use crate::prelude::*;
use iris_core::{TextData, UiColor};
use parley::{Affinity, Layout, Selection};
use std::ops::{Deref, DerefMut};
use winit::{
    event::KeyEvent,
    keyboard::{Key, NamedKey},
};

#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Motion {
    Left,
    Right,
    LeftWord,
    RightWord,
    Up,
    Down,
    LineStart,
    LineEnd,
}

pub struct TextEdit {
    view: TextView,
    /// `None` represents unfocused, which Parley's `Selection` cannot express.
    selection: Option<Selection>,
    history: Vec<(String, Option<Selection>)>,
    double_hit: Option<usize>,
    pub mode: EditMode,
}

#[derive(Clone, Copy, PartialEq)]
pub enum EditMode {
    SingleLine,
    MultiLine,
}

impl TextEdit {
    pub fn new(view: TextView, mode: EditMode) -> Self {
        Self {
            view,
            selection: None,
            history: Default::default(),
            double_hit: None,
            mode,
        }
    }

    pub fn selected_text(&self) -> Option<String> {
        let sel = self.selection?;
        if sel.is_collapsed() {
            return None;
        }
        Some(self.buf.text()[sel.text_range()].to_string())
    }
}

impl Widget for TextEdit {
    fn draw(&mut self, painter: &mut Painter) -> Size {
        let base = painter.layer;
        painter.child_layer();
        let (_, size) = self.view.draw(painter);
        painter.layer = base;
        let region = self.region();

        let Some(selection) = self.selection else {
            return size;
        };
        let layout = self.view.buf.layout();

        // parley reports selection as boxes in layout space, so bidi and
        // wrapped lines come out right without this code knowing about either.
        for (rect, _) in selection.geometry(layout) {
            let rect_size = vec2(rect.width() as f32, rect.height() as f32);
            let top_left = vec2(rect.x0 as f32, rect.y0 as f32);
            painter.primitive_within(
                RectPrimitive::color(Color::SKY),
                rect_size
                    .align(Align::TOP_LEFT)
                    .offset(top_left)
                    .within(&region),
            );
        }

        let caret = selection.focus().geometry(layout, CARET_WIDTH);
        let caret_size = vec2(caret.width() as f32, caret.height() as f32);
        let top_left = vec2(caret.x0 as f32, caret.y0 as f32);
        painter.primitive_within(
            RectPrimitive::color(Color::WHITE),
            caret_size
                .align(Align::TOP_LEFT)
                .offset(top_left)
                .within(&region),
        );
        size
    }
}

const CARET_WIDTH: f32 = 1.0;

pub struct TextEditCtx<'a> {
    pub text: &'a mut TextEdit,
    pub data: &'a mut TextData,
}

impl<'a> TextEditCtx<'a> {
    fn layout(&mut self) -> &Layout<UiColor> {
        let attrs = self.text.view.attrs.clone();
        let width = self.text.view.wrap_width();
        self.text.view.buf.shape(self.data, &attrs, width);
        self.text.view.buf.layout()
    }

    fn clamp_selection_to_layout(&mut self) {
        if let Some(sel) = self.text.selection {
            let layout = self.layout();
            self.text.selection = Some(sel.refresh(layout));
        }
    }

    pub fn take(&mut self) -> String {
        let text = std::mem::take(self.text.view.buf.edit());
        self.text.selection = None;
        text
    }

    pub fn set(&mut self, text: &str) {
        let text = self.string(text);
        self.text.view.buf.set_text(text);
        self.text.selection = None;
    }

    pub fn motion(&mut self, motion: Motion, select: bool) {
        let Some(sel) = self.text.selection else {
            return;
        };
        let layout = self.layout();
        let sel = apply_motion(sel, layout, motion, select);
        self.text.selection = Some(sel);
    }

