// 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 atspi

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

/*
#cgo pkg-config: atspi-2 gobject-2.0
#include "adapter_native.h"
*/
import "C"

const eventQueueCapacity = 64

const (
	FocusEvent                 = "focus:"
	FocusedStateEvent          = "object:state-changed:focused"
	WindowActivatedEvent       = "window:activate"
	WindowDeactivatedEvent     = "window:deactivate"
	WindowDestroyedEvent       = "window:destroy"
	WindowCreateEvent          = "window:create"
	CaretEvent                 = "object:text-caret-moved"
	MouseButtonEvent           = "mouse:button"
	TextSelectionChangedEvent  = "object:text-selection-changed"
	TextInsertedEvent          = "object:text-changed:insert"
	TextDeletedEvent           = "object:text-changed:delete"
	ValueChangedEvent          = "object:value-changed"
	AccessibleValueEvent       = "object:property-change:accessible-value"
	AccessibleNameEvent        = "object:property-change:accessible-name"
	ActiveDescendantEvent      = "object:active-descendant-changed"
	SelectionChangedEvent      = "object:selection-changed"
	SelectedStateEvent         = "object:state-changed:selected"
	ChildrenChangedEvent       = "object:children-changed"
	ChildrenAddedEvent         = "object:children-changed:add"
	ChildrenRemovedEvent       = "object:children-changed:remove"
	DefunctStateEvent          = "object:state-changed:defunct"
	BoundsChangedEvent         = "object:bounds-changed"
	VisibleStateEvent          = "object:state-changed:visible"
	ShowingStateEvent          = "object:state-changed:showing"
	TextBoundsChangedEvent     = "object:text-bounds-changed"
	TextAttributesChangedEvent = "object:text-attributes-changed"
	DocumentReloadEvent        = "document:reload"
	DocumentLoadCompleteEvent  = "document:load-complete"
	DocumentLoadStoppedEvent   = "document:load-stopped"
	BusyStateEvent             = "object:state-changed:busy"
	AnnouncementEvent          = "object:announcement"
)

var eventTypes = []string{
	FocusEvent,
	FocusedStateEvent,
	WindowActivatedEvent,
	WindowDeactivatedEvent,
	WindowDestroyedEvent,
	WindowCreateEvent,
	CaretEvent,
	TextSelectionChangedEvent,
	TextInsertedEvent,
	TextDeletedEvent,
	ValueChangedEvent,
	AccessibleValueEvent,
	AccessibleNameEvent,
	ActiveDescendantEvent,
	SelectionChangedEvent,
	ChildrenChangedEvent,
	DefunctStateEvent,
	BoundsChangedEvent,
	VisibleStateEvent,
	ShowingStateEvent,
	TextBoundsChangedEvent,
	TextAttributesChangedEvent,
	DocumentReloadEvent,
	DocumentLoadCompleteEvent,
	DocumentLoadStoppedEvent,
	BusyStateEvent,
	AnnouncementEvent,
	"object:state-changed:checked",
	"object:state-changed:expanded",
	"object:state-changed:indeterminate",
	"object:state-changed:invalid-entry",
	"object:state-changed:pressed",
	"object:state-changed:read-only",
	"object:state-changed:editable",
	"object:state-changed:required",
	SelectedStateEvent,
	"object:state-changed:sensitive",
	"object:state-changed:visited",
	MouseButtonEvent,
}

