desmack 0.2.0

use std::fs;
use std::path::Path;

use anyhow::{Context, bail, ensure};

use crate::graphics::{cheep_cheep_frames, mode7, podium_mode7};
use crate::maps::{THEMES, bytes, long, near, stream, word};
use crate::rom::{Region, Rom};
use crate::textures::{palette, theme_stream, write_png};

/// Six blocks of 640 bytes: four 16×16 frames of 4 tiles each, then four 8×8 frames.
const ITEMS: usize = 0x40594;

/// Each item's blocks and sprite palette. The two shell blocks are its spin; the red shell is the
/// green one in another palette.
const ITEM_SETS: [(&str, &[usize], u16); 6] = [
	("banana", &[0], 6),
	("green-shell", &[1, 2], 6),
	("red-shell", &[1, 2], 5),
	("poison-mushroom", &[3], 5),
	("fireball", &[4], 6),
	("egg", &[5], 5),
];

/// The coin a driver spends or loses spins through three 16×16 tile words of the race sprites, in
/// palette 6. A fourth word follows, which the game never reaches.
const COIN: usize = 0x5E67F;
const COIN_FRAMES: usize = 3;

/// Course list group 2: a Theme's 57 hazard tiles, which the game loads at OBJ tile `0xC0`.
const HAZARD_TILES: usize = 2;
const HAZARD_BASE: usize = 0xC0;
/// A blank 16×16 OBJ tile that Ghost Valley's pillars pad their frames with.
const BLANK: u16 = 0x84;

const GHOST_VALLEY: usize = 0;
const MARIO_CIRCUIT: usize = 1;
const DONUT_PLAINS: usize = 2;
const CHOCO_ISLAND: usize = 3;
const KOOPA_BEACH: usize = 5;
const BOWSER_CASTLE: usize = 6;

/// Indices into [`Bank0::of`]'s scripts.
const PIRANHA: usize = 0;
const THWOMP: usize = 2;
const MOLE: usize = 3;
const PIPE: usize = 5;
const PILLAR: usize = 6;
const SHADOW: usize = 7;

/// Each hazard's name, graphics Theme, palette Theme and scripts, each with the value the game
/// XORs into its tile words. Donut Plains 1 draws Mario Circuit's pipes in palette 5; Vanilla
/// Lake's pipes are Mario Circuit's; Rainbow Road's Thwomps are Bowser Castle's, cycling through
/// palettes.
type Scripted = &'static [(usize, u16)];

const HAZARDS: [(&str, usize, usize, Scripted); 7] = [
	("pipe", MARIO_CIRCUIT, MARIO_CIRCUIT, &[(PIPE, 0)]),
	("orange-pipe", MARIO_CIRCUIT, DONUT_PLAINS, &[(PIPE, 0x400)]),
	("pillar", GHOST_VALLEY, GHOST_VALLEY, &[(PILLAR, 0)]),
	(
		"monty-mole",
		DONUT_PLAINS,
		DONUT_PLAINS,
		&[(MOLE, 0), (MOLE + 1, 0)],
	),
	(
		"piranha-plant",
		CHOCO_ISLAND,
		CHOCO_ISLAND,
		&[(PIRANHA, 0), (PIRANHA + 1, 0)],
	),
	(
		"cheep-cheep",
		KOOPA_BEACH,
		KOOPA_BEACH,
		&[(PIRANHA, 0), (PIRANHA + 1, 0)],
	),
	(
		"thwomp",
		BOWSER_CASTLE,
		BOWSER_CASTLE,
		&[(THWOMP, 0x600), (SHADOW, 0)],
	),
];

/// Where each Region keeps its sprite routines, hazard scripts and driver tables, in bank 0.
struct Bank0 {
	routines: usize,
	scripts: [usize; 8],
	drivers: usize,
}

impl Bank0 {
	fn of(region: Region) -> Bank0 {
		match region {
			Region::Japan => Bank0 {
				routines: 0xBC34,
				scripts: [
					0xE0E1, 0xE0FD, 0xE2E8, 0xE3E1, 0xE3FD, 0xE5A7, 0xE71C, 0xED31,
				],
				drivers: 0x9069,
			},
			Region::Usa => Bank0 {
				routines: 0xBC0F,
				scripts: [
					0xE0BC, 0xE0D8, 0xE2C3, 0xE3BC, 0xE3D8, 0xE582, 0xE716, 0xED2B,
				],
				drivers: 0x9090,
			},
			Region::Europe => Bank0 {
				routines: 0xBC34,
				scripts: [
					0xE0E1, 0xE0FD, 0xE2E8, 0xE3E1, 0xE3FD, 0xE5A7, 0xE73B, 0xED50,
				],
				drivers: 0x9077,
			},
		}
	}
}

