3 files changed, 47 insertions, 2 deletions
diff --git a/app/src/main/java/space/jakob/mines/GameActivity.kt b/app/src/main/java/space/jakob/mines/GameActivity.kt
index b6135b3..5a44720 100644
--- a/app/src/main/java/space/jakob/mines/GameActivity.kt
+++ b/app/src/main/java/space/jakob/mines/GameActivity.kt
@@ -42,6 +42,13 @@ class GameActivity : AppCompatActivity() {
             }
             return false
         }
+
+        override fun onLongPress(e: MotionEvent) {
+            with (gameView) {
+                flagAt(e.x.toInt(), e.y.toInt())
+                invalidate()
+            }
+        }
     }
 
     // Implements the callbacks for scaleGestureDetector.
diff --git a/app/src/main/java/space/jakob/mines/GameView.kt b/app/src/main/java/space/jakob/mines/GameView.kt
index 118cb45..d0a7ae0 100644
--- a/app/src/main/java/space/jakob/mines/GameView.kt
+++ b/app/src/main/java/space/jakob/mines/GameView.kt
@@ -97,6 +97,19 @@ class GameView(context: Context, attrs: AttributeSet) : View(context, attrs) {
         }
     }
 
+    /**
+     * Flag and @return the tile at (@param x, @param y).
+     */
+    fun flagAt(x: Int, y: Int): Tile? = grid?.let {
+        val (x, y) = toGridCoordinates(x.toInt(), y.toInt())
+        if (it.valid(x, y)) {
+            it.flag(x, y)
+            return it[x, y]
+        } else {
+            return null
+        }
+    }
+
     private fun atlasRect(entry: AtlasEntry): Rect {
         val atlasWidth = 3
 
@@ -111,7 +124,6 @@ class GameView(context: Context, attrs: AttributeSet) : View(context, attrs) {
         val xSpacing = (scaledTileWidth * tileSpacing).toInt()
         val ySpacing = (scaledTileWidth * tileSpacing).toInt()
 
-        // TODO: Opportunity for more ASCII art explanations :)
         val dst = Rect(
             x + xSpacing,
             y + ySpacing,
@@ -121,6 +133,10 @@ class GameView(context: Context, attrs: AttributeSet) : View(context, attrs) {
 
         if (tile.masked) {
             canvas.drawBitmap(atlas, atlasRect(AtlasEntry.MASKED), dst, null)
+
+            if (tile.flagged) {
+                canvas.drawBitmap(atlas, atlasRect(AtlasEntry.FLAG), dst, null)
+            }
         } else {
             canvas.drawBitmap(atlas, atlasRect(AtlasEntry.UNMASKED), dst, null)
 
diff --git a/app/src/main/java/space/jakob/mines/Grid.kt b/app/src/main/java/space/jakob/mines/Grid.kt
index 2eec411..963f8cb 100644
--- a/app/src/main/java/space/jakob/mines/Grid.kt
+++ b/app/src/main/java/space/jakob/mines/Grid.kt
@@ -14,7 +14,12 @@ package space.jakob.mines
 
 import java.util.Random
 
-data class Tile(val adjacentMines: Int = 0, val mine: Boolean = false, val masked: Boolean = true)
+data class Tile(
+    val adjacentMines: Int = 0,
+    val mine: Boolean = false,
+    val masked: Boolean = true,
+    val flagged: Boolean = false
+)
 
 /**
  * The Minesweeper "grid", containing instances of [Tile].
@@ -118,6 +123,23 @@ class Grid(val width: Int, val height: Int, val tiles: Array<Tile>) {
         }
     }
 
+    /**
+     * Mark the tile at the given coordinates as flagged.
+     *
+     * @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 flag(x: Int, y: Int) {
+        if (!valid(x, y) || !this[x, y].masked) {
+            return;
+        }
+
+        with (this[x, y]) {
+            place(x, y, copy(flagged = true))
+        }
+    }
+
     override fun toString(): String = buildString {
         for (y in 0 until height) {
             for (x in 0 until width) {