diff --git a/.editorconfig b/.editorconfig
index fdfd3d6..22114f7 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -1,6 +1,6 @@
 root = true
 
-[*.{c,txt,js}]
+[*.{cc,txt,js}]
 indent_style = space
 indent_size = 2
 tab_width = 8
diff --git a/src/scanner.c b/src/scanner.c
deleted file mode 100644
index bc971da..0000000
--- a/src/scanner.c
+++ /dev/null
@@ -1,257 +0,0 @@
-#include <tree_sitter/parser.h>
-
-#include <wctype.h>
-#include <string.h>
-#include <stdio.h>
-#include <assert.h>
-
-enum TokenType {
-  QUOTED_TEMPLATE_START,
-  QUOTED_TEMPLATE_END,
-  TEMPLATE_LITERAL_CHUNK,
-  TEMPLATE_INTERPOLATION_START,
-  TEMPLATE_INTERPOLATION_END,
-  HEREDOC_IDENTIFIER,
-};
-
-static void advance(TSLexer *lexer) { lexer->advance(lexer, false); }
-
-static void skip(TSLexer *lexer) { lexer->advance(lexer, true); }
-
-static bool accept_inplace(TSLexer *lexer, enum TokenType token) {
-  lexer->result_symbol = token;
-  return true;
-}
-
-static bool accept_and_advance(TSLexer *lexer, enum TokenType token) {
-  advance(lexer);
-  return accept_inplace(lexer, token);
-}
-
-static bool consume_wxdigit(TSLexer *lexer) {
-  advance(lexer);
-  return iswxdigit(lexer->lookahead);
-}
-
-typedef struct Scanner {
-  bool in_template_interpolation;
-  bool in_quoted_context;
-  int template_interpolation_depth;
-  int quoted_context_depth;
-} Scanner;
-
-void print_debug_info(Scanner *scanner, TSLexer *lexer, const bool *valid_symbols) {
-  printf("\nDEBUG INFO START\n\n");
-  printf("currently at: '%c'\n\n", lexer->lookahead);
-  printf("could be one of\n");
-  printf("quoted_template_start: %x\n", valid_symbols[QUOTED_TEMPLATE_START]);
-  printf("quoted_template_end: %x\n", valid_symbols[QUOTED_TEMPLATE_END]);
-  printf("template_literal_chunk: %x\n", valid_symbols[TEMPLATE_LITERAL_CHUNK]);
-  printf("template_interpolation_start: %x\n", valid_symbols[TEMPLATE_INTERPOLATION_START]);
-  printf("template_interpolation_end: %x\n", valid_symbols[TEMPLATE_INTERPOLATION_END]);
-  printf("\n");
-  printf("scanner state:\n");
-  printf("in_template_interpolation %x\n", scanner->in_template_interpolation);
-  printf("in_quoted_context %x\n", scanner->in_quoted_context);
-  printf("template_interpolation_depth %x\n", scanner->template_interpolation_depth);
-  printf("quoted_context_depth %x\n", scanner->quoted_context_depth);
-  printf("\nDEBUG INFO END\n\n");
-}
-
-void scanner_enter_interpolation_context(Scanner *scanner) {
-  scanner->template_interpolation_depth++;
-  scanner->in_template_interpolation = true;
-  scanner->in_quoted_context = false;
-}
-
-void scanner_exit_interpolation_context(Scanner *scanner) {
-  assert(scanner->template_interpolation_depth > 0);
-  scanner->template_interpolation_depth--;
-  scanner->in_template_interpolation = false;
-  if (scanner->quoted_context_depth > 0) {
-    scanner->in_quoted_context = true;
-  }
-}
-
-void scanner_enter_quoted_context(Scanner *scanner) {
-  scanner->quoted_context_depth++;
-  scanner->in_quoted_context = true;
-  scanner->in_template_interpolation = false;
-}
-
-void scanner_exit_quoted_context(Scanner *scanner) {
-  assert(scanner->quoted_context_depth > 0);
-  scanner->quoted_context_depth--;
-  scanner->in_quoted_context = false;
-  if (scanner->template_interpolation_depth > 0) {
-    scanner->in_template_interpolation = true;
-  }
-}
-
-bool scanner_scan(Scanner *scanner, TSLexer *lexer, const bool *valid_symbols) {
-  // print_debug_info(scanner, lexer, valid_symbols);
-
-  while (iswspace(lexer->lookahead)) {
-    skip(lexer);
-  }
-  if (lexer->lookahead == '\0') return false;
-
-  // manage quoted context
-  if (
-    valid_symbols[QUOTED_TEMPLATE_START] &&
-    !scanner->in_quoted_context &&
-    lexer->lookahead == '"'
-  ) {
-    scanner_enter_quoted_context(scanner);
-    return accept_and_advance(lexer, QUOTED_TEMPLATE_START);
-  }
-  if (
-    valid_symbols[QUOTED_TEMPLATE_END] &&
-    scanner->in_quoted_context &&
-    lexer->lookahead == '"'
-  ) {
-    scanner_exit_quoted_context(scanner);
-    return accept_and_advance(lexer, QUOTED_TEMPLATE_END);
-  }
-