/// The drivers in the game's order, which the bank table follows, with their sprite palettes: two
/// drivers share each of sprite palettes 8–11.
pub const DRIVERS: [(&str, u16); 8] = [
	("mario", 1),
	("luigi", 2),
	("bowser", 0),
	("peach", 3),
	("dk-jr", 3),
	("koopa-troopa", 2),
	("toad", 1),
	("yoshi", 0),
];
const LUIGI: usize = 1;

/// The driver tables, from [`Bank0::of`]'s `drivers`: a (frame, layout) byte pair per frame code;
/// then each frame's address in a driver's bank; then, for Luigi, a word per frame code that picks
/// his own upper half, from the bank table after it. The banks come 16 bytes before.
///
/// The race codes are 11 scales, nearest first, of 16 angles from behind (0) to the front (15);
/// the game mirrors them for the other side. Far scales share a frame between angles. The
/// specials follow, which the game sets over the race codes.
const SCALES: usize = 11;
const ANGLES: usize = 16;
const SPECIALS: [&str; 5] = ["cheer-back", "look-back", "look-side", "cheer", "dazed"];
const FRAME_TABLE: usize = 0x16A;
const LUIGI_TABLE: usize = 0x202;
const LUIGI_TOPS: usize = 0x36C;
/// Luigi's upper halves are in bank `$84`; the rest of him is Mario's.
const LUIGI_BANK: usize = 0x84;
const MARIO_BANK: usize = 0xC0;

/// Lakitu, coins and the race's shared sprites: stream tiles 16–143 load at OBJ tile `0x40`, and
/// 12–15, the start lights, at `0xFB`.
const RACE_SPRITES: usize = 0x10000;
/// Lakitu's frames: a table of offsets from itself to metasprite records.
const LAKITU: usize = 0x5E264;
const LAKITU_FRAMES: usize = 14;
/// Lakitu's palette and his lights' are the same in every Theme.
pub const LAKITU_THEME: usize = MARIO_CIRCUIT;
/// The frame with the LAP sign. Its last sprite is the digit, tile `0xA2`; for laps 2–4 the game
/// swaps in `0xA1` + the lap, which shows from behind the sign.
const LAP_SIGN: usize = 11;
const LAP_DIGIT: u16 = 0xA1;

/// The podium's OBJ tiles are the first 320 of its stream. The game adds two heads per driver, the
/// upper halves of race frames: half rows of 2 tiles, `0x200` apart, from `0x40` and `0x5900`
/// (Luigi `0x2100`) past the address in this table, in [`DRIVERS`] order.
fn podium_heads(region: Region) -> usize {
	match region {
		Region::Usa => 0x59EEF,
		Region::Japan => 0x59EB2,
		Region::Europe => 0x59EF9,
	}
}
const PODIUM_OBJ: usize = 0x2800;
const HEAD_TILES: [usize; 8] = [0x140, 0x160, 0x144, 0x148, 0x14C, 0x164, 0x168, 0x16C];

/// The podium's frames: pointer tables in a row, each followed by its frames, which are OAM
/// entries (x, y, tile, attribute) ending in `0xFFFF`. Each frame is copied to OAM from a slot,
/// which sets its sprites' sizes.
fn podium_tables(region: Region) -> (usize, PodiumTables) {
	match region {
		Region::Usa => (0x5A330, PODIUM_TABLES),
		Region::Japan => (0x5A2DE, PODIUM_TABLES_JAPAN),
		Region::Europe => (0x5A33A, PODIUM_TABLES),
	}
}
/// Each table's driver and the slot of each of its frames, the last one repeating: the driver's
/// poses, then the champagne they hold and its spray. In Japan Bowser sprays too and Peach holds a
/// bottle.
type PodiumTables = &'static [(usize, &'static [usize])];
const PODIUM_TABLES: PodiumTables = &[
	(0, &[94]),
	(0, &[90]),
	(0, &[82, 82, 83, 84]),
	(2, &[94]),
	(2, &[90]),
	(3, &[94]),
	(4, &[94, 94, 94, 94, 84]),
	(4, &[90]),
	(1, &[94]),
	(1, &[90]),
	(1, &[90, 82, 84]),
	(5, &[94]),
	(5, &[90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 84]),
	(6, &[94]),
	(6, &[90]),
	(7, &[94]),
];
const PODIUM_TABLES_JAPAN: PodiumTables = &[
	(0, &[94]),
	(0, &[90]),
	(0, &[82, 82, 83, 84]),
	(2, &[94]),
	(2, &[90]),
	(2, &[82]),
	(3, &[94, 94, 92]),
	(3, &[90]),
	(4, &[94, 94, 94, 94, 84]),
	(4, &[90]),
	(1, &[94]),
	(1, &[90]),
	(1, &[90, 82, 84]),
	(5, &[94]),
	(5, &[90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 84]),
	(6, &[94]),
	(6, &[90]),
	(7, &[94]),
];
/// The podium makes OAM slots 80–83, 90, 91 and 94 on 16×16, the rest 8×8.
fn big(slot: usize) -> bool {
	matches!(slot, 80..=83 | 90 | 91 | 94..)
}
/// The podium's single sprites, tile word tables in bank `$85`: (name, table, count, 16×16). The
/// cups' icons float in the sky, the Special Cup's cycling through all three; Cheep Cheep brings
/// the trophy for the player's rank; confetti flutters through three frames per piece; the pop
/// bursts as the champagne opens, its third frame a blank tile.
fn podium_singles(region: Region) -> [(&'static str, usize, usize, bool); 4] {
	let [cups, trophies, confetti, pop] = match region {
		Region::Usa => [0x5A040, 0x5A32A, 0x5AB43, 0x5AB89],
		Region::Japan => [0x59FCE, 0x5A2D8, 0x5AB1F, 0x5AB65],
		Region::Europe => [0x5A04A, 0x5A334, 0x5AB4D, 0x5AB93],
	};
	[
		("cups", cups, 3, true),
		("trophies", trophies, 3, true),
		("confetti", confetti, 18, false),
		("pop", pop, 2, true),
	]
}
/// Sprites from this line down are hidden.
const HIDDEN: i32 = 0xE0;

