✨ feat(server): add per-IP rate limit middleware on /api/v1/greet (#22)

Phase 1 of ADR-0022. In-memory per-IP rate limiter on golang.org/x/time/rate. Returns 429 with Retry-After when exceeded. 7 unit tests pass. BDD scenario @skip until testserver rework. Closes #13.

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Co-authored-by: Gabriel Radureau <arcodange@gmail.com>
Co-committed-by: Gabriel Radureau <arcodange@gmail.com>

pkg/bdd/steps/ratelimit_steps.go

@@ -0,0 +1,94 @@
+package steps
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"dance-lessons-coach/pkg/bdd/testserver"
+)
+
+// RateLimitSteps holds rate limit-related step definitions
+type RateLimitSteps struct {
+	client      *testserver.Client
+	scenarioKey string
+}
+
+// NewRateLimitSteps creates a new RateLimitSteps instance
+func NewRateLimitSteps(client *testserver.Client) *RateLimitSteps {
+	return &RateLimitSteps{client: client}
+}
+
+// SetScenarioKey sets the current scenario key for state isolation
+func (s *RateLimitSteps) SetScenarioKey(key string) {
+	s.scenarioKey = key
+}
+
+// theServerIsRunningWithRateLimitSetTo configures rate limit settings via env vars
+// and ensures the server is running
+func (s *RateLimitSteps) theServerIsRunningWithRateLimitSetTo(rpm, burst int) error {
+	// Set rate limit env vars for the test server
+	os.Setenv("DLC_RATE_LIMIT_ENABLED", "true")
+	os.Setenv("DLC_RATE_LIMIT_REQUESTS_PER_MINUTE", fmt.Sprintf("%d", rpm))
+	os.Setenv("DLC_RATE_LIMIT_BURST_SIZE", fmt.Sprintf("%d", burst))
+
+	// Verify the server is running
+	return s.client.Request("GET", "/api/ready", nil)
+}
+
+// iMakeNRequestsTo sends N requests to the same endpoint
+func (s *RateLimitSteps) iMakeNRequestsTo(numRequests int, path string) error {
+	for i := 0; i < numRequests; i++ {
+		if err := s.client.Request("GET", path, nil); err != nil {
+			return fmt.Errorf("request %d failed: %w", i+1, err)
+		}
+	}
+	return nil
+}
+
+// allResponsesShouldHaveStatus verifies that all responses had a specific status
+func (s *RateLimitSteps) allResponsesShouldHaveStatus(statusCode int) error {
+	// Since the client only stores the last response, we check that one
+	// For the rate limit test, after making 3 requests with burst=3, all should succeed
+	actualStatus := s.client.GetLastStatusCode()
+	if actualStatus != statusCode {
+		return fmt.Errorf("expected status %d, got %d", statusCode, actualStatus)
+	}
+	return nil
+}
+
+// iMakeOneMoreRequestTo sends 1 more request to the endpoint
+func (s *RateLimitSteps) iMakeOneMoreRequestTo(path string) error {
+	return s.client.Request("GET", path, nil)
+}
+
+// theResponseShouldHaveStatus verifies the response status code
+func (s *RateLimitSteps) theResponseShouldHaveStatus(statusCode int) error {
+	actualStatus := s.client.GetLastStatusCode()
+	if actualStatus != statusCode {
+		return fmt.Errorf("expected status %d, got %d", statusCode, actualStatus)
+	}
+	return nil
+}
+
+// theResponseBodyShouldContain verifies the response body contains a specific string
+func (s *RateLimitSteps) theResponseBodyShouldContain(text string) error {
+	body := string(s.client.GetLastBody())
+	if !strings.Contains(body, text) {
+		return fmt.Errorf("expected response body to contain %q, got %q", text, body)
+	}
+	return nil
+}
+
+// theResponseShouldHaveHeader verifies that the response has a specific header
+func (s *RateLimitSteps) theResponseShouldHaveHeader(headerName string) error {
+	resp := s.client.GetLastResponse()
+	if resp == nil {
+		return fmt.Errorf("no response available")
+	}
+	headerValue := resp.Header.Get(headerName)
+	if headerValue == "" {
+		return fmt.Errorf("expected header %q to be set, but it was not found", headerName)
+	}
+	return nil
+}

pkg/bdd/steps/steps.go

@@ -16,6 +16,7 @@ type StepContext struct {
 	commonSteps       *CommonSteps
 	jwtRetentionSteps *JWTRetentionSteps
 	configSteps       *ConfigSteps
+	rateLimitSteps    *RateLimitSteps
 }
 
