"""
Basic image exploration and fitting
===================================

Detect sources, produce a sky image and a spectrum using CTA-1DC data.

Introduction
------------

**This notebook shows an example how to make a sky image and spectrum
for simulated CTAO data with Gammapy.**

The dataset we will use is three observation runs on the Galactic
Center. This is a tiny (and thus quick to process and play with and
learn) subset of the simulated CTAO dataset that was produced for the
first data challenge in August 2017.

"""

######################################################################
# Setup
# -----
#
# As usual, we’ll start with some setup …
#

# Configure the logger, so that the spectral analysis
# isn't so chatty about what it's doing.
import logging
import astropy.units as u
from astropy.coordinates import SkyCoord
from regions import CircleSkyRegion
import matplotlib.pyplot as plt
from IPython.display import display
from gammapy.data import DataStore
from gammapy.datasets import Datasets, FluxPointsDataset, MapDataset, SpectrumDataset
from gammapy.estimators import FluxPointsEstimator, TSMapEstimator
from gammapy.estimators.utils import find_peaks
from gammapy.makers import (
    MapDatasetMaker,
    ReflectedRegionsBackgroundMaker,
    SafeMaskMaker,
    SpectrumDatasetMaker,
)
from gammapy.maps import MapAxis, RegionGeom, WcsGeom
from gammapy.modeling import Fit
from gammapy.modeling.models import (
    GaussianSpatialModel,
    PowerLawSpectralModel,
    SkyModel,
)
from gammapy.visualization import plot_npred_signal, plot_spectrum_datasets_off_regions

logging.basicConfig()
log = logging.getLogger("gammapy.spectrum")
log.setLevel(logging.ERROR)

######################################################################
# Select observations
# -------------------
#
# A Gammapy analysis usually starts by creating a
# `~gammapy.data.DataStore` and selecting observations.
#
# This is shown in detail in other notebooks (see e.g. the :doc:`/tutorials/starting/analysis_2` tutorial),
# here we choose three observations near the Galactic Center.
#

data_store = DataStore.from_dir("$GAMMAPY_DATA/cta-1dc/index/gps")

# Just as a reminder: this is how to select observations
# from astropy.coordinates import SkyCoord
# table = data_store.obs_table
# pos_obs = SkyCoord(table['GLON_PNT'], table['GLAT_PNT'], frame='galactic', unit='deg')
# pos_target = SkyCoord(0, 0, frame='galactic', unit='deg')
# offset = pos_target.separation(pos_obs).deg
# mask = (1 < offset) & (offset < 2)
# table = table[mask]
# table.show_in_browser(jsviewer=True)

obs_id = [110380, 111140, 111159]
observations = data_store.get_observations(obs_id)

obs_cols = ["OBS_ID", "GLON_PNT", "GLAT_PNT", "LIVETIME"]
display(data_store.obs_table.select_obs_id(obs_id)[obs_cols])


######################################################################
# Make sky images
# ---------------
#
# Define map geometry
# ~~~~~~~~~~~~~~~~~~~
#
# Select the target position and define an ON region for the spectral
# analysis
#

axis = MapAxis.from_energy_bounds(
    0.1,
    10,
    nbin=10,
    unit="TeV",
    name="energy",
)
axis_true = MapAxis.from_energy_bounds(
    0.05,
    20,
    nbin=20,
    name="energy_true",
    unit="TeV",
)
geom = WcsGeom.create(
    skydir=(0, 0), npix=(500, 400), binsz=0.02, frame="galactic", axes=[axis]
)
print(geom)


######################################################################
# Compute images
# ~~~~~~~~~~~~~~
#

stacked = MapDataset.create(geom=geom, energy_axis_true=axis_true)
maker = MapDatasetMaker(selection=["counts", "background", "exposure", "psf"])
maker_safe_mask = SafeMaskMaker(methods=["offset-max"], offset_max=2.5 * u.deg)

for obs in observations:
    cutout = stacked.cutout(obs.get_pointing_icrs(obs.tmid), width="5 deg")
    dataset = maker.run(cutout, obs)
    dataset = maker_safe_mask.run(dataset, obs)
    stacked.stack(dataset)

# %%
#
# The maps are cubes, with an energy axis.
# Let's also make some images:
#

dataset_image = stacked.to_image()
geom_image = dataset_image.geoms["geom"]

######################################################################
# Show images
# ~~~~~~~~~~~
#
# Let’s have a quick look at the images we computed …
#

fig, (ax1, ax2, ax3) = plt.subplots(
    figsize=(15, 5),
    ncols=3,
    subplot_kw={"projection": geom_image.wcs},
    gridspec_kw={"left": 0.1, "right": 0.9},
)

ax1.set_title("Counts map")
dataset_image.counts.smooth(2).plot(ax=ax1, vmax=5)

ax2.set_title("Background map")
dataset_image.background.plot(ax=ax2, vmax=5)

ax3.set_title("Excess map")
dataset_image.excess.smooth(3).plot(ax=ax3, vmax=2)
plt.show()


######################################################################
# Source Detection
# ----------------
#
# Use the class `~gammapy.estimators.TSMapEstimator` and function
# `~gammapy.estimators.utils.find_peaks` to detect sources on the images.
# We search for 0.1 deg sigma gaussian sources in the dataset.
#

spatial_model = GaussianSpatialModel(sigma="0.05 deg")
spectral_model = PowerLawSpectralModel(index=2)
model = SkyModel(spatial_model=spatial_model, spectral_model=spectral_model)

ts_image_estimator = TSMapEstimator(
    model,
    kernel_width="0.5 deg",
    selection_optional=[],
    downsampling_factor=2,
    sum_over_energy_groups=False,
    energy_edges=[0.1, 10] * u.TeV,
)

images_ts = ts_image_estimator.run(stacked)

sources = find_peaks(
    images_ts["sqrt_ts"],
    threshold=5,
    min_distance="0.2 deg",
)
display(sources)

