EN605.607.81.SP22_ASDM_Project/front_end/src/ai.rs

324 lines
9.4 KiB
Rust

use std::collections::BTreeMap;
use crate::constants::{AI_EASY_MAX_CHOICES, AI_NORMAL_MAX_CHOICES, COLS, ROWS};
use crate::game_logic::check_win_draw;
use crate::random_helper::get_seeded_random;
use crate::state::{board_deep_clone, BoardState, BoardType, Turn};
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum AIDifficulty {
Easy,
Normal,
Hard,
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum SlotChoice {
Slot0,
Slot1,
Slot2,
Slot3,
Slot4,
Slot5,
Slot6,
Invalid,
}
impl From<SlotChoice> for usize {
fn from(slot_choice: SlotChoice) -> Self {
match slot_choice {
SlotChoice::Slot0 => 0,
SlotChoice::Slot1 => 1,
SlotChoice::Slot2 => 2,
SlotChoice::Slot3 => 3,
SlotChoice::Slot4 => 4,
SlotChoice::Slot5 => 5,
SlotChoice::Slot6 => 6,
SlotChoice::Invalid => (ROWS * COLS) as usize,
}
}
}
impl From<usize> for SlotChoice {
fn from(idx: usize) -> Self {
if idx >= (ROWS * COLS) as usize {
return SlotChoice::Invalid;
}
match idx % (COLS as usize) {
0 => SlotChoice::Slot0,
1 => SlotChoice::Slot1,
2 => SlotChoice::Slot2,
3 => SlotChoice::Slot3,
4 => SlotChoice::Slot4,
5 => SlotChoice::Slot5,
6 => SlotChoice::Slot6,
_ => SlotChoice::Invalid,
}
}
}
pub fn get_ai_choice(
difficulty: AIDifficulty,
player: Turn,
board: &BoardType,
) -> Result<SlotChoice, String> {
let mut rng = get_seeded_random()?;
let mut utilities = Vec::with_capacity(COLS as usize);
for i in 0..(COLS as usize) {
let slot = i.into();
if slot == SlotChoice::Invalid {
return Err("Internal error: get_ai_choice() iterated to SlotChoice::Invalid".into());
}
if let Some(utility) = get_utility_for_slot(player, slot, board) {
utilities.push((i, utility));
}
}
if utilities.is_empty() {
return Err("All slots are full".into());
}
// shuffle utilities for the cases where there are equivalent utilities
if utilities.len() > 1 {
for i in 1..utilities.len() {
utilities.swap(i, rng.rand_range(0..((i + 1) as u32)) as usize);
}
}
let mut pick_some_of_choices = |amount: usize| -> Result<SlotChoice, String> {
let mut maximums: BTreeMap<i64, usize> = BTreeMap::new();
for (idx, utility) in &utilities {
// f64 cannot be used as Key since it doesn't implement Ord.
// Use i64 as a substitute, noting that the map stores in ascending
// order.
let mut utility_value = (utility * 10000.0) as i64;
while maximums.contains_key(&utility_value) {
utility_value += rng.rand_range(0..7) as i64 - 3;
}
maximums.insert(utility_value, *idx);
}
// don't pick from more items than what exists
let mod_amount = if maximums.len() < amount {
maximums.len()
} else {
amount
};
// don't use random if only 1 item is to be picked
let random_number: usize = if mod_amount > 1 {
rng.rand_u32() as usize % mod_amount
} else {
0
};
let rand_idx = maximums.len() - 1 - random_number;
// turns the map into a vector of (key, value), then pick out of the
// last few values by index the "value" which is the SlotChoice.
// This is done because BTreeMap stores keys in ascending order.
