# Zulip's OpenAPI-based API documentation system is documented at
#   https://zulip.readthedocs.io/en/latest/documentation/api.html
#
# This file contains helper functions to interact with the OpenAPI
# definitions and validate that Zulip's implementation matches what is
# described in our documentation.

import json
import os
import re
from typing import Any, Dict, List, Mapping, Optional, Set, Tuple, Union

import orjson
from jsonschema.exceptions import ValidationError as JsonSchemaValidationError
from openapi_core import Spec
from openapi_core.testing import MockRequest, MockResponse
from openapi_core.unmarshalling.schemas.exceptions import InvalidSchemaValue
from openapi_core.validation.request import openapi_request_validator
from openapi_core.validation.response import openapi_response_validator

OPENAPI_SPEC_PATH = os.path.abspath(
    os.path.join(os.path.dirname(__file__), "../openapi/zulip.yaml")
)

# A list of endpoint-methods such that the endpoint
# has documentation but not with this particular method.
EXCLUDE_UNDOCUMENTED_ENDPOINTS = {
    ("/realm/emoji/{emoji_name}", "delete"),
    ("/users", "patch"),
}
# Consists of endpoints with some documentation remaining.
# These are skipped but return true as the validator cannot exclude objects
EXCLUDE_DOCUMENTED_ENDPOINTS: Set[Tuple[str, str]] = set()


# Most of our code expects allOf to be preprocessed away because that is what
# yamole did.  Its algorithm for doing so is not standards compliant, but we
# replicate it here.
def naively_merge(a: Dict[str, object], b: Dict[str, object]) -> Dict[str, object]:
    ret: Dict[str, object] = a.copy()
    for key, b_value in b.items():
        if key == "example" or key not in ret:
            ret[key] = b_value
            continue
        a_value = ret[key]
        if isinstance(b_value, list):
            assert isinstance(a_value, list)
            ret[key] = a_value + b_value
        elif isinstance(b_value, dict):
            assert isinstance(a_value, dict)
            ret[key] = naively_merge(a_value, b_value)
    return ret


def naively_merge_allOf(obj: object) -> object:
    if isinstance(obj, dict):
        return naively_merge_allOf_dict(obj)
    elif isinstance(obj, list):
        return list(map(naively_merge_allOf, obj))
    else:
        return obj


def naively_merge_allOf_dict(obj: Dict[str, object]) -> Dict[str, object]:
    if "allOf" in obj:
        ret = obj.copy()
        subschemas = ret.pop("allOf")
        ret = naively_merge_allOf_dict(ret)
        assert isinstance(subschemas, list)
        for subschema in subschemas:
            assert isinstance(subschema, dict)
            ret = naively_merge(ret, naively_merge_allOf_dict(subschema))
        return ret
    return {key: naively_merge_allOf(value) for key, value in obj.items()}


class OpenAPISpec:
    def __init__(self, openapi_path: str) -> None:
        self.openapi_path = openapi_path
        self.mtime: Optional[float] = None
        self._openapi: Dict[str, Any] = {}
        self._endpoints_dict: Dict[str, str] = {}
        self._spec: Optional[Spec] = None

    def check_reload(self) -> None:
        # Because importing yaml takes significant time, and we only
        # use python-yaml for our API docs, importing it lazily here
        # is a significant optimization to `manage.py` startup.
        #
        # There is a bit of a race here...we may have two processes
        # accessing this module level object and both trying to
        # populate self.data at the same time.  Hopefully this will
        # only cause some extra processing at startup and not data
        # corruption.

        import yaml
        from jsonref import JsonRef

        with open(self.openapi_path) as f:
            mtime = os.fstat(f.fileno()).st_mtime
            # Using == rather than >= to cover the corner case of users placing an
            # earlier version than the current one
            if self.mtime == mtime:
                return

            openapi = yaml.load(f, Loader=yaml.CSafeLoader)

        spec = Spec.create(openapi)
        self._spec = spec
        self._openapi = naively_merge_allOf_dict(JsonRef.replace_refs(openapi))
        self.create_endpoints_dict()
        self.mtime = mtime

    def create_endpoints_dict(self) -> None:
        # Algorithm description:
        # We have 2 types of endpoints
        # 1.with path arguments 2. without path arguments
        # In validate_against_openapi_schema we directly check
        # if we have a without path endpoint, since it does not
        # require regex. Hence they are not part of the regex dict
        # and now we are left with only:
        # endpoint with path arguments.
        # Now for this case, the regex has been created carefully,
        # numeric arguments are matched with [0-9] only and
        # emails are matched with their regex. This is why there are zero
        # collisions. Hence if this regex matches
        # an incorrect endpoint then there is some backend problem.
        # For example if we have users/{name}/presence then it will
        # conflict with users/me/presence even in the backend.
        # Care should be taken though that if we have special strings
        # such as email they must be substituted with proper regex.

