troggle/parsers/caves.py

import os
import re
import string
import sys

from pathlib import Path

from django.conf import settings
from django.db import transaction

from troggle.core.models.caves import Cave, CaveAndEntrance, Entrance, GetCaveLookup  
from troggle.core.models.survex import SurvexStation  
from troggle.core.models.troggle import DataIssue
from troggle.settings import CAVEDESCRIPTIONS, ENTRANCEDESCRIPTIONS, EXPOWEB, SURVEX_DATA

"""Reads all the cave description data and entrance description data 
by parsing the xml files stored as e.g. 
:EXPOWEB:/cave_data/1623-161.html 
or
:EXPOWEB:/entrance_data/1623-161g.html 

and creating the various Cave, Entrance and necessary Area objects.

This is the first import that happens after the database is reinitialised. 
So is the first thing that creates tables.

"""

todo = """  
- When reading cave data, to start off wit we do not know the cave id (slug) so we can't give a useful url in
  the error message, but we do have the filename. Systematize this, and the same thing with reading entrance files.
  
- Cannot use Edit This Page for pendingcaves.txt_edit as Edit This Page is expecting an html file.
   So we will need a separate file-editing capability just for this configuration file ?!
   
- we want to overwrite a PENDING cave if we are now importing the 1623-xxx.html file for it

- rewrite archaic regex
  re.findall("<%(itemname)s>(.*?)</%(itemname)s>" % {"itemname": itemname}, text, re.S)
  in modern form and pre-compile it. 
   
- crashes on MariaDB in databasereset.py on server when deleting Caves and complains Area needs a 
  non null parent, But this is not true.   The only solution we have found is to let it crash, then 
  stop and restart MariaDB (requires a logon able to sudo)   and then restart the databasereset.py 
  again. (status as of July 2022). May not happen now that class Area is removed (Sept.2023).
"""
AREACODES = {"1623", "1624", "1626", "1627"} # NB set not dict
ARGEAREAS = {"1626", "1627", "1624"} # NB set not dict

entrances_xslug = {}
caves_xslug = {}
areas_xslug = {}

LETTERS = list(string.ascii_lowercase)


def dummy_entrance(k, slug, msg="DUMMY"):
    """Returns an empty entrance object for either a PENDING cave or a DUMMY entrance if
    user forgot to provide one when creating the cave
    """
    ent = Entrance.objects.create( # creates object and saves into db
        name=k, slug=k, filename = k + ".html",
        entrance_description="Dummy entrance: auto-created when registering a new cave "
        + "and you forgot to create an entrance for it. Click on 'Edit' to enter the correct data, then 'Submit'.",
        marking="?",
    )
    if ent:
        return ent
    else:
        message = f" ! {k:11s}  {msg}-{slug} {k} entrance create failure"
        DataIssue.objects.create(parser="entrances", message=message, url=f"{slug}")
        print(message)
        raise # caught and handled by calling routine.



def set_dummy_entrance(id, slug, cave, msg="DUMMY"):
    """Called only when reading the cave and entrance html files
    
    Called when the Entrance field in a cave_data file is either missing or 
    holds a null string instead of a filename.
    
    Previously, the lack of an entrance where an entrance was expected, caused troggle to crash in several places. 
    But it is more robust now, so this is not necessary... we hope.
    
    Also, Cave and Entrance editing now expects there to be a real file (since April 2023), so creating this
    dummy is actually harmful. So this is commented out, pending removal after further experience.
    
    global variable entrances_xslug is simply a cache of references to Entrance objects
    to speed things up when parsing a lot of caves and entrances. All DB actions are time-consuming
    so 
    """
    global entrances_xslug
    message = f" - Note: Missing Entrance for entrance '{id}' on cave '{cave}' - Is this a problem?"
    DataIssue.objects.create(parser="entrances", message=message, url=f"{cave.url}")

def add_cave_to_pending_list(id, wallet, message):
    """(id, f"Wallet {wallet} - Could not find id <{id}>")
    """
    wurl = f"/walletedit/{wallet.walletname}".replace('#', ':')
    DataIssue.objects.update_or_create(parser="wallets", message=message, url=wurl)

def create_new_cave(svxpath, svxid=None, msg=None):
    """This is called only when a new survex file is edited online which has a path on the
    :loser: repo which is not recognised as a known cave.
    ALSO called by survex parser when it finds a cave it doesn't recognise
    """
    # e.g. svxpath = "caves-1623/666/beast" .svx - from the *inlcude tree
    # e.g. svxid = "caves-1623/666/beast"
    print(f"Create new cave at {svxpath} - {msg}")
    #
    survex_file = ""
    if svxid:
        sv = Path(settings.SURVEX_DATA, svxid + ".svx")
        if sv.is_file:
            survex_file = svxid + ".svx"
    else:
        sv = Path(settings.SURVEX_DATA, svxpath + ".svx")
        if sv.is_file:
            survex_file = svxpath + ".svx"
        
    if survex_file: 
        # message = f"Found a survex file {survex_file=} {svxpath=} {svxid=} "   
        # DataIssue.objects.create(parser="caves", message=message)
        # print(message, file=sys.stderr) 
        # print(message)
        pass
    else:
        message = f"NOT found a survex file {svxpath=} {svxid=}"   
        DataIssue.objects.create(parser="caves", message=message)
        print(message, file=sys.stderr) 
        print(message)
      
