transpiler, errors

src/foreignthon/transpiler.py

@@ -0,0 +1,83 @@
+from __future__ import annotations
+
+import io
+import tokenize
+from pathlib import Path
+
+from .pack import load_pack
+
+
+def transpile(source: str, lang_code: str) -> str:
+    """
+    Transpile foreign-language Python source to standard Python.
+    Uses the tokenizer so strings and comments are never touched.
+    """
+    pack = load_pack(lang_code)
+
+    # Build a single flat lookup: foreign token -> English token
+    mapping: dict[str, str] = {}
+    mapping.update(pack["keywords"])
+    mapping.update(pack["builtins"])
+    mapping.update(pack["exceptions"])
+    mapping.update(pack["stdlib"])
+
+    tokens_in = tokenize.generate_tokens(io.StringIO(source).readline)
+    result: list[str] = []
+
+    prev_end = (1, 0)
+
+    for tok in tokens_in:
+        tok_type, tok_string, tok_start, tok_end, _ = tok
+
+        # Preserve original whitespace/indentation between tokens
+        start_row, start_col = tok_start
+        end_row, end_col = prev_end
+
+        if start_row == end_row:
+            result.append(" " * (start_col - end_col))
+        else:
+            result.append("\n" * (start_row - end_row))
+            result.append(" " * start_col)
+
+        # Only swap NAME tokens — leaves strings, comments, ops untouched
+        if tok_type == tokenize.NAME and tok_string in mapping:
+            result.append(mapping[tok_string])
+        else:
+            result.append(tok_string)
+
+        prev_end = tok_end
+
+    return "".join(result)
+
+
+def transpile_file(path: Path) -> str:
+    """
+    Detect language from file extension (.es.py → es),
+    read the file, and return transpiled Python source.
+    """
+    lang_code = _detect_lang(path)
+    source = path.read_text(encoding="utf-8")
+
+    # Allow shebang-style override: # foreignthon: fr
+    lang_code = _check_shebang(source, lang_code)
+
+    return transpile(source, lang_code)
+
+
+def _detect_lang(path: Path) -> str:
+    """Extract lang code from extension, e.g. script.es.py → es."""
+    suffixes = path.suffixes  # e.g. ['.es', '.py']
+    if len(suffixes) >= 2 and suffixes[-1] == ".py":
+        return suffixes[-2].lstrip(".")
+    raise ValueError(
+        f"Cannot detect language from filename '{path.name}'. "
+        "Expected format: script.<lang>.py (e.g. script.es.py)"
+    )
+
+
+def _check_shebang(source: str, default: str) -> str:
+    """Check first line for # foreignthon: <lang> override."""
+    first_line = source.splitlines()[0] if source else ""
+    if first_line.startswith("# foreignthon:"):
+        return first_line.split(":", 1)[1].strip()
+    return default