package dispenser

import (
	"bytes"
	"context"
	"errors"
	"strings"
	"testing"
	"time"

	log "github.com/sirupsen/logrus"
)

type fakeSequenceDevice struct {
	statusResponses []cmdResp
	commandErrors   map[cmdType][]error
	commands        []cmdType
}

func newSequenceTestClient(t *testing.T, statusResponses ...cmdResp) (*Client, *fakeSequenceDevice) {
	t.Helper()

	device := &fakeSequenceDevice{
		statusResponses: append([]cmdResp(nil), statusResponses...),
		commandErrors:   make(map[cmdType][]error),
	}
	now := time.Date(2026, time.July, 23, 12, 0, 0, 0, time.UTC)
	client := &Client{
		reqCh: make(chan cmdReq),
		done:  make(chan struct{}),
		sequenceTiming: sequenceTiming{
			now: func() time.Time {
				return now
			},
			wait: func(ctx context.Context, duration time.Duration) error {
				select {
				case <-ctx.Done():
					return ctx.Err()
				default:
					now = now.Add(duration)
					return nil
				}
			},
		},
	}

	go func() {
		for {
			select {
			case <-client.done:
				return
			case request := <-client.reqCh:
				device.commands = append(device.commands, request.typ)
				if request.typ == cmdStatus {
					if len(device.statusResponses) == 0 {
						request.respCh <- cmdResp{err: errors.New("unexpected status read")}
						continue
					}
					response := device.statusResponses[0]
					device.statusResponses = device.statusResponses[1:]
					request.respCh <- response
					continue
				}

				var err error
				if queued := device.commandErrors[request.typ]; len(queued) > 0 {
					err = queued[0]
					device.commandErrors[request.typ] = queued[1:]
				}
				request.respCh <- cmdResp{err: err}
			}
		}
	}()
	t.Cleanup(client.Close)

	return client, device
}

func status(position byte) []byte {
	return []byte{0x30, 0x30, 0x30, position}
}

func commandCount(commands []cmdType, target cmdType) int {
	count := 0
	for _, command := range commands {
		if command == target {
			count++
		}
	}
	return count
}

func TestPrepareCurrentCardAcceptsEncoderPositionWithStaleDiagnostics(t *testing.T) {
	tests := []struct {
		name      string
		status    []byte
		wantStock string
	}{
		{
			name:      "dispense error and jam",
			status:    []byte{0x30, 0x32, 0x32, 0x33},
			wantStock: "Card jammed",
		},
		{
			name:      "supply diagnostics",
			status:    []byte{0x32, 0x30, 0x31, 0x33},
			wantStock: "Card pre-empty",
		},
		{
			name:   "combined stale jam and supply diagnostics",
			status: []byte{0x30, 0x32, 0x33, 0x33},
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			var logOutput bytes.Buffer
			standardLogger := log.StandardLogger()
			previousOutput := standardLogger.Out
			standardLogger.SetOutput(&logOutput)
			t.Cleanup(func() {
				standardLogger.SetOutput(previousOutput)
			})

			client, device := newSequenceTestClient(t, cmdResp{status: test.status})

			stock, err := client.PrepareCurrentCard(context.Background())
			if err != nil {
				t.Fatal(err)
			}
			if stock != test.wantStock {
				t.Fatalf("stock status = %q, want %q", stock, test.wantStock)
			}
			if got := commandCount(device.commands, cmdToEncoder); got != 0 {
				t.Fatalf("to-encoder commands = %d, want 0", got)
			}
			if got := commandCount(device.commands, cmdStatus); got != 1 {
				t.Fatalf("status reads = %d, want 1", got)
			}
			logged := logOutput.String()
			if !strings.Contains(logged, "card confirmed at encoder") ||
				!strings.Contains(logged, statusDescription(test.status)) ||
				!strings.Contains(logged, "raw status") {
				t.Fatalf("encoder diagnostic log = %q", logged)
			}
		})
	}
}

func TestPrepareCurrentCardPollingAllowsTransientMovementWithStaleErrors(t *testing.T) {
	client, device := newSequenceTestClient(t,
		cmdResp{status: status(0x34)},
		cmdResp{status: []byte{0x31, 0x38, 0x32, 0x30}},
		cmdResp{status: []byte{0x30, 0x32, 0x32, 0x33}},
	)

