# Licensed under a 3-clause BSD style license - see LICNSE.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 the CDS string format for units."""

import re
from typing import ClassVar, Literal

from astropy.extern.ply.lex import Lexer
from astropy.units.core import CompositeUnit, Unit, UnitBase
from astropy.units.enums import DeprecatedUnitAction
from astropy.units.utils import is_effectively_unity
from astropy.utils import classproperty, parsing
from astropy.utils.parsing import ThreadSafeParser

from .base import Base, _ParsingFormatMixin


class CDS(Base, _ParsingFormatMixin):
    """
    Support the `Centre de Données astronomiques de Strasbourg
    <https://cds.unistra.fr/>`_ `Standards for Astronomical
    Catalogues 2.0 <https://vizier.unistra.fr/vizier/doc/catstd-3.2.htx>`_
    format, and the `complete set of supported units
    <https://vizier.unistra.fr/viz-bin/Unit>`_.  This format is used
    by VOTable up to version 1.2.
    """

    _space: ClassVar[str] = "."
    _times: ClassVar[str] = "x"
    _scale_unit_separator: ClassVar[str] = ""

    _tokens: ClassVar[tuple[str, ...]] = (
        "PRODUCT",
        "DIVISION",
        "OPEN_PAREN",
        "CLOSE_PAREN",
        "OPEN_BRACKET",
        "CLOSE_BRACKET",
        "X",
        "INT",
        "FLOAT",
        "UNIT",
        "DIMENSIONLESS",
    )

    @classproperty(lazy=True)
    def _units(cls) -> dict[str, UnitBase]:
        from astropy import units as u
        from astropy.units import cds

        return {k: v for k, v in cds.__dict__.items() if isinstance(v, u.UnitBase)}

    @classproperty(lazy=True)
    def _lexer(cls) -> Lexer:
        tokens = cls._tokens

        t_PRODUCT = r"\."
        t_DIVISION = r"/"
        t_OPEN_PAREN = r"\("
        t_CLOSE_PAREN = r"\)"
        t_OPEN_BRACKET = r"\["
        t_CLOSE_BRACKET = r"\]"

        # NOTE THE ORDERING OF THESE RULES IS IMPORTANT!!
        # Regular expression rules for simple tokens

        def t_FLOAT(t):
            r"[+-]?((\d+\.?\d+)|(\.\d+))([eE][+-]?\d+)?"
            if not re.search(r"[eE\.]", t.value):
                t.type = "INT"
                t.value = int(t.value)
            else:
                t.value = float(t.value)
            return t

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

        def t_X(t):  # multiplication for factor in front of unit
            r"[x×]"
            return t

        # Most units are just combinations of letters with no numbers, but there
        # are a few special ones (\h is Planch constant) and three that end in 0.
        def t_UNIT(t):
            r"%|°|\\h|(a|eps|mu)0|((?!\d)\w)+"
            t.value = cls._get_unit(t)
            return t

        def t_DIMENSIONLESS(t):
            r"---|-"
            # These are separate from t_UNIT since they cannot have a prefactor.
            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="cds_lextab", package="astropy/units", reflags=int(re.UNICODE)
        )

    @classproperty(lazy=True)
    def _parser(cls) -> ThreadSafeParser:
        """
        The grammar here is based on the description in the `Standards
        for Astronomical Catalogues 2.0
        <https://vizier.unistra.fr/vizier/doc/catstd-3.2.htx>`_, which is not
        terribly precise.  The exact grammar is here is based on the
        YACC grammar in the `unity library <https://purl.org/nxg/dist/unity/>`_.
        """
        tokens = cls._tokens

        def p_main(p):
            """
            main : factor combined_units
                 | combined_units
                 | DIMENSIONLESS
                 | OPEN_BRACKET combined_units CLOSE_BRACKET
                 | OPEN_BRACKET DIMENSIONLESS CLOSE_BRACKET
                 | factor
            """
            from astropy.units import dex

            if len(p) == 3:
                p[0] = CompositeUnit(p[1] * p[2].scale, p[2].bases, p[2].powers)
            elif len(p) == 4:
                p[0] = dex(p[2])
            else:
                p[0] = Unit(p[1])

        def p_combined_units(p):
            """
            combined_units : product_of_units
                           | division_of_units
            """
            p[0] = p[1]

        def p_product_of_units(p):
            """
            product_of_units : unit_expression PRODUCT combined_units
                             | unit_expression
            """
            if len(p) == 4:
                p[0] = p[1] * p[3]
            else:
                p[0] = p[1]

        def p_division_of_units(p):
            """
            division_of_units : DIVISION unit_expression
                              | combined_units DIVISION unit_expression
            """
            if len(p) == 3:
                p[0] = p[2] ** -1
            else:
                p[0] = p[1] / p[3]

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

        def p_factor(p):
            """
            factor : FLOAT X INT INT
                   | INT X INT INT
                   | INT INT
                   | INT
                   | FLOAT
            """
            match p[1:]:
                case factor, _, 10, exponent:
                    p[0] = factor * 10.0**exponent
                case _, _, _, _:
                    raise ValueError("Only base ten exponents are allowed in CDS")
                case 10, exponent:
                    p[0] = 10.0**exponent
                case _, _:
                    raise ValueError("Only base ten exponents are allowed in CDS")
                case _:
                    p[0] = p[1]

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

        def p_error(p):
            raise ValueError()

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

    @classmethod
    def parse(cls, s: str, debug: bool = False) -> UnitBase:
        if " " in s:
            raise ValueError("CDS unit must not contain whitespace")
        if not isinstance(s, str):
            s = s.decode("ascii")

        return cls._do_parse(s, debug)

    @classmethod
    def _format_mantissa(cls, m: str) -> str:
        return "" if m == "1" else m

    @classmethod
    def _format_superscript(cls, number: str) -> str:
        return number if number.startswith("-") else "+" + number

    @classmethod
    def to_string(
        cls,
        unit: UnitBase,
        fraction: bool | Literal["inline", "multiline"] = False,
        deprecations: DeprecatedUnitAction = DeprecatedUnitAction.WARN,
    ) -> str:
        # Remove units that aren't known to the format
        unit = cls._decompose_to_known_units(unit)

        if not unit.bases:
            if unit.scale == 1:
                return "---"
            elif is_effectively_unity(unit.scale * 100.0):
                return "%"

        return super().to_string(unit, fraction=fraction)
