// Bridges under strain: wooden bridges catch fire (fire traps, fire breath, fireballs, lightning),
// the fire spreads along the planks and the bridge collapses into the river; knights wear bridges
// down step by step, pit imps mend them again. Stone bridges over lava never burn.
// Drawbridges are raised and lowered by hand or rise by themselves when enemies come near.
// Frost (the frost glow trap, the frost spell) cools lava into walkable obsidian for a while.

use crate::game::*;
use crate::map::*;
use crate::particles::*;
use serde::{Deserialize, Serialize};

// seconds a burning plank holds before it falls into the river
pub const BURN_TIME: f32 = 6.0;
// a burning plank sets a neighbouring wooden plank alight with this chance per second
pub const BURN_SPREAD: f32 = 0.35;
// fire damage per second to whoever stands on a burning plank
pub const BURN_DPS: f32 = 6.0;
// wear a knight does to a bridge tile per second (1.0 = it falls)
pub const TEAR_RATE: f32 = 0.12;
// wear an imp mends per second
pub const MEND_RATE: f32 = 0.25;
// an automatic drawbridge rises when an enemy comes this close (tiles)
pub const DRAWBRIDGE_WATCH: f32 = 6.0;
// seconds the frost spell keeps lava cooled; the last seconds it steams
pub const FREEZE_TIME: f32 = 40.0;
pub const MELT_WARN: f32 = 5.0;

#[derive(Clone, Debug, Default, Serialize, Deserialize)]
pub struct BridgeWork {
    pub burning: Vec<(usize, f32)>, // tile, seconds it burns already
    pub wear: Vec<(usize, f32)>,    // tile, damage 0..1
    #[serde(default)]
    pub cooled: Vec<(usize, f32)>, // obsidian tile, seconds until it melts
    #[serde(default)]
    pub watch_t: f32, // automatic drawbridges look around twice a second
}

impl Game {
    // a wooden bridge (or wooden drawbridge) that can burn
    pub fn wooden_bridge(&self, i: usize) -> bool {
        self.map.t.get(i).map_or(false, |t| t.kind == Kind::Bridge || (t.kind == Kind::Drawbridge && t.res & DB_LAVA == 0))
    }

    pub fn burning(&self, i: usize) -> bool {
        self.bridgework.burning.iter().any(|b| b.0 == i)
    }

    pub fn wear_of(&self, i: usize) -> f32 {
        self.bridgework.wear.iter().find(|w| w.0 == i).map_or(0.0, |w| w.1)
    }

    // fire reaches tile (x, y): a wooden bridge there starts to burn
    pub fn ignite_at(&mut self, x: f32, y: f32) {
        let (tx, ty) = (x.floor() as i32, y.floor() as i32);
        if !inb(tx, ty) {
            return;
        }
        let i = idx(tx, ty);
        if !self.wooden_bridge(i) || self.burning(i) {
            return;
        }
        self.bridgework.burning.push((i, 0.0));
        self.fx(3, tx as f32 + 0.5, ty as f32 + 0.5, 0.0, 0.0, 0.5, 0xff2080ff);
        if self.map.t[i].owner == self.me {
            self.msg("msg.bridge_fire", vec![]);
            self.hint(32, "hint.bridge_fire");
        }
    }

    // fire along a jet from (x, y) in direction (dx, dy) over `len` tiles
    pub fn ignite_line(&mut self, x: f32, y: f32, dx: f32, dy: f32, len: f32) {
        let steps = (len * 3.0) as usize;
        for s in 1..=steps {
            let f = s as f32 / 3.0;
            self.ignite_at(x + dx * f, y + dy * f);
        }
    }