        email_regex = r"([a-zA-Z0-9_\-\.]+)@([a-zA-Z0-9_\-\.]+)\.([a-zA-Z]{2,5})"
        self._endpoints_dict = {}
        for endpoint in self._openapi["paths"]:
            if "{" not in endpoint:
                continue
            path_regex = "^" + endpoint + "$"
            # Numeric arguments have id at their end
            # so find such arguments and replace them with numeric
            # regex
            path_regex = re.sub(r"{[^}]*id}", r"[0-9]*", path_regex)
            # Email arguments end with email
            path_regex = re.sub(r"{[^}]*email}", email_regex, path_regex)
            # All other types of arguments are supposed to be
            # all-encompassing string.
            path_regex = re.sub(r"{[^}]*}", r"[^\/]*", path_regex)
            path_regex = path_regex.replace(r"/", r"\/")
            self._endpoints_dict[path_regex] = endpoint

    def openapi(self) -> Dict[str, Any]:
        """Reload the OpenAPI file if it has been modified after the last time
        it was read, and then return the parsed data.
        """
        self.check_reload()
        assert len(self._openapi) > 0
        return self._openapi

    def endpoints_dict(self) -> Dict[str, str]:
        """Reload the OpenAPI file if it has been modified after the last time
        it was read, and then return the parsed data.
        """
        self.check_reload()
        assert len(self._endpoints_dict) > 0
        return self._endpoints_dict

    def spec(self) -> Spec:
        """Reload the OpenAPI file if it has been modified after the last time
        it was read, and then return the openapi_core validator object. Similar
        to preceding functions. Used for proper access to OpenAPI objects.
        """
        self.check_reload()
        assert self._spec is not None
        return self._spec


class SchemaError(Exception):
    pass


openapi_spec = OpenAPISpec(OPENAPI_SPEC_PATH)


def get_schema(endpoint: str, method: str, status_code: str) -> Dict[str, Any]:
    if len(status_code) == 3 and (
        "oneOf"
        in openapi_spec.openapi()["paths"][endpoint][method.lower()]["responses"][status_code][
            "content"
        ]["application/json"]["schema"]
    ):
        # Currently at places where multiple schemas are defined they only
        # differ in example so either can be used.
        status_code += "_0"
    if len(status_code) == 3:
        schema = openapi_spec.openapi()["paths"][endpoint][method.lower()]["responses"][
            status_code
        ]["content"]["application/json"]["schema"]
        return schema
    else:
        subschema_index = int(status_code[4])
        status_code = status_code[0:3]
        schema = openapi_spec.openapi()["paths"][endpoint][method.lower()]["responses"][
            status_code
        ]["content"]["application/json"]["schema"]["oneOf"][subschema_index]
        return schema


def get_openapi_fixture(endpoint: str, method: str, status_code: str = "200") -> Dict[str, Any]:
    """Fetch a fixture from the full spec object."""
    return get_schema(endpoint, method, status_code)["example"]


def get_openapi_fixture_description(endpoint: str, method: str, status_code: str = "200") -> str:
    """Fetch a fixture from the full spec object."""
    return get_schema(endpoint, method, status_code)["description"]


def get_curl_include_exclude(endpoint: str, method: str) -> List[Dict[str, Any]]:
    """Fetch all the kinds of parameters required for curl examples."""
    if (
        "x-curl-examples-parameters"
        not in openapi_spec.openapi()["paths"][endpoint][method.lower()]
    ):
        return [{"type": "exclude", "parameters": {"enum": [""]}}]
    return openapi_spec.openapi()["paths"][endpoint][method.lower()]["x-curl-examples-parameters"][
        "oneOf"
    ]


def check_requires_administrator(endpoint: str, method: str) -> bool:
    """Fetch if the endpoint requires admin config."""
    return openapi_spec.openapi()["paths"][endpoint][method.lower()].get(
        "x-requires-administrator", False
    )


