//! The roulette table and wheel, painted from `RouletteView`.
//!
//! Geometry is the GUI's business: the core only says which number or region a
//! chip or the cursor is on. Everything here is derived from that, so the two
//! frontends can lay the same table out differently.

use std::f32::consts::{FRAC_PI_2, TAU};

use eframe::egui::{
    Align2, Color32, CornerRadius, Painter, PointerButton, Pos2, Rect, Sense, Shape, Stroke,
    StrokeKind, Ui, Vec2, pos2, vec2,
};
use zagan_bet::client::games::roulette::target_at as lattice_target;
use zagan_bet::client::view::{RoulettePhase, RouletteView};
use zagan_bet::roulette::{BetTarget, Outside, WHEEL, color as wheel_color, is_red};

use crate::theme;

const COLUMNS: usize = 12;
const ROWS: usize = 3;
const OUTSIDE_ORDER: [Outside; 6] = [
    Outside::Low,
    Outside::Even,
    Outside::Red,
    Outside::Black,
    Outside::Odd,
    Outside::High,
];

const DOZEN_ROW: f32 = 0.72;
const COLUMN_ROW: f32 = 0.55;
const OUTSIDE_ROW: f32 = 0.62;
const HEIGHT_UNITS: f32 = ROWS as f32 + DOZEN_ROW + COLUMN_ROW + OUTSIDE_ROW;
const BOARD_PAD: f32 = 6.0;

/// Largest table that fits in `available`, including its felt border.
pub fn size_for(available: Vec2) -> Vec2 {
    let inner = (available - Vec2::splat(BOARD_PAD * 2.0)).max(Vec2::ZERO);
    let cell = (inner.x / (COLUMNS as f32 + 1.0))
        .min(inner.y / HEIGHT_UNITS)
        .max(1.0);
    vec2((COLUMNS as f32 + 1.0) * cell, HEIGHT_UNITS * cell) + Vec2::splat(BOARD_PAD * 2.0)
}

/// What the pointer did to the felt this frame.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum FeltAction {
    /// Left click: add the selected chip.
    Place(BetTarget),
    /// Right or middle click: take one chip back.
    Reduce(BetTarget),
}

/// The table painted at `size`; returns the bet the pointer changed.
pub fn felt(ui: &mut Ui, size: Vec2, view: &RouletteView) -> Option<FeltAction> {
    let (rect, response) = ui.allocate_exact_size(size, Sense::click());
    let felt = Felt::new(rect);
    let hovered = if view.phase == RoulettePhase::Spinning {
        None
    } else {
        response.hover_pos().and_then(|pos| felt.target_at(pos))
    };
    let painter = ui.painter();

    painter.rect_filled(rect, theme::RADIUS_LG, theme::FELT_DARK);

    // Every cell the hovered bet covers tints, so a split or corner reads
    // before the chip lands.
    let covered = hovered.as_ref().map(BetTarget::numbers).unwrap_or_default();
    for number in 0..=36u8 {
        felt.paint_number(
            painter,
            number,
            covered.contains(&number),
            hovered == Some(BetTarget::Straight { number }),
        );
    }
    for index in 0..3 {
        felt.paint_dozen(
            painter,
            index,
            hovered == Some(BetTarget::Dozen { index: index as u8 }),
        );
    }
    for index in 0..3 {
        felt.paint_column(
            painter,
            index,
            hovered == Some(BetTarget::Column { index: index as u8 }),
        );
    }
    for (index, kind) in OUTSIDE_ORDER.iter().enumerate() {
        felt.paint_outside(
            painter,
            index,
            *kind,
            hovered == Some(BetTarget::Outside { kind: *kind }),
        );
    }

    if view.phase == RoulettePhase::Result {
        if let Some(number) = view.number {
            painter.rect_stroke(
                felt.number_rect(number).shrink(2.0),
                theme::RADIUS_SM,
                Stroke::new(2.0, theme::GOLD),
                StrokeKind::Inside,
            );
        }
    }

    for chip in &view.bets.chips {
        if let Some(center) = felt.anchor(&chip.target) {
            paint_chip(painter, center, felt.cell_size() * 0.26, chip.amount);
        }
    }

    if let Some(target) = &hovered {
        if let Some(center) = felt.anchor(target) {
            paint_chip_preview(painter, center, felt.cell_size() * 0.26, view.chip);
        }
    }

    if response.clicked_by(PointerButton::Secondary) || response.clicked_by(PointerButton::Middle) {
        hovered.map(FeltAction::Reduce)
    } else if response.clicked() {
        hovered.map(FeltAction::Place)
    } else {
        None
    }
}