    parts = svxpath.split("/")
    a = parts[0][-4:]
    caveid = parts[1]
    print(f"parts {parts}, {a}, {caveid}")
    # double check
    if a[0:3] == "162":
        areacode = a[0:4]
        url = f"{areacode}/{caveid}/{caveid}.html"  # Note we are appending the .html as we are believe in backwards compatability. This is to fix Martin's new 2023 app.
    else: 
        print(f"WARNING: parsers/caves/create_new_cave called with svxpath '{svxpath}'.  Surely it should start 'caves-162*'? {msg}")
        areacode = "1623"
        url = f"1623/{caveid}/{caveid}.html"
         
    k = f"{areacode}-{caveid}"

    caves = Cave.objects.filter(unofficial_number=caveid, areacode =areacode) 
    if caves:
        message = f" ! Already exists, caveid:{k} in areacode {areacode} {caves} - {msg}"
        DataIssue.objects.create(parser="caves", message=message)
        print(message)
        return caves[0]
        
    urltest = Cave.objects.filter(url=url)
    if urltest:
        message = f" ! Cave {urltest[0]} already exists with this url {url}. Can't create new cave {slug} from {svxpath} "
        DataIssue.objects.create(parser="caves", message=message, url=url)
        print(message)
        return urltest[0]
    try:
        cave = do_pending_cave(k, caveid, url, areacode, msg)
    except:
        message = f" ! Error. Cannot create pending cave and entrance, pending-id:{k} in area {areacode} - {msg}"
        DataIssue.objects.create(parser="caves", message=message)
        print(message)
        raise    
    
    # But this sets the survex file on  the Cave from the first one we find, not necessarily the best survex file for this cave
    cave.survex_file=survex_file # primary survex file for Cave
    cave.areacode=areacode
    cave.save()
    return cave

def do_ARGE_cave(slug, caveid, areacode, svxid):
    """Only called by survex parser, NOT the cave parser.
    Creates a new Cave object, but with abbreviated data as the survex file (from ARGE) is all we have.
    We already know the survex file.
    We already know that the cave doesn't exist... though there are bugs..
    
    Assumes anything in the ARGE list of cave areas is Arge, which is not true for 1626...
    
    caveid may be kataster number or it may be e.g. LA34
    """
    
    default_note = "This is (probably) an ARGE cave where we only have the survex file and no other information"
    url = f"{areacode}/{caveid}/{caveid}.html"

    urltest = Cave.objects.filter(url=url)
    if urltest:
        message = f" ! Cave {urltest[0]} already exists with this url {url}. Can't create new ARGE cave {slug} from {svxid}"
        DataIssue.objects.create(parser="caves", message=message, url=url)
        print(message)
        return urltest[0]
        
    numtest = Cave.objects.filter(unofficial_number=caveid.upper(), areacode=areacode)
    if numtest:
        message = f" ! Cave {numtest[0]} already exists with this areacode {areacode} and unofficial_number {caveid.upper()}. Can't create new ARGE cave {slug}"
        DataIssue.objects.create(parser="caves", message=message, url=url)
        print(message)
        return numtest[0]
    
    sv = Path(settings.SURVEX_DATA, svxid + ".svx")
    if sv.is_file:
        with open(sv, "r") as s:
            line1 = s.readline()
            line2 = s.readline()
            line3 = s.readline()
            rest = s.readlines()
    else:
        print(f"not correct svxid {svxid} {sv}", file=sys.stderr)
    
    print(f"{caveid} {rest}")
    passages = "\n"
    for line in rest:
        if line.strip().startswith("*begin"):
            passages = f"{passages}{line}"
    cave = Cave( 
    underground_description="ARGE cave.<br>3 lines of the survexfile, then all the *begin lines:<br><pre>" + line1 +line2 +line3 +passages +"</pre>",
    unofficial_number="ARGE",
    survex_file= f"{svxid}.svx",
    url=url, 
    notes=default_note,
    areacode=areacode,
    )
    if cave:
        try:
            kn = int(caveid)
            cave.kataster_number=kn # should only set this if all digit
        except:
            # must be unofficial 'number' or name
            cave.unofficial_number=caveid
   
        cave.save() 

    else:
        message = f" ! {slug:11s}  ARGE cave create failure {caveid=} {url=} {areacode=} {svxid=}"
        DataIssue.objects.create(parser="caves", message=message)
        print(message)
        return None

    return cave
    
def do_pending_cave(slug, caveid, url, areacode, msg=None):
    """
    default for a PENDING cave, should be overwritten in the db later if a real cave of the same name exists
    in expoweb/cave_data/1623-"k".html

    Note that at this point (parsing caves) in importing the data we have not yet seen the survex files, so we can't
    look inside the relevant survex file to find the year and so we con't provide helpful links.
    This also gets called when parsing survex files, when we do have this info.
    """

    def get_survex_file(k):
        """Guesses at and finds a survex file for this pending cave.
        Convoluted. Needs rewriting.
        Pointless if this cave is being created because we found a survex file...
        