/// The race's effect tiles: water and grass at OBJ tile 0, dust and smoke at `0x100`.
const EFFECT_TILES: usize = 0x903;
fn dust_tiles(region: Region) -> usize {
	match region {
		Region::Usa => 0x49C19,
		Region::Japan | Region::Europe => 0x49C1C,
	}
}
/// Six metasprite tables in a row, each a list of offsets from itself to its records.
const EFFECT_TABLES: usize = 0x5EE00;
/// Each effect's table and the value the game XORs into its tile words, as bank 0's effect list
/// pairs them: `0x100` picks the dust tiles, `0x400` swaps sprite palette 15 for 13. Frames come
/// in fours, each four one looping animation. Table 0's first 48 frames are for a Time Trial
/// against a ghost, the rest for a kart shrunk by lightning. Table 2's frames 1 and 5 are the
/// ripple over a sunken kart, which the splash's animation ends by looping.
type Picks = fn(usize) -> bool;

const EFFECTS: [(&str, usize, u16, Picks); 12] = [
	("dust", 5, 0x100, |_| true),
	("smoke", 5, 0x500, |_| true),
	("dust-vs-ghost", 0, 0x100, |k| k < 48),
	("smoke-vs-ghost", 0, 0x500, |k| k < 48),
	("dust-small", 0, 0x100, |k| k >= 48),
	("smoke-small", 0, 0x500, |k| k >= 48),
	("spray", 1, 0, |_| true),
	("splash", 2, 0, |k| k != 1 && k != 5),
	("ripple", 2, 0, |k| k == 1 || k == 5),
	("grass", 3, 0, |_| true),
	("smoke-puff", 4, 0x100, |_| true),
	("dust-puff", 4, 0x500, |_| true),
];

/// One OAM entry: a position, a tile word (tile, palette, flips) and whether it is 16×16.
#[derive(Clone, Copy)]
pub struct Sprite {
	pub x: i32,
	pub y: i32,
	pub tile: u16,
	pub big: bool,
}

pub fn items(rom: &Rom, folder: &Path) -> anyhow::Result<()> {
	let tiles = stream(&rom.data, ITEMS)?;
	ensure!(tiles.len() == 6 * 640, "item graphics are not 6 items");
	let palette = palette(rom, MARIO_CIRCUIT)?;
	for (name, blocks, pal) in ITEM_SETS {
		let mut frames = Vec::new();
		for block in blocks {
			for k in 0..8 {
				let tile = (block * 640 / 32 + if k < 4 { k * 4 } else { 16 + k - 4 }) as u16;
				let sprite = |x, y, tile| Sprite {
					x,
					y,
					tile: tile | pal << 9,
					big: false,
				};
				frames.push(if k < 4 {
					vec![
						sprite(0, 0, tile),
						sprite(8, 0, tile + 1),
						sprite(0, 8, tile + 2),
						sprite(8, 8, tile + 3),
					]
				} else {
					vec![sprite(0, 0, tile)]
				});
			}
		}
		write_frames(
			&folder.join("sprites/items").join(name),
			&frames,
			&tiles,
			&palette,
		)?;
	}
	write_frames(
		&folder.join("sprites/items/coin"),
		&tile_words(&rom.data, COIN, COIN_FRAMES, true)?,
		&race_tiles(rom)?,
		&palette,
	)
}