type Adapter struct {
	captureLogger        atomic.Pointer[slog.Logger]
	libreOfficeHeaders   libreOfficeHeaderStore  // copied choices shared with the event loop
	applicationProcesses map[string]string       // GLib owner; bounded provider identity cache
	webNotificationRoots map[ObjectID]bool       // copied identities only; no native references
	deferredLiveRegions  deferredLiveRegionStore // GLib owner; copied identities only
	foregroundReader     *xorg.ForegroundReader  // GLib thread only
	foregroundProcesses  map[int]bool            // GLib thread; provider PID matches for current client
	foreground           atomic.Pointer[ForegroundState]
	preferencesPID       atomic.Int64 // Owned preferences helper; zero when closed.
	echoFocus            atomic.Pointer[echoFocus]
	eventListener        *C.AtspiEventListener // GLib owner; released with subscriptions.
	foregroundChanges    chan struct{}
	foregroundTitle      atomic.Pointer[ForegroundTitle]
	titleChanges         chan struct{}
	foregroundWindow     ObjectID // GLib thread: correlated accessible for current X client
	promptRefreshWindow  ObjectID // GLib thread: frame activated before its prompt label appeared
	promptScannedWindow  ObjectID // GLib thread: avoid rescanning repeated activations
	promptScannedEpoch   uint64
	foregroundRecovery   int // GLib thread: bounded retries while a new client publishes AT-SPI
	recoveringForeground bool

	events                   chan Event
	treeRequests             chan treeCaptureRequest
	overflow                 atomic.Uint64
	treeInvalidations        atomic.Uint64
	backgroundEventsFiltered atomic.Uint64 // rejected before native target/snapshot queries
	secureMutex              sync.Mutex
	secureContext            context.Context
	secureCancel             context.CancelFunc
	secureEpoch              atomic.Uint64
	secure                   atomic.Bool
	secureReset              atomic.Bool
	secureResync             atomic.Bool
	captureSound             atomic.Bool
	captureTextAttributes    atomic.Bool
	running                  atomic.Bool
	ready                    atomic.Bool
	loopDone                 chan struct{}
	loopError                error // published by closing loopDone
	stopRequested            bool  // stopMutex; keep Stop retries from queuing stale quit sources
	stopMutex                sync.Mutex
	hungMutex                sync.Mutex
	hungBuses                map[string]time.Time
	treeMutex                sync.Mutex
	tree                     *AccessibleTree
	documentTree             *AccessibleTree
	documentTextTree         *AccessibleTree
	// The active document slots above serve one document root at a time.
	// Recently captured documents are stashed by root (bounded, LRU) so
	// returning to a tab reuses its tree and retained native sources
	// instead of snapshotting the whole document cold. Guarded by
	// treeMutex; stashed sources are released only on the GLib thread.
	documentSlotRoot           ObjectID
	stashedDocuments           map[ObjectID]stashedDocument
	stashedDocumentIDs         []ObjectID
	nativeDocument             map[ObjectID]*C.AtspiAccessible
	documentLineCache          map[ObjectID]DocumentCaretText // GLib owner; at most 64 bounded text objects
	nativeReview               map[ObjectID]*C.AtspiAccessible
	nativeReviewBus            string
	navigationEcho             map[ObjectID]uint8
	navigationCaretOffset      int
	navigationSelectionOffsets map[int]bool
	nativeFocus                []nativeFocusReference // owned only by the GLib thread
	mouseApplication           *C.AtspiAccessible     // GLib owner; released on shutdown
	mouseApplicationPID        int
	documentWindows            map[ObjectID]nativeDocumentWindow
	documentWindowIDs          []ObjectID
	selectedTabWindow          ObjectID
	activeDocument             ObjectID
	callbackHandle             cgo.Handle
	callbackData               *C.cthulhu_callback_data
}

type nativeFocusReference struct {
	id     ObjectID
	source *C.AtspiAccessible
	// Only programmatic browse positions carry this proof. A subsequent native
	// focus event replaces the entry and clears it, even for the same object.
	navigationDocument ObjectReference
}

type nativeDocumentWindow struct {
	id     ObjectID
	source *C.AtspiAccessible
}

type treeCaptureResult struct {
	soundGeometry [2]SoundGeometry
	item          TransferItem
	actions       ActionSet
	point         PointReview
	ocr           OCRGeometry
	attributes    CharacterAttributes
	content       DocumentContent
	tree          *AccessibleTree
	owner         DocumentContext
	caret         DocumentCaretText
	err           error
}

