ts, and extending src/lib/db/callLogStats.ts with getFallbackStats. This aligns with the repository's architectural rules regarding raw SQL encapsulation. The changes are supported by a new suite of unit tests in tests/unit/db-usage-analytics-3500.test.ts. Feedback on the changes highlights a potential TypeScript type violation in getFallbackStats where SUM aggregates can return null instead of 0 when no rows match, and points out a redundant column selection for serviceTier in getServiceTierUsageRows.

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[gemini-code-assist]

In SQLite, a SELECT query with aggregate functions (like SUM) and no GROUP BY always returns exactly one row, even if no rows match the WHERE clause. However, if no rows match, the SUM aggregates will evaluate to null.

Since row is defined, the nullish coalescing operator row ?? { ... } on line 234 will evaluate to row, returning an object with null values (e.g., { total: null, ... }). This violates the FallbackStatsRow TypeScript interface where all fields are typed as number, potentially causing runtime issues or NaN values in calculations.

Using COALESCE(SUM(...), 0) in the SQL query guarantees that the fields always return 0 instead of null when no matching rows are found.

  const row = db
    .prepare(
      `
      SELECT
        COALESCE(SUM(CASE WHEN (combo_name IS NULL OR combo_name = '') THEN 1 ELSE 0 END), 0) as total,
        COALESCE(SUM(CASE WHEN requested_model IS NOT NULL AND requested_model != '' AND (combo_name IS NULL OR combo_name = '') THEN 1 ELSE 0 END), 0) as with_requested,
        COALESCE(SUM(CASE
          WHEN (combo_name IS NULL OR combo_name = '')
           AND requested_model IS NOT NULL
           AND requested_model != ''
           AND model IS NOT NULL
           AND model != ''
          THEN 1 ELSE 0 END
        ), 0) as fallback_eligible,
        COALESCE(SUM(CASE
          WHEN (combo_name IS NULL OR combo_name = '')
           AND requested_model IS NOT NULL
           AND requested_model != ''
           AND model IS NOT NULL
           AND model != ''
           AND LOWER(CASE WHEN instr(requested_model, '/') > 0 THEN substr(requested_model, instr(requested_model, '/') + 1) ELSE requested_model END) != LOWER(model)
          THEN 1 ELSE 0 END
        ), 0) as fallbacks
      FROM call_logs
      ${whereClause}
    `
    )
    .get(params) as FallbackStatsRow | undefined;

[gemini-code-assist]

The serviceTier column is selected twice in the query, which is redundant and can be cleaned up to improve query readability and avoid potential parser/driver conflicts.

Suggested change

	SELECT
	COALESCE(NULLIF(service_tier, ''), 'standard') as serviceTier,
	LOWER(provider) as provider,
	LOWER(model) as model,
	COALESCE(NULLIF(service_tier, ''), 'standard') as serviceTier,
	COUNT(*) as requests,
	SELECT
	COALESCE(NULLIF(service_tier, ''), 'standard') as serviceTier,
	LOWER(provider) as provider,
	LOWER(model) as model,
	COUNT(*) as requests,