refactor(gateway): extract some functions

[steebchen]

Summary by CodeRabbit

• Improvements
  • Enhanced error messaging when unsupported models or providers are requested, with suggested usage formats.
  • Improved reliability of model and provider routing, including better handling of deactivated providers during selection.
  • Support for multiple model input formats including auto, custom, provider-scoped, direct model IDs, and custom OpenAI-compatible providers.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

This PR refactors model and provider resolution logic in the gateway's chat module by extracting inline parsing and validation into dedicated helper functions. Two new utilities—parseModelInput and resolveModelInfo—centralize model string parsing and provider deactivation filtering. The Model type dependency is removed where runtime strings suffice.

Changes

Cohort / File(s)	Summary
New Model Resolution Utilities apps/gateway/src/chat/tools/parse-model-input.ts, apps/gateway/src/chat/tools/resolve-model-info.ts	Introduces parseModelInput to parse user-provided model input strings into model, provider, and optional custom provider name; introduces resolveModelInfo to resolve model definitions, filter deactivated providers, and update provider selection accordingly.
Chat Logic Refactoring apps/gateway/src/chat/chat.ts	Replaces ad-hoc model parsing and provider resolution with calls to new helper functions; removes Model type import; simplifies control flow by consolidating model/provider routing logic.
Type Simplification apps/gateway/src/lib/costs.ts	Changes calculateCosts function signature to accept model as a string instead of Model type; removes Model type import.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• feat(costs): adapt image output pricing and tracking #1207 — Modifies the calculateCosts function signature and chat.ts cost integration, directly impacted by the model type simplification in this PR.
• fix(chat): tool calls fixes & e2e tests #675 — Adjusts model/provider routing and auto-model selection in chat.ts, which overlaps with the refactored routing logic introduced here.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Title check	❓ Inconclusive	The title 'refactor(gateway): extract some functions' is vague and uses non-descriptive language; 'extract some functions' does not convey what functionality is being refactored or why.	Consider a more specific title like 'refactor(gateway): extract model parsing and resolution helpers' to better communicate the purpose of the refactoring.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch steebchen/batch-api-phase2

Tip

🧪 Unit Test Generation v2 is now available!

We have significantly improved our unit test generation capabilities.

To enable: Add this to your .coderabbit.yaml configuration:

reviews:
  finishing_touches:
    unit_tests:
      enabled: true

Try it out by using the @coderabbitai generate unit tests command on your code files or under ✨ Finishing Touches on the walkthrough!

Have feedback? Share your thoughts on our Discord thread!

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}