# Licensed under a 3-clause BSD style license - see LICENSE.rst

# This module includes files automatically generated from ply (these end in
# _lextab.py and _parsetab.py). To generate these files, remove them from this
# folder, then build astropy and run the tests in-place:
#
#   python setup.py build_ext --inplace
#   pytest astropy/units
#
# You can then commit the changes to the re-generated _lextab.py and
# _parsetab.py files.

"""
Handles a "generic" string format for units
"""

import re
import unicodedata
import warnings
from fractions import Fraction

from astropy.utils import classproperty, deprecated, parsing
from astropy.utils.misc import did_you_mean

from . import core
from .base import Base


class Generic(Base):
    """
    A "generic" format.

    The syntax of the format is based directly on the FITS standard,
    but instead of only supporting the units that FITS knows about, it
    supports any unit available in the `astropy.units` namespace.
    """

    _tokens = (
        "COMMA",
        "DOUBLE_STAR",
        "STAR",
        "PERIOD",
        "SOLIDUS",
        "CARET",
        "OPEN_PAREN",
        "CLOSE_PAREN",
        "FUNCNAME",
        "UNIT",
        "SIGN",
        "UINT",
        "UFLOAT",
    )

    @classproperty(lazy=True)
    def _all_units(cls):
        return cls._generate_unit_names()

    @classproperty(lazy=True)
    def _units(cls):
        return cls._all_units[0]

    @classproperty(lazy=True)
    def _deprecated_units(cls):
        return cls._all_units[1]

    @classproperty(lazy=True)
    def _functions(cls):
        return cls._all_units[2]

    @classproperty(lazy=True)
    def _parser(cls):
        return cls._make_parser()

    @classproperty(lazy=True)
    def _lexer(cls):
        return cls._make_lexer()

    @classmethod
    def _make_lexer(cls):
        tokens = cls._tokens

        t_COMMA = r"\,"
        t_STAR = r"\*"
        t_PERIOD = r"\."
        t_SOLIDUS = r"/"
        t_DOUBLE_STAR = r"\*\*"
        t_CARET = r"\^"
        t_OPEN_PAREN = r"\("
        t_CLOSE_PAREN = r"\)"

        # NOTE THE ORDERING OF THESE RULES IS IMPORTANT!!
        # Regular expression rules for simple tokens
        def t_UFLOAT(t):
            r"((\d+\.?\d*)|(\.\d+))([eE][+-]?\d+)?"
            if not re.search(r"[eE\.]", t.value):
                t.type = "UINT"
                t.value = int(t.value)
            elif t.value.endswith("."):
                t.type = "UINT"
                t.value = int(t.value[:-1])
            else:
                t.value = float(t.value)
            return t

        def t_UINT(t):
            r"\d+"
            t.value = int(t.value)
            return t

        def t_SIGN(t):
            r"[+-](?=\d)"
            t.value = int(t.value + "1")
            return t

        # This needs to be a function so we can force it to happen
        # before t_UNIT
        def t_FUNCNAME(t):
            r"((sqrt)|(ln)|(exp)|(log)|(mag)|(dB)|(dex))(?=\ *\()"
            return t

        def t_UNIT(t):
            "%|([YZEPTGMkhdcmu\N{MICRO SIGN}npfazy]?'((?!\\d)\\w)+')|((?!\\d)\\w)+"
            t.value = cls._get_unit(t)
            return t

        t_ignore = " "

        # Error handling rule
        def t_error(t):
            raise ValueError(f"Invalid character at col {t.lexpos}")

        return parsing.lex(
            lextab="generic_lextab", package="astropy/units", reflags=int(re.UNICODE)
        )

    @classmethod
    def _make_parser(cls):
        """
        The grammar here is based on the description in the `FITS
        standard
        <http://fits.gsfc.nasa.gov/standard30/fits_standard30aa.pdf>`_,
        Section 4.3, which is not terribly precise.  The exact grammar
        is here is based on the YACC grammar in the `unity library
        <https://bitbucket.org/nxg/unity/>`_.

