// 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 (
	"strings"
	"time"
	"unicode"
	"unicode/utf8"

	"git.stormux.org/storm/cthulhu/internal/webscripts"
)

const maxSnapshotFieldLength = 4096

type Snapshot struct {
	TextAttributeRun  TextAttributeRun
	TextAttributeRuns []TextAttributeRun
	Mnemonic          string
	Misspelled        bool
	SpeechContext     []Snapshot // Bounded copied ancestor metadata, without native handles.
	BrailleContext    []Snapshot // Nearest ancestor first, including window/application.
	Spreadsheet       bool
	LibreOffice       *LibreOfficeContext
	// BrowserTab identifies browser chrome, excluding page-authored tab widgets.
	BrowserTab bool
	// ExplicitName distinguishes an author-supplied link label from a name
	// derived from descendants. Only the former makes a link one browse stop.
	ExplicitName bool
	// Autocomplete describes a single-line completion entry. Popup ownership
	// comes from the native POPUP_FOR relation, not a control's name.
	Autocomplete, AutocompletePopup bool
	SupportsClick                   bool
	LiveRegion                      bool
	LivePoliteness                  string
	LiveAtomic                      bool
	LayoutTable                     bool
	// ChildCount is copied only for list containers. A failed provider query
	// leaves ChildCountKnown false so zero is not mistaken for an empty list.
	ChildCount      int
	ChildCountKnown bool

	TableRowCount                       int
	TableColumnCount                    int
	TableName                           string
	TablePath                           string
	TableRowIndex                       int
	TableColumnIndex                    int
	TablePositionKnown                  bool
	TableRowSpan, TableColumnSpan       int
	TableRowHeaders, TableColumnHeaders string
	TableRowText                        string
	GUITable                            bool
	CharacterCount                      int
	EmbeddedObjectCount                 int
	// TextChildren maps embedded-object characters to native child offsets.
	// Captured for hypertext containers; nil leaves ordinary leaf traversal.
	TextChildren []TextChild
	// Selection offsets are captured for text-bearing focused events.
	SelectionStart, SelectionEnd int
	SelectionText                string
	CompletionPrefixCharacter    string
	// CaretWord is captured only for caret movement, not tree traversal.
	CaretWord string
	// StatesKnown reports whether native capture returned a state set.
	// A missing set must not be interpreted as known non-focusable content.
	Visible, Showing bool
	StatesKnown      bool
	Active           bool
	Focusable        bool
	Focused          bool
	HasPopup         bool
	HeadingLevel     int
	Checked          bool
	Defunct          bool
	Editable         bool
	Expandable       bool
	Expanded         bool
	Indeterminate    bool
	Invalid          bool
	Multiselectable  bool
	ReadOnly         bool
	Required         bool
	Selected         bool
	Sensitive        bool
	SensitiveKnown   bool
	ValueKnown       bool
	Visited          bool
	CurrentValue     float64
	MaximumValue     float64
	MinimumValue     float64
	MinimumIncrement float64
	BusName          string
	Path             string
	Name             string
	Role             string
	RadioGroupName   string
	Description      string
	Text             string
	// BrailleLine preserves the captured line's spacing; Text is normalized
	// for speech and cannot locate a cursor after repeated spaces.
	BrailleLine string
	// Absolute Unicode offsets, before speech normalization.
	BrailleLineStart int
	BrailleCaret     int
	CaretCharacter   string
	TextBeforeCaret  string
	TextCaretKnown   bool
	ValueText        string
	ApplicationName  string
	// ApplicationProcess is resolved from the provider PID, not page content.
	ApplicationProcess string
	// ToolkitName is captured for name-change events to select web policy
	// even before document focus or an address-bar event has arrived.
	ToolkitName string
	XMLRoles    string
	HTMLTag     string
	ElementID   string

	// PositionInSet is one-based; zero means unavailable. SetSize must be
	// positive and at least PositionInSet before presentation uses it.
	PositionInSet, SetSize int

	// SoundGeometry contains immutable screen geometry copied on the AT-SPI
	// event-loop thread. Presentation and audio workers never retain or query
	// the native accessibles from which it was derived.
	SoundGeometry SoundGeometry
}

// TextChild is a single embedded-object character in an owned text container.
// Its offset belongs to the parent; Child retains no native handle.
type TextChild struct {
	Offset int
	Child  ObjectID
}

