From b109c0d0824145e55e0de7c022964324da6a4376 Mon Sep 17 00:00:00 2001
From: Oliver-Akins <Tyler.Akins1999@gmail.com>
Date: Sat, 8 Jan 2022 21:34:03 -0600
Subject: [PATCH] Add the algorithm for helping with ship movement

---
 common/src/algorithms/movementDirection.ts | 84 ++++++++++++++++++++++
 common/src/index.ts                        |  3 +
 2 files changed, 87 insertions(+)
 create mode 100644 common/src/algorithms/movementDirection.ts

diff --git a/common/src/algorithms/movementDirection.ts b/common/src/algorithms/movementDirection.ts
new file mode 100644
index 0000000..d9f0dda
--- /dev/null
+++ b/common/src/algorithms/movementDirection.ts
@@ -0,0 +1,84 @@
+/**
+ * A helper method for counting how many ships are on each side of a specific
+ * ship on the board.
+ *
+ * @param board The array of spaces that represents the Gravwell board
+ * @param shipLocation The index of the ship that we are counting the number of
+ *		ships on each side for.
+ * @returns An object containing the number of ships that are on each side of
+ *		the target ship
+ */
+function countShips(board: string[], shipLocation: number) {
+	return {
+		left: board.slice(1, shipLocation - 1).filter(x => x != null).length,
+		right: board.slice(shipLocation + 1).filter(x => x != null).length,
+	};
+};
+
+/**
+ * The algorithm to determine which direction the closest ship is, this uses an
+ * integer that can be multiplied by the player's fuel card magnitude in order
+ * to determine the delta for the board index.
+ *
+ * ---
+ *
+ * Possible Return Values:
+ * - `-1` = Away from the Warp Gate
+ * - `0` = Not moving
+ * - `1` = Towards the Warp Gate
+ */
+export function determineDirection(board: string[], shipLocation: number) {
+	let delta = 1;
+
+	while (true) {
+		// The left side of the board is out of range, nearest ship is always
+		// right
+		if (shipLocation - delta <= 0) {
+			return 1;
+		}
+
+		// The right side of the board is out of range, nearest ship is always
+		// left
+		else if (shipLocation + delta >= board.length) {
+			return -1;
+		}
+
+		// Both sides are still in range, continue
+		else {
+
+			let left = board[shipLocation - delta];
+			let right = board[shipLocation + delta];
+
+			// Nearest ships are equidistant, fallback to sum
+			if (left != null && right != null) {
+				let sum = countShips(board, shipLocation);
+
+				// More ships on the left, going backwards
+				if (sum.left > sum.right) {
+					return -1;
+				}
+
+				// more ships on the right, going forward
+				else if (sum.left < sum.right) {
+					return 1;
+				}
+
+				// Equal number of ships, staying still
+				else {
+					return 0;
+				};
+			}
+
+			// Left side of ship is closer
+			else if (left != null) {
+				return -1;
+			}
+
+			// Right side of ship is closer
+			else if (right != null) {
+				return 1;
+			};
+			delta++;
+		};
+	};
+};
\ No newline at end of file
diff --git a/common/src/index.ts b/common/src/index.ts
index f9abf23..c211a31 100644
--- a/common/src/index.ts
+++ b/common/src/index.ts
@@ -1,6 +1,9 @@
 // Enums
 	export { Status } from "./enums/Status";
 
+// Algorithms
+	export * from "./algorithms/movementDirection";
+
 // Data Structures
 	export * from "./types/Colour";
 	export * from "./types/Spaceship";