import re
import logging
from abc import abstractmethod
from collections import defaultdict
from functools import lru_cache
from typing import Any, Callable, Dict, List, Optional, AnyStr, Union
from urllib.parse import unquote

from blacksheep.utils import ensure_bytes, ensure_str

__all__ = [
    "Router",
    "Route",
    "RouteMatch",
    "RouteDuplicate",
    "RegisteredRoute",
    "RoutesRegistry",
    "HTTPMethod",
]


class HTTPMethod:
    GET = "GET"
    HEAD = "HEAD"
    POST = "POST"
    PUT = "PUT"
    DELETE = "DELETE"
    TRACE = "TRACE"
    OPTIONS = "OPTIONS"
    CONNECT = "CONNECT"
    PATCH = "PATCH"


_route_all_rx = re.compile(b"\\*")
_route_param_rx = re.compile(b"/:([^/]+)")
_mustache_route_param_rx = re.compile(b"/{([^}]+)}")
_angle_bracket_route_param_rx = re.compile(b"/<([^>]+)>")
_named_group_rx = re.compile(b"\\?P<([^>]+)>")
_escaped_chars = {b".", b"[", b"]", b"(", b")"}


class RouteException(Exception):
    ...


class RouteDuplicate(RouteException):
    def __init__(self, method, pattern, current_handler):
        method = ensure_str(method)
        pattern = ensure_str(pattern)
        super().__init__(
            f"Cannot register route pattern `{pattern}` for "
            f"`{method}` more than once. "
            f"This pattern is already registered for handler "
            f"{current_handler.__qualname__}."
        )
        self.method = method
        self.pattern = pattern
        self.current_handler = current_handler


class InvalidValuePatternName(RouteException):
    def __init__(self, parameter_pattern_name: str, matched_parameter: str) -> None:
        super().__init__(
            f"Invalid value pattern: {parameter_pattern_name} "
            f"for route parameter {matched_parameter}."
            f"Define a value pattern in the `Route.value_patterns` class "
            f"attribute to configure additional patterns for route values."
        )

        self.parameter_pattern_name = parameter_pattern_name
        self.matched_parameter = matched_parameter


class RouteMatch:

    __slots__ = ("values", "pattern", "handler")

    def __init__(self, route: "Route", values: Optional[Dict[str, bytes]]):
        self.handler = route.handler
        self.pattern = route.pattern
        self.values: Optional[Dict[str, str]] = (
            {k: unquote(v.decode("utf8")) for k, v in values.items()}
            if values
            else None
        )


def _get_parameter_pattern_fragment(
    parameter_name: bytes, value_pattern: bytes = br"[^\/]+"
) -> bytes:
    return b"/(?P<" + parameter_name + b">" + value_pattern + b")"


class Route:

    __slots__ = (
        "handler",
        "pattern",
        "param_names",
        "_rx",
    )

    pattern: bytes

    value_patterns = {
        "string": r"[^\/]+",
        "str": r"[^\/]+",
        "path": r".*",
        "int": r"\d+",
        "float": r"\d+(?:\.\d+)?",
        "uuid": r"[a-zA-Z0-9]{8}-[a-zA-Z0-9]{4}-[a-zA-Z0-9]"
        + r"{4}-[a-zA-Z0-9]{4}-[a-zA-Z0-9]{12}",
    }

    def __init__(self, pattern: Union[str, bytes], handler: Any):
        raw_pattern = self.normalize_pattern(pattern)
        self.handler = handler
        self.pattern = raw_pattern
        rx, param_names = self._get_regex_for_pattern(raw_pattern)
        self._rx = rx
        self.param_names = [name.decode("utf8") for name in param_names]

    @property
    def rx(self) -> re.Pattern:
        return self._rx

    @property
    def has_params(self) -> bool:
        return self._rx.groups > 0

    def _get_regex_for_pattern(self, pattern: bytes):
        """
        Converts a raw pattern into a compiled regular expression that can be used
        to match bytes URL paths, extracting route parameters.
        """
        # TODO: should blacksheep support ":" in routes (using escape chars)?
        for c in _escaped_chars:
            if c in pattern:
                pattern = pattern.replace(c, b"\\" + c)

        if b"*" in pattern:
            # throw exception if a star appears more than once
            if pattern.count(b"*") > 1:
                raise RouteException(
                    "A route pattern cannot contain more than one star sign *. "
                    "Multiple star signs are not supported."
                )

            if b"/*" in pattern:
                pattern = _route_all_rx.sub(br"?(?P<tail>.*)", pattern)
            else:
                pattern = _route_all_rx.sub(br"(?P<tail>.*)", pattern)

