1 files changed, 92 insertions, 0 deletions
diff --git a/src/mml_composemusic_mcp/parser_base.py b/src/mml_composemusic_mcp/parser_base.py
new file mode 100644
index 0000000..0427a4c
--- /dev/null
+++ b/src/mml_composemusic_mcp/parser_base.py
@@ -0,0 +1,92 @@
+"""Base parser utilities shared between ppmck and pyxel parsers."""
+
+from dataclasses import dataclass
+
+from .ir import ErrorCode, ErrorDetail
+from .lexer import Token, TokenType
+
+
+@dataclass
+class ParserContext:
+    tokens: list[Token]
+    pos: int = 0
+    errors: list[ErrorDetail] = None  # type: ignore[assignment]
+
+    def __post_init__(self) -> None:
+        if self.errors is None:
+            self.errors = []
+
+    def peek(self, offset: int = 0) -> Token:
+        idx = self.pos + offset
+        if idx >= len(self.tokens):
+            return self.tokens[-1]
+        return self.tokens[idx]
+
+    def advance(self) -> Token:
+        token = self.peek()
+        self.pos += 1
+        return token
+
+    def match(self, *types: TokenType) -> Token | None:
+        token = self.peek()
+        if token.type in types:
+            return self.advance()
+        return None
+
+    def expect(self, *types: TokenType) -> Token | None:
+        return self.match(*types)
+
+    def add_error(
+        self,
+        code: ErrorCode,
+        line: int,
+        column: int,
+        message: str,
+        severity: str,
+        hint: str = "",
+        context: str = "",
+    ) -> None:
+        self.errors.append(
+            ErrorDetail(
+                code=code,
+                line=line,
+                column=column,
+                message=message,
+                severity=severity,
+                hint=hint,
+                context=context,
+            )
+        )
+
+
+class ParserError(Exception):
+    pass
+
+
+def length_value_to_ticks(length: int, dots: int, ticks_per_quarter: int = 192) -> int:
+    base = ticks_per_quarter * 4 // length
+    total = base
+    add = base
+    for _ in range(dots):
+        add //= 2
+        total += add
+    return total
+
+
+NOTE_OFFSET = {
+    "c": 0,
+    "d": 2,
+    "e": 4,
+    "f": 5,
+    "g": 7,
+    "a": 9,
+    "b": 11,
+}
+
+
+def note_to_midi(note: str, octave: int, accidental: int = 0) -> int:
+    return (octave + 1) * 12 + NOTE_OFFSET[note] + accidental
+
+
+def clamp(value: int, min_val: int, max_val: int) -> int:
+    return max(min_val, min(value, max_val))