	stock, err := client.PrepareCurrentCard(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if stock != "Card jammed" {
		t.Fatalf("stock status = %q, want Card jammed", stock)
	}
	if got := commandCount(device.commands, cmdToEncoder); got != 1 {
		t.Fatalf("to-encoder commands = %d, want 1", got)
	}
	if got := commandCount(device.commands, cmdStatus); got != 3 {
		t.Fatalf("status reads = %d, want 3", got)
	}
}

func TestPrepareCurrentCardRejectsFailureWithoutEncoderOrMovement(t *testing.T) {
	tests := []struct {
		name      string
		response  cmdResp
		wantError string
		wantStock string
	}{
		{
			name:      "status read error",
			response:  cmdResp{err: errors.New("serial read failed")},
			wantError: "serial read failed",
		},
		{
			name:      "malformed status",
			response:  cmdResp{status: []byte{0x30, 0x30, 0x31}},
			wantError: "malformed dispenser status",
		},
		{
			name:      "unknown status",
			response:  cmdResp{status: []byte{0x30, 0x30, 0x30, 0x39}},
			wantError: "unknown dispenser status",
		},
		{
			name:      "jammed preparation",
			response:  cmdResp{status: []byte{0x30, 0x30, 0x32, 0x34}},
			wantError: "Card jammed",
			wantStock: "Card jammed",
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			client, _ := newSequenceTestClient(t, test.response)

			stock, err := client.PrepareCurrentCard(context.Background())
			if err == nil || !strings.Contains(err.Error(), test.wantError) {
				t.Fatalf("error = %v, want containing %q", err, test.wantError)
			}
			if stock != test.wantStock {
				t.Fatalf("stock status = %q, want %q", stock, test.wantStock)
			}
		})
	}
}

func TestPrepareCurrentCardReturnsAuthoritativeEmptyWellError(t *testing.T) {
	client, device := newSequenceTestClient(t, cmdResp{status: status(0x38)})

	stock, err := client.PrepareCurrentCard(context.Background())
	if !errors.Is(err, ErrCardWellEmpty) {
		t.Fatalf("error = %v, want ErrCardWellEmpty", err)
	}
	if stock != "Card empty" {
		t.Fatalf("stock status = %q, want Card empty", stock)
	}
	if got := commandCount(device.commands, cmdToEncoder); got != 0 {
		t.Fatalf("to-encoder commands = %d, want 0", got)
	}
}

func TestDeliverCurrentCardSucceedsAfterCommandAcceptanceWithoutStatusPolling(t *testing.T) {
	staleStatus := []byte{0x30, 0x32, 0x32, 0x33}
	client, device := newSequenceTestClient(t, cmdResp{status: staleStatus})

	stock, err := client.DeliverCurrentCard(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if stock != "" {
		t.Fatalf("stock status = %q, want empty", stock)
	}
	if got := commandCount(device.commands, cmdOutOfMouth); got != 1 {
		t.Fatalf("out-of-mouth commands = %d, want 1", got)
	}
	if got := commandCount(device.commands, cmdStatus); got != 0 {
		t.Fatalf("status reads = %d, want 0", got)
	}
	if len(device.statusResponses) != 1 {
		t.Fatalf("queued status responses = %d, want stale status unread", len(device.statusResponses))
	}
}

func TestDeliverCurrentCardRejectsCommandFailures(t *testing.T) {
	tests := []struct {
		name string
		err  error
	}{
		{name: "serial dispatch failure", err: errors.New("serial write failed")},
		{name: "invalid acknowledgement", err: errors.New("unexpected response status")},
		{name: "missing acknowledgement", err: errors.New("no response from dispenser")},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			client, device := newSequenceTestClient(t)
			device.commandErrors[cmdOutOfMouth] = []error{test.err}

			_, err := client.DeliverCurrentCard(context.Background())
			if err == nil || !strings.Contains(err.Error(), test.err.Error()) {
				t.Fatalf("error = %v, want containing %q", err, test.err)
			}
			if got := commandCount(device.commands, cmdOutOfMouth); got != 1 {
				t.Fatalf("out-of-mouth commands = %d, want 1", got)
			}
			if got := commandCount(device.commands, cmdStatus); got != 0 {
				t.Fatalf("status reads = %d, want 0", got)
			}
		})
	}
}

func TestDeliverCurrentCardPreservesContextCancellation(t *testing.T) {
	client, _ := newSequenceTestClient(t)
	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	_, err := client.DeliverCurrentCard(ctx)
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("error = %v, want context.Canceled", err)
	}
}

func TestPrepareCurrentCardRetriesOnceThenTimesOut(t *testing.T) {
	responses := make([]cmdResp, 13)
	for index := range responses {
		responses[index] = cmdResp{status: status(0x34)}
	}
	client, device := newSequenceTestClient(t, responses...)

