// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

package sockstatlog

import (
	"testing"

	"github.com/google/go-cmp/cmp"
	"tailscale.com/net/sockstats"
)

func TestDelta(t *testing.T) {
	tests := []struct {
		name      string
		a, b      *sockstats.SockStats
		wantStats map[sockstats.Label]deltaStat
	}{
		{
			name:      "nil a stat",
			a:         nil,
			b:         &sockstats.SockStats{},
			wantStats: nil,
		},
		{
			name:      "nil b stat",
			a:         &sockstats.SockStats{},
			b:         nil,
			wantStats: nil,
		},
		{
			name: "no change",
			a: &sockstats.SockStats{
				Stats: map[sockstats.Label]sockstats.SockStat{
					sockstats.LabelDERPHTTPClient: {
						TxBytes: 10,
						TxBytesByInterface: map[string]uint64{
							"en0": 10,
						},
					},
				},
			},
			b: &sockstats.SockStats{
				Stats: map[sockstats.Label]sockstats.SockStat{
					sockstats.LabelDERPHTTPClient: {
						TxBytes: 10,
						TxBytesByInterface: map[string]uint64{
							"en0": 10,
						},
					},
				},
			},
			wantStats: nil,
		},
		{
			name: "tx after empty stat",
			a:    &sockstats.SockStats{},
			b: &sockstats.SockStats{
				Stats: map[sockstats.Label]sockstats.SockStat{
					sockstats.LabelDERPHTTPClient: {
						TxBytes: 10,
						TxBytesByInterface: map[string]uint64{
							"en0": 10,
						},
					},
				},
				Interfaces: []string{"en0"},
			},
			wantStats: map[sockstats.Label]deltaStat{
				sockstats.LabelDERPHTTPClient: {10, 0},
			},
		},
		{
			name: "rx after non-empty stat",
			a: &sockstats.SockStats{
				Stats: map[sockstats.Label]sockstats.SockStat{
					sockstats.LabelDERPHTTPClient: {
						TxBytes: 10,
						RxBytes: 10,
						TxBytesByInterface: map[string]uint64{
							"en0": 10,
						},
						RxBytesByInterface: map[string]uint64{
							"en0": 10,
						},
					},
				},
				Interfaces: []string{"en0"},
			},
			b: &sockstats.SockStats{
				Stats: map[sockstats.Label]sockstats.SockStat{
					sockstats.LabelDERPHTTPClient: {
						TxBytes: 10,
						RxBytes: 30,
						TxBytesByInterface: map[string]uint64{
							"en0": 10,
						},
						RxBytesByInterface: map[string]uint64{
							"en0": 30,
						},
					},
				},
				Interfaces: []string{"en0"},
			},
			wantStats: map[sockstats.Label]deltaStat{
				sockstats.LabelDERPHTTPClient: {0, 20},
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			gotStats := delta(tt.a, tt.b)
			if !cmp.Equal(gotStats, tt.wantStats) {
				t.Errorf("gotStats = %v, want %v", gotStats, tt.wantStats)
			}
		})
	}
}