From 5082bc64818d9580c92e04dea8ddf3455b5d4b5f Mon Sep 17 00:00:00 2001
From: Brychan Dempsey <brychand@hotmail.com>
Date: Fri, 12 Mar 2021 12:14:51 +1300
Subject: [PATCH] fixed word parsing

---
 Assignment 1/Program.cs | 67 ++++++++++++++++++++++++++++-------------
 1 file changed, 46 insertions(+), 21 deletions(-)

diff --git a/Assignment 1/Program.cs b/Assignment 1/Program.cs
index 95902da..aa6e0af 100644
--- a/Assignment 1/Program.cs	
+++ b/Assignment 1/Program.cs	
@@ -71,7 +71,8 @@ namespace Assignment_1
                 printwords,
                 printwordcount,
                 set,
-                reverse
+                reverse,
+                h
             }
             public void StartParsing(Stream source, bool dynamicInput = false)
             {
@@ -125,6 +126,13 @@ namespace Assignment_1
                                 case statements.reverse:
                                     Reverse(source);
                                     break;
+                                case statements.h:
+                                    Console.WriteLine("Commands are: ");
+                                    foreach (var item in Enum.GetValues(typeof(statements)))
+                                    {
+                                        Console.WriteLine("\t{0}", ((statements)item).ToString());
+                                    }
+                                    break;
                             }
                         }
                         else Console.WriteLine("Failed parsing statement");
@@ -143,10 +151,9 @@ namespace Assignment_1
             /// <returns></returns>
             bool Append(Stream source, long lineStart = -1)
             {
-                // If it wasn't explicitly set, assume line starts the length of 'append ' before the current position
                 if (lineStart == -1)
                 {
-                    lineStart = source.Position - "append ".Length;
+                    lineStart = GetLineStart(source, "append");
                 }
                 string key;
                 long keyEndPos = FindIdentifier(source, out key);
@@ -256,18 +263,13 @@ namespace Assignment_1
             {
                 if(lineStart == -1)
                 {
-                    lineStart = source.Position - "set ".Length;
+                    lineStart = GetLineStart(source, "set");
                 }
                 string identifier;
                 long identifierEndPos = FindIdentifier(source, out identifier);
-                if (identifierEndPos < 0 || identifierEndPos == source.Position)
+                if (identifierEndPos <= source.Position + 1 )
                 {
-                    string fullLine = GetNextLine(source); // Grab a copy of the line to show the user
-                    //                 set x
-                    string errorMSG = "    ^ could not identify object";
-                    Console.WriteLine(fullLine);
-                    Console.WriteLine(errorMSG);
-                    source.SetLength(source.Position);
+                    WriteDebugLine(lineStart, "set ".Length, "???", source);
                     return false;
                 }
                 source.Position = identifierEndPos;
@@ -275,6 +277,7 @@ namespace Assignment_1
                 long expressionEndPos = FindExpression(source, out expression);
                 if (expressionEndPos < 0)
                 {
+                    WriteDebugLine(lineStart, identifierEndPos, "failed parsing expression", source);
                     // Couldn't match expression
                     return false;
                 }
@@ -282,8 +285,7 @@ namespace Assignment_1
                 {
                     if (Symbols[identifier].Item2.HasFlag(VariableFlags.Reserved))
                     {
-                        Console.WriteLine("Error: Cannot assign to {0} as it is a reserved constant.", identifier);
-                        source.SetLength(source.Position); // Wipe the remainder of the stream, so that it doesn't get read
+                        WriteDebugLine(lineStart, identifierEndPos - identifier.Length, "cannot assign to a reserved constant", source);
                         return false;
                     }
                     Symbols[identifier] = new Tuple<string, VariableFlags>(expression, Symbols[identifier].Item2);
@@ -331,11 +333,29 @@ namespace Assignment_1
             {
                 source.Position = lineStart;
                 string fullLine = GetNextLine(source);
-                string errorMSG = new string (' ', (int)(caratPos - lineStart)) +  "^ " + errorMessage;
+                string errorMSG = new string (' ', (caratPos - lineStart) >= 0 ? (int)(caratPos - lineStart):0) +  "^ " + errorMessage;
                 Console.WriteLine(fullLine);
                 Console.WriteLine(errorMSG);
                 source.SetLength(source.Position);
             }
+            /// <summary>
+            /// Gets the starting point of the expression at expected line.
+            /// </summary>
+            /// <param name="source"></param>
+            /// <param name="word"></param>
+            /// <returns></returns>
+            long GetLineStart(Stream source, string word)
+            {
+                // Decrement and check the previous value is 32 (space), before incrementing back to our current pos
+                // Don't need to guard against oob - implied it's within bounds by the set command being at least 3 bytes long
+                source.Position--;
+                if (source.ReadByte() == 32)
+                {
+                    source.Position--;
+                }
+                //source.Position++;
+                return source.Position - word.Length;
+            }
 
             #endregion
             #region Data Handling
@@ -507,7 +527,18 @@ namespace Assignment_1
         /// <returns></returns>
         static long FindNextWord(Stream s, out string nextWord)
         {
-            return FindNextOccurance(s, (c, s) => Char.IsWhiteSpace(c), out nextWord);
+            // Find the next occurance of a whitespace character
+            long originalPos = s.Position;
+            string tempstring;
+            long nextWSOccurance = FindNextOccurance(s, (c, s) => Char.IsWhiteSpace(c), out tempstring);
+            while (tempstring.Length == 0)
+            {
+                nextWSOccurance = FindNextOccurance(s, (c, s) => Char.IsWhiteSpace(c), out tempstring);
+                s.Position++;
+            }
+            nextWord = tempstring;
+            s.Position = originalPos;
+            return nextWSOccurance;
         }
 
 
@@ -532,12 +563,6 @@ namespace Assignment_1
                 }
                 else if (p(nextChar, s))
                 {
-                   /*if (c == '\n')
-                    {
-                        s.Position--;
-                        if (s.ReadByte() != '\r') s.Position--;
-                        // Avoid capturing the carriage return
-                    }*/
                     charFound = true;
                 }
                 else