penpot/render-wasm/src/state/text_editor.rs

#![allow(dead_code)]

use macros::ToJs;

use crate::shapes::{
    Fill, FontStyle, TextAlign, TextContent, TextDecoration, TextDirection,
    TextPositionWithAffinity, TextTransform, VerticalAlign,
};
use crate::uuid::Uuid;
use crate::wasm::text::helpers::{self as text_helpers, find_text_span_at_offset};
use crate::wasm::text_editor::CursorDirection;
use skia_safe::Color;

#[derive(Debug, Clone, Copy, Default)]
pub struct TextSelection {
    pub anchor: TextPositionWithAffinity,
    pub focus: TextPositionWithAffinity,
}

impl TextSelection {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn from_position_with_affinity(position: TextPositionWithAffinity) -> Self {
        Self {
            anchor: position,
            focus: position,
        }
    }

    pub fn is_collapsed(&self) -> bool {
        self.anchor == self.focus
    }

    pub fn is_selection(&self) -> bool {
        !self.is_collapsed()
    }

    pub fn reset(&mut self) {
        self.anchor.reset();
        self.focus.reset();
    }

    pub fn set_caret(&mut self, cursor: TextPositionWithAffinity) {
        self.anchor = cursor;
        self.focus = cursor;
    }

    pub fn extend_to(&mut self, cursor: TextPositionWithAffinity) {
        self.focus = cursor;
    }

    pub fn collapse_to_focus(&mut self) {
        self.anchor = self.focus;
    }

    pub fn collapse_to_anchor(&mut self) {
        self.focus = self.anchor;
    }

    pub fn start(&self) -> TextPositionWithAffinity {
        if self.anchor.paragraph < self.focus.paragraph {
            self.anchor
        } else if self.anchor.paragraph > self.focus.paragraph {
            self.focus
        } else if self.anchor.offset <= self.focus.offset {
            self.anchor
        } else {
            self.focus
        }
    }

    pub fn end(&self) -> TextPositionWithAffinity {
        if self.anchor.paragraph > self.focus.paragraph {
            self.anchor
        } else if self.anchor.paragraph < self.focus.paragraph {
            self.focus
        } else if self.anchor.offset >= self.focus.offset {
            self.anchor
        } else {
            self.focus
        }
    }
}

/// Events that the text editor can emit for frontend synchronization
/// FIXME: the serialization should be in the wasm module
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, ToJs)]
pub enum TextEditorEvent {
    None = 0,
    ContentChanged = 1,
    SelectionChanged = 2,
    StylesChanged = 3,
    NeedsLayout = 4,
}

/// FIXME: It should be better to get these constants from the frontend through the API.
const SELECTION_COLOR: Color = Color::from_argb(127, 0, 209, 184);
const CURSOR_COLOR: Color = Color::WHITE;
const CURSOR_WIDTH: f32 = 1.0;
const CURSOR_BLINK_INTERVAL_MS: f32 = 530.0;

#[derive(Debug)]
pub struct TextEditorStyles {
    pub vertical_align: VerticalAlign,
    pub text_align: Multiple<TextAlign>,         // Multiple
    pub text_direction: Multiple<TextDirection>, // Multiple
    pub text_decoration: Multiple<TextDecoration>,
    pub text_transform: Multiple<TextTransform>,
    // The font family is decomposed into its independent parts so the family
    // dropdown shows a single family even when the selection mixes variants of
    // the same family (e.g. regular + bold italic). The id identifies the
    // family; weight is tracked by `font_weight`; only the style is left here.
    pub font_family_id: Multiple<Uuid>,
    pub font_style: Multiple<FontStyle>,
    pub font_size: Multiple<f32>,
    pub font_weight: Multiple<i32>,
    pub font_variant_id: Multiple<Uuid>,
    pub line_height: Multiple<f32>,
    pub letter_spacing: Multiple<f32>,
    pub fills_are_multiple: bool,
    pub fills: Vec<Fill>,
}

// FIXME: the serialization should be in the wasm module
#[derive(Debug, Clone, Copy, PartialEq, ToJs)]
#[repr(u8)]
pub enum MultipleState {
    Undefined = 0,
    Single = 1,
    Multiple = 2,
}

