import datetime
import re
from glob import glob
from os.path import join, dirname
from warnings import warn

import pandas as pd
from astropy import units as u
from astropy.coordinates import EarthLocation
from astropy.time import Time
from numpy import nan

from kis_tools.gris.headers.exceptions import NothingToDoError
from kis_tools.gris.headers.template_builder import gris_const_trans, gris_triv_trans, TRANS_SETTINGS, fitpar_kws
from kis_tools.gris.headers.translator import cache_translation, MetadataTranslator
from kis_tools.gris.util import get_observers
from kis_tools.util.calculations import get_distance_gregor_sun
from kis_tools.util.constants import gregor_coords
from kis_tools.util.util import gris_obs_mode, date_from_fn, gris_run_number


class FitsTranslator(MetadataTranslator):
    """Metadata translator for FITS standard headers.

    Understands:

    - DATE-OBS
    - INSTRUME
    - TELESCOP
    - OBSGEO-[X,Y,Z]

    """

    _wcs_kw_patterns = [
        r"CTYPE\d+",
        r"CUNIT\d+",
        r"CRPIX\d+",
        r"CRVAL\d+",
        r"CSYER\d+",
        r"CDELT\d+",
        r"PC\d+_\d+",
    ]

    @classmethod
    def can_translate(cls, header, filename=None):
        """Indicate whether this translation class can translate the
        supplied header.

        Checks the instrument value and compares with the supported
        instruments in the class

        Parameters
        ----------
        header : `dict`-like
            Header to convert to standardized form.
        filename : `str`, optional
            Name of file being translated.

        Returns
        -------
        can : `bool`
            `True` if the header is recognized by this class. `False`
            otherwise.
        """
        if cls.supported_instrument is None:
            return False

        # Protect against being able to always find a standard
        # header for instrument
        try:
            translator = cls(header, filename=filename)
            instrument = translator.to_instrument()
        except KeyError:
            return False

        return instrument == cls.supported_instrument

    @classmethod
    def _from_fits_date_string(cls, date_str, scale="utc", time_str=None):
        """Parse standard FITS ISO-style date string and return time object

        Parameters
        ----------
        date_str : `str`
            FITS format date string to convert to standard form. Bypasses
            lookup in the header.
        scale : `str`, optional
            Override the time scale from the TIMESYS header. Defaults to
            UTC.
        time_str : `str`, optional
            If provided, overrides any time component in the ``dateStr``,
            retaining the YYYY-MM-DD component and appending this time
            string, assumed to be of format HH:MM::SS.ss.

        Returns
        -------
        date : `astropy.time.Time`
            `~astropy.time.Time` representation of the date.
        """
        if time_str is not None:
            date_str = "{}T{}".format(date_str[:10], time_str)

        return Time(date_str, format="isot", scale=scale)

    def _from_fits_date(self, date_key):
        """Calculate a date object from the named FITS header

        Uses the TIMESYS header if present to determine the time scale,
        defaulting to UTC.

        Parameters
        ----------
        dateKey : `str`
            The key in the header representing a standard FITS
            ISO-style date.

        Returns
        -------
        date : `astropy.time.Time`
            `~astropy.time.Time` representation of the date.
        """
        used = [date_key]
        if "TIMESYS" in self._header:
            scale = self._header["TIMESYS"].lower()
            used.append("TIMESYS")
        else:
            scale = "utc"
        if date_key in self._header:
            date_str = self._header[date_key]
            value = self._from_fits_date_string(date_str, scale=scale)
            self._used_these_cards(*used)
        else:
            value = None
        return value

    @cache_translation
    def to_datetime_begin(self):
        """Calculate start time of observation.

        Uses FITS standard ``DATE-OBS`` and ``TIMESYS`` headers.

        Returns
        -------
        start_time : `astropy.time.Time`
            Time corresponding to the start of the observation.
        """
        return self._from_fits_date("DATE-OBS")

    @cache_translation
    def to_datetime_end(self):
        """Calculate end time of observation.

        Uses FITS standard ``DATE-END`` and ``TIMESYS`` headers.

        Returns
        -------
        start_time : `astropy.time.Time`
            Time corresponding to the end of the observation.
        """
        return self._from_fits_date("DATE-END")

    @cache_translation
    def to_location(self):
        """Calculate the observatory location.

        Uses FITS standard ``OBSGEO-`` headers.

        Returns
        -------
        location : `astropy.coordinates.EarthLocation`
            An object representing the location of the telescope.
        """
        cards = [f"OBSGEO-{c}" for c in ("X", "Y", "Z")]
        coords = [self._header[c] for c in cards]
        value = EarthLocation.from_geocentric(*coords, unit=u.m)
        self._used_these_cards(*cards)
        return value

    def from_default(self, kw, default):
        """Generate a translation method which keeps the value of a given Keyword and fills a default if no
        value is given"""

        def check_or_default():
            if kw in self._header.keys():
                return self._header[kw]
            else:
                return default

        setattr(self, f"to_{kw}", check_or_default)

    def from_float_or_nan(self, kw):
        """Generate a translation method which tries to convert a given Keyword to float and fills a NaN if no
        value is given"""

