import logging
from contextlib import contextmanager

import picamerax
from flask import abort
from labthings import find_component
from labthings.extensions import BaseExtension
from labthings.views import ActionView

from openflexure_microscope.camera.base import BaseCamera
from openflexure_microscope.microscope import Microscope

from .recalibrate_utils import (
    auto_expose_and_freeze_settings,
    flat_lens_shading_table,
    recalibrate_camera,
)


@contextmanager
def pause_stream(scamera: BaseCamera):
    """This context manager locks a streaming camera, and pauses the stream.

    The stream is re-enabled, with the original resolution, once the with
    block has finished.
    """
    with scamera.lock:
        assert (
            not scamera.record_active
        ), "We can't pause the camera's video stream while a recording is in progress."
        streaming = scamera.stream_active
        old_resolution = scamera.stream_resolution
        if streaming:
            logging.info("Stopping stream in pause_stream context manager")
            scamera.stop_stream()
        try:
            yield scamera
        finally:
            scamera.stream_resolution = old_resolution
            if streaming:
                logging.info("Restarting stream in pause_stream context manager")
                scamera.start_stream()


def recalibrate(microscope: Microscope):
    """Reset the camera's settings.

    This generates new gains, exposure time, and lens shading
    table such that the background is as uniform as possible
    with a gray level of 230.  It takes a little while to run.
    """
    with pause_stream(microscope.camera) as scamera:
        if hasattr(scamera, "picamera"):
            picamera_obj: picamerax.PiCamera = getattr(scamera, "picamera")
            auto_expose_and_freeze_settings(picamera_obj)
            recalibrate_camera(picamera_obj)
            microscope.save_settings()
        else:
            raise RuntimeError(
                "Recalibrate can only be used with a Raspberry Pi camera"
            )


class RecalibrateView(ActionView):
    def post(self):
        microscope = find_component("org.openflexure.microscope")

        if not microscope:
            abort(503, "No microscope connected. Unable to recalibrate.")

        logging.info("Starting microscope recalibration...")

        return recalibrate(microscope)


class FlattenLSTView(ActionView):
    def post(self):
        microscope = find_component("org.openflexure.microscope")

        if not microscope:
            abort(
                503,
                "No microscope connected. Unable to flatten the lens shading table.",
            )

        with pause_stream(microscope.camera) as scamera:
            flat_lst = flat_lens_shading_table(scamera.camera)
            scamera.camera.lens_shading_table = flat_lst
        microscope.save_settings()


class DeleteLSTView(ActionView):
    def post(self):
        microscope = find_component("org.openflexure.microscope")

        if not microscope:
            abort(
                503,
                "No microscope connected. Unable to flatten the lens shading table.",
            )

        with pause_stream(microscope.camera) as scamera:
            scamera.camera.lens_shading_table = None
        microscope.save_settings()


lst_extension_v2 = BaseExtension(
    "org.openflexure.calibration.picamera",
    version="2.0.0-beta.1",
    description="Routines to perform flat-field correction on the camera.",
)

lst_extension_v2.add_method(
    recalibrate, "org.openflexure.calibration.picamera.recalibrate"
)

lst_extension_v2.add_view(RecalibrateView, "/recalibrate", endpoint="recalibrate")
lst_extension_v2.add_view(
    FlattenLSTView, "/flatten_lens_shading_table", endpoint="flatten_lens_shading_table"
)
lst_extension_v2.add_view(
    DeleteLSTView, "/delete_lens_shading_table", endpoint="delete_lens_shading_table"
)