use std::fmt::Write;

pub const W: usize = 96;
pub const H: usize = 64;
pub const DAY: u64 = 1800;

const WATER_DEEP: u8 = 0;
const WATER: u8 = 1;
const SAND: u8 = 2;
const GRASS: u8 = 3;
const FOREST: u8 = 4;
const HILLS: u8 = 5;
const MOUNTAIN: u8 = 6;

const TREE: u8 = 1;
const BERRY: u8 = 2;
const STONE: u8 = 3;

pub struct Rng(u64);

impl Rng {
    fn next(&mut self) -> u64 {
        let mut x = self.0;
        x ^= x >> 12;
        x ^= x << 25;
        x ^= x >> 27;
        self.0 = x;
        x.wrapping_mul(0x2545F4914F6CDD1D)
    }
    fn f(&mut self) -> f32 {
        (self.next() >> 40) as f32 / (1u64 << 24) as f32
    }
    fn chance(&mut self, p: f32) -> bool {
        self.f() < p
    }
    fn below(&mut self, n: usize) -> usize {
        (self.next() % n as u64) as usize
    }
}

fn hash(x: i32, y: i32, seed: u64) -> f32 {
    let mut h = (x as u64).wrapping_mul(0x9E3779B97F4A7C15)
        ^ (y as u64).wrapping_mul(0xC2B2AE3D27D4EB4F)
        ^ seed.wrapping_mul(0x165667B19E3779F9);
    h ^= h >> 33;
    h = h.wrapping_mul(0xFF51AFD7ED558CCD);
    h ^= h >> 33;
    (h >> 40) as f32 / (1u64 << 24) as f32
}

fn value_noise(x: f32, y: f32, seed: u64) -> f32 {
    let (xi, yi) = (x.floor() as i32, y.floor() as i32);
    let (fx, fy) = (x - xi as f32, y - yi as f32);
    let s = |t: f32| t * t * (3.0 - 2.0 * t);
    let (u, v) = (s(fx), s(fy));
    let a = hash(xi, yi, seed);
    let b = hash(xi + 1, yi, seed);
    let c = hash(xi, yi + 1, seed);
    let d = hash(xi + 1, yi + 1, seed);
    let top = a + (b - a) * u;
    let bot = c + (d - c) * u;
    top + (bot - top) * v
}

fn fbm(x: f32, y: f32, seed: u64) -> f32 {
    let (mut sum, mut amp, mut freq, mut norm) = (0.0, 1.0, 1.0 / 16.0, 0.0);
    for o in 0..4 {
        sum += amp * value_noise(x * freq, y * freq, seed + o);
        norm += amp;
        amp *= 0.5;
        freq *= 2.0;
    }
    sum / norm
}

#[derive(Clone)]
pub struct Person {
    id: u32,
    x: usize,
    y: usize,
    hunger: f32,
    food: u32,
    wood: u32,
    stone: u32,
    action: &'static str,
    dead: bool,
}

impl Person {
    fn carry(&self) -> u32 {
        self.food + self.wood + self.stone
    }
}

#[derive(Clone)]
pub struct Animal {
    x: usize,
    y: usize,
    energy: f32,
    dead: bool,
}

pub struct World {
    tiles: Vec<u8>,
    res: Vec<(u8, u16)>,
    people: Vec<Person>,
    rabbits: Vec<Animal>,
    wolves: Vec<Animal>,
    houses: Vec<(usize, usize)>,
    home: (usize, usize),
    food: u32,
    wood: u32,
    stone: u32,
    tools: u32,
    rng: Rng,
    tick: u64,
    next_id: u32,
    log: Vec<String>,
}

fn cheb(a: (usize, usize), b: (usize, usize)) -> usize {
    a.0.abs_diff(b.0).max(a.1.abs_diff(b.1))
}

