Added a dedupe processor, and moved processor packages under processors/*

processors/dedupe/doc.go

@@ -0,0 +1,28 @@
+// Package dedupe provides a default in-memory LRU deduplication processor.
+//
+// The processor keys strictly by event.Event.ID:
+//   - first-seen IDs pass through
+//   - repeated IDs are dropped
+//
+// The in-memory seen-ID set is bounded by a required maxEntries capacity.
+// When capacity is exceeded, the least recently used ID is evicted.
+//
+// Typical registry wiring:
+//
+// ```go
+// reg := processors.NewRegistry()
+// reg.Register("dedupe", dedupe.Factory(10_000))
+//
+//	reg.Register("normalize", func() (processors.Processor, error) {
+//	    return normalize.NewProcessor(myNormalizers, false), nil
+//	})
+//
+// chain, err := reg.BuildChain([]string{"dedupe", "normalize"})
+//
+//	if err != nil {
+//	    // handle wiring error
+//	}
+//
+// p := &pipeline.Pipeline{Processors: chain}
+// ```
+package dedupe

processors/dedupe/processor.go

@@ -0,0 +1,89 @@
+package dedupe
+
+import (
+	"container/list"
+	"context"
+	"fmt"
+	"strings"
+	"sync"
+
+	"gitea.maximumdirect.net/ejr/feedkit/event"
+	"gitea.maximumdirect.net/ejr/feedkit/processors"
+)
+
+// Processor drops duplicate events by Event.ID using an in-memory LRU.
+type Processor struct {
+	maxEntries int
+
+	mu    sync.Mutex
+	order *list.List               // most-recent at front, least-recent at back
+	byID  map[string]*list.Element // id -> list element (element.Value is string id)
+}
+
+var _ processors.Processor = (*Processor)(nil)
+
+// NewProcessor constructs a dedupe processor with a required max entry count.
+func NewProcessor(maxEntries int) (*Processor, error) {
+	if maxEntries <= 0 {
+		return nil, fmt.Errorf("dedupe: maxEntries must be > 0, got %d", maxEntries)
+	}
+
+	return &Processor{
+		maxEntries: maxEntries,
+		order:      list.New(),
+		byID:       make(map[string]*list.Element, maxEntries),
+	}, nil
+}
+
+// Factory returns a processors.Factory that constructs Processor instances.
+func Factory(maxEntries int) processors.Factory {
+	return func() (processors.Processor, error) {
+		return NewProcessor(maxEntries)
+	}
+}
+
+// Process implements processors.Processor.
+func (p *Processor) Process(_ context.Context, in event.Event) (*event.Event, error) {
+	if p == nil {
+		return nil, fmt.Errorf("dedupe: processor is nil")
+	}
+	if p.maxEntries <= 0 {
+		return nil, fmt.Errorf("dedupe: processor maxEntries must be > 0")
+	}
+
+	id := strings.TrimSpace(in.ID)
+	if id == "" {
+		return nil, fmt.Errorf("dedupe: event ID is required")
+	}
+
+	p.mu.Lock()
+
+	if p.order == nil || p.byID == nil {
+		p.mu.Unlock()
+		return nil, fmt.Errorf("dedupe: processor is not initialized")
+	}
+
+	if elem, exists := p.byID[id]; exists {
+		p.order.MoveToFront(elem)
+		p.mu.Unlock()
+		return nil, nil
+	}
+
+	elem := p.order.PushFront(id)
+	p.byID[id] = elem
+
+	if p.order.Len() > p.maxEntries {
+		oldest := p.order.Back()
+		if oldest != nil {
+			p.order.Remove(oldest)
+			if oldestID, ok := oldest.Value.(string); ok {
+				delete(p.byID, oldestID)
+			}
+		}
+	}
+
+	p.mu.Unlock()
+
+	out := in
+	return &out, nil
+}

