"""
pyacl - high level abstractions over pylibacl
Copyright 2024, Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

Licensed under the EUPL, Version 1.2 or - as soon they will be approved by the European Commission - subsequent versions of the EUPL (the "Licence").
You may not use this work except in compliance with the Licence.
An English copy of the Licence is shipped in a file called LICENSE along with this applications source code.
You may obtain copies of the Licence in any of the official languages at https://joinup.ec.europa.eu/collection/eupl/eupl-text-eupl-12.
"""

import posix1e

DEFAULT_ENTRIES = [
  'u::rw-',
  'g::r--',
  'm::r--',
  'o::r--',
]

DEFAULT_PERMISSIONS = {
  'read': None,
  'write': None,
  'execute': None,
}

DEFAULT_ENTRYTYPES = [
  'user',
  'group',
  'mask',
  'other',
]

MAX_PERMBITS = 3


def reduce_entries(acl):
  entries = acl.to_any_text().decode().split()
  entries = [entry for entry in entries if entry not in DEFAULT_ENTRIES]
  return entries


def parse_permission(strpermission):
  if len(strpermission) != MAX_PERMBITS:
    return ValueError('Invalid permission')

  permap = {
    0: 'read',
    1: 'write',
    2: 'execute',
  }

  outmap = DEFAULT_PERMISSIONS.copy()

  for i, perm in permap.items():
    permval = strpermission[i]
    if permval in ['r', 'w', 'x']:
      outmap[perm] = True
    elif permval == '-':
      outmap[perm] = False
    else:
      return ValueError('Invalid permission flag')

  return outmap


def parse_entry(strentry):
  if not strentry:
    raise ValueError('Got empty string')

  entrytype, entryvalue, permissions = strentry.split(':')

  if entrytype not in DEFAULT_ENTRYTYPES:
    raise ValueError('Invalid entry')

  if entryvalue == '':
    entryvalue = None
  elif not entryvalue:
    return ValueError('Invalid entry value')

  if len(permissions) != MAX_PERMBITS:
    raise ValueError('Unsupported amount of permissions')

  return {
    entrytype: {
      entryvalue: parse_permission(permissions),
    },
  }


def parse_entries(acl):
  outmap = {
    group: DEFAULT_PERMISSIONS for group in DEFAULT_ENTRYTYPES
  }

  for entry in acl:
    outmap.update(parse_entry(entry))

  return outmap


def aclfromfile(path):
  return posix1e.ACL(file=path)


def entriesfromfile(path):
  return reduce_entries(aclfromfile(path))


def parsefromfile(path):
  return parse_entries(reduce_entries(aclfromfile(path)))