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},
	}
}