From 2546b2bb48f45a819ffbfec92bf4ae111854678b Mon Sep 17 00:00:00 2001
From: Mitchell Paulus <paulusm14@gmail.com>
Date: Wed, 18 Sep 2024 21:53:38 -0500
Subject: [PATCH] Add first translation of Evaluator

---
 mshell-go/Evaluator.go    | 119 ++++++++++++++++++++++++++++++++++++++
 mshell-go/Lexer.go        |   6 +-
 mshell-go/MShellObject.go |   1 -
 mshell-go/Main.go         |   2 +-
 4 files changed, 123 insertions(+), 5 deletions(-)
 create mode 100644 mshell-go/Evaluator.go

diff --git a/mshell-go/Evaluator.go b/mshell-go/Evaluator.go
new file mode 100644
index 0000000..6305c9e
--- /dev/null
+++ b/mshell-go/Evaluator.go
@@ -0,0 +1,119 @@
+package main
+
+import (
+    "io"
+    "fmt"
+    "os"
+)
+
+type MShellStack []MShellObject
+
+func (objList MShellStack) Peek() (MShellObject, error) {
+    if len(objList) == 0 {
+        return nil, fmt.Errorf("Empty stack")
+    }
+    return objList[len(objList) - 1], nil
+}
+
+func (objList MShellStack) Pop() (MShellObject, error) {
+    if len(objList) == 0 {
+        return nil, fmt.Errorf("Empty stack")
+    }
+    popped := objList[len(objList) - 1]
+    objList = objList[:len(objList) - 1]
+    return popped, nil
+}
+
+func (objList MShellStack) Push(obj MShellObject) {
+    objList = append(objList, obj)
+}
+
+type EvalState  struct {
+    PositionalArgs[] string
+    LoopDepth int32
+
+    // private Dictionary<string, MShellObject> _variables = new();
+    Variables map[string]MShellObject
+}
+
+type EvalResult struct {
+    Success bool
+    BreakNum int32
+}
+
+type ExecuteContext struct {
+    StandardInput io.Reader
+    StandardOutput io.Writer
+}
+
+func SimpleSuccess() EvalResult {
+    return EvalResult { true, -1 }
+}
+
+func FailWithMessage(message string) EvalResult {
+    // Log message to stderr
+    fmt.Fprintf(os.Stderr, message)
+    return EvalResult { false, -1 }
+}
+
+func (state EvalState) Evaluate(tokens []Token, stack MShellStack, context ExecuteContext) EvalResult { 
+    index := 0
+
+    // Need a stack of integers
+    // quotationStack := []int32{}
+    leftSquareBracketStack := []int{}
+
+    for index < len(tokens) {
+        t := tokens[index]
+        index++
+
+        if t.Type == EOF {
+            return SimpleSuccess()
+        } else if t.Type == LITERAL {
+            stack.Push(&MShellLiteral { t.Lexeme })
+        } else if t.Type == LEFT_SQUARE_BRACKET {
+            leftSquareBracketStack = append(leftSquareBracketStack, index)
+
+            for {
+                currentToken := tokens[index]
+                index++
+
+                if index >= len(tokens) || tokens[index].Type == EOF {
+                    return FailWithMessage(fmt.Sprintf("%d:%d: Found unbalanced bracket.\n", currentToken.Line, currentToken.Column))
+                }
+
+                if tokens[index].Type == LEFT_SQUARE_BRACKET {
+                    leftSquareBracketStack = append(leftSquareBracketStack, index)
+                } else if tokens[index].Type == RIGHT_SQUARE_BRACKET {
+                    if len(leftSquareBracketStack) > 0 {
+                        leftIndex := leftSquareBracketStack[len(leftSquareBracketStack)-1]
+
+                        if len(leftSquareBracketStack) == 0 {
+                            listStack := []MShellObject{}
+                            tokensWithinList := tokens[leftIndex + 1:index - leftIndex - 1]
+                            result := state.Evaluate(tokensWithinList, listStack, context)
+                            if !result.Success {
+                                return result
+                            }
+
+                            if result.BreakNum > 0 {
+                                return FailWithMessage("Encountered break within list.\n")
+                            }
+
+                            l := &MShellList { listStack, nil, nil }
+                            stack.Push(l)
+                            break
+                        }
+
+                    } else {
+                        return FailWithMessage(fmt.Sprintf("%d:%d: Found unbalanced square bracket.\n", currentToken.Line, currentToken.Column))
+                    }
+                } 
+            }
+        } else {
+            return FailWithMessage(fmt.Sprintf("%d:%d: We haven't implemented the token type '%s' yet.\n", t.Line, t.Column, t.Type))
+        }
+    }
+
+    return EvalResult { true, -1 }
+}
diff --git a/mshell-go/Lexer.go b/mshell-go/Lexer.go
index 89f8c66..44bc7e9 100644
--- a/mshell-go/Lexer.go
+++ b/mshell-go/Lexer.go
@@ -127,7 +127,7 @@ type Token struct {
     Column    int
     Start     int
     Lexeme    string
-    TokenType TokenType
+    Type TokenType
 }
 
 type Lexer struct {
@@ -156,7 +156,7 @@ func (l *Lexer) makeToken(tokenType TokenType) Token {
         Column:    l.col,
         Start:     l.start,
         Lexeme:    lexeme,
-        TokenType: tokenType,
+        Type: tokenType,
     }
 }
 
@@ -333,7 +333,7 @@ func (l *Lexer) Tokenize() []Token {
     for {
         t := l.scanToken()
         tokens = append(tokens, t)
-        if t.TokenType == ERROR || t.TokenType == EOF {
+        if t.Type == ERROR || t.Type == EOF {
             break
         }
     }
diff --git a/mshell-go/MShellObject.go b/mshell-go/MShellObject.go
index 7fc045f..a879b84 100644
--- a/mshell-go/MShellObject.go
+++ b/mshell-go/MShellObject.go
@@ -236,4 +236,3 @@ func (obj *MShellPipe) DebugString() string {
     // Join each item with a ' | '
     return strings.Join(DebugStrs(obj.List.Items), " | ")
 }
-
diff --git a/mshell-go/Main.go b/mshell-go/Main.go
index e2ad1fe..7e1d1c0 100644
--- a/mshell-go/Main.go
+++ b/mshell-go/Main.go
@@ -60,7 +60,7 @@ func main() {
         fmt.Println("Tokens:")
         for _, t := range tokens {
             //                 Console.Write($"{t.Line}:{t.Column}:{t.TokenType} {t.RawText}\n");
-            fmt.Printf("%d:%d:%s %s\n", t.Line, t.Column, t.TokenType, t.Lexeme)
+            fmt.Printf("%d:%d:%s %s\n", t.Line, t.Column, t.Type, t.Lexeme)
         }
         return
     }