//go:build linux

/*
 * ============================================================================
 * Projekt.....: rs2322tcp
 * Datei.......: internal/client/virtual_port_linux_test.go
 * Copyright (C) 2026 Dieter Lang
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * Beschreibung:
 * Tests für die Linux-spezifische Verwaltung der internen Symlinks
 * virtueller rs2322tcp-Seriellschnittstellen.
 * ============================================================================
 */
package client

import (
	"os"
	"path/filepath"
	"reflect"
	"testing"

	"git.lang-dieter.de/rs2322tcp/internal/config"
)

func TestVirtualPortLinkPath(t *testing.T) {
	path, err := virtualPortLinkPath("/dev/ttyUSB100")
	if err != nil {
		t.Fatalf("virtualPortLinkPath() failed: %v", err)
	}

	wantSuffix := filepath.Join(
		".rs2322tcp",
		"virtual",
		"ttyUSB100",
	)

	if !filepath.IsAbs(path) {
		t.Fatalf("path is not absolute: %q", path)
	}

	if !hasPathSuffix(path, wantSuffix) {
		t.Errorf(
			"virtualPortLinkPath() = %q, want suffix %q",
			path,
			wantSuffix,
		)
	}
}

func TestSetAndRemoveVirtualPortLink(t *testing.T) {
	tempHome := t.TempDir()

	t.Setenv("HOME", tempHome)

	portPath := "/dev/ttyUSB100"
	target := "/dev/pts/2"

	if err := setVirtualPortLink(portPath, target); err != nil {
		t.Fatalf("setVirtualPortLink() failed: %v", err)
	}

	linkPath, err := virtualPortLinkPath(portPath)
	if err != nil {
		t.Fatalf("virtualPortLinkPath() failed: %v", err)
	}

	got, err := os.Readlink(linkPath)
	if err != nil {
		t.Fatalf("Readlink() failed: %v", err)
	}

	if got != target {
		t.Errorf(
			"link target = %q, want %q",
			got,
			target,
		)
	}

	if err := removeVirtualPortLink(portPath); err != nil {
		t.Fatalf("removeVirtualPortLink() failed: %v", err)
	}

	if _, err := os.Lstat(linkPath); !os.IsNotExist(err) {
		t.Fatalf(
			"link still exists after removal: %q",
			linkPath,
		)
	}
}

func TestSetVirtualPortLinkReplacesExistingLink(t *testing.T) {
	tempHome := t.TempDir()

	t.Setenv("HOME", tempHome)

	portPath := "/dev/ttyUSB100"

	if err := setVirtualPortLink(
		portPath,
		"/dev/pts/2",
	); err != nil {
		t.Fatalf(
			"first setVirtualPortLink() failed: %v",
			err,
		)
	}

	if err := setVirtualPortLink(
		portPath,
		"/dev/pts/7",
	); err != nil {
		t.Fatalf(
			"second setVirtualPortLink() failed: %v",
			err,
		)
	}

	linkPath, err := virtualPortLinkPath(portPath)
	if err != nil {
		t.Fatalf("virtualPortLinkPath() failed: %v", err)
	}

	got, err := os.Readlink(linkPath)
	if err != nil {
		t.Fatalf("Readlink() failed: %v", err)
	}

	if got != "/dev/pts/7" {
		t.Errorf(
			"link target = %q, want %q",
			got,
			"/dev/pts/7",
		)
	}
}

func TestRemoveVirtualPortLinkMissing(t *testing.T) {
	tempHome := t.TempDir()

	t.Setenv("HOME", tempHome)

	if err := removeVirtualPortLink("/dev/ttyUSB100"); err != nil {
		t.Fatalf(
			"removeVirtualPortLink() failed for missing link: %v",
			err,
		)
	}
}

func TestVirtualPortLinkPathUsesBaseName(t *testing.T) {
	path, err := virtualPortLinkPath("/dev/ttyUSB123")
	if err != nil {
		t.Fatalf("virtualPortLinkPath() failed: %v", err)
	}

