new-go-endpoint

<objective> Automate the complete workflow for adding new API endpoints to the Lexicon Go backend, following API-first development principles. </objective> <workflow> ## Step 1: Gather Requirements

Ask the user for:

1. Endpoint path (e.g., /api/v1/beneficial-ownership/search)
2. HTTP method (GET, POST, PUT, DELETE)
3. Purpose - Brief description of what the endpoint does
4. Request parameters - Query params, path params, or request body
5. Response structure - What data should be returned
6. Caching requirements - Should this endpoint use Redis caching?
7. Database query needed - Does this need a new SQLC query?

Step 2: Update OpenAPI Spec

Edit api/openapi.yaml to add:

• New path and operation
• Request parameters/body schema
• Response schema with all fields
• Proper tags for grouping

Template for new endpoint:

  /api/v1/{resource}:
    get:
      summary: Brief description
      operationId: GetResource
      tags:
        - resource
      parameters:
        - name: param
          in: query
          schema:
            type: string
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ResourceResponse'

Step 3: Generate API Code

Run code generation:

make api-generate

This generates internal/api/api.gen.go with:

• Request/response types
• Server interface with new method signature

Step 4: Create SQLC Query (if needed)

Add query to internal/db/queries/{resource}.sql:

Query patterns from this codebase:

-- Array-based filtering (prevents SQL injection)
-- name: SearchCases :many
SELECT * FROM bo_v1.cases
WHERE (cardinality($1::int[]) = 0 OR subject_type = ANY($1::int[]))
AND (cardinality($2::text[]) = 0 OR LOWER(nation) = ANY($2::text[]))
LIMIT $3 OFFSET $4;

-- Count query for pagination
-- name: CountCases :one
SELECT COUNT(*) FROM bo_v1.cases
WHERE (cardinality($1::int[]) = 0 OR subject_type = ANY($1::int[]));

Then generate:

make sqlc-generate

Step 5: Implement Handler

Add handler in internal/api/handlers.go:

Handler template with caching:

func (s *Server) GetResource(w http.ResponseWriter, r *http.Request) {
    ctx := r.Context()

    // Parse parameters
    params := r.URL.Query()

    // Check cache (if applicable)
    cacheKey := "resource:key"
    if cached, err := s.redis.Get(ctx, cacheKey).Result(); err == nil {
        var result ResourceResponse
        if err := json.Unmarshal([]byte(cached), &result); err == nil {
            respondJSON(w, http.StatusOK, result)
            return
        }
    }

    // Query database
    data, err := s.queries.GetResource(ctx, db.GetResourceParams{...})
    if err != nil {
        respondError(w, http.StatusInternalServerError, "Failed to fetch resource")
        return
    }

    // Map to response
    response := mapToResourceResponse(data)

    // Cache result (5 minute TTL)
    if jsonData, err := json.Marshal(response); err == nil {
        s.redis.Set(ctx, cacheKey, jsonData, 5*time.Minute)
    }

    respondJSON(w, http.StatusOK, response)
}

Handler template without caching:

func (s *Server) GetResource(w http.ResponseWriter, r *http.Request) {
    ctx := r.Context()

    // Parse and validate parameters
    // ...

    // Query database
    data, err := s.queries.GetResource(ctx, params)
    if err != nil {
        respondError(w, http.StatusInternalServerError, "Failed to fetch resource")
        return
    }

    respondJSON(w, http.StatusOK, mapToResponse(data))
}

Step 6: Add Route

Add route in internal/api/routes.go if not auto-registered.

Step 7: Type Mapping Helpers

For SQLC queries with CASE expressions, add helper functions:

// Convert nullable interface{} to string (for CASE expressions)
func convertLabel(label interface{}) string {
    if label == nil {
        return ""
    }
    if str, ok := label.(string); ok {
        return str
    }
    return fmt.Sprintf("%v", label)
}

// Map database int codes to API string enums
func mapSubjectType(code int32) string {
    switch code {
    case 1: return "individual"
    case 2: return "company"
    case 3: return "organization"
    default: return "unknown"
    }
}

Step 8: Test the Endpoint

Run the server and test with curl:

make api-dev
curl -X GET "http://localhost:8080/api/v1/{resource}?param=value" | jq

</workflow>

<validation_patterns>

ULID Validation

var ulidRegex = regexp.MustCompile(`^[0-9A-HJKMNP-TV-Z]{26}$`)

func isValidULID(id string) bool {
    return ulidRegex.MatchString(id)
}

Year Range Validation

const (
    MinYear = 1900
    MaxYear = 2100
    MaxYearSpan = 50
)

func validateYearRange(startYear, endYear int) error {
    if startYear < MinYear || endYear > MaxYear {
        return errors.New("year out of range")
    }
    if endYear - startYear > MaxYearSpan {
        return errors.New("year range too large")
    }
    return nil
}

</validation_patterns>

<cache_keys>

Standard Cache Key Patterns

| Pattern | TTL | Example | |---------|-----|---------| | chart:{type} | 5 min | chart:countries | | lkpp:{type} | 5 min | lkpp:province | | filter:{hash} | 1 min | filter:abc123 | | search:{hash} | 30 sec | search:def456 | </cache_keys>

<success_criteria> Endpoint creation is complete when:

• [ ] OpenAPI spec updated with full schema
• [ ] make api-generate runs without errors
• [ ] SQLC query added (if needed)
• [ ] make sqlc-generate runs without errors
• [ ] Handler implemented with proper error handling
• [ ] Route registered
• [ ] Tested with curl and response documented
• [ ] make check passes (lint + tests) </success_criteria>