        This same grammar is used by the `"fits"` and `"vounit"`
        formats, the only difference being the set of available unit
        strings.
        """
        tokens = cls._tokens

        def p_main(p):
            """
            main : unit
                 | structured_unit
                 | structured_subunit
            """
            if isinstance(p[1], tuple):
                # Unpack possible StructuredUnit inside a tuple, ie.,
                # ignore any set of very outer parentheses.
                p[0] = p[1][0]
            else:
                p[0] = p[1]

        def p_structured_subunit(p):
            """
            structured_subunit : OPEN_PAREN structured_unit CLOSE_PAREN
            """
            # We hide a structured unit enclosed by parentheses inside
            # a tuple, so that we can easily distinguish units like
            # "(au, au/day), yr" from "au, au/day, yr".
            p[0] = (p[2],)

        def p_structured_unit(p):
            """
            structured_unit : subunit COMMA
                            | subunit COMMA subunit
            """
            from astropy.units.structured import StructuredUnit

            inputs = (p[1],) if len(p) == 3 else (p[1], p[3])
            units = ()
            for subunit in inputs:
                if isinstance(subunit, tuple):
                    # Structured unit that should be its own entry in the
                    # new StructuredUnit (was enclosed in parentheses).
                    units += subunit
                elif isinstance(subunit, StructuredUnit):
                    # Structured unit whose entries should be
                    # individually added to the new StructuredUnit.
                    units += subunit.values()
                else:
                    # Regular unit to be added to the StructuredUnit.
                    units += (subunit,)

            p[0] = StructuredUnit(units)

        def p_subunit(p):
            """
            subunit : unit
                    | structured_unit
                    | structured_subunit
            """
            p[0] = p[1]

        def p_unit(p):
            """
            unit : product_of_units
                 | factor product_of_units
                 | factor product product_of_units
                 | division_product_of_units
                 | factor division_product_of_units
                 | factor product division_product_of_units
                 | inverse_unit
                 | factor inverse_unit
                 | factor product inverse_unit
                 | factor
            """
            from astropy.units.core import Unit

            if len(p) == 2:
                p[0] = Unit(p[1])
            elif len(p) == 3:
                p[0] = Unit(p[1] * p[2])
            elif len(p) == 4:
                p[0] = Unit(p[1] * p[3])

        def p_division_product_of_units(p):
            """
            division_product_of_units : division_product_of_units division product_of_units
                                      | product_of_units
            """
            from astropy.units.core import Unit

            if len(p) == 4:
                p[0] = Unit(p[1] / p[3])
            else:
                p[0] = p[1]

        def p_inverse_unit(p):
            """
            inverse_unit : division unit_expression
            """
            p[0] = p[2] ** -1

        def p_factor(p):
            """
            factor : factor_fits
                   | factor_float
                   | factor_int
            """
            p[0] = p[1]

        def p_factor_float(p):
            """
            factor_float : signed_float
                         | signed_float UINT signed_int
                         | signed_float UINT power numeric_power
            """
            if cls.name == "fits":
                raise ValueError("Numeric factor not supported by FITS")
            if len(p) == 4:
                p[0] = p[1] * p[2] ** float(p[3])
            elif len(p) == 5:
                p[0] = p[1] * p[2] ** float(p[4])
            elif len(p) == 2:
                p[0] = p[1]

        def p_factor_int(p):
            """
            factor_int : UINT
                       | UINT signed_int
                       | UINT power numeric_power
                       | UINT UINT signed_int
                       | UINT UINT power numeric_power
            """
            if cls.name == "fits":
                raise ValueError("Numeric factor not supported by FITS")
            if len(p) == 2:
                p[0] = p[1]
            elif len(p) == 3:
                p[0] = p[1] ** float(p[2])
            elif len(p) == 4:
                if isinstance(p[2], int):
                    p[0] = p[1] * p[2] ** float(p[3])
                else:
                    p[0] = p[1] ** float(p[3])
            elif len(p) == 5:
                p[0] = p[1] * p[2] ** p[4]

        def p_factor_fits(p):
            """
            factor_fits : UINT power OPEN_PAREN signed_int CLOSE_PAREN
                        | UINT power OPEN_PAREN UINT CLOSE_PAREN
                        | UINT power signed_int
                        | UINT power UINT
                        | UINT SIGN UINT
                        | UINT OPEN_PAREN signed_int CLOSE_PAREN
            """
            if p[1] != 10:
                if cls.name == "fits":
                    raise ValueError("Base must be 10")
                else:
                    return
            if len(p) == 4:
                if p[2] in ("**", "^"):
                    p[0] = 10 ** p[3]
                else:
                    p[0] = 10 ** (p[2] * p[3])
            elif len(p) == 5:
                p[0] = 10 ** p[3]
            elif len(p) == 6:
                p[0] = 10 ** p[4]

        def p_product_of_units(p):
            """
            product_of_units : unit_expression product product_of_units
                             | unit_expression product_of_units
                             | unit_expression
            """
            if len(p) == 2:
                p[0] = p[1]
            elif len(p) == 3:
                p[0] = p[1] * p[2]
            else:
                p[0] = p[1] * p[3]