/// Geometry of one table: the felt is 13 cells wide (zero plus twelve
/// columns) and 3 + 0.72 + 0.55 + 0.62 cells tall.
///
/// Public so the pointer snapping can be tested without a window.
pub struct Felt {
    cell: f32,
    origin: Pos2,
}

impl Felt {
    pub fn new(board: Rect) -> Self {
        let inner = board.shrink(BOARD_PAD);
        Self {
            cell: inner.width() / (COLUMNS as f32 + 1.0),
            origin: inner.min,
        }
    }

    pub fn cell_size(&self) -> f32 {
        self.cell
    }

    pub fn number_rect(&self, number: u8) -> Rect {
        debug_assert!(number <= 36);
        if number == 0 {
            return Rect::from_min_size(self.origin, vec2(self.cell, self.cell * ROWS as f32));
        }
        let column = ((number - 1) / 3) as f32;
        let row = (2 - (number - 1) % 3) as f32;
        Rect::from_min_size(
            self.origin + vec2(self.cell * (1.0 + column), self.cell * row),
            Vec2::splat(self.cell),
        )
    }

    fn dozen_rect(&self, index: usize) -> Rect {
        let y = self.origin.y + self.cell * ROWS as f32;
        Rect::from_min_size(
            pos2(self.origin.x + self.cell * (1.0 + 4.0 * index as f32), y),
            vec2(self.cell * 4.0, self.cell * DOZEN_ROW),
        )
    }

    fn column_rect(&self, index: usize) -> Rect {
        let y = self.origin.y + self.cell * (ROWS as f32 + DOZEN_ROW);
        Rect::from_min_size(
            pos2(self.origin.x + self.cell * (1.0 + 4.0 * index as f32), y),
            vec2(self.cell * 4.0, self.cell * COLUMN_ROW),
        )
    }

    fn outside_rect(&self, index: usize) -> Rect {
        let y = self.origin.y + self.cell * (ROWS as f32 + DOZEN_ROW + COLUMN_ROW);
        Rect::from_min_size(
            pos2(self.origin.x + self.cell * (1.0 + 2.0 * index as f32), y),
            vec2(self.cell * 2.0, self.cell * OUTSIDE_ROW),
        )
    }

    /// Where a chip sits for this target.
    pub fn anchor(&self, target: &BetTarget) -> Option<Pos2> {
        Some(match target {
            BetTarget::Straight { number } => self.number_rect(*number).center(),
            BetTarget::Split { a, b } => {
                let a = self.number_rect(*a).center();
                let b = self.number_rect(*b).center();
                pos2((a.x + b.x) * 0.5, (a.y + b.y) * 0.5)
            }
            BetTarget::Corner { numbers } => {
                let mut sum = Vec2::ZERO;
                for number in numbers {
                    sum += self.number_rect(*number).center().to_vec2();
                }
                (sum / numbers.len() as f32).to_pos2()
            }
            BetTarget::Dozen { index } => self.dozen_rect(*index as usize).center(),
            BetTarget::Column { index } => self.column_rect(*index as usize).center(),
            BetTarget::Outside { kind } => {
                let index = OUTSIDE_ORDER
                    .iter()
                    .position(|candidate| candidate == kind)?;
                self.outside_rect(index).center()
            }
        })
    }

    fn grid_origin(&self) -> Pos2 {
        self.origin + vec2(self.cell, 0.0)
    }

    /// The bet under the pointer, snapped to the fine lattice: a cell centre
    /// is a straight, a line is a split, a crossing is a corner.
    pub fn target_at(&self, pos: Pos2) -> Option<BetTarget> {
        if self.number_rect(0).contains(pos) {
            return Some(BetTarget::Straight { number: 0 });
        }

        let grid = self.grid_origin();
        let fx = (pos.x - grid.x) / self.cell;
        let fy = (pos.y - grid.y) / self.cell;
        if (0.0..COLUMNS as f32).contains(&fx) && (0.0..ROWS as f32).contains(&fy) {
            // Thresholds sit a quarter cell from a centre, so the inner half
            // of a cell is a straight and its edges are splits or corners.
            let x = (fx * 2.0).round().clamp(1.0, 23.0) as usize;
            let y = (fy * 2.0).round().clamp(1.0, 5.0) as usize;
            return lattice_target(x, y);
        }

        for index in 0..3usize {
            if self.dozen_rect(index).contains(pos) {
                return Some(BetTarget::Dozen { index: index as u8 });
            }
            if self.column_rect(index).contains(pos) {
                return Some(BetTarget::Column { index: index as u8 });
            }
        }
        for (index, kind) in OUTSIDE_ORDER.iter().enumerate() {
            if self.outside_rect(index).contains(pos) {
                return Some(BetTarget::Outside { kind: *kind });
            }
        }
        None
    }