processors/dedupe/processor_test.go

@@ -0,0 +1,163 @@
+package dedupe
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+
+	"gitea.maximumdirect.net/ejr/feedkit/event"
+	"gitea.maximumdirect.net/ejr/feedkit/processors"
+)
+
+func TestNewProcessorValidation(t *testing.T) {
+	t.Run("rejects non-positive maxEntries", func(t *testing.T) {
+		for _, maxEntries := range []int{0, -1} {
+			p, err := NewProcessor(maxEntries)
+			if err == nil {
+				t.Fatalf("expected error for maxEntries=%d, got nil", maxEntries)
+			}
+			if p != nil {
+				t.Fatalf("expected nil processor for maxEntries=%d", maxEntries)
+			}
+			if !strings.Contains(err.Error(), "maxEntries") {
+				t.Fatalf("unexpected error: %v", err)
+			}
+		}
+	})
+
+	t.Run("accepts positive maxEntries", func(t *testing.T) {
+		p, err := NewProcessor(1)
+		if err != nil {
+			t.Fatalf("NewProcessor error: %v", err)
+		}
+		if p == nil {
+			t.Fatalf("expected processor, got nil")
+		}
+	})
+}
+
+func TestProcessorFirstSeenAndDuplicate(t *testing.T) {
+	p, err := NewProcessor(8)
+	if err != nil {
+		t.Fatalf("NewProcessor error: %v", err)
+	}
+
+	ctx := context.Background()
+	first := testEvent("evt-1")
+
+	out, err := p.Process(ctx, first)
+	if err != nil {
+		t.Fatalf("Process first error: %v", err)
+	}
+	if out == nil {
+		t.Fatalf("expected first event to pass through")
+	}
+	if out.ID != first.ID {
+		t.Fatalf("expected unchanged ID %q, got %q", first.ID, out.ID)
+	}
+
+	out, err = p.Process(ctx, first)
+	if err != nil {
+		t.Fatalf("Process duplicate error: %v", err)
+	}
+	if out != nil {
+		t.Fatalf("expected duplicate to be dropped, got %#v", out)
+	}
+
+	out, err = p.Process(ctx, testEvent("evt-2"))
+	if err != nil {
+		t.Fatalf("Process second unique error: %v", err)
+	}
+	if out == nil {
+		t.Fatalf("expected second unique event to pass through")
+	}
+}
+
+func TestProcessorLRUEvictionAndPromotion(t *testing.T) {
+	p, err := NewProcessor(2)
+	if err != nil {
+		t.Fatalf("NewProcessor error: %v", err)
+	}
+
+	ctx := context.Background()
+
+	mustPass(t, p, ctx, "a")
+	mustPass(t, p, ctx, "b")
+	mustDrop(t, p, ctx, "a") // promote "a" so "b" becomes least-recently-used
+	mustPass(t, p, ctx, "c") // evicts "b"
+	mustDrop(t, p, ctx, "a") // "a" should still be tracked after promotion
+	mustPass(t, p, ctx, "b") // "b" was evicted, so now it passes again
+}
+
+func TestProcessorRejectsBlankID(t *testing.T) {
+	p, err := NewProcessor(4)
+	if err != nil {
+		t.Fatalf("NewProcessor error: %v", err)
+	}
+
+	in := testEvent("   ")
+	out, err := p.Process(context.Background(), in)
+	if err == nil {
+		t.Fatalf("expected error for blank ID")
+	}
+	if out != nil {
+		t.Fatalf("expected nil output on error, got %#v", out)
+	}
+	if !strings.Contains(err.Error(), "event ID is required") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestFactoryWithRegistry(t *testing.T) {
+	r := processors.NewRegistry()
+	r.Register("dedupe", Factory(3))
+
+	p, err := r.Build("dedupe")
+	if err != nil {
+		t.Fatalf("Build error: %v", err)
+	}
+	if p == nil {
+		t.Fatalf("expected processor, got nil")
+	}
+
+	out, err := p.Process(context.Background(), testEvent("evt-factory-1"))
+	if err != nil {
+		t.Fatalf("Process error: %v", err)
+	}
+	if out == nil {
+		t.Fatalf("expected first event to pass through")
+	}
+}
+
+func mustPass(t *testing.T, p *Processor, ctx context.Context, id string) {
+	t.Helper()
+	out, err := p.Process(ctx, testEvent(id))
+	if err != nil {
+		t.Fatalf("expected pass for id=%q, got error: %v", id, err)
+	}
+	if out == nil {
+		t.Fatalf("expected pass for id=%q, got drop", id)
+	}
+}
+
+func mustDrop(t *testing.T, p *Processor, ctx context.Context, id string) {
+	t.Helper()
+	out, err := p.Process(ctx, testEvent(id))
+	if err != nil {
+		t.Fatalf("expected drop for id=%q, got error: %v", id, err)
+	}
+	if out != nil {
+		t.Fatalf("expected drop for id=%q, got output", id)
+	}
+}
+
+func testEvent(id string) event.Event {
+	return event.Event{
+		ID:        id,
+		Kind:      event.Kind("observation"),
+		Source:    "source-1",
+		EmittedAt: time.Now().UTC(),
+		Payload:   map[string]any{"ok": true},
+	}
+}