better errors

src/main.rs

@@ -7,12 +7,32 @@ use std::process;
 use text_io::read;
 use std::cmp::min;
 
+const CHAR_SET: &str = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
 enum LineType {
 	Top,
 	Middle,
 	Bottom,
 }
 
+enum WaveError {
+	Contradiction,
+	NoEmptyCell,
+	NoPossibility,
+	NoHistory,
+}
+
+impl fmt::Display for WaveError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+        	WaveError::Contradiction => write!(f, "Error: The puzzle contradicts itself."),
+            WaveError::NoEmptyCell => write!(f, "Error: No empty cells left to fill."),
+            WaveError::NoPossibility => write!(f, "Error: The cell has no possibility."),
+            WaveError::NoHistory => write!(f, "Error: Tried to backtrack but the History is empty."),
+        }
+    }
+}
+
 enum DisplayMode {
 	Full,
 	Focus(usize),
@@ -53,11 +73,16 @@ impl Cell {
 
 impl fmt::Display for Cell {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if let Some(value) = self.value {
+        let Some(value) = self.value else {
-			write!(f, "{}", to_base35(value))
+        	return write!(f, " ")
-        } else {
+        };
-        	write!(f, " ")
+        
-        }
+        let display_value = match CHAR_SET.chars().nth(value) {
+       		Some(value) => value.to_string(),
+       		None => "#".to_string(),
+       	};
+
+		write!(f, "{}", display_value)
     }
 }
 
@@ -79,7 +104,6 @@ impl Sudoku {
 	fn new(order: usize) -> Self {
 		let size = order*order;
 		let sudoku_grid: Vec<Vec<Cell>> = vec![vec![Cell::new(size); size]; size];
-
 		Self {
 			grid: sudoku_grid,
 			rng: rand::thread_rng(),
@@ -112,7 +136,6 @@ impl Sudoku {
         	}
         	println!("{}",line);
         }
-        
    		self.draw_line(LineType::Bottom);
     }
 
@@ -122,7 +145,6 @@ impl Sudoku {
     		LineType::Middle => ("╠", "╬", "╣"),
     		LineType::Bottom => ("╚", "╩", "╝"),
     	};
-    	
     	let mut line = left_corner.to_string();
          for i in 0..(self.square_size) {
          	line += &"═".repeat(self.square_size*2+1);
@@ -133,7 +155,7 @@ impl Sudoku {
          println!("{}{}", line, right_corner);
     }
 
-    fn update_possibilities(&mut self) {
+    fn update_possibilities(&mut self) -> Result<(), WaveError> {
     	let mut row_used_values: Vec<HashSet<usize>> = vec![HashSet::new(); self.size];
     	let mut column_used_values: Vec<HashSet<usize>> = vec![HashSet::new(); self.size];
     	let mut square_used_values: Vec<Vec<HashSet<usize>>> = vec![vec![HashSet::new(); self.square_size]; self.square_size];
@@ -143,6 +165,9 @@ impl Sudoku {
 				let Some(value) = self.grid[row_index][column_index].value else {
 					continue
 				};
+				if row_used_values[row_index].contains(&value) || column_used_values[column_index].contains(&value) || column_used_values[column_index].contains(&value) {
+					return Err(WaveError::Contradiction)
+				}
 				row_used_values[row_index].insert(value);
 				column_used_values[column_index].insert(value);
 				square_used_values[row_index/self.square_size][column_index/self.square_size].insert(value);
@@ -158,19 +183,19 @@ impl Sudoku {
 				self.grid[row_index][column_index].remove_possibilities(&used_values);
 			}
 		}
+		Ok(())
     }
 
-    fn propagate_collapse(&mut self, _debug_display: bool) {
+    fn propagate_collapse(&mut self, _debug_display: bool) -> Result<(), WaveError> {
     	let Some(last_choice) = self.history.last() else {
-    		self.update_possibilities();
+    		return self.update_possibilities()
-    		return
     	};
     	
     	let collapsed_row = last_choice.cell_selected[0];
     	let collapsed_column = last_choice.cell_selected[1];
     	
 		let Some(collapsed_value) = self.grid[collapsed_row][collapsed_column].value else {
-			return
+			return Ok(())
 		};
 
     	let mut collapsed_possibility = HashSet::new();
@@ -191,9 +216,10 @@ impl Sudoku {
     			self.grid[row][column].remove_possibilities(&collapsed_possibility);
     		}
     	}
+    	Ok(())
     }
 
-    fn collapse(&mut self, debug_display: bool) -> bool {
+    fn collapse(&mut self, debug_display: bool) -> Result<(), WaveError> {
 		let mut min_row_index: usize = 0;
 		let mut min_column_index: usize = 0;
 		let mut min_len: usize = self.size;
@@ -219,13 +245,21 @@ impl Sudoku {
     		if debug_display {
     			println!("x no empty cells");
     		}
-    		return false
+    		return Err(WaveError::NoEmptyCell)
     	}
 
-    	if self.collapse_cell(min_row_index, min_column_index, debug_display) {
+    	let Err(reason) = self.collapse_cell(min_row_index, min_column_index, debug_display) else {
-   	        return true
+    		return Ok(())
+    	};
+
+    	if let WaveError::NoPossibility = reason {
+    		return self.backtrack(debug_display)
+    	} else {
+    		return Err(reason)
+    	}
 	}
 
+	fn backtrack(&mut self, debug_display: bool) -> Result<(), WaveError> {
 		let mut fork: Option<Choice> = None;
 		
         while let Some(choice) = self.history.pop() {
@@ -243,10 +277,10 @@ impl Sudoku {
         	if debug_display {
         		println!("x backtracked to start");
         	}
-        	return false
+        	return Err(WaveError::NoHistory)
         };
         
