"""Compute modes of a rectangular Si strip waveguide on top of oxide.
Note that you should only pay attention, here, to the guided modes,
which are the modes whose frequency falls under the light line --
that is, frequency < beta / 1.45, where 1.45 is the SiO2 index.

Since there's no special lengthscale here, you can just
use microns. In general, if you use units of x, the frequencies
output are equivalent to x/lambda# so here, the frequencies will be
output as um/lambda, e.g. 1.5um would correspond to the frequency
1/1.5 = 0.6667.

"""
import pathlib
import pickle
from functools import partial
from typing import Dict, Optional

import meep as mp
import numpy as np
from meep import mpb

from gdsfactory.config import CONFIG
from gdsfactory.simulation.get_sparameters_path import get_kwargs_hash
from gdsfactory.simulation.modes.disable_print import disable_print, enable_print
from gdsfactory.simulation.modes.get_mode_solver_coupler import get_mode_solver_coupler
from gdsfactory.simulation.modes.get_mode_solver_rib import get_mode_solver_rib
from gdsfactory.simulation.modes.types import Mode
from gdsfactory.types import PathType

mpb.Verbosity(0)


def find_modes_waveguide(
    tol: float = 1e-6,
    wavelength: float = 1.55,
    mode_number: int = 1,
    parity=mp.NO_PARITY,
    cache: Optional[PathType] = CONFIG["modes"],
    overwrite: bool = False,
    single_waveguide: bool = True,
    **kwargs,
) -> Dict[int, Mode]:
    """Computes mode effective and group index for a rectangular waveguide.

    single_waveguide=True

    ::

          __________________________
          |
          |
          |         width
          |     <---------->
          |      ___________   _ _ _
          |     |           |       |
        sz|_____|  ncore    |_______|
          |                         | wg_thickness
          |slab_thickness    nslab  |
          |_________________________|
          |
          |        nclad
          |__________________________
          <------------------------>
                        sy

    single_waveguide=False

    ::

          _____________________________________________________
          |
          |
          |         widths[0]                 widths[1]
          |     <---------->     gaps[0]    <---------->
          |      ___________ <-------------> ___________      _
          |     |           |               |           |     |
        sz|_____|  ncore    |_______________|           |_____|
          |                                                   | wg_thickness
          |slab_thickness        nslab                        |
          |___________________________________________________|
          |
          |<--->                                         <--->
          |ymargin               nclad                   ymargin
          |____________________________________________________
          <--------------------------------------------------->
                                   sy

    Args:
        mode_solver: function that returns mpb.ModeSolver
        tol: tolerance when finding modes
        wavelength: wavelength in um.
        mode_number: mode order of the first mode
        parity: mp.ODD_Y mp.EVEN_X for TE, mp.EVEN_Y for TM.
        cache: directory path to cache modes. None disables the file cache.
        overwrite: forces
        kwargs: waveguide settings.

    Keyword Args:
        wg_width: wg_width (um)
        wg_thickness: wg height (um)
        slab_thickness: thickness for the waveguide slab
        ncore: core material refractive index
        nclad: clad material refractive index
        sy: simulation region width (um)
        sz: simulation region height (um)
        resolution: resolution (pixels/um)
        nmodes: number of modes to compute.

    Keyword Args:
        wg_width: wg_width (um) for the symmetric case.
        gap: for the case of only two waveguides.
        wg_widths: list or tuple of waveguide widths.
        gaps: list or tuple of waveguide gaps.
        wg_thickness: wg height (um)
        slab_thickness: thickness for the waveguide slab
        ncore: core material refractive index
        nclad: clad material refractive index
        nslab: Optional slab material refractive index. Defaults to ncore.
        ymargin: margin in y.
        sz: simulation region thickness (um)
        resolution: resolution (pixels/um)
        nmodes: number of modes
        sidewall_angles: waveguide sidewall angle (radians),
            tapers from wg_width at top of slab, upwards, to top of waveguide

    Returns: Dict[mode_number, Mode]

    compute mode_number lowest frequencies as a function of k. Also display
    "parities", i.e. whether the mode is symmetric or anti_symmetric
    through the y=0 and z=0 planes.
    mode_solver.run(mpb.display_yparities, mpb.display_zparities)

    Above, we outputed the dispersion relation: frequency (omega) as a
    function of wavevector kx (beta). Alternatively, you can compute
    beta for a given omega -- for example, you might want to find the
    modes and wavevectors at a fixed wavelength of 1.55 microns. You
    can do that using the find_k function:
    """
    modes = {}
    mode_solver = (
        get_mode_solver_rib(**kwargs)
        if single_waveguide
        else get_mode_solver_coupler(**kwargs)
    )
    nmodes = mode_solver.nmodes
    omega = 1 / wavelength

    h = get_kwargs_hash(
        wavelength=wavelength,
        parity=parity,
        single_waveguide=single_waveguide,
        **kwargs,
    )

    if cache:
        cache = pathlib.Path(cache)
        cache.mkdir(exist_ok=True, parents=True)
        filepath = cache / f"{h}_{mode_number}.pkl"

        if filepath.exists() and not overwrite:
            for index, i in enumerate(range(mode_number, mode_number + nmodes)):
                filepath = cache / f"{h}_{index}.pkl"
                mode = pickle.loads(filepath.read_bytes())
                modes[i] = mode
            return modes

    # Output the x component of the Poynting vector for mode_number bands at omega
    disable_print()
    k = mode_solver.find_k(
        parity,