From 60f59e03d421a3f127bf8f19c80fb18d62245571 Mon Sep 17 00:00:00 2001
From: Lars Simon Winzer <lars.winzer@stud.unibas.ch>
Date: Sun, 15 Mar 2026 13:26:59 +0100
Subject: [PATCH] Add: TokenClassifier to perform more extensive syntax
 verification and classify tokens

---
 .../server/tokenizer/TokenClassifier.java     | 103 ++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/tokenizer/TokenClassifier.java

diff --git a/src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/tokenizer/TokenClassifier.java b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/tokenizer/TokenClassifier.java
new file mode 100644
index 0000000..cb19021
--- /dev/null
+++ b/src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/tokenizer/TokenClassifier.java
@@ -0,0 +1,103 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.tokenizer;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class TokenClassifier {
+    public static List<Token> classify(List<RawToken> rawTokens) {
+        validateFirstToken(rawTokens);
+
+        List<Token> tokens = new ArrayList<>();
+
+        for (int i = 0; i < rawTokens.size(); i++) {
+            RawToken raw = rawTokens.get(i);
+
+            switch (raw.type()) {
+                case SEPARATOR -> {
+                    validateSeparator(rawTokens, i);
+                    tokens.add(
+                            new Token(TokenType.SEPARATOR, raw.value(), raw.line(), raw.column()));
+                }
+                case WORD -> {
+                    TokenType type = resolveWordType(rawTokens, i);
+                    tokens.add(new Token(type, raw.value(), raw.line(), raw.column()));
+                }
+                case STRING -> {
+                    validateString(rawTokens, i);
+                    tokens.add(new Token(TokenType.VALUE, raw.value(), raw.line(), raw.column()));
+                }
+
+                case NEWLINE -> {
+                    throw new TokenizerException(
+                            "Unexpected newline in request", raw.line(), raw.column());
+                }
+
+                case EOF -> {
+                    tokens.add(new Token(TokenType.EOF, raw.value(), raw.line(), raw.column()));
+                }
+            }
+        }
+
+        return tokens;
+    }
+
+    private static void validateFirstToken(List<RawToken> rawTokens) {
+        if (rawTokens.isEmpty() || rawTokens.get(0).type() != RawTokenType.WORD) {
+            throw new TokenizerException("Expected COMMAND as first token", 1, 1);
+        }
+    }
+
+    private static void validateSeparator(List<RawToken> rawTokens, int index) {
+        boolean missingKey = index == 0 || rawTokens.get(index - 1).type() != RawTokenType.WORD;
+
+        boolean missingValue =
+                index + 1 >= rawTokens.size()
+                        || (rawTokens.get(index + 1).type() != RawTokenType.WORD
+                                && rawTokens.get(index + 1).type() != RawTokenType.STRING);
+
+        boolean nextWordIsKey =
+                !missingValue
+                        && rawTokens.get(index + 1).type() == RawTokenType.WORD
+                        && index + 2 < rawTokens.size()
+                        && rawTokens.get(index + 2).type() == RawTokenType.SEPARATOR;
+
+        RawToken separator = rawTokens.get(index);
+
+        if (missingKey) {
+            throw new TokenizerException(
+                    "Expected KEY before '='", separator.line(), separator.column());
+        }
+
+        if (missingValue || nextWordIsKey) {
+            throw new TokenizerException(
+                    "Expected VALUE after '='", separator.line(), separator.column());
+        }
+    }
+
+    private static void validateString(List<RawToken> rawTokens, int index) {
+        boolean afterSeparator =
+                index > 0 && rawTokens.get(index - 1).type() == RawTokenType.SEPARATOR;
+
+        if (!afterSeparator) {
+            RawToken token = rawTokens.get(index);
+            throw new TokenizerException("Unexpected string literal", token.line(), token.column());
+        }
+    }
+
+    private static TokenType resolveWordType(List<RawToken> rawTokens, int index) {
+        boolean isFirst = index == 0;
+        boolean afterNewline = index > 0 && rawTokens.get(index - 1).type() == RawTokenType.NEWLINE;
+        boolean afterSeparator =
+                index > 0 && rawTokens.get(index - 1).type() == RawTokenType.SEPARATOR;
+
+        if (isFirst || afterNewline) {
+            return TokenType.COMMAND;
+        }
+
+        if (afterSeparator) {
+            return TokenType.VALUE;
+        }
+
+        return TokenType.KEY;
+    }
+}