#[derive(Debug)]
pub struct Multiple<T> {
    state: MultipleState,
    value: Option<T>,
}

impl<T> Multiple<T> {
    pub fn empty() -> Self {
        Self {
            state: MultipleState::Undefined,
            value: None,
        }
    }

    pub fn new(state: MultipleState, value: Option<T>) -> Self {
        Self { state, value }
    }

    pub fn state(&self) -> &MultipleState {
        &self.state
    }

    pub fn value(&self) -> &Option<T> {
        &self.value
    }

    pub fn is_undefined(&self) -> bool {
        self.state == MultipleState::Undefined
    }

    pub fn is_multiple(&self) -> bool {
        self.state == MultipleState::Multiple
    }

    pub fn is_single(&self) -> bool {
        self.state == MultipleState::Single
    }

    pub fn is_single_some(&self) -> bool {
        !self.is_undefined() && self.value.is_some()
    }

    pub fn is_single_none(&self) -> bool {
        !self.is_undefined() && self.value.is_none()
    }

    pub fn reset(&mut self) {
        self.state = MultipleState::Undefined;
        self.value = None;
    }

    pub fn set(&mut self, value: Option<T>) {
        if self.state == MultipleState::Undefined || self.state == MultipleState::Multiple {
            self.state = MultipleState::Single;
        }
        self.value = value;
    }

    pub fn set_single(&mut self, value: Option<T>) {
        self.state = MultipleState::Single;
        self.value = value;
    }

    pub fn set_multiple(&mut self) {
        self.state = MultipleState::Multiple;
        self.value = None;
    }

    pub fn merge(&mut self, value: Option<T>) -> bool
    where
        T: PartialEq,
    {
        if self.state == MultipleState::Multiple {
            return false;
        }

        if self.state == MultipleState::Undefined {
            self.set_single(value);
            return true;
        }

        if self.value.as_ref() != value.as_ref() {
            self.set_multiple();
            return false;
        }

        self.value = value;
        true
    }
}

impl TextEditorStyles {
    pub fn new() -> Self {
        Self {
            vertical_align: VerticalAlign::Top,
            text_align: Multiple::empty(),
            text_direction: Multiple::empty(),
            text_decoration: Multiple::empty(),
            text_transform: Multiple::empty(),
            font_family_id: Multiple::empty(),
            font_style: Multiple::empty(),
            font_size: Multiple::empty(),
            font_weight: Multiple::empty(),
            font_variant_id: Multiple::empty(),
            line_height: Multiple::empty(),
            letter_spacing: Multiple::empty(),
            fills_are_multiple: false,
            fills: Vec::new(),
        }
    }

    pub fn reset(&mut self) {
        self.text_align.reset();
        self.text_direction.reset();
        self.text_decoration.reset();
        self.text_transform.reset();
        self.font_family_id.reset();
        self.font_style.reset();
        self.font_size.reset();
        self.font_weight.reset();
        self.font_variant_id.reset();
        self.line_height.reset();
        self.letter_spacing.reset();
        self.fills_are_multiple = false;
        self.fills.clear();
    }
}

impl Default for TextEditorStyles {
    fn default() -> Self {
        Self::new()
    }
}

pub struct TextEditorTheme {
    pub selection_color: Color,
    pub cursor_color: Color,
    pub cursor_width: f32,
    /// When true the caret is painted with a Difference blend mode, so it shows
    /// as the inverted color of whatever is behind it. Used as the default when
    /// the text has no solid fill whose color the caret can match.
    pub cursor_invert: bool,
}

pub struct TextComposition {
    pub previous: String,
    pub current: String,
    pub is_composing: bool,
    /// Preview start: each update replaces `[start, start + previous]`.
    pub start: Option<TextPositionWithAffinity>,
}

impl TextComposition {
    pub fn new() -> Self {
        Self {
            previous: String::new(),
            current: String::new(),
            is_composing: false,
            start: None,
        }
    }

    pub fn start(&mut self) -> bool {
        if self.is_composing {
            return false;
        }
        self.is_composing = true;
        self.previous = String::new();
        self.current = String::new();
        self.start = None;
        true
    }

    pub fn update(&mut self, text: &str) -> bool {
        if !self.is_composing {
            self.is_composing = true;
        }
        self.previous = self.current.clone();
        self.current = text.to_owned();
        true
    }

    pub fn end(&mut self) -> bool {
        if !self.is_composing {
            return false;
        }
        self.is_composing = false;
        self.start = None;
        true
    }

    /// Range the next preview replaces: the previous preview, or `selection`
    /// (the pre-composition selection) when there is none yet.
    pub fn get_selection(&self, selection: &TextSelection) -> TextSelection {
        let Some(start) = self.start.filter(|_| !self.previous.is_empty()) else {
            return *selection;
        };

        let anchor = TextPositionWithAffinity::new_downstream_affinity(
            start.paragraph,
            start.offset + self.previous.chars().count(),
        );

