From 8fe0f7e6a27cf3efdf56433639f1b24ee8b542f1 Mon Sep 17 00:00:00 2001
From: Joel Wetzell <git@jwetzell.com>
Date: Sun, 24 May 2026 14:19:58 -0500
Subject: [PATCH] add rate limiting filter

---
 internal/processor/filter-rate.go           |  58 ++++++++++
 internal/processor/test/filter-rate_test.go | 116 ++++++++++++++++++++
 2 files changed, 174 insertions(+)
 create mode 100644 internal/processor/filter-rate.go
 create mode 100644 internal/processor/test/filter-rate_test.go

diff --git a/internal/processor/filter-rate.go b/internal/processor/filter-rate.go
new file mode 100644
index 0000000..9e0c6b9
--- /dev/null
+++ b/internal/processor/filter-rate.go
@@ -0,0 +1,58 @@
+package processor
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/google/jsonschema-go/jsonschema"
+	"github.com/jwetzell/showbridge-go/internal/common"
+	"github.com/jwetzell/showbridge-go/internal/config"
+	"golang.org/x/time/rate"
+)
+
+func init() {
+	RegisterProcessor(ProcessorRegistration{
+		Type:  "filter.rate",
+		Title: "Filter by Rate",
+		ParamsSchema: &jsonschema.Schema{
+			Type: "object",
+			Properties: map[string]*jsonschema.Schema{
+				"rate": {
+					Type:        "integer",
+					Title:       "Rate",
+					Description: "The number of events to allow per second.",
+				},
+			},
+			Required: []string{"rate"},
+		},
+		New: func(config config.ProcessorConfig) (Processor, error) {
+			params := config.Params
+			rateInt, err := params.GetInt("rate")
+			if err != nil {
+				return nil, fmt.Errorf("filter.rate rate error: %w", err)
+			}
+
+			limiter := rate.NewLimiter(rate.Limit(rateInt), rateInt*2)
+
+			return &FilterRate{config: config, limiter: limiter}, nil
+		},
+	})
+}
+
+type FilterRate struct {
+	config  config.ProcessorConfig
+	limiter *rate.Limiter
+}
+
+func (fc *FilterRate) Process(ctx context.Context, wrappedPayload common.WrappedPayload) (common.WrappedPayload, error) {
+	err := fc.limiter.Wait(ctx)
+	if err != nil {
+		wrappedPayload.End = true
+		return wrappedPayload, err
+	}
+	return wrappedPayload, nil
+}
+
+func (fc *FilterRate) Type() string {
+	return fc.config.Type
+}
diff --git a/internal/processor/test/filter-rate_test.go b/internal/processor/test/filter-rate_test.go
new file mode 100644
index 0000000..0e28fd0
--- /dev/null
+++ b/internal/processor/test/filter-rate_test.go
@@ -0,0 +1,116 @@
+package processor_test
+
+import (
+	"testing"
+
+	"github.com/jwetzell/showbridge-go/internal/common"
+	"github.com/jwetzell/showbridge-go/internal/config"
+	"github.com/jwetzell/showbridge-go/internal/processor"
+	"github.com/jwetzell/showbridge-go/internal/test"
+)
+
+func TestFilterRateFromRegistry(t *testing.T) {
+	registration, ok := processor.ProcessorRegistry["filter.rate"]
+	if !ok {
+		t.Fatalf("filter.rate processor not registered")
+	}
+
+	processorInstance, err := registration.New(config.ProcessorConfig{
+		Type: "filter.rate",
+		Params: map[string]any{
+			"rate": 1,
+		},
+	})
+	if err != nil {
+		t.Fatalf("failed to create filter.rate processor: %s", err)
+	}
+
+	if processorInstance.Type() != "filter.rate" {
+		t.Fatalf("filter.rate processor has wrong type: %s", processorInstance.Type())
+	}
+}
+
+func TestGoodFilterRate(t *testing.T) {
+	testCases := []struct {
+		name    string
+		params  map[string]any
+		payload any
+		match   bool
+	}{}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			registration, ok := processor.ProcessorRegistry["filter.rate"]
+			if !ok {
+				t.Fatalf("filter.rate processor not registered")
+			}
+
+			processorInstance, err := registration.New(config.ProcessorConfig{
+				Type:   "filter.rate",
+				Params: testCase.params,
+			})
+
+			if err != nil {
+				t.Fatalf("filter.rate failed to create processor: %s", err)
+			}
+
+			_, err = processorInstance.Process(t.Context(), common.WrappedPayload{Payload: testCase.payload})
+			// TODO(jwetzell): figure out how to test the rate limiting behavior
+		})
+	}
+}
+
+func TestBadFilterRate(t *testing.T) {
+	tests := []struct {
+		name        string
+		params      map[string]any
+		payload     any
+		errorString string
+	}{
+		{
+			name:   "no rate parameter",
+			params: map[string]any{
+				// no rate parameter
+			},
+			payload:     test.TestStruct{},
+			errorString: "filter.rate rate error: not found",
+		},
+		{
+			name: "non-int rate parameter",
+			params: map[string]any{
+				"rate": "12345",
+			},
+			payload:     test.TestStruct{},
+			errorString: "filter.rate rate error: not a number",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			registration, ok := processor.ProcessorRegistry["filter.rate"]
+			if !ok {
+				t.Fatalf("filter.rate processor not registered")
+			}
+
+			processorInstance, err := registration.New(config.ProcessorConfig{
+				Type:   "filter.rate",
+				Params: test.params,
+			})
+			if err != nil {
+				if err.Error() != test.errorString {
+					t.Fatalf("filter.rate got error '%s', expected '%s'", err.Error(), test.errorString)
+				}
+				return
+			}
+			got, err := processorInstance.Process(t.Context(), common.WrappedPayload{Payload: test.payload})
+
+			if err == nil {
+				t.Fatalf("filter.rate expected to fail but succeeded, got: %v", got)
+
+			}
+			if err.Error() != test.errorString {
+				t.Fatalf("filter.rate got error '%s', expected '%s'", err.Error(), test.errorString)
+			}
+		})
+	}
+}