Add a class to handle token operations

Author: Kapil Borle

Engine/ScriptAnalyzerEngine.csproj

@@ -101,6 +101,7 @@
       <DesignTime>True</DesignTime>
       <DependentUpon>Strings.resx</DependentUpon>
     </Compile>
+    <Compile Include="TokenOperations.cs" />
     <Compile Include="VariableAnalysis.cs" />
     <Compile Include="VariableAnalysisBase.cs" />
   </ItemGroup>

Engine/TokenOperations.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Management.Automation.Language;
+
+namespace Microsoft.Windows.PowerShell.ScriptAnalyzer
+{
+    // TODO Move all token query related methods here
+    /// <summary>
+    /// A class to encapsulate all the token querying operations.
+    /// </summary>
+    public class TokenOperations
+    {
+        private readonly Token[] tokens;
+        private readonly Ast ast;
+
+        /// <summary>
+        /// Initializes the fields of the TokenOperations class.
+        /// </summary>
+        /// <param name="tokens">Tokens referring to the input AST.</param>
+        /// <param name="ast">AST that needs to be analyzed.</param>
+        public TokenOperations(Token[] tokens, Ast ast)
+        {
+            if (tokens == null)
+            {
+                throw new ArgumentNullException(nameof(tokens));
+            }
+
+            if (ast == null)
+            {
+                throw new ArgumentNullException(nameof(ast));
+            }
+
+            this.tokens = tokens;
+            this.ast = ast;
+        }
+
+        /// <summary>
+        /// Return tokens of kind LCurly that begin a scriptblock expression in an command element.
+        ///
+        /// E.g. Get-Process * | where { $_.Name -like "powershell" }
+        /// In the above example it will return the open brace following the where command.
+        /// </summary>
+        /// <returns>An enumerable of type Token</returns>
+        public IEnumerable<Token> GetOpenBracesInCommandElements()
+        {
+            return GetBraceInCommandElement(TokenKind.LCurly);
+        }
+
+
+        /// <summary>
+        /// Return tokens of kind RCurly that end a scriptblock expression in an command element.
+        ///
+        /// E.g. Get-Process * | where { $_.Name -like "powershell" }
+        /// In the above example it will return the close brace following "powershell".
+        /// </summary>
+        /// <returns>An enumerable of type Token</returns>
+        public IEnumerable<Token> GetCloseBraceInCommandElement()
+        {
+            return GetBraceInCommandElement(TokenKind.RCurly);
+        }
+
+        private IEnumerable<Token> GetBraceInCommandElement(TokenKind tokenKind)
+        {
+            var cmdElemAsts = ast.FindAll(x => x is CommandElementAst && x is ScriptBlockExpressionAst, true);
+            if (cmdElemAsts == null)
+            {
+                yield break;
+            }
+
+            Func<Token, Ast, bool> predicate;
+
+            switch (tokenKind)
+            {
+                case TokenKind.LCurly:
+                    predicate = (x, cmdElemAst) =>
+                        x.Kind == TokenKind.LCurly && x.Extent.StartOffset == cmdElemAst.Extent.StartOffset;
+                    break;
+
+                case TokenKind.RCurly:
+                    predicate = (x, cmdElemAst) =>
+                        x.Kind == TokenKind.RCurly && x.Extent.EndOffset == cmdElemAst.Extent.EndOffset;
+                    break;
+
+                default:
+                    throw new ArgumentException("", nameof(tokenKind));
+            }
+
+            foreach (var cmdElemAst in cmdElemAsts)
+            {
+                var tokenFound = tokens.FirstOrDefault(token => predicate(token, cmdElemAst));
+                if (tokenFound != null)
+                {
+                    yield return tokenFound;
+                }
+            }
+        }
+    }
+}