type treeCaptureRequest struct {
	readFocusedSnapshot bool

	soundObjects      [2]ObjectReference
	transferItem      bool
	typeText          bool
	insertionText     string
	listActions       bool
	actionTarget      *ActionTarget
	actionName        string
	pointReview       bool
	pointX, pointY    int
	pointPID          int
	ocrGeometry       bool
	ocrZone           *Rectangle
	readFocusedText   bool
	readFocusedLine   bool
	readAttributes    bool
	setFocusedCaret   bool
	brailleRoute      *BrailleRoute
	ctx               context.Context
	reviewFocus       ObjectID
	document          bool
	documentText      bool
	contextOnly       bool
	position          ObjectReference
	caretObject       ObjectReference
	caretOffset       int
	caretUnit         DocumentCaretUnit
	positionOffset    int
	usePositionOffset bool
	activate          bool
	result            chan treeCaptureResult
}

// PointReview is copied metadata for the accessible at a screen point.
// Text ranges are optional and never include password contents.
type PointReview struct {
	Snapshot   Snapshot
	Window     ObjectID
	Word, Line string
	LineStart  int
	Offset     int // native text offset at the pointer, or -1
}

func (adapter *Adapter) ReviewAtPoint(ctx context.Context, x, y, pid int) (PointReview, error) {
	if ctx == nil {
		return PointReview{}, errors.New("review pointer: nil context")
	}
	ctx, cancel := adapter.secureRequestContext(ctx)
	defer cancel()
	adapter.stopMutex.Lock()
	defer adapter.stopMutex.Unlock()
	if !adapter.ready.Load() || adapter.callbackData == nil {
		return PointReview{}, errors.New("review pointer: adapter is not running")
	}
	request := treeCaptureRequest{ctx: ctx, pointReview: true, pointX: x, pointY: y, pointPID: pid, result: make(chan treeCaptureResult, 1)}
	select {
	case adapter.treeRequests <- request:
	case <-ctx.Done():
		return PointReview{}, ctx.Err()
	}
	if C.cthulhu_request_tree_capture(C.gpointer(unsafe.Pointer(adapter.callbackData))) == 0 {
		<-adapter.treeRequests
		return PointReview{}, errors.New("schedule pointer review")
	}
	select {
	case result := <-request.result:
		return result.point, result.err
	case <-ctx.Done():
		return PointReview{}, ctx.Err()
	}
}

func New() *Adapter {
	adapter := &Adapter{
		events:            make(chan Event, eventQueueCapacity),
		foregroundChanges: make(chan struct{}, 1),
		titleChanges:      make(chan struct{}, 1),
		treeRequests:      make(chan treeCaptureRequest, 1),
	}
	// Direct adapter users historically receive geometry. The application
	// narrows this before Start when object-sound spatialization is disabled.
	adapter.captureSound.Store(true)
	return adapter
}

// SetCaptureSoundGeometry controls synchronous component and ancestor queries
// performed while copying event snapshots. It is safe to change while the
// adapter is running; the next callback observes the new setting.
func (adapter *Adapter) SetCaptureSoundGeometry(enabled bool) {
	adapter.captureSound.Store(enabled)
}

// SetCaptureTextAttributes enables bounded native run capture for braille.
// Disabled by default to avoid extra provider queries on ordinary focus events.
func (adapter *Adapter) SetCaptureTextAttributes(enabled bool) {
	adapter.captureTextAttributes.Store(enabled)
}

func (adapter *Adapter) Events() <-chan Event {
	return adapter.events
}

func (adapter *Adapter) Overflow() uint64 {
	return adapter.overflow.Load()
}

func (adapter *Adapter) TreeInvalidations() uint64 {
	return adapter.treeInvalidations.Load()
}

// CaptureDesktop copies the current AT-SPI desktop into the adapter's owned
// tree on the native event-loop thread. Calls are serialized with shutdown so
// callback data cannot be released while a capture is pending.
func (adapter *Adapter) CaptureDesktop(ctx context.Context) (*AccessibleTree, error) {
	return adapter.capture(ctx, ObjectID{}, "desktop", false, false)
}