-       	self.reset_possibilities();
+       	self.reset_possibilities()?;
 
        	let mut selected_value = HashSet::new();
        	selected_value.insert(choice.selected_value);
@@ -255,22 +289,22 @@ impl Sudoku {
        	return self.collapse_cell(choice.cell_selected[0], choice.cell_selected[1], debug_display)
 	}
 
-    fn reset_possibilities(&mut self) {
+    fn reset_possibilities(&mut self) -> Result<(), WaveError> {
     	for row in &mut self.grid {
     		for cell in row {
     			cell.reset_possibilities();
     		}
     	}
     	
-        self.update_possibilities();
+        return self.update_possibilities();
     }
 
-    fn collapse_cell(&mut self, row_index: usize, column_index: usize, debug_display: bool) -> bool {
+    fn collapse_cell(&mut self, row_index: usize, column_index: usize, debug_display: bool) -> Result<(), WaveError> {
     	let Some(&selected_value) = self.grid[row_index][column_index].possibilities.choose(&mut self.rng) else {
 			if debug_display {
    	    		println!("x no possibilities for [{}][{}]", row_index, column_index);
    	    	}
-			return false
+			return Err(WaveError::NoPossibility)
 		};
 
     	self.history.push(Choice {
@@ -283,10 +317,10 @@ impl Sudoku {
   	    if debug_display {
 			println!("# collapsing [{}][{}] ({:?}) to {}", row_index, column_index, self.grid[row_index][column_index].possibilities, selected_value);
 		}
-		return true
+		Ok(())
 	}
 
-	fn solve(&mut self, debug_display: bool) {
+	fn solve(&mut self, debug_display: bool) -> Result<(), WaveError> {
 		let now = Instant::now();
 		
 		self.display(DisplayMode::Full);
@@ -303,15 +337,26 @@ impl Sudoku {
 	    	}
 	    }
 
+	    let initial_grid = self.grid.clone();
+	    
 		println!("# started");
 	    
-	    self.update_possibilities();
+	    self.update_possibilities()?;
-		let mut counter: usize = 0;
 	    
-	    while self.collapse(debug_display) {
+		let mut step_counter: usize = 0;
+		let mut reset_counter: usize = 0;
+		
+	    while let Ok(_) = self.collapse(debug_display) {
 	    	//self.update_possibilities();
-	    	self.propagate_collapse(debug_display);
+	    	self.propagate_collapse(debug_display)?;
-	    	counter +=1;
+	    	step_counter += 1;
+
+	    	if step_counter%(2*self.size*self.size) == 0 {
+	    		self.grid = initial_grid.clone();
+	    		self.update_possibilities()?;
+	    		self.history = vec![];
+	    		reset_counter += 1;
+	    	}
 
 			if !debug_display {
 				let bar_size = (self.size + self.square_size - 1)*2 + 1;
@@ -320,6 +365,7 @@ impl Sudoku {
 		    	print!("\r[{}{}]", "#".repeat(progress), "-".repeat(to_do));
 		    }
 	    }
+	    
 	    println!();
 
 	    let elapsed = now.elapsed();
@@ -327,8 +373,13 @@ impl Sudoku {
 		if debug_display {
 	    	println!("--------");
 	    }
-	    println!("# finished in {} steps, {:.2?} ({:.2?}/step)", counter, elapsed, elapsed/(counter as u32));
+	    println!("# finished in {} steps, {:.2?} ({:.2?}/step)", step_counter, elapsed, elapsed/(step_counter as u32));
+		if reset_counter > 0 {
+			println!("# {} resets", reset_counter);
+		}
 	    self.display(DisplayMode::Full);
+	    
+	    Ok(())
 	}
 
 	fn ask(&mut self) {
@@ -337,7 +388,7 @@ impl Sudoku {
 			print!("> ");
 			let line: String = read!("{}\n");
 			for (column_index, c) in line.chars().enumerate() {
-			    match "0123456789abcdefghijklmnopqrstuvwxyz".find(c) {
+			    match CHAR_SET.find(c) {
 			        Some(value) => {
 			            if value <= self.size {
 			                self.grid[row_index][column_index].set(value);
@@ -348,7 +399,7 @@ impl Sudoku {
 			}
 			let height = self.size + self.square_size + 2;
 			print!("\x1b[{}A", height);
-			for i in 0..height {
+			for _ in 0..height {
 				println!("{}"," ".repeat((self.size + self.square_size - 1)*2 + 5));
 			}
 			print!("\x1b[{}A", height);
@@ -356,24 +407,6 @@ impl Sudoku {
 	}
 }
 
-fn to_base35(mut n: usize) -> String {
-    let chars = "0123456789abcdefghijklmnopqrstuvwxyz";
-    if n == 0 {
-        return chars[0..1].to_string(); // Special case for 0
-    }
-
-    let mut result = String::new();
-
-    while n > 0 {
-        let remainder = n % 35;
-        result.push(chars.chars().nth(remainder).unwrap());
-        n /= 35;
-    }
-
-    // The result will be in reverse order, so we need to reverse it
-    result.chars().rev().collect()
-}
-
 fn main() {
 	let args: Vec<String> = env::args().collect();
 	if args.len() < 2 {
@@ -392,5 +425,7 @@ fn main() {
     	sudoku.ask();
     }
     
-	sudoku.solve(args.contains(&"--debug".to_string()));
+	if let Err(reason) = sudoku.solve(args.contains(&"--debug".to_string())) {
+		println!("{}",reason);
+	}
 }