        One problem is that the Cave name may have different capitalisation from the survex filename,
        e.g. 2018-NTU-02 has a survex file 2018-ntu-02.svx
        """
        if k[0:3] == "162":
            id = Path(k[5:])
        else:
            id = Path(k)

        survex_file = f"caves-{areacode}/{id}/{id}.svx"
        if Path(settings.SURVEX_DATA, survex_file).is_file():
            return survex_file
        else:
            survex_file = f"caves-{areacode}/{id}.svx"
            if Path(settings.SURVEX_DATA, survex_file).is_file():
                return survex_file

        # This should find the file even if the capitalisation is different, or if the directory name is totally different
        survex_file = ""
        d = Path(settings.SURVEX_DATA, f"caves-{areacode}/{id}")
        if d.is_dir():
            prime_suspect = ""
            dir = d.iterdir()
            for f in dir:
                if f.suffix == ".svx":
                    survex_file = f.relative_to(settings.SURVEX_DATA)
                    chk = min(5, len(f.name) - 1)
                    if str(f.name)[:chk].lower() == str(id.name)[:chk].lower():  # bodge which mostly works
                        prime_suspect = survex_file
            if prime_suspect:
                survex_file = prime_suspect
                # message = f" ! {k:14} Found a survex file which might be the right one: {survex_file} - {msg}"
                # DataIssue.objects.create(parser='caves', message=message, url=url)
                # print(message)
                if Path(settings.SURVEX_DATA, survex_file).is_file():
                    return survex_file
        return ""

    g = GetCaveLookup()
    with transaction.atomic():
        if slug in g:
            message = f" ! {slug:18} cave listed in pendingcaves.txt already exists. - {msg}"
            DataIssue.objects.create(parser="caves", message=message, url=url)
            print(message)
            return

        default_note = "A reference has been found to this cave id in a survex file in the loser repo, or in a wallet metadata"
        default_note += " in a JSON file in the drawings repo, but no Cave Description exists in expoweb (in /cave_data/)<br><br><br>\n"
        default_note += "INSTRUCTIONS: FIRST read the notes in <a href='/cave_data/pendingcaves.txt'>pendingcaves.txt</a><br />"
        default_note += "Next open 'This survex file' (link above the CaveView panel) to find the date and info. Then "
        default_note += '<br><br>\n\n - (0) look in the <a href="/noinfo/cave-number-index">cave number index</a> for notes on this cave,  '
        default_note += "<br><br>\n\n - (1) search in the survex file for the *ref to find a "
        default_note += "relevant wallet, e.g.<a href='/survey_scans/2009%252311/'>2009#11</a> and read the notes image files <br>\n - "
        default_note += (
            "<br><br>\n\n - (2) search in the Expo for that year e.g. <a href='/expedition/2009'>2009</a> to find a "
        )
        default_note += "relevant logbook entry, remember that the date may have been recorded incorrectly, "
        default_note += (
            "so check for trips i.e. logbook entries involving the same people as were listed in the survex file, "
        )
        default_note += (
            "and you should also check the scanned copy of the logbook (linked from each logbook entry page) "
        )
        default_note += "just in case a vital trip was not transcribed, then <br>\n - "
        default_note += (
            "click on 'Edit this cave' and copy the information you find in the survex file and the logbook"
        )
        default_note += "and delete all the text in the 'Notes' section - which is the text you are reading now."
        default_note += "<br><br>\n\n - Only two fields on this  form are essential. "
        default_note += "Documentation of all the fields on 'Edit this cave' form is in <a href='/handbook/survey/caveentryfields.html'>handbook/survey/caveentryfields</a>"
        default_note += "<br><br>\n\n - "
        default_note += "You will also need to create a new entrance from the 'Edit this cave' page. Ignore the existing dummy one, it will evaporate on the next full import."
        default_note += "<br><br>\n\n - "
        default_note += "When you Submit it will create a new file in expoweb/cave_data/ "
        default_note += (
            "<br><br>\n\n - Now you can edit the entrance info: click on Edit below for the dummy entrance. "
        )
        default_note += "and then Submit to save it (if you forget to do this, a dummy entrance will be created for your new cave description)."
        default_note += "<br><br>\n\n - Finally, you need to find a nerd to edit the file '<var>expoweb/cave_data/pending.txt</var>' "
        default_note += (
            f"to remove the line <br><var>{slug}</var><br> as it is no longer 'pending' but 'done. Well Done."
        )
        urltest = Cave.objects.filter(url=url)
        if urltest:
            message = f" ! Cave {urltest[0]} already exists with this url {url}. Can't create new cave {slug}"
            DataIssue.objects.create(parser="caves", message=message, url=url)
            print(message)
            return urltest[0]

        survex_file = get_survex_file(slug)

        cave = Cave(
            unofficial_number=caveid,
            underground_description="Pending cave write-up - No cave description created yet.",
            survex_file=survex_file,
            url=url,
            notes=default_note,
            areacode=areacode,
        )
        if cave:
            cave.save()  # must save to have id before foreign keys work. This is also a ManyToMany key.
            message = f" ! {slug:18} Pending cave write-up url: {url} - {survex_file=} - {msg}"
            DataIssue.objects.create(parser="caves", message=message, url=url)
            print(message)

        else:
            message = f" ! {slug:11s}  PENDING cave create failure - {msg}"
            DataIssue.objects.create(parser="caves", message=message)
            print(message)

    return cave

def getXML(text, itemname, minItems=1, maxItems=None, context=""):
    """Reads a single XML tag
    Should throw exception rather than producing error message here,
    then handle exception in calling routine where it has the context.
    
