run-commands-from-markdown/markdownrunner.py

#!/bin/python3

import pandoc
import pandoc.types as t
import sys
from dataclasses import dataclass
from typing import *

# There are three parts:
# - Parse a given markdown and extract the commands
#    - Also: keep track of the groups / ...
# - Let the user decide, what to run / edit / split / skip
# - Run the commands remotely

# Usage: $0 remote.host.name md1 ...

host: str

def main():
	if len(sys.argv) < 3:
		print(f"Usage: {sys.argv[0]} hostname file1.md ...")
		exit(1)
	# Here I would use Haskell's pointfree functions, so that host is implicitly passed...
	# Never mind, it will be a global variable NOTE THIS!!!
	global host
	host = sys.argv[1]
	for file in sys.argv[2:]:
		process_file(file)

@dataclass
class Command:
	user: str
	directory: Union[str, None]
	command: str
	context: str

def stringify(block) -> str:
	"""
	Take an object of some of pandoc.types and make the best of it.
	"""
	# The pandoc library has a fancy function for that...
	return pandoc.write(block)

def extract_snippets(pd: t.Pandoc) -> Sequence[Tuple[str, str]]:
	"""
	This extracts snippets from the code. The problem is, that we want context with it, so we return a list of tuples (previous_block_stringified, code_snippet).
	"""
	result = []
	last_block = ""
	for block in pd[1]:
		if isinstance(block, t.CodeBlock):
			result.append((last_block, block[1]))
		last_block = stringify(block)
	return result

def parse_snippet(s: Tuple[str, str]) -> Sequence[Command]:
	# Will return always a list, even if it has only one element.
	# This is where we handle blank lines, comments, cd's and sudo's, so that the Commands in the output are "runnable"

	# The original context should be mentioned for all hunks
	context = s[0]
	
	
	# We now check the separate lines and possibly tweak them (e.g. by removing sudo-s)
	lines = s[1].split('\n')
	directory = None	# Don't cd by default
	user = 'root'	# Connect as root by default (it does not really matter, since the commands are run with sudo's)
	result = []
	for line in lines:
		line = line.strip()
		if line.startswith('cd'):
			parts = line.split()
			assert len(parts) == 2
			directory = parts[1]
			continue
		elif line.startswith('sudo -u'):
			parts = line.split(maxsplit=4)
			assert parts[3] == '-H', "Insecure sudo?"
			user = parts[2]
			directory = f'~{user}'	# This actually works with SSH. That is nice, since we don't need to know the target's /etc/passwd
			cmd = parts[4]
		elif line.startswith('sudo'):
			parts = line.split(maxsplit=1)
			assert not parts[1].startswith('-'), "Weird sudo"
			user = 'root'
			cmd = parts[1]
		elif line == '':
			# Only add it to context for reference
			context = f'{context}\n'
			continue
		else:
			# No sudo or cd, just a command.
			user = 'root'	# Reset to default
			cmd = line
		result.append(Command(user=user,directory=directory,command=cmd,context=context))
		# Let's have the previously processed commands in the context
		context = f"{context}\nCMD: {user}:{directory if directory else '??'} $ {cmd}"
	return result	# I miss the right feature of Nim lang...



def user_action(hunk: Sequence[Command], context=None) -> Sequence[Command]:
	# Maybe modify the commands to run.
	# This should have a simple UI: show the hunk with context (ideally in grey), ask what to do, return the wanted command
	# Actions: yes(y): accept input; no(n): skip this command; edit(e): launch $EDITOR or vim on the hunk; quit(q): terminate; split(s): split hunks to individual lines and ask for each one.
	
	# FIXME: We don't implement splitting yet, because it's simple to comment / delete in the editor
	# FIXME: We only show given context and don't care for the command's one; that's wrong.
	
	def stringify_hunk(hunk):
		result = ''
		for cmd in hunk:
			global host
			result += f'SSH: {cmd.user}@{host} {cmd.directory} $ {cmd.command}\n'
		return result


	# TODO: Print context in color (gray?)
	print('-------------------------------------------')
	print(context)
	print()
	print(stringify_hunk(hunk))

	# TODO: Print prompt in color (green?)
	answer = input("What to do: edit(e), run(y, default), skip(n)?")
	if answer is None:
		# Default is run, for convenience
		answer = 'Y'
	if answer.startswith(('e', 'E')):
		import tempfile
		with tempfile.NamedTemporaryFile(mode='r+') as tmpfile:
			# Fill the file with data
			for cmd in hunk:
				tmpfile.file.write(f"{cmd.user}\t{cmd.directory if cmd.directory else ''}\t{cmd.command}\n")
			tmpfile.file.flush()	# Should not be needed, but better safe than sorry
			# Let the user edit the file
			import os
			editor = os.getenv('EDITOR')
			if editor is None:
				# Fallback to vim
				editor = 'vim'
			import subprocess
			subprocess.run([editor, tmpfile.name])
			# Read the file back
			tmpfile.file.seek(0)
			new_hunk = []
			for line in tmpfile.file.readlines():
				if line == '':
					continue
				parts = line.split('\t', maxsplit=2)
				# Change user to None if it is not specified
				parts[0] = parts[0].strip() if parts[0].strip() != '' else None
				# Change directory to None if it is not specified
				parts[1] = parts[1].strip() if parts[1].strip() != '' else None
				new_hunk.append(Command(user=parts[0],directory=parts[1],command=parts[2],context=None))
			# Python has no goto for restarting, but we can recurse
			return user_action(new_hunk, context)
	elif answer.startswith(('y', 'Y')):
		return hunk
	elif answer.startswith(('n', 'N')):
		return []



def run_command(cmd: Command):
	# Generate and run the SSH command.
	global host
	local_command = ['ssh', host]
	remote_command = cmd.command
	if cmd.user is not None:
		local_command.extend(['-l', cmd.user])
	if cmd.directory is not None:
		remote_command = f'cd {cmd.directory}; {remote_command}'
	local_command.append(remote_command)
	
	# Run
	import subprocess
	process = subprocess.run(local_command)
	if process.returncode != 0:
		# TODO: Print in color (red?)
		answer = input(f"Command {process.args} failed with return code {process.returncode}. Continue? ")
		if not answer.startswith(('Y', 'y', 'a', 'A')):	# We are Czech, so "ano" is a valid answer :-)
			print("Bailing out")
			sys.exit(1)


def process_file(fn: str):
	"""
	To be called upon each file on the command line. This function should perform all the steps needed in order to remotely run a parsed markdown, id est the three parts above.
	"""
	pd = pandoc.read(file=fn)
	snippets = extract_snippets(pd)
	for snip in snippets:
		cmds = parse_snippet(snip)
		cmds = user_action(cmds, context=cmds[0].context)
		for cmd in cmds:
			run_command(cmd)

if __name__ == '__main__':
	main()