    // the shared part of every step: fire, collapse, drawbridges, melting obsidian
    pub(crate) fn update_bridges(&mut self, dt: f32) {
        self.update_drawbridges(dt);
        self.update_obsidian(dt);
        if self.bridgework.burning.is_empty() {
            return;
        }
        let mut k = 0;
        while k < self.bridgework.burning.len() {
            let (i, t0) = self.bridgework.burning[k];
            // the plank is gone already (torn down, sold, rebuilt)
            if !self.wooden_bridge(i) {
                self.bridgework.burning.swap_remove(k);
                continue;
            }
            let t = t0 + dt;
            self.bridgework.burning[k].1 = t;
            let (x, y) = xy(i);
            let (fx, fy) = (x as f32 + 0.5, y as f32 + 0.5);
            // flames and smoke (looks only)
            if self.vrng.f() < dt * 14.0 {
                let (ox, oy) = (self.vrng.f() - 0.5, self.vrng.f() - 0.5);
                let v = (self.vrng.f() * 0.4 - 0.2, self.vrng.f() * 0.4 - 0.2, 0.9 + self.vrng.f() * 0.8);
                self.parts.push(Part { kind: EMBER, x: fx + ox * 0.9, y: fy + oy * 0.9, h: 0.15, vx: v.0, vy: v.1, vh: v.2, t: 0.0, max: 0.7, col: abgr(255, 120 + (self.vrng.f() * 80.0) as u8, 30), size: 0.08 });
            }
            if self.vrng.f() < dt * 3.0 {
                self.parts.push(Part { kind: SMOKE, x: fx + self.vrng.f() - 0.5, y: fy + self.vrng.f() - 0.5, h: 0.5, vx: 0.0, vy: 0.0, vh: 0.6, t: 0.0, max: 2.2, col: abgr(40, 34, 30), size: 0.18 });
            }
            // whoever stands in the flames gets burnt
            for j in 0..self.ents.len() {
                let e = &self.ents[j];
                if e.alive && !e.held && !flies(e.kind) && e.tile() == i {
                    self.ents[j].hp -= BURN_DPS * dt;
                    if self.ents[j].hp <= 0.0 {
                        self.kill(j);
                    }
                }
            }
            // the fire spreads along the planks (deterministic: the shared random numbers)
            if t > 1.5 && (t / 1.0).floor() != ((t - dt) / 1.0).floor() {
                for &(dx, dy) in DIR4.iter() {
                    if !inb(x + dx, y + dy) {
                        continue;
                    }
                    let n = idx(x + dx, y + dy);
                    if self.wooden_bridge(n) && !self.burning(n) && self.rng.f() < BURN_SPREAD {
                        self.bridgework.burning.push((n, 0.0));
                    }
                }
            }
            if t >= BURN_TIME {
                self.bridgework.burning.swap_remove(k);
                self.bridge_falls(i);
                continue;
            }
            k += 1;
        }
    }

    // a bridge tile falls into its river: whoever stands there goes into the water (or lava)
    pub(crate) fn bridge_falls(&mut self, i: usize) {
        let t = self.map.t[i];
        if !t.bridge() {
            return;
        }
        let mine = t.owner == self.me;
        let tl = &mut self.map.t[i];
        tl.kind = if t.river() == Some(Kind::Lava) { Kind::Lava } else { Kind::Water };
        tl.owner = Owner::None;
        tl.reserved = 0;
        tl.res = 0;
        self.bridgework.wear.retain(|w| w.0 != i);
        self.bridgework.burning.retain(|w| w.0 != i);
        self.ground_lost(i);
        let (x, y) = xy(i);
        self.fx(6, x as f32 + 0.5, y as f32 + 0.5, 0.0, 0.0, 0.6, 0xff3a5a7a);
        for _ in 0..6 {
            let v = (self.vrng.f() * 2.0 - 1.0, self.vrng.f() * 2.0 - 1.0, 0.6 + self.vrng.f());
            self.parts.push(Part { kind: DEBRIS, x: x as f32 + 0.5, y: y as f32 + 0.5, h: 0.2, vx: v.0, vy: v.1, vh: v.2, t: 0.0, max: 1.2, col: abgr(90, 62, 34), size: 0.08 });
        }
        self.sfx(Sfx::DigDone, x as f32 + 0.5, y as f32 + 0.5);
        if mine {
            self.msg("msg.bridge_torn", vec![]);
        }
    }

    // a knight works on a bridge tile: true while it still stands
    pub(crate) fn wear_bridge(&mut self, i: usize, dt: f32) -> bool {
        let w = self.wear_of(i) + TEAR_RATE * dt;
        if w >= 1.0 {
            self.bridge_falls(i);
            return false;
        }
        match self.bridgework.wear.iter_mut().find(|x| x.0 == i) {
            Some(x) => x.1 = w,
            None => self.bridgework.wear.push((i, w)),
        }
        true
    }