    This always succeeds, but it produces error message on the terminal and in the
    DataIssues log.
    """
    items = re.findall("<%(itemname)s>(.*?)</%(itemname)s>" % {"itemname": itemname}, text, re.S)
    if len(items) < minItems:
        message = (
            " ! %(count)i x %(itemname)s found, at least %(min)i expected. Load may ABORT. "
            % {"count": len(items), "itemname": itemname, "min": minItems}
            + " in file "
            + context
        )
        DataIssue.objects.create(parser="caves", message=message, url="" + context)
        print(message)

    if maxItems is not None and len(items) > maxItems:
        message = (
            " ! %(count)i x %(itemname)s found, no more than %(max)i expected in this XML unit. Load may ABORT. "
            % {"count": len(items), "itemname": itemname, "max": maxItems}
            + " in file "
            + context
        )
        DataIssue.objects.create(parser="caves", message=message, url="" + context)
        print(message)
    if minItems == 0:
        if not items:
            items = [""]
    return items


def boolify(boolstrs):
            return {
            "True": True,
            "False": False,
            "true": True,
            "false": False}[boolstrs[0]]
            
def validate_station(station):
    """It is possible to break troggle entirely by getting this wrong.
    These station identifiers are matched against other stations using .endswith()
    in parsers/locations.py
    so a simple number here will match hundreds of SUrvexStation objects
    It should be, e.g. "1623.p240"
    
    We will test them against survex stations after we have loaded them.
    """
    if station == "":
        return True
 
    # CANNOT test against locations as we have not read the survex files yet. Hmph.
        
    # Must have the right format in its name
    dot = station.find(".")
    if dot == -1:
        print(dot)
        # no full stop found. Bad station identifier.
        # should just skip really, and log an error
        raise
    else:
        return True

def read_entrance(filename, ent=None):
    """Reads an entrance description from the .html file.
       Runs on initial full import, and also whenever an entrance is edited online.

      If not called as part of initial import, then the global lists will not be correct
      but this is OK, a search will find them in the db.
      
      EDIT href examples
      /1623-1:1623-1a_entrance_edit
      /1623/1/1623-1_cave_edit/

      Args:
        filename: The name of the entrance_data .html file, e.g. 1623-JS-01a.html
        ent: The entrance object, if it already exists.

      Returns:
        The entrance object, or a new entrance object if `ent` is None.
      """
    def getXMLmin0(field):
        return getXML(entrancecontents, field, minItems=0, maxItems=1, context=context) 

    def getXMLmax1(field):
        return getXML(entrancecontents, field, maxItems=1, context=context)
        
    global entrances_xslug
    global caves_xslug
    global areas_xslug

    # Note: these are HTML files in the EXPOWEB repo, not from the loser repo.
    with open(os.path.join(ENTRANCEDESCRIPTIONS, filename)) as f:
        contents = f.read()
    context = filename
    
    # Derive the letter, entrance slug and cave slug from the filename
    entslug_fn = filename[:-5] # remove .html
    if entslug_fn[-1] in LETTERS:
        caveslug_fn = entslug_fn[:-1]
        letter_fn = entslug_fn[-1]
    else:
        caveslug_fn = entslug_fn
        letter_fn = ""
        
    ent_area = filename[:4]
    cave_name = caveslug_fn[5:] # remove initial 1623-
    
    ent_edit_url = f"/{caveslug_fn}:{entslug_fn}_entrance_edit" 
    cave_edit_url = f"/{ent_area}/{cave_name}/{cave_name}_cave_edit"
    
    
    # validate filename, check areacode
    if ent_area not in AREACODES:
        message = f'! BAD AREA CODE in "{filename}". Not recognised.'
        DataIssue.objects.create(parser="entrances", message=message, url=ent_edit_url)
        print(message)
        
    # New system 2024, create the Cave object when parsing Entrances, not Caves
    cave = make_cave(caveslug_fn)
    
    # try:  
        # cs = CaveSlug.objects.update_or_create(cave=cave, slug=caveslug_fn, primary=True)
    # except Exception as ex:
        # #raise
        # # This fails to do an update! It just crashes.. to be fixed
        # message = f" ! Entrances: CaveSlug {cave} update/create failure : {caveslug_fn}, skipping cave_data file {filename} with exception\nException: {ex.__class__}"
        # DataIssue.objects.create(parser="caves", message=message, url=context)
        # print(message)
    
    entrancecontentslist = getXML(contents, "entrance", maxItems=1, context=context)
    if len(entrancecontentslist) != 1:
        message = f'! BAD ENTRANCE DATA in "{filename}". More than one entrance. Edit file manually, click.'
        DataIssue.objects.create(parser="entrances", message=message, url=ent_edit_url)
        print(message)
        return None

    entrancecontents = entrancecontentslist[0]
    slugs = getXMLmin0("slug") # not the full slug, just the id: i.e. without the 1623- prefix
    # we ignore all these, because we now just use the filename. But if they are there, we validate them.
    if len(slugs) > 0 :
        slug = slugs[0]

        if len(slugs) >1:
            # Only ever one of these per entrance in the expo dataset
            message = f" ! - More than one slug for an entrance: {entrance}, slugs: {slugs}. Ignoring all of them."
            DataIssue.objects.create(parser="entrances", message=message, url=cave_edit_url)
            print(message)
            
        if slug and slug != entslug_fn:
            message = f" ! - Warning, mismatch between entrance slug (or unofficial name) and filename:  {slug=} {filename=}. Ignoring slug field, using filename."
            DataIssue.objects.create(parser="xEntrances", message=message, url=cave_edit_url)
            print(message)
    slug = entslug_fn # force 
    