######################################################################
# To get the position of the sources, simply
#
source_pos = SkyCoord(sources["ra"], sources["dec"])
print(source_pos)

######################################################################
# Plot sources on top of significance sky image
#
fig, ax = plt.subplots(figsize=(8, 6), subplot_kw={"projection": geom_image.wcs})
images_ts["sqrt_ts"].plot(ax=ax, add_cbar=True)

ax.scatter(
    source_pos.ra.deg,
    source_pos.dec.deg,
    transform=ax.get_transform("icrs"),
    color="none",
    edgecolor="white",
    marker="o",
    s=200,
    lw=1.5,
)
plt.show()


######################################################################
# Spatial analysis
# ----------------
#
# See other notebooks for how to run a 3D cube or 2D image based analysis.
#


######################################################################
# Spectrum
# --------
#
# We’ll run a spectral analysis using the classical reflected regions
# background estimation method, and using the on-off (often called WSTAT)
# likelihood function.
#

target_position = SkyCoord(0, 0, unit="deg", frame="galactic")
on_radius = 0.2 * u.deg
on_region = CircleSkyRegion(center=target_position, radius=on_radius)

exclusion_mask = ~geom.to_image().region_mask([on_region])
exclusion_mask.plot()
plt.show()

######################################################################
# Configure spectral analysis

energy_axis = MapAxis.from_energy_bounds(0.1, 40, 40, unit="TeV", name="energy")
energy_axis_true = MapAxis.from_energy_bounds(
    0.05, 100, 200, unit="TeV", name="energy_true"
)

geom = RegionGeom.create(region=on_region, axes=[energy_axis])
dataset_empty = SpectrumDataset.create(geom=geom, energy_axis_true=energy_axis_true)

dataset_maker = SpectrumDatasetMaker(
    containment_correction=False, selection=["counts", "exposure", "edisp"]
)
bkg_maker = ReflectedRegionsBackgroundMaker(exclusion_mask=exclusion_mask)
safe_mask_masker = SafeMaskMaker(methods=["aeff-max"], aeff_percent=10)

######################################################################
# Run data reduction

datasets = Datasets()

for observation in observations:
    dataset = dataset_maker.run(
        dataset_empty.copy(name=f"obs-{observation.obs_id}"), observation
    )
    dataset_on_off = bkg_maker.run(dataset, observation)
    dataset_on_off = safe_mask_masker.run(dataset_on_off, observation)
    datasets.append(dataset_on_off)

######################################################################
# Plot results

plt.figure(figsize=(8, 6))
ax = dataset_image.counts.smooth("0.03 deg").plot(vmax=8)

on_region.to_pixel(ax.wcs).plot(ax=ax, edgecolor="white")
plot_spectrum_datasets_off_regions(datasets, ax=ax)
plt.show()


######################################################################
# Model fit
# ~~~~~~~~~
#
# The next step is to fit a spectral model, using all data (i.e. a
# “global” fit, using all energies).
#

spectral_model = PowerLawSpectralModel(
    index=2, amplitude=1e-11 * u.Unit("cm-2 s-1 TeV-1"), reference=1 * u.TeV
)

model = SkyModel(spectral_model=spectral_model, name="source-gc")

datasets.models = model

fit = Fit()
result = fit.run(datasets=datasets)
print(result)


######################################################################
# Here we can plot the predicted number of counts for each model and
# for the background in the dataset. This is especially useful when
# studying complex field with a lot a sources. There is a function
# in the visualization sub-package of gammapy that does this automatically.
#
# First we need to stack our datasets.


stacked_dataset = datasets.stack_reduce(name="stacked")
stacked_dataset.models = model

print(stacked_dataset)


######################################################################
# Call `~gammapy.visualization.plot_npred_signal` to plot the predicted counts.
#


plot_npred_signal(stacked_dataset)
plt.show()


######################################################################
# Spectral points
# ~~~~~~~~~~~~~~~
#
# Finally, let’s compute spectral points. The method used is to first
# choose an energy binning, and then to do a 1-dim likelihood fit /
# profile to compute the flux and flux error.
#


# Flux points are computed on stacked datasets
energy_edges = MapAxis.from_energy_bounds("1 TeV", "30 TeV", nbin=5).edges

fpe = FluxPointsEstimator(energy_edges=energy_edges, source="source-gc")
flux_points = fpe.run(datasets=[stacked_dataset])
flux_points.to_table(sed_type="dnde", formatted=True)


######################################################################
# Plot
# ~~~~
#
# Let’s plot the spectral model and points. You could do it directly, but
# for convenience we bundle the model and the flux points in a
# `~gammapy.datasets.FluxPointsDataset`:
#

flux_points_dataset = FluxPointsDataset(data=flux_points, models=model)
flux_points_dataset.plot_fit()
plt.show()


######################################################################
# Exercises
# ---------
#
# -  Re-run the analysis above, varying some analysis parameters, e.g.
#
#    -  Select a few other observations
#    -  Change the energy band for the map
#    -  Change the spectral model for the fit
#    -  Change the energy binning for the spectral points
#
# -  Change the target. Make a sky image and spectrum for your favourite
#    source.
#
#    -  If you don’t know any, the Crab nebula is the “hello world!”
#       analysis of gamma-ray astronomy.
#

# print('hello world')
# SkyCoord.from_name('crab')


######################################################################
# What next?
# ----------
#
# -  This notebook showed an example of a first CTAO analysis with Gammapy,
#    using simulated 1DC data.
# -  Let us know if you have any questions or issues!
#