        TextSelection {
            anchor,
            focus: start,
        }
    }
}

impl Default for TextComposition {
    fn default() -> Self {
        Self::new()
    }
}

pub struct TextEditorState {
    pub theme: TextEditorTheme,
    pub selection: TextSelection,
    pub composition: TextComposition,
    pub has_focus: bool,
    // This property indicates that we've started
    // selecting something with the pointer.
    pub is_pointer_selection_active: bool,
    pub is_click_event_skipped: bool,
    pub is_overtype_mode: bool,
    pub active_shape_id: Option<Uuid>,
    pub cursor_visible: bool,
    pub last_blink_time_ms: f32,
    pub current_styles: TextEditorStyles,
    pending_events: Vec<TextEditorEvent>,
}

impl TextEditorState {
    pub fn new() -> Self {
        Self {
            theme: TextEditorTheme {
                selection_color: SELECTION_COLOR,
                cursor_color: CURSOR_COLOR,
                cursor_width: CURSOR_WIDTH,
                cursor_invert: true,
            },
            selection: TextSelection::new(),
            composition: TextComposition::new(),
            has_focus: false,
            is_pointer_selection_active: false,
            is_click_event_skipped: false,
            is_overtype_mode: false,
            active_shape_id: None,
            cursor_visible: true,
            last_blink_time_ms: 0.0,
            pending_events: Vec::new(),
            current_styles: TextEditorStyles::new(),
        }
    }

    pub fn focus(&mut self, shape_id: Uuid) {
        let same_shape = self.active_shape_id == Some(shape_id);

        self.has_focus = true;
        self.active_shape_id = Some(shape_id);
        self.cursor_visible = true;
        self.last_blink_time_ms = 0.0;
        if !same_shape {
            self.selection.reset();
        }
        self.is_pointer_selection_active = false;
        self.is_overtype_mode = false;
        self.pending_events.clear();
    }

    pub fn blur(&mut self) {
        self.has_focus = false;
        // self.active_shape_id = None;
        self.cursor_visible = false;
        self.last_blink_time_ms = 0.0;
        // self.selection.reset();
        self.is_pointer_selection_active = false;
        self.is_overtype_mode = false;
        self.pending_events.clear();
    }

    pub fn dispose(&mut self) {
        self.has_focus = false;
        self.active_shape_id = None;
        self.cursor_visible = false;
        self.last_blink_time_ms = 0.0;
        self.selection.reset();
        self.is_pointer_selection_active = false;
        self.is_overtype_mode = false;
        self.pending_events.clear();
    }

    pub fn start_pointer_selection(&mut self) -> bool {
        if self.is_pointer_selection_active {
            return false;
        }
        self.is_pointer_selection_active = true;
        true
    }

    pub fn stop_pointer_selection(&mut self) -> bool {
        if !self.is_pointer_selection_active {
            return false;
        }
        self.is_pointer_selection_active = false;
        true
    }

    fn select_range(
        &mut self,
        text_content: &TextContent,
        start: &TextPositionWithAffinity,
        end: &TextPositionWithAffinity,
    ) {
        self.is_pointer_selection_active = false;
        self.is_click_event_skipped = false;
        self.set_caret_from_position(start);
        self.extend_selection_from_position(end);
        self.update_styles(text_content);
        self.reset_blink();
        self.push_event(TextEditorEvent::SelectionChanged);
    }

    pub fn select_all(&mut self, text_content: &TextContent) -> bool {
        let num_paragraphs = text_content.paragraphs().len().saturating_sub(1);
        let Some(last_paragraph) = text_content.paragraphs().last() else {
            return false;
        };
        let Some(_last_text_span) = last_paragraph.children().last() else {
            return false;
        };
        // Offsets are counted in characters, not bytes.
        let offset = text_helpers::paragraph_char_count(last_paragraph);
        self.select_range(
            text_content,
            &TextPositionWithAffinity::empty(),
            &TextPositionWithAffinity::new_upstream_affinity(num_paragraphs, offset),
        );

        true
    }

    pub fn select_word_boundary(
        &mut self,
        text_content: &TextContent,
        position: &TextPositionWithAffinity,
    ) {
        let paragraphs = text_content.paragraphs();
        if paragraphs.is_empty() || position.paragraph >= paragraphs.len() {
            return;
        }

        let paragraph = &paragraphs[position.paragraph];
        let paragraph_text: String = paragraph
            .children()
            .iter()
            .map(|span| span.text.as_str())
            .collect();

        let chars: Vec<char> = paragraph_text.chars().collect();
        if chars.is_empty() {
            self.set_caret_from_position(&TextPositionWithAffinity::new_downstream_affinity(
                position.paragraph,
                0,
            ));
            self.update_styles(text_content);
            self.reset_blink();
            self.push_event(TextEditorEvent::SelectionChanged);
            return;
        }

        let mut offset = position.offset.min(chars.len());