        def p_unit_expression(p):
            """
            unit_expression : function
                            | unit_with_power
                            | OPEN_PAREN product_of_units CLOSE_PAREN
            """
            if len(p) == 2:
                p[0] = p[1]
            else:
                p[0] = p[2]

        def p_unit_with_power(p):
            """
            unit_with_power : UNIT power numeric_power
                            | UNIT numeric_power
                            | UNIT
            """
            if len(p) == 2:
                p[0] = p[1]
            elif len(p) == 3:
                p[0] = p[1] ** p[2]
            else:
                p[0] = p[1] ** p[3]

        def p_numeric_power(p):
            """
            numeric_power : sign UINT
                          | OPEN_PAREN paren_expr CLOSE_PAREN
            """
            if len(p) == 3:
                p[0] = p[1] * p[2]
            elif len(p) == 4:
                p[0] = p[2]

        def p_paren_expr(p):
            """
            paren_expr : sign UINT
                       | signed_float
                       | frac
            """
            if len(p) == 3:
                p[0] = p[1] * p[2]
            else:
                p[0] = p[1]

        def p_frac(p):
            """
            frac : sign UINT division sign UINT
            """
            p[0] = Fraction(p[1] * p[2], p[4] * p[5])

        def p_sign(p):
            """
            sign : SIGN
                 |
            """
            if len(p) == 2:
                p[0] = p[1]
            else:
                p[0] = 1

        def p_product(p):
            """
            product : STAR
                    | PERIOD
            """

        def p_division(p):
            """
            division : SOLIDUS
            """

        def p_power(p):
            """
            power : DOUBLE_STAR
                  | CARET
            """
            p[0] = p[1]

        def p_signed_int(p):
            """
            signed_int : SIGN UINT
            """
            p[0] = p[1] * p[2]

        def p_signed_float(p):
            """
            signed_float : sign UINT
                         | sign UFLOAT
            """
            p[0] = p[1] * p[2]

        def p_function_name(p):
            """
            function_name : FUNCNAME
            """
            p[0] = p[1]

        def p_function(p):
            """
            function : function_name OPEN_PAREN main CLOSE_PAREN
            """
            if p[1] == "sqrt":
                p[0] = p[3] ** 0.5
                return
            elif p[1] in ("mag", "dB", "dex"):
                function_unit = cls._parse_unit(p[1])
                # In Generic, this is callable, but that does not have to
                # be the case in subclasses (e.g., in VOUnit it is not).
                if callable(function_unit):
                    p[0] = function_unit(p[3])
                    return

            raise ValueError(f"'{p[1]}' is not a recognized function")

        def p_error(p):
            raise ValueError()

        return parsing.yacc(tabmodule="generic_parsetab", package="astropy/units")

    @classmethod
    def _get_unit(cls, t):
        try:
            return cls._parse_unit(t.value)
        except ValueError as e:
            registry = core.get_current_unit_registry()
            if t.value in registry.aliases:
                return registry.aliases[t.value]

            raise ValueError(f"At col {t.lexpos}, {str(e)}")

    @classmethod
    def _parse_unit(cls, s, detailed_exception=True):
        registry = core.get_current_unit_registry().registry
        if s in cls._unit_symbols:
            s = cls._unit_symbols[s]

        elif not s.isascii():
            if s[0] == "\N{MICRO SIGN}":
                s = "u" + s[1:]
            if s[-1] in cls._prefixable_unit_symbols:
                s = s[:-1] + cls._prefixable_unit_symbols[s[-1]]
            elif len(s) > 1 and s[-1] in cls._unit_suffix_symbols:
                s = s[:-1] + cls._unit_suffix_symbols[s[-1]]
            elif s.endswith("R\N{INFINITY}"):
                s = s[:-2] + "Ry"

        if s in registry:
            return registry[s]

        if detailed_exception:
            raise ValueError(f"{s} is not a valid unit. {did_you_mean(s, registry)}")
        else:
            raise ValueError()

    _unit_symbols = {
        "%": "percent",
        "\N{PRIME}": "arcmin",
        "\N{DOUBLE PRIME}": "arcsec",
        "\N{MODIFIER LETTER SMALL H}": "hourangle",
        "e\N{SUPERSCRIPT MINUS}": "electron",
    }

