# Source code for scm.plams.tools.units

import collections
import math
import numpy as np

from ..core.errors import UnitsError

__all__ = ['Units']

[docs]class Units:
"""A singleton class for unit converter.

All values are based on 2014 CODATA recommended values <http://physics.nist.gov/cuu/Constants>_.

The following constants and units are supported:

*   constants:

-   speed_of_light (also c)
-   electron_charge (also e)
-   Avogadro_constant (also NA)
-   Bohr_radius

*   distance:

-   Angstrom, A
-   Bohr, au, a.u.
-   nm
-   pm

*   reciprocal distance:

-   1/Angstrom, 1/A, Angstrom^-1, A^-1,
-   1/Bohr, Bohr^-1

*   angle:

-    degree, deg,
-    radian, rad,
-    grad
-    circle

*   energy:

-   au, a.u., Hartree
-   eV
-   kcal/mol
-   kJ/mol
-   cm^-1, cm-1

*   dipole moment:

-   au, a.u.
-   Cm
-   Debye, D

Example::

>>> print(Units.constants['speed_of_light'])
299792458
>>> print(Units.constants['e'])
1.6021766208e-19
>>> print(Units.convert(123, 'angstrom', 'bohr'))
232.436313431
>>> print(Units.convert([23.32, 145.0, -34.7], 'kJ/mol', 'kcal/mol'))
[5.573613766730401, 34.655831739961755, -8.293499043977056]
>>> print(Units.conversion_ratio('kcal/mol', 'kJ/mol'))
4.184

"""

constants = {}
constants['Avogadro_constant'] = constants['NA'] =  6.022140857e23   #http://physics.nist.gov/cgi-bin/cuu/Value?na
constants['speed_of_light'] = constants['c']     =  299792458   #http://physics.nist.gov/cgi-bin/cuu/Value?c
constants['electron_charge'] = constants['e']    =  1.6021766208e-19   #http://physics.nist.gov/cgi-bin/cuu/Value?e

distance = {}
distance['A'] = distance['Angstrom']                 =  1.0
distance['Bohr'] = distance['a.u.'] = distance['au'] =  1.0 / constants['Bohr_radius']
distance['nm']                                       = distance['A'] / 10.0
distance['pm']                                       = distance['A'] * 100.0

rec_distance = {}
rec_distance['1/A'] = rec_distance['1/Angstrom'] = rec_distance['A^-1'] = rec_distance['Angstrom^-1'] = 1.0

energy = {}
energy['au'] = energy['a.u.'] = energy['Hartree'] =  1.0
energy['eV']                                      =  27.21138602   #http://physics.nist.gov/cgi-bin/cuu/Value?hrev
energy['kJ/mol']                                  =  4.359744650e-21 * constants['NA']  #http://physics.nist.gov/cgi-bin/cuu/Value?hrj
energy['kcal/mol']                                =  energy['kJ/mol'] / 4.184
energy['cm^-1'] = energy['cm-1']                  =  219474.6313702   #http://physics.nist.gov/cgi-bin/cuu/Value?hrminv

angle = {}
angle['degree'] =  angle['deg'] = 1.0
angle['circle'] =  1.0 / 360.0

dipole = {}
dipole['au'] = dipole['a.u.'] =  1.0
dipole['Cm']                  =  constants['e'] * constants['Bohr_radius'] * 1e-10
dipole['Debye'] = dipole['D'] =  dipole['Cm'] * constants['c']* 1e21

dicts = {}
dicts['distance'] = distance
dicts['energy'] = energy
dicts['angle'] = angle
dicts['dipole'] = dipole
dicts['reciprocal distance'] = rec_distance

[docs]    def __init__(self):
raise UnitsError('Instances of Units cannot be created')

@classmethod
def find_unit(cls, unit):
ret = {}
for quantity in cls.dicts:
for k in cls.dicts[quantity]:
if k.lower() == unit.lower():
ret[quantity] = k
return ret

[docs]    @classmethod
def conversion_ratio(cls, inp, out):
"""Return conversion ratio from unit *inp* to *out*."""
inps = cls.find_unit(inp)
outs = cls.find_unit(out)
common = set(inps.keys()) & set(outs.keys())
if len(common) > 0:
quantity = common.pop()
d = cls.dicts[quantity]
return d[outs[quantity]]/d[inps[quantity]]
else:
if len(inps) == 0 and len(outs) == 0:
raise UnitsError("Unsupported units: '{}' and '{}'".format(inp, out))
if len(inps) > 0 and len(outs) > 0:
raise UnitsError("Invalid unit conversion: '{}' is a unit of {} and '{}' is a unit of {}".format(inp, ', '.join(list(inps.keys())), out, ', '.join(list(outs.keys()))))
else: #exactly one of (inps,outs) empty
invalid, nonempty = (out,inps) if len(inps) else (inp,outs)
if len(nonempty) == 1:
quantity = list(nonempty.keys())[0]
raise UnitsError("Invalid unit conversion: {} is not supported. Supported units for {}: {}".format(invalid, quantity, ', '.join(list(cls.dicts[quantity].keys()))))
else:
raise UnitsError("Invalid unit conversion: {} is not a supported unit for {}".format(invalid, ', '.join(list(nonempty.keys()))))

[docs]    @classmethod
def convert(cls, value, inp, out):
"""Convert *value* from unit *inp* to *out*.

*value* can be a single number or a container (list, tuple, numpy.array etc.). In the latter case a container of the same type and length is returned. Conversion happens recursively, so this method can be used to convert, for example, a list of lists of numbers, or any other hierarchical container structure. Conversion is applied on all levels, to all values that are numbers (also numpy number types). All other values (strings, bools etc.) remain unchanged.
"""
if value is None or isinstance(value, (bool, str)):
return value
if isinstance(value, collections.abc.Iterable):
t = type(value)
if t == np.ndarray:
t = np.array
v = [cls.convert(i, inp, out) for i in value]
return t(v)
if isinstance(value, (int, float, np.generic)):
return value * cls.conversion_ratio(inp,out)
return value