from ssz_test_case import invalid_test_case, valid_test_case
from eth2spec.utils.ssz.ssz_typing import View, Container, byte, uint8, uint16, \
    uint32, uint64, List, ByteList, Vector, Bitvector, Bitlist
from eth2spec.utils.ssz.ssz_impl import serialize
from random import Random
from typing import Dict, Tuple, Sequence, Callable, Type
from eth2spec.debug.random_value import RandomizationMode, get_random_ssz_object


class SingleFieldTestStruct(Container):
    A: byte


class SmallTestStruct(Container):
    A: uint16
    B: uint16


class FixedTestStruct(Container):
    A: uint8
    B: uint64
    C: uint32


class VarTestStruct(Container):
    A: uint16
    B: List[uint16, 1024]
    C: uint8


class ComplexTestStruct(Container):
    A: uint16
    B: List[uint16, 128]
    C: uint8
    D: ByteList[256]
    E: VarTestStruct
    F: Vector[FixedTestStruct, 4]
    G: Vector[VarTestStruct, 2]


class BitsStruct(Container):
    A: Bitlist[5]
    B: Bitvector[2]
    C: Bitvector[1]
    D: Bitlist[6]
    E: Bitvector[8]


def container_case_fn(rng: Random, mode: RandomizationMode, typ: Type[View], chaos: bool=False):
    return get_random_ssz_object(rng, typ,
                                 max_bytes_length=2000,
                                 max_list_length=2000,
                                 mode=mode, chaos=chaos)


PRESET_CONTAINERS: Dict[str, Tuple[Type[View], Sequence[int]]] = {
    'SingleFieldTestStruct': (SingleFieldTestStruct, []),
    'SmallTestStruct': (SmallTestStruct, []),
    'FixedTestStruct': (FixedTestStruct, []),
    'VarTestStruct': (VarTestStruct, [2]),
    'ComplexTestStruct': (ComplexTestStruct, [2, 2 + 4 + 1, 2 + 4 + 1 + 4]),
    'BitsStruct': (BitsStruct, [0, 4 + 1 + 1, 4 + 1 + 1 + 4]),
}


def valid_cases():
    rng = Random(1234)
    for (name, (typ, offsets)) in PRESET_CONTAINERS.items():
        for mode in [RandomizationMode.mode_zero, RandomizationMode.mode_max]:
            yield f'{name}_{mode.to_name()}', valid_test_case(lambda: container_case_fn(rng, mode, typ))

        if len(offsets) == 0:
            modes = [RandomizationMode.mode_random, RandomizationMode.mode_zero, RandomizationMode.mode_max]
        else:
            modes = list(RandomizationMode)

        for mode in modes:
            for variation in range(3):
                yield f'{name}_{mode.to_name()}_chaos_{variation}', \
                      valid_test_case(lambda: container_case_fn(rng, mode, typ, chaos=True))
        # Notes: Below is the second wave of iteration, and only the random mode is selected
        # for container without offset since ``RandomizationMode.mode_zero`` and ``RandomizationMode.mode_max``
        # are deterministic.
        modes = [RandomizationMode.mode_random] if len(offsets) == 0 else list(RandomizationMode)
        for mode in modes:
            for variation in range(10):
                yield f'{name}_{mode.to_name()}_{variation}', \
                      valid_test_case(lambda: container_case_fn(rng, mode, typ))


def mod_offset(b: bytes, offset_index: int, change: Callable[[int], int]):
    return b[:offset_index] + \
           (change(int.from_bytes(b[offset_index:offset_index + 4], byteorder='little')) & 0xffffffff) \
           .to_bytes(length=4, byteorder='little') + \
           b[offset_index + 4:]


def invalid_cases():
    rng = Random(1234)
    for (name, (typ, offsets)) in PRESET_CONTAINERS.items():
        # using mode_max_count, so that the extra byte cannot be picked up as normal list content
        yield f'{name}_extra_byte', \
              invalid_test_case(lambda: serialize(
                  container_case_fn(rng, RandomizationMode.mode_max_count, typ)) + b'\xff')

        if len(offsets) != 0:
            # Note: there are many more ways to have invalid offsets,
            # these are just example to get clients started looking into hardening ssz.
            for mode in [RandomizationMode.mode_random,
                         RandomizationMode.mode_nil_count,
                         RandomizationMode.mode_one_count,
                         RandomizationMode.mode_max_count]:
                for index, offset_index in enumerate(offsets):
                    yield f'{name}_{mode.to_name()}_offset_{offset_index}_plus_one', \
                          invalid_test_case(lambda: mod_offset(
                              b=serialize(container_case_fn(rng, mode, typ)),
                              offset_index=offset_index,
                              change=lambda x: x + 1
                          ))
                    yield f'{name}_{mode.to_name()}_offset_{offset_index}_zeroed', \
                          invalid_test_case(lambda: mod_offset(
                              b=serialize(container_case_fn(rng, mode, typ)),
                              offset_index=offset_index,
                              change=lambda x: 0
                          ))
                    if index == 0:
                        yield f'{name}_{mode.to_name()}_offset_{offset_index}_minus_one', \
                            invalid_test_case(lambda: mod_offset(
                              b=serialize(container_case_fn(rng, mode, typ)),
                              offset_index=offset_index,
                              change=lambda x: x - 1
                            ))
                    if mode == RandomizationMode.mode_max_count:
                        serialized = serialize(container_case_fn(rng, mode, typ))
                        serialized = serialized + serialized[:2]
                        yield f'{name}_{mode.to_name()}_last_offset_{offset_index}_overflow', \
                            invalid_test_case(lambda: serialized)
                    if mode == RandomizationMode.mode_one_count:
                        serialized = serialize(container_case_fn(rng, mode, typ))
                        serialized = serialized + serialized[:1]
                        yield f'{name}_{mode.to_name()}_last_offset_{offset_index}_wrong_byte_length', \
                            invalid_test_case(lambda: serialized)