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

package app

import (
	"strings"

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

// Inline completions are selected by the browser. Echo the inserted portion
// outside that selection; it contains the user's edit, not the suggested suffix.
func autocompleteInsertion(event atspi.Event) string {
	text := []rune(event.Payload)
	start, end := event.Source.SelectionStart, event.Source.SelectionEnd
	if end <= start || end <= event.Detail1 || start >= event.Detail1+len(text) {
		return event.Payload
	}
	left := max(0, start-event.Detail1)
	right := min(len(text), end-event.Detail1)
	return string(text[:left]) + string(text[right:])
}

func recentInput(source any) input.Activity {
	if provider, ok := source.(interface{ RecentInput() input.Activity }); ok {
		return provider.RecentInput()
	}
	return input.Activity{}
}

type autocompleteEcho struct {
	sequence uint64
	source   atspi.ObjectID
}

// autocompleteAvailability presents the selected address when it changes.
// Chromium can send several insertion and popup events for the same suggestion.
type autocompleteAvailability struct {
	entry       atspi.ObjectID
	lastAddress string
}

func supportsAutocomplete(snapshot atspi.Snapshot) bool {
	return snapshot.Autocomplete || snapshot.Role == "autocomplete"
}

func (availability *autocompleteAvailability) focus(event atspi.Event) {
	if !isFocusGainEvent(event) || event.Source.AutocompletePopup {
		return
	}
	entry := atspi.ObjectID{}
	if supportsAutocomplete(event.Source) {
		entry = event.Source.ID()
	}
	if entry != availability.entry {
		availability.entry = entry
		availability.lastAddress = ""
	}
}

func (availability *autocompleteAvailability) offered(event atspi.Event, activity input.Activity) string {
	if !availability.entry.Valid() || event.Type != atspi.TextInsertedEvent ||
		!supportsAutocomplete(event.Source) || event.Source.ID() != availability.entry ||
		(activity.Intent != input.TypingIntent && activity.Intent != input.DeleteIntent) {
		return ""
	}
	address := strings.TrimSpace(event.Source.Text)
	if event.Source.SelectionEnd <= event.Source.SelectionStart ||
		event.Source.SelectionEnd > len([]rune(address)) || address == "" ||
		address == availability.lastAddress {
		return ""
	}
	availability.lastAddress = address
	return address
}

func (echo *autocompleteEcho) insertion(event atspi.Event, activity input.Activity) string {
	text := autocompleteInsertion(event)
	if text == "" && activity.Sequence != 0 &&
		(activity.Sequence != echo.sequence || event.Source.ID() != echo.source) &&
		event.Detail1 == event.Source.SelectionStart {
		// Chromium can retain an unchanged typed prefix and emit only a replacement
		// of the selected suffix. Recover that character from accessible text once
		// for this key press; a normal insertion already covers the other case.
		text = event.Source.CompletionPrefixCharacter
	}
	if text != "" {
		echo.sequence, echo.source = activity.Sequence, event.Source.ID()
	}
	return text
}