// Particles: trails that fall to the ground behind projectiles, explosions of fireballs and
// cannonballs, bursts of the spells, debris and coins, scorch marks, and arrows that stay stuck
// in walls and the ground for five minutes. Purely visual: never saved, with their own random
// numbers (the game's random sequence stays untouched).

use crate::game::*;
use crate::map::*;

pub const STUCK_MAX: usize = 400; // arrows and scorch marks
pub const STUCK_LIFE: f32 = 300.0; // seconds an arrow stays
const PARTS_MAX: usize = 900;
const GRAVITY: f32 = 6.0;

// particle kinds
pub const EMBER: u8 = 0; // glowing, falls
pub const SMOKE: u8 = 1; // rises and grows
pub const SPARK: u8 = 2; // glowing, falls fast, bounces once
pub const DEBRIS: u8 = 3; // solid chunk, falls and rests a moment
pub const MOTE: u8 = 4; // glowing, floats up slowly
pub const COIN: u8 = 5; // solid gold, bounces
pub const ARROW: u8 = 6; // stuck arrow (vx, vy, vh = its direction)
pub const SCORCH: u8 = 7; // dark mark on the floor
pub const FLASH: u8 = 8; // expanding fireball
pub const RING: u8 = 9; // shock wave

// projectile styles (Fx::style)
pub const ST_PLAIN: u8 = 0;
pub const ST_ARROW: u8 = 1;
pub const ST_CANNON: u8 = 2;
pub const ST_FIRE: u8 = 3;
pub const ST_SHADOW: u8 = 4;
pub const ST_HOLY: u8 = 5;
pub const ST_ARCANE: u8 = 6;
pub const ST_RUNE: u8 = 7;
pub const ST_MAGIC: u8 = 8;
pub const ST_ARROW_WALL: u8 = 9; // an arrow that ends in a wall

#[derive(Clone, Copy, Debug)]
pub struct Part {
    pub kind: u8,
    pub x: f32,
    pub y: f32,
    pub h: f32,
    pub vx: f32,
    pub vy: f32,
    pub vh: f32,
    pub t: f32,
    pub max: f32,
    pub col: u32,
    pub size: f32,
}

pub fn vrng() -> Rng {
    Rng(0x2545_f491)
}

// colour as 0xAABBGGRR (like Fx::col)
pub const fn abgr(r: u8, g: u8, b: u8) -> u32 {
    0xff00_0000 | (b as u32) << 16 | (g as u32) << 8 | r as u32
}

// position of a projectile at progress p (cannonballs and fireballs fly in an arc)
pub fn fx_pos(f: &Fx, p: f32) -> (f32, f32, f32) {
    let p = p.clamp(0.0, 1.0);
    let x = f.x + (f.x2 - f.x) * p;
    let y = f.y + (f.y2 - f.y) * p;
    let dist = ((f.x2 - f.x).powi(2) + (f.y2 - f.y).powi(2)).sqrt();
    let arc = match f.style {
        ST_CANNON => 0.22,
        ST_FIRE => 0.12,
        ST_ARROW | ST_ARROW_WALL => 0.04,
        _ => 0.0,
    } * dist;
    let h = f.h + (f.h2 - f.h) * p + arc * (p * std::f32::consts::PI).sin();
    (x, y, h)
}

impl Game {
    pub(crate) fn part(&mut self, kind: u8, (x, y, h): (f32, f32, f32), (vx, vy, vh): (f32, f32, f32), max: f32, col: u32, size: f32) {
        if self.parts.len() < PARTS_MAX {
            self.parts.push(Part { kind, x, y, h, vx, vy, vh, t: 0.0, max, col, size });
        }
    }

    fn stick(&mut self, p: Part) {
        if self.stuck.len() >= STUCK_MAX {
            self.stuck.remove(0);
        }
        self.stuck.push(p);
    }

    // a random direction with the given speed (upwards bias `up`)
    fn burst_vel(&mut self, speed: f32, up: f32) -> (f32, f32, f32) {
        let a = self.vrng.f() * std::f32::consts::TAU;
        let s = speed * (0.4 + 0.6 * self.vrng.f());
        (a.cos() * s, a.sin() * s, up * (0.5 + self.vrng.f()))
    }

    fn burst(&mut self, kind: u8, at: (f32, f32, f32), n: usize, speed: f32, up: f32, max: f32, col: u32, size: f32) {
        for _ in 0..n {
            let v = self.burst_vel(speed, up);
            let m = max * (0.6 + 0.6 * self.vrng.f());
            let sz = size * (0.7 + 0.6 * self.vrng.f());
            self.part(kind, at, v, m, col, sz);
        }
    }

