'''
This module sets up a scheme for validating that arbitrary Python
objects are correctly typed.  It is totally decoupled from Django,
composable, easily wrapped, and easily extended.

A validator takes two parameters--var_name and val--and raises an
error if val is not the correct type.  The var_name parameter is used
to format error messages.  Validators return the validated value when
there are no errors.

Example primitive validators are check_string, check_int, and check_bool.

Compound validators are created by check_list and check_dict.  Note that
those functions aren't directly called for validation; instead, those
functions are called to return other functions that adhere to the validator
contract.  This is similar to how Python decorators are often parameterized.

The contract for check_list and check_dict is that they get passed in other
validators to apply to their items.  This allows you to build up validators
for arbitrarily complex validators.  See ValidatorTestCase for example usage.

A simple example of composition is this:

   check_list(check_string)('my_list', ['a', 'b', 'c'])

To extend this concept, it's simply a matter of writing your own validator
for any particular type of object.

'''
import re
from datetime import datetime
from typing import (
    Any,
    Callable,
    Dict,
    Iterable,
    List,
    Optional,
    Set,
    Tuple,
    TypeVar,
    Union,
    cast,
    overload,
)

import ujson
from django.conf import settings
from django.core.exceptions import ValidationError
from django.core.validators import URLValidator, validate_email
from django.utils.translation import ugettext as _

from zerver.lib.request import JsonableError, ResultT
from zerver.lib.types import ProfileFieldData, Validator

FuncT = Callable[..., Any]
TypeStructure = TypeVar("TypeStructure")

USING_TYPE_STRUCTURE = settings.LOG_API_EVENT_TYPES

# The type_structure system is designed to support using the validators in
# test_events.py to create documentation for our event formats.
#
# Ultimately, it should be possible to do this with mypy rather than a
# parallel system.
def set_type_structure(type_structure: TypeStructure) -> Callable[[FuncT], Any]:
    def _set_type_structure(func: FuncT) -> FuncT:
        if USING_TYPE_STRUCTURE:
            func.type_structure = type_structure  # type: ignore[attr-defined] # monkey-patching
        return func
    return _set_type_structure

@set_type_structure("str")
def check_string(var_name: str, val: object) -> str:
    if not isinstance(val, str):
        raise ValidationError(_('{var_name} is not a string').format(var_name=var_name))
    return val

@set_type_structure("str")
def check_required_string(var_name: str, val: object) -> str:
    s = check_string(var_name, val)
    if not s.strip():
        raise ValidationError(_("{item} cannot be blank.").format(item=var_name))
    return s

def check_string_in(possible_values: Union[Set[str], List[str]]) -> Validator[str]:
    @set_type_structure("str")
    def validator(var_name: str, val: object) -> str:
        s = check_string(var_name, val)
        if s not in possible_values:
            raise ValidationError(_("Invalid {var_name}").format(var_name=var_name))
        return s

    return validator

@set_type_structure("str")
def check_short_string(var_name: str, val: object) -> str:
    return check_capped_string(50)(var_name, val)

def check_capped_string(max_length: int) -> Validator[str]:
    @set_type_structure("str")
    def validator(var_name: str, val: object) -> str:
        s = check_string(var_name, val)
        if len(s) > max_length:
            raise ValidationError(_("{var_name} is too long (limit: {max_length} characters)").format(
                var_name=var_name, max_length=max_length,
            ))
        return s

    return validator

def check_string_fixed_length(length: int) -> Validator[str]:
    @set_type_structure("str")
    def validator(var_name: str, val: object) -> Optional[str]:
        s = check_string(var_name, val)
        if len(s) != length:
            raise ValidationError(_("{var_name} has incorrect length {length}; should be {target_length}").format(
                var_name=var_name, target_length=length, length=len(s),
            ))
        return s

    return validator

@set_type_structure("str")
def check_long_string(var_name: str, val: object) -> str:
    return check_capped_string(500)(var_name, val)

@set_type_structure("date")
def check_date(var_name: str, val: object) -> str:
    if not isinstance(val, str):
        raise ValidationError(_('{var_name} is not a string').format(var_name=var_name))
    try:
        datetime.strptime(val, '%Y-%m-%d')
    except ValueError:
        raise ValidationError(_('{var_name} is not a date').format(var_name=var_name))
    return val

