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

package review

import (
	"context"

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

// DocumentCaretCommand follows Python Cthulhu's browse caret key families.
type DocumentCaretCommand uint8

const (
	CaretNextCharacter DocumentCaretCommand = iota + 1
	CaretPreviousCharacter
	CaretNextWord
	CaretPreviousWord
	CaretNextLine
	CaretPreviousLine
	CaretLineStart
	CaretLineEnd
	CaretDocumentStart
	CaretDocumentEnd
	CaretReadLine
	TableLeft
	TableRight
	TableUp
	TableDown
	TableFirst
	TableLast
)

func (command DocumentCaretCommand) valid() bool {
	return command >= CaretNextCharacter && command <= TableLast
}

func (command DocumentCaretCommand) String() string {
	names := [...]string{"invalid", "next-character", "previous-character",
		"next-word", "previous-word", "next-line", "previous-line", "line-start",
		"line-end", "document-start", "document-end", "read-line", "table-left",
		"table-right", "table-up", "table-down", "table-first", "table-last"}
	if !command.valid() {
		return names[0]
	}
	return names[command]
}

type DocumentCaretReader interface {
	ReadDocumentCaret(context.Context, atspi.ObjectReference, int, atspi.DocumentCaretUnit) (atspi.DocumentCaretText, error)
}

type DocumentCaretMove struct {
	Position   DocumentPosition
	Text       string
	RawText    string
	Misspelled bool
	// Line retains each object's native range for an assembled visual line.
	Line                     *atspi.DocumentLine
	TablePrefix, TableSuffix string

	TableRowHeader, TableColumnHeader string

	Moved bool
	// Native text range used for this move, in Unicode character offsets.
	Start, End int
}

// MoveCaret advances the independent browse position using AT-SPI text units.
// It does not depend on Chromium's retained native caret. A stale captured
// document is reported to the worker for one bounded refresh.
func (cursor *DocumentCursor) MoveCaret(ctx context.Context, reader DocumentCaretReader, command DocumentCaretCommand) (DocumentCaretMove, error) {
	if !command.valid() || reader == nil {
		return DocumentCaretMove{}, ErrInvalidDirection
	}
	cursor.mu.Lock()
	defer cursor.mu.Unlock()
	if !cursor.active.Valid() || len(cursor.places) == 0 {
		return DocumentCaretMove{}, ErrNoCurrent
	}
	place := &cursor.places[len(cursor.places)-1]
	doc, err := cursor.tree.Document(ctx, place.object)
	if err != nil {
		return DocumentCaretMove{}, err
	}
	if doc.Context.TopLevel != place.document {
		return DocumentCaretMove{}, atspi.ErrStaleObject
	}
	if command >= TableLeft {
		return cursor.moveTable(ctx, doc, place, command)
	}
	place.tableCell = atspi.ObjectID{}
	_, current := caret_node_indices(doc.Nodes, place.object)
	indices := caretNodeRanges(doc.Nodes)
	if current < 0 {
		return DocumentCaretMove{}, atspi.ErrStaleObject
	}
	if len(indices) == 0 {
		return DocumentCaretMove{Position: documentPosition(doc, *place)}, nil
	}
	switch command {
	case CaretNextWord, CaretPreviousWord, CaretNextCharacter, CaretPreviousCharacter:
		return moveCaretText(ctx, reader, doc, place, indices, current,
			command == CaretPreviousWord || command == CaretPreviousCharacter,
			command == CaretNextWord || command == CaretPreviousWord)
	}
	return move_caret_line(ctx, reader, cursor.tree, doc, place, indices, current, command)
}