        def try_float_else_nan():
            val = self._header[kw]
            try:
                val = float(val)
                return val
            except ValueError:
                return nan
            except TypeError:
                return nan

        setattr(self, f"to_{kw}", try_float_else_nan)

    def add_wcs_methods(self):
        h = self._header
        patterns = self._wcs_kw_patterns

        for p in patterns:
            pattern = re.compile(p)
            kws = filter(pattern.match, h.keys())
            for k in kws:
                def constant_translator():
                    return h[k]

                self.from_default(k, h[k])

        pass

    @property
    def wcs_cards(self):
        """Retrieve WCS-related cards from header. Cards are Identified by matching with the wcs_patterns property
        Returns:
            cards: list of header cards
        """
        h = self._header
        patterns = self._wcs_kw_patterns
        cards = [
            c
            for c in h._cards
            if any([re.search(pattern, c.keyword) for pattern in patterns])
        ]

        return cards


class KISTranslator(FitsTranslator):
    """Translator class for building KIS headers. It is intended to be used as a base class for all
    telescope-specific translators."""

    def _to_ORIGIN(self):
        return self.default_if_empty(
            "ORIGIN", "Leibniz Insitute for Solar Physics (KIS)"
        )


class GREGORTranslator(KISTranslator):
    """Translator class for building GREGOR headers. It is intended to be used as a base class for all
    instrument-specific translators."""

    def to_TELESCOP(self):
        return self.default_if_empty("TELESCOP", "GREGOR")

    def to_OBSRVTRY(self):
        return self.default_if_empty("OBSRVTRY", "Teide Obseratory")

    def __init__(self, *args, **kwargs):
        self._coords = gregor_coords.to_geocentric()
        super().__init__(*args, **kwargs)

    def to_OBSGEO_X(self):
        return self._coords[0].value

    def to_OBSGEO_Y(self):
        return self._coords[1].value

    def to_OBSGEO_Z(self):
        return self._coords[2].value


class GrisTranslator(GREGORTranslator):
    """Translate Gris Headers"""

    name = "Gris"
    supported_instrument = "Gris"

    @classmethod
    def can_translate(cls, header, filename=None):
        """Indicate whether this translation class can translate the
        supplied header.

        Parameters
        ----------
        header : `dict`-like
            Header to convert to standardized form.
        filename : `str`, optional
            Name of file being translated.

        Returns
        -------
        can : `bool`
            `True` if the header is recognized by this class. `False`
            otherwise.
        """
        if "SOLARNET" in header:
            raise NothingToDoError("This header is already up to date!")

        if "TELESCOP" in header:
            is_gregor = header["TELESCOP"] == "GREGOR"
            if is_gregor and all([key in header.keys() for key in ["FF1WLOFF"]]):
                return True
            else:
                warn(
                    "GrisTranslator: got a file which does not contain FTS-fitting results or has not been split."
                    "This translator needs a split file created with recent routines as input."
                )

        return False

    _const_map = gris_const_trans

    _trivial_map = gris_triv_trans

    @cache_translation
    def to_observation_id(self):
        """ observation id is given by DAY_RUN"""
        date = self._from_fits_date_string(self._header["DATE-OBS"]).strftime("%Y%m%d")
        iobs = int(self._header["IOBS"])
        value = f"{date}_{iobs:03d}"
        return value

    def to_EXTNAME(self):
        """EXTNAME as hdu for a given combination of day, run,
        map,slitposition"""
        iserie = int(self._header["ISERIE"])
        istep = int(self._header["ISTEP"])
        value = self.to_observation_id()
        value += f"_{iserie:03d}_{istep:04d}"
        return value

    def to_POINT_ID(self):
        """Assume that telescope is re-pointed for each run"""
        return self.to_observation_id()

    @staticmethod
    def to_DATE():
        """Date of FITS creation"""
        return datetime.date.today()

    @cache_translation
    def to_DSUN_OBS(self):
        """Distance between instrument and sun center"""
        return get_distance_gregor_sun(self.to_DATE_BEG())

    @cache_translation
    def to_DATE_BEG(self):
        """Calculate start time of observation.

        Uses FITS standard ``DATE-OBS``

        Returns
        -------
        time : datetime.datetime
            Time corresponding to the start of the observation.
        """
        ut = self._header["UT"]
        do = self._header["DATE-OBS"]
        string = do + " " + ut.strip()
        time = datetime.datetime.strptime(string, "%Y-%m-%d %H:%M:%S.%f")
        return time

    def to_DATE_OBS(self):
        """Added for compatibility, set to beginnning of observation

        Returns
        -------
        time : datetime.datetime
            Time corresponding to the start of the observation.
        """
        time = self.to_DATE_BEG()
        return time

    @cache_translation
    def to_AWAVLNTH(self):
        """Get approximate wavelength in air"""
        wl = int(self._header["WAVELENG"])
        if wl == 1564:
            wl = 1565
        return wl * 10

    @cache_translation
    def to_AWAVMIN(self):
        """Minimum wavelength is calculated from the wavelength offset
        determined by the FTS fit, average if two flats are given"""
        ff1 = self._header["FF1WLOFF"]
        ff2 = self._header["FF2WLOFF"]
        try:
            value = (ff1 + ff2) / 2
        except TypeError:
            value = ff1
        return value