    /// Replace the `len` characters before the caret. This is the IME's
    /// preedit path: it re-sends the whole composition each time.
    pub fn replace(&mut self, len: usize, text: &str) {
        let text = self.string(text);
        for _ in 0..len {
            self.backspace(false);
        }
        self.insert_str(&text);
    }

    fn string(&self, text: &str) -> String {
        if self.text.mode == EditMode::SingleLine {
            text.replace('\n', "")
        } else {
            text.to_string()
        }
    }

    pub fn insert(&mut self, text: &str) {
        let text = self.string(text);
        self.insert_str(&text);
    }

    fn insert_str(&mut self, text: &str) {
        if text.is_empty() {
            return;
        }
        self.clear_span();
        let at = match self.text.selection {
            Some(sel) => sel.focus().index(),
            None => return,
        };
        let at = at.min(self.text.view.buf.text().len());
        self.text.view.buf.edit().insert_str(at, text);
        self.set_caret(at + text.len());
    }

    pub fn clear_span(&mut self) -> bool {
        let Some(sel) = self.text.selection else {
            return false;
        };
        if sel.is_collapsed() {
            return false;
        }
        let range = sel.text_range();
        self.text.view.buf.edit().replace_range(range.clone(), "");
        self.set_caret(range.start);
        true
    }

    fn set_caret(&mut self, index: usize) {
        let index = index.min(self.text.view.buf.text().len());
        let layout = self.layout();
        self.text.selection = Some(Selection::from_byte_index(
            layout,
            index,
            Affinity::default(),
        ));
    }

    pub fn newline(&mut self) {
        if self.text.mode == EditMode::MultiLine {
            self.insert_str("\n");
        }
    }

    pub fn backspace(&mut self, word: bool) {
        if self.clear_span() {
            return;
        }
        let Some(sel) = self.text.selection else {
            return;
        };
        let end = sel.focus().index();
        if end == 0 {
            return;
        }
        let layout = self.layout();
        let start = if word {
            sel.focus().previous_logical_word(layout).index()
        } else {
            let Some(cluster) = sel.focus().logical_clusters(layout)[0] else {
                return;
            };
            let range = cluster.text_range();
            if cluster.is_hard_line_break() || cluster.is_emoji() {
                range.start
            } else {
                self.text.view.buf.text()[..range.end]
                    .char_indices()
                    .next_back()
                    .map_or(range.start, |(start, _)| start)
            }
        };
        self.delete_range(start, end);
    }

    pub fn delete(&mut self, word: bool) {
        if self.clear_span() {
            return;
        }
        let Some(sel) = self.text.selection else {
            return;
        };
        let start = sel.focus().index();
        if start >= self.text.view.buf.text().len() {
            return;
        }
        let layout = self.layout();
        let end = if word {
            sel.focus().next_logical_word(layout).index()
        } else {
            let clusters = sel.focus().logical_clusters(layout);
            let Some(cluster) = clusters[1].as_ref() else {
                return;
            };
            cluster.text_range().end
        };
        self.delete_range(start, end);
    }

    fn delete_range(&mut self, start: usize, end: usize) {
        self.text.view.buf.edit().replace_range(start..end, "");
        self.set_caret(start);
    }

    pub fn select_all(&mut self) {
        let len = self.text.view.buf.text().len();
        if len == 0 {
            return;
        }
        let layout = self.layout();
        let anchor = parley::Cursor::from_byte_index(layout, 0, Affinity::default());
        let focus = parley::Cursor::from_byte_index(layout, len, Affinity::default());
        self.text.selection = Some(Selection::new(anchor, focus));
    }

    pub fn select(&mut self, pos: Vec2, size: Vec2, drag: bool, recent: bool) {
        let pos = pos - self.text.region().top_left().to_px(size);
        let prev_sel = self.text.selection;
        let prev_hit = self.text.double_hit;

        let layout = self.layout();
        let (selection, double_hit) = if drag {
            let Some(selection) = prev_sel else {
                return;
            };
            (selection.extend_to_point(layout, pos.x, pos.y), prev_hit)
        } else {
            let hit = Selection::from_point(layout, pos.x, pos.y);
            let index = hit.focus().index();
            // Successive clicks at one index select the word, then the line.
            if recent && prev_hit == Some(index) {
                (Selection::line_from_point(layout, pos.x, pos.y), None)
            } else if recent && prev_sel.map(|s| s.focus().index()) == Some(index) {
                (
                    Selection::word_from_point(layout, pos.x, pos.y),
                    Some(index),
                )
            } else {
                (hit, None)
            }
        };

        self.text.selection = Some(selection);
        self.text.double_hit = double_hit;
    }

    pub fn deselect(&mut self) {
        self.text.selection = None;
        self.text.double_hit = None;
    }