        if offset == chars.len() {
            offset = offset.saturating_sub(1);
        } else if !text_helpers::is_word_char(chars[offset])
            && offset > 0
            && text_helpers::is_word_char(chars[offset - 1])
        {
            offset -= 1;
        }

        if !text_helpers::is_word_char(chars[offset]) {
            self.set_caret_from_position(&TextPositionWithAffinity::new_downstream_affinity(
                position.paragraph,
                position.offset.min(chars.len()),
            ));
            self.update_styles(text_content);
            self.reset_blink();
            self.push_event(TextEditorEvent::SelectionChanged);
            return;
        }

        let mut start = offset;
        while start > 0 && text_helpers::is_word_char(chars[start - 1]) {
            start -= 1;
        }

        let mut end = offset + 1;
        while end < chars.len() && text_helpers::is_word_char(chars[end]) {
            end += 1;
        }

        self.select_range(
            text_content,
            &TextPositionWithAffinity::new_downstream_affinity(position.paragraph, start),
            &TextPositionWithAffinity::new_downstream_affinity(position.paragraph, end),
        );
    }

    pub fn select_paragraph(
        &mut self,
        text_content: &TextContent,
        position: &TextPositionWithAffinity,
    ) {
        let paragraphs = text_content.paragraphs();
        if paragraphs.is_empty() || position.paragraph >= paragraphs.len() {
            return;
        }

        // Offsets are counted in characters, not bytes.
        let offset = text_helpers::paragraph_char_count(&paragraphs[position.paragraph]);

        self.select_range(
            text_content,
            &TextPositionWithAffinity::new_downstream_affinity(position.paragraph, 0),
            &TextPositionWithAffinity::new_upstream_affinity(position.paragraph, offset),
        );
    }

    pub fn set_caret_from_position(&mut self, position: &TextPositionWithAffinity) {
        self.selection.set_caret(*position);
        // Restart the blink so the caret is solid right after it is placed,
        // instead of keeping whatever phase it had (which can toggle off at the
        // moment of the click and read as a flash). Mirrors the keyboard paths
        // (`move_cursor`, `select_all`) which already reset the blink.
        self.reset_blink();
        self.push_event(TextEditorEvent::SelectionChanged);
    }

    /// Places the caret and refreshes `current_styles` (emits `StylesChanged`).
    pub fn place_caret_from_position(
        &mut self,
        text_content: &TextContent,
        position: &TextPositionWithAffinity,
    ) {
        self.set_caret_from_position(position);
        self.update_styles(text_content);
    }

    pub fn extend_selection_from_position(&mut self, position: &TextPositionWithAffinity) {
        self.selection.extend_to(*position);
        self.reset_blink();
        self.push_event(TextEditorEvent::SelectionChanged);
    }

    pub fn set_overtype_mode(&mut self, overtype_mode: bool) {
        self.is_overtype_mode = overtype_mode;
    }

    pub fn toggle_overtype_mode(&mut self) {
        self.set_overtype_mode(!self.is_overtype_mode);
    }

    fn update_styles_from_selection(&mut self, text_content: &TextContent) -> bool {
        let paragraphs = text_content.paragraphs();
        if paragraphs.is_empty() {
            return false;
        }

        let start = self.selection.start();
        if start.paragraph >= paragraphs.len() {
            return false;
        }

        let end = self.selection.end();
        let end_paragraph = end.paragraph.min(paragraphs.len() - 1);

        self.current_styles.reset();
        let mut has_selected_content = false;
        for (para_idx, paragraph) in paragraphs
            .iter()
            .enumerate()
            .take(end_paragraph + 1)
            .skip(start.paragraph)
        {
            let paragraph_char_count: usize = paragraph
                .children()
                .iter()
                .map(|span| span.text.chars().count())
                .sum();

            let range_start = if para_idx == start.paragraph {
                start.offset.min(paragraph_char_count)
            } else {
                0
            };

            let range_end = if para_idx == end.paragraph {
                end.offset.min(paragraph_char_count)
            } else {
                paragraph_char_count
            };

            if range_start >= range_end {
                continue;
            }

            has_selected_content = true;
            self.current_styles
                .text_align
                .merge(Some(paragraph.text_align()));

            let mut char_pos = 0;
            for span in paragraph.children() {
                let span_len = span.text.chars().count();
                let span_start = char_pos;
                let span_end = char_pos + span_len;
                char_pos += span_len;

                let selected_start = range_start.max(span_start);
                let selected_end = range_end.min(span_end);
                if selected_start >= selected_end {
                    continue;
                }

