"""
Convert models to and from sasview.
"""
import warnings

# List of models which SasView versions don't contain the explicit 'scale' argument.
# When converting such a model, please update this list.
MODELS_WITHOUT_SCALE = [
    'teubner_strey',
    'broad_peak',
    'two_lorentzian',
    "two_power_law",
    'gel_fit',
    'gauss_lorentz_gel',
    'be_polyelectrolyte',
    'correlation_length',
    'fractal_core_shell'
    'binary_hard_sphere',
]

# List of models which SasView versions don't contain the explicit 'background' argument.
# When converting such a model, please update this list.
MODELS_WITHOUT_BACKGROUND = [
    'guinier',
]

PD_DOT = [
    ("", ""),
    ("_pd", ".width"),
    ("_pd_n", ".npts"),
    ("_pd_nsigma", ".nsigmas"),
    ("_pd_type", ".type"),
    ]
def _convert_pars(pars, mapping):
    """
    Rename the parameters and any associated polydispersity attributes.
    """
    newpars = pars.copy()
    for new, old in mapping.items():
        if old == new: continue
        for pd, dot in PD_DOT:
            if old+dot in newpars:
                if new is not None:
                    newpars[new+pd] = pars[old+dot]
                del newpars[old+dot]
    return newpars

def _rescale_sld(pars):
    """
    rescale all sld parameters in the new model definition by 1e6 so the
    numbers are nicer.  Relies on the fact that all sld parameters in the
    new model definition end with sld.
    """
    return dict((p, (v*1e6 if p.endswith('sld')
                     else v*1e-15 if 'ndensity' in p
                     else v))
                for p, v in pars.items())

def convert_model(name, pars):
    """
    Convert model from old style parameter names to new style.
    """
    _, _ = name, pars # lint
    raise NotImplementedError
    # need to load all new models in order to determine old=>new
    # model name mapping

def _unscale_sld(pars):
    """
    rescale all sld parameters in the new model definition by 1e6 so the
    numbers are nicer.  Relies on the fact that all sld parameters in the
    new model definition end with sld.
    """
    return dict((p, (v*1e-6 if p.endswith('sld')
                     else v*1e15 if 'ndensity' in p
                     else v))
                for p, v in pars.items())

def _remove_pd(pars, key, name):
    """
    Remove polydispersity from the parameter list.

    Note: operates in place
    """
    # Bumps style parameter names
    pd = pars.pop(key+".width", 0.0)
    pd_n = pars.pop(key+".npts", 0)
    if pd != 0.0 and pd_n != 0:
        warnings.warn("parameter %s not polydisperse in sasview %s"%(key, name))
    pars.pop(key+".nsigmas", None)
    pars.pop(key+".type", None)
    return pars

def _revert_pars(pars, mapping):
    """
    Rename the parameters and any associated polydispersity attributes.
    """
    newpars = pars.copy()

    for new, old in mapping.items():
        for pd, dot in PD_DOT:
            if old and old+pd == new+dot:
                continue
            if new+pd in newpars:
                if old is not None:
                    newpars[old+dot] = pars[new+pd]
                del newpars[new+pd]
    for k in list(newpars.keys()):
        for pd, dot in PD_DOT[1:]:  # skip "" => ""
            if k.endswith(pd):
                newpars[k[:-len(pd)]+dot] = newpars[k]
                del newpars[k]
    return newpars

def revert_pars(model_info, pars):
    """
    Convert model from new style parameter names to old style.
    """
    mapping = model_info['oldpars']
    oldpars = _revert_pars(_unscale_sld(pars), mapping)

    # Note: update compare.constrain_pars to match
    name = model_info['id']
    if name in MODELS_WITHOUT_SCALE or model_info['structure_factor']:
        if oldpars.pop('scale', 1.0) != 1.0:
            warnings.warn("parameter scale not used in sasview %s"%name)
    if name in MODELS_WITHOUT_BACKGROUND or model_info['structure_factor']:
        if oldpars.pop('background', 0.0) != 0.0:
            warnings.warn("parameter background not used in sasview %s"%name)

    # If it is a product model P*S, then check the individual forms for special
    # cases.  Note: despite the structure factor alone not having scale or
    # background, the product model does, so this is below the test for
    # models without scale or background.
    namelist = name.split('*') if '*' in name else [name]
    for name in namelist:
        if name == 'pearl_necklace':
            _remove_pd(oldpars, 'num_pearls', name)
            _remove_pd(oldpars, 'thick_string', name)
        elif name == 'core_shell_parallelepiped':
            _remove_pd(oldpars, 'rimA', name)
            _remove_pd(oldpars, 'rimB', name)
            _remove_pd(oldpars, 'rimC', name)
        elif name == 'rpa':
            # convert scattering lengths from femtometers to centimeters
            for p in "La", "Lb", "Lc", "Ld":
                if p in oldpars: oldpars[p] *= 1e-13

    return oldpars

def constrain_new_to_old(model_info, pars):
    """
    Restrict parameter values to those that will match sasview.
    """
    name = model_info['id']
    # Note: update convert.revert_model to match
    if name in MODELS_WITHOUT_SCALE or model_info['structure_factor']:
        pars['scale'] = 1
    if name in MODELS_WITHOUT_BACKGROUND or model_info['structure_factor']:
        pars['background'] = 0
    # sasview multiplies background by structure factor
    if '*' in name:
        pars['background'] = 0

    # If it is a product model P*S, then check the individual forms for special
    # cases.  Note: despite the structure factor alone not having scale or
    # background, the product model does, so this is below the test for
    # models without scale or background.
    namelist = name.split('*') if '*' in name else [name]
    for name in namelist:
        if name == 'pearl_necklace':
            pars['string_thickness_pd_n'] = 0
            pars['number_of_pearls_pd_n'] = 0
        elif name == 'line':
            pars['scale'] = 1
            pars['background'] = 0
        elif name == 'rpa':
            pars['case_num'] = int(pars['case_num'])