ccs/docs/code-standards.md

CCS Code Standards

Last Updated: 2025-12-21

Code standards, modularization patterns, and conventions for the CCS codebase.

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Core Principles

YAGNI (You Aren't Gonna Need It)

• No features "just in case"
• Only implement what is currently needed
• Delete unused code rather than commenting it out

KISS (Keep It Simple, Stupid)

• Prefer simple solutions over clever ones
• Reduce complexity at every opportunity
• Use established patterns over custom implementations

DRY (Don't Repeat Yourself)

• One source of truth for configuration
• Extract common logic into shared utilities
• Use barrel exports to centralize imports

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File Organization

Directory Structure Rules

1. Domain-based organization: Group files by business domain, not by file type
2. Barrel exports required: Every directory must have an index.ts aggregating exports
3. Flat within depth: Keep nesting to 3 levels maximum
4. Co-location: Keep related files together (component + hooks + utils)

File Naming Conventions

Convention	Example	When to Use
kebab-case	cliproxy-executor.ts	All TypeScript/TSX files
kebab-case	profile-detector.ts	Multi-word file names
PascalCase	BinaryManager	Class exports only
camelCase	detectProfile	Function exports

File names should be descriptive: LLMs should understand the file's purpose from its name alone without reading content.

Correct Examples

src/cliproxy/binary-manager.ts      # Binary management logic
src/commands/doctor-command.ts      # Doctor CLI command handler
ui/src/components/cliproxy/provider-editor/index.tsx

Incorrect Examples

src/utils/helper.ts                 # Too vague
src/cliproxy/manager.ts             # Which manager?
ui/src/components/Editor.tsx        # Not kebab-case

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File Size Limit: 200 Lines

Target: All code files should be under 200 lines.

Exceptions (with justification):

• Data files (model-pricing.ts, model-catalog.ts)
• Entry points with routing logic (ccs.ts)
• Complex transformation logic that cannot be meaningfully split

Why 200 Lines?

1. Context efficiency: LLMs process smaller files faster
2. Single responsibility: Forces focused, testable modules
3. Navigation: Easier to scan and understand
4. Maintainability: Reduces merge conflicts

When Files Exceed 200 Lines

If a file grows beyond 200 lines:

1. Identify extraction candidates:

   • Helper functions that could be utilities
   • Constants and type definitions
   • Subcomponents within React components
   • Related logic that forms a cohesive unit

2. Create subdirectory structure:

   # Before
   provider-editor.tsx (921 lines)
   
   # After
   provider-editor/
   ├── index.tsx           # Main component (200 lines)
   ├── model-mapping-form.tsx
   ├── endpoint-config.tsx
   ├── auth-section.tsx
   ├── hooks.ts
   ├── types.ts
   └── utils.ts
   

3. Preserve public API: Main export remains the same through barrel export

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Barrel Export Pattern

What is a Barrel Export?

An index.ts file that aggregates and re-exports module contents:

// src/cliproxy/index.ts

// Types (with explicit type keyword)
export type { PlatformInfo, BinaryInfo } from './types';

// Functions
export { detectPlatform } from './platform-detector';
export { BinaryManager } from './binary-manager';

// From subdirectories
export * from './auth';
export * from './services';

Rules for Barrel Exports

1. Every domain directory must have index.ts
2. Export types with export type for tree-shaking
3. Re-export subdirectories for deep access
4. Keep barrel exports flat - no logic, only exports

Import Patterns

// CORRECT: Import from domain barrel
import { execClaudeWithCLIProxy, CLIProxyProvider } from '../cliproxy';
import { Config, Settings } from '../types';

// INCORRECT: Import from specific file (bypasses barrel)
import { execClaudeWithCLIProxy } from '../cliproxy/cliproxy-executor';

Exception: Deep Imports

Allowed when:

• Importing private utilities not exposed in barrel
• Circular dependency avoidance
• Performance-critical tree-shaking

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Monster File Splitting Methodology

When splitting large files (500+ lines), follow this process:

Step 1: Analyze Structure

Identify logical boundaries:

• Render sections in React components
• Handler groups in route files
• Related utility functions
• Constants and types

Step 2: Extract Types First

// types.ts
export interface ProviderEditorProps {
  providerId: string;
  onSave: (config: ProviderConfig) => void;
}

export interface ModelMappingValues {
  model: string;
  endpoint: string;
}

Step 3: Extract Utilities

// utils.ts
export function validateEndpoint(url: string): boolean { ... }
export function formatModelName(name: string): string { ... }