// CaptureReviewWindow copies the focused application's tree into the owned
// model. Flat review needs only the focused frame or dialog, so excluding
// unrelated applications keeps capture bounded on busy desktops.
func (adapter *Adapter) CaptureReviewWindow(ctx context.Context, focus ObjectID) (*AccessibleTree, error) {
	if !focus.Valid() {
		return nil, errors.New("capture AT-SPI review window: invalid focus")
	}
	return adapter.capture(ctx, focus, "review window", false, false)
}

// CaptureDocument captures semantics without flat review's viewport text work.
// Its independent tree cannot replace text required by an active flat cursor.
func (adapter *Adapter) CaptureDocument(ctx context.Context, focus ObjectID) (*AccessibleTree, error) {
	if !focus.Valid() {
		return nil, errors.New("capture AT-SPI document: invalid focus")
	}
	return adapter.capture(ctx, focus, "document", true, false)
}

// CaptureDocumentText also captures visible text and range geometry. Line
// assembly needs those native details; structural navigation does not.
func (adapter *Adapter) CaptureDocumentText(ctx context.Context, focus ObjectID) (*AccessibleTree, error) {
	if !focus.Valid() {
		return nil, errors.New("capture AT-SPI document text: invalid focus")
	}
	return adapter.capture(ctx, focus, "document text", true, true)
}

// SetCaptureLogger enables capture diagnostics when the logger accepts debug
// records. It can be updated without touching the GLib thread or native state.
func (adapter *Adapter) SetCaptureLogger(logger *slog.Logger) {
	adapter.captureLogger.Store(logger)
}

const providerHungCooldown = 2 * time.Second

// markProviderHung records a capture deadline for one application bus.
// Orca similarly remembers hung objects briefly so later commands skip
// straight past a provider that just stalled.
func (adapter *Adapter) markProviderHung(busName string, at time.Time) {
	if busName == "" {
		return
	}
	adapter.hungMutex.Lock()
	defer adapter.hungMutex.Unlock()
	if adapter.hungBuses == nil {
		adapter.hungBuses = make(map[string]time.Time)
	}
	adapter.hungBuses[busName] = at
}

func (adapter *Adapter) providerHung(busName string, at time.Time) bool {
	adapter.hungMutex.Lock()
	defer adapter.hungMutex.Unlock()
	since, ok := adapter.hungBuses[busName]
	if !ok {
		return false
	}
	if at.Sub(since) > providerHungCooldown {
		delete(adapter.hungBuses, busName)
		return false
	}
	return true
}

func (adapter *Adapter) capture(ctx context.Context, reviewFocus ObjectID, captureName string, document, documentText bool) (tree *AccessibleTree, err error) {
	if ctx == nil {
		return nil, fmt.Errorf("capture AT-SPI %s: nil context", captureName)
	}
	ctx, cancel := adapter.secureRequestContext(ctx)
	defer cancel()
	if document && adapter.providerHung(reviewFocus.BusName, time.Now()) {
		return nil, fmt.Errorf("%w: bus %q", ErrProviderHung, reviewFocus.BusName)
	}
	var trace *captureDiagnostics
	if reviewFocus.Valid() {
		ctx, trace = new_capture_diagnostics(ctx, adapter.captureLogger.Load(), reviewFocus)
		if trace != nil && document {
			trace.kind = "document"
		}
		defer func() { trace.finish(err) }()
	}
	if err := ctx.Err(); err != nil {
		return nil, err
	}

	adapter.stopMutex.Lock()
	defer adapter.stopMutex.Unlock()
	if !adapter.ready.Load() || adapter.callbackData == nil {
		return nil, fmt.Errorf("capture AT-SPI %s: adapter is not running", captureName)
	}
	if err := ctx.Err(); err != nil {
		return nil, err
	}

