fix: bug in shuffle sequence on button click

The passed empty value index was wrong.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "slide-puzzle"
-version = "0.3.0"
+version = "0.3.1"
 edition = "2021"
 
 [lib]

src/board.rs

@@ -113,7 +113,7 @@ where
 
 /// Get the index of a value in a slice.
 ///
-/// This is a convenience wrapper and panics if the value cannot be found.
+/// This is a convenience wrapper which should not be used in a hot path.
 pub(crate) fn get_idx_of_val(slice: &[u8], value: u8) -> Result<usize, Error> {
     slice
         .iter()
@@ -127,6 +127,10 @@ pub(crate) fn initialize_fields(num_elements: usize) -> Vec<u8> {
     (0..num_elements).collect()
 }
 
+pub(crate) fn get_empty_field_idx(fields: &[u8]) -> Result<usize, Error> {
+    get_idx_of_val(fields, fields.len() as u8 - 1)
+}
+
 /// Get the indices of neighbours that can be swapped with the empty field.
 pub(crate) fn get_swappable_neighbours(
     width: usize,

src/lib.rs

@@ -39,5 +39,3 @@ pub fn wasm_main() {
 
     unlock_ui();
 }
-
-// TODO: Solver not attempting / button greyed out at a certain size

src/solver/divide_and_conquer.rs

@@ -10,8 +10,8 @@ use simple_error::bail;
 
 use crate::{
     board::{
-        get_coords_from_idx, get_idx_from_coords, get_idx_of_val, in_bounds, initialize_fields,
-        Coords,
+        get_coords_from_idx, get_empty_field_idx, get_idx_from_coords, get_idx_of_val, in_bounds,
+        initialize_fields, Coords,
     },
     Error,
 };
@@ -47,8 +47,7 @@ impl DacPuzzleSolver {
             bail!("DacPuzzleSolver: Puzzles below 3x3 are not supported");
         }
 
-        let empty_field_val = (width * height - 1) as u8;
-        let empty_field_idx = get_idx_of_val(fields, empty_field_val)? as i32;
+        let empty_field_idx = get_empty_field_idx(fields)? as i32;
         let empty_field_pos = get_coords_from_idx(empty_field_idx, width);
 
         Ok(Self {

src/solver/optimal.rs

@@ -13,7 +13,7 @@ use fnv::FnvHasher;
 use rustc_hash::FxHashMap;
 
 use crate::{
-    board::{get_idx_of_val, get_swappable_neighbours, initialize_fields},
+    board::{get_empty_field_idx, get_swappable_neighbours, initialize_fields},
     Error,
 };
 
@@ -40,8 +40,7 @@ pub fn find_swap_order(
         return Ok(Vec::with_capacity(0));
     }
 
-    let empty_field_id = (width * height - 1) as u8;
-    let empty_field_idx = get_idx_of_val(&fields, empty_field_id)?;
+    let empty_field_idx = get_empty_field_idx(&fields)?;
 
     // Map from a state hash to its parent hash and the last swap that led to
     // this state from the parent. We need to the swap information to trace back

src/ui/board.rs

@@ -2,7 +2,9 @@ use wasm_bindgen::{prelude::Closure, JsCast as _};
 use web_sys::{window, CssStyleDeclaration, Document, MouseEvent, Node};
 
 use crate::{
-    board::get_row_col_from_idx, board::Board, ui::search_params::Parameters, ui::ui_locked, BOARD,
+    board::{get_row_col_from_idx, Board},
+    ui::{search_params::Parameters, ui_locked},
+    BOARD,
 };
 
 pub(crate) struct UiBoard {

src/ui/buttons.rs

@@ -2,7 +2,7 @@ use wasm_bindgen::prelude::*;
 use web_sys::{window, HtmlElement, MouseEvent};
 
 use crate::{
-    board::get_shuffle_sequence,
+    board::{get_empty_field_idx, get_shuffle_sequence},
     solver::{divide_and_conquer::DacPuzzleSolver, optimal::find_swap_order},
     ui::{
         lock_ui,
@@ -60,7 +60,8 @@ fn get_quick_swap_callback(size: usize) -> Closure<dyn FnMut(MouseEvent)> {
             return;
         }
 
-        let empty_field_idx = size - 1;
+        let empty_field_idx =
+            BOARD.with_borrow(|b| get_empty_field_idx(b.board().indices2ids()).unwrap());
 
         match get_shuffle_sequence(size, empty_field_idx, 20) {
             Ok(shuffle_sequence) => {
@@ -88,7 +89,8 @@ fn get_granular_swap_callback(size: usize) -> Closure<dyn FnMut(MouseEvent)> {
         }
 
         let num_shuffles = NUM_SHUFFLES;
-        let empty_field_idx = size - 1;
+        let empty_field_idx =
+            BOARD.with_borrow(|b| get_empty_field_idx(b.board().indices2ids()).unwrap());
 
         match get_shuffle_sequence(size, empty_field_idx, num_shuffles) {
             Ok(shuffle_sequence) => {

src/ui/mod.rs

@@ -45,3 +45,4 @@ pub(crate) fn ui_locked() -> bool {
 }
 
 // TODO: Change button colors when locking UI.
+// TODO: Solver not attempting / button greyed out at a certain size