    pub fn apply_event(&mut self, event: &KeyEvent, modifiers: &Modifiers) -> TextInputResult {
        let old = (self.text.view.buf.text().to_string(), self.text.selection);
        let mut undo = false;
        let res = self.apply_event_inner(event, modifiers, &mut undo);
        if undo {
            if let Some((old, selection)) = self.text.history.pop() {
                self.set(&old);
                self.text.selection = selection;
                self.clamp_selection_to_layout();
            }
        } else if self.text.view.buf.text() != old.0 {
            self.text.history.push(old);
        }
        res
    }

    fn apply_event_inner(
        &mut self,
        event: &KeyEvent,
        modifiers: &Modifiers,
        undo: &mut bool,
    ) -> TextInputResult {
        match &event.logical_key {
            Key::Named(named) => match named {
                NamedKey::Backspace => self.backspace(modifiers.control),
                NamedKey::Delete => self.delete(modifiers.control),
                NamedKey::Space => self.insert(" "),
                NamedKey::Enter => {
                    if modifiers.shift {
                        self.newline();
                    } else {
                        return TextInputResult::Submit;
                    }
                }
                NamedKey::ArrowRight => {
                    let motion = if modifiers.control {
                        Motion::RightWord
                    } else {
                        Motion::Right
                    };
                    self.motion(motion, modifiers.shift);
                }
                NamedKey::ArrowLeft => {
                    let motion = if modifiers.control {
                        Motion::LeftWord
                    } else {
                        Motion::Left
                    };
                    self.motion(motion, modifiers.shift);
                }
                NamedKey::ArrowUp => self.motion(Motion::Up, modifiers.shift),
                NamedKey::ArrowDown => self.motion(Motion::Down, modifiers.shift),
                NamedKey::Home => self.motion(Motion::LineStart, modifiers.shift),
                NamedKey::End => self.motion(Motion::LineEnd, modifiers.shift),
                NamedKey::Escape => {
                    self.deselect();
                    return TextInputResult::Unfocus;
                }
                _ => return TextInputResult::Unused,
            },
            Key::Character(text) => {
                if modifiers.control {
                    match text.as_str() {
                        "v" => return TextInputResult::Paste,
                        "c" => {
                            if let Some(content) = self.text.selected_text() {
                                return TextInputResult::Copy(content);
                            }
                        }
                        "x" => {
                            if let Some(content) = self.text.selected_text() {
                                self.clear_span();
                                return TextInputResult::Copy(content);
                            }
                        }
                        "a" => self.select_all(),
                        "z" => *undo = true,
                        _ => self.insert(text),
                    }
                } else {
                    self.insert(text);
                }
            }
            _ => return TextInputResult::Unused,
        }
        TextInputResult::Used
    }
}

fn apply_motion(
    sel: Selection,
    layout: &Layout<UiColor>,
    motion: Motion,
    extend: bool,
) -> Selection {
    match motion {
        Motion::Left => sel.previous_visual(layout, extend),
        Motion::Right => sel.next_visual(layout, extend),
        Motion::LeftWord => sel.previous_visual_word(layout, extend),
        Motion::RightWord => sel.next_visual_word(layout, extend),
        Motion::Up => sel.previous_line(layout, extend),
        Motion::Down => sel.next_line(layout, extend),
        Motion::LineStart => sel.line_start(layout, extend),
        Motion::LineEnd => sel.line_end(layout, extend),
    }
}

#[derive(Default)]
pub struct Modifiers {
    pub shift: bool,
    pub control: bool,
}

impl Modifiers {
    pub fn clear(&mut self) {
        self.shift = false;
        self.control = false;
    }
}

pub enum TextInputResult {
    Used,
    Unused,
    Unfocus,
    Submit,
    Copy(String),
    Paste,
}

impl TextInputResult {
    pub fn unfocus(&self) -> bool {
        matches!(self, TextInputResult::Unfocus)
    }
}

impl Deref for TextEdit {
    type Target = TextView;

    fn deref(&self) -> &Self::Target {
        &self.view
    }
}

impl DerefMut for TextEdit {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.view
    }
}

pub trait TextEditable {
    fn edit<'a>(&self, ui: &'a mut impl UiRsc) -> TextEditCtx<'a>;
}

impl<I: IdLike<Widget = TextEdit>> TextEditable for I {
    fn edit<'a>(&self, ui: &'a mut impl UiRsc) -> TextEditCtx<'a> {
        let ui = ui.ui_mut();
        TextEditCtx {
            text: ui.widgets.get_mut(self).unwrap(),
            data: &mut ui.text,
        }
    }
}