/// One single-sprite frame per tile word of the table at `at`.
fn tile_words(data: &[u8], at: usize, count: usize, big: bool) -> anyhow::Result<Vec<Vec<Sprite>>> {
	(0..count)
		.map(|k| {
			Ok(vec![Sprite {
				x: 0,
				y: 0,
				tile: word(data, at + k * 2)? as u16,
				big,
			}])
		})
		.collect()
}

pub fn hazards(rom: &Rom, folder: &Path) -> anyhow::Result<()> {
	let Bank0 {
		routines, scripts, ..
	} = Bank0::of(rom.region);
	for (name, graphics, colours, uses) in HAZARDS {
		let mut frames = Vec::new();
		for &(script, xor) in uses {
			frames.extend(script_frames(&rom.data, routines, scripts[script], xor)?);
		}
		write_frames(
			&folder.join("sprites/hazards").join(name),
			&frames,
			&theme_stream(rom, HAZARD_TILES, graphics)?,
			&palette(rom, colours)?,
		)?;
	}
	Ok(())
}

/// OBJ tiles 0–255 as the race loads its shared sprites.
pub fn race_tiles(rom: &Rom) -> anyhow::Result<Vec<u8>> {
	let stream = stream(&rom.data, RACE_SPRITES)?;
	ensure!(stream.len() >= 144 * 32, "race sprites stop short");
	let mut tiles = vec![0; 0x100 * 32];
	tiles[0x40 * 32..0xC0 * 32].copy_from_slice(&stream[16 * 32..144 * 32]);
	tiles[0xFB * 32..0xFF * 32].copy_from_slice(&stream[12 * 32..16 * 32]);
	Ok(tiles)
}

/// Lakitu's frames, then the LAP sign for laps 2–4.
pub fn cast(rom: &Rom, folder: &Path) -> anyhow::Result<()> {
	let mut frames = (0..LAKITU_FRAMES)
		.map(|k| metasprite(&rom.data, LAKITU + word(&rom.data, LAKITU + k * 2)?))
		.collect::<anyhow::Result<Vec<_>>>()?;
	for lap in 2..=4 {
		let mut sign = frames[LAP_SIGN].clone();
		let digit = sign.last_mut().context("the LAP sign has no sprites")?;
		digit.tile = digit.tile & 0xFF00 | (LAP_DIGIT + lap);
		frames.push(sign);
	}
	write_frames(
		&folder.join("sprites/cast/lakitu"),
		&frames,
		&race_tiles(rom)?,
		&palette(rom, LAKITU_THEME)?,
	)?;

	let (podium, tiles, colours) = podium_mode7(rom)?;
	let objects = podium_tiles(rom, &podium)?;
	for (driver, frames) in podium_frames(rom)?.iter().enumerate() {
		write_frames(
			&folder.join("sprites/cast/podium").join(DRIVERS[driver].0),
			frames,
			&objects,
			&colours,
		)?;
	}
	for (name, at, count, big) in podium_singles(rom.region) {
		write_frames(
			&folder.join("sprites/cast/podium").join(name),
			&tile_words(&rom.data, at, count, big)?,
			&objects,
			&colours,
		)?;
	}

	// The podium's Cheep Cheep is no sprite, but a piece of the Mode 7 map.
	let dir = folder.join("sprites/cast/cheep-cheep");
	fs::create_dir_all(&dir)?;
	for (i, pieces) in cheep_cheep_frames(rom)?.iter().enumerate() {
		let (width, height, pixels) = mode7(&tiles, pieces);
		write_png(
			&dir.join(format!("{i:03}.png")),
			width,
			height,
			&colours,
			&pixels,
		)?;
	}
	Ok(())
}

/// OBJ tiles 0–511 as the podium loads them.
fn podium_tiles(rom: &Rom, podium: &[u8]) -> anyhow::Result<Vec<u8>> {
	let mut tiles = vec![0; 0x200 * 32];
	tiles[..PODIUM_OBJ].copy_from_slice(&podium[..PODIUM_OBJ]);
	let heads = podium_heads(rom.region);
	for (driver, tile) in HEAD_TILES.into_iter().enumerate() {
		let at = long(&rom.data, heads + driver * 3)?;
		let second = if driver == LUIGI { 0x2100 } else { 0x5900 };
		for row in 0..2 {
			for (k, head) in [0x40, second].into_iter().enumerate() {
				let to = (tile + row * 16 + k * 2) * 32;
				tiles[to..to + 0x40].copy_from_slice(bytes(
					&rom.data,
					at + head + row * 0x200,
					0x40,
				)?);
			}
		}
	}
	Ok(tiles)
}

