Add ability to specify puzzle difficulty and save result to CSV file

src/bin/generator.rs

@@ -1,3 +1,8 @@
+use rand_chacha::ChaCha8Rng;
+use rand::prelude::*;
+use sudoku_solver::grid::{Grid, CellValue};
+use std::error::Error;
+use std::io::Write;
 
 fn main() {
 
@@ -5,6 +10,10 @@ fn main() {
     // Starting default seed will just be based on time
     let mut seed = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).expect("Time went backwards").as_secs();
 
+    let mut max_hints = 81;
+    let mut max_attempts = 100;
+    let mut filename : Option<String> = None;
+
     { // this block limits scope of borrows by ap.refer() method
         let mut ap = argparse::ArgumentParser::new();
         ap.set_description("Generate Sudoku puzzles");
@@ -14,6 +23,15 @@ fn main() {
         ap.refer(&mut seed)
             .add_option(&["--seed"], argparse::Store, "Provide seed for puzzle generation");
 
+        ap.refer(&mut max_hints)
+            .add_option(&["--hints"], argparse::Store, "Only return a puzzle with less than or equal to this number of hints");
+
+        ap.refer(&mut max_attempts)
+            .add_option(&["--attempts"], argparse::Store, "Number of attempts that will be tried to generate such a puzzle; default is 100");
+
+        ap.refer(&mut filename)
+            .add_argument("filename", argparse::StoreOption, "Optional filename to store puzzle in as a CSV");
+
         ap.parse_args_or_exit();
     }
 
@@ -28,9 +46,62 @@ fn main() {
     if debug {
         println!("Using seed {}", seed);
     }
+    let mut rng = ChaCha8Rng::seed_from_u64(seed);
 
-    let (grid, num_hints) = sudoku_solver::generator::generate_grid(seed);
+    let mut num_attempts = 0;
 
-    println!("{}", grid);
-    println!("Puzzle has {} hints", num_hints);
+    let grid = loop {
+        if num_attempts >= max_attempts{
+            println!("Unable to find a puzzle with only {} hints in {} attempts", max_hints, max_attempts);
+            return;
+        }
+
+        let (grid, num_hints) = sudoku_solver::generator::generate_grid(&mut rng);
+        num_attempts = num_attempts + 1;
+
+        if num_hints <= max_hints {
+            println!("{}", grid);
+            println!("Puzzle has {} hints", num_hints);
+            if num_attempts > 1 {
+                println!("It took {} attempts to find this puzzle.", num_attempts);
+            }
+            break grid;
+        }
+    };
+
+    match filename {
+        Some(filename) => {
+            save_grid(&grid, &filename).unwrap();
+            println!("Grid saved to {}", filename);
+        },
+        None => {}
+    }
+
+}
+
+fn save_grid(grid: &Grid, filename: &str) -> Result<(), Box<dyn Error>>{
+    // Not using the csv crate for writing because it's being difficult and won't accept raw integers
+    let mut file = std::fs::File::create(filename)?;
+
+    for x in 0..9 {
+        for y in 0..9 {
+            let cell = grid.get(x, y).unwrap();
+            let value = &*cell.value.borrow();
+            let digit =
+            match value {
+                CellValue::Fixed(digit) => {*digit}
+                CellValue::Unknown(_) => {0}
+            };
+
+            let mut text = digit.to_string();
+            if y < 8 {
+                text.push(',');
+            }
+            file.write(text.as_bytes())?;
+
+        }
+        file.write(b"\n")?;
+    }
+
+    Ok(())
 }

src/generator.rs

@@ -152,8 +152,7 @@ impl Line {
     }
 }
 
-pub fn generate_grid(seed: u64) -> (Grid, i32) {
-    let mut rng = ChaCha8Rng::seed_from_u64(seed);
+pub fn generate_grid(rng: &mut ChaCha8Rng) -> (Grid, i32) {
 
     let mut num_hints;
     let mut grid : Grid = loop {
@@ -167,7 +166,7 @@ pub fn generate_grid(seed: u64) -> (Grid, i32) {
 
         for digit in 1..10 {
             if digit != digit_excluded {
-                let cell = grid.get_random_empty_cell(&mut rng);
+                let cell = grid.get_random_empty_cell(rng);
                 cell.unwrap().set(digit);
                 num_hints = num_hints + 1;
             }
@@ -189,12 +188,12 @@ pub fn generate_grid(seed: u64) -> (Grid, i32) {
     grid =
     'outer: loop {
         num_hints = num_hints + 1;
-        let cell = grid.get_random_empty_cell(&mut rng).unwrap(); // We unwrap because if somehow we're filled each cell without finding a solution, that's reason for a panic
+        let cell = grid.get_random_empty_cell(rng).unwrap(); // We unwrap because if somehow we're filled each cell without finding a solution, that's reason for a panic
         let cell = &*cell;
         let mut cell_possibilities = cell.get_value_possibilities().expect("An empty cell has no possibilities");
 
         // Let's scramble the order
-        cell_possibilities.shuffle(&mut rng);
+        cell_possibilities.shuffle(rng);
 
         for (_index, digit) in cell_possibilities.iter().enumerate() {
 
@@ -244,7 +243,7 @@ pub fn generate_grid(seed: u64) -> (Grid, i32) {
         }
     }
     // Need to randomly reorder non_empty_cells
-    non_empty_cells.shuffle(&mut rng);
+    non_empty_cells.shuffle(rng);
 
     for (_index, cell) in non_empty_cells.iter().enumerate() {
         let grid_clone = grid.clone();