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

package atspi

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

import (
	"context"
	"errors"
	"fmt"
	"git.stormux.org/storm/cthulhu/internal/platform/session"
	"git.stormux.org/storm/cthulhu/internal/platform/xorg"
	"runtime"
	"runtime/cgo"
	"sync"
	"unsafe"
)

// libatspi and its default GLib loop are process globals. Adapters may take
// turns owning them, but must never run concurrently. atspi_exit is reserved
// for process exit: its caches do not support an exit/init cycle.
var nativeAdapterOwner sync.Mutex
var nativeAdapterInit sync.Once
var nativeAdapterInitError error

func (adapter *Adapter) Start(ctx context.Context) error {
	adapter.stopMutex.Lock()
	defer adapter.stopMutex.Unlock()
	if !adapter.running.CompareAndSwap(false, true) {
		return errors.New("AT-SPI adapter already started")
	}
	if !nativeAdapterOwner.TryLock() {
		adapter.running.Store(false)
		return errors.New("another AT-SPI adapter is running")
	}

	adapter.echoFocus.Store(nil)
	adapter.loopError = nil
	adapter.stopRequested = false
	adapter.loopDone = make(chan struct{})
	setupDone := make(chan error, 1)
	go func() {
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()
		defer close(adapter.loopDone)
		defer nativeAdapterOwner.Unlock()
		if err := adapter.initialize(); err != nil {
			setupDone <- err
			return
		}
		// Xwayland only describes X clients. Its empty or stale foreground
		// must not veto native Wayland windows; use AT-SPI ownership there.
		if !session.Wayland() {
			adapter.foregroundReader = xorg.OpenForegroundReader()
		}
		adapter.promptRefreshWindow = ObjectID{}
		adapter.promptScannedWindow = ObjectID{}
		adapter.promptScannedEpoch = 0
		adapter.refreshForeground()
		adapter.refreshWindowTitle()
		timer := C.start_foreground_timer(C.gpointer(adapter.callbackData))
		setupDone <- nil
		C.atspi_event_main()
		if timer != 0 {
			C.g_source_remove(timer)
		}
		// Deregistration can dispatch queued D-Bus events synchronously. Keep
		// foreground state and retained accessibles alive until it finishes.
		adapter.loopError = adapter.releaseNativeCallbacks()
		adapter.foregroundReader.Close()
		adapter.foregroundReader = nil
		for _, focus := range adapter.nativeFocus {
			C.g_object_unref(C.gpointer(focus.source))
		}
		adapter.nativeFocus = nil
		adapter.echoFocus.Store(nil)
		adapter.libreOfficeHeaders.reset()
		for _, known := range adapter.documentWindows {
			C.g_object_unref(C.gpointer(known.source))
		}
		adapter.documentWindows = nil
		adapter.documentWindowIDs = nil
		adapter.clearStashedDocuments()
		adapter.clearNativeDocument()
		adapter.deferredLiveRegions = nil
		adapter.clearNativeReview()
		adapter.clearMouseApplication()
	}()

	select {
	case err := <-setupDone:
		if err != nil {
			<-adapter.loopDone
			adapter.running.Store(false)
			return err
		}
		if err := ctx.Err(); err != nil {
			C.cthulhu_request_event_loop_quit()
			<-adapter.loopDone
			adapter.running.Store(false)
			return err
		}
		adapter.ready.Store(true)
		return nil
	case <-ctx.Done():
		err := <-setupDone
		if err != nil {
			<-adapter.loopDone
			adapter.running.Store(false)
			return err
		}
		C.cthulhu_request_event_loop_quit()
		<-adapter.loopDone
		adapter.running.Store(false)
		return ctx.Err()
	}
}

func (adapter *Adapter) initialize() error {
	nativeAdapterInit.Do(func() {
		if result := C.atspi_init(); result > 1 {
			nativeAdapterInitError = fmt.Errorf("initialize AT-SPI: result %d", int(result))
		}
	})
	if nativeAdapterInitError != nil {
		return nativeAdapterInitError
	}
	// libatspi's ordinary default is 800 ms, but its startup grace period is
	// much longer. Keep both bounded so a newly connected or wedged provider
	// cannot indefinitely hold the event-loop thread during owned-tree capture.
	C.atspi_set_timeout(800, 800)

