package via

import (
	"errors"
	"strings"
	"testing"
)

// probeQueue scripts one answer per channel the probe visits, so a test can say
// which channels the keyboard has.
func probeQueue(present ...Channel) [][]byte {
	queue := make([][]byte, 0, probeChannelMax)
	for c := 1; c <= probeChannelMax; c++ {
		buf := make([]byte, 32)
		if containsChannel(present, Channel(c)) {
			buf[0] = byte(CustomGet)
			buf[3] = 160
		} else {
			buf[0] = byte(Unhandled)
		}
		buf[1] = byte(c)
		buf[2] = probeValueID
		queue = append(queue, buf)
	}
	return queue
}

func containsChannel(channels []Channel, want Channel) bool {
	for _, c := range channels {
		if c == want {
			return true
		}
	}
	return false
}

func TestDetectChannelsFindsTheAnsweredChannels(t *testing.T) {
	transport := &fakeTransport{queue: probeQueue(ChannelRgblight, ChannelRgbMatrix, ChannelAudio)}
	protocol := Protocol{handle: transport}

	got, err := protocol.DetectChannels()
	if err != nil {
		t.Fatalf("DetectChannels() error = %v", err)
	}

	want := []Channel{ChannelRgblight, ChannelRgbMatrix, ChannelAudio}
	if len(got) != len(want) {
		t.Fatalf("DetectChannels() = %v, want %v", got, want)
	}
	for i := range want {
		if got[i] != want[i] {
			t.Errorf("DetectChannels()[%d] = %d, want %d", i, got[i], want[i])
		}
	}
}

func TestDetectChannelsAsksBrightnessOnEveryChannelFromOneToFifteen(t *testing.T) {
	transport := &fakeTransport{queue: probeQueue()}
	protocol := Protocol{handle: transport}

	if _, err := protocol.DetectChannels(); err != nil {
		t.Fatalf("DetectChannels() error = %v", err)
	}

	if len(transport.reports) != probeChannelMax {
		t.Fatalf("requests = %d, want %d", len(transport.reports), probeChannelMax)
	}
	for i, report := range transport.reports {
		wantChannel := byte(i + 1)
		if report[0] != byte(CustomGet) {
			t.Errorf("request %d command = 0x%02x, want 0x%02x", i, report[0], CustomGet)
		}
		if report[1] != wantChannel {
			t.Errorf("request %d channel = %d, want %d", i, report[1], wantChannel)
		}
		if report[2] != probeValueID {
			t.Errorf("request %d value = 0x%02x, want 0x%02x (brightness)", i, report[2], probeValueID)
		}
	}
}

// A channel list missing entries is indistinguishable from a complete one, so a
// transport failure has to abort the probe instead of shrinking it.
func TestDetectChannelsFailsOnATransportErrorMidProbe(t *testing.T) {
	transport := &fakeTransport{
		queue:        probeQueue(ChannelRgblight, ChannelRgbMatrix, ChannelAudio),
		readErr:      errors.New("read: interrupted system call"),
		readErrAfter: 3,
	}
	protocol := Protocol{handle: transport}

	_, err := protocol.DetectChannels()
	if err == nil {
		t.Fatal("DetectChannels() expected an error, got nil")
	}
	if !strings.Contains(err.Error(), "channel 4") {
		t.Errorf("error = %q, want it to name the channel that failed", err)
	}
}

// A 0xFF that matches nothing is a valid "no such channel". Only a 0xFF whose
// echoed channel disagrees is a desynchronised stream.
func TestDetectChannelsAcceptsAWellFormedUnhandledAnswer(t *testing.T) {
	transport := &fakeTransport{queue: probeQueue(ChannelRgblight)}
	protocol := Protocol{handle: transport}

	got, err := protocol.DetectChannels()
	if err != nil {
		t.Fatalf("DetectChannels() error = %v", err)
	}
	if len(got) != 1 || got[0] != ChannelRgblight {
		t.Errorf("DetectChannels() = %v, want [2]", got)
	}
}

func TestDetectChannelsReportsNoChannelsWhenNoneArePresent(t *testing.T) {
	transport := &fakeTransport{queue: probeQueue()}
	protocol := Protocol{handle: transport}

	got, err := protocol.DetectChannels()
	if err != nil {
		t.Fatalf("DetectChannels() error = %v", err)
	}
	if len(got) != 0 {
		t.Errorf("DetectChannels() = %v, want empty", got)
	}
}

// effectResponse is one scripted answer to an effect get or set, carrying the
// value the keyboard is left with.
func effectResponse(command Message, ch Channel, value byte) []byte {
	buf := make([]byte, 32)
	buf[0] = byte(command)
	buf[1] = byte(ch)
	buf[2] = effectValueID
	buf[3] = value
	return buf
}

