//! Look and feel for the desktop frontend.
//!
//! The palette is derived from the terminal client's ANSI scheme so the two
//! frontends read as the same product: near-black ground, low-contrast panels,
//! cyan for focus, and the felt green reserved for the roulette table.
//!
//! egui's defaults are a debug tool's palette. Every colour, size and corner
//! used by the app comes from this module; widgets never pick their own.

use std::sync::Arc;

use eframe::egui::style::WidgetVisuals;
use eframe::egui::{
    self, Color32, Context, CornerRadius, FontData, FontDefinitions, FontFamily, FontId, Margin,
    RichText, Stroke, TextStyle, Theme, Visuals,
};

// ---------------------------------------------------------------------------
// Colour tokens
// ---------------------------------------------------------------------------

/// Window ground. Everything else sits above this.
pub const BG: Color32 = Color32::from_rgb(0x0a, 0x0e, 0x12);
/// Cards, header, sidebar.
pub const SURFACE: Color32 = Color32::from_rgb(0x11, 0x17, 0x1d);
/// Inputs, pills, raised rows.
pub const SURFACE_RAISED: Color32 = Color32::from_rgb(0x17, 0x1f, 0x27);
/// Hover state.
pub const SURFACE_HOVER: Color32 = Color32::from_rgb(0x1d, 0x27, 0x31);
/// Hairlines and table borders.
pub const LINE: Color32 = Color32::from_rgb(0x24, 0x2e, 0x38);
/// Primary text.
pub const TEXT: Color32 = Color32::from_rgb(0xd9, 0xe2, 0xea);
/// Labels and secondary text.
pub const TEXT_DIM: Color32 = Color32::from_rgb(0x8a, 0x98, 0xa6);
/// Disabled text, captions.
pub const TEXT_FAINT: Color32 = Color32::from_rgb(0x5b, 0x67, 0x73);
/// Focus, cursor, selection.
pub const ACCENT: Color32 = Color32::from_rgb(0x4f, 0xb8, 0xc9);
/// Wins, "online", the spin button.
pub const WIN: Color32 = Color32::from_rgb(0x4e, 0xc2, 0x7b);
/// Losses and errors.
pub const LOSS: Color32 = Color32::from_rgb(0xe0, 0x5a, 0x5a);
/// Chips and pending bets.
pub const GOLD: Color32 = Color32::from_rgb(0xe0, 0xb6, 0x4a);

/// Roulette felt. Never used outside the table.
pub const FELT: Color32 = Color32::from_rgb(0x0d, 0x5c, 0x39);
pub const FELT_DARK: Color32 = Color32::from_rgb(0x09, 0x47, 0x2c);
pub const FELT_LINE: Color32 = Color32::from_rgb(0x1f, 0x7d, 0x52);
pub const FELT_TEXT: Color32 = Color32::from_rgb(0xec, 0xf7, 0xf0);
pub const ROULETTE_RED: Color32 = Color32::from_rgb(0xb0, 0x31, 0x3a);
pub const ROULETTE_BLACK: Color32 = Color32::from_rgb(0x15, 0x1b, 0x21);
pub const ROULETTE_ZERO: Color32 = Color32::from_rgb(0x10, 0x6b, 0x45);

// ---------------------------------------------------------------------------
// Spacing, radius, type scale
// ---------------------------------------------------------------------------

pub const SPACE_1: f32 = 4.0;
pub const SPACE_2: f32 = 8.0;
pub const SPACE_3: f32 = 12.0;
pub const SPACE_4: f32 = 16.0;
pub const SPACE_5: f32 = 24.0;

pub const RADIUS_SM: CornerRadius = CornerRadius::same(4);
pub const RADIUS_MD: CornerRadius = CornerRadius::same(8);
pub const RADIUS_LG: CornerRadius = CornerRadius::same(12);

pub const FONT_BODY: f32 = 14.0;
pub const FONT_SMALL: f32 = 12.0;
pub const FONT_LABEL: f32 = 11.0;
pub const FONT_TITLE: f32 = 24.0;
pub const FONT_MONO: f32 = 16.0;

// ---------------------------------------------------------------------------
// Fonts
// ---------------------------------------------------------------------------

/// Open Sans, SIL OFL 1.1. See `assets/fonts/OFL-OpenSans.txt`.
pub const FONT_SANS_BYTES: &[u8] = include_bytes!("../assets/fonts/OpenSans-Regular.ttf");
/// Hack, MIT. See `assets/fonts/LICENSE-Hack.md`.
pub const FONT_MONO_BYTES: &[u8] = include_bytes!("../assets/fonts/Hack-Regular.ttf");

pub fn sans(size: f32) -> FontId {
    FontId::new(size, FontFamily::Proportional)
}

pub fn mono(size: f32) -> FontId {
    FontId::new(size, FontFamily::Monospace)
}

