Add script detection, env shebang parser, and opt-in content guessing

src/rp/cli.py

@@ -65,6 +65,13 @@ def main(
             help="Use pager for output. Default: auto-detect.",
         ),
     ] = None,
+    guess_content: Annotated[
+        bool,
+        typer.Option(
+            "--guess-content/--no-guess-content",
+            help="Use heuristic content-based type detection as a fallback.",
+        ),
+    ] = False,
     version: Annotated[
         bool | None,
         typer.Option(
@@ -84,6 +91,7 @@ def main(
         theme: Pygments color theme.
         line_numbers: Show line numbers. Default: auto.
         pager: Use pager for output. Default: auto-detect.
+        guess_content: Use heuristic content-based type detection as a fallback.
         version: Show version and exit.
     """
     console = Console()
@@ -114,7 +122,12 @@ def main(
         console.print("[dim]Empty input, nothing to display.[/dim]")
         raise typer.Exit()
 
-    file_type = detect_type(path=file_path, content=content, explicit_type=file_type)
+    file_type = detect_type(
+        path=file_path,
+        content=content,
+        explicit_type=file_type,
+        guess_content=guess_content,
+    )
 
     options = RenderOptions(
         theme=theme,

src/rp/detect.py

@@ -3,8 +3,13 @@
 from __future__ import annotations
 
 import json
+import shlex
+from numbers import Real
 from pathlib import Path
 
+from pygments.lexers import guess_lexer
+from pygments.util import ClassNotFound
+
 EXTENSION_MAP: dict[str, str] = {
     ".md": "markdown",
     ".json": "json",
@@ -52,13 +57,153 @@ EXTENSION_MAP: dict[str, str] = {
 _FILENAME_MAP: dict[str, str] = {
     "Dockerfile": "docker",
     "Makefile": "make",
+    ".bashrc": "bash",
+    ".zshrc": "bash",
+    ".profile": "bash",
 }
 
+_SHEBANG_MAP: dict[str, str] = {
+    "python": "python",
+    "python3": "python",
+    "python2": "python",
+    "sh": "bash",
+    "bash": "bash",
+    "zsh": "bash",
+}
+
+_ENV_OPTIONS_WITH_ARG = {
+    "-C",
+    "-u",
+    "--argv0",
+    "--block-signal",
+    "--chdir",
+    "--default-signal",
+    "--ignore-signal",
+    "--unset",
+}
+
+_ENV_LONG_OPTIONS_WITH_ARG = {
+    opt.lstrip("-") for opt in _ENV_OPTIONS_WITH_ARG if opt.startswith("--")
+}
+
+
+def _is_env_assignment(part: str) -> bool:
+    """Return whether a token looks like an env-style variable assignment."""
+    name, separator, _ = part.partition("=")
+    return (
+        bool(separator)
+        and bool(name)
+        and (name[0].isalpha() or name[0] == "_")
+        and all(char.isalnum() or char == "_" for char in name[1:])
+    )
+
+
+def _detect_env_program(parts: list[str]) -> str | None:
+    """Return the actual program name from an env-based shebang."""
+    remaining = parts[1:]
+
+    while remaining:
+        part = remaining.pop(0)
+
+        if part.startswith("--split-string="):
+            try:
+                remaining = shlex.split(part.partition("=")[2]) + remaining
+            except ValueError:
+                return None
+            continue
+
+        if part in {"-S", "--split-string"}:
+            if not remaining:
+                return None
+            try:
+                remaining = shlex.split(remaining.pop(0)) + remaining
+            except ValueError:
+                return None
+            continue
+
+        if part.startswith("-S"):
+            try:
+                remaining = shlex.split(part[2:]) + remaining
+            except ValueError:
+                return None
+            continue
+
+        if part == "--":
+            if not remaining:
+                return None
+            return Path(remaining[0]).name
+
+        if part in _ENV_OPTIONS_WITH_ARG:
+            if not remaining:
+                return None
+            remaining.pop(0)
+            continue
+
+        if any(part.startswith(f"{option}=") for option in _ENV_LONG_OPTIONS_WITH_ARG):
+            continue
+
+        if part.startswith("-"):
+            continue
+
+        if _is_env_assignment(part):
+            continue
+
+        return Path(part).name
+
+    return None
+
+
+def _detect_shebang(content: str) -> str | None:
+    """Return a lexer from the first shebang line when recognized."""
+    lines = content.splitlines()
+    first_line = lines[0] if lines else content
+    if not first_line.startswith("#!"):
+        return None
+
+    command = first_line[2:].strip()
+    if not command:
+        return None
+
+    try:
+        parts = shlex.split(command)
+    except ValueError:
+        return None
+
+    if not parts:
+        return None
+
+    program = Path(parts[0]).name
+    if program == "env":
+        env_program = _detect_env_program(parts)
+        if env_program is None:
+            return None
+        program = env_program
+
+    return _SHEBANG_MAP.get(program)
+
+
+def _detect_pygments_content(content: str) -> str | None:
+    """Return a lexer guessed from content when Pygments is confident."""
+    try:
+        lexer = guess_lexer(content)
+    except ClassNotFound:
+        return None
+
+    aliases: list[str] = getattr(lexer, "aliases", [])
+    alias = aliases[0] if aliases else None
+    analyse_text = getattr(lexer, "analyse_text", None)
+    score_value = analyse_text(content) if callable(analyse_text) else 0.0
+    score = float(score_value) if isinstance(score_value, Real) else 0.0
+    if alias == "text" or score < 0.5:
+        return None
+    return alias
+
 
 def detect_type(
     path: str | None = None,
     content: str | None = None,
     explicit_type: str | None = None,
+    guess_content: bool = False,
 ) -> str:
     """Detect the file type for syntax highlighting.
 
@@ -66,13 +211,16 @@ def detect_type(
     1. Explicit type if provided
     2. Filename-based mapping (for example, Dockerfile)
     3. Extension-based mapping
-    4. JSON if content starts with '{' or '[' and parses successfully
-    5. Fallback to 'text'
+    4. Shebang-based mapping for script content
+    5. JSON if content starts with '{' or '[' and parses successfully
+    6. Heuristic content guessing when enabled
+    7. Fallback to 'text'
 
     Args:
         path: File path for filename and extension detection.
         content: File content for JSON detection.
         explicit_type: Override auto-detection with explicit type.
+        guess_content: Enable heuristic content-based lexer guessing.
 
     Returns:
         Pygments lexer name for the detected file type.
@@ -90,6 +238,10 @@ def detect_type(
             return EXTENSION_MAP[suffix]
 
     if content is not None:
+        shebang_type = _detect_shebang(content)
+        if shebang_type is not None:
+            return shebang_type
+
         stripped = content.strip()
         if stripped and (
             (stripped[0] == "{" and stripped[-1] == "}")
@@ -101,4 +253,9 @@ def detect_type(
             except (json.JSONDecodeError, ValueError):
                 pass
 
+        if guess_content:
+            pygments_type = _detect_pygments_content(content)
+            if pygments_type is not None:
+                return pygments_type
+
     return "text"