from __future__ import (absolute_import, division, print_function)

from .constants import Constants, ConversionFactors

def _apply_conv_fact(var, vartype, var_unit, dest_unit):

"""Return the variable converted to different units using a conversion

factor.

Args:

var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A

variable.

vartype (:obj:`str`): The type of variable. Choices are: 'wind',

'pressure', 'temp', or 'height'.

var_unit (:obj:`str`): The variable's current units.

dest_unit (:obj:`str`): The desired units.

Returns:

:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in

the desired units.

"""

if var_unit == dest_unit:

return var

# Note, case where var_unit and dest_unit are base unit, should be

# handled above

if var_unit == _BASE_UNITS[vartype]:

return var*(_CONV_FACTORS[vartype]["to_dest"][dest_unit])

else:

if dest_unit == _BASE_UNITS[vartype]:

return var*(_CONV_FACTORS[vartype]["to_base"][var_unit])

else:

return var*(_CONV_FACTORS[vartype]["to_base"][var_unit] *

_CONV_FACTORS[vartype]["to_dest"][dest_unit])

def _to_kelvin(var, var_unit):

"""Return the variable in Kelvin.

Args:

var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A

variable.

var_unit (:obj:`str`): The variable's current units.

Returns:

:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in

Kelvin.

"""

if var_unit == "c":

return var + Constants.CELKEL

elif var_unit == "f":

return (var - 32.0) * (5.0/9.0) + Constants.CELKEL

def _k_to_c(var):

"""Return the variable in Celsius.

Args:

var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A

variable in units of Kelvin.

Returns:

:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in

Celsius.

"""

return var - Constants.CELKEL

def _k_to_f(var):

"""Return the variable in Fahrenheit.

Args:

var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A

variable in units of Kelvin.

Returns:

:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in

Fahrenheit.

"""

return 1.8 * _k_to_c(var) + 32.0

def _apply_temp_conv(var, var_unit, dest_unit):

"""Return the variable converted to different units using a temperature

conversion algorithm.

Args:

var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A

variable.

var_unit (:obj:`str`): The variable's current units.

dest_unit (:obj:`str`): The desired units.

Returns:

:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in

the desired units.

"""

if dest_unit == var_unit:

return var

if var_unit != _BASE_UNITS["temp"]:

tk = _to_kelvin(var, var_unit)

if dest_unit == _BASE_UNITS["temp"]:

return tk

else:

return (_TEMP_CONV_METHODS[dest_unit])(tk)

else:

return (_TEMP_CONV_METHODS[dest_unit])(var)

# A mapping of unit names to their dictionary key names

_UNIT_ALIASES = {"mps": "m s-1",

"m/s": "m s-1",

"ms-1": "m s-1",

"meters_per_second": "m s-1",

"metres_per_second": "m s-1",

"knots": "kt",

"knot": "kt",

"kts": "kt",

"kn": "kt",

"miles_per_hour": "mi h-1",

"mih-1": "mi h-1",

"mph": "mi h-1",

"mi/h": "mi h-1",

"kmph": "km h-1",

"kmh-1": "km h-1",

"km/h": "km h-1",

"kilometers_per_hour": "km h-1",

"kilometres_per_hour": "km h-1",

"ft/s": "ft s-1",

"ft/sec": "ft s-1",

"fps": "ft s-1",

"fs-1": "ft s-1",

"feet_per_second": "ft s-1",

"pascal": "pa",

"pascals": "pa",

"hecto_pascal": "hpa",

"hecto_pascals": "hpa",

"millibar": "mb",

"millibars": "mb",

"mbar": "mb",

"kelvin": "k",

"degree_kelvin": "k",

"degrees_kelvin": "k",

"degree_k": "k",

"degrees_k": "k",

"degreek": "k",

"degreesk": "k",

"degk": "k",

"degsk": "k",

"deg_k": "k",

"degs_k": "k",

"deg k": "k",

"degs k": "k",

"celsius": "c",

"degree_celsius": "c",

"degrees_celsius": "c",

"degree_c": "c",

"degrees_c": "c",

"degreec": "c",

"degreesc": "c",

"degc": "c",

"degsc": "c",

"deg_c": "c",

"degs_c": "c",

"deg c": "c",

"degs c": "c",

"fahrenheit": "f",

"degree_fahrenheit": "f",

"degrees_fahrenheit": "f",

"degree_f": "f",

"degrees_f": "f",

"degreef": "f",

"degreesf": "f",

"degf": "f",

"degsf": "f",

"deg_f": "f",

"degs_f": "f",

"deg f": "f",

"degs f": "f",

"meter": "m",

"meters": "m",

"metre": "m",

"metres": "m",

"kilometer": "km",

"kilometers": "km",

"dekameter": "dm",

"dekameters": "dm",

"decameter": "dm",

"decameters": "dm",

"dekametre": "dm",

"dekametres": "dm",

"decametre": "dm",

"decametres": "dm",

"dam": "dm",

"dkm": "dm",

"feet": "ft",

"foot": "ft",

"mile": "mi",

"miles": "mi"

