package mesh

import (
	"errors"
	"testing"
)

func TestSyntheticRelaySchedulerDequeuesByQoSPriority(t *testing.T) {
	scheduler := testRelayScheduler()
	telemetry := testRelayEnvelope(SyntheticChannelTelemetry, SyntheticMessageTelemetry, 1)
	routeControl := testRelayEnvelope(SyntheticChannelRouteControl, SyntheticMessageRouteHealth, 2)
	fabricControl := testRelayEnvelope(SyntheticChannelFabricControl, SyntheticMessageProbe, 3)

	if _, err := scheduler.Enqueue(telemetry); err != nil {
		t.Fatalf("enqueue telemetry: %v", err)
	}
	if _, err := scheduler.Enqueue(routeControl); err != nil {
		t.Fatalf("enqueue route control: %v", err)
	}
	if _, err := scheduler.Enqueue(fabricControl); err != nil {
		t.Fatalf("enqueue fabric control: %v", err)
	}

	first, err := scheduler.Dequeue()
	if err != nil {
		t.Fatalf("dequeue first: %v", err)
	}
	second, err := scheduler.Dequeue()
	if err != nil {
		t.Fatalf("dequeue second: %v", err)
	}
	third, err := scheduler.Dequeue()
	if err != nil {
		t.Fatalf("dequeue third: %v", err)
	}
	if first.Channel != SyntheticChannelFabricControl {
		t.Fatalf("first channel = %q, want fabric_control", first.Channel)
	}
	if second.Channel != SyntheticChannelRouteControl {
		t.Fatalf("second channel = %q, want route_control", second.Channel)
	}
	if third.Channel != SyntheticChannelTelemetry {
		t.Fatalf("third channel = %q, want telemetry", third.Channel)
	}
}

func TestSyntheticRelaySchedulerDropsOldestTelemetryOnly(t *testing.T) {
	scheduler := testRelayScheduler()
	first := testRelayEnvelope(SyntheticChannelTelemetry, SyntheticMessageTelemetry, 1)
	second := testRelayEnvelope(SyntheticChannelTelemetry, SyntheticMessageTelemetry, 2)

	if result, err := scheduler.Enqueue(first); err != nil || result.Dropped {
		t.Fatalf("enqueue first result=%+v err=%v", result, err)
	}
	result, err := scheduler.Enqueue(second)
	if err != nil {
		t.Fatalf("enqueue second: %v", err)
	}
	if !result.Dropped || result.DroppedSequence != 1 {
		t.Fatalf("result = %+v, want dropped sequence 1", result)
	}
	dequeued, err := scheduler.Dequeue()
	if err != nil {
		t.Fatalf("dequeue: %v", err)
	}
	if dequeued.Sequence != 2 {
		t.Fatalf("dequeued sequence = %d, want 2", dequeued.Sequence)
	}
	metrics := scheduler.SnapshotQueueMetrics()
	if metrics.Dropped != 1 || metrics.Enqueued != 2 {
		t.Fatalf("metrics = %+v, want one drop and two enqueues", metrics)
	}
}

func TestSyntheticRelaySchedulerRejectsFullReliableQueue(t *testing.T) {
	scheduler := testRelayScheduler()
	first := testRelayEnvelope(SyntheticChannelFabricControl, SyntheticMessageProbe, 1)
	second := testRelayEnvelope(SyntheticChannelFabricControl, SyntheticMessageProbe, 2)

	if _, err := scheduler.Enqueue(first); err != nil {
		t.Fatalf("enqueue first: %v", err)
	}
	_, err := scheduler.Enqueue(second)
	if !errors.Is(err, ErrSyntheticRelayQueueFull) {
		t.Fatalf("err = %v, want ErrSyntheticRelayQueueFull", err)
	}
	dequeued, err := scheduler.Dequeue()
	if err != nil {
		t.Fatalf("dequeue: %v", err)
	}
	if dequeued.Sequence != 1 {
		t.Fatalf("dequeued sequence = %d, want 1", dequeued.Sequence)
	}
	metrics := scheduler.SnapshotQueueMetrics()
	if metrics.Dropped != 0 || metrics.Rejected != 1 {
		t.Fatalf("metrics = %+v, want no drop and one rejection", metrics)
	}
}

