added decompilation and decompile with portffix in json

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "foreignthon"
-version = "0.3.0"
+version = "0.4.0"
 description = "Write Python in any language. Transpiles foreign-language .xx.py files to standard Python."
 license = { text = "GPL v3" }
 requires-python = ">=3.9"

src/foreignthon/cli.py

@@ -115,8 +115,48 @@ def validate_pack(json_file: Path):
     click.echo(f"✓ Pack '{data['meta']['name']}' is valid.")
 
 
+
+@main.command(context_settings=CONTEXT_SETTINGS)
+@click.argument("file", type=click.Path(exists=True, path_type=Path))
+@click.option("--lang", "-l", required=True, help="Target language code (e.g. es, ta)")
+@click.option("--postfix", is_flag=True, help="Use @@ postfix style for if/elif/while")
+@click.option("--output", "-o", default=None, help="Output file or directory")
+def decompile(file: Path, lang: str, postfix: bool, output: str | None):
+    """
+    Convert standard Python back to a foreign language.
+
+    Keywords and builtins are translated. Variable names are untouched.
+
+    \b
+    fpy decompile script.py --lang es
+    fpy decompile script.py --lang ta --postfix
+    fpy decompile script.py --lang es -o out/
+    """
+    from .transpiler import detranspile_file
+
+    result = detranspile_file(file, lang, postfix=postfix)
+
+    ext = f".{lang}.py"
+
+    if output is None:
+        stem = file.stem if not file.stem.endswith(f".{lang}") else file.stem
+        out_path = file.with_name(stem + ext)
+    else:
+        out = Path(output)
+        if out.is_dir() or str(output).endswith("/"):
+            out.mkdir(parents=True, exist_ok=True)
+            out_path = out / (file.stem + ext)
+        else:
+            out_path = out
+
+    out_path.parent.mkdir(parents=True, exist_ok=True)
+    out_path.write_text(result, encoding="utf-8")
+    click.echo(f"Decompiled: {out_path}")
+
+
 def _lang_from_file(path: Path) -> str:
     suffixes = path.suffixes
     if len(suffixes) >= 2 and suffixes[-1] == ".py":
         return suffixes[-2].lstrip(".")
     return "en"
+

src/foreignthon/transpiler.py

@@ -9,11 +9,6 @@ from .pack import load_pack
 
 
 def _apply_postfix_syntax(source: str, mapping: dict) -> str:
-    """
-    Pre-tokenizer pass: handle postfix @@ keyword syntax.
-    x > 0 @@ஆனால்:  →  ஆனால் x > 0:
-    Indentation is preserved by separating it before rewriting.
-    """
     if "@@" not in source:
         return source
 
@@ -28,28 +23,50 @@ def _apply_postfix_syntax(source: str, mapping: dict) -> str:
             result.append(line)
             continue
 
-        # Separate indentation from content so we never lose it
         stripped = line.lstrip()
         indent = line[: len(line) - len(stripped)]
         ending = "\n" if stripped.endswith("\n") else ""
         content = stripped.rstrip("\n")
 
         def _replace(m: re.Match) -> str:
-            expr = m.group(1).strip()
-            kw = m.group(2)
-            return f"{kw} {expr}"
+            return f"{m.group(2)} {m.group(1).strip()}"
 
-        rewritten = indent + postfix_re.sub(_replace, content) + ending
-        result.append(rewritten)
+        result.append(indent + postfix_re.sub(_replace, content) + ending)
+
+    return "".join(result)
+
+
+def _apply_postfix_output(source: str, en_to_foreign: dict, postfix_english: set) -> str:
+    """
+    Post-pass for decompile: rewrite foreign keyword lines to @@ postfix.
+    postfix_english comes from the language pack's postfix_keywords list.
+    """
+    postfix_foreign = {en_to_foreign[k] for k in postfix_english if k in en_to_foreign}
+
+    lines = source.splitlines(keepends=True)
+    result = []
+
+    for line in lines:
+        stripped = line.lstrip()
+        indent = line[: len(line) - len(stripped)]
+        ending = "\n" if line.endswith("\n") else ""
+        content = stripped.rstrip("\n")
+        matched = False
+
+        for fkw in postfix_foreign:
+            if content.startswith(fkw + " ") and content.endswith(":"):
+                expr = content[len(fkw): -1].strip()
+                result.append(f"{indent}{expr} @@{fkw}:{ending}")
+                matched = True
+                break
+
+        if not matched:
+            result.append(line)
 
     return "".join(result)
 
 
 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)
 
     mapping: dict[str, str] = {}
@@ -86,6 +103,47 @@ def transpile(source: str, lang_code: str) -> str:
     return "".join(result)
 
 
+def detranspile(source: str, lang_code: str, postfix: bool = False) -> str:
+    pack = load_pack(lang_code)
+
+    en_to_foreign: dict[str, str] = {}
+    for section in ("keywords", "builtins", "exceptions", "stdlib"):
+        for foreign, english in pack[section].items():
+            en_to_foreign[english] = foreign
+
+    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
+
+        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)
+
+        if tok_type == tokenize.NAME and tok_string in en_to_foreign:
+            result.append(en_to_foreign[tok_string])
+        else:
+            result.append(tok_string)
+
+        prev_end = tok_end
+
+    output = "".join(result)
+
+    if postfix:
+        # Use pack-defined list, fallback to sensible defaults
+        postfix_english = set(pack.get("postfix_keywords", ["if", "elif", "while"]))
+        output = _apply_postfix_output(output, en_to_foreign, postfix_english)
+
+    return output
+
+
 def transpile_file(path: Path) -> str:
     lang_code = _detect_lang(path)
     source = path.read_text(encoding="utf-8")
@@ -93,6 +151,11 @@ def transpile_file(path: Path) -> str:
     return transpile(source, lang_code)
 
 
+def detranspile_file(path: Path, lang_code: str, postfix: bool = False) -> str:
+    source = path.read_text(encoding="utf-8")
+    return detranspile(source, lang_code, postfix=postfix)
+
+
 def run_transpiled(original_path: Path, transpiled: str) -> None:
     import linecache