keyCommandsDoc.py

# -*- coding: UTF-8 -*-
# A part of NonVisual Desktop Access (NVDA)
# Copyright (C) 2023-2024 NV Access Limited, Mesar Hameed, Takuya Nishimoto
# This file is covered by the GNU General Public License.
# See the file COPYING for more details.

"""
TODO: move to site_scons/site_tools

Generates the Key Commands document from the User Guide.
Works as a Python Markdown Extension:
https://python-markdown.github.io/extensions/

TODO move docs to docs folder

Generation of the Key Commands document requires certain commands to be included in the user guide.
These commands must begin at the start of the line and take the form::
	%kc:command: arg

The kc:title command must appear first and specifies the title of the Key Commands document.
For example:
	%kc:title: NVDA Key Commands

The rest of these commands are used to include key commands into the document.
Appropriate headings from the User Guide will be included implicitly.

The kc:beginInclude command begins a block of text which should be included verbatim.
The block ends at the kc:endInclude command.
For example::
	%kc:beginInclude
	|| Name | Desktop command | Laptop command | Description |
	...
	%kc:endInclude

The kc:settingsSection command indicates the beginning of a section documenting individual settings.
It specifies the header row for a table summarising the settings indicated by the kc:setting command
(see below).
In order, it must consist of a name column, a column for each keyboard layout and a description column.
For example::
	%kc:settingsSection: || Name | Desktop command | Laptop command | Description |

The kc:setting command indicates a section for an individual setting.
It must be followed by:
	* A heading containing the name of the setting;
	* A table row for each keyboard layout, or if the key is common to all layouts,
	a single line of text specifying the key after a colon;
	* A blank line; and
	* A line describing the setting.
For example:
	%kc:setting
	==== Braille Tethered To ====
	| Desktop command | NVDA+control+t |
	| Laptop Command | NVDA+control+t |
	This option allows you to choose whether the braille display will follow the system focus,
	or whether it follows the navigator object / review cursor.
"""

from enum import auto, Enum, IntEnum, StrEnum
import re
from collections.abc import Iterator

from markdown import Extension, Markdown
from markdown.preprocessors import Preprocessor


LINE_END = "\r\n"


class Section(IntEnum):
	"""Sections must be nested in this order."""
	HEADER = auto()
	BODY = auto()


class Command(StrEnum):
	TITLE = "title"
	BEGIN_INCLUDE = "beginInclude"
	END_INCLUDE = "endInclude"
	SETTING = "setting"
	SETTINGS_SECTION = "settingsSection"

	def t2tRegex(self) -> re.Pattern:
		return re.compile(rf"%kc:({self.value}.*)")


class Regex(Enum):
	COMMAND = re.compile(r"^<!-- KC:(?P<cmd>[^:\s]+)(?:: (?P<arg>.*))? -->$")
	HEADING = re.compile(r"^(?P<id>#+)(?P<txt>.*)$")
	SETTING_SINGLE_KEY = re.compile(r"^[^|]+?[:：]\s*(.+?)\s*$")
	TABLE_ROW = re.compile(r"^(\|.*\|)$")


class KeyCommandsError(Exception):
	"""Raised due to an error encountered in the User Guide related to generation of the Key Commands document.
	"""


class KeyCommandsExtension(Extension):
	# Magic number, priorities are not well documented.
	# It's unclear what the range of priorities are to compare to, but 25 seems to work, 1 doesn't.
	# See https://python-markdown.github.io/extensions/api/#registries
	PRIORITY = 25

	def extendMarkdown(self, md: Markdown):
		md.preprocessors.register(KeyCommandsPreprocessor(md), 'key_commands', self.PRIORITY)


class KeyCommandsPreprocessor(Preprocessor):
	def __init__(self, md: Markdown | None):
		super().__init__(md)
		self.initialize()

	def initialize(self):
		self._ugLines: Iterator[str] = iter(())
		self._kcLines: list[str] = []
		#: The current section of the key commands file.
		self._kcSect: Section = Section.HEADER
		#: The current stack of headings.
		self._headings: list[re.Match] = []
		#: The 0 based level of the last heading in L{_headings} written to the key commands file.
		self._kcLastHeadingLevel: int = -1
		#: Whether lines which aren't commands should be written to the key commands file as is.
		self._kcInclude: bool = False
		#: The header row for settings sections.
		self._settingsHeaderRow: str | None = None
		#: The number of layouts for settings in a settings section.
		self._settingsNumLayouts: int = 0
		#: The current line number being processed, used to present location of syntax errors
		self._lineNum: int = 0
		# We want to skip the title line to replace it with the KC:TITLE command argument.
		self._skippedTitle = False

	def run(self, lines: list[str]) -> list[str]:
		# Turn this into an iterator so we can use next() to seek through lines.
		self._ugLines = iter(lines)
		for line in self._ugLines:
			line = line.strip()
			self._lineNum += 1