impl World {
    pub fn new(seed: u64) -> World {
        let mut tiles = vec![0u8; W * H];
        for y in 0..H {
            for x in 0..W {
                let dx = (x as f32 / W as f32 - 0.5) * 2.0;
                let dy = (y as f32 / H as f32 - 0.5) * 2.0;
                let d = (dx * dx + dy * dy).min(1.5);
                let h = fbm(x as f32, y as f32, seed) + 0.25 - 0.55 * d;
                let m = fbm(x as f32 + 500.0, y as f32 + 500.0, seed + 99);
                tiles[y * W + x] = if h < 0.28 {
                    WATER_DEEP
                } else if h < 0.36 {
                    WATER
                } else if h < 0.41 {
                    SAND
                } else if h < 0.68 {
                    if m > 0.52 { FOREST } else { GRASS }
                } else if h < 0.78 {
                    HILLS
                } else {
                    MOUNTAIN
                };
            }
        }
        let mut w = World {
            tiles,
            res: vec![(0, 0); W * H],
            people: vec![],
            rabbits: vec![],
            wolves: vec![],
            houses: vec![],
            home: (W / 2, H / 2),
            food: 4,
            wood: 0,
            stone: 0,
            tools: 0,
            rng: Rng(seed.wrapping_mul(0x9E3779B97F4A7C15) | 1),
            tick: DAY / 4,
            next_id: 1,
            log: vec![],
        };
        w.home = w
            .find_land(GRASS)
            .unwrap_or_else(|| w.find_land(SAND).unwrap_or((W / 2, H / 2)));
        for i in 0..W * H {
            let r = w.rng.f();
            w.res[i] = match w.tiles[i] {
                FOREST if r < 0.6 => (TREE, 5),
                GRASS if r < 0.04 => (BERRY, 4),
                HILLS if r < 0.15 => (STONE, 6),
                _ => (0, 0),
            };
        }
        let (hx, hy) = w.home;
        w.res[hy * W + hx] = (0, 0);
        for _ in 0..6 {
            w.spawn_person();
        }
        for _ in 0..60 {
            if let Some(p) = w.random_land() {
                w.rabbits.push(Animal {
                    x: p.0,
                    y: p.1,
                    energy: 70.0,
                    dead: false,
                });
            }
        }
        for _ in 0..4 {
            if let Some(p) = w.random_land() {
                if cheb(p, w.home) > 15 {
                    w.wolves.push(Animal {
                        x: p.0,
                        y: p.1,
                        energy: 70.0,
                        dead: false,
                    });
                }
            }
        }
        w
    }

    fn find_land(&self, kind: u8) -> Option<(usize, usize)> {
        let c = (W / 2, H / 2);
        let mut best: Option<(usize, usize)> = None;
        for y in 0..H {
            for x in 0..W {
                if self.tiles[y * W + x] == kind
                    && best.is_none_or(|b| cheb((x, y), c) < cheb(b, c))
                {
                    best = Some((x, y));
                }
            }
        }
        best
    }

    fn random_land(&mut self) -> Option<(usize, usize)> {
        for _ in 0..50 {
            let (x, y) = (self.rng.below(W), self.rng.below(H));
            if self.walkable(x as i32, y as i32) {
                return Some((x, y));
            }
        }
        None
    }

    fn spawn_person(&mut self) {
        let (x, y) = self.home;
        self.people.push(Person {
            id: self.next_id,
            x,
            y,
            hunger: 10.0,
            food: 0,
            wood: 0,
            stone: 0,
            action: "idle",
            dead: false,
        });
        self.next_id += 1;
    }

    fn say(&mut self, s: String) {
        self.log
            .push(format!("[day {}] {}", self.tick / DAY + 1, s));
        if self.log.len() > 8 {
            self.log.remove(0);
        }
    }

    pub fn daylight(&self) -> f32 {
        let phase = (self.tick % DAY) as f32 / DAY as f32;
        let v = -(phase * std::f32::consts::TAU).cos();
        (0.5 + v * 0.8).clamp(0.0, 1.0)
    }

    fn walkable(&self, x: i32, y: i32) -> bool {
        if x < 0 || y < 0 || x >= W as i32 || y >= H as i32 {
            return false;
        }
        matches!(
            self.tiles[y as usize * W + x as usize],
            SAND | GRASS | FOREST | HILLS
        )
    }

    fn move_dir(&mut self, x: usize, y: usize, dx: i32, dy: i32) -> (usize, usize) {
        for (a, b) in [(dx, dy), (dx, 0), (0, dy)] {
            if (a, b) != (0, 0) && self.walkable(x as i32 + a, y as i32 + b) {
                return ((x as i32 + a) as usize, (y as i32 + b) as usize);
            }
        }
        self.wander(x, y)
    }

