import copy
import struct

fields = [
	('cpu', 'f', [
		'num_cpus',
		'user', 'iowait', 'system', 'nice',
		'guest', 'guest_nice',
		'irq', 'softirq', 'steal', 'idle',
	]),
	('mem', 'q', ['total', 'used', 'buffers', 'cached']),
	('net', 'q', [
		'bytes_recv', 'bytes_sent',
		'dropin', 'dropout', 'errin', 'errout',
	]),
	('disk', 'q', ['read_bytes', 'write_bytes', 'total', 'used']),
]

def gen_template(val):
	template = {}
	for stat_group, _, subfields in fields:
		field_data = {}
		if stat_group == 'disk':
			field_data = 
		else:
			for field in subfields:
				field_data[field] = copy.copy(val)
		template[stat_group] = field_data
	return template
TEMPLATE = gen_template([-1] * 1440)

def read_stats(f):
	stats = {}
	for stat_group, format_code, subfields in fields:
		field_data = {}
		fmt = '1440' + format_code
		if stat_group != 'disk':
			size = struct.calcsize(fmt)
			for field in subfields:
				field_data[field] = struct.unpack(fmt, f.read(size))
		else:
			buf = f.read() # disk is last, so we can read everything
			index = 0
			while index < len(buf):
				mountpoint_size = ord(buf[index])
				disk_fmt = '%dp %s %s' % (mountpoint_size + 1, fmt, fmt)
				size = struct.calcsize(disk_fmt)
				data = struct.unpack_from(disk_fmt, buf, index)

				mountpoint = data[0]
				total = data[1:1441]
				used = data[1441:]
				field_data[mountpoint] = {'used': used, 'total': total}
				index += size
		stats[stat_group] = field_data
	return stats

def dict_insert(d, split, value):
	if len(split) > 1:
		d.setdefault(split[0], {})
		dict_insert(d[split[0]], split[1:], value)
	else:
		d[split[0]] = value

def write_datum(f, data):
	for stat_group, format_code, subfields in fields:
		fmt = '1440' + format_code
		if stat_group != 'disk':
			for field in subfields:
				array = data[stat_group][field]
				f.write(struct.pack(fmt, *array))
		else:
			for mountpoint, disk_data in data['disk'].iteritems():
				mountpoint = mountpoint.encode('utf-8')
				disk_fmt = '%dp %s %s' % (len(mountpoint) + 1, fmt, fmt)
				array = disk_data['total'] + disk_data['used']
				f.write(struct.pack(disk_fmt, mountpoint, *array))