    lastvisit = getXML(entrancecontents, "lastvisit", maxItems=1, minItems=0, context=cave_edit_url)
    lat_wgs84 = getXML(entrancecontents, "lat_wgs84", maxItems=1, minItems=0, context=cave_edit_url)
    long_wgs84 = getXML(entrancecontents, "long_wgs84", maxItems=1, minItems=0, context=cave_edit_url)

    alt = getXMLmax1("alt")
    approach = getXMLmax1("approach")
    bearings = getXMLmax1("bearings")
    entrance_description = getXMLmax1("entrance_description")
    explorers = getXMLmax1("explorers")
    findability = getXMLmax1("findability")
    findability_description = getXMLmax1("findability_description")
    location_description = getXMLmax1("location_description")
    #map_description = getXMLmax1("map_description")
    marking = getXMLmax1("marking")
    marking_comment = getXMLmax1("marking_comment")
    name = getXMLmax1("name")
    non_public = getXMLmax1("non_public")
    other_description = getXMLmax1("other_description")
    other_station = getXMLmax1("other_station")
    photo = getXMLmax1("photo")
    tag_station = getXMLmax1("tag_station")
    underground_description = getXMLmax1("underground_description")

    if not ent:
        ent, state = Entrance.objects.update_or_create(slug=slug)
        
    ent.name=name[0]
    ent.non_public=boolify(non_public)
    ent.alt=alt[0]
    ent.approach=approach[0]
    ent.bearings=bearings[0]
    ent.lat_wgs84=lat_wgs84[0]
    ent.long_wgs84=long_wgs84[0]
    ent.entrance_description=entrance_description[0]
    ent.explorers=explorers[0]
    ent.filename=filename
    ent.findability=findability[0]
    ent.findability_description=findability_description[0]
    ent.lastvisit=lastvisit[0]
    ent.location_description=location_description[0]
    #ent.map_description=map_description[0]
    ent.marking=marking[0]
    ent.marking_comment=marking_comment[0]
    ent.other_description=other_description[0]
    ent.other_station=other_station[0]
    ent.photo=photo[0]
    # ent.slug=slugs[0] # set algorithically
    ent.tag_station=tag_station[0]
    ent.underground_description=underground_description[0]
    
    for st in [ent.other_station, ent.tag_station]:
        #validate_station(st)
        try:
            validate_station(st)
        except:
            message = f" ! BAD ENTRANCE TAG '{st}' in '{filename}'. Must format like '1623.p204'. Edit file manually, click."
            #http://localhost:8000/1623/2023-EBH-01/1623-2023-EBH-01:1623-2023-EBH-01_entrance_edit
            DataIssue.objects.create(parser="entrances", message=message, url=ent_edit_url) # url=f"/1623/{slug}/{slug}:{slug}_entrance_edit")
            print(message)
    ent.save()
    return ent

def make_cave(slug):
    """Making a Cave object, but when we have multiple entrances, the Cave object may already exist"""
    filename = f"{slug}.html"
    try:
        cave, state = Cave.objects.update_or_create(filename=filename) # replace with slug when CaveSlug tidied up
        #print(f" - created:{state} cave.id:{cave} with {filename=}")

    except:
        print(f" ! FAILED to get only one CAVE in db when updating using: {filename} or not found.")
        kaves = Cave.objects.all().filter(filename=filename) # assumes filename unique, eeugh.
        for k in kaves:
            message = " ! - DUPLICATES in db. kataster:" + str(k.kataster_number) + ", slug:" + str(k.slug())
            DataIssue.objects.create(parser="caves", message=message, url=context)
            print(message)
        for k in kaves:
            if k.slug() is not None:
                print(" ! - OVERWRITING this one: slug:" + str(k.slug()))
                k.notes = "DUPLICATE kataster number found on import. Please fix\n" + k.notes
                cave = k
    return cave
                
def read_cave(filename, mvf=None, cave=None):
    """Reads an entrance description from the .html file
    Convoluted. Sorry. Needs rewriting
    
    mvf is a file handle for misnamed files
    
    If not called as part of initial import, then the global lists will not be correct
    but this is OK, a search will find them in the db.
    
    Attempted to use standard python3.11 xml library but fails on HTML entities (2023-04-23)
    import xml.etree.ElementTree as ET
    tree = ET.parse(fn)
    xml_root = tree.getroot()
    for t in ["html", "head", "body", "cave","non_public", "caveslug", "official_name","entrance"]:
        elements = xml_root.findall(t)

    """
    def getXMLmin0(field):
        return getXML(cavecontents, field, minItems=0, maxItems=1, context=context) 

    def getXMLmax1(field):
        return getXML(cavecontents, field, minItems=0, maxItems=1, context=context)
        
    def do_entrances():
        """For both bulk import and individual re-reading of cave_data file,
        fix the entrances
        