    fn wander(&mut self, x: usize, y: usize) -> (usize, usize) {
        for _ in 0..4 {
            let (a, b) = (self.rng.below(3) as i32 - 1, self.rng.below(3) as i32 - 1);
            if (a, b) != (0, 0) && self.walkable(x as i32 + a, y as i32 + b) {
                return ((x as i32 + a) as usize, (y as i32 + b) as usize);
            }
        }
        (x, y)
    }

    fn move_toward(&mut self, from: (usize, usize), to: (usize, usize)) -> (usize, usize) {
        let dx = (to.0 as i32 - from.0 as i32).signum();
        let dy = (to.1 as i32 - from.1 as i32).signum();
        self.move_dir(from.0, from.1, dx, dy)
    }

    fn nearest_res(&self, from: (usize, usize), kind: u8, r: usize) -> Option<(usize, usize)> {
        let mut best: Option<(usize, usize)> = None;
        let (x0, x1) = (from.0.saturating_sub(r), (from.0 + r).min(W - 1));
        let (y0, y1) = (from.1.saturating_sub(r), (from.1 + r).min(H - 1));
        for y in y0..=y1 {
            for x in x0..=x1 {
                if self.res[y * W + x].0 == kind
                    && best.is_none_or(|b| cheb((x, y), from) < cheb(b, from))
                {
                    best = Some((x, y));
                }
            }
        }
        best
    }

    fn nearest_animal(list: &[Animal], from: (usize, usize), r: usize) -> Option<usize> {
        let mut best: Option<(usize, usize)> = None;
        for (i, a) in list.iter().enumerate() {
            let d = cheb((a.x, a.y), from);
            if !a.dead && d <= r && best.is_none_or(|(_, bd)| d < bd) {
                best = Some((i, d));
            }
        }
        best.map(|b| b.0)
    }

    pub fn step(&mut self) {
        self.tick += 1;
        self.regrow();
        if self.tick % 2 == 0 {
            for i in 0..self.people.len() {
                self.tick_person(i);
            }
            for i in 0..self.rabbits.len() {
                self.tick_rabbit(i);
            }
        } else {
            for i in 0..self.wolves.len() {
                self.tick_wolf(i);
            }
        }
        self.people.retain(|p| !p.dead);
        self.rabbits.retain(|a| !a.dead);
        self.wolves.retain(|a| !a.dead);
        self.population();
    }

    fn regrow(&mut self) {
        for _ in 0..20 {
            let i = self.rng.below(W * H);
            if self.res[i].0 != 0 {
                continue;
            }
            let p = self.rng.f();
            match self.tiles[i] {
                FOREST if p < 0.02 => self.res[i] = (TREE, 5),
                GRASS if p < 0.02 => self.res[i] = (BERRY, 4),
                HILLS if p < 0.004 => self.res[i] = (STONE, 6),
                _ => {}
            }
        }
    }

    fn population(&mut self) {
        if self.tick % 400 == 0 && self.food >= 10 && self.people.len() < 8 + self.houses.len() * 3
        {
            self.food -= 6;
            self.spawn_person();
            self.say("A child was born".into());
        }
        if self.tick % 50 == 0 {
            if self.rabbits.len() < 15 {
                if let Some(p) = self.random_land() {
                    self.rabbits.push(Animal {
                        x: p.0,
                        y: p.1,
                        energy: 70.0,
                        dead: false,
                    });
                }
            }
            if self.wolves.len() < 2 && self.rabbits.len() > 40 {
                if let Some(p) = self.random_land() {
                    if cheb(p, self.home) > 15 {
                        self.wolves.push(Animal {
                            x: p.0,
                            y: p.1,
                            energy: 70.0,
                            dead: false,
                        });
                    }
                }
            }
        }
    }

