// 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 input

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

// Layout_paths keeps named TOML layouts in Fenrir's keyboard directories.
// Explicit paths select exactly one file. The bundle is an on-disk runtime asset.
func Layout_paths(layout, home string, uid int, bundledDirectory string) ([]string, error) {
	if strings.TrimSpace(layout) == "" || strings.ContainsAny(layout, "\x00\r\n") {
		return nil, fmt.Errorf("keyboard layout cannot be empty or contain control characters")
	}
	if filepath.Ext(layout) != "" && filepath.Ext(layout) != ".toml" {
		return nil, fmt.Errorf("keyboard layout must use TOML")
	}
	if strings.ContainsRune(layout, filepath.Separator) || filepath.IsAbs(layout) {
		if filepath.Ext(layout) != ".toml" {
			return nil, fmt.Errorf("keyboard layout path must end in .toml")
		}
		return []string{layout}, nil
	}
	name := strings.TrimSuffix(layout, ".toml")
	if name == "" || name == "." || name == ".." {
		return nil, fmt.Errorf("invalid keyboard layout name")
	}
	name += ".toml"
	paths := []string{}
	if uid != 0 {
		paths = append(paths, filepath.Join(home, ".local/share/stormux/fenrirscreenreader/keyboard", name))
	}
	paths = append(paths, filepath.Join("/etc/fenrirscreenreader/keyboard", name))
	if bundledDirectory != "" {
		paths = append(paths, filepath.Join(bundledDirectory, name))
	}
	return paths, nil
}

// Load_bindings selects one whole file. A malformed or unreadable candidate
// stops loading; only absent named candidates advance to the next directory.
func Load_bindings(paths []string) (Layout, string, error) {
	for _, path := range paths {
		file, err := os.Open(path)
		if errors.Is(err, os.ErrNotExist) {
			continue
		}
		if err != nil {
			return Layout{}, path, err
		}
		data, readErr := io.ReadAll(io.LimitReader(file, (1<<20)+1))
		closeErr := file.Close()
		if err := errors.Join(readErr, closeErr); err != nil {
			return Layout{}, path, err
		}
		if len(data) > 1<<20 {
			return Layout{}, path, fmt.Errorf("keyboard layout exceeds 1 MiB")
		}
		bindings, err := Decode_bindings(data)
		return bindings, path, err
	}
	return Layout{}, "", fmt.Errorf("keyboard layout not found (searched %s)", strings.Join(paths, ", "))
}