#! /usr/bin/python3
#
# Run sassc and watch for changes in source files (using inotitfy) to rebuild
# automatically.
#
# Usage: sassw INPUT
# (output will automatically be INPUT with .scss changed to .css)

import json
import glob
import os
import pyinotify
import subprocess
import sys
import time

filename = sys.argv[1] if len(sys.argv) > 1 else '.'
if os.path.isdir(filename):
    scss_filenames = [x for x in os.listdir(filename) if not x.startswith('_') and x.endswith('.scss')]
    if not scss_filenames:
        print('Error: directory specified but no proper scss file within.', file=sys.stderr)
    filenames = [os.path.join(filename, x) for x in scss_filenames]
else:
    filenames = sys.argv[1:]

def build():
    global sources, directories
    directories = set()
    sources = set()
    for filename in filenames:
        result = subprocess.run(
                ['sassc', '-mauto', filename, filename.replace('.scss', '.css')],
                capture_output=True,
                text=True)
        sys.stdout.write(result.stdout)
        sys.stderr.write(result.stderr)
        if result.returncode:
            # error
            with open(filename.replace('.scss', '.css'), 'w') as fd:
                print('''body::before {
                          white-space: pre;
                          font-family: monospace;
                          content: "%s";
                         }''' % result.stderr.replace('\n', '\\A').replace('"', '\\"'),
                    file=fd)
        basepath = os.path.abspath(os.path.dirname(filename))
        sources = sources.union(set([os.path.abspath(os.path.join(basepath, x))
            for x in json.load(open(filename.replace('.scss', '.css.map')))['sources']]))
        directories = directories.union(set([os.path.dirname(x) for x in sources]))

class EventManager(pyinotify.ProcessEvent):
    def process_default(self, event):
        if event.pathname in sources:
            filename = os.path.basename(event.pathname)
            print(f'{filename} changed, building', end='')
            t0 = time.time()
            build()
            print(f' ({time.time() - t0:.2f}s)')


print('>>> Building %s' % ' '.join(filenames))
build()
wm = pyinotify.WatchManager()
notifier = pyinotify.Notifier(wm, default_proc_fun=EventManager())
for directory in directories:
    wm.add_watch(directory, pyinotify.IN_CLOSE_WRITE)
notifier.coalesce_events()
print('>>> Sassw is watching for changes. Press Ctrl-C to stop.')
notifier.loop()