use wasm_bindgen::prelude::wasm_bindgen;

#[wasm_bindgen]
pub fn find_winner(board: &[u8]) -> u8 {
	for i in 0..3 {
		let h = i*3;
		if board[h] != 0 && board[h] == board[h + 1] && board[h + 1] == board[h + 2] {
			return board[h];
		}
		if board[i] != 0 && board[i] == board[i + 3] && board[i + 3] == board[i + 6] {
			return board[i];
		}
	}
	if board[0] != 0 && board[0] == board[4] && board[4] == board[8] {
		return board[0];
	}
	if board[2] != 0 && board[2] == board[4] && board[4] == board[6] {
		return board[2];
	}
	0
}

#[wasm_bindgen]
pub fn count_empty(board: &[u8]) -> usize {
	board.iter().filter(|&n| *n == 0).count()
}

#[wasm_bindgen]
pub fn get_turn(me: u8, other: u8, first: bool, empty: usize) -> u8 {
	if empty % 2 == if first { 1 } else { 0 } {
		me
	} else {
		other
	}
}

#[wasm_bindgen]
pub fn sa_get_score(me: u8, other: u8, first: bool, board: &[u8]) -> f64 {
	let winner = find_winner(board);
	if winner != 0 {
		return if winner == me { 1.0 } else { -1.0 };
	}
	let empty = count_empty(board);
	if empty == 0 {
		return 0.0;
	}
	let mut score = 0.0;
	for i in 0..9 {
		if board[i] != 0 {
			continue;
		}
		let copy = &mut [0u8; 9];
		copy.copy_from_slice(board);
		copy[i] = get_turn(me, other, first, empty);
		score += sa_get_score(me, other, first, copy);
	}
	score
}

#[wasm_bindgen]
pub fn sa_rd_get_score(me: u8, other: u8, first: bool, board: &[u8]) -> f64 {
	let (outcomes, score) = sa_r_sub_get_score(me, other, first, board, 2, 2, 1);
	score as f64 / outcomes as f64
}

#[wasm_bindgen]
pub fn sa_r_d_get_score(me: u8, other: u8, first: bool, board: &[u8]) -> f64 {
	let (outcomes, score) = sa_r_sub_get_score(me, other, first, board, 1, 1, 0);
	score as f64 / outcomes as f64
}

// outcomes, winning outcomes
// m: Total outcomes multiplier
// w: Win winning outcome score
// d: Draw winning outcome score
// (loose = 0)
pub fn sa_r_sub_get_score(me: u8, other: u8, first: bool, board: &[u8], m: i32, w: i32, d: i32) -> (i32, i32) {
	let winner = find_winner(board);
	if winner != 0 {
		return if winner == me { (m, w) } else { (m, 0) };
	}
	let empty = count_empty(board);
	if empty == 0 {
		return (m, d);
	}
	let mut score = 0;
	let mut outcomes = 0;
	for i in 0..9 {
		if board[i] != 0 {
			continue;
		}
		let copy = &mut [0u8; 9];
		copy.copy_from_slice(board);
		copy[i] = get_turn(me, other, first, empty);
		let (sub_outcomes, sub_score) = sa_r_sub_get_score(me, other, first, copy, m, w, d);
		outcomes += sub_outcomes;
		score += sub_score;
	}
	(outcomes, score)
}

#[wasm_bindgen]
pub fn mm_get_score(me: u8, other: u8, first: bool, board: &[u8]) -> f64 {
	mm_sub_get_score(me, other, first, board, 10.0, 0.0, 0.0)
}

#[wasm_bindgen]
pub fn mm_d_get_score(me: u8, other: u8, first: bool, board: &[u8]) -> f64 {
	mm_sub_get_score(me, other, first, board, 10.0, 0.0, 1.0)
}

// m = score (without depth) multiplier
// dm = depth multiplier
pub fn mm_sub_get_score(me: u8, other: u8, first: bool, board: &[u8], m: f64, depth: f64, dm: f64) -> f64 {
	let winner = find_winner(board);
	if winner != 0 {
		return if winner == me { m - depth*dm } else { -m + depth*dm };
	}
	let empty = count_empty(board);
	if empty == 0 {
		return 0.0;
	}
	let turn = get_turn(me, other, first, empty);
	let mut best = if turn == me { f64::MIN } else { f64::MAX };
	for i in 0..9 {
		if board[i] != 0 {
			continue;
		}
		let copy = &mut [0u8; 9];
		copy.copy_from_slice(board);
		copy[i] = get_turn(me, other, first, empty);
		let value = mm_sub_get_score(me, other, first, copy, m, depth + 1.0, dm);
		best = if turn == me { best.max(value) } else { best.min(value) };
	}
	best
}

// Algorithms:
// sa: score adding without optimizations
// sa+rd: score adding with ratio optimization including draws
// sa+r-d: score adding with ratio optimization excluding draws (draw = loose)
// mm: minimax algorithm
// mm+d: minmax algorithm with depth
#[wasm_bindgen]
pub fn get_score(me: u8, other: u8, first: bool, board: &[u8], algorithm: &str) -> f64 {
	match algorithm {
		"sa" => sa_get_score(me, other, first, board),
		"sa+rd" => sa_rd_get_score(me, other, first, board),
		"sa+r-d" => sa_r_d_get_score(me, other, first, board),
		"mm" => mm_get_score(me, other, first, board),
		"mm+d" => mm_d_get_score(me, other, first, board),
		_ => 0.0
	}
}

// Algorithms:
// sa: score adding without optimizations
// sa+rd: score adding with ratio optimization including draws
// sa+r-d: score adding with ratio optimization excluding draws (draw = loose)
// mm: minimax algorithm
// mm+d: minmax algorithm with depth
#[wasm_bindgen]
pub fn predict(me: u8, other: u8, first: bool, board: &[u8], algorithm: &str) -> usize {
	let (mut max_p, mut max_s) = (0, f64::MIN);
	let empty = count_empty(board);
	if empty == 0 {
		return 0;
	}
	for i in 0..9 {
		if board[i] != 0 {
			continue;
		}
		let copy = &mut [0u8; 9];
		copy.copy_from_slice(board);
		copy[i] = get_turn(me, other, first, empty);
		let score = get_score(me, other, first, copy, algorithm);
		if score > max_s {
			(max_p, max_s) = (i, score);
		}
	}
	max_p
}