	request := treeCaptureRequest{
		ctx:          ctx,
		reviewFocus:  reviewFocus,
		document:     document,
		documentText: documentText,
		result:       make(chan treeCaptureResult, 1),
	}
	trace.begin_stage("queue-wait", reviewFocus, "")
	select {
	case adapter.treeRequests <- request:
	case <-ctx.Done():
		return nil, ctx.Err()
	}
	if C.cthulhu_request_tree_capture(C.gpointer(unsafe.Pointer(adapter.callbackData))) == 0 {
		<-adapter.treeRequests
		return nil, fmt.Errorf("schedule AT-SPI %s capture", captureName)
	}
	select {
	case result := <-request.result:
		if document && errors.Is(result.err, context.DeadlineExceeded) {
			adapter.markProviderHung(reviewFocus.BusName, time.Now())
		}
		return result.tree, result.err
	case <-ctx.Done():
		if document && errors.Is(ctx.Err(), context.DeadlineExceeded) {
			adapter.markProviderHung(reviewFocus.BusName, time.Now())
		}
		return nil, ctx.Err()
	}
}

func (adapter *Adapter) installTree(root ObjectID, nodes []TreeNode) (*AccessibleTree, error) {
	return adapter.installCapturedTree(root, nodes, false, false)
}

const maxStashedDocuments = 3

type stashedDocument struct {
	tree, textTree *AccessibleTree
	sources        map[ObjectID]*C.AtspiAccessible
}

// Source membership survives tree invalidation until the next capture, so it
// can identify the owner of a removed focus without guessing from its bus.
func (adapter *Adapter) retainedDocumentRoot(id ObjectID) ObjectID {
	adapter.treeMutex.Lock()
	defer adapter.treeMutex.Unlock()
	if _, retained := adapter.nativeDocument[id]; retained {
		return adapter.documentSlotRoot
	}
	for _, root := range adapter.stashedDocumentIDs {
		if _, retained := adapter.stashedDocuments[root].sources[id]; retained {
			return root
		}
	}
	return ObjectID{}
}

// rotateDocumentSlots makes root's retained trees and native sources the
// active document slots, stashing the previously active document. Capture
// calls this on the GLib thread once the capture root is known, before
// preparing the incremental-refresh cache.
func (adapter *Adapter) rotateDocumentSlots(root ObjectID) {
	adapter.rotateDocumentSlotsAndRelease(root, releaseDocumentSources)
}

func releaseDocumentSources(document stashedDocument) {
	for _, source := range document.sources {
		C.g_object_unref(C.gpointer(source))
	}
}

// libatspi disposal synchronously emits defunct events. Publish the new slots
// and unlock before releasing references, so reentrant invalidation sees a
// consistent cache and can acquire treeMutex.
func (adapter *Adapter) rotateDocumentSlotsAndRelease(root ObjectID, release func(stashedDocument)) {
	if !root.Valid() {
		return
	}
	var retired []stashedDocument
	adapter.treeMutex.Lock()
	defer func() {
		adapter.treeMutex.Unlock()
		for _, document := range retired {
			release(document)
		}
	}()
	if root == adapter.documentSlotRoot {
		return
	}
	// Remove the requested slot before stashing the active one: at capacity,
	// stashing first could evict the very document we are returning to.
	stashed := adapter.stashedDocuments[root]
	delete(adapter.stashedDocuments, root)
	for index, id := range adapter.stashedDocumentIDs {
		if id == root {
			adapter.stashedDocumentIDs = append(adapter.stashedDocumentIDs[:index], adapter.stashedDocumentIDs[index+1:]...)
			break
		}
	}
	if adapter.documentSlotRoot.Valid() &&
		(adapter.documentTree != nil || adapter.documentTextTree != nil) {
		retired = adapter.stashDocumentLocked(adapter.documentSlotRoot, stashedDocument{
			tree: adapter.documentTree, textTree: adapter.documentTextTree,
			sources: adapter.nativeDocument,
		})
	} else if len(adapter.nativeDocument) != 0 {
		retired = append(retired, stashedDocument{sources: adapter.nativeDocument})
	}
	adapter.documentTree = stashed.tree
	adapter.documentTextTree = stashed.textTree
	adapter.nativeDocument = stashed.sources
	adapter.documentSlotRoot = root
}