                self.current_styles
                    .text_direction
                    .merge(Some(span.text_direction));
                self.current_styles
                    .text_decoration
                    .merge(span.text_decoration);
                self.current_styles
                    .text_transform
                    .merge(span.text_transform);
                self.current_styles
                    .font_family_id
                    .merge(Some(span.font_family.id()));
                self.current_styles
                    .font_style
                    .merge(Some(span.font_family.style()));
                self.current_styles.font_size.merge(Some(span.font_size));
                self.current_styles
                    .font_weight
                    .merge(Some(span.font_weight));
                self.current_styles
                    .font_variant_id
                    .merge(Some(span.font_variant_id));
                self.current_styles
                    .line_height
                    .merge(Some(span.line_height));
                self.current_styles
                    .letter_spacing
                    .merge(Some(span.letter_spacing));

                if self.current_styles.fills.is_empty() {
                    self.current_styles.fills.append(&mut span.fills.clone());
                } else if self.current_styles.fills != span.fills {
                    self.current_styles.fills_are_multiple = true;
                    self.current_styles.fills.append(&mut span.fills.clone());
                }
            }
        }

        has_selected_content
    }

    fn update_styles_from_caret(&mut self, text_content: &TextContent) -> bool {
        let focus = self.selection.focus;
        let paragraphs = text_content.paragraphs();
        let Some(current_paragraph) = paragraphs.get(focus.paragraph) else {
            return false;
        };
        let current_offset = focus.offset;
        let current_text_span = find_text_span_at_offset(current_paragraph, current_offset);

        self.current_styles.reset();
        self.current_styles
            .text_align
            .set_single(Some(current_paragraph.text_align()));
        if let Some((text_span_index, _)) = current_text_span {
            if let Some(text_span) = current_paragraph.children().get(text_span_index) {
                self.current_styles
                    .text_direction
                    .set_single(Some(text_span.text_direction));
                self.current_styles
                    .text_decoration
                    .set_single(text_span.text_decoration);
                self.current_styles
                    .text_transform
                    .set_single(text_span.text_transform);
                self.current_styles
                    .font_family_id
                    .set_single(Some(text_span.font_family.id()));
                self.current_styles
                    .font_style
                    .set_single(Some(text_span.font_family.style()));
                self.current_styles
                    .font_size
                    .set_single(Some(text_span.font_size));
                self.current_styles
                    .font_weight
                    .set_single(Some(text_span.font_weight));
                self.current_styles
                    .font_variant_id
                    .set_single(Some(text_span.font_variant_id));
                self.current_styles
                    .line_height
                    .set_single(Some(text_span.line_height));
                self.current_styles
                    .letter_spacing
                    .set_single(Some(text_span.letter_spacing));
                self.current_styles.fills = text_span.fills.clone();
            }
        } else {
            self.current_styles
                .line_height
                .set_single(Some(current_paragraph.line_height()));
            self.current_styles
                .letter_spacing
                .set_single(Some(current_paragraph.letter_spacing()));
        }
        true
    }

    pub fn update_styles(&mut self, text_content: &TextContent) -> bool {
        if self.selection.is_selection() {
            let styles_were_updated = self.update_styles_from_selection(text_content);
            if styles_were_updated {
                self.push_event(TextEditorEvent::StylesChanged);
            }
            return styles_were_updated;
        }
        // It is a caret.
        let styles_were_updated = self.update_styles_from_caret(text_content);
        if styles_were_updated {
            self.push_event(TextEditorEvent::StylesChanged);
        }
        styles_were_updated
    }

    pub fn update_blink(&mut self, timestamp_ms: f32) {
        if !self.has_focus {
            return;
        }

        if self.last_blink_time_ms == 0.0 {
            self.last_blink_time_ms = timestamp_ms;
            self.cursor_visible = true;
            return;
        }

        let elapsed = timestamp_ms - self.last_blink_time_ms;
        if elapsed >= CURSOR_BLINK_INTERVAL_MS {
            self.cursor_visible = !self.cursor_visible;
            self.last_blink_time_ms = timestamp_ms;
        }
    }

    pub fn reset_blink(&mut self) {
        self.cursor_visible = true;
        self.last_blink_time_ms = 0.0;
    }

    pub fn push_event(&mut self, event: TextEditorEvent) {
        if self.pending_events.last() != Some(&event) {
            self.pending_events.push(event);
        }
    }

    pub fn poll_event(&mut self) -> TextEditorEvent {
        self.pending_events.pop().unwrap_or(TextEditorEvent::None)
    }

    pub fn has_pending_events(&self) -> bool {
        !self.pending_events.is_empty()
    }