    // particles that come with a new effect (spells, hits, digging, gold, ...)
    pub(crate) fn fx_particles(&mut self, kind: u8, x: f32, y: f32, h: f32, col: u32) {
        match kind {
            // lightning: a shower of sparks, smoke and a burnt spot
            1 => {
                self.burst(SPARK, (x, y, 0.1), 40, 3.5, 3.5, 1.0, abgr(255, 250, 200), 0.05);
                self.burst(SMOKE, (x, y, 0.2), 6, 0.4, 0.6, 2.0, abgr(90, 90, 100), 0.25);
                self.part(FLASH, (x, y, 0.3), (0.0, 0.0, 0.0), 0.35, abgr(255, 255, 220), 1.0);
                self.stick(Part { kind: SCORCH, x, y, h: 0.0, vx: 0.0, vy: 0.0, vh: 0.0, t: 0.0, max: 20.0, col: 0, size: 0.8 });
            }
            // hit: a few sparks of the effect's colour
            2 => self.burst(SPARK, (x, y, h.max(0.3)), 5, 1.5, 1.5, 0.5, col, 0.035),
            3 => self.burst(SMOKE, (x, y, 0.3), 4, 0.3, 0.5, 1.6, abgr(80, 80, 90), 0.2),
            // healing: green motes rising in a spiral, sparkles falling
            4 => {
                for k in 0..12 {
                    let a = k as f32 * 0.52;
                    self.part(MOTE, (x + a.cos() * 0.3, y + a.sin() * 0.3, 0.1 + k as f32 * 0.03), (-a.sin() * 0.3, a.cos() * 0.3, 0.9), 1.3, abgr(120, 255, 140), 0.05);
                }
                self.burst(EMBER, (x, y, 0.9), 6, 0.6, 0.5, 1.0, abgr(200, 255, 200), 0.03);
            }
            // gold: coins pop up and fall
            5 => self.burst(COIN, (x, y, 0.4), 5, 1.2, 2.5, 1.6, abgr(255, 210, 60), 0.06),
            // digging: earth chunks
            6 => self.burst(DEBRIS, (x, y, 0.5), 4, 1.2, 1.5, 1.4, abgr(110, 80, 56), 0.06),
            // level up, spells, specials: sparkles in the effect's colour shoot up and rain down
            7 => self.burst(EMBER, (x, y, 0.5), 18, 1.6, 3.0, 1.4, col, 0.04),
            // claiming: a puff of dust
            8 => self.burst(SMOKE, (x, y, 0.1), 2, 0.3, 0.2, 0.8, abgr(120, 60, 60), 0.12),
            _ => {}
        }
    }

