"""
This contains a bunch of RFC7230 definitions and regular expressions that are
needed to properly parse HTTP messages.
"""

import re

HEXDIG = "[0-9a-fA-F]"
DIGIT = "[0-9]"

WS = "[ \t]"
OWS = WS + "{0,}?"
RWS = WS + "{1,}?"
BWS = OWS

# RFC 7230 Section 3.2.6 "Field Value Components":
# tchar          = "!" / "#" / "$" / "%" / "&" / "'" / "*"
#                / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
#                / DIGIT / ALPHA
# obs-text      = %x80-FF
TCHAR = r"[!#$%&'*+\-.^_`|~0-9A-Za-z]"
OBS_TEXT = r"\x80-\xff"

TOKEN = TCHAR + "{1,}"

# RFC 5234 Appendix B.1 "Core Rules":
# VCHAR         =  %x21-7E
#                  ; visible (printing) characters
VCHAR = r"\x21-\x7e"

# The '\\' between \x5b and \x5d is needed to escape \x5d (']')
QDTEXT = "[\t \x21\x23-\x5b\\\x5d-\x7e" + OBS_TEXT + "]"

QUOTED_PAIR = r"\\" + "([\t " + VCHAR + OBS_TEXT + "])"
QUOTED_STRING = '"(?:(?:' + QDTEXT + ")|(?:" + QUOTED_PAIR + '))*"'

# header-field   = field-name ":" OWS field-value OWS
# field-name     = token
# field-value    = *( field-content / obs-fold )
# field-content  = field-vchar [ 1*( SP / HTAB ) field-vchar ]
# field-vchar    = VCHAR / obs-text

# Errata from: https://www.rfc-editor.org/errata_search.php?rfc=7230&eid=4189
# changes field-content to:
#
# field-content  = field-vchar [ 1*( SP / HTAB / field-vchar )
#                  field-vchar ]

FIELD_VCHAR = "[" + VCHAR + OBS_TEXT + "]"
# Field content is more greedy than the ABNF, in that it will match the whole value
FIELD_CONTENT = FIELD_VCHAR + "+(?:[ \t]+" + FIELD_VCHAR + "+)*"
# Which allows the field value here to just see if there is even a value in the first place
FIELD_VALUE = "(?:" + FIELD_CONTENT + ")?"

# chunk-ext      = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
# chunk-ext-name = token
# chunk-ext-val  = token / quoted-string

CHUNK_EXT_NAME = TOKEN
CHUNK_EXT_VAL = "(?:" + TOKEN + ")|(?:" + QUOTED_STRING + ")"
CHUNK_EXT = (
    "(?:;(?P<extension>" + CHUNK_EXT_NAME + ")(?:=(?P<value>" + CHUNK_EXT_VAL + "))?)*"
)

# Pre-compiled regular expressions for use elsewhere
ONLY_HEXDIG_RE = re.compile(("^" + HEXDIG + "+$").encode("latin-1"))
ONLY_DIGIT_RE = re.compile(("^" + DIGIT + "+$").encode("latin-1"))
HEADER_FIELD_RE = re.compile(
    (
        "^(?P<name>" + TOKEN + "):" + OWS + "(?P<value>" + FIELD_VALUE + ")" + OWS + "$"
    ).encode("latin-1")
)
QUOTED_PAIR_RE = re.compile(QUOTED_PAIR)
QUOTED_STRING_RE = re.compile(QUOTED_STRING)
CHUNK_EXT_RE = re.compile(("^" + CHUNK_EXT + "$").encode("latin-1"))