    pub fn delete_backward(&mut self, text_content: &mut TextContent, word_boundary: bool) {
        if self.selection.is_selection() {
            text_helpers::delete_selection_range(text_content, &self.selection);
            let start = self.selection.start();
            let clamped = text_helpers::clamp_cursor(start, text_content.paragraphs());
            self.selection.set_caret(clamped);
        } else if word_boundary {
            let cursor = self.selection.focus;
            if let Some(new_cursor) = text_helpers::delete_word_before(text_content, &cursor) {
                self.selection.set_caret(new_cursor);
            }
        } else {
            let cursor = self.selection.focus;
            if let Some(new_cursor) = text_helpers::delete_char_before(text_content, &cursor) {
                self.selection.set_caret(new_cursor);
            }
        }

        text_content.layout.clear();

        self.reset_blink();
        self.push_event(TextEditorEvent::ContentChanged);
        self.push_event(TextEditorEvent::NeedsLayout);
    }

    pub fn delete_forward(&mut self, text_content: &mut TextContent, word_boundary: bool) {
        if self.selection.is_selection() {
            text_helpers::delete_selection_range(text_content, &self.selection);
            let start = self.selection.start();
            let clamped = text_helpers::clamp_cursor(start, text_content.paragraphs());
            self.selection.set_caret(clamped);
        } else if word_boundary {
            let cursor = self.selection.focus;
            text_helpers::delete_word_after(text_content, &cursor);
            let clamped = text_helpers::clamp_cursor(cursor, text_content.paragraphs());
            self.selection.set_caret(clamped);
        } else {
            let cursor = self.selection.focus;
            text_helpers::delete_char_after(text_content, &cursor);
            let clamped = text_helpers::clamp_cursor(cursor, text_content.paragraphs());
            self.selection.set_caret(clamped);
        }

        text_content.layout.clear();

        self.reset_blink();
        self.push_event(TextEditorEvent::ContentChanged);
        self.push_event(TextEditorEvent::NeedsLayout);
    }

    pub fn insert_paragraph(&mut self, text_content: &mut TextContent) {
        if self.selection.is_selection() {
            text_helpers::delete_selection_range(text_content, &self.selection);
            let start = self.selection.start();
            self.selection.set_caret(start);
        }

        let cursor = self.selection.focus;
        if text_helpers::split_paragraph_at_cursor(text_content, &cursor) {
            let new_cursor =
                TextPositionWithAffinity::new_downstream_affinity(cursor.paragraph + 1, 0);
            self.selection.set_caret(new_cursor);
        }

        text_content.layout.clear();

        self.reset_blink();
        self.push_event(TextEditorEvent::ContentChanged);
        self.push_event(TextEditorEvent::NeedsLayout);
    }

    pub fn move_cursor(
        &mut self,
        text_content: &TextContent,
        direction: CursorDirection,
        word_boundary: bool,
        extend_selection: bool,
    ) -> bool {
        let paragraphs = text_content.paragraphs();
        if paragraphs.is_empty() {
            return false;
        }

        // With a range selected, Left/Right collapse to that edge and stop.
        // Extending (Shift) keeps the normal move-from-focus path below.
        if self.selection.is_selection() && !extend_selection {
            let edge = match direction {
                CursorDirection::Backward => Some(self.selection.start()),
                CursorDirection::Forward => Some(self.selection.end()),
                _ => None,
            };
            if let Some(caret) = edge {
                self.selection.set_caret(caret);
                self.update_styles(text_content);
                self.reset_blink();
                self.push_event(TextEditorEvent::SelectionChanged);
                return true;
            }
        }

        let focus = self.selection.focus;

        // Get the text direction of the span at the current cursor position
        let text_span_text_direction = if focus.paragraph < paragraphs.len() {
            text_helpers::get_text_span_text_direction_at_offset(
                &paragraphs[focus.paragraph],
                focus.offset,
            )
        } else {
            TextDirection::LTR
        };

        // In vertical-rl, Up/Down move by character along the column and
        // Left/Right cross columns (columns advance right-to-left).
        let is_vertical = text_content.is_vertical();
        let direction = if is_vertical {
            match direction {
                CursorDirection::Backward => CursorDirection::LineAfter, // Left -> next column
                CursorDirection::Forward => CursorDirection::LineBefore, // Right -> prev column
                CursorDirection::LineBefore => CursorDirection::Backward, // Up -> prev char
                CursorDirection::LineAfter => CursorDirection::Forward,  // Down -> next char
                other => other,
            }
        } else {
            direction
        };