    // advances projectiles (trails, impacts) and particles
    pub(crate) fn update_particles(&mut self, dt: f32) {
        // trails and impacts of the projectiles
        let mut trails: Vec<(u8, (f32, f32, f32), f32)> = Vec::new();
        let mut impacts: Vec<Fx> = Vec::new();
        for f in self.fx.iter() {
            if f.kind != 0 {
                continue;
            }
            let p0 = f.t / f.max;
            let p1 = (f.t + dt) / f.max;
            if p0 < 1.0 {
                trails.push((f.style, fx_pos(f, p1.min(1.0)), f.size));
            }
            if p0 < 1.0 && p1 >= 1.0 {
                impacts.push(*f);
            }
        }
        for (style, at, size) in trails {
            let (rate, kind, col, psize, life) = match style {
                ST_FIRE => (70.0, EMBER, abgr(255, 150, 40), 0.045, 0.9),
                ST_SHADOW => (45.0, EMBER, abgr(200, 70, 255), 0.035, 1.0),
                ST_HOLY => (35.0, MOTE, abgr(255, 240, 150), 0.03, 0.8),
                ST_ARCANE => (40.0, EMBER, abgr(255, 170, 90), 0.03, 0.9),
                ST_RUNE => (45.0, SPARK, abgr(90, 200, 255), 0.03, 0.7),
                ST_MAGIC => (45.0, EMBER, abgr(255, 90, 220), 0.035, 0.9),
                ST_CANNON => (30.0, SMOKE, abgr(70, 70, 76), 0.1, 0.9),
                ST_ARROW | ST_ARROW_WALL => (0.0, EMBER, 0, 0.0, 0.0),
                _ => (12.0, EMBER, abgr(180, 210, 230), 0.03, 0.6),
            };
            let n = rate * dt * size;
            let mut count = n.floor() as usize;
            if self.vrng.f() < n.fract() {
                count += 1;
            }
            for _ in 0..count {
                let v = (self.vrng.f() * 0.6 - 0.3, self.vrng.f() * 0.6 - 0.3, if kind == SMOKE { 0.3 } else { 0.2 });
                let j = (self.vrng.f() * 0.06 - 0.03, self.vrng.f() * 0.06 - 0.03);
                let m = life * (0.7 + 0.6 * self.vrng.f());
                self.part(kind, (at.0 + j.0, at.1 + j.1, at.2), v, m, col, psize * size.sqrt());
            }
            if style == ST_FIRE && self.vrng.f() < 12.0 * dt {
                self.part(SMOKE, at, (0.0, 0.0, 0.4), 1.2, abgr(60, 50, 50), 0.12);
            }
        }
        for f in impacts {
            self.impact(&f);
        }
        // particles
        for p in self.parts.iter_mut() {
            p.t += dt;
            match p.kind {
                SMOKE => {
                    p.x += p.vx * dt;
                    p.y += p.vy * dt;
                    p.h += p.vh * dt;
                    p.vx *= 1.0 - dt;
                    p.vy *= 1.0 - dt;
                    p.size += dt * 0.35;
                }
                MOTE => {
                    p.x += p.vx * dt;
                    p.y += p.vy * dt;
                    p.h += p.vh * dt;
                }
                FLASH | RING => {}
                _ => {
                    // falling: embers drift down slower than sparks and debris
                    let g = if p.kind == EMBER { GRAVITY * 0.35 } else { GRAVITY };
                    p.vh -= g * dt;
                    p.x += p.vx * dt;
                    p.y += p.vy * dt;
                    p.h += p.vh * dt;
                    if p.h <= 0.02 {
                        p.h = 0.02;
                        if matches!(p.kind, SPARK | COIN) && p.vh < -1.0 {
                            p.vh = -p.vh * 0.35;
                            p.vx *= 0.5;
                            p.vy *= 0.5;
                        } else {
                            p.vh = 0.0;
                            p.vx *= 0.8;
                            p.vy *= 0.8;
                        }
                    }
                }
            }
        }
        self.parts.retain(|p| p.t < p.max);
        // stuck arrows fall out when their wall is dug away; everything fades in the end
        let map = &self.map;
        for p in self.stuck.iter_mut() {
            p.t += dt;
            if p.kind == ARROW && p.h > 0.1 {
                let (tx, ty) = ((p.x + p.vx * 0.08) as i32, (p.y + p.vy * 0.08) as i32);
                if !map.get(tx, ty).map_or(false, |t| t.solid()) {
                    p.t = p.max;
                }
            }
        }
        self.stuck.retain(|p| p.t < p.max);
    }