/// A small uppercase label, the terminal's dim section headers.
pub fn label(text: &str) -> RichText {
    RichText::new(text.to_uppercase())
        .font(mono(FONT_LABEL))
        .color(TEXT_DIM)
}

/// Group an amount in threes: 1234567 -> "1 234 567".
pub fn group_digits(amount: i64) -> String {
    let negative = amount < 0;
    let digits = amount.unsigned_abs().to_string();
    let mut grouped = String::with_capacity(digits.len() + digits.len() / 3);
    for (index, character) in digits.chars().enumerate() {
        if index > 0 && (digits.len() - index) % 3 == 0 {
            grouped.push(' ');
        }
        grouped.push(character);
    }
    if negative {
        format!("-{grouped}")
    } else {
        grouped
    }
}

/// `1000` -> `"1 000 Kr"`.
pub fn money(amount: i64) -> String {
    format!("{} Kr", group_digits(amount))
}

/// Net amount with an explicit sign: `"+800 Kr"`, `"-90 Kr"`.
pub fn signed_money(amount: i64) -> String {
    let sign = if amount < 0 { "-" } else { "+" };
    format!("{sign}{} Kr", group_digits(amount.abs()))
}

// ---------------------------------------------------------------------------
// Installation
// ---------------------------------------------------------------------------

/// Install the embedded fonts and the dark style. Call once, from the app
/// constructor, before the first frame.
pub fn install(ctx: &Context) {
    let mut fonts = FontDefinitions::default();
    fonts.font_data.insert(
        "zagan-sans".to_owned(),
        Arc::new(FontData::from_static(FONT_SANS_BYTES)),
    );
    fonts.font_data.insert(
        "zagan-mono".to_owned(),
        Arc::new(FontData::from_static(FONT_MONO_BYTES)),
    );
    fonts
        .families
        .get_mut(&FontFamily::Proportional)
        .expect("proportional family exists")
        .insert(0, "zagan-sans".to_owned());
    fonts
        .families
        .get_mut(&FontFamily::Monospace)
        .expect("monospace family exists")
        .insert(0, "zagan-mono".to_owned());
    ctx.set_fonts(fonts);

    ctx.set_theme(Theme::Dark);
    let mut style = (*ctx.global_style()).clone();
    style.text_styles = [
        (TextStyle::Heading, sans(FONT_TITLE)),
        (TextStyle::Body, sans(FONT_BODY)),
        (TextStyle::Button, sans(FONT_BODY)),
        (TextStyle::Small, sans(FONT_SMALL)),
        (TextStyle::Monospace, mono(FONT_MONO)),
    ]
    .into();
    style.spacing.item_spacing = egui::vec2(SPACE_2, SPACE_2);
    style.spacing.button_padding = egui::vec2(SPACE_3, SPACE_2);
    style.spacing.interact_size = egui::vec2(36.0, 32.0);
    style.spacing.window_margin = Margin::same(SPACE_3 as i8);
    style.visuals = visuals();
    ctx.set_global_style(style);
}

fn widget(
    bg_fill: Color32,
    bg_stroke: Color32,
    fg: Color32,
    corner_radius: CornerRadius,
) -> WidgetVisuals {
    WidgetVisuals {
        bg_fill,
        weak_bg_fill: bg_fill,
        bg_stroke: Stroke::new(1.0, bg_stroke),
        corner_radius,
        fg_stroke: Stroke::new(1.0, fg),
        expansion: 0.0,
    }
}

fn visuals() -> Visuals {
    let mut visuals = Visuals::dark();
    visuals.override_text_color = Some(TEXT);
    visuals.panel_fill = BG;
    visuals.window_fill = SURFACE;
    visuals.window_stroke = Stroke::new(1.0, LINE);
    visuals.window_corner_radius = RADIUS_LG;
    visuals.extreme_bg_color = BG;
    visuals.faint_bg_color = SURFACE_RAISED;
    visuals.code_bg_color = SURFACE_RAISED;
    visuals.hyperlink_color = ACCENT;
    visuals.warn_fg_color = GOLD;
    visuals.error_fg_color = LOSS;
    visuals.selection.bg_fill = ACCENT.gamma_multiply(0.30);
    visuals.selection.stroke = Stroke::new(1.0, ACCENT);
    visuals.widgets.noninteractive = widget(SURFACE, LINE, TEXT, RADIUS_MD);
    visuals.widgets.inactive = widget(SURFACE_RAISED, LINE, TEXT, RADIUS_MD);
    visuals.widgets.hovered = widget(SURFACE_HOVER, ACCENT.gamma_multiply(0.75), TEXT, RADIUS_MD);
    visuals.widgets.active = widget(
        ACCENT.gamma_multiply(0.25),
        ACCENT,
        Color32::WHITE,
        RADIUS_MD,
    );
    visuals.widgets.open = visuals.widgets.active;
    visuals
}