        What is Class CaveAndEntrance for? It was to allow mandy<=>many relationship between caves and entrances, but now we insist
        only one Cave for any Entrance, so this Class is reduncdant and should be removed..
        """
        c = cave
        for e in entrances:
            eslugs = getXML(e, "entranceslug", maxItems=1, context=context)
            if len(eslugs) < 1:
                print(f"TYPO IN cave_data file <entrance> tag contents\n <entrance> contents: {e}\n  {eslugs=}")
            eslug = eslugs[0]
            # if eslug.endswith(('a','b','c','d','e','f')):
                # print(f"! Entrance {eslug}")
            # if eslug.endswith('a b'):
                # message = f' - Entrance has weird name slug:"{eslug}" cave:"{cave}" caveslug:"{slug}" filename:"cave_data/{filename}"'
                # DataIssue.objects.create(parser="xEntrances", message=message, url=f"{cave.url}_cave_edit/")
                # print(message)        

            letter = getXML(e, "letter", maxItems=1, context=context)[0]
        
            if len(entrances) > 1 and letter =="":
                # Usually the second entrance is 'b', but the first is still unlettered. So probably 'a'
                letter = eslug[-1].lower()
                if letter.lower() not in list(string.ascii_lowercase):
                    letter = "a"
                message = f"- Warning - Empty 'letter' field for '{eslug}' in multiple-entrance cave '{cave}', setting to {letter}."
                #eurl = f"{cave.url}_cave_edit/"
                eurl = Path(cave.url).parent + f"{cave.slug()}_cave_edit/"
                # edit recognizer: (?P<path>.*)/(?P<slug>[^/]+)_cave_edit/$                
                DataIssue.objects.create(parser="entrances", message=message, url=eurl)
                print(message)   

            if len(entrances) == 1 and not eslug:  # may be empty: <entranceslug></entranceslug>
                msg="DUMMY: no entrance slug read from file, so assume textually same as cave slug"
                set_dummy_entrance(slug[5:], slug, c, msg=msg)
                print(f"! {msg}\n- {slug} {c}")
            else:
                if eslug in entrances_xslug:
                    # print(f"eslug {eslug} found eslug in xslug cache ")
                    entrance = entrances_xslug[eslug]
                else:
                    # print(f"eslug {eslug} looking up entrance ")
                    try:
                        entrance = Entrance.objects.get(slug=eslug)
                        entrances_xslug[eslug] = entrance
                    except:
                        message = f"! Fail entrance loading {eslug}  /entrance_data/{eslug} file does not exist or loading it from {filename} failed."         
                        DataIssue.objects.create(parser="entrances", message=message, url=f"{cave.url}_cave_edit/")
                        print(message)   
                        print(e)
                        return                        

                if eslug != f"{entrance}":
                    message = f"eslug {eslug} using different entrance {entrance} to set CaveAndEntrance"         
                    DataIssue.objects.create(parser="xEntrances", message=message, url=f"{cave.areacode}/{cave.areacode}-{cave.url}_cave_edit/")
                    print(message)        
                try:    
                    # this fails if there is not an unambiguous letter set.
                    CaveAndEntrance.objects.update_or_create(
                        cave=cave, entranceletter=letter, entrance=entrance
                    )
                except:
                    print(f"! Entrance setting failure {slug}")
                    message = f' ! Entrance setting failure, slug:"{slug}" #entrances:{len(entrances)} letter:"{letter}" cave:"{cave}" filename:"cave_data/{filename}"\n{e}'
                    DataIssue.objects.create(parser="entrances", message=message, url=f"{cave.areacode}/{cave.areacode}-{cave.url}_cave_edit/")
                    print(message)        
    def reload_entrances():
        """For individual re-reading of a cave_data file when editing,
        also re-read the entrance_data files
        """
        for eslug in entrances_xslug:
            entrance = entrances_xslug[eslug]
            read_entrance(entrance.filename, ent=entrance)
            entrance.save()

    def do_caveslugstuff(context):
        """This may be a fossil. We only have one slug per cave in troggle.
         Pending destruction of this whole concept and Class CaveSlug
         What is Class CaveSlug for?
         """
        return
            
    def check_directory(areacode, caveid, url, cave):
        dir = Path(settings.EXPOWEB, areacode, caveid)
        dir_l = Path(settings.EXPOWEB, areacode, caveid.lower())
        dir_u = Path(settings.EXPOWEB, areacode, caveid.upper())
        if dir.is_dir():
            return
        if dir_l.is_dir() or dir_u.is_dir():
            message = f" ! Cave URL capitalisation incorrect  '{dir}' is not a directory but different capitalisation is. {url=}\n - Fix by renaming cave_data/{caveid}.html which determines the cave id OR by renaming the directory and hand-fixing all the links to the files in the cave description."
            DataIssue.objects.create(parser="caves", message=message, url=f"{cave.newslug()}_cave_edit/")
            print(message)
            return
        if cave.filename:
            # not a pending cave, yet the directory does not exist. This is FINE. Many don't (yet)
            pass
            
    def check_slug(areacode, kataster_number, unofficial_number, url):
        """There is a <caveslug> field in the .html file, but we now ignore it as we use the 
         filename itself to set the slug.
         However we do check it for sanity, if it is there, pending its removal eventually."""
           