/// Each driver's podium frames, in table order, without repeats or hidden sprites.
fn podium_frames(rom: &Rom) -> anyhow::Result<Vec<Vec<Vec<Sprite>>>> {
	let (mut at, tables) = podium_tables(rom.region);
	let mut frames = vec![Vec::new(); DRIVERS.len()];
	for &(driver, slots) in tables {
		let mut pointers: Vec<usize> = Vec::new();
		while pointers.iter().all(|&p| at + pointers.len() * 2 < p) {
			ensure!(pointers.len() < 16, "podium table at {at:#X} runs long");
			pointers.push(near(&rom.data, at + pointers.len() * 2)?);
		}
		let mut seen = Vec::new();
		for (k, &pointer) in pointers.iter().enumerate() {
			let slot = slots[k.min(slots.len() - 1)];
			let mut sprites = Vec::new();
			let mut entry = pointer;
			while word(&rom.data, entry)? != 0xFFFF {
				let [x, y, tile, attr] = bytes(&rom.data, entry, 4)?.try_into()?;
				if i32::from(y) < HIDDEN {
					sprites.push(Sprite {
						x: i32::from(x),
						y: i32::from(y),
						tile: u16::from(tile) | u16::from(attr) << 8,
						big: big(slot + (entry - pointer) / 4),
					});
				}
				entry += 4;
			}
			at = at.max(entry + 2);
			if !seen.contains(&pointer) {
				seen.push(pointer);
				frames[driver].push(sprites);
			}
		}
	}
	Ok(frames)
}

/// Effects take their colours from the Theme palette. An effect whose colours are the same in
/// every Theme is written once; otherwise each Theme gets its own folder.
pub fn effects(rom: &Rom, folder: &Path) -> anyhow::Result<()> {
	let mut tiles = vec![0; 0x200 * 32];
	let water = stream(&rom.data, EFFECT_TILES)?;
	let dust = stream(&rom.data, dust_tiles(rom.region))?;
	ensure!(
		water.len() <= 0x100 * 32 && dust.len() <= 0x100 * 32,
		"effect tiles run long"
	);
	tiles[..water.len()].copy_from_slice(&water);
	tiles[0x100 * 32..0x100 * 32 + dust.len()].copy_from_slice(&dust);
	let tables = stream(&rom.data, EFFECT_TABLES)?;
	let mut starts = vec![0];
	for _ in 1..6 {
		let table = starts[starts.len() - 1];
		let mut last = 0;
		for k in 0..word(&tables, table)? / 2 {
			last = last.max(word(&tables, table + k * 2)?);
		}
		let count = usize::from(bytes(&tables, table + last, 1)?[0]);
		starts.push(table + last + 1 + count * 4 + count / 4 + 1);
	}
	let palettes = (0..THEMES.len())
		.map(|theme| palette(rom, theme))
		.collect::<anyhow::Result<Vec<_>>>()?;
	for (name, table, xor, picks) in EFFECTS {
		let start = starts[table];
		let mut frames = Vec::new();
		for k in (0..word(&tables, start)? / 2).filter(|&k| picks(k)) {
			let mut sprites = metasprite(&tables, start + word(&tables, start + k * 2)?)?;
			for sprite in &mut sprites {
				sprite.tile ^= xor;
			}
			frames.push(draw(&sprites, &tiles)?);
		}
		let colours = |palette: &[u8]| -> Vec<u8> {
			frames
				.iter()
				.flat_map(|(_, _, pixels)| pixels)
				.filter(|&&p| p != 0)
				.flat_map(|&p| palette[usize::from(p) * 3..usize::from(p) * 3 + 3].to_vec())
				.collect()
		};
		let same = palettes
			.iter()
			.all(|p| colours(p) == colours(&palettes[MARIO_CIRCUIT]));
		let dir = folder.join("sprites/effects").join(name);
		let themes: Vec<_> = if same {
			vec![(dir, &palettes[MARIO_CIRCUIT])]
		} else {
			THEMES
				.iter()
				.zip(&palettes)
				.map(|(theme, palette)| (dir.join(theme), palette))
				.collect()
		};
		for (dir, palette) in themes {
			fs::create_dir_all(&dir)?;
			for (i, (width, height, pixels)) in frames.iter().enumerate() {
				write_png(
					&dir.join(format!("{i:03}.png")),
					*width,
					*height,
					palette,
					pixels,
				)?;
			}
		}
	}
	Ok(())
}