    // an imp mends a worn bridge tile: true while there is more to do
    pub(crate) fn mend_bridge(&mut self, i: usize, dt: f32) -> bool {
        let Some(k) = self.bridgework.wear.iter().position(|x| x.0 == i) else { return false };
        self.bridgework.wear[k].1 -= MEND_RATE * dt;
        if self.bridgework.wear[k].1 <= 0.0 {
            self.bridgework.wear.swap_remove(k);
            return false;
        }
        true
    }

    // a worn (not burning) bridge tile of the master being processed next to or at tile i
    pub(crate) fn worn_bridge_near(&self, i: usize) -> Option<usize> {
        if self.bridgework.wear.is_empty() {
            return None;
        }
        let (x, y) = xy(i);
        std::iter::once((0, 0)).chain(DIR4.iter().copied()).find_map(|(dx, dy)| {
            let n = idx(x + dx, y + dy);
            let ok = inb(x + dx, y + dy) && self.map.t[n].bridge() && self.map.t[n].owner == self.me && self.wear_of(n) > 0.0 && !self.burning(n);
            ok.then_some(n)
        })
    }
}

// ------------------------------------------------------------------ drawbridges and frost
impl Game {
    // the drawbridge tiles connected to tile i (same owner)
    pub fn drawbridge_group(&self, i: usize) -> Vec<usize> {
        let owner = self.map.t[i].owner;
        let mut group = vec![i];
        let mut k = 0;
        while k < group.len() {
            let (x, y) = xy(group[k]);
            for &(dx, dy) in DIR4.iter() {
                if !inb(x + dx, y + dy) {
                    continue;
                }
                let n = idx(x + dx, y + dy);
                let t = &self.map.t[n];
                if t.kind == Kind::Drawbridge && t.owner == owner && !group.contains(&n) {
                    group.push(n);
                }
            }
            k += 1;
        }
        group
    }

    // the drawbridge tool: a click on an own drawbridge switches it (down -> up -> automatic -> down),
    // anything else builds drawbridges like bridges
    pub fn drawbridge_order(&mut self, x0: i32, y0: i32, x1: i32, y1: i32) {
        if x0 == x1 && y0 == y1 && inb(x0, y0) {
            let i = idx(x0, y0);
            let t = self.map.t[i];
            if t.kind == Kind::Drawbridge && t.owner == self.me {
                let state = t.res & (DB_RAISED | DB_AUTO);
                let next = match state {
                    0 => DB_RAISED,
                    s if s & DB_AUTO != 0 => 0,
                    _ => DB_AUTO,
                };
                self.set_drawbridge(i, next);
                let key = match next {
                    DB_RAISED => "msg.drawbridge_up",
                    DB_AUTO => "msg.drawbridge_auto",
                    _ => "msg.drawbridge_down",
                };
                self.msg(key, vec![]);
                self.sfx_ui(Sfx::Click);
                return;
            }
        }
        self.build_bridges_of(x0, y0, x1, y1, true);
    }

    // sets the state bits (DB_RAISED, DB_AUTO) of the whole drawbridge at tile i
    pub fn set_drawbridge(&mut self, i: usize, state: u8) {
        let group = self.drawbridge_group(i);
        let raise = state & DB_RAISED != 0 && !self.map.t[i].raised();
        let lower = state & DB_RAISED == 0 && self.map.t[i].raised();
        for &g in &group {
            let t = &mut self.map.t[g];
            t.res = (t.res & DB_LAVA) | state;
        }
        if raise {
            // whoever stands on it jumps to the bank (or falls)
            for &g in &group {
                self.ground_lost(g);
            }
        }
        if raise || lower {
            let (x, y) = xy(i);
            self.sfx(Sfx::Build, x as f32 + 0.5, y as f32 + 0.5);
            for &g in &group {
                let (gx, gy) = xy(g);
                self.fx(6, gx as f32 + 0.5, gy as f32 + 0.5, 0.0, 0.0, 0.3, 0xff506070);
            }
        }
    }