}

# A mapping of unit types to the avaible units

_VALID_UNITS = {"wind": ["m s-1", "kt", "mi h-1", "km h-1", "ft s-1"],

"pressure": ["pa", "hpa", "mb", "torr", "mmhg", "atm"],

"temp": ["k", "f", "c"],

"height": ["m", "km", "dm", "ft", "mi"]

}

# Conversion factor map for wind from base units

_WIND_BASE_FACTORS = {"kt": ConversionFactors.MPS_TO_KTS,

"km h-1": ConversionFactors.MPS_TO_KMPH,

"mi h-1": ConversionFactors.MPS_TO_MPH,

"ft s-1": ConversionFactors.MPS_TO_FPS

}

# Conversion factor map to base units

_WIND_TOBASE_FACTORS = {"kt": 1.0/ConversionFactors.MPS_TO_KTS,

"km h-1": 1.0/ConversionFactors.MPS_TO_KMPH,

"mi h-1": 1.0/ConversionFactors.MPS_TO_MPH,

"ft s-1": 1.0/ConversionFactors.MPS_TO_FPS

}

# Conversion factor map for pressure from base units

_PRES_BASE_FACTORS = {"hpa": ConversionFactors.PA_TO_HPA,

"mb": ConversionFactors.PA_TO_HPA,

"torr": ConversionFactors.PA_TO_TORR,

"mmhg": ConversionFactors.PA_TO_MMHG,

"atm": ConversionFactors.PA_TO_ATM

}

# Conversion factor map for pressure to base units

_PRES_TOBASE_FACTORS = {"hpa": 1.0/ConversionFactors.PA_TO_HPA,

"mb": 1.0/ConversionFactors.PA_TO_HPA,

"torr": 1.0/ConversionFactors.PA_TO_TORR,

"mmhg": 1.0/ConversionFactors.PA_TO_MMHG,

"atm": 1.0/ConversionFactors.PA_TO_ATM

}

# Conversion factor map for height from base units

_HEIGHT_BASE_FACTORS = {"km": ConversionFactors.M_TO_KM,

"dm": ConversionFactors.M_TO_DM,

"ft": ConversionFactors.M_TO_FT,

"mi": ConversionFactors.M_TO_MILES

}

# Conversion factor map for height to base units

_HEIGHT_TOBASE_FACTORS = {"km": 1.0/ConversionFactors.M_TO_KM,

"dm": 1.0/ConversionFactors.M_TO_DM,

"ft": 1.0/ConversionFactors.M_TO_FT,

"mi": 1.0/ConversionFactors.M_TO_MILES

}

# Mapping of unit type to base unit type

_BASE_UNITS = {"wind": "m s-1",

"pressure": "pa",

"temp": "k",

"height": "m"

}

# A mapping of unit type to a mapping of to/from base conversion factors

_CONV_FACTORS = {"wind": {"to_dest": _WIND_BASE_FACTORS,

"to_base": _WIND_TOBASE_FACTORS},

"pressure": {"to_dest": _PRES_BASE_FACTORS,

"to_base": _PRES_TOBASE_FACTORS},

"height": {"to_dest": _HEIGHT_BASE_FACTORS,

"to_base": _HEIGHT_TOBASE_FACTORS}

}

# A mapping of temperature type to the conversion function

_TEMP_CONV_METHODS = {"c": _k_to_c,

"f": _k_to_f

}

def dealias_and_clean_unit(unit):

"""Return the properly cleaned and dealiased unit name.

Args:

unit (:obj:`str`): The unit name.

Returns:

:obj:`str`: A unit name suitable for dictionary key lookups.

"""

cleaned_unit = " ".join(unit.lower().split())

dealiased = _UNIT_ALIASES.get(cleaned_unit, None)

return cleaned_unit if dealiased is None else dealiased

def check_units(unit, unit_type):

"""Raise an exception if the unit name is invalid.

Args:

unit (:obj:`str`): The unit name.

unit_type (:obj:`str`): The type of unit.

Returns:

None

Raises:

:class:`ValueError`: Raised when the unit name is invalid.

"""

u_cleaned = dealias_and_clean_unit(unit)

if u_cleaned not in _VALID_UNITS[unit_type]:

raise ValueError("invalid unit type '{}'".format(unit))

def do_conversion(var, vartype, var_unit, dest_unit):

"""Return the variable converted to different units.

Args:

var (:class:`xarray.DataArray` or :class:`numpy.ndarray`): A

variable.

vartype (:obj:`str`): The type of variable. Choices are: 'wind',

'pressure', 'temp', or 'height'.

var_unit (:obj:`str`): The variable's current units.

dest_unit (:obj:`str`): The desired units.

Returns:

:class:`xarray.DataArray` or :class:`numpy.ndarray`: The variable in

the desired units.

"""

u_cleaned = dealias_and_clean_unit(dest_unit)

if vartype != "temp":

return _apply_conv_fact(var, vartype, var_unit.lower(), u_cleaned)

else:

return _apply_temp_conv(var, var_unit.lower(), u_cleaned)