    fn tick_person(&mut self, i: usize) {
        let mut p = self.people[i].clone();
        let night = self.daylight() < 0.2;
        let pos = (p.x, p.y);
        let at_home = cheb(pos, self.home) <= 1;
        p.hunger += if night && at_home { 0.04 } else { 0.1 };
        if p.hunger >= 100.0 {
            p.dead = true;
            self.say(format!("Person #{} starved", p.id));
            self.people[i] = p;
            return;
        }
        if at_home {
            self.food += p.food;
            self.wood += p.wood;
            self.stone += p.stone;
            p.food = 0;
            p.wood = 0;
            p.stone = 0;
            if p.hunger > 40.0 && self.food > 0 {
                self.food -= 1;
                p.hunger = (p.hunger - 25.0).max(0.0);
            }
            if self.wood >= 3 && self.stone >= 1 && self.tools < self.people.len() as u32 {
                self.wood -= 3;
                self.stone -= 1;
                self.tools += 1;
            }
            if self.wood >= 12 && self.stone >= 4 && self.houses.len() < 10 {
                let (hx, hy) = self.home;
                let x = (hx as i32 + self.rng.below(13) as i32 - 6).clamp(0, W as i32 - 1);
                let y = (hy as i32 + self.rng.below(13) as i32 - 6).clamp(0, H as i32 - 1);
                if self.walkable(x, y)
                    && self.res[y as usize * W + x as usize].0 == 0
                    && !self.houses.contains(&(x as usize, y as usize))
                {
                    self.wood -= 12;
                    self.stone -= 4;
                    self.houses.push((x as usize, y as usize));
                    self.say("A new house was built".into());
                }
            }
        }
        if p.hunger > 50.0 && p.food > 0 {
            p.food -= 1;
            p.hunger = (p.hunger - 25.0).max(0.0);
        }

        let home = self.home;
        let yield_n = if self.tools >= self.people.len() as u32 {
            2
        } else {
            1
        };
        let mut target: Option<(usize, usize)> = None;
        let mut gather: Option<u8> = None;
        let mut hunt = false;

        if night {
            if at_home {
                p.action = "sleeping";
            } else {
                p.action = "going home";
                target = Some(home);
            }
        } else if p.hunger > 50.0 && p.food == 0 && self.food > 0 {
            p.action = "going to eat";
            target = Some(home);
        } else if p.carry() >= 6 {
            p.action = "hauling goods";
            target = Some(home);
        } else {
            let order: [u8; 3] = if self.food < 12 || p.hunger > 50.0 {
                [BERRY, TREE, STONE]
            } else if self.wood <= self.stone * 2 + 8 {
                [TREE, STONE, BERRY]
            } else {
                [STONE, TREE, BERRY]
            };
            for k in order {
                if let Some(t) = self.nearest_res(pos, k, 25) {
                    target = Some(t);
                    gather = Some(k);
                    p.action = match k {
                        BERRY => "foraging",
                        TREE => "chopping wood",
                        _ => "mining stone",
                    };
                    break;
                }
            }
            if (self.food < 12 || p.hunger > 50.0)
                && (gather != Some(BERRY) || self.rng.chance(0.3))
            {
                if let Some(r) = Self::nearest_animal(&self.rabbits, pos, 25) {
                    target = Some((self.rabbits[r].x, self.rabbits[r].y));
                    hunt = true;
                    gather = None;
                    p.action = "hunting";
                }
            }
        }

        if let Some(t) = target {
            if hunt {
                if cheb(pos, t) <= 1 {
                    if let Some(r) = Self::nearest_animal(&self.rabbits, pos, 1) {
                        if self.rng.chance(0.5) {
                            self.rabbits[r].dead = true;
                            p.food += 3;
                        }
                    }
                } else {
                    (p.x, p.y) = self.move_toward(pos, t);
                }
            } else if let Some(k) = gather {
                let idx = pos.1 * W + pos.0;
                if pos == t && self.res[idx].0 == k {
                    let take = (yield_n as u16).min(self.res[idx].1);
                    self.res[idx].1 -= take;
                    if self.res[idx].1 == 0 {
                        self.res[idx].0 = 0;
                    }
                    match k {
                        BERRY => p.food += take as u32,
                        TREE => p.wood += take as u32,
                        _ => p.stone += take as u32,
                    }
                } else {
                    (p.x, p.y) = self.move_toward(pos, t);
                }
            } else if !at_home || p.action == "going to eat" && cheb(pos, t) > 1 {
                (p.x, p.y) = self.move_toward(pos, t);
            }
        } else if p.action != "sleeping" {
            p.action = "wandering";
            (p.x, p.y) = self.wander(p.x, p.y);
        }
        self.people[i] = p;
    }

