package probes

import (
	"strings"
	"testing"
)

// TestParseNetDev_RealSample exercises parseNetDev against a synthetic
// /proc/net/dev fixture with the full 16-column layout. Confirms the
// loopback interface is dropped, headers are skipped, and each of the
// six curated counters lands in the right field.
func TestParseNetDev_RealSample(t *testing.T) {
	// Columns after "iface:":
	//   0 rx_bytes  1 rx_packets  2 rx_errs  3 rx_drop
	//   4 fifo  5 frame  6 compressed  7 multicast
	//   8 tx_bytes  9 tx_packets 10 tx_errs 11 tx_drop
	//  12 fifo 13 colls 14 carrier 15 compressed
	fixture := `Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
    lo: 1000000   10000    0    0    0     0          0         0  1000000   10000    0    0    0     0       0          0
  eth0: 50000000  100000   7   12    0     0          0         0  40000000   90000   3    5    0     0       0          0
  eth1: 12345      200     0    0    0     0          0         0    54321     180    0    0    0     0       0          0
`
	snaps := parseNetDev(strings.NewReader(fixture))
	if len(snaps) != 2 {
		t.Fatalf("got %d snapshots, want 2 (lo should be dropped)", len(snaps))
	}
	byIface := map[string]NetDevSnapshot{}
	for _, s := range snaps {
		byIface[s.Iface] = s
	}
	eth0, ok := byIface["eth0"]
	if !ok {
		t.Fatalf("eth0 missing from parsed snapshots")
	}
	if eth0.RxBytes != 50000000 {
		t.Errorf("eth0 RxBytes=%d, want 50000000", eth0.RxBytes)
	}
	if eth0.RxErrs != 7 {
		t.Errorf("eth0 RxErrs=%d, want 7", eth0.RxErrs)
	}
	if eth0.RxDrop != 12 {
		t.Errorf("eth0 RxDrop=%d, want 12", eth0.RxDrop)
	}
	if eth0.TxBytes != 40000000 {
		t.Errorf("eth0 TxBytes=%d, want 40000000", eth0.TxBytes)
	}
	if eth0.TxErrs != 3 {
		t.Errorf("eth0 TxErrs=%d, want 3", eth0.TxErrs)
	}
	if eth0.TxDrop != 5 {
		t.Errorf("eth0 TxDrop=%d, want 5", eth0.TxDrop)
	}
	if _, ok := byIface["lo"]; ok {
		t.Errorf("lo should have been filtered out")
	}
}

// TestParseNetDev_Empty: an empty reader returns no snapshots, not a
// crash. Callers treat nil as "no data" and skip the delta step.
func TestParseNetDev_Empty(t *testing.T) {
	snaps := parseNetDev(strings.NewReader(""))
	if len(snaps) != 0 {
		t.Errorf("got %d snapshots from empty reader, want 0", len(snaps))
	}
}

// TestParseNetDev_MalformedRow skips rows that don't have the expected
// 16 columns rather than panicking. A truncated line shouldn't hide the
// good rows that follow.
func TestParseNetDev_MalformedRow(t *testing.T) {
	fixture := `header line 1
header line 2
  bad0: 123 456
  eth0: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
`
	snaps := parseNetDev(strings.NewReader(fixture))
	if len(snaps) != 1 {
		t.Fatalf("got %d snapshots, want 1 (bad0 should be dropped)", len(snaps))
	}
	if snaps[0].Iface != "eth0" {
		t.Errorf("got iface=%q, want eth0", snaps[0].Iface)
	}
}