// 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>.

//go:build linux && cgo

package terminal

/*
#include "native.h"
*/
import "C"

import (
	"fmt"
	"unsafe"

	"git.stormux.org/storm/fenrir/internal/diagnostic"
	"git.stormux.org/storm/fenrir/internal/input"
)

// Keyboard returns the input side of this session. Commands use exactly the
// same router, modal capture and app dispatcher as evdev.
func (s *Session) Keyboard() *Keyboard { return &Keyboard{session: s} }

type Keyboard struct{ session *Session }

func (k *Keyboard) Events() <-chan error { return k.session.inputEvents }
func (k *Keyboard) Scan() error          { return nil }
func (k *Keyboard) Pass_next()           { k.session.router.Pass_next() }
func (k *Keyboard) Capture(enabled bool) error {
	s := k.session
	if enabled && !s.grabbed {
		status, err := s.capture_keyboard()
		if err != nil {
			return err
		}
		if status != 0 {
			return fmt.Errorf("X11 terminal capture unavailable (status %d)", status)
		}
	}
	s.router.Capture(enabled)
	if enabled {
		// Bytes already replayed by xterm must not reach the child during a form.
		s.pending = nil
		s.pasteStart, s.pasteEnd = 0, 0
	}
	// The closing key is already in the router but may not yet be in s.held:
	// Capture(false) can run from handle inside Poll. Keep that grab until its
	// release rather than ungrabbing and regrabbing with an older timestamp.
	if !enabled && !s.router.Held(0) && len(s.held) == 0 && s.grabbed {
		C.terminal_x_release(s.x)
		s.grabbed = false
	}
	return nil
}
func (k *Keyboard) Close() error {
	C.terminal_x_release(k.session.x)
	return nil
}

// Update_modifiers applies only between complete chords and outside modal capture.
// The native transaction retains the previous grabs if any new grab is refused.
func (k *Keyboard) Update_modifiers(fenrirKeys, scriptKeys []string) (bool, error) {
	s := k.session
	if s.router.Captured() || s.grabbed || s.captureBlocked || len(s.held) != 0 || len(s.replayed) != 0 {
		return false, nil
	}
	candidate := s.router
	if err := candidate.Configure_modifiers(fenrirKeys, scriptKeys); err != nil {
		return false, err
	}
	var keys []C.int
	for _, key := range append(candidate.Reader_keys(), candidate.Script_keys()...) {
		keys = append(keys, C.int(key))
	}
	var keyPointer *C.int
	if len(keys) > 0 {
		keyPointer = &keys[0]
	}
	status := C.terminal_x_update_keys(s.x, keyPointer, C.int(len(keys)))
	if err := native_error(status); err != nil {
		return false, fmt.Errorf("update X11 modifier keys: %w", err)
	}
	if status != 0 {
		return false, nil
	}
	s.router = candidate
	return true, nil
}

// capture_keyboard treats desktop/focus contention as a refused chord, not a
// terminal-session failure. Keep modal intent while discarding stale key state.
func (s *Session) capture_keyboard() (int, error) {
	status := C.terminal_x_consume(s.x)
	if err := native_error(status); err != nil {
		return 0, fmt.Errorf("acquire X11 terminal keyboard: %w", err)
	}
	if status == 0 {
		s.grabbed = true
		return 0, nil
	}
	diagnostic.Record("X11 keyboard capture refused", "status", int(status))
	C.terminal_x_release(s.x)
	captured := s.router.Captured()
	s.router.Reset()
	s.router.Capture(captured)
	clear(s.held)
	clear(s.replayed)
	s.grabbed = false
	s.captureBlocked = true
	return int(status), nil
}

