// Fenrir console screen reader.
// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program. If not, see <https://www.gnu.org/licenses/gpl-3.0.html>.

package clipboard

import (
	"fmt"
	"os"
	"os/user"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
)

type Target struct{ Display, Authority string }

// Display_candidates never falls through an explicit setting or DISPLAY to a
// different session. Discovery uses existing local sockets, not a fixed :0..:9.
func Display_candidates(configured, current, authority, home, socketDirectory string) ([]Target, error) {
	if authority == "" {
		authority = filepath.Join(home, ".Xauthority")
	}
	if configured != "" {
		return []Target{{configured, authority}}, nil
	}
	if current != "" {
		return []Target{{current, authority}}, nil
	}
	entries, err := os.ReadDir(socketDirectory)
	if err != nil {
		return nil, err
	}
	var targets []Target
	for _, entry := range entries {
		name := entry.Name()
		if !strings.HasPrefix(name, "X") {
			continue
		}
		number, err := strconv.Atoi(name[1:])
		if err != nil || number < 0 {
			continue
		}
		info, err := entry.Info()
		if err == nil && info.Mode()&os.ModeSocket != 0 {
			targets = append(targets, Target{fmt.Sprintf(":%d", number), authority})
		}
	}
	sort.Slice(targets, func(i, j int) bool { return targets[i].Display < targets[j].Display })
	if len(targets) == 0 {
		return nil, fmt.Errorf("no local X display")
	}
	// Multiple desktops require an explicit choice; do not silently mix users.
	if len(targets) > 1 {
		return nil, fmt.Errorf("multiple X displays; set clipboard.sync_display")
	}
	return targets, nil
}

func system_targets(configured string) ([]Target, error) {
	home, _ := os.UserHomeDir()
	if os.Geteuid() == 0 && os.Getenv("SUDO_UID") != "" {
		if caller, err := user.LookupId(os.Getenv("SUDO_UID")); err == nil {
			home = caller.HomeDir
		}
	}
	targets, err := Display_candidates(configured, os.Getenv("DISPLAY"), os.Getenv("XAUTHORITY"), home, "/tmp/.X11-unix")
	if err != nil {
		return nil, err
	}
	if os.Getenv("XAUTHORITY") == "" {
		// Console services may lack a desktop environment. Xorg's -auth names
		// the actual cookie file, including display-manager runtime locations.
		// Read command-line metadata only; never log or copy cookie contents.
		paths, _ := filepath.Glob("/proc/[0-9]*/cmdline")
		for _, path := range paths {
			data, err := os.ReadFile(path)
			if err != nil {
				continue
			}
			args := strings.Split(strings.TrimRight(string(data), "\x00"), "\x00")
			if len(args) == 0 {
				continue
			}
			switch filepath.Base(args[0]) {
			case "Xorg", "X", "Xwayland":
			default:
				continue
			}
			display, auth := "", ""
			for i, arg := range args {
				if strings.HasPrefix(arg, ":") {
					display = arg
				}
				if arg == "-auth" && i+1 < len(args) {
					auth = args[i+1]
				}
			}
			for i := range targets {
				if display != "" && strings.SplitN(targets[i].Display, ".", 2)[0] == display && auth != "" {
					targets[i].Authority = auth
				}
			}
		}
	}
	return targets, nil
}