Ok((*maximums.iter().collect::<Vec<(&i64, &usize)>>()[rand_idx].1).into())
};
match difficulty {
AIDifficulty::Easy => pick_some_of_choices(AI_EASY_MAX_CHOICES),
AIDifficulty::Normal => pick_some_of_choices(AI_NORMAL_MAX_CHOICES),
AIDifficulty::Hard => {
// only pick the best option all the time
let mut max = -1.0f64;
let mut max_idx: usize = 0;
for (idx, utility) in utilities {
if utility > max {
max = utility;
max_idx = idx;
}
}
Ok(max_idx.into())
}
}
}
/// Returns a value between 0.0 and 1.0 where 1.0 is highest utility
/// "None" indicates it is impossible to place at the given slot
fn get_utility_for_slot(player: Turn, slot: SlotChoice, board: &BoardType) -> Option<f64> {
// get idx of location where dropped token will reside in
let mut idx: usize = slot.into();
if board[idx].get() != BoardState::Empty {
// slot is full, cannot place in slot
return None;
}
while idx < ((ROWS - 1) * COLS) as usize
&& board[idx + COLS as usize].get() == BoardState::Empty
{
idx += COLS as usize;
}
// check if placing a token here is a win
if get_block_amount(player.get_opposite(), idx, 3, board) {
return Some(1.0);
}
// check if placing a token here blocks a win
if get_block_amount(player, idx, 3, board) {
return Some(0.9);
}
let mut utility: f64 = 0.5;
// check if placing a token here connects 2 pieces
if get_block_amount(player.get_opposite(), idx, 2, board) {
utility *= 1.5;
if utility >= 0.8 {
utility = 0.8;
}
}
// check if placing a token here blocks 2 pieces
if get_block_amount(player, idx, 2, board) {
utility *= 1.2;
if utility >= 0.8 {
utility = 0.8;
}
}
// check if placing a token here connects 1 piece
if get_block_amount(player.get_opposite(), idx, 1, board) {
utility *= 1.09;
if utility >= 0.8 {
utility = 0.8;
}
}
// check if placing a token here allows the opposing player to win
if idx >= COLS as usize {
let cloned_board = board_deep_clone(board);
cloned_board[idx].replace(player.into());
cloned_board[idx - (COLS as usize)].replace(player.get_opposite().into());
if let Some((state, _)) = check_win_draw(&cloned_board) {
if state == player.get_opposite().into() {
utility *= 0.1;
}
}
}
Some(utility)
}
/// Returns true if placing a token at idx will block the opposite player that
/// has "amount" in a line (horizontally, vertically, and diagonally).
fn get_block_amount(player: Turn, idx: usize, amount: usize, board: &BoardType) -> bool {
let opposite = player.get_opposite();
// setup for checks
let mut count = 0;
let mut temp_idx = idx;
// check left
while temp_idx % (COLS as usize) > 0 {
temp_idx -= 1;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// check right
// count = 0; // don't reset count, since horizontal may pass through idx
temp_idx = idx;
while temp_idx % (COLS as usize) < (COLS - 1) as usize {
temp_idx += 1;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// check down
count = 0;
temp_idx = idx;
while temp_idx / (COLS as usize) < (ROWS - 1) as usize {
temp_idx += COLS as usize;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// check diagonal left down
count = 0;
temp_idx = idx;
while temp_idx % (COLS as usize) > 0 && temp_idx / (COLS as usize) < (ROWS - 1) as usize {
temp_idx = temp_idx - 1 + COLS as usize;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// check diagonal right up
// count = 0; // don't reset count as diagonal may pass through idx
temp_idx = idx;
while temp_idx % (COLS as usize) < (COLS - 1) as usize && temp_idx / (COLS as usize) > 0 {
temp_idx = temp_idx + 1 - COLS as usize;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// check diagonal right down
count = 0;
temp_idx = idx;
while temp_idx % (COLS as usize) < (COLS - 1) as usize
&& temp_idx / (COLS as usize) < (ROWS - 1) as usize
{
temp_idx = temp_idx + 1 + COLS as usize;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// check diagonal left up
// count = 0; // don't reset count as diagonal may pass through idx
temp_idx = idx;
while temp_idx % (COLS as usize) > 0 && temp_idx / (COLS as usize) > 0 {
temp_idx = temp_idx - 1 - COLS as usize;
if board[temp_idx].get() == opposite.into() {
count += 1;
if count >= amount {
return true;
}
} else {
break;
}
}
// exhausted all possible potential wins, therefore does not block a win
false
}