        // For horizontal navigation, swap Backward/Forward when in RTL text
        let adjusted_direction = if !is_vertical && text_span_text_direction == TextDirection::RTL {
            match direction {
                CursorDirection::Backward => CursorDirection::Forward,
                CursorDirection::Forward => CursorDirection::Backward,
                other => other,
            }
        } else {
            direction
        };

        let new_cursor = match adjusted_direction {
            CursorDirection::Backward => {
                text_helpers::move_cursor_backward(&focus, paragraphs, word_boundary)
            }
            CursorDirection::Forward => {
                text_helpers::move_cursor_forward(&focus, paragraphs, word_boundary)
            }
            CursorDirection::LineBefore => {
                text_helpers::move_cursor_up(&focus, paragraphs, text_content)
            }
            CursorDirection::LineAfter => {
                text_helpers::move_cursor_down(&focus, paragraphs, text_content)
            }
            CursorDirection::LineStart if word_boundary => TextPositionWithAffinity::empty(),
            CursorDirection::LineEnd if word_boundary => text_helpers::move_cursor_line_end(
                &TextPositionWithAffinity::new_downstream_affinity(paragraphs.len() - 1, 0),
                paragraphs,
            ),
            CursorDirection::LineStart => text_helpers::move_cursor_line_start(&focus, paragraphs),
            CursorDirection::LineEnd => text_helpers::move_cursor_line_end(&focus, paragraphs),
        };

        if extend_selection {
            self.selection.extend_to(new_cursor);
        } else {
            self.selection.set_caret(new_cursor);
        }

        self.update_styles(text_content);

        self.reset_blink();
        self.push_event(TextEditorEvent::SelectionChanged);
        true
    }
}

impl Default for TextEditorState {
    fn default() -> Self {
        Self::new()
    }
}

fn is_word_char(c: char) -> bool {
    c.is_alphanumeric() || c == '_'
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::math::Rect;
    use crate::shapes::{
        Fill, FontFamily, FontStyle, GrowType, Paragraph, SolidColor, TextAlign, TextSpan,
    };
    use skia_safe::Color;

    fn span(text: &str, font_size: f32, fill: Fill) -> TextSpan {
        TextSpan::new(
            text.to_string(),
            FontFamily::new(Uuid::nil(), 400, FontStyle::Normal),
            font_size,
            1.2,
            0.0,
            None,
            None,
            TextDirection::LTR,
            400,
            Uuid::nil(),
            vec![fill],
        )
    }

    fn hello_world_content() -> TextContent {
        let black = Fill::Solid(SolidColor(Color::BLACK));
        let red = Fill::Solid(SolidColor(Color::RED));
        let mut content =
            TextContent::new(Rect::from_xywh(0.0, 0.0, 200.0, 100.0), GrowType::Fixed);
        content.add_paragraph(Paragraph::new(
            TextAlign::Left,
            TextDirection::LTR,
            None,
            None,
            1.2,
            0.0,
            vec![span("Hello ", 24.0, black), span("world", 40.0, red)],
        ));
        content
    }

    fn content(text: &str) -> TextContent {
        let mut content =
            TextContent::new(Rect::from_xywh(0.0, 0.0, 200.0, 100.0), GrowType::Fixed);
        content.add_paragraph(Paragraph::new(
            TextAlign::Left,
            TextDirection::LTR,
            None,
            None,
            1.2,
            0.0,
            vec![span(text, 14.0, Fill::Solid(SolidColor(Color::BLACK)))],
        ));
        content
    }

    fn drain_events(editor: &mut TextEditorState) -> Vec<TextEditorEvent> {
        let mut events = Vec::new();
        loop {
            let ev = editor.poll_event();
            if ev == TextEditorEvent::None {
                break;
            }
            events.push(ev);
        }
        events
    }

    fn pos(offset: usize) -> TextPositionWithAffinity {
        TextPositionWithAffinity::new_downstream_affinity(0, offset)
    }

    #[test]
    fn set_caret_from_position_alone_does_not_emit_styles_changed() {
        let content = hello_world_content();
        let mut editor = TextEditorState::new();
        editor.place_caret_from_position(
            &content,
            &TextPositionWithAffinity::new_downstream_affinity(0, 1),
        );
        drain_events(&mut editor);

        editor.set_caret_from_position(&TextPositionWithAffinity::new_downstream_affinity(0, 8));
        let events = drain_events(&mut editor);

        assert!(!events.contains(&TextEditorEvent::StylesChanged));
        assert_eq!(editor.current_styles.font_size.value(), &Some(24.0));
    }

    #[test]
    fn place_caret_from_position_syncs_styles_and_emits_styles_changed() {
        let content = hello_world_content();
        let mut editor = TextEditorState::new();
        editor.place_caret_from_position(
            &content,
            &TextPositionWithAffinity::new_downstream_affinity(0, 1),
        );
        drain_events(&mut editor);
        assert_eq!(editor.current_styles.font_size.value(), &Some(24.0));

