1 files changed, 110 insertions, 0 deletions

diff --git a/src/WixToolset.Core/Preprocess/IfContext.cs b/src/WixToolset.Core/Preprocess/IfContext.cs
new file mode 100644
index 00000000..64b5bd91
--- /dev/null
+++ b/src/WixToolset.Core/Preprocess/IfContext.cs
@@ -0,0 +1,110 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Preprocess
+{
+    using System;
+
+    /// <summary>
+    /// Current state of the if context.
+    /// </summary>
+    internal enum IfState
+    {
+        /// <summary>Context currently in unknown state.</summary>
+        Unknown,
+
+        /// <summary>Context currently inside if statement.</summary>
+        If,
+
+        /// <summary>Context currently inside elseif statement..</summary>
+        ElseIf,
+
+        /// <summary>Conext currently inside else statement.</summary>
+        Else,
+    }
+
+    /// <summary>
+    /// Context for an if statement in the preprocessor.
+    /// </summary>
+    internal sealed class IfContext
+    {
+        private bool active;
+        private bool keep;
+        private bool everKept;
+        private IfState state;
+
+        /// <summary>
+        /// Creates a default if context object, which are used for if's within an inactive preprocessor block
+        /// </summary>
+        public IfContext()
+        {
+            this.active = false;
+            this.keep = false;
+            this.everKept = true;
+            this.state = IfState.If;
+        }
+
+        /// <summary>
+        /// Creates an if context object.
+        /// </summary>
+        /// <param name="active">Flag if context is currently active.</param>
+        /// <param name="keep">Flag if context is currently true.</param>
+        /// <param name="state">State of context to start in.</param>
+        public IfContext(bool active, bool keep, IfState state)
+        {
+            this.active = active;
+            this.keep = keep;
+            this.everKept = keep;
+            this.state = state;
+        }
+
+        /// <summary>
+        /// Gets and sets if this if context is currently active.
+        /// </summary>
+        /// <value>true if context is active.</value>
+        public bool Active
+        {
+            get { return this.active; }
+            set { this.active = value; }
+        }
+
+        /// <summary>
+        /// Gets and sets if context is current true.
+        /// </summary>
+        /// <value>true if context is currently true.</value>
+        public bool IsTrue
+        {
+            get
+            {
+                return this.keep;
+            }
+
+            set
+            {
+                this.keep = value;
+                if (this.keep)
+                {
+                    this.everKept = true;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets if the context was ever true.
+        /// </summary>
+        /// <value>True if context was ever true.</value>
+        public bool WasEverTrue
+        {
+            get { return this.everKept; }
+        }
+
+        /// <summary>
+        /// Gets the current state of the if context.
+        /// </summary>
+        /// <value>Current state of context.</value>
+        public IfState IfState
+        {
+            get { return this.state; }
+            set { this.state = value; }
+        }
+    }
+}