"""
    Change directory to provide relative paths for doctests
    >>> import os
    >>> filepath = os.path.dirname( os.path.realpath( __file__ ) )
    >>> datadir = os.path.realpath(os.path.join(filepath, '../../testing/data'))
    >>> os.chdir(datadir)

"""
from nipype.interfaces.base import (traits, TraitedSpec, File,
                                    CommandLine, CommandLineInputSpec, isdefined,
                                    InputMultiPath)
from nipype.utils.filemanip import split_filename
import os

class ImageStatsInputSpec(CommandLineInputSpec):
    in_files = InputMultiPath(File(exists=True), argstr='-images %s', mandatory=True,
                              position=-1, desc=('List of images to process. They must '
                                                 'be in the same space and have the same '
                                                 'dimensions.'))
    stat = traits.Enum("min", "max", "mean", "median", "sum", "std", "var",
                       argstr='-stat %s', units='NA', mandatory=True,
                       desc="The statistic to compute.")

    out_type = traits.Enum("float", "char", "short", "int", "long", "double",
                           argstr='-outputdatatype %s', usedefault=True,
                           desc=('A Camino data type string, default is "float". '
                                 'Type must be signed.'))
    output_root = File(argstr='-outputroot %s', mandatory=True,
                       desc=('Filename root prepended onto the names of the output '
                             ' files. The extension will be determined from the input.'))

class ImageStatsOutputSpec(TraitedSpec):
    out_file = File(exists=True, desc='Path of the file computed with the statistic chosen')

class ImageStats(CommandLine):
    """
    This program computes voxelwise statistics on a series of 3D images. The images
    must be in the same space; the operation is performed voxelwise and one output
    is produced per voxel.

    Examples
    --------

    >>> import nipype.interfaces.camino as cam
    >>> imstats = cam.ImageStats()
    >>> imstats.inputs.in_files = ['im1.nii','im2.nii','im3.nii']
    >>> imstats.inputs.stat = 'max'
    >>> imstats.run()                  # doctest: +SKIP
    """
    _cmd = 'imagestats'
    input_spec = ImageStatsInputSpec
    output_spec = ImageStatsOutputSpec

    def _list_outputs(self):
        outputs = self.output_spec().get()
        outputs['out_file'] = os.path.abspath(self._gen_outfilename())
        return outputs

    def _gen_outfilename(self):
        output_root = self.inputs.output_root
        first_file = self.inputs.in_files[0]
        _, _ , ext = split_filename(first_file)
        return output_root + ext
