'''Generate func_defs.pxd'''

import pathlib


def _gen_func_defs_pxd(outfile, x_funcs, no_x_funcs, max_num_inputs=4):
    '''
    Cython does not support template parameter packs, so to keep it
    from freaking out, we'll manually produce all the different template
    expansions we need to call in the cython wrappers.
    '''

    contents = ('# This file was generated by stats/_boost/include/'
                '_gen_func_defs_pxd.py\n')
    contents += '# All modifications to this file will be overwritten.\n'
    hdr = str((pathlib.Path(__file__).parent / "func_defs.hpp").as_posix())
    contents += f'cdef extern from "{hdr}" namespace "" nogil:\n'

    for ii in range(1, max_num_inputs+1):
        template_args = ', '.join(f'T{jj} arg{jj}' for jj in range(1, ii+1))
        template_types = ', '.join(f'T{jj}' for jj in range(1, ii+1))

        # for all the different "overloads", we need to produce a
        # distinct Cython reference;
        # assumes that all number template types are the same,
        # i.e. RealType == T1 == T2 == etc
        for func in x_funcs:
            fname = f'boost_{func}'
            tmpl = f'Dist, RealType, {template_types}'
            contents += (f'    RealType {fname}{ii} "{fname}" '
                         f'[{tmpl}](RealType x, {template_args})\n')
        for func in no_x_funcs:
            fname = f'boost_{func}'
            tmpl = f'Dist, RealType, {template_types}'
            contents += (f'    RealType {fname}{ii} "{fname}" '
                         f'[{tmpl}]({template_args})\n')

    # patch for boost::math::beta_distibution to handle x = 0 when a < 1
    # and x = 1 when beta < 1
    contents += ('    RealType boost_pdf_beta2 "boost_pdf_beta" '
                 '[Dist, RealType, T1, T2](RealType x, T1 a, T2 b)')

    with open(outfile, 'w') as fp:
        fp.write(contents)