    @cache_translation
    def to_AWAVMAX(self):
        """Maximum wavelength is calculated from the wavelength offset
        determined by the FTS fit plus the number of pixels along the
        wavelength axis times the dispersion. average if two flats are
        given"""

        ff1 = self._header["FF1WLDSP"]
        ff2 = self._header["FF2WLDSP"]
        nsteps = self._header["NAXIS1"] - 1
        try:
            dispersion = (ff1 + ff2) / 2
        except TypeError:
            dispersion = ff1
        value = dispersion * nsteps + self.to_AWAVMIN()
        return value

    @cache_translation
    def to_OBS_MODE(self):
        """Observation mode is determined by the number of observed
        states,the stepping settings and the number of observed
        maps."""
        n_maps = self.to_NMAPS()
        n_steps = self.to_NSTEPS()
        step_size = self._header["STEPSIZE"]
        naxis = self._header["NAXIS"]
        if naxis == 2:
            states = 1
        else:
            states = self._header[f"NAXIS{naxis}"]
        mode_string = gris_obs_mode(states, n_maps, n_steps, step_size)

        return mode_string

    def to_TEXPOSUR(self):
        """Implemented for Solarsoft compatibility in seconds"""
        return self._header["EXPTIME"] / 1000

    @cache_translation
    def to_XPOSURE(self):
        """Exposure time for the entire file in seconds"""
        n_accumulations = self.to_NSUMEXP()
        exptime = self.to_TEXPOSUR()
        return exptime * n_accumulations

    def to_EXPTIME(self):
        """Implemented for Solarsoft compatibility in seconds"""
        return self.to_XPOSURE()

    @cache_translation
    def to_OBSERVER(self):
        """Observer"""
        logfiles = glob(join(dirname(dirname(self.filename)), "????????.txt"))
        if not logfiles:
            return "Unknown"
        logfile = logfiles[0]
        observers = get_observers(logfile)
        to_header = []
        sep = ", "
        for o in observers:
            length = sum([len(th) for th in to_header]) + (len(to_header) - 1) * len(
                sep
            )
            if length + len(o) + len(sep) < 70:
                to_header.append(o)
            else:
                break
        res = sep.join(to_header)
        assert len(res) < 70
        return res

    @cache_translation
    def to_AO_LOCK(self):
        """Adaptive optics locking"""
        state = self._header["AOSTATE"].strip()
        if state == "on":
            return 1.0
        elif state == "off":
            return 0.0
        else:
            return nan

    def to_OBS_TRGT(self):
        """Parsed from tagging file, if not in tagging file, check
        header for tag, else default to not_tagged"""
        fn = self._header["FILENAME"]
        date = date_from_fn(fn).strftime("%Y-%m-%d")
        run = gris_run_number(fn)
        try:
            return self.tags.at[(date, run), "main_tag"]
        except KeyError:
            if "TARGET" in self._header:
                return self._header["TARGET"]
            else:
                return "not tagged"

    def get_fitpars(self, fitpar_kw):
        """Generate a dictionary of keywords for the parameters of the
        Polynomial determined by the FTS fit. The dictionary is later
        expanded to single keywords."""

        def get_all_parameters():
            npoly_key = fitpar_kw[:3] + "NPOLY"
            try:
                npoly = int(self._header[npoly_key])
            except ValueError:
                return {fitpar_kw: None}
            except TypeError:
                return {fitpar_kw: None}
            vals = {}
            for i in range(npoly + 1):
                par_key = fitpar_kw.replace("nn", f"{i:02d}")
                try:
                    vals[par_key] = self._header[par_key]
                except KeyError:
                    message = f"Warning: could not find '{par_key}' in header."
                    message += (
                        " Check that the correct number of parameters has entered "
                    )
                    message += "the header and re-run calibration if necessary!"
                    warn(message)

            return vals

        setattr(self, f"to_{fitpar_kw}", get_all_parameters)

    def __init__(self, *args, **kwargs):
        """Parse tag_file, set up translations for keywords with
        default value, setup fit result keywords"""
        super(GrisTranslator, self).__init__(*args, **kwargs)

        self.tags = pd.read_csv(
            TRANS_SETTINGS["tag_file"],
            parse_dates=["date"],
            index_col=["date", "run"],
        )

        self.from_default("ROTCODE", -1)
        self.from_default("ROTTRACK", None)
        self.from_default("IMGSYS", "SLIT")
        self.from_default("SLITCNTR", "scancntr")
        self.from_default("ROTANGLE", 0)
        self.from_default("BSCALE", 1)
        self.from_default("BZERO", 0)

        fit_results = ["WLOFF", "WLDSP", "FWHMA", "FWHMP", "STRAY", "NPOLY"]
        for fit_res in fit_results:
            for i_flat in [1, 2]:
                kw = f"FF{i_flat}{fit_res}"
                self.from_float_or_nan(kw)

        # add fit res parameters
        for fitpar_kw in fitpar_kws:
            self.get_fitpars(fitpar_kw)