func TestSyntheticRelaySchedulerRejectsInvalidEnvelopes(t *testing.T) {
	tests := []struct {
		name   string
		mutate func(*SyntheticEnvelope)
		want   error
	}{
		{
			name: "wrong cluster",
			mutate: func(envelope *SyntheticEnvelope) {
				envelope.ClusterID = "cluster-2"
			},
			want: ErrClusterMismatch,
		},
		{
			name: "wrong node",
			mutate: func(envelope *SyntheticEnvelope) {
				envelope.To.NodeID = "node-x"
			},
			want: ErrNodeMismatch,
		},
		{
			name: "unauthorized channel",
			mutate: func(envelope *SyntheticEnvelope) {
				envelope.Channel = "rdp_render"
			},
			want: ErrUnauthorizedChannel,
		},
		{
			name: "unsupported message",
			mutate: func(envelope *SyntheticEnvelope) {
				envelope.MessageType = "rdp.input"
			},
			want: ErrUnsupportedSyntheticMessage,
		},
		{
			name: "ttl exhausted",
			mutate: func(envelope *SyntheticEnvelope) {
				envelope.TTL = 0
			},
			want: ErrTTLExhausted,
		},
		{
			name: "loop detected",
			mutate: func(envelope *SyntheticEnvelope) {
				envelope.Visited = append(envelope.Visited, "node-r")
			},
			want: ErrLoopDetected,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			scheduler := testRelayScheduler()
			envelope := testRelayEnvelope(SyntheticChannelFabricControl, SyntheticMessageProbe, 1)
			tt.mutate(&envelope)
			_, err := scheduler.Enqueue(envelope)
			if !errors.Is(err, tt.want) {
				t.Fatalf("err = %v, want %v", err, tt.want)
			}
		})
	}
}

func TestSyntheticRelaySchedulerDisabledRejects(t *testing.T) {
	scheduler := NewSyntheticRelayScheduler(SyntheticRelaySchedulerConfig{
		Enabled: false,
		Local:   PeerIdentity{ClusterID: "cluster-1", NodeID: "node-r"},
	})
	_, err := scheduler.Enqueue(testRelayEnvelope(SyntheticChannelFabricControl, SyntheticMessageProbe, 1))
	if !errors.Is(err, ErrMeshRuntimeDisabled) {
		t.Fatalf("err = %v, want ErrMeshRuntimeDisabled", err)
	}
	if _, err := scheduler.Dequeue(); !errors.Is(err, ErrMeshRuntimeDisabled) {
		t.Fatalf("dequeue err = %v, want ErrMeshRuntimeDisabled", err)
	}
}

func TestSyntheticRelaySchedulerQueueDepthSnapshot(t *testing.T) {
	scheduler := testRelayScheduler()
	if _, err := scheduler.Enqueue(testRelayEnvelope(SyntheticChannelFabricControl, SyntheticMessageProbe, 1)); err != nil {
		t.Fatalf("enqueue fabric control: %v", err)
	}
	if _, err := scheduler.Enqueue(testRelayEnvelope(SyntheticChannelRouteControl, SyntheticMessageRouteHealth, 2)); err != nil {
		t.Fatalf("enqueue route control: %v", err)
	}
	metrics := scheduler.SnapshotQueueMetrics()
	if metrics.QueueDepths[SyntheticChannelFabricControl] != 1 {
		t.Fatalf("fabric_control depth = %d, want 1", metrics.QueueDepths[SyntheticChannelFabricControl])
	}
	if metrics.QueueDepths[SyntheticChannelRouteControl] != 1 {
		t.Fatalf("route_control depth = %d, want 1", metrics.QueueDepths[SyntheticChannelRouteControl])
	}
}

func testRelayScheduler() *SyntheticRelayScheduler {
	return NewSyntheticRelayScheduler(SyntheticRelaySchedulerConfig{
		Enabled: true,
		Local:   PeerIdentity{ClusterID: "cluster-1", NodeID: "node-r"},
		QueuePolicies: []SyntheticRelayQueuePolicy{
			{Channel: SyntheticChannelFabricControl, Capacity: 1, Droppable: false},
			{Channel: SyntheticChannelRouteControl, Capacity: 1, Droppable: false},
			{Channel: SyntheticChannelTelemetry, Capacity: 1, Droppable: true},
		},
	})
}

func testRelayEnvelope(channel string, messageType string, sequence uint64) SyntheticEnvelope {
	route := testRoute("route-relay-scheduler", []string{"node-a", "node-r", "node-b"})
	envelope := testEnvelope(route, "node-a", "node-r")
	envelope.Channel = channel
	envelope.MessageType = messageType
	envelope.Sequence = sequence
	return envelope
}