#!/usr/bin/python3

"""
Reads through the wiki dump, attempts to parse short-descriptions,
and adds them to a database
"""

# In testing, this script took over 10 hours to run, and generated about 5GB

import sys, os, re
import bz2
import html, mwxml, mwparserfromhell
import sqlite3

DUMP_FILE = 'enwiki-20220501-pages-articles-multistream.xml.bz2' # Had about 22e6 pages
DB_FILE = 'desc_data.db'

DESC_LINE_REGEX = re.compile('^ *[A-Z\'"]')
EMBEDDED_HTML_REGEX = re.compile(r'<[^<]+/>|<!--[^<]+-->|<[^</]+>([^<]*|[^<]*<[^<]+>[^<]*)</[^<]+>|<[^<]+$')
	# Recognises a self-closing HTML tag, a tag with 0 children, tag with 1 child with 0 children, or unclosed tag
CONVERT_TEMPLATE_REGEX = re.compile(r'{{convert\|(\d[^|]*)\|(?:(to|-)\|(\d[^|]*)\|)?([a-z][^|}]*)[^}]*}}')
def convertTemplateReplace(match):
	""" Used in regex-substitution with CONVERT_TEMPLATE_REGEX """
	if match.group(2) is None:
		return f'{match.group(1)} {match.group(4)}'
	else:
		return f'{match.group(1)} {match.group(2)} {match.group(3)} {match.group(4)}'
PARENS_GROUP_REGEX = re.compile(r' \([^()]*\)')
LEFTOVER_BRACE_REGEX = re.compile(r'(?:{\||{{).*')

def genData(dumpFile: str, dbFile: str) -> None:
	print('Creating database')
	if os.path.exists(dbFile):
		raise Exception(f'ERROR: Existing {dbFile}')
	dbCon = sqlite3.connect(dbFile)
	dbCur = dbCon.cursor()
	dbCur.execute('CREATE TABLE pages (id INT PRIMARY KEY, title TEXT UNIQUE)')
	dbCur.execute('CREATE INDEX pages_title_idx ON pages(title COLLATE NOCASE)')
	dbCur.execute('CREATE TABLE redirects (id INT PRIMARY KEY, target TEXT)')
	dbCur.execute('CREATE INDEX redirects_idx ON redirects(target)')
	dbCur.execute('CREATE TABLE descs (id INT PRIMARY KEY, desc TEXT)')
	#
	print('Iterating through dump file')
	with bz2.open(dumpFile, mode='rt') as file:
		for pageNum, page in enumerate(mwxml.Dump.from_file(file), 1):
			if pageNum % 1e4 == 0:
				print(f'At page {pageNum}')
			# Parse page
			if page.namespace == 0:
				try:
					dbCur.execute('INSERT INTO pages VALUES (?, ?)', (page.id, convertTitle(page.title)))
				except sqlite3.IntegrityError as e:
					# Accounts for certain pages that have the same title
					print(f'Failed to add page with title "{page.title}": {e}', file=sys.stderr)
					continue
				if page.redirect is not None:
					dbCur.execute('INSERT INTO redirects VALUES (?, ?)', (page.id, convertTitle(page.redirect)))
				else:
					revision = next(page)
					desc = parseDesc(revision.text)
					if desc is not None:
						dbCur.execute('INSERT INTO descs VALUES (?, ?)', (page.id, desc))
	#
	print('Closing database')
	dbCon.commit()
	dbCon.close()
def parseDesc(text: str) -> str | None:
	# Find first matching line outside {{...}}, [[...]], and block-html-comment constructs,
		# and then accumulate lines until a blank one.
	# Some cases not accounted for include: disambiguation pages, abstracts with sentences split-across-lines, 
		# nested embedded html, 'content significant' embedded-html, markup not removable with mwparsefromhell, 
	lines: list[str] = []
	openBraceCount = 0
	openBracketCount = 0
	inComment = False
	skip = False
	for line in text.splitlines():
		line = line.strip()
		if not lines:
			if line:
				if openBraceCount > 0 or line[0] == '{':
					openBraceCount += line.count('{')
					openBraceCount -= line.count('}')
					skip = True
				if openBracketCount > 0 or line[0] == '[':
					openBracketCount += line.count('[')
					openBracketCount -= line.count(']')
					skip = True
				if inComment or line.find('<!--') != -1:
					if line.find('-->') != -1:
						if inComment:
							inComment = False
							skip = True
					else:
						inComment = True
						skip = True
				if skip:
					skip = False
					continue
				if line[-1] == ':': # Seems to help avoid disambiguation pages
					return None
				if DESC_LINE_REGEX.match(line) is not None:
					lines.append(line)
		else:
			if not line:
				return removeMarkup(' '.join(lines))
			lines.append(line)
	if lines:
		return removeMarkup(' '.join(lines))
	return None
def removeMarkup(content: str) -> str:
	content = EMBEDDED_HTML_REGEX.sub('', content)
	content = CONVERT_TEMPLATE_REGEX.sub(convertTemplateReplace, content)
	content = mwparserfromhell.parse(content).strip_code() # Remove wikitext markup
	content = PARENS_GROUP_REGEX.sub('', content)
	content = LEFTOVER_BRACE_REGEX.sub('', content)
	return content
def convertTitle(title: str) -> str:
	return html.unescape(title).replace('_', ' ')

if __name__ == '__main__':
	import argparse
	parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
	parser.parse_args()
	#
	genData(DUMP_FILE, DB_FILE)