@set_type_structure("int")
def check_int(var_name: str, val: object) -> int:
    if not isinstance(val, int):
        raise ValidationError(_('{var_name} is not an integer').format(var_name=var_name))
    return val

def check_int_in(possible_values: List[int]) -> Validator[int]:
    @set_type_structure("int")
    def validator(var_name: str, val: object) -> int:
        n = check_int(var_name, val)
        if n not in possible_values:
            raise ValidationError(_("Invalid {var_name}").format(var_name=var_name))
        return n

    return validator

@set_type_structure("float")
def check_float(var_name: str, val: object) -> float:
    if not isinstance(val, float):
        raise ValidationError(_('{var_name} is not a float').format(var_name=var_name))
    return val

@set_type_structure("bool")
def check_bool(var_name: str, val: object) -> bool:
    if not isinstance(val, bool):
        raise ValidationError(_('{var_name} is not a boolean').format(var_name=var_name))
    return val

@set_type_structure("str")
def check_color(var_name: str, val: object) -> str:
    s = check_string(var_name, val)
    valid_color_pattern = re.compile(r'^#([a-fA-F0-9]{3,6})$')
    matched_results = valid_color_pattern.match(s)
    if not matched_results:
        raise ValidationError(_('{var_name} is not a valid hex color code').format(var_name=var_name))
    return s

def check_none_or(sub_validator: Validator[ResultT]) -> Validator[ResultT]:
    if USING_TYPE_STRUCTURE:
        type_structure = 'none_or_' + sub_validator.type_structure  # type: ignore[attr-defined] # monkey-patching
    else:
        type_structure = None

    @set_type_structure(type_structure)
    def f(var_name: str, val: object) -> Optional[ResultT]:
        if val is None:
            return val
        else:
            return sub_validator(var_name, val)
    return f

# https://zulip.readthedocs.io/en/latest/testing/mypy.html#using-overload-to-accurately-describe-variations
@overload
def check_list(sub_validator: None, length: Optional[int]=None) -> Validator[List[object]]:
    ...
@overload
def check_list(sub_validator: Validator[ResultT], length: Optional[int]=None) -> Validator[List[ResultT]]:
    ...
def check_list(sub_validator: Optional[Validator[ResultT]]=None, length: Optional[int]=None) -> Validator[List[ResultT]]:
    if USING_TYPE_STRUCTURE:
        if sub_validator:
            type_structure = [sub_validator.type_structure]  # type: ignore[attr-defined] # monkey-patching
        else:
            type_structure = 'list'  # type: ignore[assignment] # monkey-patching
    else:
        type_structure = None  # type: ignore[assignment] # monkey-patching

    @set_type_structure(type_structure)
    def f(var_name: str, val: object) -> List[ResultT]:
        if not isinstance(val, list):
            raise ValidationError(_('{var_name} is not a list').format(var_name=var_name))

        if length is not None and length != len(val):
            raise ValidationError(_('{container} should have exactly {length} items').format(
                container=var_name, length=length,
            ))

        if sub_validator:
            for i, item in enumerate(val):
                vname = f'{var_name}[{i}]'
                valid_item = sub_validator(vname, item)
                assert item is valid_item  # To justify the unchecked cast below

        return cast(List[ResultT], val)
    return f

# https://zulip.readthedocs.io/en/latest/testing/mypy.html#using-overload-to-accurately-describe-variations
@overload
def check_dict(required_keys: Iterable[Tuple[str, Validator[object]]]=[],
               optional_keys: Iterable[Tuple[str, Validator[object]]]=[],
               *,
               _allow_only_listed_keys: bool=False) -> Validator[Dict[str, object]]:
    ...
@overload
def check_dict(required_keys: Iterable[Tuple[str, Validator[ResultT]]]=[],
               optional_keys: Iterable[Tuple[str, Validator[ResultT]]]=[],
               *,
               value_validator: Validator[ResultT],
               _allow_only_listed_keys: bool=False) -> Validator[Dict[str, ResultT]]:
    ...
def check_dict(required_keys: Iterable[Tuple[str, Validator[ResultT]]]=[],
               optional_keys: Iterable[Tuple[str, Validator[ResultT]]]=[],
               *,
               value_validator: Optional[Validator[ResultT]]=None,
               _allow_only_listed_keys: bool=False) -> Validator[Dict[str, ResultT]]:
    type_structure: Dict[str, Any] = {}