	_, err := client.PrepareCurrentCard(context.Background())
	if err == nil || !strings.Contains(err.Error(), "timed out") {
		t.Fatalf("error = %v, want preparation timeout", err)
	}
	if got := commandCount(device.commands, cmdToEncoder); got != 2 {
		t.Fatalf("to-encoder commands = %d, want initial command plus one halfway retry", got)
	}
	if got := commandCount(device.commands, cmdStatus); got != 13 {
		t.Fatalf("status reads = %d, want 13", got)
	}
}

func TestPrepareCurrentCardPropagatesContextCancellation(t *testing.T) {
	client, _ := newSequenceTestClient(t,
		cmdResp{status: status(0x34)},
		cmdResp{status: status(0x34)},
	)
	ctx, cancel := context.WithCancel(context.Background())
	client.sequenceTiming.wait = func(context.Context, time.Duration) error {
		cancel()
		return ctx.Err()
	}

	_, err := client.PrepareCurrentCard(ctx)
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("error = %v, want context.Canceled", err)
	}
}

func TestBeginPrepareNextCardDispatchesWithoutReadinessPolling(t *testing.T) {
	client, device := newSequenceTestClient(t)

	if err := client.BeginPrepareNextCard(context.Background()); err != nil {
		t.Fatal(err)
	}
	if got := commandCount(device.commands, cmdToEncoder); got != 1 {
		t.Fatalf("to-encoder commands = %d, want 1", got)
	}
	if got := commandCount(device.commands, cmdStatus); got != 0 {
		t.Fatalf("status reads = %d, want 0", got)
	}
}

func TestBeginPrepareNextCardReturnsDispatchFailureWithoutPolling(t *testing.T) {
	client, device := newSequenceTestClient(t)
	device.commandErrors[cmdToEncoder] = []error{errors.New("dispatch failed")}

	err := client.BeginPrepareNextCard(context.Background())
	if err == nil || !strings.Contains(err.Error(), "dispatch failed") {
		t.Fatalf("error = %v, want dispatch failure", err)
	}
	if got := commandCount(device.commands, cmdToEncoder); got != 1 {
		t.Fatalf("to-encoder commands = %d, want 1", got)
	}
	if got := commandCount(device.commands, cmdStatus); got != 0 {
		t.Fatalf("status reads = %d, want 0", got)
	}
}

func TestPrepareCardAtEncoderRequiresConfirmedEncoderState(t *testing.T) {
	tests := []struct {
		name          string
		responses     []cmdResp
		wantError     string
		wantToEncoder int
	}{
		{
			name:          "already at encoder",
			responses:     []cmdResp{{status: status(0x33)}},
			wantToEncoder: 0,
		},
		{
			name: "moves ready card to encoder",
			responses: []cmdResp{
				{status: status(0x34)},
				{status: status(0x33)},
			},
			wantToEncoder: 1,
		},
		{
			name:          "empty card well",
			responses:     []cmdResp{{status: status(0x38)}},
			wantError:     CardWellEmptyMessage,
			wantToEncoder: 0,
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			client, device := newSequenceTestClient(t, test.responses...)

			_, err := client.PrepareNextCard(context.Background())
			if test.wantError == "" && err != nil {
				t.Fatal(err)
			}
			if test.wantError != "" && (err == nil || !strings.Contains(err.Error(), test.wantError)) {
				t.Fatalf("error = %v, want containing %q", err, test.wantError)
			}
			if got := commandCount(device.commands, cmdToEncoder); got != test.wantToEncoder {
				t.Fatalf("to-encoder commands = %d, want %d", got, test.wantToEncoder)
			}
		})
	}
}