    fn impact(&mut self, f: &Fx) {
        let size = f.size;
        let (x, y) = (f.x2, f.y2);
        match f.style {
            ST_FIRE => {
                // the fireball explodes on the ground
                let at = (x, y, 0.15);
                self.part(FLASH, at, (0.0, 0.0, 0.0), 0.45, abgr(255, 170, 60), 0.9 * size);
                self.part(RING, (x, y, 0.05), (0.0, 0.0, 0.0), 0.5, abgr(255, 120, 40), 1.4 * size);
                self.burst(EMBER, at, (24.0 * size) as usize, 2.8 * size, 3.0, 1.2, abgr(255, 140, 40), 0.05);
                self.burst(SPARK, at, 10, 3.5, 2.5, 0.7, abgr(255, 230, 120), 0.035);
                self.burst(SMOKE, (x, y, 0.3), 8, 0.6, 0.7, 2.2, abgr(70, 60, 60), 0.22);
                self.stick(Part { kind: SCORCH, x, y, h: 0.0, vx: 0.0, vy: 0.0, vh: 0.0, t: 0.0, max: 25.0, col: 0, size: 0.7 * size });
            }
            ST_CANNON => {
                // the ball explodes: flash, stones and dirt flying, smoke
                let at = (x, y, 0.2);
                self.part(FLASH, at, (0.0, 0.0, 0.0), 0.3, abgr(255, 200, 120), 0.7 * size);
                self.part(RING, (x, y, 0.05), (0.0, 0.0, 0.0), 0.4, abgr(220, 200, 170), 1.6);
                self.burst(DEBRIS, at, 16, 3.0, 3.5, 1.6, abgr(84, 70, 64), 0.07);
                self.burst(DEBRIS, at, 6, 2.5, 3.0, 1.4, abgr(120, 92, 70), 0.05);
                self.burst(SPARK, at, 12, 4.0, 2.5, 0.6, abgr(255, 200, 100), 0.03);
                self.burst(SMOKE, (x, y, 0.3), 10, 0.8, 0.6, 2.4, abgr(80, 80, 86), 0.25);
                self.stick(Part { kind: SCORCH, x, y, h: 0.0, vx: 0.0, vy: 0.0, vh: 0.0, t: 0.0, max: 20.0, col: 0, size: 0.6 });
            }
            ST_ARROW | ST_ARROW_WALL => {
                let (dx, dy) = (f.x2 - f.x, f.y2 - f.y);
                let l = (dx * dx + dy * dy).sqrt().max(0.01);
                let (dx, dy) = (dx / l, dy / l);
                if f.style == ST_ARROW_WALL {
                    self.burst(DEBRIS, (x, y, f.h2), 3, 0.8, 1.0, 0.8, abgr(110, 90, 80), 0.04);
                    let h = f.h2 + self.vrng.f() * 0.2;
                    self.stick(Part { kind: ARROW, x, y, h, vx: dx, vy: dy, vh: -0.08, t: 0.0, max: STUCK_LIFE, col: 0, size: 1.0 });
                } else if self.vrng.f() < 0.35 {
                    // glanced off: stuck in the floor next to the target
                    let (ox, oy) = (self.vrng.f() * 0.7 - 0.35, self.vrng.f() * 0.7 - 0.35);
                    let tilt = -0.6 - self.vrng.f() * 0.6;
                    let n = (1.0 + tilt * tilt).sqrt();
                    self.stick(Part { kind: ARROW, x: x + ox, y: y + oy, h: 0.04, vx: dx / n, vy: dy / n, vh: tilt / n, t: 0.0, max: STUCK_LIFE, col: 0, size: 1.0 });
                }
            }
            ST_SHADOW => self.burst(EMBER, (x, y, f.h2), 14, 1.6, 1.5, 0.9, abgr(190, 70, 255), 0.04),
            ST_HOLY => self.burst(MOTE, (x, y, f.h2), 12, 0.8, 0.8, 0.8, abgr(255, 240, 160), 0.035),
            ST_ARCANE => self.burst(EMBER, (x, y, f.h2), 14, 1.8, 1.5, 0.8, abgr(255, 180, 100), 0.035),
            ST_RUNE => {
                self.burst(SPARK, (x, y, f.h2), 16, 2.5, 2.0, 0.7, abgr(110, 210, 255), 0.035);
                self.part(FLASH, (x, y, f.h2), (0.0, 0.0, 0.0), 0.2, abgr(150, 220, 255), 0.4);
            }
            ST_MAGIC => self.burst(EMBER, (x, y, f.h2), 14, 1.8, 1.5, 0.9, abgr(255, 100, 220), 0.04),
            _ => self.burst(SPARK, (x, y, f.h2), 6, 1.5, 1.2, 0.5, f.col, 0.03),
        }
    }

    // the last projectile gets a style
    pub(crate) fn style_last_fx(&mut self, style: u8) {
        if let Some(f) = self.fx.last_mut() {
            f.style = style;
        }
    }

    // where an arrow flying from (x, y) along (dx, dy) ends: the first wall within `max`
    pub(crate) fn arrow_end(&self, x: f32, y: f32, dx: f32, dy: f32, max: f32) -> (f32, f32, bool) {
        let mut d = 0.0;
        while d < max {
            d += 0.1;
            let (px, py) = (x + dx * d, y + dy * d);
            if self.map.get(px as i32, py as i32).map_or(true, |t| t.solid()) {
                let back = (d - 0.12).max(0.0);
                return (x + dx * back, y + dy * back, true);
            }
        }
        (x + dx * max, y + dy * max, false)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn projectiles_trail_and_explode_and_arrows_stick() {
        let mut g = Game::new(3, 64, 64);
        let (cx, cy) = g.map.core;
        let (x, y) = (cx as f32 + 1.5, cy as f32 - 1.5);
        g.shot(x, y, 0.5, x + 3.0, y, 0.45, 0.3, 0xffffffff);
        g.style_last_fx(ST_FIRE);
        let (ex, ey, wall) = g.arrow_end(x, y, -1.0, 0.0, 20.0);
        assert!(wall);
        g.shot(x, y, 0.5, ex, ey, 0.45, 0.3, 0xffffffff);
        g.style_last_fx(ST_ARROW_WALL);
        let mut trail = 0;
        for _ in 0..4 {
            g.update(0.05);
            trail = trail.max(g.parts.len());
        }
        assert!(trail > 3, "fire trail: {}", trail);
        for _ in 0..6 {
            g.update(0.05);
        }
        assert!(g.parts.iter().any(|p| p.kind == FLASH) || g.stuck.iter().any(|p| p.kind == SCORCH), "explosion");
        assert!(g.stuck.iter().any(|p| p.kind == ARROW), "arrow stuck");
        // particles fall to the ground and vanish
        for _ in 0..200 {
            g.update(0.05);
        }
        assert!(g.parts.iter().all(|p| p.h >= 0.0));
        assert!(g.parts.len() < 5);
        assert!(g.stuck.iter().any(|p| p.kind == ARROW), "arrows stay for minutes");
    }
}