venv-now

#!/usr/bin/env bash

SOURCED=$([[ ${BASH_SOURCE[0]} != "$0" ]] && echo true || echo false)
if [[ $SOURCED == false ]]; then
	set -euo pipefail
fi
return-or-exit() {
	[[ $SOURCED == true ]] && return "$1" || exit "$1"
}

# Pure validation function - returns 0 if path is dangerous, 1 if safe
# Can be tested safely without triggering any file operations
# Parameters:
#   $1 - venv_dir: the raw directory argument
#   $2 - resolved_dir: the resolved/normalized path
#   $3 - current_dir: the current working directory
is_dangerous_venv_path() {
	local venv_dir="$1"
	local resolved_dir="$2"
	local current_dir="$3"

	[[ -z "$venv_dir" || "$venv_dir" == "." || "$venv_dir" == ".." ||
		"$venv_dir" == "/" || "$venv_dir" == "~" ||
		"$resolved_dir" == "$HOME" || "$resolved_dir" == "/" ||
		"$resolved_dir" == "$current_dir" ]]
}

# When sourced with VENV_NOW_SOURCE_ONLY=1, only export functions (for testing)
# This allows tests to call is_dangerous_venv_path() without triggering file ops
if [[ "${VENV_NOW_SOURCE_ONLY:-}" == "1" ]]; then
	return 0
fi

VENV_DIR=".venv"
REMOVE_EXISTING=true
SCRIPT_NAME=$(basename "$0")

usage() {
	local exit_code=${1:-0}
	cat <<EOF
Usage: $SCRIPT_NAME [DIRECTORY] [OPTIONS]

Create a new Python virtual environment in ./.venv by default. If the specified
directory already exists, it will be removed by default unless the --no-remove flag is
used. The virtual environment will be activated if the script is sourced.

Positional Arguments:
  DIRECTORY         The virtual environment directory name (default: .venv)

Options:
  -n, --no-remove   Do not remove an existing virtual environment
  -h, --help        Show this help message and exit

Examples:
    . $SCRIPT_NAME
    source $SCRIPT_NAME myenv --no-remove
    $SCRIPT_NAME .venv -n
EOF
	return-or-exit "$exit_code"
}

# Initialize empty positional argument
positional_arg_set=false

# Parse arguments
while [[ $# -gt 0 ]]; do
	case "$1" in
	-h | --help)
		usage
		;;
	-n | --no-remove)
		REMOVE_EXISTING=false
		shift
		;;
	-*)
		echo "Unknown option: $1" >&2
		usage 1
		;;
	*)
		if [ "$positional_arg_set" = false ]; then
			VENV_DIR="$1"
			positional_arg_set=true
		else
			echo "Error: Multiple directory arguments specified: '$VENV_DIR' and '$1'" >&2
			usage 1
		fi
		shift
		;;
	esac
done

# Find python executable (prefer python3 for systems without python symlink)
PYTHON_CMD="python"
if ! command -v python &>/dev/null && command -v python3 &>/dev/null; then
	PYTHON_CMD="python3"
fi

# Global safety check: refuse obviously dangerous targets
# Resolve and normalize the target virtual environment path safely,
# even if the directory does not exist yet.
RESOLVED_VENV_DIR="$(
	"$PYTHON_CMD" - "$VENV_DIR" <<'EOF'
from pathlib import Path
import sys

# Path.resolve() resolves '..' and symlinks without requiring the
# final path component to exist (strict=False is the default in 3.6+).
print(Path(sys.argv[1]).resolve(strict=False))
EOF
)" || {
	echo "Error: Failed to resolve path '$VENV_DIR'" >&2
	return-or-exit 1
}

# Get current directory for comparison
CURRENT_DIR="$(pwd -P)"

if is_dangerous_venv_path "$VENV_DIR" "$RESOLVED_VENV_DIR" "$CURRENT_DIR"; then
	echo "Error: Refusing to use dangerous path: '$VENV_DIR' (resolves to '$RESOLVED_VENV_DIR')" >&2
	return-or-exit 1
fi

if $REMOVE_EXISTING && [ -d "$VENV_DIR" ]; then
	echo "Removing existing virtual environment: $VENV_DIR"
	rm -rf -- "$VENV_DIR"
fi

echo "Creating virtual environment in: $VENV_DIR"
"$PYTHON_CMD" -m venv "$VENV_DIR"

if [ -f "$VENV_DIR/bin/activate" ]; then
	echo "Virtual environment created: $VENV_DIR"
else
	echo "Error: Virtual environment creation failed!" >&2
	return-or-exit 1
fi

if [[ $SOURCED == true ]]; then
	# shellcheck disable=SC1091
	{ . "$VENV_DIR/bin/activate" && echo "Virtual environment activated: $VENV_DIR"; } ||
		{
			echo "Error: Virtual environment activation failed!" >&2
			return 1
		}
fi