        # support for < > patterns, e.g. /api/cats/<cat_id>
        # but also: /api/cats/<int:cat_id> or /api/cats/<uuid:cat_id> for more
        # granular control on the generated pattern
        if b"<" in pattern:
            pattern = _angle_bracket_route_param_rx.sub(
                self._handle_rich_parameter, pattern
            )

        # support for mustache patterns, e.g. /api/cats/{cat_id}
        # but also: /api/cats/{int:cat_id} or /api/cats/{uuid:cat_id} for more
        # granular control on the generated pattern
        if b"{" in pattern:
            pattern = _mustache_route_param_rx.sub(self._handle_rich_parameter, pattern)

        # route parameters defined using /:name syntax
        if b"/:" in pattern:
            pattern = _route_param_rx.sub(br"/(?P<\1>[^\/]+)", pattern)

        # NB: following code is just to throw user friendly errors;
        # regex would fail anyway, but with a more complex message
        # 'sre_constants.error: redefinition of group name'
        # we only return param names as they are useful for other things
        param_names = []
        for p in _named_group_rx.finditer(pattern):
            param_name = p.group(1)
            if param_name in param_names:
                raise ValueError(
                    f"cannot have multiple parameters with name: " f"{param_name}"
                )

            param_names.append(param_name)

        if len(pattern) > 1 and not pattern.endswith(b"*"):
            # NB: the /? at the end ensures that a route is matched both with
            # a trailing slash or not
            pattern = pattern + b"/?"
        return re.compile(b"^" + pattern + b"$", re.IGNORECASE), param_names

    def _handle_rich_parameter(self, match: re.Match):
        """
        Handles a route parameter that can include details about the pattern,
        for example:

        /api/cats/<int:cat_id>
        /api/cats/<uuid:cat_id>

        /api/cats/{int:cat_id}
        /api/cats/{uuid:cat_id}
        """
        assert (
            len(match.groups()) == 1
        ), "The regex using this function must handle a single group at a time."

        matched_parameter = next(iter(match.groups()))
        assert isinstance(matched_parameter, bytes)

        if b":" in matched_parameter:
            assert matched_parameter.count(b":") == 1

            raw_pattern_name, parameter_name = matched_parameter.split(b":")
            parameter_pattern_name = raw_pattern_name.decode()
            parameter_pattern = Route.value_patterns.get(parameter_pattern_name)

            if not parameter_pattern:
                raise InvalidValuePatternName(
                    parameter_pattern_name,
                    matched_parameter.decode("utf8"),
                )

            return _get_parameter_pattern_fragment(
                parameter_name, parameter_pattern.encode()
            )
        return _get_parameter_pattern_fragment(matched_parameter)

    def normalize_pattern(self, pattern: Union[str, bytes]) -> bytes:
        if isinstance(pattern, str):
            raw_pattern = pattern.encode("utf8")
        else:
            raw_pattern = pattern

        if raw_pattern == b"":
            raw_pattern = b"/"
        if len(raw_pattern) > 1 and raw_pattern.endswith(b"/"):
            raw_pattern = raw_pattern.rstrip(b"/")

        return raw_pattern.lower()

    def __repr__(self) -> str:
        return f"<Route {self.pattern.decode('utf8')}>"

    @property
    def mustache_pattern(self) -> str:
        return _route_param_rx.sub(br"/{\1}", self.pattern).decode("utf8")

    @property
    def full_pattern(self) -> bytes:
        return self._rx.pattern

    def match(self, value: bytes) -> Optional[RouteMatch]:
        if not self.has_params and value.lower() == self.pattern:
            return RouteMatch(self, None)

        match = self._rx.match(value)

        if not match:
            return None

        return RouteMatch(self, match.groupdict() if self.has_params else None)


class RouterBase:
    @abstractmethod
    def add(self, method: str, pattern: str, handler: Callable) -> None:
        """Adds a request handler for the given HTTP method and route pattern."""

    def mark_handler(self, handler: Callable) -> None:
        setattr(handler, "route_handler", True)

    def normalize_default_pattern_name(self, handler_name: str) -> str:
        return handler_name.replace("_", "-")

    def get_decorator(
        self, method: str, pattern: Optional[str] = "/"
    ) -> Callable[..., Any]:
        def decorator(fn):
            nonlocal pattern
            if pattern is ... or pattern is None:
                # default to something depending on decorated function's name
                if fn.__name__ in {"index", "default"}:
                    pattern = "/"
                else:
                    pattern = "/" + self.normalize_default_pattern_name(fn.__name__)

                logging.debug(
                    "Defaulting to route pattern '%s' for" "request handler <%s>",
                    pattern,
                    fn.__qualname__,
                )
            self.add(method, pattern, fn)
            return fn

        return decorator

    def add_head(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.HEAD, pattern, handler)

    def add_get(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.GET, pattern, handler)