			# We want to skip the title line to replace it with the KC:TITLE command argument.
			if line.startswith("# ") and not self._skippedTitle:
				self._skippedTitle = True
				continue

			m = Regex.COMMAND.value.match(line)
			if m:
				self._command(**m.groupdict())
				continue

			m = Regex.HEADING.value.match(line)
			if m:
				self._heading(m)
				continue

			if self._kcInclude:
				self._kcLines.append(line)

		return self._kcLines.copy()

	def _command(self, cmd: Command | None = None, arg: str | None = None):
		# Handle header commands.
		if cmd == Command.TITLE.value:
			if self._kcSect > Section.HEADER:
				raise KeyCommandsError(f"{self._lineNum}, title command is not valid here")
			# Write the title and two blank lines to complete the txt2tags header section.
			self._kcLines.append("# " + arg + LINE_END * 2)
			self._kcSect = Section.BODY
			return

		elif self._kcSect == Section.HEADER:
			raise KeyCommandsError(f"{self._lineNum}, title must be the first command")

		if cmd == Command.BEGIN_INCLUDE.value:
			self._writeHeadings()
			self._kcInclude = True
		elif cmd == Command.END_INCLUDE.value:
			self._kcInclude = False
			self._kcLines.append("")

		elif cmd == Command.SETTINGS_SECTION.value:
			# The argument is the table header row for the settings section.
			# Replace t2t header syntax with markdown syntax.
			self._settingsHeaderRow = arg.replace("||", "|")
			# There are name and description columns.
			# Each of the remaining columns provides keystrokes for one layout.
			# There's one less delimiter than there are columns, hence subtracting 1 instead of 2.
			self._settingsNumLayouts = arg.strip("|").count("|") - 1
			if self._settingsNumLayouts < 1:
				raise KeyCommandsError(
					f"{self._lineNum}, settingsSection command must specify the header row for a table"
					" summarising the settings"
				)

		elif cmd == Command.SETTING.value:
			self._handleSetting()

		else:
			raise KeyCommandsError(f"{self._lineNum}, Invalid command {cmd}")

	def _seekNonEmptyLine(self) -> str:
		"""Seeks to the next non-empty line in the user guide.
		"""
		line = next(self._ugLines).strip()
		self._lineNum += 1
		while not line:
			try:
				line = next(self._ugLines).strip()
			except StopIteration:
				return line
			self._lineNum += 1
		return line

	def _areHeadingsPending(self) -> bool:
		return self._kcLastHeadingLevel < len(self._headings) - 1

	def _writeHeadings(self):
		level = self._kcLastHeadingLevel + 1
		# Only write headings we haven't yet written.
		for level, heading in enumerate(self._headings[level:], level):
			self._kcLines.append(heading.group(0))
		self._kcLastHeadingLevel = level

	def _heading(self, m: re.Match):
		# We work with 0 based heading levels.
		level = len(m.group("id")) - 1
		try:
			del self._headings[level:]
		except IndexError:
			pass
		self._headings.append(m)
		self._kcLastHeadingLevel = min(self._kcLastHeadingLevel, level - 1)

	def _handleSetting(self):
		if not self._settingsHeaderRow:
			raise KeyCommandsError("%d, setting command cannot be used before settingsSection command" % self._lineNum)

		if self._areHeadingsPending():
			# There are new headings to write.
			# If there was a previous settings table, it ends here, so write a blank line.
			self._kcLines.append("")
			self._writeHeadings()
			# New headings were written, so we need to output the header row.
			self._kcLines.append(self._settingsHeaderRow)
			numCols = self._settingsNumLayouts + 2  # name + description + layouts
			self._kcLines.append("|" + "---|" * numCols)

		# The next line should be a heading which is the name of the setting.
		line = self._seekNonEmptyLine()
		m = Regex.HEADING.value.match(line)
		if not m:
			raise KeyCommandsError(f"{self._lineNum}, setting command must be followed by heading")
		name = m.group("txt")

		# The next few lines should be table rows for each layout.
		# Alternatively, if the key is common to all layouts, there will be a single line of text specifying the key after a colon.
		keys: list[str] = []
		for _layout in range(self._settingsNumLayouts):
			line = self._seekNonEmptyLine()

			m = Regex.SETTING_SINGLE_KEY.value.match(line)
			if m:
				keys.append(m.group(1))
				break
			elif not Regex.TABLE_ROW.value.match(line):
				raise KeyCommandsError(
					f"{self._lineNum}, setting command: "
					"There must be one table row for each keyboard layout"
				)

			# This is a table row.
			# The key will be the second column.
			try:
				key = line.strip("|").split("|")[1].strip()
			except IndexError:
				raise KeyCommandsError(f"{self._lineNum}, setting command: Key entry not found in table row.")
			else:
				keys.append(key)

		if 1 == len(keys) < self._settingsNumLayouts:
			# The key has only been specified once, so it is the same in all layouts.
			key = keys[0]
			keys[1:] = (key for _layout in range(self._settingsNumLayouts - 1))

		# There should now be a blank line.
		line = next(self._ugLines).strip()
		self._lineNum += 1
		if line:
			raise KeyCommandsError(
				f"{self._lineNum}, setting command: The keyboard shortcuts must be followed by a blank line. "
				"Multiple keys must be included in a table. "
				f"Erroneous key: {key}"
			)

		# Finally, the next line should be the description.
		desc = self._seekNonEmptyLine()
		self._kcLines.append(f"| {name} | {' | '.join(keys)} | {desc} |")
		if not self._kcLines[-2].startswith("|"):
			# The previous line was not a table, so this is a new table.
			# Write the header row.
			numCols = len(keys) + 2  # name + description + layouts
			self._kcLines.append("|" + "---|" * numCols)