# Set of helper functions to manipulate the OpenAPI files that define our REST
# API's specification.
import os
import re
from typing import Any, Dict, List, Optional, Set

from openapi_core import create_spec
from openapi_core.testing import MockRequest
from openapi_core.validation.request.validators import RequestValidator
from openapi_schema_validator import OAS30Validator

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 = {
    ("/settings/notifications", "patch"),
}

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._request_validator: Optional[RequestValidator] = None

    def check_reload(self) -> None:
        # Because importing yamole (and in turn, 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.
        from yamole import YamoleParser

        mtime = os.path.getmtime(self.openapi_path)
        # Using == rather than >= to cover the corner case of users placing an
        # earlier version than the current one
        if self.mtime == mtime:
            return

        with open(self.openapi_path) as f:
            yamole_parser = YamoleParser(f)
        self._openapi = yamole_parser.data
        spec = create_spec(self._openapi)
        self._request_validator = RequestValidator(spec)
        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 request_validator(self) -> RequestValidator:
        """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._request_validator is not None
        return self._request_validator

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_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_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) -> List[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 validate_against_openapi_schema(content: Dict[str, Any], path: str,
                                    method: str, status_code: str) -> 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() != 'success'):
        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
    # The actual work of validating that the response matches the
    # schema is done via the third-party OAS30Validator.
    schema = get_schema(endpoint, method, status_code)
    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)
    validator = OAS30Validator(schema)
    validator.validate(content)
    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', dict()).values():
            validate_schema(property_schema)
        if schema['additionalProperties']:
            validate_schema(schema['additionalProperties'])

def to_python_type(py_type: str) -> type:
    """Transform an OpenAPI-like type to a Python one.
    https://swagger.io/docs/specification/data-models/data-types
    """
    TYPES = {
        'string': str,
        'number': float,
        'integer': int,
        'boolean': bool,
        'array': list,
        'object': dict,
    }

    return TYPES[py_type]

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

    return "**Deprecated**" in 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: Dict[str, Any],
                     http_headers: Dict[str, Any], 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.
    mock_request = MockRequest('http://localhost:9991/', method, '/api/v1' + url,
                               headers=http_headers, args=data)
    result = openapi_spec.request_validator().validate(mock_request)
    if len(result.errors) != 0:
        # 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

    # If no errors are raised, then validation is successful
    if len(result.errors) == 0:
        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 result.errors:
        msg += f"* {str(error)}\n"
    raise SchemaError(msg)