    fn paint_number(&self, painter: &Painter, number: u8, covered: bool, hovered: bool) {
        let rect = self.number_rect(number);
        let fill = if number == 0 {
            theme::ROULETTE_ZERO
        } else if is_red(number) {
            theme::ROULETTE_RED
        } else {
            theme::ROULETTE_BLACK
        };
        painter.rect_filled(rect, CornerRadius::ZERO, fill);
        painter.rect_stroke(
            rect,
            CornerRadius::ZERO,
            Stroke::new(1.0, theme::FELT_LINE),
            StrokeKind::Inside,
        );
        if covered {
            painter.rect_filled(rect, CornerRadius::ZERO, theme::ACCENT.gamma_multiply(0.16));
        } else if hovered {
            painter.rect_filled(
                rect,
                CornerRadius::ZERO,
                Color32::WHITE.gamma_multiply(0.10),
            );
        }
        painter.text(
            rect.center(),
            Align2::CENTER_CENTER,
            number,
            theme::mono(self.number_font()),
            theme::FELT_TEXT,
        );
    }

    fn paint_dozen(&self, painter: &Painter, index: usize, hovered: bool) {
        let rect = self.dozen_rect(index);
        self.paint_region(painter, rect, hovered);
        let label = match index {
            0 => "1st 12",
            1 => "2nd 12",
            _ => "3rd 12",
        };
        painter.text(
            rect.center(),
            Align2::CENTER_CENTER,
            label,
            theme::sans(self.label_font()),
            theme::FELT_TEXT,
        );
    }

    fn paint_column(&self, painter: &Painter, index: usize, hovered: bool) {
        let rect = self.column_rect(index);
        self.paint_region(painter, rect, hovered);
        painter.text(
            rect.center(),
            Align2::CENTER_CENTER,
            "2:1",
            theme::sans(self.label_font()),
            theme::FELT_TEXT,
        );
    }

    fn paint_outside(&self, painter: &Painter, index: usize, kind: Outside, hovered: bool) {
        let rect = self.outside_rect(index);
        self.paint_region(painter, rect, hovered);
        let color = match kind {
            Outside::Red => theme::ROULETTE_RED,
            Outside::Black => theme::TEXT_DIM,
            _ => theme::FELT_TEXT,
        };
        painter.text(
            rect.center(),
            Align2::CENTER_CENTER,
            kind.label(),
            theme::sans(self.label_font()),
            color,
        );
    }

    fn paint_region(&self, painter: &Painter, rect: Rect, hovered: bool) {
        painter.rect_filled(rect, CornerRadius::ZERO, theme::FELT);
        painter.rect_stroke(
            rect,
            CornerRadius::ZERO,
            Stroke::new(1.0, theme::FELT_LINE),
            StrokeKind::Inside,
        );
        if hovered {
            painter.rect_filled(
                rect,
                CornerRadius::ZERO,
                Color32::WHITE.gamma_multiply(0.10),
            );
        }
    }

    fn number_font(&self) -> f32 {
        (self.cell * 0.40).clamp(12.0, 22.0)
    }

    fn label_font(&self) -> f32 {
        (self.cell * 0.24).clamp(10.0, 15.0)
    }
}

/// A single chip, also used by the sidebar's chip tray.
pub fn paint_chip(painter: &Painter, center: Pos2, radius: f32, amount: u64) {
    let fill = chip_color(amount);
    painter.circle_filled(center, radius, fill);
    painter.circle_stroke(
        center,
        radius - radius * 0.18,
        Stroke::new(radius * 0.10, Color32::WHITE.gamma_multiply(0.55)),
    );
    let text_color = if amount <= 10 {
        theme::BG
    } else {
        Color32::WHITE
    };
    painter.text(
        center,
        Align2::CENTER_CENTER,
        amount,
        theme::mono(radius * 0.85),
        text_color,
    );
}

/// The chip under the pointer, showing what a click would add.
pub fn paint_chip_preview(painter: &Painter, center: Pos2, radius: f32, amount: u64) {
    painter.circle_filled(center, radius, chip_color(amount).gamma_multiply(0.45));
    painter.circle_stroke(
        center,
        radius,
        Stroke::new(2.0, Color32::WHITE.gamma_multiply(0.85)),
    );
    painter.text(
        center,
        Align2::CENTER_CENTER,
        amount,
        theme::mono(radius * 0.85),
        Color32::WHITE,
    );
}

/// Colour per denomination, as a chip tray would be stocked.
pub fn chip_color(amount: u64) -> Color32 {
    match amount {
        0..=10 => Color32::from_rgb(0xd9, 0xd3, 0xc7),
        11..=25 => Color32::from_rgb(0x3f, 0x7f, 0xd1),
        26..=50 => Color32::from_rgb(0xc9, 0x4b, 0x4b),
        _ => Color32::from_rgb(0x3a, 0x9d, 0x5d),
    }
}

fn segment_color(number: u8) -> Color32 {
    match wheel_color(number) {
        "red" => theme::ROULETTE_RED,
        "green" => theme::ROULETTE_ZERO,
        _ => Color32::from_rgb(0x2b, 0x35, 0x3f),
    }
}