-  // manage template interpolations
-  if (
-    valid_symbols[TEMPLATE_INTERPOLATION_START] &&
-    lexer->lookahead == '$'
-  ) {
-    advance(lexer);
-    if (lexer->lookahead == '{') {
-      scanner_enter_interpolation_context(scanner);
-      return accept_and_advance(lexer, TEMPLATE_INTERPOLATION_START);
-    }
-    if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) {
-      // try to scan escape sequence
-      if (lexer->lookahead == '$') {
-        advance(lexer);
-        if (lexer->lookahead == '{') {
-          // $${
-          return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-        }
-      }
-      return accept_inplace(lexer, TEMPLATE_LITERAL_CHUNK);
-    }
-  }
-  if (
-    valid_symbols[TEMPLATE_INTERPOLATION_END] &&
-    lexer->lookahead == '}' &&
-    scanner->in_template_interpolation
-  ) {
-    scanner_exit_interpolation_context(scanner);
-    return accept_and_advance(lexer, TEMPLATE_INTERPOLATION_END);
-  }
-
-  // handle template literal chunks
-
-  // handle template literal chunks in quoted contexts
-  //
-  // they may not contain newlines and may contain escape sequences
-
-  if (valid_symbols[TEMPLATE_LITERAL_CHUNK] && scanner->in_quoted_context) {
-    switch (lexer->lookahead) {
-      case '\\':
-        advance(lexer);
-        switch (lexer->lookahead) {
-          case '"':
-          case 'n':
-          case 'r':
-          case 't':
-          case '\\':
-            return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-          case 'u':
-            for (int i = 0; i < 4; i++) {
-              if (!consume_wxdigit(lexer)) return false;
-            }
-            return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-          case 'U':
-            for (int i = 0; i < 8; i++) {
-              if (!consume_wxdigit(lexer)) return false;
-            }
-            return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-          default:
-            return false;
-        }
-    }
-  }
-
-  // handle escaped template interpolations in string literals
-  if (
-    valid_symbols[TEMPLATE_LITERAL_CHUNK] &&
-    !valid_symbols[TEMPLATE_INTERPOLATION_START] &&
-    scanner->in_quoted_context
-  ) {
-    // try to scan escaped template interpolation
-    switch (lexer->lookahead) {
-      case '$':
-        advance(lexer);
-        if (lexer->lookahead == '{') {
-          // unescaped template interpolation
-          return false;
-        }
-        if (lexer->lookahead == '$') {
-          advance(lexer);
-          if (lexer->lookahead == '{') {
-            // $${
-            return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-          }
-        return accept_inplace(lexer, TEMPLATE_LITERAL_CHUNK);
-        }
-    }
-  }
-
-  // handle heredoc identifier
-  if (valid_symbols[HEREDOC_IDENTIFIER]) {
-    if (lexer->lookahead != 'E') {
-       if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-    }
-    advance(lexer);
-    if (lexer->lookahead != 'O') {
-       if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-    }
-    advance(lexer);
-    if (lexer->lookahead != 'F') {
-       if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-    }
-    return accept_and_advance(lexer, HEREDOC_IDENTIFIER);
-  }
-
-  // handle all other quoted template or string literal characters
-  if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) {
-    return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
-  }
-
-  // probably not handled by the external scanner
-  return false;
-}
-
-void *tree_sitter_hcl_external_scanner_create() {
-  Scanner *scanner = (Scanner*)malloc(sizeof(Scanner));
-  if (scanner) {
-    scanner->in_template_interpolation = false;
-    scanner->in_quoted_context = false;
-    scanner->template_interpolation_depth = 0;
-    scanner->quoted_context_depth = 0;
-  }
-  return scanner;
-}
-
-void tree_sitter_hcl_external_scanner_destroy(void *p) {
-  free(p);
-}
-
-unsigned tree_sitter_hcl_external_scanner_serialize(void *p, char *b) {
-  memcpy(b, p, sizeof(Scanner)); return sizeof(Scanner);
-}
-
