package atspi

import (
	"strings"
	"unicode/utf8"
)

// DocumentCaretUnit selects the AT-SPI text granularity for virtual browsing.
type DocumentCaretUnit uint8

const (
	DocumentCaretCharacter DocumentCaretUnit = iota + 1
	DocumentCaretWord
	DocumentCaretLine
	DocumentCaretLineRemainder
	// DocumentCaretBrailleLine preserves native spacing for display offsets.
	DocumentCaretBrailleLine
	// DocumentCaretCharacters returns a bounded block of raw characters for
	// whitespace traversal. It does not normalize spaces or query line geometry.
	DocumentCaretCharacters
)

func (unit DocumentCaretUnit) Valid() bool {
	return unit >= DocumentCaretCharacter && unit <= DocumentCaretCharacters
}

type DocumentCaretText struct {
	TextAttributeRuns []TextAttributeRun
	Start             int
	End               int
	Text              string
	RawText           string
	Misspelled        bool
	// Expanded reports that embedded-object placeholders in Text were
	// replaced by their descendant text. Start, End, selections, attribute
	// runs, and RawText still describe the unexpanded native line, so
	// native offsets no longer map one-to-one into Text.
	Expanded                     bool
	CharacterCount               int
	SelectionStart, SelectionEnd int
	// Bounds describe this native line, including offscreen document text.
	Bounds Rectangle
}

func (line *DocumentCaretText) applyExpandedText(expanded, name string, incomplete bool) {
	line.RawText = line.Text
	// An accessible name describes the whole object. It can recover a failed
	// descendant read only when this range covers that entire object; using it
	// on a wrapped line would repeat unrelated text and move the reading point.
	if incomplete && line.CharacterCount > 0 && line.Start == 0 && line.End == line.CharacterCount &&
		strings.TrimSpace(name) != "" && !strings.ContainsRune(name, '\ufffc') {
		expanded = name
	}
	line.Text, line.Expanded = expanded, expanded != line.RawText
}

func (snapshot *Snapshot) applyDocumentCaretLine(line DocumentCaretText, offset int) {
	// A caret capture already expanded this exact native line. Preserve that
	// text instead of replacing it with the raw line used for offset repair.
	if snapshot.BrailleLine != line.RawText || snapshot.BrailleLineStart != line.Start || snapshot.CharacterCount != line.CharacterCount {
		snapshot.Text = sanitizeSnapshotField(line.Text)
	}
	snapshot.BrailleLine, snapshot.BrailleLineStart, snapshot.BrailleCaret = line.RawText, line.Start, offset
	snapshot.CharacterCount = line.CharacterCount
}

func documentCaretCharacter(value string) string {
	if value == "" {
		return ""
	}
	character, _ := utf8.DecodeRuneInString(value)
	return string(character)
}