// QMK clamps rather than rejects: a mode at or above the top comes down to it.
// A single write above the top therefore returns the top itself, which is the
// whole reason the probe is one round trip instead of a search.
func TestEffectTopReadsTheTopOffWhatTheFirmwareClampedTo(t *testing.T) {
	const ch = ChannelRgbMatrix
	transport := &fakeTransport{queue: [][]byte{
		effectResponse(CustomGet, ch, 12),  // the effect the channel is on
		effectResponse(CustomSet, ch, 255), // the probe, echoed
		effectResponse(CustomGet, ch, 45),  // what the clamp left
		effectResponse(CustomSet, ch, 12),  // the restore, echoed
	}}
	protocol := Protocol{handle: transport}

	got, err := protocol.EffectTop(ch)
	if err != nil {
		t.Fatalf("EffectTop() error = %v", err)
	}
	if got != 45 {
		t.Errorf("EffectTop() = %d, want 45", got)
	}
	if len(transport.reports) != 4 {
		t.Fatalf("requests = %d, want 4 (read, probe, read back, restore)", len(transport.reports))
	}
	last := transport.reports[3]
	if last[0] != byte(CustomSet) || last[3] != 12 {
		t.Errorf("last request = %v, want the original effect 12 written back", last[:4])
	}
}

// A channel already sitting on its last effect answers the probe with the value
// it held, which is the same number the clamp would give. The two cases need not
// be told apart, so the answer is still the top.
func TestEffectTopReportsTheTopWhenTheChannelAlreadySatOnIt(t *testing.T) {
	const ch = ChannelRgbMatrix
	transport := &fakeTransport{queue: [][]byte{
		effectResponse(CustomGet, ch, 45),
		effectResponse(CustomSet, ch, 255),
		effectResponse(CustomGet, ch, 45),
		effectResponse(CustomSet, ch, 45),
	}}
	protocol := Protocol{handle: transport}

	got, err := protocol.EffectTop(ch)
	if err != nil {
		t.Fatalf("EffectTop() error = %v", err)
	}
	if got != 45 {
		t.Errorf("EffectTop() = %d, want 45", got)
	}
}

// VIA reads a 0 on the effect parameter as "turn this channel off", so the probe
// must not write one. The restore may: a channel that was on effect 0 goes back
// to 0, which is the state it was in.
func TestEffectTopProbesWithoutSwitchingTheChannelOff(t *testing.T) {
	if effectProbeValue == 0 {
		t.Fatal("effectProbeValue is 0, which switches the channel off instead of asking")
	}

	const ch = ChannelRgbMatrix
	transport := &fakeTransport{queue: [][]byte{
		effectResponse(CustomGet, ch, 0),
		effectResponse(CustomSet, ch, effectProbeValue),
		effectResponse(CustomGet, ch, 6),
		effectResponse(CustomSet, ch, 0),
	}}
	protocol := Protocol{handle: transport}

	if _, err := protocol.EffectTop(ch); err != nil {
		t.Fatalf("EffectTop() error = %v", err)
	}

	probe := transport.reports[1]
	if probe[0] != byte(CustomSet) || probe[2] != effectValueID {
		t.Fatalf("request 1 = %v, want a set on the effect parameter", probe[:4])
	}
	if probe[3] != effectProbeValue {
		t.Errorf("probe wrote effect %d, want %d", probe[3], effectProbeValue)
	}
}

// An effect that cannot be read is a channel the probe cannot restore, so it
// stops before it writes rather than leaving the channel on the last effect.
func TestEffectTopStopsBeforeWritingWhenTheEffectCannotBeRead(t *testing.T) {
	const ch = ChannelRgbMatrix
	transport := &fakeTransport{queue: [][]byte{effectResponse(Unhandled, ch, 0)}}
	protocol := Protocol{handle: transport}

	if _, err := protocol.EffectTop(ch); err == nil {
		t.Fatal("EffectTop() = nil error, want a failure for an effect that cannot be read")
	}
	if len(transport.reports) != 1 {
		t.Errorf("requests = %d, want only the read that failed", len(transport.reports))
	}
}

func TestChannelSubsystemNames(t *testing.T) {
	tests := []struct {
		channel Channel
		want    string
	}{
		{ChannelBacklight, "backlight"},
		{ChannelRgblight, "rgblight"},
		{ChannelRgbMatrix, "rgb_matrix"},
		{ChannelAudio, "audio"},
		{ChannelLedMatrix, "led_matrix"},
		{Channel(9), ""},
	}

	for _, tt := range tests {
		if got := tt.channel.Subsystem(); got != tt.want {
			t.Errorf("Channel(%d).Subsystem() = %q, want %q", tt.channel, got, tt.want)
		}
	}
}

// A stale 0xFF — the answer to an earlier request, still in the read buffer —
// looks exactly like absence. Reading the channel out of it is what tells the
// two apart, and a mismatch means the request/response stream is out of step.
func TestDetectChannelsRejectsAnUnhandledAnswerForAnotherChannel(t *testing.T) {
	queue := probeQueue(ChannelRgblight, ChannelRgbMatrix, ChannelAudio)
	// Channel 2 answers "unhandled", but for a different channel: the stream
	// is answering a request that is not this one.
	stale := make([]byte, 32)
	stale[0] = byte(Unhandled)
	stale[1] = 0x07
	stale[2] = probeValueID
	queue[1] = stale

	transport := &fakeTransport{queue: queue}
	protocol := Protocol{handle: transport}

	_, err := protocol.DetectChannels()
	if err == nil {
		t.Fatal("DetectChannels() expected an error for an answer belonging to another channel")
	}
	if !strings.Contains(err.Error(), "channel 2") {
		t.Errorf("error = %q, want it to name the channel whose answer did not match", err)
	}
}