    @set_type_structure(type_structure)
    def f(var_name: str, val: object) -> Dict[str, ResultT]:
        if not isinstance(val, dict):
            raise ValidationError(_('{var_name} is not a dict').format(var_name=var_name))

        for k in val:
            check_string(f'{var_name} key', k)

        for k, sub_validator in required_keys:
            if k not in val:
                raise ValidationError(_('{key_name} key is missing from {var_name}').format(
                    key_name=k, var_name=var_name,
                ))
            vname = f'{var_name}["{k}"]'
            sub_validator(vname, val[k])
            if USING_TYPE_STRUCTURE:
                type_structure[k] = sub_validator.type_structure  # type: ignore[attr-defined] # monkey-patching

        for k, sub_validator in optional_keys:
            if k in val:
                vname = f'{var_name}["{k}"]'
                sub_validator(vname, val[k])
            if USING_TYPE_STRUCTURE:
                type_structure[k] = sub_validator.type_structure  # type: ignore[attr-defined] # monkey-patching

        if value_validator:
            for key in val:
                vname = f'{var_name} contains a value that'
                valid_value = value_validator(vname, val[key])
                assert val[key] is valid_value  # To justify the unchecked cast below
            if USING_TYPE_STRUCTURE:
                type_structure['any'] = value_validator.type_structure  # type: ignore[attr-defined] # monkey-patching

        if _allow_only_listed_keys:
            required_keys_set = {x[0] for x in required_keys}
            optional_keys_set = {x[0] for x in optional_keys}
            delta_keys = set(val.keys()) - required_keys_set - optional_keys_set
            if len(delta_keys) != 0:
                raise ValidationError(_("Unexpected arguments: {}").format(", ".join(list(delta_keys))))

        return cast(Dict[str, ResultT], val)

    return f

def check_dict_only(required_keys: Iterable[Tuple[str, Validator[ResultT]]],
                    optional_keys: Iterable[Tuple[str, Validator[ResultT]]]=[]) -> Validator[Dict[str, ResultT]]:
    return cast(
        Validator[Dict[str, ResultT]],
        check_dict(required_keys, optional_keys, _allow_only_listed_keys=True),
    )

def check_union(allowed_type_funcs: Iterable[Validator[ResultT]]) -> Validator[ResultT]:
    """
    Use this validator if an argument is of a variable type (e.g. processing
    properties that might be strings or booleans).

    `allowed_type_funcs`: the check_* validator functions for the possible data
    types for this variable.
    """

    if USING_TYPE_STRUCTURE:
        type_structure = f'any("{[x.type_structure for x in allowed_type_funcs]}")'  # type: ignore[attr-defined] # monkey-patching
    else:
        type_structure = None  # type: ignore[assignment] # monkey-patching

    @set_type_structure(type_structure)
    def enumerated_type_check(var_name: str, val: object) -> ResultT:
        for func in allowed_type_funcs:
            try:
                return func(var_name, val)
            except ValidationError:
                pass
        raise ValidationError(_('{var_name} is not an allowed_type').format(var_name=var_name))
    return enumerated_type_check

def equals(expected_val: ResultT) -> Validator[ResultT]:
    @set_type_structure(f'equals("{str(expected_val)}")')
    def f(var_name: str, val: object) -> ResultT:
        if val != expected_val:
            raise ValidationError(_('{variable} != {expected_value} ({value} is wrong)').format(
                variable=var_name, expected_value=expected_val, value=val,
            ))
        return cast(ResultT, val)
    return f

@set_type_structure('str')
def validate_login_email(email: str) -> None:
    try:
        validate_email(email)
    except ValidationError as err:
        raise JsonableError(str(err.message))