    // automatic drawbridges rise while an enemy of their master is near, and come down again
    fn update_drawbridges(&mut self, dt: f32) {
        self.bridgework.watch_t -= dt;
        if self.bridgework.watch_t > 0.0 {
            return;
        }
        self.bridgework.watch_t = 0.5;
        let mut seen: Vec<usize> = Vec::new();
        for i in 0..self.map.t.len() {
            let t = self.map.t[i];
            if t.kind != Kind::Drawbridge || t.res & DB_AUTO == 0 || seen.contains(&i) {
                continue;
            }
            let group = self.drawbridge_group(i);
            seen.extend(group.iter().copied());
            let side = t.owner.side();
            let r2 = DRAWBRIDGE_WATCH * DRAWBRIDGE_WATCH;
            let enemy = self.ents.iter().any(|e| {
                e.alive
                    && !e.held
                    && e.captive == 0
                    && !e.chained
                    && e.side() != side
                    && !self.allied(side, e.side())
                    && group.iter().any(|&g| {
                        let (gx, gy) = xy(g);
                        (e.x - gx as f32 - 0.5).powi(2) + (e.y - gy as f32 - 0.5).powi(2) < r2
                    })
            });
            if enemy != t.raised() {
                self.set_drawbridge(i, DB_AUTO | if enemy { DB_RAISED } else { 0 });
                if enemy && t.owner == self.me {
                    self.msg("msg.drawbridge_rises", vec![]);
                }
            }
        }
    }

    // frost on tile i: lava turns to obsidian (or stays it) for at least `secs`
    pub fn cool_lava(&mut self, i: usize, secs: f32) {
        let t = &mut self.map.t[i];
        match t.kind {
            Kind::Lava => {
                t.kind = Kind::Obsidian;
                t.owner = Owner::None;
                self.bridgework.cooled.push((i, secs));
                let (x, y) = xy(i);
                for _ in 0..3 {
                    self.parts.push(Part { kind: SMOKE, x: x as f32 + self.vrng.f(), y: y as f32 + self.vrng.f(), h: 0.1, vx: 0.0, vy: 0.0, vh: 0.5, t: 0.0, max: 1.6, col: abgr(200, 210, 220), size: 0.16 });
                }
            }
            Kind::Obsidian => {
                if let Some(c) = self.bridgework.cooled.iter_mut().find(|c| c.0 == i) {
                    c.1 = c.1.max(secs);
                }
            }
            _ => {}
        }
    }

    // frost in a circle around (x, y)
    pub fn cool_lava_around(&mut self, x: f32, y: f32, r: f32, secs: f32) {
        let ri = r.ceil() as i32;
        let (cx, cy) = (x.floor() as i32, y.floor() as i32);
        for ty in cy - ri..=cy + ri {
            for tx in cx - ri..=cx + ri {
                if inb(tx, ty) && (tx as f32 + 0.5 - x).powi(2) + (ty as f32 + 0.5 - y).powi(2) <= r * r {
                    self.cool_lava(idx(tx, ty), secs);
                }
            }
        }
    }

    // obsidian melts again: it steams before, and whoever still stands there is burnt
    fn update_obsidian(&mut self, dt: f32) {
        let mut k = 0;
        while k < self.bridgework.cooled.len() {
            let (i, left) = self.bridgework.cooled[k];
            if self.map.t[i].kind != Kind::Obsidian {
                self.bridgework.cooled.swap_remove(k);
                continue;
            }
            let left = left - dt;
            self.bridgework.cooled[k].1 = left;
            let (x, y) = xy(i);
            if left < MELT_WARN && self.vrng.f() < dt * 4.0 {
                self.parts.push(Part { kind: SMOKE, x: x as f32 + self.vrng.f(), y: y as f32 + self.vrng.f(), h: 0.05, vx: 0.0, vy: 0.0, vh: 0.4, t: 0.0, max: 1.4, col: abgr(150, 150, 160), size: 0.14 });
            }
            if left <= 0.0 {
                self.bridgework.cooled.swap_remove(k);
                self.map.t[i].kind = Kind::Lava;
                self.ground_lost(i);
                continue;
            }
            k += 1;
        }
    }
}