        // Offset 8 is inside the second span ("world").
        editor.place_caret_from_position(
            &content,
            &TextPositionWithAffinity::new_downstream_affinity(0, 8),
        );
        let events = drain_events(&mut editor);

        assert!(events.contains(&TextEditorEvent::StylesChanged));
        assert_eq!(editor.current_styles.font_size.value(), &Some(40.0));
        assert_eq!(
            editor.current_styles.fills,
            vec![Fill::Solid(SolidColor(Color::RED))]
        );
    }

    #[test]
    fn place_caret_from_position_clears_mixed_selection_styles() {
        let content = hello_world_content();
        let mut editor = TextEditorState::new();
        editor.select_all(&content);
        assert!(editor.current_styles.font_size.is_multiple());
        assert!(editor.current_styles.fills_are_multiple);
        drain_events(&mut editor);

        editor.place_caret_from_position(
            &content,
            &TextPositionWithAffinity::new_downstream_affinity(0, 8),
        );
        let events = drain_events(&mut editor);

        assert!(events.contains(&TextEditorEvent::StylesChanged));
        assert_eq!(editor.current_styles.font_size.value(), &Some(40.0));
        assert!(!editor.current_styles.fills_are_multiple);
        assert_eq!(
            editor.current_styles.fills,
            vec![Fill::Solid(SolidColor(Color::RED))]
        );
    }

    #[test]
    fn move_backward_with_selection_collapses_to_start() {
        // "Third paragraph" — select "aph" at the end, then Left.
        let content = content("Third paragraph");
        let mut editor = TextEditorState::new();
        editor.selection.set_caret(pos(12));
        editor.selection.extend_to(pos(15));

        editor.move_cursor(&content, CursorDirection::Backward, false, false);

        assert!(editor.selection.is_collapsed());
        assert_eq!(editor.selection.focus.offset, 12);
    }

    #[test]
    fn move_forward_with_selection_collapses_to_end() {
        // Caret between "parag" and "raph", Shift+Left twice selects "ag", then Right.
        let content = content("Third paragraph");
        let mut editor = TextEditorState::new();
        editor.selection.set_caret(pos(11));
        editor.selection.extend_to(pos(9));

        editor.move_cursor(&content, CursorDirection::Forward, false, false);

        assert!(editor.selection.is_collapsed());
        assert_eq!(editor.selection.focus.offset, 11);
    }

    #[test]
    fn move_backward_with_full_selection_collapses_to_document_start() {
        let content = content("Hello");
        let mut editor = TextEditorState::new();
        editor.select_all(&content);

        editor.move_cursor(&content, CursorDirection::Backward, false, false);

        assert!(editor.selection.is_collapsed());
        assert_eq!(editor.selection.focus.offset, 0);
    }

    #[test]
    fn move_forward_with_full_selection_collapses_to_document_end() {
        let content = content("Hello");
        let mut editor = TextEditorState::new();
        editor.select_all(&content);

        editor.move_cursor(&content, CursorDirection::Forward, false, false);

        assert!(editor.selection.is_collapsed());
        assert_eq!(editor.selection.focus.offset, 5);
    }

    #[test]
    fn move_backward_while_extending_still_moves_from_focus() {
        let content = content("Third paragraph");
        let mut editor = TextEditorState::new();
        editor.selection.set_caret(pos(15));
        editor.selection.extend_to(pos(12));

        editor.move_cursor(&content, CursorDirection::Backward, false, true);

        assert!(editor.selection.is_selection());
        assert_eq!(editor.selection.anchor.offset, 15);
        assert_eq!(editor.selection.focus.offset, 11);
    }

    #[test]
    fn move_backward_with_collapsed_caret_still_moves() {
        let content = content("Hello");
        let mut editor = TextEditorState::new();
        editor.selection.set_caret(pos(3));

        editor.move_cursor(&content, CursorDirection::Backward, false, false);

        assert!(editor.selection.is_collapsed());
        assert_eq!(editor.selection.focus.offset, 2);
    }

    fn caret(paragraph: usize, offset: usize) -> TextSelection {
        TextSelection::from_position_with_affinity(
            TextPositionWithAffinity::new_downstream_affinity(paragraph, offset),
        )
    }

    #[test]
    fn composition_replaces_the_previous_preview_wherever_the_caret_is() {
        let mut composition = TextComposition::new();
        composition.start();

        // First update: the pre-composition caret is the replaced range.
        composition.update("に");
        let replaced = composition.get_selection(&caret(0, 2));
        assert_eq!((replaced.start().offset, replaced.end().offset), (2, 2));
        composition.start = Some(replaced.start());

        // The caret sits after the preview; the next update still replaces
        // the preview itself.
        composition.update("にほ");
        let replaced = composition.get_selection(&caret(0, 3));
        assert_eq!((replaced.start().offset, replaced.end().offset), (2, 3));

        composition.end();
        assert!(composition.start.is_none());
    }
}