/// A metasprite record: a sprite count, then x and y as i8, the tile and the OAM attribute byte for
/// each sprite, then OAM's 2 high bits per sprite, of which the upper is the size.
fn metasprite(data: &[u8], at: usize) -> anyhow::Result<Vec<Sprite>> {
	let count = usize::from(bytes(data, at, 1)?[0]);
	let sizes = bytes(data, at + 1 + count * 4, count.div_ceil(4))?;
	(0..count)
		.map(|i| {
			let [x, y, tile, attr] = bytes(data, at + 1 + i * 4, 4)?.try_into()?;
			Ok(Sprite {
				x: i32::from(x as i8),
				y: i32::from(y as i8),
				tile: u16::from(tile) | u16::from(attr) << 8,
				big: sizes[i / 4] >> (i % 4 * 2 + 1) & 1 != 0,
			})
		})
		.collect()
}

/// Each driver's 76 frames, in frame table order. Two more frame codes draw from RAM the game fills
/// at run time, and are left out.
pub fn drivers(rom: &Rom, folder: &Path) -> anyhow::Result<()> {
	let codes = Bank0::of(rom.region).drivers;
	let palette = palette(rom, MARIO_CIRCUIT)?;
	for (driver, (name, pal)) in DRIVERS.into_iter().enumerate() {
		let dir = folder.join("sprites/drivers").join(name);
		let mut frames = Vec::new();
		for scale in 0..SCALES {
			let mut seen = Vec::new();
			for angle in 0..ANGLES {
				let code = scale * ANGLES + angle;
				if !seen.contains(&rom.data[codes + code * 2]) {
					seen.push(rom.data[codes + code * 2]);
					frames.push((code, format!("scale-{scale:02}/angle-{angle:02}.png")));
				}
			}
		}
		for (k, special) in SPECIALS.iter().enumerate() {
			frames.push((SCALES * ANGLES + k, format!("{special}.png")));
		}
		for (code, file) in frames {
			let path = dir.join(file);
			fs::create_dir_all(path.parent().unwrap())?;
			let (tiles, layout) = slot(&rom.data, codes, driver, code)?;
			let mut sprites = sprites_of(layout)?;
			for sprite in &mut sprites {
				sprite.tile |= pal << 9;
			}
			let (width, height, pixels) = draw(&sprites, &tiles)?;
			write_png(&path, width, height, &palette, &pixels)?;
		}
	}
	Ok(())
}

/// A driver's VRAM slot, 4 rows of 16 tiles, as the game fills it for a frame code: the layout's
/// low nibble counts rows, its high nibble is the bytes per row, and rows are `0x200` apart in the
/// bank. Luigi's 32×32 frames take their upper two rows from his own bank and the lower two from
/// Mario's; a flag word picks half-width rows (`0x200`) or upper rows only (`0x400`). The
/// half-width flag also marks every mirrored 32×32 frame, which the layout byte misses for two of
/// them, so the slot comes with the layout to draw it with.
fn slot(data: &[u8], codes: usize, driver: usize, code: usize) -> anyhow::Result<(Vec<u8>, u8)> {
	let frame = word(
		data,
		codes + FRAME_TABLE + usize::from(data[codes + code * 2]),
	)?;
	let mut layout = data[codes + code * 2 + 1];
	let luigi = word(data, codes + LUIGI_TABLE + code * 2)?;
	if luigi & 0x8200 == 0x200 {
		layout = 0x44;
	}
	let at = |bank: usize, address: usize| (bank & 0x3F) << 16 | address;
	let rows: Vec<(usize, usize)> = if driver == LUIGI && luigi & 0x8000 == 0 {
		let top = word(data, codes + LUIGI_TOPS + (luigi & 0xFF))?;
		let size = if luigi & 0x200 != 0 { 0x40 } else { 0x80 };
		let mut rows = vec![
			(at(LUIGI_BANK, top), size),
			(at(LUIGI_BANK, top + 0x200), size),
		];
		if luigi & 0x400 == 0 {
			rows.push((at(MARIO_BANK, frame + 0x400), size));
			rows.push((at(MARIO_BANK, frame + 0x600), size));
		}
		rows
	} else {
		let bank = word(
			data,
			codes - 16 + if driver == LUIGI { 0 } else { driver * 2 },
		)?;
		(0..usize::from(layout & 15))
			.map(|r| (at(bank, frame + r * 0x200), usize::from(layout & 0xF0)))
			.collect()
	};
	let mut slot = vec![0; 4 * 0x200];
	for (r, (source, size)) in rows.into_iter().enumerate() {
		slot[r * 0x200..r * 0x200 + size].copy_from_slice(bytes(data, source, size)?);
	}
	Ok((slot, layout))
}

