1 files changed, 113 insertions, 0 deletions
diff --git a/app/src/main/java/space/jakob/mines/Grid.kt b/app/src/main/java/space/jakob/mines/Grid.kt
new file mode 100644
index 0000000..a532632
--- /dev/null
+++ b/app/src/main/java/space/jakob/mines/Grid.kt
@@ -0,0 +1,113 @@
+data class Tile(val adjacentMines: Int = 0, val mine: Boolean = false, val masked: Boolean = true)
+
+/**
+ * The Minesweeper "grid", containing instances of [Tile].
+ */
+class Grid(val width: Int, val height: Int, val tiles: Array<Tile>) {
+    constructor(width: Int = 8, height: Int = 8, mines: Int = 10)
+    : this(width, height, Array<Tile>(width * height) { Tile() }) {
+        for (i in 0 until mines) {
+            val x = (0 until width).random()
+            val y = (0 until height).random()
+            placeMine(x, y)
+        }
+    }
+
+    private fun index(x: Int, y: Int) = y * width + x
+    private fun valid(x: Int, y: Int) = y in 0 until height && x in 0 until width
+    private fun place(x: Int, y: Int, tile: Tile) {
+        tiles[index(x, y)] = tile
+    }
+
+    /**
+     * Returns the tile at the given coordinates.
+     *
+     * @throws IllegalArgumentException if the X coordinate is outside
+     * the range of [0, width), or if the Y coordinate is outside the
+     *  range of [0, height).
+     */
+    operator fun get(x: Int, y: Int) = if (valid(x, y)) {
+        tiles[index(x, y)]
+    } else {
+        throw IllegalArgumentException("Invalid coordinates (${x}, ${y})")
+    }
+
+    /**
+     * Places a mine at the given coordinates.
+     *
+     * @throws IllegalArgumentException if the X coordinate is outside
+     * the range of [0, width), or if the Y coordinate is outside the
+     *  range of [0, height).
+     */
+    fun placeMine(x: Int, y: Int) {
+        if (!valid(x, y)) {
+            throw IllegalArgumentException("Invalid coordinates (${x}, ${y})")
+        }
+
+        if (this[x, y].mine) {
+            return;
+        }
+
+        place(x, y, Tile(mine = true))
+
+        val xMin = (x - 1).coerceAtLeast(0)
+        val xMax = (x + 1).coerceAtMost(width - 1)
+        val yMin = (y - 1).coerceAtLeast(0)
+        val yMax = (y + 1).coerceAtMost(height - 1)
+
+        for (y in yMin..yMax) {
+            for (x in xMin..xMax) {
+                with (tiles[index(x, y)]) {
+                    if (!mine) {
+                        place(x, y, copy(adjacentMines + 1))
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Reveals a tile at the given coordinates according to the game rules.
+     *
+     * @throws IllegalArgumentException if the X coordinate is outside
+     * the range of [0, width), or if the Y coordinate is outside the
+     *  range of [0, height).
+     */
+    fun reveal(x: Int, y: Int) {
+        if (!valid(x, y) || !this[x, y].masked) {
+            return;
+        }
+
+        with (this[x, y]) {
+            place(x, y, copy(masked = false))
+
+            if (!mine && adjacentMines == 0) {
+                val xMin = (x - 1).coerceAtLeast(0)
+                val xMax = (x + 1).coerceAtMost(width - 1)
+                val yMin = (y - 1).coerceAtLeast(0)
+                val yMax = (y + 1).coerceAtMost(height - 1)
+
+                for (y in yMin..yMax) {
+                    for (x in xMin..xMax) {
+                        reveal(x, y)
+                    }
+                }
+            }
+        }
+    }
+
+    override fun toString(): String = buildString {
+        for (y in 0 until height) {
+            for (x in 0 until width) {
+                val tile = this@Grid[x, y]
+                append(when {
+                    tile.masked -> "."
+                    tile.mine -> "M"
+                    tile.adjacentMines == 0 -> " "
+                    else -> tile.adjacentMines.toString()
+                } + " ")
+            }
+            append("\n")
+        }
+    }
+}