@set_type_structure('str')
def check_url(var_name: str, val: object) -> str:
    # First, ensure val is a string
    s = check_string(var_name, val)
    # Now, validate as URL
    validate = URLValidator()
    try:
        validate(s)
        return s
    except ValidationError:
        raise ValidationError(_('{var_name} is not a URL').format(var_name=var_name))

@set_type_structure('str')
def check_external_account_url_pattern(var_name: str, val: object) -> str:
    s = check_string(var_name, val)

    if s.count('%(username)s') != 1:
        raise ValidationError(_('Malformed URL pattern.'))
    url_val = s.replace('%(username)s', 'username')

    check_url(var_name, url_val)
    return s

def validate_choice_field_data(field_data: ProfileFieldData) -> Dict[str, Dict[str, str]]:
    """
    This function is used to validate the data sent to the server while
    creating/editing choices of the choice field in Organization settings.
    """
    validator = check_dict_only([
        ('text', check_required_string),
        ('order', check_required_string),
    ])

    for key, value in field_data.items():
        if not key.strip():
            raise ValidationError(_("'{item}' cannot be blank.").format(item='value'))

        valid_value = validator('field_data', value)
        assert value is valid_value  # To justify the unchecked cast below

    return cast(Dict[str, Dict[str, str]], field_data)

def validate_choice_field(var_name: str, field_data: str, value: object) -> str:
    """
    This function is used to validate the value selected by the user against a
    choice field. This is not used to validate admin data.
    """
    s = check_string(var_name, value)
    field_data_dict = ujson.loads(field_data)
    if s not in field_data_dict:
        msg = _("'{value}' is not a valid choice for '{field_name}'.")
        raise ValidationError(msg.format(value=value, field_name=var_name))
    return s

def check_widget_content(widget_content: object) -> Dict[str, Any]:
    if not isinstance(widget_content, dict):
        raise ValidationError('widget_content is not a dict')

    if 'widget_type' not in widget_content:
        raise ValidationError('widget_type is not in widget_content')

    if 'extra_data' not in widget_content:
        raise ValidationError('extra_data is not in widget_content')

    widget_type = widget_content['widget_type']
    extra_data = widget_content['extra_data']

    if not isinstance(extra_data, dict):
        raise ValidationError('extra_data is not a dict')

    if widget_type == 'zform':

        if 'type' not in extra_data:
            raise ValidationError('zform is missing type field')

        if extra_data['type'] == 'choices':
            check_choices = check_list(
                check_dict([
                    ('short_name', check_string),
                    ('long_name', check_string),
                    ('reply', check_string),
                ]),
            )

            checker = check_dict([
                ('heading', check_string),
                ('choices', check_choices),
            ])

            checker('extra_data', extra_data)

            return widget_content

        raise ValidationError('unknown zform type: ' + extra_data['type'])

    raise ValidationError('unknown widget type: ' + widget_type)


# Converter functions for use with has_request_variables
@set_type_structure('int')
def to_non_negative_int(s: str, max_int_size: int=2**32-1) -> int:
    x = int(s)
    if x < 0:
        raise ValueError("argument is negative")
    if x > max_int_size:
        raise ValueError(f'{x} is too large (max {max_int_size})')
    return x

def to_positive_or_allowed_int(allowed_integer: int) -> Callable[[str], int]:
    @set_type_structure('int')
    def convertor(s: str) -> int:
        x = int(s)
        if x == allowed_integer:
            return x
        if x == 0:
            raise ValueError("argument is 0")
        return to_non_negative_int(s)
    return convertor

@set_type_structure('any(List[int], str)]')
def check_string_or_int_list(var_name: str, val: object) -> Union[str, List[int]]:
    if isinstance(val, str):
        return val

    if not isinstance(val, list):
        raise ValidationError(_('{var_name} is not a string or an integer list').format(var_name=var_name))

    return check_list(check_int)(var_name, val)

@set_type_structure('any(int, str)')
def check_string_or_int(var_name: str, val: object) -> Union[str, int]:
    if isinstance(val, str) or isinstance(val, int):
        return val

    raise ValidationError(_('{var_name} is not a string or integer').format(var_name=var_name))