// TextAttributeRun is the native attribute range at the caret, copied without
// retaining an AT-SPI object. Offsets are Unicode character offsets.
type TextAttributeRun struct {
	Start, End int
	Values     map[string]string
}

func captureBrailleLine(snapshot *Snapshot, text, beforeCaret string, start int) {
	snapshot.BrailleLine = sanitizeTextContext(text)
	// sanitizeTextContext retains a bounded suffix. Retain its source origin,
	// and hide a caret which is outside that suffix rather than misrouting it.
	snapshot.BrailleLineStart = start + utf8.RuneCountInString(text) - utf8.RuneCountInString(snapshot.BrailleLine)
	snapshot.BrailleCaret = start + utf8.RuneCountInString(beforeCaret)
}

type SoundGeometry struct {
	Object, Reference Rectangle
	ObjectKnown       bool
	ReferenceKnown    bool
}

// ObjectID identifies one accessible for the lifetime of its AT-SPI bus
// connection. Object paths alone are not unique because different
// applications can publish the same path.
type ObjectID struct {
	BusName string
	Path    string
}

func NewObjectID(busName, path string) ObjectID {
	return ObjectID{
		BusName: sanitizeSnapshotField(busName),
		Path:    sanitizeSnapshotField(path),
	}
}

func (id ObjectID) Valid() bool {
	return id.BusName != "" && id.Path != "" &&
		validBusName(id.BusName) && validObjectPath(id.Path) &&
		id == NewObjectID(id.BusName, id.Path)
}

func validBusName(name string) bool {
	if len(name) > 255 {
		return false
	}
	unique := strings.HasPrefix(name, ":")
	if unique {
		name = strings.TrimPrefix(name, ":")
	}
	parts := strings.Split(name, ".")
	if len(parts) < 2 {
		return false
	}
	for _, part := range parts {
		if part == "" {
			return false
		}
		for index, character := range []byte(part) {
			letter := character >= 'A' && character <= 'Z' || character >= 'a' && character <= 'z'
			digit := character >= '0' && character <= '9'
			if !letter && !digit && character != '_' && character != '-' {
				return false
			}
			if index == 0 && !unique && digit {
				return false
			}
		}
	}
	return true
}

func validObjectPath(path string) bool {
	if path == "/" {
		return true
	}
	if !strings.HasPrefix(path, "/") || strings.HasSuffix(path, "/") {
		return false
	}
	for _, part := range strings.Split(path[1:], "/") {
		if part == "" {
			return false
		}
		for _, character := range []byte(part) {
			letter := character >= 'A' && character <= 'Z' || character >= 'a' && character <= 'z'
			digit := character >= '0' && character <= '9'
			if !letter && !digit && character != '_' {
				return false
			}
		}
	}
	return true
}

func (snapshot Snapshot) ID() ObjectID {
	return ObjectID{BusName: snapshot.BusName, Path: snapshot.Path}
}

type Event struct {
	// WebNotification is selected on the native owner before background-event
	// filtering. It contains copied content and no retained native references.
	WebNotification    *webscripts.Notification
	Foreground         ForegroundState
	ForegroundMismatch bool
	// ForegroundCheck contains numeric, text-free diagnostics for rejected
	// window activations. Other events leave it empty.
	ForegroundCheck ForegroundCheck
	// PopupFor is the autocomplete entry named by the popup's AT-SPI relation.
	PopupFor ObjectID

	// FocusOutsideDocument is a freshly verified chrome focus at load
	// completion. A page loading behind it must not acquire browse keys.
	FocusOutsideDocument ObjectID
	// DocumentFragment is the URL fragment of a completed web document load.
	DocumentFragment string
	// Window identifies the nearest dialog/window/frame which owns Source.
	// It is captured from the original event source before activation may be
	// redirected to a focused descendant.
	Window ObjectID
	// WindowRecovered reports an owned frame restored after a browser tab
	// temporarily detached its document's AT-SPI parent chain.
	WindowRecovered bool
	// WindowTitle is the top-level AT-SPI name captured on activation, even
	// when Source is the focused descendant.
	WindowTitle string
	// WindowDescription is the top-level accessible description on activation.
	WindowDescription string
	// WindowMessage is a simple frame prompt recovered when its first button
	// takes focus after activation arrived before the label was available.
	WindowMessage    string
	NavigationEcho   bool
	SnapshotDuration time.Duration
	Type             string
	// NativeType retains an AT-SPI text-change origin suffix for debug logs.
	// Presentation policies use the canonical Type.
	NativeType string
	Source     Snapshot
	OriginPath string
	Payload    string
	Detail1    int
}