    _prefixable_unit_symbols = {
        "\N{GREEK CAPITAL LETTER OMEGA}": "Ohm",
        "\N{LATIN CAPITAL LETTER A WITH RING ABOVE}": "Angstrom",
        "\N{SCRIPT SMALL L}": "l",
    }

    _unit_suffix_symbols = {
        "\N{CIRCLED DOT OPERATOR}": "sun",
        "\N{SUN}": "sun",
        "\N{CIRCLED PLUS}": "earth",
        "\N{EARTH}": "earth",
        "\N{JUPITER}": "jupiter",
        "\N{LATIN SUBSCRIPT SMALL LETTER E}": "_e",
        "\N{LATIN SUBSCRIPT SMALL LETTER P}": "_p",
    }

    _translations = str.maketrans(
        {
            "\N{GREEK SMALL LETTER MU}": "\N{MICRO SIGN}",
            "\N{MINUS SIGN}": "-",
        }
    )
    """Character translations that should be applied before parsing a string.

    Note that this does explicitly *not* generally translate MICRO SIGN to u,
    since then a string like 'µ' would be interpreted as unit mass.
    """

    _superscripts = (
        "\N{SUPERSCRIPT MINUS}"
        "\N{SUPERSCRIPT PLUS SIGN}"
        "\N{SUPERSCRIPT ZERO}"
        "\N{SUPERSCRIPT ONE}"
        "\N{SUPERSCRIPT TWO}"
        "\N{SUPERSCRIPT THREE}"
        "\N{SUPERSCRIPT FOUR}"
        "\N{SUPERSCRIPT FIVE}"
        "\N{SUPERSCRIPT SIX}"
        "\N{SUPERSCRIPT SEVEN}"
        "\N{SUPERSCRIPT EIGHT}"
        "\N{SUPERSCRIPT NINE}"
    )

    _superscript_translations = str.maketrans(_superscripts, "-+0123456789")
    _regex_superscript = re.compile(f"[{_superscripts}]?[{_superscripts[2:]}]+")
    _regex_deg = re.compile("°([CF])?")

    @classmethod
    def _convert_superscript(cls, m):
        return f"({m.group().translate(cls._superscript_translations)})"

    @classmethod
    def _convert_deg(cls, m):
        if len(m.string) == 1:
            return "deg"
        return m.string.replace("°", "deg_")

    @classmethod
    def parse(cls, s, debug=False):
        if not isinstance(s, str):
            s = s.decode("ascii")
        elif not s.isascii():
            # common normalization of unicode strings to avoid
            # having to deal with multiple representations of
            # the same character. This normalizes to "composed" form
            # and will e.g. convert OHM SIGN to GREEK CAPITAL LETTER OMEGA
            s = unicodedata.normalize("NFC", s)
            # Translate some basic unicode items that we'd like to support on
            # input but are not standard.
            s = s.translate(cls._translations)

            # TODO: might the below be better done in the parser/lexer?
            # Translate superscripts to parenthesized numbers; this ensures
            # that mixes of superscripts and regular numbers fail.
            s = cls._regex_superscript.sub(cls._convert_superscript, s)
            # Translate possible degrees.
            s = cls._regex_deg.sub(cls._convert_deg, s)

        result = cls._do_parse(s, debug=debug)
        # Check for excess solidi, but exclude fractional exponents (accepted)
        n_slashes = s.count("/")
        if n_slashes > 1 and (n_slashes - len(re.findall(r"\(\d+/\d+\)", s))) > 1:
            warnings.warn(
                f"'{s}' contains multiple slashes, which is "
                "discouraged by the FITS standard",
                core.UnitsWarning,
            )
        return result

    @classmethod
    def _do_parse(cls, s, debug=False):
        try:
            # This is a short circuit for the case where the string
            # is just a single unit name
            return cls._parse_unit(s, detailed_exception=False)
        except ValueError as e:
            try:
                return cls._parser.parse(s, lexer=cls._lexer, debug=debug)
            except ValueError as e:
                if str(e):
                    raise
                else:
                    raise ValueError(f"Syntax error parsing unit '{s}'")


# 2023-02-18: The statement in the docstring is no longer true, the class is not used
# anywhere so can be safely removed in 6.0.
@deprecated("5.3", alternative="Generic")
class Unscaled(Generic):
    """
    A format that doesn't display the scale part of the unit, other
    than that, it is identical to the `Generic` format.

    This is used in some error messages where the scale is irrelevant.
    """

    @classmethod
    def to_string(cls, unit):
        if unit.scale != 1:
            unit = core.Unit(unit / unit.scale)
        return super().to_string(unit)
