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

package app

import (
	"slices"
	"strings"

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

// Owned by the event loop, with one bounded snapshot for the focused sheet.
// Retired on sheet/application focus changes and the ordinary focus reset
// (including lock, destruction, foreground loss, and shutdown). No timers or
// provider references survive a selection event.
type libreOfficeSelectionState struct {
	sheet    atspi.ObjectID
	previous *atspi.LibreOfficeSelection
}

func calcSheet(snapshot atspi.Snapshot) atspi.ObjectID {
	if !atspi.IsLibreOfficeProcess(snapshot.ApplicationProcess) || snapshot.LibreOffice == nil || !snapshot.LibreOffice.InSpreadsheet {
		return atspi.ObjectID{}
	}
	if snapshot.Role == "table" {
		return snapshot.ID()
	}
	if snapshot.LibreOffice.Cell {
		return atspi.NewObjectID(snapshot.BusName, snapshot.TablePath)
	}
	return atspi.ObjectID{}
}

func (handler *accessibilityEventHandler) handleLibreOfficeSelection(event atspi.Event) {
	state := handler.state
	if isFocusGainEvent(event) && state.libreOfficeSelection.sheet != calcSheet(event.Source) {
		state.libreOfficeSelection = libreOfficeSelectionState{}
	}
	context := event.Source.LibreOffice
	if event.Type != atspi.SelectionChangedEvent || context == nil || context.Selection == nil ||
		event.Source.Role != "table" || event.Source.Defunct || !context.InSpreadsheet ||
		!atspi.IsLibreOfficeProcess(event.Source.ApplicationProcess) ||
		handler.focusGate.Suspended() || !state.owner.window.Valid() ||
		state.owner.window != eventWindow(event) || state.owner.applicationBus != event.Source.BusName ||
		calcSheet(state.current) != event.Source.ID() {
		return
	}
	history := &state.libreOfficeSelection
	if history.sheet != event.Source.ID() {
		*history = libreOfficeSelectionState{sheet: event.Source.ID()}
	}
	selection := context.Selection
	handler.logger.Debug("received Calc selection snapshot", "kind", selection.Kind,
		"count", selection.Count, "count_limited", selection.CountLimited,
		"complete", selection.Complete, "cells", selection.Cells,
		"first", selection.First, "last", selection.Last)
	previous := history.previous
	history.previous = selection
	if previous != nil && previous.Kind == selection.Kind && previous.Count == selection.Count &&
		previous.CountLimited == selection.CountLimited && previous.Complete == selection.Complete &&
		previous.First == selection.First && previous.Last == selection.Last && slices.Equal(previous.Cells, selection.Cells) {
		return
	}
	reading := state.presentationOptions.Reading
	if handler.live != nil {
		settings := handler.live.Load()
		reading = &settings.Reading
	}
	if reading != nil && reading.OnlySpeakDisplayedText {
		return
	}
	var messages []string
	if previous != nil && (previous.Count != 0 || previous.Kind == "all") {
		if selection.Count == 0 && selection.Kind != "all" {
			messages = append(messages, "Selection cleared.")
		} else if previous.Kind == selection.Kind && previous.Kind != "all" && previous.Complete && selection.Complete {
			removed := *previous
			removed.Cells = calcSelectionDifference(previous.Cells, selection.Cells)
			removed.Count = len(removed.Cells)
			if text := presentation.LibreOfficeSelectionText(removed, "unselected"); text != "" {
				messages = append(messages, text)
			}
		}
	}
	added := *selection
	if selection.Complete && (selection.Kind == "cells" || previous != nil && previous.Kind == selection.Kind) {
		if previous != nil && previous.Complete && previous.Kind == selection.Kind {
			added.Cells = calcSelectionDifference(selection.Cells, previous.Cells)
		}
		if selection.Kind == "cells" && state.current.TablePositionKnown {
			// Orca leaves the anchor to ordinary active-cell presentation.
			anchor := atspi.LibreOfficeCell{Row: state.current.TableRowIndex, Column: state.current.TableColumnIndex}
			added.Cells = calcSelectionDifference(added.Cells, []atspi.LibreOfficeCell{anchor})
		}
		added.Count = len(added.Cells)
	}
	if text := presentation.LibreOfficeSelectionText(added, "selected"); text != "" {
		messages = append(messages, text)
	}
	if text := strings.Join(messages, " "); text != "" {
		state.pending.clear()
		handler.speech.Interrupt()
		handler.speech.Enqueue(speechRequest{Text: text, Role: "system", Cause: "calc-selection"})
	}
}

func calcSelectionDifference(first, second []atspi.LibreOfficeCell) []atspi.LibreOfficeCell {
	var result []atspi.LibreOfficeCell
	for _, cell := range first {
		if !slices.Contains(second, cell) {
			result = append(result, cell)
		}
	}
	return result
}