Step 4: Extract Hooks

// hooks.ts
export function useProviderConfig(providerId: string) { ... }
export function useModelValidation() { ... }

Step 5: Extract Subcomponents

// model-mapping-form.tsx
export function ModelMappingForm({ values, onChange }: Props) { ... }

Step 6: Compose in Index

// index.tsx
import { ModelMappingForm } from './model-mapping-form';
import { useProviderConfig } from './hooks';
import type { ProviderEditorProps } from './types';

export function ProviderEditor({ providerId, onSave }: ProviderEditorProps) {
  const config = useProviderConfig(providerId);
  return (
    <div>
      <ModelMappingForm values={config.mapping} onChange={...} />
    </div>
  );
}

// Re-export types for consumers
export type { ProviderEditorProps, ModelMappingValues } from './types';

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TypeScript Standards

Strict Mode Required

All projects use TypeScript strict mode:

{
  "compilerOptions": {
    "strict": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true
  }
}

Type Annotations

// CORRECT: Explicit return types for public functions
export function detectProfile(args: string[]): DetectedProfile { ... }

// CORRECT: Inferred types for internal functions
const formatName = (name: string) => name.trim().toLowerCase();

// INCORRECT: any type
function processData(data: any) { ... }  // Use unknown or proper type

Type Exports

// CORRECT: Use type keyword for type-only exports
export type { Config, Settings } from './config';

// CORRECT: Group type exports in barrel
export type {
  PlatformInfo,
  BinaryInfo,
  DownloadProgress,
} from './types';

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ESLint Rules (Enforced)

Rule	Level	Notes
@typescript-eslint/no-unused-vars	error	Ignore _ prefix
@typescript-eslint/no-explicit-any	error	Use proper types
@typescript-eslint/no-non-null-assertion	error	No ! assertions
prefer-const	error	Immutable by default
no-var	error	Use const/let
eqeqeq	error	Strict equality
react-hooks/*	recommended	(UI only)

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Terminal Output Standards

ASCII Only

// CORRECT
console.log('[OK] Operation successful');
console.log('[!] Warning message');
console.log('[X] Error occurred');
console.log('[i] Information');

// INCORRECT - NO EMOJIS
console.log('Operation successful');  // NO
console.log('Warning message');       // NO

Color Handling

import { colors } from '../utils/ui';

// Colors are TTY-aware and respect NO_COLOR
console.log(colors.green('[OK]') + ' Operation successful');

Box Borders

Use ASCII box drawing for error displays:

+=====================================+
|  [X] ERROR: Configuration failed    |
|                                     |
|  Details: Unable to parse config    |
+=====================================+

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React Component Standards (UI)

Component Structure

// component-name.tsx

// 1. Imports (grouped: react, external, internal, relative)
import { useState } from 'react';
import { Button } from '@/components/ui/button';
import { useProfiles } from '@/hooks';
import { formatName } from './utils';
import type { ComponentProps } from './types';

// 2. Types (if not in separate file)
interface Props {
  id: string;
  onSave: () => void;
}

// 3. Component
export function ComponentName({ id, onSave }: Props) {
  // Hooks first
  const profiles = useProfiles();
  const [state, setState] = useState(null);

  // Handlers
  const handleClick = () => { ... };

  // Render
  return ( ... );
}

Naming Conventions

Item	Convention	Example
Component files	kebab-case.tsx	provider-editor.tsx
Component exports	PascalCase	ProviderEditor
Hook files	use-*.ts	use-profiles.ts
Hook exports	useCamelCase	useProfiles
Utility files	kebab-case.ts	path-utils.ts
Utility exports	camelCase	formatPath

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Input State Persistence Patterns

When building forms and editors that allow users to make changes, follow these patterns to prevent data loss.

Pattern 1: Key-Based Remounting

Use when: Component has complex local state that should reset on prop changes.

// Parent component
<ProfileEditor
  key={profileId}  // Forces remount when profile changes
  profileId={profileId}
  onSave={handleSave}
/>

Why: Without key, React reuses the component instance. Local useState values persist even when props change, causing stale data bugs.

Pattern 2: Unsaved Changes Confirmation

Use when: User might navigate away while editing.