-void tree_sitter_hcl_external_scanner_deserialize(void *p, const char *b, unsigned n) {
-  memcpy(p, b, n);
-}
-
-bool tree_sitter_hcl_external_scanner_scan(void *p, TSLexer *lexer, const bool *valid_symbols) {
-  return scanner_scan((Scanner*)p, lexer, valid_symbols);
-}
-
diff --git a/src/scanner.cc b/src/scanner.cc
new file mode 100644
index 0000000..52ba60a
--- /dev/null
+++ b/src/scanner.cc
@@ -0,0 +1,255 @@
+#include <tree_sitter/parser.h>
+
+#include <vector>
+#include <string>
+#include <wctype.h>
+#include <assert.h>
+#include <stdio.h>
+
+namespace {
+
+using std::vector;
+using std::string;
+
+enum TokenType {
+  QUOTED_TEMPLATE_START,
+  QUOTED_TEMPLATE_END,
+  TEMPLATE_LITERAL_CHUNK,
+  TEMPLATE_INTERPOLATION_START,
+  TEMPLATE_INTERPOLATION_END,
+  HEREDOC_IDENTIFIER,
+};
+
+enum ContextType {
+  TEMPLATE_INTERPOLATION,
+  QUOTED_TEMPLATE,
+  HEREDOC_TEMPLATE,
+};
+
+struct Context {
+  ContextType type;
+
+  // valid if type == HEREDOC_TEMPLATE
+  char* identifier;
+  size_t identifier_size;
+};
+
+struct Scanner {
+
+public:
+  // TODO: implement properly
+  unsigned serialize(char* buf) {
+    return 0;
+  }
+
+  // TODO: implement properly
+  void deserialize(const char* buf, unsigned n) {
+  }
+
+  bool scan(TSLexer* lexer, const bool* valid_symbols) {
+    while (iswspace(lexer->lookahead)) {
+      skip(lexer);
+    }
+    if (lexer->lookahead == '\0') {
+      return false;
+    }
+    // manage quoted context
+    if (valid_symbols[QUOTED_TEMPLATE_START] && !in_quoted_context() && lexer->lookahead == '"') {
+      context_stack.push_back({ .type = QUOTED_TEMPLATE });
+      return accept_and_advance(lexer, QUOTED_TEMPLATE_START);
+    }
+    if (valid_symbols[QUOTED_TEMPLATE_END] && in_quoted_context() && lexer->lookahead == '"') {
+      context_stack.pop_back();
+      return accept_and_advance(lexer, QUOTED_TEMPLATE_END);
+    }
+
+    // manage template interpolations
+    if (valid_symbols[TEMPLATE_INTERPOLATION_START] && !in_interpolation_context() && lexer->lookahead == '$') {
+      advance(lexer);
+      if (lexer->lookahead == '{') {
+        context_stack.push_back({ .type = TEMPLATE_INTERPOLATION});
+        return accept_and_advance(lexer, TEMPLATE_INTERPOLATION_START);
+      }
+      if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) {
+        // try to scan escape sequence
+        if (lexer->lookahead == '$') {
+          advance(lexer);
+          if (lexer->lookahead == '{') {
+            // $${
+            return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+          }
+        }
+        return accept_inplace(lexer, TEMPLATE_LITERAL_CHUNK);
+      }
+    }
+    if (valid_symbols[TEMPLATE_INTERPOLATION_END] && in_interpolation_context() && lexer->lookahead == '}') {
+      context_stack.pop_back();
+      return accept_and_advance(lexer, TEMPLATE_INTERPOLATION_END);
+    }
+
+    // handle template literal chunks
+
+    // handle template literal chunks in quoted contexts
+    //
+    // they may not contain newlines and may contain escape sequences
+
+    if (valid_symbols[TEMPLATE_LITERAL_CHUNK] && in_quoted_context()) {
+      switch (lexer->lookahead) {
+        case '\\':
+          advance(lexer);
+          switch (lexer->lookahead) {
+            case '"':
+            case 'n':
+            case 'r':
+            case 't':
+            case '\\':
+              return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+            case 'u':
+              for (int i = 0; i < 4; i++) {
+                if (!consume_wxdigit(lexer)) return false;
+              }
+              return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+            case 'U':
+              for (int i = 0; i < 8; i++) {
+                if (!consume_wxdigit(lexer)) return false;
+              }
+              return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+            default:
+              return false;
+          }
+      }
+    }
+
+    // handle escaped template interpolations in string literals
+    if (valid_symbols[TEMPLATE_LITERAL_CHUNK] && !valid_symbols[TEMPLATE_INTERPOLATION_START] && in_quoted_context()) {