        if kataster_number:
            if slug == f"{areacode}-{kataster_number}":
                return slug
            message = f" ! Cave Slug mismatch (kataster): '{slug}' != '{areacode}-{kataster_number}' {url=} in file {filename}. IGNORING caveslug field in the .html file."
            correctslug = f"{areacode}-{kataster_number}"

        else:
            if slug == f"{areacode}-{unofficial_number}":
                return slug
            if slug.lower() == f"{areacode}-{unofficial_number.lower()}":
                message = f" ! Cave Slug capitalisation incorrect (unofficial): '{slug}' != '{areacode}-{unofficial_number}' {url=} in file {filename}. IGNORING caveslug field in the .html file."
                correctslug = slug.lower()
            else:
                message = f" ! Cave Slug mismatch (unofficial): '{slug}' != '{areacode}-{unofficial_number}' {url=} in file {filename} IGNORING caveslug field in the .html file."
                correctslug = f"{areacode}-{unofficial_number}"
                
        msgurl=f"/{correctslug[0:4]}/{correctslug}_cave_edit/"
        DataIssue.objects.create(parser="caves", message=message, url=msgurl) # url here is for the href link to edit the bad data in the DataIssues page
        mvtext = f"mv {filename} {correctslug}.html"
        #print(mvtext)
        if filename != f"{correctslug}.html" :
            message = f" ! Filename is not the same as the cave slug '{slug}' != '{areacode}-{unofficial_number}' {url=} in file {filename} IGNORING caveslug field in the .html file."
            DataIssue.objects.create(parser="caves", message=message, url=msgurl) # url here is for where the file actually is, for editing
            mvf.write(mvtext + "\n")
        print(message)              
        return correctslug
         
    global entrances_xslug
    global caves_xslug
    global areas_xslug

    # Note: we want to overwrite a PENDING cave if we are now importing the 1623-xxx.html file for it
    
    # Note: these are HTML files in the EXPOWEB repo, not from the loser repo.
    fn = settings.CAVEDESCRIPTIONS / filename
    
    #print(f" - Reading Cave from cave descriptions file {fn}")
    if not fn.exists():
        message = f" ! Cave_data file reading problem filename:'cave_data/{filename}'"
        DataIssue.objects.create(parser="caves", message=message, url="")
        print(message)
        return None

    # ignore <caveslug> read from the filename
    slug = filename[:-5] # strip off the ".html" at the end of the filename
    slugs = [slug]
    areacode = slug[:4]

    context = f"/{areacode}/{slug}_cave_edit" 
        
    with open(fn) as f:
        contents = f.read()
    cavecontentslist = getXML(contents, "cave", maxItems=1, context=context)

    if len(cavecontentslist) != 1:
        message = f'! BAD CAVE DATA in "{filename}". More than one cave. Edit file manually, click.'
        DataIssue.objects.create(parser="caves", message=message, url="")
        print(message)
        return None
        
    cavecontents = cavecontentslist[0]
 
    #print(f"{filename=} {slug=}")
    if slug[-1].lower() in LETTERS:
        message = f" ! Cave name ends in a letter not a number. Fix this! in file {filename} "
        DataIssue.objects.create(parser="caves", message=message, url=context) # url here is for where the file actually is, for editing
        print(message)
 
    non_public = getXMLmax1("non_public")
    official_name = getXMLmax1("official_name")
    kataster_code = getXMLmax1("kataster_code")
    kataster_number = getXMLmax1("kataster_number")
    unofficial_number = getXMLmax1("unofficial_number")
    explorers = getXMLmax1("explorers")
    underground_description = getXMLmax1("underground_description")
    equipment = getXMLmax1("equipment")
    references = getXMLmax1("references")
    survey = getXMLmax1("survey")
    #kataster_status = getXMLmax1("kataster_status")
    #underground_centre_line = getXMLmax1("underground_centre_line")
    notes = getXMLmax1("notes")
    survex_file = getXMLmax1("survex_file")
    description_file = getXMLmax1("description_file")

    # Optional, but probably deprecated as we should just derive this from the survex data
    length = getXMLmin0("length")
    depth = getXMLmin0("depth")
    extent = getXMLmin0("extent")

    manual_edit = True
    if not cave:
        # we are parsing using databaseReset.py not an online edit
        # we have already checked for uniqueness but the Cave object may/should be already created by the Entrance parsing
        manual_edit = False
        
        # The Cave object should already have been created when reading the entrance_data file
        caves = Cave.objects.filter(filename=filename) 
        if len(caves) ==1:
            cave = caves[0]
        else:
            c = Cave.objects.filter(filename=filename.lower()) 
            if len(c) ==1:
                cave = c[0]
            else:
                print(f" * Cannot find single Cave object for cave_data/{filename}  from entrance_data file. {len(caves)} found")
                return False
                

    # From here on the code applies to both edited and newly-imported caves (mostly!)
    do_caveslugstuff(context) # needs cave!=None

    # We no longer need the <area> tag to define 1623 etc as we get that from the filename.
    areas = getXML(cavecontents, "area", context=context, minItems=0) # can be multiple <area> tags
    for area_slug in areas:
        if area_slug not in AREACODES: # only detect subareas
            cave.subarea = area_slug
    if not cave.areacode:
         if areacode in AREACODES:
            cave.areacode = areacode
         
    cave.non_public=boolify(non_public)
    cave.official_name=official_name[0]
    cave.kataster_code=kataster_code[0]
    if "+" in kataster_code[0]:
        cave.fully_explored = True
        # print(f"{kataster_code[0]} {slug}")
    cave.kataster_number=kataster_number[0]
    cave.unofficial_number=unofficial_number[0]
    cave.explorers=explorers[0]
    cave.underground_description=underground_description[0]
    cave.equipment=equipment[0]
    cave.references=references[0]
    cave.survey=survey[0]
    #cave.kataster_status=kataster_status[0]
    #cave.underground_centre_line=underground_centre_line[0]
    cave.notes=notes[0]
    if length:
        cave.length=length[0]
    if depth:
        cave.depth=depth[0]
    if extent:
        cave.extent=extent[0]
    cave.survex_file=survex_file[0]
    cave.description_file=description_file[0]
    # cave.url=url[0] # set algorithically now:
    cave.url = f"{cave.areacode}/{cave.number()}/{cave.number()}.html"
    check_directory(cave.areacode, cave.number(), cave.url, cave)

    slug = check_slug(cave.areacode, cave.kataster_number, cave.unofficial_number, cave.url) #NB cave.slug is not a field on Cave
               
