"""Helpers for checking external dependencies."""

import os
import sys
from distutils.spawn import find_executable


EXIFTOOL_ERROR = u"""
It looks like you don't have exiftool installed, which Elodie requires.
Please take a look at the installation steps in the readme:

https://github.com/jmathai/elodie#install-everything-you-need
""".lstrip()

PYEXIV2_ERROR = u"""
{error_class_name}: {error}

It looks like you don't have pyexiv2 installed, which Elodie requires for
geolocation. Please take a look at the installation steps in the readme:

https://github.com/jmathai/elodie#install-everything-you-need
""".lstrip()


def get_exiftool():
    """Get path to executable exiftool binary.

    We wrap this since we call it in a few places and we do a fallback.

    @returns, None or string
    """
    path = find_executable('exiftool')
    # If exiftool wasn't found we try to brute force the homebrew location
    if path is None:
        path = '/usr/local/bin/exiftool'
        if not os.path.isfile(path) or not os.access(path, os.X_OK):
            return None
    return path


def verify_dependencies():
    """Verify that external dependencies are installed.

    Prints a message to stderr and returns False if any dependencies are
    missing.

    @returns, bool
    """
    exiftool = get_exiftool()
    if exiftool is None:
        print >>sys.stderr, EXIFTOOL_ERROR
        return False

    try:
        import pyexiv2
    except ImportError as e:
        print >>sys.stderr, PYEXIV2_ERROR.format(
            error_class_name=e.__class__.__name__, error=e)
        return False

    return True