	callbackHandle := cgo.NewHandle(adapter)
	callbackData := C.cthulhu_callback_data_new(C.uintptr_t(callbackHandle))
	if callbackData == nil {
		callbackHandle.Delete()
		return errors.New("allocate AT-SPI callback data")
	}
	adapter.callbackHandle = callbackHandle
	adapter.callbackData = callbackData
	// Own one listener for all subscriptions, as Orca does. The callback
	// convenience API lost mouse delivery when mixed with object subscriptions
	// in the private native probe.
	adapter.eventListener = C.atspi_event_listener_new(
		C.AtspiEventListenerCB(C.cthulhu_event_callback_pointer()), C.gpointer(callbackData), nil)
	if adapter.eventListener == nil {
		C.cthulhu_callback_data_free(callbackData)
		adapter.callbackHandle = 0
		adapter.callbackData = nil
		callbackHandle.Delete()
		return errors.New("allocate AT-SPI event listener")
	}

	for _, eventType := range eventTypes {
		if err := adapter.registerEvent(eventType); err != nil {
			if cleanupErr := adapter.releaseNativeCallbacks(); cleanupErr != nil {
				err = errors.Join(err, cleanupErr)
			}
			return err
		}
	}

	return nil
}

func (adapter *Adapter) registerEvent(eventType string) error {
	nativeEventType := C.CString(eventType)
	var registerError *C.GError
	registered := C.atspi_event_listener_register(adapter.eventListener, nativeEventType, &registerError)
	C.free(unsafe.Pointer(nativeEventType))
	if registerError != nil {
		err := nativeError("register AT-SPI event listener "+eventType, registerError)
		C.g_error_free(registerError)
		return err
	}
	if registered == 0 {
		return errors.New("register AT-SPI event listener " + eventType)
	}
	return nil
}

func (adapter *Adapter) deregisterEvents() error {
	var stopErr error
	for _, eventType := range eventTypes {
		nativeEventType := C.CString(eventType)
		var deregisterError *C.GError
		C.atspi_event_listener_deregister(adapter.eventListener, nativeEventType, &deregisterError)
		C.free(unsafe.Pointer(nativeEventType))
		if deregisterError != nil {
			stopErr = errors.Join(stopErr, nativeError("deregister AT-SPI event listener "+eventType, deregisterError))
			C.g_error_free(deregisterError)
		}
	}
	if adapter.eventListener != nil {
		C.g_object_unref(C.gpointer(adapter.eventListener))
		adapter.eventListener = nil
	}
	return stopErr
}

// Called only by the GLib owner, after dispatch has stopped and request callers
// have been excluded. Destroy pending idle captures before releasing their
// callback data/handle; deregistration prevents later adapters reaching us.
func (adapter *Adapter) releaseNativeCallbacks() error {
	err := adapter.deregisterEvents()
	C.cthulhu_callback_data_free(adapter.callbackData)
	adapter.callbackData = nil
	if adapter.callbackHandle != 0 {
		adapter.callbackHandle.Delete()
		adapter.callbackHandle = 0
	}
	for len(adapter.treeRequests) != 0 {
		request := <-adapter.treeRequests
		request.result <- treeCaptureResult{err: errors.New("AT-SPI adapter stopped")}
	}
	return err
}

func (adapter *Adapter) Stop(ctx context.Context) error {
	adapter.stopMutex.Lock()
	defer adapter.stopMutex.Unlock()
	if !adapter.running.Load() {
		return nil
	}
	adapter.ready.Store(false)

	var stopErr error
	// AT-SPI documents event-loop quit as an event-handler operation. Schedule
	// it on the default GLib context owned by atspi_event_main instead of calling
	// it synchronously from this arbitrary shutdown goroutine.
	if !adapter.stopRequested {
		if C.cthulhu_request_event_loop_quit() == 0 {
			stopErr = errors.New("request AT-SPI event loop quit")
		} else {
			adapter.stopRequested = true
		}
	}

	select {
	case <-adapter.loopDone:
	case <-ctx.Done():
		return errors.Join(stopErr, fmt.Errorf("wait for AT-SPI event loop: %w", ctx.Err()))
	}
	stopErr = errors.Join(stopErr, adapter.loopError)
	adapter.running.Store(false)
	adapter.invalidateTree()
	return stopErr
}