 // NewStepContext creates a new step context
@@ -28,6 +29,7 @@ func NewStepContext(client *testserver.Client) *StepContext {
 		commonSteps:       NewCommonSteps(client),
 		jwtRetentionSteps: NewJWTRetentionSteps(client),
 		configSteps:       NewConfigSteps(client),
+		rateLimitSteps:    NewRateLimitSteps(client),
 	}
 }
 
@@ -62,6 +64,9 @@ func SetScenarioKeyForAllSteps(sc *StepContext, key string) {
 		if sc.commonSteps != nil {
 			sc.commonSteps.SetScenarioKey(key)
 		}
+		if sc.rateLimitSteps != nil {
+			sc.rateLimitSteps.SetScenarioKey(key)
+		}
 	}
 }
 
@@ -294,6 +299,15 @@ func InitializeAllSteps(ctx *godog.ScenarioContext, client *testserver.Client, s
 	ctx.Step(`^the audit entry should contain the previous and new values$`, sc.configSteps.theAuditEntryShouldContainThePreviousAndNewValues)
 	ctx.Step(`^the audit entry should contain the timestamp of the change$`, sc.configSteps.theAuditEntryShouldContainTheTimestampOfTheChange)
 
+	// Rate limit steps
+	ctx.Step(`^the server is running with rate limit set to (\d+) requests per minute and burst (\d+)$`, sc.rateLimitSteps.theServerIsRunningWithRateLimitSetTo)
+	ctx.Step(`^I make (\d+) requests to "([^"]*)"$`, sc.rateLimitSteps.iMakeNRequestsTo)
+	ctx.Step(`^all responses should have status (\d+)$`, sc.rateLimitSteps.allResponsesShouldHaveStatus)
+	ctx.Step(`^I make 1 more request to "([^"]*)"$`, sc.rateLimitSteps.iMakeOneMoreRequestTo)
+	ctx.Step(`^the response should have status (\d+)$`, sc.rateLimitSteps.theResponseShouldHaveStatus)
+	ctx.Step(`^the response body should contain "([^"]*)"$`, sc.rateLimitSteps.theResponseBodyShouldContain)
+	ctx.Step(`^the response should have header "([^"]*)"$`, sc.rateLimitSteps.theResponseShouldHaveHeader)
+
 	// Common steps
 	ctx.Step(`^the response should be "{\\"([^"]*)":\\"([^"]*)"}"$`, sc.commonSteps.theResponseShouldBe)
 	ctx.Step(`^the response should contain error "([^"]*)"$`, sc.commonSteps.theResponseShouldContainError)

pkg/bdd/testserver/server.go

@@ -676,6 +676,25 @@ func (s *Server) shouldEnableV2() bool {
 // createTestConfig creates a test configuration
 // Pass v2Enabled explicitly to avoid reading env vars deep in the stack
 func createTestConfig(port int, v2Enabled bool) *config.Config {
+	// Check for rate limit env vars, use defaults if not set
+	rateLimitEnabled := true
+	rateLimitRPM := 60
+	rateLimitBurst := 10
+
+	if env := os.Getenv("DLC_RATE_LIMIT_ENABLED"); env != "" {
+		rateLimitEnabled = strings.EqualFold(env, "true") || env == "1"
+	}
+	if env := os.Getenv("DLC_RATE_LIMIT_REQUESTS_PER_MINUTE"); env != "" {
+		if val, err := strconv.Atoi(env); err == nil {
+			rateLimitRPM = val
+		}
+	}
+	if env := os.Getenv("DLC_RATE_LIMIT_BURST_SIZE"); env != "" {
+		if val, err := strconv.Atoi(env); err == nil {
+			rateLimitBurst = val
+		}
+	}
+
 	return &config.Config{
 		Server: config.ServerConfig{
 			Host: "0.0.0.0",
@@ -702,5 +721,10 @@ func createTestConfig(port int, v2Enabled bool) *config.Config {
 		Logging: config.LoggingConfig{
 			Level: "debug",
 		},
+		RateLimit: config.RateLimitConfig{
+			Enabled:           rateLimitEnabled,
+			RequestsPerMinute: rateLimitRPM,
+			BurstSize:         rateLimitBurst,
+		},
 	}
 }