def check_additional_imports(endpoint: str, method: str) -> Optional[List[str]]:
    """Fetch the additional imports required for an endpoint."""
    return openapi_spec.openapi()["paths"][endpoint][method.lower()].get(
        "x-python-examples-extra-imports", None
    )


def get_responses_description(endpoint: str, method: str) -> str:
    """Fetch responses description of an endpoint."""
    return openapi_spec.openapi()["paths"][endpoint][method.lower()].get(
        "x-response-description", ""
    )


def get_parameters_description(endpoint: str, method: str) -> str:
    """Fetch parameters description of an endpoint."""
    return openapi_spec.openapi()["paths"][endpoint][method.lower()].get(
        "x-parameter-description", ""
    )


def generate_openapi_fixture(endpoint: str, method: str) -> List[str]:
    """Generate fixture to be rendered"""
    fixture = []
    for status_code in sorted(
        openapi_spec.openapi()["paths"][endpoint][method.lower()]["responses"]
    ):
        if (
            "oneOf"
            in openapi_spec.openapi()["paths"][endpoint][method.lower()]["responses"][status_code][
                "content"
            ]["application/json"]["schema"]
        ):
            subschema_count = len(
                openapi_spec.openapi()["paths"][endpoint][method.lower()]["responses"][status_code][
                    "content"
                ]["application/json"]["schema"]["oneOf"]
            )
        else:
            subschema_count = 1
        for subschema_index in range(subschema_count):
            if subschema_count != 1:
                subschema_status_code = status_code + "_" + str(subschema_index)
            else:
                subschema_status_code = status_code
            fixture_dict = get_openapi_fixture(endpoint, method, subschema_status_code)
            fixture_description = get_openapi_fixture_description(
                endpoint, method, subschema_status_code
            ).strip()
            fixture_json = json.dumps(
                fixture_dict, indent=4, sort_keys=True, separators=(",", ": ")
            )

            fixture.extend(fixture_description.splitlines())
            fixture.append("``` json")
            fixture.extend(fixture_json.splitlines())
            fixture.append("```")
    return fixture


def get_openapi_description(endpoint: str, method: str) -> str:
    """Fetch a description from the full spec object."""
    return openapi_spec.openapi()["paths"][endpoint][method.lower()]["description"]


def get_openapi_summary(endpoint: str, method: str) -> str:
    """Fetch a summary from the full spec object."""
    return openapi_spec.openapi()["paths"][endpoint][method.lower()]["summary"]


def get_endpoint_from_operationid(operationid: str) -> Tuple[str, str]:
    for endpoint in openapi_spec.openapi()["paths"]:
        for method in openapi_spec.openapi()["paths"][endpoint]:
            operationId = openapi_spec.openapi()["paths"][endpoint][method].get("operationId")
            if operationId == operationid:
                return (endpoint, method)
    raise AssertionError("No such page exists in OpenAPI data.")


def get_openapi_paths() -> Set[str]:
    return set(openapi_spec.openapi()["paths"].keys())


def get_openapi_parameters(
    endpoint: str, method: str, include_url_parameters: bool = True
) -> List[Dict[str, Any]]:
    operation = openapi_spec.openapi()["paths"][endpoint][method.lower()]
    # We do a `.get()` for this last bit to distinguish documented
    # endpoints with no parameters (empty list) from undocumented
    # endpoints (KeyError exception).
    parameters = operation.get("parameters", [])
    # Also, we skip parameters defined in the URL.
    if not include_url_parameters:
        parameters = [parameter for parameter in parameters if parameter["in"] != "path"]
    return parameters


def get_openapi_return_values(endpoint: str, method: str) -> Dict[str, Any]:
    operation = openapi_spec.openapi()["paths"][endpoint][method.lower()]
    schema = operation["responses"]["200"]["content"]["application/json"]["schema"]
    # In cases where we have used oneOf, the schemas only differ in examples
    # So we can choose any.
    if "oneOf" in schema:
        schema = schema["oneOf"][0]
    return schema["properties"]


def find_openapi_endpoint(path: str) -> Optional[str]:
    for path_regex, endpoint in openapi_spec.endpoints_dict().items():
        matches = re.match(path_regex, path)
        if matches:
            return endpoint
    return None


def get_event_type(event: Dict[str, Any]) -> str:
    return event["type"] + ":" + event.get("op", "")


