import datetime
import re
from base64 import b64decode
from typing import Any, List, Optional, Tuple

import xmltodict

from moto.core.base_backend import BackendDict, BaseBackend
from moto.core.common_models import BaseModel
from moto.core.utils import utcnow
from moto.iam.models import AccessKey, iam_backends
from moto.sts.utils import (
    DEFAULT_STS_SESSION_DURATION,
    random_assumed_role_id,
    random_session_token,
)
from moto.utilities.utils import ARN_PARTITION_REGEX, PARTITION_NAMES, get_partition


class Token(BaseModel):
    def __init__(self, duration: int, name: Optional[str] = None):
        now = utcnow()
        self.expiration = now + datetime.timedelta(seconds=duration)
        self.name = name
        self.policy = None


class AssumedRole(BaseModel):
    def __init__(
        self,
        account_id: str,
        region_name: str,
        access_key: AccessKey,
        role_session_name: str,
        role_arn: str,
        policy: str,
        duration: int,
        external_id: str,
    ):
        self.account_id = account_id
        self.region_name = region_name
        self.session_name = role_session_name
        self.role_arn = role_arn
        self.policy = policy
        now = utcnow()
        self.expiration = now + datetime.timedelta(seconds=duration)
        self.external_id = external_id
        self.access_key = access_key
        self.access_key_id = access_key.access_key_id
        self.secret_access_key = access_key.secret_access_key
        self.session_token = random_session_token()
        self.partition = get_partition(region_name)

    @property
    def user_id(self) -> str:
        iam_backend = iam_backends[self.account_id][self.partition]
        try:
            role_id = iam_backend.get_role_by_arn(arn=self.role_arn).id
        except Exception:
            role_id = "AROA" + random_assumed_role_id()
        return role_id + ":" + self.session_name

    @property
    def arn(self) -> str:
        partition = get_partition(self.region_name)
        return f"arn:{partition}:sts::{self.account_id}:assumed-role/{self.role_arn.split('/')[-1]}/{self.session_name}"


class STSBackend(BaseBackend):
    def __init__(self, region_name: str, account_id: str):
        super().__init__(region_name, account_id)
        self.assumed_roles: List[AssumedRole] = []

    def get_session_token(self, duration: int) -> Token:
        return Token(duration=duration)

    def get_federation_token(self, name: Optional[str], duration: int) -> Token:
        return Token(duration=duration, name=name)

    def assume_role(
        self,
        region_name: str,
        role_session_name: str,
        role_arn: str,
        policy: str,
        duration: int,
        external_id: str,
    ) -> AssumedRole:
        """
        Assume an IAM Role. Note that the role does not need to exist. The ARN can point to another account, providing an opportunity to switch accounts.
        """
        account_id, access_key = self._create_access_key(role=role_arn)
        role = AssumedRole(
            account_id=account_id,
            region_name=region_name,
            access_key=access_key,
            role_session_name=role_session_name,
            role_arn=role_arn,
            policy=policy,
            duration=duration,
            external_id=external_id,
        )
        access_key.role_arn = role_arn
        account_backend = sts_backends[account_id][get_partition(region_name)]
        account_backend.assumed_roles.append(role)
        return role

    def get_assumed_role_from_access_key(
        self, access_key_id: str
    ) -> Optional[AssumedRole]:
        for assumed_role in self.assumed_roles:
            if assumed_role.access_key_id == access_key_id:
                return assumed_role
        return None

    def assume_role_with_web_identity(self, **kwargs: Any) -> AssumedRole:
        return self.assume_role(**kwargs)

    def assume_role_with_saml(self, **kwargs: Any) -> AssumedRole:
        del kwargs["principal_arn"]
        saml_assertion_encoded = kwargs.pop("saml_assertion")
        saml_assertion_decoded = b64decode(saml_assertion_encoded)

        namespaces = {
            "urn:oasis:names:tc:SAML:2.0:protocol": "samlp",
            "urn:oasis:names:tc:SAML:2.0:assertion": "saml",
        }
        saml_assertion = xmltodict.parse(
            saml_assertion_decoded.decode("utf-8"),
            force_cdata=True,
            process_namespaces=True,
            namespaces=namespaces,
            namespace_separator="|",
        )

        target_role = None
        saml_assertion_attributes = saml_assertion["samlp|Response"]["saml|Assertion"][
            "saml|AttributeStatement"
        ]["saml|Attribute"]
        for attribute in saml_assertion_attributes:
            if (
                attribute["@Name"]
                == "https://aws.amazon.com/SAML/Attributes/RoleSessionName"
            ):
                kwargs["role_session_name"] = attribute["saml|AttributeValue"]["#text"]
            if (
                attribute["@Name"]
                == "https://aws.amazon.com/SAML/Attributes/SessionDuration"
            ):
                kwargs["duration"] = int(attribute["saml|AttributeValue"]["#text"])
            if attribute["@Name"] == "https://aws.amazon.com/SAML/Attributes/Role":
                target_role = attribute["saml|AttributeValue"]["#text"].split(",")[0]

        if "duration" not in kwargs:
            kwargs["duration"] = DEFAULT_STS_SESSION_DURATION

        account_id, access_key = self._create_access_key(role=target_role)  # type: ignore
        kwargs["account_id"] = account_id
        kwargs["region_name"] = self.region_name
        kwargs["access_key"] = access_key

        kwargs["external_id"] = None
        kwargs["policy"] = None
        role = AssumedRole(**kwargs)
        self.assumed_roles.append(role)
        return role

    def get_caller_identity(
        self, access_key_id: str, region: str
    ) -> Tuple[str, str, str]:
        assumed_role = self.get_assumed_role_from_access_key(access_key_id)
        if assumed_role:
            return assumed_role.user_id, assumed_role.arn, assumed_role.account_id

        iam_backend = iam_backends[self.account_id][self.partition]
        user = iam_backend.get_user_from_access_key_id(access_key_id)
        if user:
            return user.id, user.arn, user.account_id

        # Default values in case the request does not use valid credentials generated by moto
        partition = get_partition(region)
        user_id = "AKIAIOSFODNN7EXAMPLE"
        arn = f"arn:{partition}:sts::{self.account_id}:user/moto"
        return user_id, arn, self.account_id

    def _create_access_key(self, role: str) -> Tuple[str, AccessKey]:
        account_id_match = re.search(ARN_PARTITION_REGEX + r":iam::([0-9]+).+", role)
        if account_id_match:
            account_id = account_id_match.group(2)
        else:
            account_id = self.account_id
        iam_backend = iam_backends[account_id][self.partition]
        return account_id, iam_backend.create_temp_access_key()


sts_backends = BackendDict(
    STSBackend, "sts", use_boto3_regions=False, additional_regions=PARTITION_NAMES
)
