2 files changed, 78 insertions, 5 deletions
diff --git a/src/lib/Saving.ts b/src/lib/Saving.ts
new file mode 100644
index 0000000..0d71057
--- /dev/null
+++ b/src/lib/Saving.ts
@@ -0,0 +1,25 @@
+import type { Grid } from "./Sudoku";
+
+export function save(grid: Grid) {
+  const a = document.createElement("a");
+  const fileParts = [JSON.stringify(grid)];
+  const blob = new Blob(fileParts, { type: 'application/json' }); // the blob
+  a.href = URL.createObjectURL(blob);
+  a.download = "sudoku-save.json";
+  a.click();
+}
+export function readGridFromFile(f: File): Promise<string[][] | null> {
+  return new Promise(res => {
+    let reader = new FileReader();
+    reader.onload = e => {
+      try {
+        //@ts-expect-error
+        const json = JSON.parse(e.target.result);
+        res(json)
+      } catch (error) {
+        res(null)
+      }
+    };
+    reader.readAsText(f);
+  })
+}
diff --git a/src/lib/Sudoku.ts b/src/lib/Sudoku.ts
index 0da0d77..94b972e 100644
--- a/src/lib/Sudoku.ts
+++ b/src/lib/Sudoku.ts
@@ -1,9 +1,57 @@
-import sudoku from "sudoku-umd";
+export type Grid = Array<Array<string>>;
+export type Coord = { x: number; y: number };
 
-type Grid = Array<Array<string>>;
+export function validate(board: Grid) {
+  const bads = [] as Coord[];
+  for (let i = 0; i < 9; i++) {
+    for (let j = 0; j < 9; j++) {
+      const value = board[i][j];
+      if (value !== '.') {
+        if (!validateRow(board, i, j, value) || !validateColumn(board, i, j, value) || !validateBox(board, i, j, value)) {
+          bads.push({ x: i, y: j })
+        }
+      }
+    }
+  }
+  return bads;
+};
 
-export function validate(grid: Grid) {
-  const list = sudoku.board_grid_to_string(grid)
+function validateRow(board: Grid, row: number, col: number, value: string) {
+  for (let j = 0; j < 8; j++) {
+    if (j !== col) {
+      if (board[row][j] === value) {
+        return false;
+      }
+    }
+  }
 
-  return true
+  return true;
+}
+
+function validateColumn(board: Grid, row: number, col: number, value: string) {
+  for (let i = 0; i < 8; i++) {
+    if (i !== row) {
+      if (board[i][col] === value) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+function validateBox(board: Grid, row: number, col: number, value: string) {
+  const startRow = row - (row % 3), startCol = col - (col % 3);
+
+  for (let i = startRow; i < startRow + 3; i++) {
+    for (let j = startCol; j < startCol + 3; j++) {
+      if (i !== row && j !== col) {
+        if (board[i][j] === value) {
+          return false;
+        }
+      }
+    }
+  }
+
+  return true;
 }