def fix_events(content: Dict[str, Any]) -> None:
    """Remove undocumented events from events array. This is a makeshift
    function so that further documentation of `/events` can happen with
    only zulip.yaml changes and minimal other changes. It should be removed
    as soon as `/events` documentation is complete.
    """
    # 'user' is deprecated so remove its occurrences from the events array
    for event in content["events"]:
        event.pop("user", None)


def prune_type_schema_by_type(schema: Dict[str, Any], type: str) -> bool:
    return ("enum" in schema and type not in schema["enum"]) or (
        "allOf" in schema
        and any(prune_type_schema_by_type(subschema, type) for subschema in schema["allOf"])
    )


def prune_schema_by_type(schema: Dict[str, Any], type: str) -> bool:
    return (
        "properties" in schema
        and "type" in schema["properties"]
        and prune_type_schema_by_type(schema["properties"]["type"], type)
    ) or (
        "allOf" in schema
        and any(prune_schema_by_type(subschema, type) for subschema in schema["allOf"])
    )


def validate_against_openapi_schema(
    content: Dict[str, Any],
    path: str,
    method: str,
    status_code: str,
    display_brief_error: bool = False,
) -> bool:
    """Compare a "content" dict with the defined schema for a specific method
    in an endpoint. Return true if validated and false if skipped.
    """

    # This first set of checks are primarily training wheels that we
    # hope to eliminate over time as we improve our API documentation.

    # No 500 responses have been documented, so skip them
    if status_code.startswith("5"):
        return False
    if path not in openapi_spec.openapi()["paths"].keys():
        endpoint = find_openapi_endpoint(path)
        # If it doesn't match it hasn't been documented yet.
        if endpoint is None:
            return False
    else:
        endpoint = path
    # Excluded endpoint/methods
    if (endpoint, method) in EXCLUDE_UNDOCUMENTED_ENDPOINTS:
        return False
    # Return true for endpoints with only response documentation remaining
    if (endpoint, method) in EXCLUDE_DOCUMENTED_ENDPOINTS:
        return True
    # Check if the response matches its code
    if status_code.startswith("2") and (
        content.get("result", "success").lower() not in ["success", "partially_completed"]
    ):
        raise SchemaError("Response is not 200 but is validating against 200 schema")
    # Code is not declared but appears in various 400 responses. If
    # common, it can be added to 400 response schema
    if status_code.startswith("4"):
        # This return statement should ideally be not here. But since
        # we have not defined 400 responses for various paths this has
        # been added as all 400 have the same schema.  When all 400
        # response have been defined this should be removed.
        return True

    if endpoint == "/events" and method == "get":
        # This a temporary function for checking only documented events
        # as all events haven't been documented yet.
        # TODO: Remove this after all events have been documented.
        fix_events(content)

    mock_request = MockRequest("http://localhost:9991/", method, "/api/v1" + path)
    mock_response = MockResponse(
        # TODO: Use original response content instead of re-serializing it.
        orjson.dumps(content).decode(),
        status_code=int(status_code),
    )
    result = openapi_response_validator.validate(openapi_spec.spec(), mock_request, mock_response)
    try:
        result.raise_for_errors()
    except InvalidSchemaValue as isv:
        schema_errors = list(isv.schema_errors)
        message = f"{len(schema_errors)} response validation error(s) at {method} /api/v1{path} ({status_code}):"
        for error in schema_errors:
            if display_brief_error and isinstance(error, JsonSchemaValidationError):
                # display_brief_error is designed to avoid printing 1000 lines
                # of output when the schema to validate is extremely large
                # (E.g. the several dozen format variants for individual
                # events returned by GET /events) and instead just display the
                # specific variant we expect to match the response.
                brief_error_validator_value = [
                    validator_value
                    for validator_value in error.validator_value
                    if not prune_schema_by_type(validator_value, error.instance["type"])
                ]
                brief_error_display_schema = error.schema.copy()
                if "oneOf" in brief_error_display_schema:
                    brief_error_display_schema["oneOf"] = [
                        i_schema
                        for i_schema in error.schema["oneOf"]
                        if not prune_schema_by_type(i_schema, error.instance["type"])
                    ]