func (adapter *Adapter) stashDocumentLocked(root ObjectID, document stashedDocument) []stashedDocument {
	var retired []stashedDocument
	if adapter.stashedDocuments == nil {
		adapter.stashedDocuments = make(map[ObjectID]stashedDocument)
	}
	if old, ok := adapter.stashedDocuments[root]; ok {
		retired = append(retired, old)
		for index, id := range adapter.stashedDocumentIDs {
			if id == root {
				adapter.stashedDocumentIDs = append(adapter.stashedDocumentIDs[:index], adapter.stashedDocumentIDs[index+1:]...)
				break
			}
		}
	}
	adapter.stashedDocuments[root] = document
	adapter.stashedDocumentIDs = append(adapter.stashedDocumentIDs, root)
	for len(adapter.stashedDocumentIDs) > maxStashedDocuments {
		oldest := adapter.stashedDocumentIDs[0]
		retired = append(retired, adapter.stashedDocuments[oldest])
		delete(adapter.stashedDocuments, oldest)
		adapter.stashedDocumentIDs = adapter.stashedDocumentIDs[1:]
	}
	return retired
}

// clearStashedDocuments releases every stashed document's native sources.
// Callers run on the GLib thread (secure reset, shutdown).
func (adapter *Adapter) clearStashedDocuments() {
	adapter.treeMutex.Lock()
	stashed := adapter.stashedDocuments
	adapter.stashedDocuments = nil
	adapter.stashedDocumentIDs = nil
	adapter.documentSlotRoot = ObjectID{}
	adapter.treeMutex.Unlock()
	for _, document := range stashed {
		for _, source := range document.sources {
			C.g_object_unref(C.gpointer(source))
		}
	}
}

func (adapter *Adapter) ownedTrees() []*AccessibleTree {
	adapter.treeMutex.Lock()
	defer adapter.treeMutex.Unlock()
	return adapter.ownedTreesLocked()
}

func (adapter *Adapter) ownedTreesLocked() []*AccessibleTree {
	trees := make([]*AccessibleTree, 0, 3+2*len(adapter.stashedDocuments))
	for _, tree := range []*AccessibleTree{adapter.tree, adapter.documentTree, adapter.documentTextTree} {
		if tree != nil {
			trees = append(trees, tree)
		}
	}
	for _, id := range adapter.stashedDocumentIDs {
		stashed := adapter.stashedDocuments[id]
		if stashed.tree != nil {
			trees = append(trees, stashed.tree)
		}
		if stashed.textTree != nil {
			trees = append(trees, stashed.textTree)
		}
	}
	return trees
}

func (adapter *Adapter) installCapturedTree(root ObjectID, nodes []TreeNode, document, documentText bool) (*AccessibleTree, error) {
	adapter.treeMutex.Lock()
	defer adapter.treeMutex.Unlock()
	owned := &adapter.tree
	if documentText {
		owned = &adapter.documentTextTree
	} else if document {
		owned = &adapter.documentTree
	}
	if *owned == nil {
		tree, err := NewAccessibleTree(root, nodes)
		if err != nil {
			return nil, err
		}
		*owned = tree
		return tree, nil
	}
	if err := (*owned).Replace(root, nodes); err != nil {
		return nil, err
	}
	return *owned, nil
}

func (adapter *Adapter) invalidateTree() {
	adapter.treeMutex.Lock()
	defer adapter.treeMutex.Unlock()
	for _, tree := range adapter.ownedTreesLocked() {
		root, err := tree.Root()
		if err == nil {
			adapter.treeInvalidations.Add(uint64(tree.Invalidate(root.ID())))
		}
	}
}