From ffd66f1f866354bb79a137f55bca5aa970394d23 Mon Sep 17 00:00:00 2001
From: erick-alcachofa <erick@artichoke.dev>
Date: Sun, 5 Oct 2025 22:51:16 -0600
Subject: [PATCH] feat: Added peekExpect method for token type validation in
 tokenizer Signed-off-by: erick-alcachofa <erick@artichoke.dev>

Introduced `peekExpect(std::size_t, TokenV)` to the Tokenizer class, enabling
token lookahead with explicit token type checks. This method returns an
`Unexpected` error with diagnostic info if the expected token type does not
match the peeked token.

Includes a special case handling (workaround) for distinguishing between
`>` and `>>` tokens when parsing the token stream.
---
 lib/include/artichoke/Tokenizer/Tokenizer.hpp |  1 +
 lib/src/Tokenizer/Tokenizer.cpp               | 56 +++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/lib/include/artichoke/Tokenizer/Tokenizer.hpp b/lib/include/artichoke/Tokenizer/Tokenizer.hpp
index 7269d57..33c5485 100644
--- a/lib/include/artichoke/Tokenizer/Tokenizer.hpp
+++ b/lib/include/artichoke/Tokenizer/Tokenizer.hpp
@@ -25,6 +25,7 @@ namespace arti::lang {
 
     Expected<void> consume(std::size_t n = 1) noexcept;
     Expected<Token> peek(std::size_t n = 0) noexcept;
+    Expected<Token> peekExpect(std::size_t n, TokenV tokenType) noexcept;
 
     bool finished() const noexcept;
 
diff --git a/lib/src/Tokenizer/Tokenizer.cpp b/lib/src/Tokenizer/Tokenizer.cpp
index f95b457..4cc905e 100644
--- a/lib/src/Tokenizer/Tokenizer.cpp
+++ b/lib/src/Tokenizer/Tokenizer.cpp
@@ -106,6 +106,62 @@ namespace arti::lang {
     return tokensBuffer.at(n);
   }
 
+  Expected<Token>
+  Tokenizer::peekExpect(std::size_t n, TokenV tokenType) noexcept {
+    if (tokensBuffer.size() > (n + 1)) {
+      auto tokenAt = tokensBuffer.at(n);
+
+      if (tokenAt.value != tokenType) {
+        return Unexpected<> {
+          Exception{
+            .line = tokenAt.line,
+            .column = tokenAt.column,
+            .message = std::format(
+              "OExpected token of type {}, got {}",
+              toString(tokenType), toString(tokenAt)
+            )
+          }
+        };
+      }
+
+      return tokenAt;
+    }
+
+    auto token = peek(n);
+
+    if (!token) {
+      return token;
+    }
+
+    /* TODO: Look for a nicer fix for this corner case */
+    if (tokenType == TokenV::opGt && token->value == TokenV::opRShift) {
+      token->strValue.remove_suffix(1);
+      token->value = TokenV::opGt;
+      auto peekTok = *token;
+      tokensBuffer.pop_back();
+      tokensBuffer.push_back(*token);
+      token->column += 1;
+      token->strValue = std::string_view{token->strValue.begin() + 1, 1};
+      tokensBuffer.push_back(*token);
+      token = peekTok;
+    }
+
+    if (token->value != tokenType) {
+      return Unexpected<> {
+        Exception{
+          .line = token->line,
+          .column = token->column,
+          .message = std::format(
+            "OExpected token of type {}, got {}",
+            toString(tokenType), toString(*token)
+          )
+        }
+      };
+    }
+
+    return *token;
+  }
+
   bool Tokenizer::finished() const noexcept {
     if (tokensGenerator.finished()) {
       if (!tokensBuffer.empty()) {