    def add_post(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.POST, pattern, handler)

    def add_put(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.PUT, pattern, handler)

    def add_delete(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.DELETE, pattern, handler)

    def add_trace(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.TRACE, pattern, handler)

    def add_options(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.OPTIONS, pattern, handler)

    def add_connect(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.CONNECT, pattern, handler)

    def add_patch(self, pattern: str, handler: Callable[..., Any]) -> None:
        self.add(HTTPMethod.PATCH, pattern, handler)

    def head(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.HEAD, pattern)

    def get(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.GET, pattern)

    def post(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.POST, pattern)

    def put(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.PUT, pattern)

    def delete(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.DELETE, pattern)

    def trace(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.TRACE, pattern)

    def options(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.OPTIONS, pattern)

    def connect(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.CONNECT, pattern)

    def patch(self, pattern: Optional[str] = "/") -> Callable[..., Any]:
        return self.get_decorator(HTTPMethod.PATCH, pattern)


class Router(RouterBase):

    __slots__ = ("routes", "_map", "_fallback")

    def __init__(self):
        self._map = {}
        self._fallback = None
        self.routes: Dict[bytes, List[Route]] = defaultdict(list)

    @property
    def fallback(self):
        return self._fallback

    @fallback.setter
    def fallback(self, value):
        if not isinstance(value, Route):
            if callable(value):
                self._fallback = Route(b"*", value)
                return
            raise ValueError("fallback must be a Route or a callable")
        self._fallback = value

    def __iter__(self):
        for _, routes in self.routes.items():
            for route in routes:
                yield route
        if self._fallback:
            yield self._fallback

    def _is_route_configured(self, method: bytes, route: Route):
        method_patterns = self._map.get(method)
        if not method_patterns:
            return False
        if method_patterns.get(route.full_pattern):
            return True
        return False

    def _set_configured_route(self, method: bytes, route: Route):
        method_patterns = self._map.get(method)
        if not method_patterns:
            self._map[method] = {route.full_pattern: route}
        else:
            method_patterns[route.full_pattern] = route

    def _check_duplicate(self, method: bytes, new_route: Route):
        if self._is_route_configured(method, new_route):
            current_route = self._map.get(method).get(new_route.full_pattern)
            raise RouteDuplicate(method, new_route.pattern, current_route.handler)
        self._set_configured_route(method, new_route)

    def add(self, method: str, pattern: AnyStr, handler: Any):
        self.mark_handler(handler)
        method_name = ensure_bytes(method)
        new_route = Route(ensure_bytes(pattern), handler)
        self._check_duplicate(method_name, new_route)
        self.add_route(method_name, new_route)

    def add_route(self, method: AnyStr, route: Route):
        self.routes[ensure_bytes(method)].append(route)

    def sort_routes(self):
        """
        Sorts the current routes in order of dynamic parameters ascending.
        The catch-all route is always placed to the end.
        """
        current_routes = self.routes.copy()

        for method in current_routes.keys():
            current_routes[method].sort(key=lambda route: -route.pattern.count(b"/"))
            current_routes[method].sort(key=lambda route: len(route.param_names))
            current_routes[method].sort(key=lambda route: b".*" in route.rx.pattern)
            current_routes[method].sort(
                key=lambda route: b"*" == route.pattern or b"/*" == route.pattern
            )

        self.routes = current_routes

    @lru_cache(maxsize=1200)
    def get_match(self, method: AnyStr, value: AnyStr) -> Optional[RouteMatch]:
        for route in self.routes[ensure_bytes(method)]:
            match = route.match(ensure_bytes(value))
            if match:
                return match
        if self._fallback is None:
            return None

        return RouteMatch(self._fallback, None)

    @lru_cache(maxsize=1200)
    def get_matching_route(self, method: AnyStr, value: AnyStr) -> Optional[Route]:
        for route in self.routes[ensure_bytes(method)]:
            match = route.match(ensure_bytes(value))
            if match:
                return route
        return None


class RegisteredRoute:

    __slots__ = ("method", "pattern", "handler")

    def __init__(self, method: str, pattern: str, handler: Callable):
        self.method = method
        self.pattern = pattern
        self.handler = handler


class RoutesRegistry(RouterBase):
    """
    A registry for routes: not a full router able to get matches.
    Unlike a router, a registry does not throw for duplicated routes;
    because such routes can be modified when applied to an actual router.

    This class is meant to enable scenarios like base pattern for controllers.
    """

    def __init__(self):
        self.routes: List[RegisteredRoute] = []

    def __iter__(self):
        yield from self.routes

    def add(self, method: str, pattern: str, handler: Callable):
        self.mark_handler(handler)
        self.routes.append(RegisteredRoute(method, pattern, handler))