/// Number currently under the pointer for this wheel rotation.
pub fn number_under(rotation: f32) -> u8 {
    let segment = TAU / WHEEL.len() as f32;
    let index = (-rotation / segment).round() as i64;
    WHEEL[index.rem_euclid(WHEEL.len() as i64) as usize]
}

/// The wheel dial: 37 coloured pockets, a fixed pointer, and the number under
/// it. `rotation` is in radians.
pub fn wheel(ui: &mut Ui, diameter: f32, view: &RouletteView, rotation: f32) {
    let (rect, _) = ui.allocate_exact_size(Vec2::splat(diameter), Sense::hover());
    let painter = ui.painter();
    let center = rect.center();
    let radius = diameter * 0.5;

    painter.circle_filled(center, radius, theme::SURFACE_RAISED);
    painter.circle_stroke(center, radius - 1.0, Stroke::new(1.0, theme::LINE));

    let segment = TAU / WHEEL.len() as f32;
    let ring = radius * 0.80;
    let dot = (radius * 0.072).max(2.0);
    painter.circle_stroke(
        center,
        ring,
        Stroke::new(dot * 2.0, Color32::from_rgb(0x1f, 0x28, 0x31)),
    );
    for (index, number) in WHEEL.iter().enumerate() {
        let angle = -FRAC_PI_2 + rotation + index as f32 * segment;
        let pocket = center + vec2(angle.cos(), angle.sin()) * ring;
        let winning = view.phase == RoulettePhase::Result && view.number == Some(*number);
        let stroke = if winning {
            Stroke::new(2.0, theme::GOLD)
        } else {
            Stroke::new(1.0, Color32::from_rgb(0x3a, 0x46, 0x52))
        };
        painter.circle(
            pocket,
            if winning { dot * 1.25 } else { dot },
            segment_color(*number),
            stroke,
        );
    }

    // A fixed pointer at the top, marking the winning pocket.
    let tip = center + vec2(0.0, -radius + dot * 0.30);
    painter.add(Shape::convex_polygon(
        vec![
            tip,
            tip + vec2(-dot * 0.9, -dot * 1.4),
            tip + vec2(dot * 0.9, -dot * 1.4),
        ],
        theme::TEXT,
        Stroke::NONE,
    ));

    let inner = radius * 0.52;
    painter.circle_filled(center, inner, theme::SURFACE);
    painter.circle_stroke(center, inner, Stroke::new(1.0, theme::LINE));

    let displayed = match view.phase {
        RoulettePhase::Spinning => Some(number_under(rotation)),
        _ => view.number,
    };
    match displayed {
        Some(number) => {
            let color = match wheel_color(number) {
                "red" => theme::ROULETTE_RED,
                "green" => theme::WIN,
                _ => theme::TEXT,
            };
            painter.text(
                center,
                Align2::CENTER_CENTER,
                number,
                theme::mono(inner * 0.85),
                color,
            );
        }
        None => {
            painter.text(
                center,
                Align2::CENTER_CENTER,
                "—",
                theme::mono(inner * 0.55),
                theme::TEXT_FAINT,
            );
        }
    }
}

/// "Straight 17", "Corner 17/18/20/21", "Red".
pub fn target_name(target: &BetTarget) -> String {
    match target {
        BetTarget::Straight { number } => format!("Straight {number}"),
        BetTarget::Split { a, b } => format!("Split {a}/{b}"),
        BetTarget::Corner { numbers } => format!(
            "Corner {}/{}/{}/{}",
            numbers[0], numbers[1], numbers[2], numbers[3]
        ),
        BetTarget::Dozen { index } => match index {
            0 => "1st 12".to_string(),
            1 => "2nd 12".to_string(),
            _ => "3rd 12".to_string(),
        },
        BetTarget::Column { index } => format!("Column {}", index + 1),
        BetTarget::Outside { kind } => title_case(kind.label()),
    }
}

fn title_case(text: &str) -> String {
    let mut characters = text.chars();
    match characters.next() {
        Some(first) => {
            first.to_uppercase().collect::<String>() + &characters.as_str().to_lowercase()
        }
        None => String::new(),
    }
}

/// Small coloured dot for a result strip.
pub fn paint_result_dot(painter: &Painter, center: Pos2, radius: f32, number: u8) {
    let color = match wheel_color(number) {
        "red" => theme::ROULETTE_RED,
        "green" => theme::ROULETTE_ZERO,
        _ => theme::ROULETTE_BLACK,
    };
    painter.circle_filled(center, radius, color);
    painter.text(
        center,
        Align2::CENTER_CENTER,
        number,
        theme::mono(radius * 0.95),
        theme::FELT_TEXT,
    );
}