// Parent tracks dirty state
const [editorHasChanges, setEditorHasChanges] = useState(false);
const [pendingSwitch, setPendingSwitch] = useState<string | null>(null);

// Child notifies parent of dirty state
useEffect(() => {
  onHasChangesUpdate?.(computedHasChanges);
}, [computedHasChanges, onHasChangesUpdate]);

// Intercept navigation
const handleSelect = (id: string) => {
  if (editorHasChanges && currentId !== id) {
    setPendingSwitch(id);  // Show confirmation dialog
  } else {
    setCurrentId(id);
  }
};

Flow:

1. Child computes hasChanges from local state vs saved data
2. Child notifies parent via callback
3. Parent intercepts navigation when dirty
4. Show confirmation dialog: "Discard & Switch" or "Cancel"
5. On confirm: reset dirty state, then switch

Pattern 3: Auto-Save with Visual Feedback

Use when: Simple inputs that should save immediately.

const [saved, setSaved] = useState(false);

const handleBlur = async () => {
  if (value !== savedValue) {
    await saveToBackend(value);
    setSaved(true);
    setTimeout(() => setSaved(false), 2000);
  }
};

return (
  <div className="flex items-center gap-2">
    <Input value={value} onChange={...} onBlur={handleBlur} />
    {saved && (
      <span className="text-green-600 text-xs flex items-center gap-1">
        <Check className="w-3.5 h-3.5" /> Saved
      </span>
    )}
  </div>
);

When to use which:

Scenario	Pattern
Complex multi-field editor	Pattern 2 (confirmation dialog)
Simple single input	Pattern 3 (auto-save + feedback)
List item selection	Pattern 1 (key-based remount) + Pattern 2

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Quality Gates

Pre-Commit Sequence

# Main project
bun run format
bun run lint:fix
bun run validate

# UI project (if changed)
cd ui
bun run format
bun run lint:fix
bun run validate

Validate Runs

Project	Command	Checks
Main	bun run validate	typecheck + lint + format:check + test
UI	bun run validate	typecheck + lint + format:check

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Conventional Commits

All commits must follow conventional commit format:

<type>(<scope>): <description>

Types

Type	When to Use	Version Bump
feat	New feature	MINOR
fix	Bug fix	PATCH
perf	Performance	PATCH
docs	Documentation	None
style	Formatting	None
refactor	Code restructure	None
test	Tests	None
chore	Maintenance	None

Examples

# Correct
git commit -m "feat(cliproxy): add OAuth token refresh"
git commit -m "fix(doctor): handle missing config gracefully"
git commit -m "refactor(ui): split provider-editor into modules"

# Incorrect - REJECTED
git commit -m "added new feature"
git commit -m "Fixed bug"

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Anti-Patterns to Avoid

1. God Files

// BAD: One file doing everything
// src/utils.ts (2000 lines with mixed concerns)

// GOOD: Split by domain
// src/utils/ui/colors.ts
// src/utils/ui/boxes.ts
// src/utils/shell-executor.ts
// src/utils/config-manager.ts

2. Barrel Import Bypass

// BAD: Direct import bypassing barrel
import { detectPlatform } from '../cliproxy/platform-detector';

// GOOD: Import from domain barrel
import { detectPlatform } from '../cliproxy';

3. Inline Everything

// BAD: Huge inline functions in components
function Component() {
  const handleComplexOperation = () => {
    // 100 lines of logic...
  };
}

// GOOD: Extract to hooks or utilities
function Component() {
  const { handleComplexOperation } = useComplexOperation();
}

4. Type Duplication

// BAD: Same types defined in multiple files
// file1.ts
interface Config { ... }
// file2.ts
interface Config { ... }

// GOOD: Single source of truth
// types/config.ts
export interface Config { ... }

5. Config Priority Pattern

When resolving configuration from multiple sources, follow this priority order:

// proxy-config-resolver.ts pattern
// Priority: CLI flags > Environment variables > config.yaml > defaults

const resolved = {
  ...DEFAULT_CONFIG,                    // 4. Defaults (lowest)
  ...yamlConfig,                        // 3. config.yaml
  ...envConfig,                         // 2. Environment variables
  ...cliFlags,                          // 1. CLI flags (highest)
};

This pattern is used in:

• src/cliproxy/proxy-config-resolver.ts - Remote proxy config
• src/config/unified-config-loader.ts - Main config loading

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Related Documentation

• Codebase Summary - Full directory structure
• System Architecture - Architecture diagrams
• CLAUDE.md - AI-facing development guidance