	if filepath.Base(path) != "ttyUSB123" {
		t.Errorf(
			"filepath.Base() = %q, want %q",
			filepath.Base(path),
			"ttyUSB123",
		)
	}
}

func TestExistingVirtualPortLinksNone(t *testing.T) {
	tempDir := t.TempDir()

	cfg := config.VirtualPortRangeConfig{
		First: 100,
		Last:  102,
	}

	got, err := existingVirtualPortLinksInDirectory(
		cfg,
		tempDir,
	)
	if err != nil {
		t.Fatalf(
			"existingVirtualPortLinksInDirectory() failed: %v",
			err,
		)
	}

	if len(got) != 0 {
		t.Fatalf(
			"existingVirtualPortLinksInDirectory() = %v, want empty list",
			got,
		)
	}
}

func TestExistingVirtualPortLinksFindsSymlinks(t *testing.T) {
	tempDir := t.TempDir()

	cfg := config.VirtualPortRangeConfig{
		First: 100,
		Last:  102,
	}

	for _, number := range []int{100, 102} {
		path := filepath.Join(
			tempDir,
			"ttyUSB"+itoa(number),
		)

		if err := os.Symlink(
			"/dev/pts/"+itoa(number),
			path,
		); err != nil {
			t.Fatalf(
				"create test symlink %q: %v",
				path,
				err,
			)
		}
	}

	got, err := existingVirtualPortLinksInDirectory(
		cfg,
		tempDir,
	)
	if err != nil {
		t.Fatalf(
			"existingVirtualPortLinksInDirectory() failed: %v",
			err,
		)
	}

	want := []string{
		filepath.Join(tempDir, "ttyUSB100"),
		filepath.Join(tempDir, "ttyUSB102"),
	}

	if !reflect.DeepEqual(got, want) {
		t.Fatalf(
			"existingVirtualPortLinksInDirectory() = %v, want %v",
			got,
			want,
		)
	}
}

func TestExistingVirtualPortLinksIgnoresRegularFile(t *testing.T) {
	tempDir := t.TempDir()

	cfg := config.VirtualPortRangeConfig{
		First: 100,
		Last:  102,
	}

	path := filepath.Join(tempDir, "ttyUSB100")

	if err := os.WriteFile(
		path,
		[]byte("not a symlink"),
		0644,
	); err != nil {
		t.Fatalf(
			"create regular test file %q: %v",
			path,
			err,
		)
	}

	got, err := existingVirtualPortLinksInDirectory(
		cfg,
		tempDir,
	)
	if err != nil {
		t.Fatalf(
			"existingVirtualPortLinksInDirectory() failed: %v",
			err,
		)
	}

	if len(got) != 0 {
		t.Fatalf(
			"regular file was detected as virtual port: %v",
			got,
		)
	}
}

func TestExistingVirtualPortLinksIgnoresOutsideRange(t *testing.T) {
	tempDir := t.TempDir()

	cfg := config.VirtualPortRangeConfig{
		First: 100,
		Last:  102,
	}

	path := filepath.Join(tempDir, "ttyUSB103")

	if err := os.Symlink(
		"/dev/pts/103",
		path,
	); err != nil {
		t.Fatalf(
			"create outside-range symlink %q: %v",
			path,
			err,
		)
	}

	got, err := existingVirtualPortLinksInDirectory(
		cfg,
		tempDir,
	)
	if err != nil {
		t.Fatalf(
			"existingVirtualPortLinksInDirectory() failed: %v",
			err,
		)
	}

	if len(got) != 0 {
		t.Fatalf(
			"outside-range symlink was detected: %v",
			got,
		)
	}
}

func itoa(number int) string {
	const digits = "0123456789"

	if number == 0 {
		return "0"
	}

	result := ""

	for number > 0 {
		result = string(digits[number%10]) + result
		number /= 10
	}

	return result
}

func hasPathSuffix(path string, suffix string) bool {
	return path == suffix ||
		len(path) > len(suffix) &&
			path[len(path)-len(suffix):] == suffix
}