import os
import re
import sys
from string import ascii_letters, ascii_lowercase, digits
from typing import Optional, TYPE_CHECKING, cast


NO_EXTENSIONS = bool(os.environ.get("YARL_NO_EXTENSIONS"))  # type: bool

if sys.implementation.name != "cpython":
    NO_EXTENSIONS = True


BASCII_LOWERCASE = ascii_lowercase.encode("ascii")
BPCT_ALLOWED = {"%{:02X}".format(i).encode("ascii") for i in range(256)}
GEN_DELIMS = ":/?#[]@"
SUB_DELIMS_WITHOUT_QS = "!$'()*,"
SUB_DELIMS = SUB_DELIMS_WITHOUT_QS + "+&=;"
RESERVED = GEN_DELIMS + SUB_DELIMS
UNRESERVED = ascii_letters + digits + "-._~"
ALLOWED = UNRESERVED + SUB_DELIMS_WITHOUT_QS


_IS_HEX = re.compile(b"[A-Z0-9][A-Z0-9]")


class _Quoter:
    def __init__(
        self, *, safe: str = "", protected: str = "", qs: bool = False
    ) -> None:
        self._safe = safe
        self._protected = protected
        self._qs = qs

    def __call__(self, val: Optional[str]) -> Optional[str]:
        if val is None:
            return None
        if not isinstance(val, str):
            raise TypeError("Argument should be str")
        if not val:
            return ""
        bval = cast(str, val).encode("utf8", errors="ignore")
        ret = bytearray()
        pct = bytearray()
        safe = self._safe
        safe += ALLOWED
        if not self._qs:
            safe += "+&=;"
        safe += self._protected
        bsafe = safe.encode("ascii")
        idx = 0
        while idx < len(bval):
            ch = bval[idx]
            idx += 1

            if pct:
                if ch in BASCII_LOWERCASE:
                    ch = ch - 32  # convert to uppercase
                pct.append(ch)
                if len(pct) == 3:  # pragma: no branch   # peephole optimizer
                    buf = pct[1:]
                    if not _IS_HEX.match(buf):
                        ret.extend(b"%25")
                        pct.clear()
                        idx -= 2
                        continue
                    try:
                        unquoted = chr(int(pct[1:].decode("ascii"), base=16))
                    except ValueError:
                        ret.extend(b"%25")
                        pct.clear()
                        idx -= 2
                        continue

                    if unquoted in self._protected:
                        ret.extend(pct)
                    elif unquoted in safe:
                        ret.append(ord(unquoted))
                    else:
                        ret.extend(pct)
                    pct.clear()

                # special case, if we have only one char after "%"
                elif len(pct) == 2 and idx == len(bval):
                    ret.extend(b"%25")
                    pct.clear()
                    idx -= 1

                continue

            elif ch == ord("%"):
                pct.clear()
                pct.append(ch)

                # special case if "%" is last char
                if idx == len(bval):
                    ret.extend(b"%25")

                continue

            if self._qs:
                if ch == ord(" "):
                    ret.append(ord("+"))
                    continue
            if ch in bsafe:
                ret.append(ch)
                continue

            ret.extend(("%{:02X}".format(ch)).encode("ascii"))

        ret2 = ret.decode("ascii")
        if ret2 == val:
            return val
        return ret2


class _Unquoter:
    def __init__(self, *, unsafe: str = "", qs: bool = False) -> None:
        self._unsafe = unsafe
        self._qs = qs
        self._quoter = _Quoter()
        self._qs_quoter = _Quoter(qs=True)

    def __call__(self, val: Optional[str]) -> Optional[str]:
        if val is None:
            return None
        if not isinstance(val, str):
            raise TypeError("Argument should be str")
        if not val:
            return ""
        pct = ""
        last_pct = ""
        pcts = bytearray()
        ret = []
        for ch in val:
            if pct:
                pct += ch
                if len(pct) == 3:  # pragma: no branch   # peephole optimizer
                    pcts.append(int(pct[1:], base=16))
                    last_pct = pct
                    pct = ""
                continue
            if pcts:
                try:
                    unquoted = pcts.decode("utf8")
                except UnicodeDecodeError:
                    pass
                else:
                    if self._qs and unquoted in "+=&;":
                        to_add = self._qs_quoter(unquoted)
                        if to_add is None:  # pragma: no cover
                            raise RuntimeError("Cannot quote None")
                        ret.append(to_add)
                    elif unquoted in self._unsafe:
                        to_add = self._quoter(unquoted)
                        if to_add is None:  # pragma: no cover
                            raise RuntimeError("Cannot quote None")
                        ret.append(to_add)
                    else:
                        ret.append(unquoted)
                    del pcts[:]

            if ch == "%":
                pct = ch
                continue

            if pcts:
                ret.append(last_pct)  # %F8ab
                last_pct = ""

            if ch == "+":
                if not self._qs or ch in self._unsafe:
                    ret.append("+")
                else:
                    ret.append(" ")
                continue

            if ch in self._unsafe:
                ret.append("%")
                h = hex(ord(ch)).upper()[2:]
                for ch in h:
                    ret.append(ch)
                continue

            ret.append(ch)

        if pcts:
            try:
                unquoted = pcts.decode("utf8")
            except UnicodeDecodeError:
                ret.append(last_pct)  # %F8
            else:
                if self._qs and unquoted in "+=&;":
                    to_add = self._qs_quoter(unquoted)
                    if to_add is None:  # pragma: no cover
                        raise RuntimeError("Cannot quote None")
                    ret.append(to_add)
                elif unquoted in self._unsafe:
                    to_add = self._qs_quoter(unquoted)
                    if to_add is None:  # pragma: no cover
                        raise RuntimeError("Cannot quote None")
                    ret.append(to_add)
                else:
                    ret.append(unquoted)
        ret2 = "".join(ret)
        if ret2 == val:
            return val
        return ret2


_PyQuoter = _Quoter
_PyUnquoter = _Unquoter

if not TYPE_CHECKING and not NO_EXTENSIONS:  # pragma: no branch
    try:
        from ._quoting import _Quoter, _Unquoter
    except ImportError:  # pragma: no cover
        _Quoter = _PyQuoter
        _Unquoter = _PyUnquoter