// SPDX-FileCopyrightText: 2026 Echolot contributors
// SPDX-License-Identifier: GPL-3.0-or-later

package selftest

import (
	"net"
	"strconv"
	"strings"
	"testing"
)

// The real check runs against ports 80/443, which a test cannot bind without privileges; the
// port list is what varies here, the mechanism is identical.

func TestOccupiedPortIsDetected(t *testing.T) {
	// The stray-process scenario: someone else holds the port before we look.
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer ln.Close()
	port := strconv.Itoa(ln.Addr().(*net.TCPAddr).Port)

	occupied, unverifiable := portsFree([]net.IP{net.ParseIP("127.0.0.1")}, []string{port})
	if len(occupied) != 1 || !strings.HasSuffix(occupied[0], ":"+port) {
		t.Fatalf("a listening port must be reported occupied, got occupied=%v unverifiable=%v",
			occupied, unverifiable)
	}
}

func TestFreePortPassesAndStaysFree(t *testing.T) {
	// Find a port that is free by construction, then check it.
	probe, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	port := strconv.Itoa(probe.Addr().(*net.TCPAddr).Port)
	probe.Close()

	occupied, unverifiable := portsFree([]net.IP{net.ParseIP("127.0.0.1")}, []string{port})
	if len(occupied) != 0 || len(unverifiable) != 0 {
		t.Fatalf("a free port must pass silently, got occupied=%v unverifiable=%v",
			occupied, unverifiable)
	}
	// The check must not keep the port: it proves the state and gets out of the way.
	ln, err := net.Listen("tcp", "127.0.0.1:"+port)
	if err != nil {
		t.Fatalf("the check left the port unusable: %v", err)
	}
	ln.Close()
}

func TestUnassignedAddressIsUnverifiableNotOccupied(t *testing.T) {
	// 192.0.2.0/24 is TEST-NET-1: never assigned to this host, so the bind fails with something
	// other than EADDRINUSE. That is "could not answer", not "occupied" — conflating them would
	// refuse startup over a typo in ECHOLOT_RESERVED_ADDRS.
	occupied, unverifiable := portsFree([]net.IP{net.ParseIP("192.0.2.1")}, []string{"65001"})
	if len(occupied) != 0 {
		t.Fatalf("an unassigned address must not be reported occupied: %v", occupied)
	}
	if len(unverifiable) != 1 {
		t.Fatalf("an unassigned address must be reported unverifiable, got %v", unverifiable)
	}
}