refactor: modularize 3.2K-line usage.ts (Issue #3594)

[oyi77]

Clean re-cut of PR #3645 — modularizes open-sse/services/usage.ts (3393→633 lines) into 25 focused modules under open-sse/services/usage/.

Cherry-picked only the modularization commit (23029463e) onto current release/v3.8.24. No unrelated changes.

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive usage fetching module under open-sse/services/usage/ to retrieve and parse quota and usage data from various AI providers. The review feedback highlights critical circular dependency issues, specifically a large dependency web created by the __testing export in utils.ts and a direct circular dependency between antigravity.ts and gemini.ts. Additionally, a potential bug was identified in kimi.ts where multiple rate limits would overwrite the quotas["Ratelimit"] key, which can be resolved by using unique keys.

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[gemini-code-assist]

The __testing object imports functions from almost every provider file (github.ts, gemini.ts, antigravity.ts, minimax.ts, opencode.ts, claude.ts, and xiaomi.ts), while those provider files simultaneously import core utility functions from utils.ts. This creates a massive circular dependency web across the entire usage/ module, which can lead to runtime issues where imported bindings are undefined during module initialization.

Since these functions are already exported from their respective files, unit tests can (and should) import them directly from their source modules rather than through utils.ts. Removing the __testing export and its associated imports will completely break this circular dependency web.

export {};

[gemini-code-assist]

There is a direct circular dependency between antigravity.ts and gemini.ts:

1. antigravity.ts imports _geminiCliSubCache from gemini.ts to clean it up in this global setInterval timer.
2. gemini.ts imports mapCodeAssistSubscriptionToPlanLabel from antigravity.ts to implement getGeminiCliPlanLabel.

To resolve this:

• Move the cache cleanup logic for _geminiCliSubCache into gemini.ts (either via its own interval or passive cleanup).
• Move mapCodeAssistSubscriptionToPlanLabel and its helper functions from antigravity.ts to utils.ts (or a dedicated subscriptionUtils.ts file) so both modules can import it from a common utility file without circular dependencies.

[gemini-code-assist]

If limitsArray contains multiple rate limits (e.g., RPM and TPM limits), they will all write to quotas["Ratelimit"], meaning only the last limit in the array will be preserved and displayed on the dashboard.

To prevent overwriting, we should use a unique key for each rate limit if there are multiple items.

    const limitsArray = Array.isArray(dataObj.limits) ? dataObj.limits : [];
    for (let i = 0; i < limitsArray.length; i++) {
      const limitItem = toRecord(limitsArray[i]);
      const window = toRecord(limitItem.window);
      const detail = toRecord(limitItem.detail);

      const limit = toNumber(detail.limit || detail.Limit, 0);
      const remaining = toNumber(detail.remaining || detail.Remaining, 0);
      const resetTime = detail.resetTime || detail.reset_at || detail.resetAt;

      if (limit > 0) {
        const key = limitsArray.length > 1 ? `Ratelimit_${i + 1}` : "Ratelimit";
        quotas[key] = {
          used: limit - remaining,
          total: limit,
          remaining,
          remainingPercentage: limit > 0 ? (remaining / limit) * 100 : 0,
          resetAt: parseResetTime(resetTime),
          unlimited: false,
        };
      }
    }

[oyi77]

Superseded by #3989 — re-cut as a small, independent, non-stacked PR from release/v3.8.27. Closing this stacked version.