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

    // a wooden bridge of the player across a strip of water, 6 tiles long
    fn bridge_game() -> (Game, Vec<usize>) {
        let mut g = Game::new(5, 64, 64);
        let (cx, cy) = g.map.core;
        let y = cy + 6;
        let mut tiles = Vec::new();
        for x in cx - 3..cx + 3 {
            let i = idx(x, y);
            g.map.t[i].kind = Kind::Bridge;
            g.map.t[i].owner = Owner::Player;
            for dy in [-1, 1] {
                let t = &mut g.map.t[idx(x, y + dy)];
                t.kind = Kind::Water;
                t.owner = Owner::None;
            }
            tiles.push(i);
        }
        (g, tiles)
    }

    #[test]
    fn a_burning_bridge_spreads_and_falls() {
        let (mut g, tiles) = bridge_game();
        let (x, y) = xy(tiles[2]);
        g.ignite_at(x as f32 + 0.5, y as f32 + 0.5);
        assert!(g.burning(tiles[2]));
        for _ in 0..(20 * 20) {
            g.update(0.05);
        }
        assert_eq!(g.map.t[tiles[2]].kind, Kind::Water, "the burnt plank fell");
        assert!(tiles.iter().filter(|&&i| g.map.t[i].kind == Kind::Water).count() >= 2, "the fire spread");
        assert!(g.bridgework.burning.iter().all(|b| g.wooden_bridge(b.0)));
    }

    #[test]
    fn stone_bridges_do_not_burn() {
        let (mut g, tiles) = bridge_game();
        g.map.t[tiles[0]].kind = Kind::LavaBridge;
        let (x, y) = xy(tiles[0]);
        g.ignite_at(x as f32 + 0.5, y as f32 + 0.5);
        assert!(!g.burning(tiles[0]));
    }

    #[test]
    fn worn_bridges_fall_or_are_mended() {
        let (mut g, tiles) = bridge_game();
        assert!(g.wear_bridge(tiles[1], 2.0));
        assert!(g.wear_of(tiles[1]) > 0.2);
        assert_eq!(g.worn_bridge_near(tiles[1]), Some(tiles[1]));
        while g.mend_bridge(tiles[1], 0.5) {}
        assert_eq!(g.wear_of(tiles[1]), 0.0);
        while g.wear_bridge(tiles[1], 1.0) {}
        assert_eq!(g.map.t[tiles[1]].kind, Kind::Water);
    }

    #[test]
    fn drawbridges_switch_and_rise_by_themselves() {
        let (mut g, tiles) = bridge_game();
        for &i in &tiles {
            g.map.t[i].kind = Kind::Drawbridge;
            g.map.t[i].res = 0;
        }
        let (x, y) = xy(tiles[2]);
        g.drawbridge_order(x, y, x, y);
        assert!(tiles.iter().all(|&i| g.map.t[i].raised()), "the whole bridge goes up");
        assert!(!g.map.walk(x, y));
        g.drawbridge_order(x, y, x, y);
        assert!(tiles.iter().all(|&i| g.map.t[i].res & DB_AUTO != 0 && !g.map.t[i].raised()), "automatic");
        // a knight comes near: it rises
        let id = g.spawn(EK::Knight, true, x as f32 + 0.5, y as f32 + 3.5, 1);
        for _ in 0..20 {
            g.update(0.05);
        }
        assert!(g.map.t[tiles[2]].raised(), "risen for the knight");
        g.ents.retain(|e| e.id != id);
        for _ in 0..20 {
            g.update(0.05);
        }
        assert!(!g.map.t[tiles[2]].raised(), "down again");
        g.drawbridge_order(x, y, x, y);
        assert_eq!(g.map.t[tiles[2]].res & (DB_RAISED | DB_AUTO), 0, "back to manual, down");
    }

    #[test]
    fn frost_cools_lava_for_a_while() {
        let mut g = Game::new(5, 64, 64);
        let (cx, cy) = g.map.core;
        let i = idx(cx + 6, cy + 6);
        g.map.t[i].kind = Kind::Lava;
        g.cool_lava(i, 2.0);
        assert_eq!(g.map.t[i].kind, Kind::Obsidian);
        assert!(g.map.t[i].walkable());
        for _ in 0..(3 * 20) {
            g.update(0.05);
        }
        assert_eq!(g.map.t[i].kind, Kind::Lava, "melted again");
    }
}