type ForegroundCheck struct {
	Reason        string
	AccessiblePID int
	Active        bool
	Showing       bool
	Iconified     bool
	Bounds        Rectangle
}

func NewSnapshot(path, name, role, description, text string) Snapshot {
	return NewSnapshotWithCaretCharacter(path, name, role, description, text, "")
}

func NewSnapshotWithCaretCharacter(path, name, role, description, text, caretCharacter string) Snapshot {
	return Snapshot{
		Path:           sanitizeSnapshotField(path),
		Name:           sanitizeSnapshotField(name),
		Role:           sanitizeSnapshotField(role),
		Description:    sanitizeSnapshotField(description),
		Text:           sanitizeSnapshotField(text),
		CaretCharacter: sanitizeCaretCharacter(caretCharacter),
	}
}

func NewEvent(eventType string, source Snapshot) Event {
	eventType = sanitizeSnapshotField(eventType)
	event := Event{Type: canonicalTextChangeEventType(eventType), Source: source, OriginPath: source.Path}
	if event.Type != eventType {
		event.NativeType = eventType
	}
	return event
}

// AT-SPI appends an origin to some text mutations (for example, :system).
// The reader handles those mutations by kind; leaving the suffix on Type
// makes them fall through as ordinary object presentation events.
func canonicalTextChangeEventType(eventType string) string {
	for _, kind := range []string{TextInsertedEvent, TextDeletedEvent} {
		if eventType == kind || strings.HasPrefix(eventType, kind+":") {
			return kind
		}
	}
	return eventType
}

func isBrowserChromeTab(snapshot Snapshot, inDocument bool) bool {
	if snapshot.Role != "page tab" || inDocument {
		return false
	}
	switch strings.ToLower(snapshot.ToolkitName) {
	case "chromium", "gecko", "webkit", "webkitgtk":
		return true
	}
	return false
}

// Firefox exposes its address bar as an editable popup combo box without the
// supports-autocompletion state used by Chromium. Keep the fallback in chrome:
// page controls with the same role still use their own document behavior.
func isFirefoxChromeAutocomplete(snapshot Snapshot, inDocument bool) bool {
	return !inDocument && strings.EqualFold(snapshot.ApplicationProcess, "firefox") &&
		snapshot.Role == "combo box" && snapshot.Editable && !snapshot.ReadOnly && snapshot.HasPopup
}

func NewManagedDescendantEvent(eventType, originPath string, source Snapshot) Event {
	event := NewEvent(eventType, source)
	event.OriginPath = sanitizeSnapshotField(originPath)
	return event
}

func NewEventWithPayload(eventType string, source Snapshot, payload string) Event {
	event := NewEvent(eventType, source)
	event.Payload = sanitizeTextPayload(payload)
	return event
}

func sanitizeTextPayload(value string) string {
	// Preserve single-character delimiters so typing-echo policy can
	// distinguish space, tab, and line boundaries. Other snapshot fields
	// continue to trim surrounding whitespace.
	switch value {
	case " ", "\t", "\n":
		return value
	case "\r", "\r\n":
		return "\n"
	}
	return sanitizeSnapshotField(value)
}

func sanitizeTextContext(value string) string {
	value = strings.ToValidUTF8(value, "�")
	value = strings.Map(func(character rune) rune {
		if character == '\r' {
			return '\n'
		}
		if character != '\n' && character != '\t' && unicode.IsControl(character) {
			return '�'
		}
		return character
	}, value)
	if len(value) > maxSnapshotFieldLength {
		value = value[len(value)-maxSnapshotFieldLength:]
		for !utf8.ValidString(value) {
			value = value[1:]
		}
	}
	return value
}

func sanitizeSnapshotField(value string) string {
	value = strings.ToValidUTF8(value, "�")
	value = strings.Map(func(character rune) rune {
		if character == '\n' || character == '\r' || character == '\t' {
			return ' '
		}
		return character
	}, value)
	value = strings.Join(strings.Fields(value), " ")
	value = strings.TrimSpace(value)
	if len(value) > maxSnapshotFieldLength {
		value = value[:maxSnapshotFieldLength]
		for !utf8.ValidString(value) {
			value = value[:len(value)-1]
		}
	}
	return value
}

func sanitizeCaretCharacter(value string) string {
	value = strings.ToValidUTF8(value, "�")
	characters := []rune(value)
	if len(characters) == 0 {
		return ""
	}
	switch characters[0] {
	case '\n', '\r':
		return "blank"
	default:
		return string(characters[0])
	}
}