Beginning of sudoku chapter 7 with SDM loading

piston-tutorials/sudoku/src/gameboard.rs

@@ -2,6 +2,7 @@
 
 const SIZE: usize = 9;
 
+#[derive(Debug, PartialEq)]
 pub struct Gameboard {
     pub cells: [[u8; SIZE]; SIZE],
 }
@@ -12,4 +13,68 @@ impl Gameboard {
             cells: [[0; SIZE]; SIZE],
         }
     }
+
+    pub fn char(&self, ind: [usize; 2]) -> Option<char> {
+        Some(match self.cells[ind[1]][ind[0]] {
+            1 => '1',
+            2 => '2',
+            3 => '3',
+            4 => '4',
+            5 => '5',
+            6 => '6',
+            7 => '7',
+            8 => '8',
+            9 => '9',
+            _ => return None,
+        })
+    }
+
+    pub fn set(&mut self, ind: [usize; 2], val: u8) {
+        self.cells[ind[1]][ind[0]] = val;
+    }
+
+    pub fn load_sdm(filename: &str) -> Self {
+        use std::fs::read_to_string;
+
+        let data = read_to_string(filename).expect("failed to read SDM file");
+        let mut cells = [[0; SIZE]; SIZE];
+        let mut row = 0;
+        let mut col = 0;
+        for c in data.chars() {
+            if col == SIZE {
+                col = 0;
+                row += 1;
+            }
+            if let Some(d) = c.to_digit(10) {
+                cells[row][col] = d as u8;
+                col += 1;
+            }
+        }
+
+        Self { cells }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn load_sdm() {
+        let got = Gameboard::load_sdm("static/puzzle.sdm");
+        let want = Gameboard {
+            cells: [
+                [0, 1, 6, 4, 0, 0, 0, 0, 0],
+                [2, 0, 0, 0, 0, 9, 0, 0, 0],
+                [4, 0, 0, 0, 0, 0, 0, 6, 2],
+                [0, 7, 0, 2, 3, 0, 1, 0, 0],
+                [1, 0, 0, 0, 0, 0, 0, 0, 3],
+                [0, 0, 3, 0, 8, 7, 0, 4, 0],
+                [9, 6, 0, 0, 0, 0, 0, 0, 5],
+                [0, 0, 0, 8, 0, 0, 0, 0, 7],
+                [0, 0, 0, 0, 0, 6, 8, 2, 0],
+            ],
+        };
+        assert_eq!(got, want);
+    }
 }