    fn tick_rabbit(&mut self, i: usize) {
        let mut a = self.rabbits[i].clone();
        a.energy -= 0.05;
        if matches!(self.tiles[a.y * W + a.x], GRASS | FOREST) {
            a.energy = (a.energy + 0.2).min(100.0);
        }
        let pos = (a.x, a.y);
        if let Some(w) = Self::nearest_animal(&self.wolves, pos, 4) {
            if self.rng.chance(0.8) {
                let dx = (a.x as i32 - self.wolves[w].x as i32).signum();
                let dy = (a.y as i32 - self.wolves[w].y as i32).signum();
                (a.x, a.y) = self.move_dir(a.x, a.y, dx, dy);
            }
        } else if self.rng.chance(0.5) {
            (a.x, a.y) = self.wander(a.x, a.y);
        }
        if a.energy > 80.0 && self.rabbits.len() < 120 && self.rng.chance(0.01) {
            a.energy -= 30.0;
            self.rabbits.push(Animal {
                x: a.x,
                y: a.y,
                energy: 50.0,
                dead: false,
            });
        }
        if a.energy <= 0.0 {
            a.dead = true;
        }
        self.rabbits[i] = a;
    }

    fn tick_wolf(&mut self, i: usize) {
        let mut a = self.wolves[i].clone();
        a.energy -= 0.15;
        let pos = (a.x, a.y);
        if let Some(r) = Self::nearest_animal(&self.rabbits, pos, 10) {
            let t = (self.rabbits[r].x, self.rabbits[r].y);
            if cheb(pos, t) <= 1 {
                if self.rng.chance(0.4) {
                    self.rabbits[r].dead = true;
                    a.energy = (a.energy + 50.0).min(100.0);
                }
            } else {
                (a.x, a.y) = self.move_toward(pos, t);
            }
        } else {
            (a.x, a.y) = self.wander(a.x, a.y);
        }
        if a.energy > 90.0 && self.wolves.len() < 10 && self.rng.chance(0.02) {
            a.energy -= 40.0;
            self.wolves.push(Animal {
                x: a.x,
                y: a.y,
                energy: 50.0,
                dead: false,
            });
        }
        if a.energy <= 0.0 {
            a.dead = true;
        }
        self.wolves[i] = a;
    }

    pub fn terrain_json(&self) -> String {
        let tiles: String = self.tiles.iter().map(|t| (b'0' + t) as char).collect();
        format!("{{\"w\":{},\"h\":{},\"tiles\":\"{}\"}}", W, H, tiles)
    }

    pub fn state_json(&self) -> String {
        let mut s = String::new();
        let _ = write!(
            s,
            "{{\"tick\":{},\"day\":{},\"hour\":{:.2},\"daylight\":{:.3},\"stock\":{{\"food\":{},\"wood\":{},\"stone\":{},\"tools\":{}}},\"home\":[{},{}],",
            self.tick,
            self.tick / DAY + 1,
            (self.tick % DAY) as f32 / DAY as f32 * 24.0,
            self.daylight(),
            self.food,
            self.wood,
            self.stone,
            self.tools,
            self.home.0,
            self.home.1
        );
        s.push_str("\"houses\":[");
        let j: Vec<String> = self
            .houses
            .iter()
            .map(|h| format!("[{},{}]", h.0, h.1))
            .collect();
        s.push_str(&j.join(","));
        s.push_str("],\"people\":[");
        let j: Vec<String> = self
            .people
            .iter()
            .map(|p| {
                format!(
                    "[{},{},{},\"{}\",{:.0},{},{},{}]",
                    p.id, p.x, p.y, p.action, p.hunger, p.food, p.wood, p.stone
                )
            })
            .collect();
        s.push_str(&j.join(","));
        s.push_str("],\"rabbits\":[");
        let j: Vec<String> = self
            .rabbits
            .iter()
            .map(|a| format!("[{},{},{:.0}]", a.x, a.y, a.energy))
            .collect();
        s.push_str(&j.join(","));
        s.push_str("],\"wolves\":[");
        let j: Vec<String> = self
            .wolves
            .iter()
            .map(|a| format!("[{},{},{:.0}]", a.x, a.y, a.energy))
            .collect();
        s.push_str(&j.join(","));
        s.push_str("],\"res\":[");
        let mut first = true;
        for (i, r) in self.res.iter().enumerate() {
            if r.0 != 0 {
                if !first {
                    s.push(',');
                }
                first = false;
                let _ = write!(s, "[{},{},{},{}]", i % W, i / W, r.0, r.1);
            }
        }
        s.push_str("],\"log\":[");
        let j: Vec<String> = self.log.iter().map(|l| format!("\"{}\"", l)).collect();
        s.push_str(&j.join(","));
        s.push_str("]}");
        s
    }
}