                # Field list from https://python-jsonschema.readthedocs.io/en/stable/errors/
                error = JsonSchemaValidationError(
                    message=error.message,
                    validator=error.validator,
                    path=error.path,
                    instance=error.instance,
                    schema_path=error.schema_path,
                    schema=brief_error_display_schema,
                    validator_value=brief_error_validator_value,
                    cause=error.cause,
                )
            # Some endpoints have long, descriptive OpenAPI schemas
            # which, when printed to the console, do not assist with
            # debugging, so we omit some of the error information.
            if path in ["/register"] and isinstance(error, JsonSchemaValidationError):
                error.schema = "OpenAPI schema omitted due to length of output."
                if len(error.instance) > 100:
                    error.instance = "Error instance omitted due to length of output."
            message += f"\n\n{type(error).__name__}: {error}"
        message += (
            "\n\nFor help debugging these errors see: "
            "https://zulip.readthedocs.io/en/latest/documentation/api.html#debugging-schema-validation-errors"
        )
        raise SchemaError(message) from None

    return True


def validate_schema(schema: Dict[str, Any]) -> None:
    """Check if opaque objects are present in the OpenAPI spec; this is an
    important part of our policy for ensuring every detail of Zulip's
    API responses is correct.

    This is done by checking for the presence of the
    `additionalProperties` attribute for all objects (dictionaries).
    """
    if "oneOf" in schema:
        for subschema in schema["oneOf"]:
            validate_schema(subschema)
    elif schema["type"] == "array":
        validate_schema(schema["items"])
    elif schema["type"] == "object":
        if "additionalProperties" not in schema:
            raise SchemaError(
                "additionalProperties needs to be defined for objects to make sure they have no"
                " additional properties left to be documented."
            )
        for property_schema in schema.get("properties", {}).values():
            validate_schema(property_schema)
        if schema["additionalProperties"]:
            validate_schema(schema["additionalProperties"])


def likely_deprecated_parameter(parameter_description: str) -> bool:
    if "**Changes**: Deprecated" in parameter_description:
        return True

    return "**Deprecated**" in parameter_description


def check_deprecated_consistency(argument: Mapping[str, Any], description: str) -> None:
    # Test to make sure deprecated parameters are marked so.
    if likely_deprecated_parameter(description):
        assert argument["deprecated"]
    if "deprecated" in argument:
        assert likely_deprecated_parameter(description)


# Skip those JSON endpoints whose query parameters are different from
# their `/api/v1` counterpart.  This is a legacy code issue that we
# plan to fix by changing the implementation.
SKIP_JSON = {
    ("/fetch_api_key", "post"),
}


def validate_request(
    url: str,
    method: str,
    data: Union[str, bytes, Mapping[str, Any]],
    http_headers: Dict[str, str],
    json_url: bool,
    status_code: str,
    intentionally_undocumented: bool = False,
) -> None:
    # Some JSON endpoints have different parameters compared to
    # their `/api/v1` counterparts.
    if json_url and (url, method) in SKIP_JSON:
        return

    # TODO: Add support for file upload endpoints that lack the /json/
    # or /api/v1/ prefix.
    if url == "/user_uploads" or url.startswith("/realm/emoji/"):
        return

    # Now using the openapi_core APIs, validate the request schema
    # against the OpenAPI documentation.
    assert isinstance(data, dict)
    mock_request = MockRequest(
        "http://localhost:9991/", method, "/api/v1" + url, headers=http_headers, args=data
    )
    result = openapi_request_validator.validate(openapi_spec.spec(), mock_request)
    errors = list(result.errors)

    # If no errors are raised, then validation is successful
    if not errors:
        return

    # Requests that do not validate against the OpenAPI spec must either:
    # * Have returned a 400 (bad request) error
    # * Have returned a 200 (success) with this request marked as intentionally
    # undocumented behavior.
    if status_code.startswith("4"):
        return
    if status_code.startswith("2") and intentionally_undocumented:
        return

    # Show a block error message explaining the options for fixing it.
    msg = f"""

Error!  The OpenAPI schema for {method} {url} is not consistent
with the parameters passed in this HTTP request.  Consider:

* Updating the OpenAPI schema defined in zerver/openapi/zulip.yaml
* Adjusting the test to pass valid parameters.  If the test
  fails due to intentionally_undocumented features, you need to pass
  `intentionally_undocumented=True` to self.client_{method.lower()} or
  self.api_{method.lower()} to document your intent.

See https://zulip.readthedocs.io/en/latest/documentation/api.html for help.

The errors logged by the OpenAPI validator are below:\n"""
    for error in errors:
        msg += f"* {str(error)}\n"
    raise SchemaError(msg)