"""
==================================================
Querying the GOES flare event list through the HEK
==================================================

How to retrieve the GOES flare event list through use of
sunpy's Heliophysics Event Knowledgebase (HEK) client.
"""
from sunpy.net import Fido
from sunpy.net import attrs as a

###################################################################
# We use Fido to to query the HEK catalogue. We define our event type
# as a flare ("FL"). We also set up the start and end times over which
# we will search for flare events. We want the list of events
# that were detected by the GOES X-ray Sensor (XRS) instrument between
# ``tstart`` and ``tend`` and GOES class > M1.0.

event_type = "FL"
tstart = "2013/10/28"
tend = "2013/10/29"
result = Fido.search(a.Time(tstart, tend),
                     a.hek.EventType(event_type),
                     a.hek.FL.GOESCls > "M1.0",
                     a.hek.OBS.Observatory == "GOES")

###################################################################
# The result is returned as a `~sunpy.net.fido_factory.UnifiedResponse`,
# from which we can see a table from one provider is found and returned.

# Here we only show two columns due there being over 100 columns returned normally.
print(result.show("hpc_bbox", "refs"))

# It"s also possible to access the HEK results from the
# `~sunpy.net.fido_factory.UnifiedResponse` by name.

hek_results = result["hek"]

###################################################################
# We can also print the key-values that correspond to the HEK parameters returned
# in result[0]. The ``.table`` attribute returns an `~astropy.table.Table`.

print(hek_results.colnames)

###################################################################
# The results returned to the `~sunpy.net.hek.hek.HEKTable`
# contain a lot of information and we may only want to keep some main
# results such as start time, end time, peak time, GOES-class, and
# active region number. This can be done as so:

new_table = hek_results["event_starttime", "event_peaktime",
                        "event_endtime", "fl_goescls", "ar_noaanum"]

###################################################################
# These results can then be saved to a CSV file, or any other file
# format that `~astropy.table.Table` supports.

new_table.write("october_M1_flares.csv", format="csv")