// Cthulhu screen reader.
// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
//
// 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 app

import (
	"context"
	"time"

	"git.stormux.org/storm/cthulhu/internal/atspi"
	"git.stormux.org/storm/cthulhu/internal/input"
)

// Interrupt drops retained requests and wakes the owned cancellation worker.
// It must never perform backend I/O in the caller's event loop.
func (worker *speechWorker) Interrupt() {
	worker.mutex.Lock()
	defer worker.mutex.Unlock()
	if worker.confirmationID != 0 || worker.has_uninterruptible_locked() {
		return
	}
	worker.interruptLocked()
}

// The preferences worker changes speech availability after the backend has
// accepted a new configuration. Disabling also retires pending and active
// utterances before the new setting becomes visible to event producers.
func (worker *speechWorker) SetEnabled(enabled bool) {
	worker.mutex.Lock()
	defer worker.mutex.Unlock()
	if worker.enabled == enabled {
		return
	}
	worker.enabled = enabled
	if !enabled {
		worker.startupUntil = time.Time{}
		worker.interruptLocked()
	}
}

func (worker *speechWorker) interruptLocked() {
	if worker.uninterruptibleCancel != nil {
		worker.uninterruptibleCancel()
	}
	worker.presentationDelivery = nil
	worker.confirmationID = 0
	if worker.beepCancel != nil {
		worker.beepCancel()
	}
	worker.titleInput.protectRepeats = false
	worker.titleWindow = atspi.ObjectID{}
	if worker.readAllCancel != nil {
		worker.readAllCancel()
		worker.readAllCancel = nil
	}
	if time.Now().Before(worker.startupUntil) {
		return
	}
	if !worker.running {
		return
	}
	completeSpeechRequests(worker.pending, context.Canceled)
	worker.pending = nil
	worker.generation++
	worker.interrupting = true

	select {
	case worker.interrupt <- struct{}{}:
	default:
	}
}

func (worker *speechWorker) BeginReadAll(ctx context.Context, timestamp uint32) context.Context {
	worker.mutex.Lock()
	defer worker.mutex.Unlock()
	worker.startupUntil = time.Time{}
	if !worker.has_uninterruptible_locked() {
		worker.interruptLocked()
	} else if worker.readAllCancel != nil {
		worker.readAllCancel()
	}
	readContext, cancel := context.WithCancel(ctx)
	worker.readAllCancel = cancel
	worker.readAllTimestamp = timestamp
	return readContext
}

func (worker *speechWorker) InterruptForInput(event input.Event) bool {
	worker.mutex.Lock()
	defer worker.mutex.Unlock()
	if event.Timestamp != 0 && worker.commandTimestamp != 0 && int32(event.Timestamp-worker.commandTimestamp) <= 0 {
		return false
	}
	// XRecord and command grabs arrive on separate goroutines. A delayed
	// copy of the initiating chord must not cancel the reading it just began.
	if worker.readAllCancel != nil && event.Timestamp != 0 && worker.readAllTimestamp != 0 && int32(event.Timestamp-worker.readAllTimestamp) <= 0 {
		return false
	}
	if worker.readAllCancel == nil && worker.titleInput.preserves(event) {
		worker.logger.Debug("preserved title speech during held-key repeat", "input_timestamp", event.Timestamp,
			"input_keycode", event.Keycode)
		return false
	}
	if event.Timestamp != 0 {
		worker.lastInputTimestamp = event.Timestamp
	}
	if worker.has_uninterruptible_locked() {
		return false
	}
	worker.startupUntil = time.Time{}
	worker.interruptLocked()
	return true
}

// ProtectCommand ignores delayed copies of input which already dispatched a
// command. A newly dispatched command also interrupts confirmation speech,
// even when its XRecord input has not arrived yet.
func (worker *speechWorker) ProtectCommand(timestamp uint32) {
	worker.mutex.Lock()
	defer worker.mutex.Unlock()
	if timestamp != 0 && worker.commandTimestamp != 0 && int32(timestamp-worker.commandTimestamp) <= 0 {
		return
	}
	if timestamp != 0 {
		worker.commandTimestamp = timestamp
	}
	if worker.confirmationID != 0 && !worker.has_uninterruptible_locked() {
		worker.interruptLocked()
	}
}

// Startup announcements need a brief window in which automatic focus events
// append instead of replacing them. A real key press ends that protection.
func (worker *speechWorker) EnqueueStartup(request speechRequest) {
	worker.mutex.Lock()
	worker.startupUntil = time.Now().Add(3 * time.Second)
	worker.mutex.Unlock()
	worker.Enqueue(request)
}

func (worker *speechWorker) InterruptForUser() {
	worker.mutex.Lock()
	defer worker.mutex.Unlock()
	if worker.has_uninterruptible_locked() {
		return
	}
	worker.startupUntil = time.Time{}
	worker.interruptLocked()
}

func (worker *speechWorker) cancelActiveSpeech(ctx context.Context) {
	defer close(worker.cancelDone)
	for {
		select {
		case <-ctx.Done():
			return
		case <-worker.interrupt:
		}
		worker.mutex.Lock()
		select {
		case <-worker.interrupt:
		default:
		}
		generation := worker.generation
		activeDone := worker.activeDone
		worker.mutex.Unlock()
		worker.cancelSpeech(ctx)
		if activeDone != nil {
			select {
			case <-ctx.Done():
				return
			case <-activeDone:
			}
			// SPEAK may have been accepted after the first CANCEL. Keep new
			// requests behind the barrier until that in-flight call is settled.
			worker.cancelSpeech(ctx)
		}
		worker.mutex.Lock()
		if generation == worker.generation {
			worker.interrupting = false
		}
		worker.mutex.Unlock()
		select {
		case worker.wake <- struct{}{}:
		default:
		}
	}
}

func (worker *speechWorker) cancelSpeech(ctx context.Context) {
	if err := worker.speaker.Cancel(ctx); err != nil && ctx.Err() == nil {
		worker.logger.Warn("interrupt speech", "error", err)
	}
}