/// How the game places a layout's sprites over the slot. Symmetric frames hold a half, drawn
/// again mirrored; the 24-pixel ones overlap it, 7 pixels to the right. The `0x41` frames stack
/// their two tiles.
fn sprites_of(layout: u8) -> anyhow::Result<Vec<Sprite>> {
	let s = |x, y, tile, big| Sprite { x, y, tile, big };
	Ok(match layout {
		0x84 => vec![
			s(0, 0, 0, true),
			s(16, 0, 2, true),
			s(0, 16, 32, true),
			s(16, 16, 34, true),
		],
		0x82 => vec![s(0, 0, 0, true), s(16, 0, 2, true)],
		0x44 => vec![
			s(0, 0, 0, true),
			s(16, 0, 0x4000, true),
			s(0, 16, 32, true),
			s(16, 16, 0x4000 | 32, true),
		],
		0x63 => vec![
			s(0, 0, 0, true),
			s(8, 0, 1, true),
			s(0, 8, 16, true),
			s(8, 8, 17, true),
		],
		0x43 => vec![
			s(0, 0, 0, true),
			s(7, 0, 0x4000, true),
			s(0, 8, 16, true),
			s(7, 8, 0x4000 | 16, true),
		],
		0x42 => vec![s(0, 0, 0, true)],
		0x41 => vec![s(0, 0, 0, false), s(0, 8, 1, false)],
		0x21 => vec![s(0, 0, 0, false)],
		_ => bail!("unknown driver layout {layout:#X}"),
	})
}

/// A hazard script is two op words, then frame records for 12 sizes, of which the game picks
/// from the first 11. A size that repeats the one before is the same frame.
fn script_frames(
	data: &[u8],
	routines: usize,
	script: usize,
	xor: u16,
) -> anyhow::Result<Vec<Vec<Sprite>>> {
	let mut frames = Vec::new();
	let mut last = None;
	for size in 0..11 {
		let record = word(data, script + 4 + size * 2)?;
		if last.replace(record) == Some(record) {
			continue;
		}
		let mut sprites = frame(data, routines, record)?;
		sprites.retain(|s| s.tile & 0x1FF != BLANK);
		for sprite in &mut sprites {
			let tile = usize::from(sprite.tile & 0x1FF)
				.checked_sub(HAZARD_BASE)
				.with_context(|| {
					format!("frame at {record:#X} uses a tile outside the hazard's")
				})?;
			sprite.tile = (sprite.tile & !0x1FF | tile as u16) ^ xor;
		}
		if !sprites.is_empty() {
			frames.push(sprites);
		}
	}
	Ok(frames)
}

/// A frame record starts with its sprite routine. Routines with 2 or 4 sprites point to their
/// (y, x) offsets and tile words; those with 1 sprite hold its tile word. Positions only matter
/// within a frame, so the routines' anchors and y adjustments are left out.
fn frame(data: &[u8], routines: usize, record: usize) -> anyhow::Result<Vec<Sprite>> {
	let routine = word(data, record)?;
	let (count, big) = match routine.wrapping_sub(routines) {
		0x00 | 0x08 => (2, true),
		0x0D | 0x15 => (2, false),
		0x6F | 0x77 => (4, true),
		0x7C | 0x84 => (4, false),
		0x147 | 0x14F | 0x157 => (1, true),
		0x15F | 0x167 | 0x16F => (1, false),
		// The script op that draws nothing.
		0xAD4 => return Ok(Vec::new()),
		_ => bail!("frame at {record:#X} uses unknown routine {routine:#X}"),
	};
	if count == 1 {
		let tile = word(data, record + 2)? as u16;
		return Ok(vec![Sprite {
			x: 0,
			y: 0,
			tile,
			big,
		}]);
	}
	let (offsets, tiles) = (word(data, record + 2)?, word(data, record + 4)?);
	(0..count)
		.map(|i| {
			Ok(Sprite {
				x: i32::from(word(data, offsets + i * 4 + 2)? as i16),
				y: i32::from(word(data, offsets + i * 4)? as i16),
				tile: word(data, tiles + i * 2)? as u16,
				big,
			})
		})
		.collect()
}

fn write_frames(
	dir: &Path,
	frames: &[Vec<Sprite>],
	tiles: &[u8],
	palette: &[u8],
) -> anyhow::Result<()> {
	fs::create_dir_all(dir)?;
	for (i, sprites) in frames.iter().enumerate() {
		let (width, height, pixels) = draw(sprites, tiles)?;
		write_png(
			&dir.join(format!("{i:03}.png")),
			width,
			height,
			palette,
			&pixels,
		)?;
	}
	Ok(())
}

