//go:build !windows

package main

import (
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"sort"
	"strconv"
	"strings"
	"syscall"
	"time"
)

func prepareAIServerCommandForLifecycle(cmd *exec.Cmd) {
	if cmd == nil {
		return
	}
	if cmd.SysProcAttr == nil {
		cmd.SysProcAttr = &syscall.SysProcAttr{}
	}
	cmd.SysProcAttr.Setpgid = true
}

func terminateAIServerProcessTree(cmd *exec.Cmd) {
	if cmd == nil || cmd.Process == nil || cmd.Process.Pid <= 0 {
		return
	}

	pid := cmd.Process.Pid
	_ = syscall.Kill(-pid, syscall.SIGTERM)
	time.Sleep(1200 * time.Millisecond)
	_ = syscall.Kill(-pid, syscall.SIGKILL)
	_ = cmd.Process.Kill()
}

func stopStaleAIServerOnPort(port string) error {
	if runtime.GOOS != "linux" {
		return nil
	}

	portNumber, err := strconv.Atoi(strings.TrimSpace(port))
	if err != nil || portNumber <= 0 || portNumber > 65535 {
		return nil
	}

	pids, err := linuxPIDsListeningOnPort(portNumber)
	if err != nil {
		return err
	}

	currentPID := os.Getpid()
	for _, pid := range pids {
		if pid <= 0 || pid == currentPID {
			continue
		}
		if !linuxPIDLooksLikeAIServer(pid) {
			appLogf("⚠️ Listener auf AI-Port %d übersprungen, Prozess sieht nicht nach AI Server aus: pid=%d", portNumber, pid)
			continue
		}
		appLogf("🧹 Alter AI Server auf Port %d wird beendet: pid=%d", portNumber, pid)
		terminateStaleUnixPID(pid)
	}

	if len(pids) > 0 {
		time.Sleep(500 * time.Millisecond)
	}

	return nil
}

func linuxPIDsListeningOnPort(port int) ([]int, error) {
	inodes := map[string]struct{}{}
	for _, path := range []string{"/proc/net/tcp", "/proc/net/tcp6"} {
		found, err := linuxSocketInodesListeningOnPort(path, port)
		if err != nil && !os.IsNotExist(err) {
			return nil, err
		}
		for inode := range found {
			inodes[inode] = struct{}{}
		}
	}
	if len(inodes) == 0 {
		return nil, nil
	}

	entries, err := os.ReadDir("/proc")
	if err != nil {
		return nil, err
	}

	pidSet := map[int]struct{}{}
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		pid, err := strconv.Atoi(entry.Name())
		if err != nil {
			continue
		}

		fdDir := filepath.Join("/proc", entry.Name(), "fd")
		fds, err := os.ReadDir(fdDir)
		if err != nil {
			continue
		}
		for _, fd := range fds {
			target, err := os.Readlink(filepath.Join(fdDir, fd.Name()))
			if err != nil {
				continue
			}
			if !strings.HasPrefix(target, "socket:[") || !strings.HasSuffix(target, "]") {
				continue
			}
			inode := strings.TrimSuffix(strings.TrimPrefix(target, "socket:["), "]")
			if _, ok := inodes[inode]; ok {
				pidSet[pid] = struct{}{}
				break
			}
		}
	}

	pids := make([]int, 0, len(pidSet))
	for pid := range pidSet {
		pids = append(pids, pid)
	}
	sort.Ints(pids)
	return pids, nil
}

func linuxSocketInodesListeningOnPort(path string, port int) (map[string]struct{}, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}

	inodes := map[string]struct{}{}
	lines := strings.Split(string(data), "\n")
	for _, line := range lines[1:] {
		fields := strings.Fields(line)
		if len(fields) < 10 || fields[3] != "0A" {
			continue
		}

		local := fields[1]
		idx := strings.LastIndex(local, ":")
		if idx < 0 || idx+1 >= len(local) {
			continue
		}

		localPort, err := strconv.ParseInt(local[idx+1:], 16, 32)
		if err != nil || int(localPort) != port {
			continue
		}

		inode := strings.TrimSpace(fields[9])
		if inode != "" && inode != "0" {
			inodes[inode] = struct{}{}
		}
	}

	return inodes, nil
}

func terminateStaleUnixPID(pid int) {
	proc, err := os.FindProcess(pid)
	if err != nil || proc == nil {
		return
	}

	_ = proc.Signal(syscall.SIGTERM)
	time.Sleep(900 * time.Millisecond)
	_ = proc.Kill()
}

func linuxPIDLooksLikeAIServer(pid int) bool {
	data, err := os.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "cmdline"))
	if err != nil || len(data) == 0 {
		return false
	}

	cmdline := strings.ToLower(strings.ReplaceAll(string(data), "\x00", " "))
	return strings.Contains(cmdline, "ai_server:app") ||
		strings.Contains(cmdline, "ai_server.py") ||
		(strings.Contains(cmdline, "uvicorn") && strings.Contains(cmdline, "ai_server"))
}