func (k *Keyboard) Poll(active, numLock bool, handle func(input.Decision)) error {
	s := k.session
	for code, key := range s.replayed {
		if C.terminal_x_down(s.x, C.int(code)) == 0 {
			s.router.Key(0, key, 0, numLock, true)
			delete(s.replayed, code)
		}
	}
	for {
		var event C.TerminalEvent
		code := C.terminal_x_next(s.x, &event)
		if code == 0 {
			break
		}
		if err := native_error(code); err != nil {
			return fmt.Errorf("X11 terminal input: %w", err)
		}
		if event._type != 1 {
			continue
		}
		if s.captureBlocked {
			// Do not reinterpret the tail of a refused Fenrir chord as a bare
			// command after its modifier state was cleared. Drain until key-up.
			C.terminal_x_release(s.x)
			continue
		}
		if !active {
			C.terminal_x_release(s.x)
			continue
		}
		// ReplayKeyboard redelivers a forwarded press to normal event
		// observers, including us. It must not interrupt speech twice.
		if event.value == 1 && s.lastReplay.code == int(event.keycode) && s.lastReplay.time == uint64(event.time) {
			continue
		}
		key := uint16(C.terminal_key_code(event.symbol, event.keycode))
		if held, exists := s.held[int(event.keycode)]; exists {
			key = held
		}
		// Synchronize standard modifiers that xterm received before our grab.
		for _, modifier := range []struct {
			key  uint16
			mask uint32
		}{
			{input.KeyShift, 1}, {input.KeyCtrl, 4}, {input.KeyAlt, 8},
		} {
			value := int32(0)
			if uint32(event.state)&modifier.mask != 0 {
				value = 1
			}
			if modifier.key != key {
				s.router.Observe_modifier(1, modifier.key, value, numLock)
			}
		}
		value := int32(event.value)
		if value == 1 {
			if _, exists := s.held[int(event.keycode)]; exists {
				value = 2
			}
		}
		decision := s.router.Key(0, key, value, numLock, false)
		if key == input.KeyCapsLock && s.router.Caps_modifier() {
			if value == 1 {
				s.capsConsumed = !decision.Forward
				s.capsRestore = uint32(event.state)&2 != 0
			}
			if s.capsConsumed && value != 2 {
				// XKB locks on press and can unlock on release, even for grabbed keys.
				enabled := C.int(0)
				if s.capsRestore {
					enabled = 1
				}
				if err := native_error(C.terminal_x_caps_lock(s.x, enabled)); err != nil {
					return err
				}
			}
			if value == 0 {
				s.capsConsumed = false
			}
		}
		if decision.ToggleCapsLock {
			if err := native_error(C.terminal_x_toggle_caps(s.x)); err != nil {
				return err
			}
		}
		// Acquire before dispatch: a failed capture must not execute a command
		// or open a form from a partial, stale chord.
		if event.value == 1 && !decision.Forward && !s.grabbed {
			status, err := s.capture_keyboard()
			if err != nil {
				return err
			}
			if status != 0 {
				continue
			}
		}
		if decision.UI != nil {
			decision.UI.Text = C.GoStringN(&event.text[0], event.length)
			// Control+A arrives as a control character from XLookupString.
			if decision.UI.Ctrl && event.symbol >= 'a' && event.symbol <= 'z' {
				decision.UI.Text = string(rune(event.symbol))
			}
		}
		handle(decision)
		if event.value == 1 {
			if decision.Forward && !s.grabbed {
				C.terminal_x_replay(s.x, event.time)
				s.lastReplay.code, s.lastReplay.time = int(event.keycode), uint64(event.time)
				s.replayed[int(event.keycode)] = key
			} else {
				s.held[int(event.keycode)] = key
				if decision.Forward {
					var bytes [256]byte
					n := int(C.terminal_key(s.vt.native, &event, (*C.char)(unsafe.Pointer(&bytes[0])), C.int(len(bytes))))
					s.pending = append(s.pending, bytes[:n]...)
				}
			}
		} else {
			delete(s.replayed, int(event.keycode))
			delete(s.held, int(event.keycode))
			if len(s.held) == 0 && s.grabbed && !s.router.Captured() {
				C.terminal_x_release(s.x)
				s.grabbed = false
			}
		}
	}
	if s.captureBlocked && C.terminal_x_keys_down(s.x) == 0 {
		s.captureBlocked = false
	}
	return s.relay_input()
}