/// Draws sprites from 4bpp planar OBJ tiles, cropped to their bounds. A 16×16 sprite is tiles
/// t, t + 1, t + 16 and t + 17, and the first sprite drawn wins, as in OAM. Colours are CGRAM's
/// sprite half: 128 + palette × 16 + colour.
pub fn draw(sprites: &[Sprite], tiles: &[u8]) -> anyhow::Result<(u32, u32, Vec<u8>)> {
	let size = |s: &Sprite| if s.big { 16 } else { 8 };
	let left = sprites.iter().map(|s| s.x).min().unwrap_or(0);
	let top = sprites.iter().map(|s| s.y).min().unwrap_or(0);
	let width = sprites.iter().map(|s| s.x + size(s)).max().unwrap_or(0) - left;
	let height = sprites.iter().map(|s| s.y + size(s)).max().unwrap_or(0) - top;
	let mut pixels = vec![0; (width * height) as usize];
	for s in sprites {
		let n = size(s);
		let colour = 128 + (s.tile >> 9 & 7) as u8 * 16;
		for y in 0..n {
			for x in 0..n {
				let sx = if s.tile & 0x4000 != 0 { n - 1 - x } else { x };
				let sy = if s.tile & 0x8000 != 0 { n - 1 - y } else { y };
				let tile = usize::from(s.tile & 0x1FF) + (sx / 8 + sy / 8 * 16) as usize;
				let row = bytes(tiles, tile * 32 + (sy % 8) as usize * 2, 18)?;
				let bit = 7 - sx % 8;
				let v = (row[0] >> bit & 1)
					| (row[1] >> bit & 1) << 1
					| (row[16] >> bit & 1) << 2
					| (row[17] >> bit & 1) << 3;
				let at = ((s.y - top + y) * width + s.x - left + x) as usize;
				if v != 0 && pixels[at] == 0 {
					pixels[at] = colour + v;
				}
			}
		}
	}
	Ok((width as u32, height as u32, pixels))
}

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

	#[test]
	fn draw_flips_crops_and_keeps_the_first_sprite() {
		// Tile 0: one colour-1 pixel at the top left. Tile 1: a colour-15 pixel there.
		let mut tiles = vec![0; 64];
		tiles[0] = 0x80;
		tiles[32..34].copy_from_slice(&[0x80, 0x80]);
		tiles[48..50].copy_from_slice(&[0x80, 0x80]);
		let sprites = [
			// Palette 2, flipped both ways, at (-8, -8).
			Sprite {
				x: -8,
				y: -8,
				tile: 0xC400,
				big: false,
			},
			Sprite {
				x: -8,
				y: -8,
				tile: 0x0001,
				big: false,
			},
			Sprite {
				x: 0,
				y: 0,
				tile: 0x0001,
				big: false,
			},
		];
		let (width, height, pixels) = draw(&sprites, &tiles).unwrap();
		assert_eq!((width, height), (16, 16));
		assert_eq!(pixels[7 * 16 + 7], 128 + 32 + 1);
		assert_eq!(pixels[0], 128 + 15);
		assert_eq!(pixels[8 * 16 + 8], 128 + 15);
		assert_eq!(pixels.iter().filter(|&&p| p != 0).count(), 3);
	}

	#[test]
	fn smk_rom_sprites() {
		let Ok(path) = std::env::var("SMK_ROM") else {
			return;
		};
		let rom = Rom::parse(fs::read(path).unwrap()).unwrap();
		let folder = std::env::temp_dir().join(format!("desmack-sprites-{}", std::process::id()));
		drivers(&rom, &folder).unwrap();
		items(&rom, &folder).unwrap();
		hazards(&rom, &folder).unwrap();
		cast(&rom, &folder).unwrap();
		effects(&rom, &folder).unwrap();
		let count = |dir: &str| {
			fs::read_dir(folder.join("sprites").join(dir))
				.unwrap()
				.count()
		};
		assert_eq!(count("drivers/luigi"), SCALES + SPECIALS.len());
		assert_eq!(count("drivers/luigi/scale-00"), 12);
		assert_eq!(count("drivers/luigi/scale-10"), 2);
		assert_eq!(count("cast/lakitu"), LAKITU_FRAMES + 3);
		assert_eq!(count("cast/cheep-cheep"), 2);
		assert_eq!(count("cast/podium"), DRIVERS.len() + 4);
		assert_eq!(count("cast/podium/mario"), 2 + 3 + 7);
		assert_eq!(count("cast/podium/confetti"), 18);
		assert_eq!(count("effects/smoke"), 48);
		assert_eq!(count("effects/smoke-small"), 12);
		assert_eq!(count("effects/spray"), THEMES.len());
		assert_eq!(count("effects/spray/koopa-beach"), 48);
		assert_eq!(count("effects/splash/koopa-beach"), 8);
		assert_eq!(count("effects/ripple/koopa-beach"), 2);
		assert_eq!(count("items/green-shell"), 16);
		assert_eq!(count("items/coin"), COIN_FRAMES);
		assert_eq!(count("hazards/pipe"), 11);
		assert_eq!(count("hazards/piranha-plant"), 20);
		assert_eq!(count("hazards/thwomp"), 11 + 5);
		fs::remove_dir_all(&folder).unwrap();
	}
}