#! /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 os.path.isdir(filename):
    scss_filenames = [x for x in os.listdir(filename) if x.startswith('_') and x.endswith('.scss')]
    if not scss_filenames:
        print('Error: directory specified but no proper scss file within.', file=sys.stderr)
    filename = os.path.join(filename, scss_filenames[0])

def build():
    global sources, directories
    subprocess.call(['sassc', '-mauto', filename, filename.replace('.scss', '.css')])
    basepath = os.path.abspath(os.path.dirname(filename))
    sources = [os.path.abspath(os.path.join(basepath, x)) for x in json.load(open(filename.replace('.scss', '.css.map')))['sources']]
    directories = 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)')

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()