    # Thsi whole way of doing entrances can be replaced by simply knowing the entrance_data filename what the cave is. to do.
    entrances = getXML(cavecontents, "entrance", context=context)
    #do_entrances()
    if not entrances or len(entrances) < 1:
        # missing entrance link in cave_data/1623-* .html file
        set_dummy_entrance(slug[5:], slug, cave, msg="DUMMY: no entrances")
    else:
        do_entrances()
    if manual_edit:
        reload_entrances()
        
    if survex_file[0]:
        if not (Path(SURVEX_DATA) / survex_file[0]).is_file():
            message = f' ! {slug:12} survex filename does not exist :LOSER:"{survex_file[0]}" in "{filename}"'
            DataIssue.objects.create(parser="caves", message=message, url=f"/{slug[0:4]}/{slug}_cave_edit/")
            print(message)
    # else:
        # print(f"{slug:12} survex filename UNSET")
            

    if description_file[0]:  # if not an empty string
        message = f' - {slug:12} Note (not an error): complex description filename "{description_file[0]}" inside "cave_data/{filename}"'
        DataIssue.objects.create(parser="caves ok", message=message, url=f"/{slug}_cave_edit/")
        # print(message)

        if not (Path(EXPOWEB) / description_file[0]).is_file():
            message = f' ! {slug:12} description filename  "{EXPOWEB}/{description_file[0]}" does not refer to a real file'
            DataIssue.objects.create(parser="caves", message=message, url=f"/{slug}_cave_edit/")
            print(message)
    cave.save()
    return cave
 
def readcaves():
    """Called from databaseReset mass importer.
    Reads the xml-format HTML 'cave' files in the EXPOWEB repo, the survex files from the loser repo.
    """
    # Pending is for those caves which do not have cave_data/1623-xxx.html XML files even though 
    # they exist and have surveys. 
    with transaction.atomic():
        pending = set()
        fpending = Path(CAVEDESCRIPTIONS, "pendingcaves.txt")
        if fpending.is_file():
            with open(fpending, "r") as fo:
                cids = fo.readlines()
            for cid in cids:
                pcaveid = cid.split(";", 1)[0] # split on ";" and take the first bit
                pcaveid = pcaveid.strip().rstrip("\n")
                if pcaveid =="":
                    continue
                pending.add(pcaveid)

    with transaction.atomic():
        print(" - Deleting Caves and Entrances")
        # attempting to avoid MariaDB crash when doing this
        try:
            Area.objects.all().delete()
        except:
            pass
        try:
            Cave.objects.all().delete()
        except:
            pass
        try:
            Entrance.objects.all().delete()
        except:
            pass
            
    # Clear the cave data issues and the caves as we are reloading
    DataIssue.objects.filter(parser="areas").delete()
    DataIssue.objects.filter(parser="caves").delete()
    DataIssue.objects.filter(parser="caves ok").delete()
    DataIssue.objects.filter(parser="aliases").delete()
    DataIssue.objects.filter(parser="aliases ok").delete()

    #DataIssue.objects.filter(parser="entrances").delete()
    #DataIssue.objects.filter(parser="xEntrances").delete()

    with transaction.atomic():
        print(" - Reading Entrances from entrance descriptions xml files")
        for filename in next(os.walk(ENTRANCEDESCRIPTIONS))[2]:  # Should be a better way of getting a list of files, use pathlib !
            read_entrance(filename)

    # Why is this needed ? Without it, we lose these DataIssues!
    ent_issues = DataIssue.objects.filter(parser="entrances")
    print(f" _ We now have  {len(ent_issues)} entrance DataIssues")

    with transaction.atomic():
        print(" - Reading Caves from cave descriptions xml files")
        mvscript = "/tmp/mvscript.sh" # in .gitignore so no problem creating it on server in /troggle/
        with open(mvscript, "w") as mvf: # overwrite
            mvf.write(f"cd {CAVEDESCRIPTIONS}\n")
            for filename in next(os.walk(CAVEDESCRIPTIONS))[2]:  # Should be a better way of getting a list of files
                if filename.endswith(".html"):
                    read_cave(filename, mvf)

    print(" - Setting up all the variously useful alias names")
    GetCaveLookup()

    print(" - Setting pending caves")
    # Do this last, so we can detect if they are created and no longer 'pending'

    with transaction.atomic():
        for k in pending:

            if k[0:3] == "162":
                areacode = k[0:4]
                number = k[5:]
                url = f"{areacode}/{k[5:]}.html"  # Note we are appending the .html to allow for offline websites
            else:
                areacode = "1623"
                number = k
                url = f"1623/{k}"

            try:
                do_pending_cave(k, number, url, areacode)
            except:
                message = f" ! Error. Cannot create pending cave, pending-id:{k} in area {areacode}"
                DataIssue.objects.create(parser="caves", message=message)
                print(message)
                raise