"""
Internal constants for the difference analysis sub-package.
"""

import re

__all__ = [
    'ACROFORM_EXEMPT_STRICT_COMPARISON',
    'ROOT_EXEMPT_STRICT_COMPARISON',
    'FORMFIELD_ALWAYS_MODIFIABLE',
    'VALUE_UPDATE_KEYS',
    'VRI_KEY_PATTERN',
]


# /Type: dictionary type (can always be added if correct)
# /Ff: Form field flags
FORMFIELD_ALWAYS_MODIFIABLE = {'/Ff', '/Type'}


# /AP: appearance dictionary
# /AS: current appearance state
# /V: field value
# /F: (widget) annotation flags
# /DA: default appearance
# /Q: quadding
VALUE_UPDATE_KEYS = FORMFIELD_ALWAYS_MODIFIABLE | {
    '/AP',
    '/AS',
    '/V',
    '/F',
    '/DA',
    '/Q',
}


VRI_KEY_PATTERN = re.compile('/[A-Z0-9]{40}')


ACROFORM_EXEMPT_STRICT_COMPARISON = {
    '/Fields',
    '/DR',
    '/DA',
    '/Q',
    '/NeedAppearances',
}


ROOT_EXEMPT_STRICT_COMPARISON = {
    '/AcroForm',
    '/DSS',
    '/Extensions',
    '/Metadata',
    '/MarkInfo',
    '/Version',
}