+      // try to scan escaped template interpolation
+      switch (lexer->lookahead) {
+        case '$':
+          advance(lexer);
+          if (lexer->lookahead == '{') {
+            // unescaped template interpolation
+            return false;
+          }
+          if (lexer->lookahead == '$') {
+            advance(lexer);
+            if (lexer->lookahead == '{') {
+              // $${
+              return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+            }
+          return accept_inplace(lexer, TEMPLATE_LITERAL_CHUNK);
+          }
+      }
+    }
+
+    // handle heredoc identifier
+    if (valid_symbols[HEREDOC_IDENTIFIER]) {
+      if (lexer->lookahead != 'E') {
+        if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) {
+          return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+        } else {
+          return false;
+        }
+      }
+      advance(lexer);
+      if (lexer->lookahead != 'O') {
+        if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) {
+          return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+        } else {
+          return false;
+        }
+      }
+      advance(lexer);
+      if (lexer->lookahead != 'F') {
+        if (valid_symbols[TEMPLATE_LITERAL_CHUNK]) {
+          return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+        } else {
+          return false;
+        }
+      }
+      return accept_and_advance(lexer, HEREDOC_IDENTIFIER);
+    }
+
+    // handle all other quoted template or string literal characters
+    if (valid_symbols[TEMPLATE_LITERAL_CHUNK] && in_template_context()) {
+      return accept_and_advance(lexer, TEMPLATE_LITERAL_CHUNK);
+    }
+
+    // probably not handled by the external scanner
+    return false;
+  }
+
+private:
+  vector<Context> context_stack;
+  vector<string> heredoc_identifier_stack;
+
+  void advance(TSLexer* lexer) {
+    lexer->advance(lexer, false);
+  }
+
+  void skip(TSLexer* lexer) { lexer->advance(lexer, true); }
+
+  bool accept_inplace(TSLexer* lexer, TokenType token) {
+    lexer->result_symbol = token;
+    return true;
+  }
+
+  bool accept_and_advance(TSLexer* lexer, TokenType token) {
+    advance(lexer);
+    return accept_inplace(lexer, token);
+  }
+  bool consume_wxdigit(TSLexer* lexer) {
+    advance(lexer);
+    return iswxdigit(lexer->lookahead);
+  }
+
+  bool in_context_type(ContextType type) {
+    if (context_stack.empty()) {
+      return false;
+    }
+    return context_stack.back().type == type;
+  }
+
+  bool in_quoted_context() {
+    return in_context_type(QUOTED_TEMPLATE);
+  }
+
+  bool in_template_context() {
+    return in_context_type(QUOTED_TEMPLATE) || in_context_type(HEREDOC_TEMPLATE);
+  }
+
+  bool in_interpolation_context() {
+    return in_context_type(TEMPLATE_INTERPOLATION);
+  }
+
+};
+
+} // namespace
+
+extern "C" {
+
+// tree sitter callbacks
+void* tree_sitter_hcl_external_scanner_create() {
+  return new Scanner();
+}
+
+void tree_sitter_hcl_external_scanner_destroy(void* p) {
+  Scanner* scanner = static_cast<Scanner*>(p);
+  delete scanner;
+}
+
+unsigned tree_sitter_hcl_external_scanner_serialize(void* p, char* b) {
+  Scanner* scanner = static_cast<Scanner*>(p);
+  return scanner->serialize(b);
+}
+
+void tree_sitter_hcl_external_scanner_deserialize(void* p, const char* b, unsigned n) {
+  Scanner* scanner = static_cast<Scanner*>(p);
+  return scanner->deserialize(b, n);
+}
+
+bool tree_sitter_hcl_external_scanner_scan(void* p, TSLexer* lexer, const bool* valid_symbols) {
+  Scanner* scanner = static_cast<Scanner*>(p);
+  return scanner->scan(lexer, valid_symbols);
+}
+
+} // extern "C"
diff --git a/test/corpus/collections.txt b/test/corpus/collections.txt
index 9cce689..aa810e5 100644
--- a/test/corpus/collections.txt
+++ b/test/corpus/collections.txt
@@ -1,5 +1,5 @@
 ================================================================================
-tuple
+simple tuple
 ================================================================================
 
 foo = [1, 2, "foo"]