Pattern Detector

Analyze ANY codebase to learn existing API patterns. Works with any framework, structure, or convention.

EXECUTION INSTRUCTIONS

When this skill is invoked, Claude MUST perform these steps in order:

Step 1: Read package.json

1. Use Read tool to read package.json in project root
2. Extract dependency information:

- dependencies - devDependencies

1. If package.json not found → Report error and abort

Step 2: Detect Framework Stack

From package.json, identify:

Report findings:

📦 package.json analysis:
  Framework: <framework> + <language>
  HTTP Client: <httpClient or "fetch (native)">
  Data Fetching: <dataFetching or "none detected">

Step 3: Search for Existing API Code

Use Glob tool with these patterns in order:

1. src/**/api/**/*.{ts,js,tsx,jsx}
2. src/**/services/**/*.{ts,js}
3. src/**/hooks/**/*{api,query,fetch}*.{ts,js}
4. lib/api/**/*.{ts,js}
5. api/**/*.{ts,js}

If NO files found:

• Report: 🔍 No existing API code found
• Skip to Step 6 (Interactive Fallback)

If files found:

• Report: 🔍 Found <count> potential API files
• Continue to Step 4

Step 4: Analyze Sample Files

For each discovered file (max 5 files):

1. Use Read tool to read file content
2. Extract patterns:

- Import patterns: What modules are imported, how (named, default, namespace) - Export patterns: Named exports, default exports, barrel exports - Function patterns: Arrow vs declaration, async, parameter style - HTTP call patterns: How HTTP requests are made - Type patterns: Interface vs type, naming conventions - Hook patterns: If React Query/SWR hooks present

1. Record findings in structured format:

`` File: <path> - Imports: <pattern> - Exports: <pattern> - Functions: <pattern> - HTTP: <pattern> - Types: <pattern> ``

Step 5: Synthesize Patterns

1. Compare patterns across all analyzed files
2. Calculate majority pattern for each category
3. Calculate confidence score (percentage of files matching majority)
4. Report findings:

📂 Detected patterns:
  Structure: <pattern> (confidence: <X>%)
  HTTP Client: <pattern>
  Data Fetching: <pattern>
  Types: <pattern>
  Naming: <pattern>

📁 Sample files:
  API: <best sample path>
  Types: <best sample path>
  Hooks: <best sample path>

Step 6: Interactive Fallback (if no patterns detected)

If Step 3 found no files OR Step 5 confidence < 50%:

1. Ask user: "No clear patterns detected. Please provide a sample API file path:"
2. Wait for user response
3. Read the provided file
4. Analyze that single file as the pattern source

If user provides no sample:

1. Ask for framework preference
2. Use sensible defaults based on detected framework

ERROR HANDLING

For full error code reference, see [../../docs/ERROR-CODES.md](../../docs/ERROR-CODES.md).

package.json Not Found [E501]

Error: "[E501] ❌ Cannot find package.json"
Cause: Not in project root or no package.json exists
Fix: Run from project root directory
Action: Abort operation

Config File Not Found [E501]

Error: "[E501] ❌ Configuration file not found: .openapi-sync.json"
Cause: Project not initialized
Fix: Run /oas:init to initialize
Action: Abort operation

No Files Match Glob Patterns [E402]

Warning: "[E402] ⚠️ No API files found in standard locations"
Cause: Project uses non-standard structure
Fix: Specify sample file manually
Recovery: Proceed to Interactive Fallback

File Read Error [E302]

Warning: "[E302] ⚠️ Could not read <filepath>, skipping..."
Cause: Permission denied or file corrupted
Recovery: Continue with other files

Invalid Sample File [E402]

Warning: "[E402] ⚠️ Sample file doesn't contain extractable patterns"
Cause: File is empty, too simple, or uses unusual syntax
Fix: Provide a more representative sample
Recovery: Uses default patterns

Conflicting Patterns

Warning: "⚠️ Inconsistent patterns detected across files"
Detail: "Found: camelCase (60%), snake_case (40%)"
Recovery: Use majority pattern, report inconsistency

REFERENCE: Common API Locations

FSD (Feature-Sliced Design):
  src/entities/{domain}/api/{domain}-api.ts
  src/entities/{domain}/model/types.ts
  src/features/{feature}/api/

Feature-based:
  src/features/{feature}/api.ts
  src/features/{feature}/hooks.ts

Flat:
  src/api/{domain}.ts
  src/hooks/use{Domain}.ts

Service-based:
  src/services/{domain}.service.ts
  src/services/{domain}Service.ts

REFERENCE: Detection Patterns

HTTP Client Detection

Data Fetching Detection

Type Pattern Detection

OUTPUT: Pattern Result Structure

Return this structure to the calling command:

{
  "meta": {
    "detectionMethod": "sample-analysis",
    "confidence": 0.85,
    "samplesAnalyzed": 5,
    "framework": "react"
  },
  "structure": {
    "type": "fsd",
    "pattern": "src/entities/{domain}/api/{domain}-api.ts",
    "discovered": ["src/entities/user/api/user-api.ts"]
  },
  "httpClient": {
    "type": "custom-wrapper",
    "import": "import { createApi } from '@/shared/api'",
    "usage": "createApi().{method}<{Type}>(path)"
  },
  "dataFetching": {
    "library": "react-query",
    "version": "5",
    "keyPattern": "factory"
  },
  "types": {
    "location": "src/entities/{domain}/model/types.ts",
    "style": "interface",
    "naming": {
      "request": "{Operation}Request",
      "response": "{Entity}",
      "entity": "{Entity}"
    }
  },
  "samples": {
    "api": { "path": "...", "content": "..." },
    "types": { "path": "...", "content": "..." },
    "hooks": { "path": "...", "content": "..." }
  }
}