1 files changed, 139 insertions, 0 deletions
diff --git a/src/SMAPI/Utilities/Keybind.cs b/src/SMAPI/Utilities/Keybind.cs
new file mode 100644
index 00000000..dd8d2861
--- /dev/null
+++ b/src/SMAPI/Utilities/Keybind.cs
@@ -0,0 +1,139 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using StardewModdingAPI.Framework;
+
+namespace StardewModdingAPI.Utilities
+{
+    /// <summary>A single multi-key binding which can be triggered by the player.</summary>
+    /// <remarks>NOTE: this is part of <see cref="KeybindList"/>, and usually shouldn't be used directly.</remarks>
+    public class Keybind
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>Get the current input state for a button.</summary>
+        [Obsolete("This property should only be used for unit tests.")]
+        internal Func<SButton, SButtonState> GetButtonState { get; set; } = SGame.GetInputState;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The buttons that must be down to activate the keybind.</summary>
+        public SButton[] Buttons { get; }
+
+        /// <summary>Whether any keys are bound.</summary>
+        public bool IsBound { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="buttons">The buttons that must be down to activate the keybind.</param>
+        public Keybind(params SButton[] buttons)
+        {
+            this.Buttons = buttons;
+            this.IsBound = buttons.Any(p => p != SButton.None);
+        }
+
+        /// <summary>Parse a keybind string, if it's valid.</summary>
+        /// <param name="input">The keybind string. See remarks on <see cref="ToString"/> for format details.</param>
+        /// <param name="parsed">The parsed keybind, if valid.</param>
+        /// <param name="errors">The parse errors, if any.</param>
+        public static bool TryParse(string input, out Keybind parsed, out string[] errors)
+        {
+            // empty input
+            if (string.IsNullOrWhiteSpace(input))
+            {
+                parsed = new Keybind(SButton.None);
+                errors = new string[0];
+                return true;
+            }
+
+            // parse buttons
+            string[] rawButtons = input.Split('+');
+            SButton[] buttons = new SButton[rawButtons.Length];
+            List<string> rawErrors = new List<string>();
+            for (int i = 0; i < buttons.Length; i++)
+            {
+                string rawButton = rawButtons[i].Trim();
+                if (string.IsNullOrWhiteSpace(rawButton))
+                    rawErrors.Add("Invalid empty button value");
+                else if (!Enum.TryParse(rawButton, ignoreCase: true, out SButton button))
+                {
+                    string error = $"Invalid button value '{rawButton}'";
+
+                    switch (rawButton.ToLower())
+                    {
+                        case "shift":
+                            error += $" (did you mean {SButton.LeftShift}?)";
+                            break;
+
+                        case "ctrl":
+                        case "control":
+                            error += $" (did you mean {SButton.LeftControl}?)";
+                            break;
+
+                        case "alt":
+                            error += $" (did you mean {SButton.LeftAlt}?)";
+                            break;
+                    }
+
+                    rawErrors.Add(error);
+                }
+                else
+                    buttons[i] = button;
+            }
+
+            // build result
+            if (rawErrors.Any())
+            {
+                parsed = null;
+                errors = rawErrors.ToArray();
+                return false;
+            }
+            else
+            {
+                parsed = new Keybind(buttons);
+                errors = new string[0];
+                return true;
+            }
+        }
+
+        /// <summary>Get the keybind state relative to the previous tick.</summary>
+        public SButtonState GetState()
+        {
+            SButtonState[] states = this.Buttons.Select(this.GetButtonState).Distinct().ToArray();
+
+            // single state
+            if (states.Length == 1)
+                return states[0];
+
+            // if any key has no state, the whole set wasn't enabled last tick
+            if (states.Contains(SButtonState.None))
+                return SButtonState.None;
+
+            // mix of held + pressed => pressed
+            if (states.All(p => p == SButtonState.Pressed || p == SButtonState.Held))
+                return SButtonState.Pressed;
+
+            // mix of held + released => released
+            if (states.All(p => p == SButtonState.Held || p == SButtonState.Released))
+                return SButtonState.Released;
+
+            // not down last tick or now
+            return SButtonState.None;
+        }
+
+        /// <summary>Get a string representation of the keybind.</summary>
+        /// <remarks>A keybind is serialized to a string like <c>LeftControl + S</c>, where each key is separated with <c>+</c>. The key order is commutative, so <c>LeftControl + S</c> and <c>S + LeftControl</c> are identical.</remarks>
+        public override string ToString()
+        {
+            return this.Buttons.Length > 0
+                ? string.Join(" + ", this.Buttons)
+                : SButton.None.ToString();
+        }
+    }
+}