// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

//go:build linux && cgo

package input

import (
	"fmt"
	"strings"
)

// Modifier_codes expands generic modifiers to their physical left/right keys.
func Modifier_codes(names []string) (map[uint16]bool, error) {
	keys := make(map[uint16]bool)
	for _, name := range names {
		code, ok := Key_code(name)
		if !ok {
			return nil, fmt.Errorf("invalid modifier key %q", name)
		}
		keys[code] = true
		switch strings.ToUpper(name) {
		case "KEY_META":
			keys[KeyRightMeta] = true
		case "KEY_CTRL":
			keys[KeyRightCtrl] = true
		case "KEY_SHIFT":
			keys[KeyRightShift] = true
		case "KEY_ALT":
			keys[KeyRightAlt] = true
		}
	}
	return keys, nil
}

// Fenrir_codes validates the supported configurable reader modifiers.
func Fenrir_codes(names []string) (map[uint16]bool, error) {
	if len(names) == 0 {
		return nil, fmt.Errorf("select at least one Fenrir key")
	}
	keys, err := Modifier_codes(names)
	if err != nil {
		return nil, err
	}
	for code := range keys {
		switch code {
		case KeyInsert, KeyKP0, KeyCapsLock, KeyMeta, KeyRightMeta:
		default:
			return nil, fmt.Errorf("unsupported Fenrir key %q", Key_name(code))
		}
	}
	return keys, nil
}

func Validate_modifier_keys(fenrirKeys, scriptKeys []string) error {
	reader, err := Fenrir_codes(fenrirKeys)
	if err != nil {
		return err
	}
	scripts, err := Modifier_codes(scriptKeys)
	if err != nil {
		return err
	}
	for code := range scripts {
		if reader[code] {
			return fmt.Errorf("%s cannot be both a Fenrir key and a script key", Key_name(code))
		}
	}
	return nil
}

func (r *Router) Set_fenrir_keys(names []string) error {
	keys, err := Fenrir_codes(names)
	if err != nil {
		return err
	}
	for key := range keys {
		if r.scriptKeys[key] {
			return fmt.Errorf("%s cannot be both a Fenrir key and a script key", Key_name(key))
		}
	}
	r.Reset()
	r.readerKeys = keys
	return nil
}

// Fenrir_keys returns the effective selection for the settings form.
func (r *Router) Fenrir_keys() []string {
	var keys []string
	for _, code := range []uint16{KeyKP0, KeyInsert, KeyCapsLock, KeyMeta, KeyRightMeta} {
		if !r.reader_modifier(code, false) {
			continue
		}
		if code == KeyMeta && r.reader_modifier(KeyRightMeta, false) {
			keys = append(keys, "KEY_META")
			continue
		}
		if code == KeyRightMeta && r.reader_modifier(KeyMeta, false) {
			continue
		}
		keys = append(keys, Key_name(code))
	}
	return keys
}

func (r *Router) script_modifier(key uint16, numLock bool) bool {
	return r.scriptKeys[key] && (key != KeyKP0 || !numLock)
}

// Available_fenrir_keys keeps explicitly configured script keys out of reader
// defaults. Explicit reader selections are validated instead of being changed.
func Available_fenrir_keys(readerNames, scriptNames []string) ([]string, error) {
	reader, err := Fenrir_codes(readerNames)
	if err != nil {
		return nil, err
	}
	scripts, err := Modifier_codes(scriptNames)
	if err != nil {
		return nil, err
	}
	var names []string
	for _, key := range []uint16{KeyKP0, KeyInsert, KeyCapsLock, KeyMeta, KeyRightMeta} {
		if reader[key] && !scripts[key] {
			names = append(names, Key_name(key))
		}
	}
	if len(names) == 0 {
		return nil, fmt.Errorf("select at least one Fenrir key that is not a script key")
	}
	return names, nil
}

func (r *Router) Configure_modifiers(fenrirKeys, scriptKeys []string) error {
	if fenrirKeys == nil {
		var err error
		fenrirKeys, err = Available_fenrir_keys(r.Fenrir_keys(), scriptKeys)
		if err != nil {
			return err
		}
	}
	if err := Validate_modifier_keys(fenrirKeys, scriptKeys); err != nil {
		return err
	}
	candidate := *r
	candidate.scriptKeys = nil
	if err := candidate.Set_fenrir_keys(fenrirKeys); err != nil {
		return err
	}
	if err := candidate.Configure_scripts(scriptKeys, nil); err != nil {
		return err
	}
	candidate.scriptBindings = r.scriptBindings
	*r = candidate
	return nil
}