import pytest
from copy import deepcopy
from eth2spec.phase0 import mainnet as spec_phase0_mainnet, minimal as spec_phase0_minimal
from eth2spec.altair import mainnet as spec_altair_mainnet, minimal as spec_altair_minimal
from eth2spec.merge import mainnet as spec_merge_mainnet, minimal as spec_merge_minimal
from eth2spec.utils import bls

from .exceptions import SkippedTest
from .helpers.constants import (
    SpecForkName, PresetBaseName,
    PHASE0, ALTAIR, MERGE, MINIMAL, MAINNET,
    ALL_PHASES, FORKS_BEFORE_ALTAIR, FORKS_BEFORE_MERGE,
)
from .helpers.genesis import create_genesis_state
from .utils import vector_test, with_meta_tags, build_transition_test

from random import Random
from typing import Any, Callable, Sequence, TypedDict, Protocol, Dict

from lru import LRU

# Without pytest CLI arg or pyspec-test-generator 'preset' argument, this will be the config to apply.
DEFAULT_TEST_PRESET = MINIMAL


# TODO: currently phases are defined as python modules.
# It would be better if they would be more well-defined interfaces for stronger typing.

class Configuration(Protocol):
    PRESET_BASE: str


class Spec(Protocol):
    fork: str
    config: Configuration


class SpecPhase0(Spec):
    ...


class SpecAltair(Spec):
    ...


class SpecMerge(Spec):
    ...


spec_targets: Dict[PresetBaseName, Dict[SpecForkName, Spec]] = {
    MINIMAL: {
        PHASE0: spec_phase0_minimal,
        ALTAIR: spec_altair_minimal,
        MERGE: spec_merge_minimal,
    },
    MAINNET: {
        PHASE0: spec_phase0_mainnet,
        ALTAIR: spec_altair_mainnet,
        MERGE: spec_merge_mainnet,
    },
}


class SpecForks(TypedDict, total=False):
    PHASE0: SpecPhase0
    ALTAIR: SpecAltair
    MERGE: SpecMerge


def _prepare_state(balances_fn: Callable[[Any], Sequence[int]], threshold_fn: Callable[[Any], int],
                   spec: Spec, phases: SpecForks):
    phase = phases[spec.fork]
    balances = balances_fn(phase)
    activation_threshold = threshold_fn(phase)
    state = create_genesis_state(spec=phase, validator_balances=balances,
                                 activation_threshold=activation_threshold)
    return state


_custom_state_cache_dict = LRU(size=10)


def with_custom_state(balances_fn: Callable[[Any], Sequence[int]],
                      threshold_fn: Callable[[Any], int]):
    def deco(fn):

        def entry(*args, spec: Spec, phases: SpecForks, **kw):
            # make a key for the state, unique to the fork + config (incl preset choice) and balances/activations
            key = (spec.fork, spec.config.__hash__(), spec.__file__, balances_fn, threshold_fn)
            global _custom_state_cache_dict
            if key not in _custom_state_cache_dict:
                state = _prepare_state(balances_fn, threshold_fn, spec, phases)
                _custom_state_cache_dict[key] = state.get_backing()

            # Take an entry out of the LRU.
            # No copy is necessary, as we wrap the immutable backing with a new view.
            state = spec.BeaconState(backing=_custom_state_cache_dict[key])
            kw['state'] = state
            return fn(*args, spec=spec, phases=phases, **kw)
        return entry
    return deco


def default_activation_threshold(spec):
    """
    Helper method to use the default balance activation threshold for state creation for tests.
    Usage: `@with_custom_state(threshold_fn=default_activation_threshold, ...)`
    """
    return spec.MAX_EFFECTIVE_BALANCE


def zero_activation_threshold(spec):
    """
    Helper method to use 0 gwei as the activation threshold for state creation for tests.
    Usage: `@with_custom_state(threshold_fn=zero_activation_threshold, ...)`
    """
    return 0


def default_balances(spec):
    """
    Helper method to create a series of default balances.
    Usage: `@with_custom_state(balances_fn=default_balances, ...)`
    """
    num_validators = spec.SLOTS_PER_EPOCH * 8
    return [spec.MAX_EFFECTIVE_BALANCE] * num_validators


with_state = with_custom_state(default_balances, default_activation_threshold)


def low_balances(spec):
    """
    Helper method to create a series of low balances.
    Usage: `@with_custom_state(balances_fn=low_balances, ...)`
    """
    num_validators = spec.SLOTS_PER_EPOCH * 8
    # Technically the balances cannot be this low starting from genesis, but it is useful for testing
    low_balance = 18 * 10 ** 9
    return [low_balance] * num_validators


def misc_balances(spec):
    """
    Helper method to create a series of balances that includes some misc. balances.
    Usage: `@with_custom_state(balances_fn=misc_balances, ...)`
    """
    num_validators = spec.SLOTS_PER_EPOCH * 8
    balances = [spec.MAX_EFFECTIVE_BALANCE * 2 * i // num_validators for i in range(num_validators)]
    rng = Random(1234)
    rng.shuffle(balances)
    return balances


def low_single_balance(spec):
    """
    Helper method to create a single of balance of 1 Gwei.
    Usage: `@with_custom_state(balances_fn=low_single_balance, ...)`
    """
    return [1]


def large_validator_set(spec):
    """
    Helper method to create a large series of default balances.
    Usage: `@with_custom_state(balances_fn=default_balances, ...)`
    """
    num_validators = 2 * spec.SLOTS_PER_EPOCH * spec.MAX_COMMITTEES_PER_SLOT * spec.TARGET_COMMITTEE_SIZE
    return [spec.MAX_EFFECTIVE_BALANCE] * num_validators


def single_phase(fn):
    """
    Decorator that filters out the phases data.
    most state tests only focus on behavior of a single phase (the "spec").
    This decorator is applied as part of spec_state_test(fn).
    """
    def entry(*args, **kw):
        if 'phases' in kw:
            kw.pop('phases')
        return fn(*args, **kw)
    return entry


# BLS is turned on by default, it can be disabled in tests by overriding this, or using `--disable-bls`.
# *This is for performance purposes during TESTING, DO NOT DISABLE IN PRODUCTION*.
# The runner of the test can indicate the preferred setting (test generators prefer BLS to be ON).
# - Some tests are marked as BLS-requiring, and ignore this setting.
#    (tests that express differences caused by BLS, e.g. invalid signatures being rejected)
# - Some other tests are marked as BLS-ignoring, and ignore this setting.
#    (tests that are heavily performance impacted / require unsigned state transitions)
# - Most tests respect the BLS setting.
DEFAULT_BLS_ACTIVE = True


is_pytest = True


def dump_skipping_message(reason: str) -> None:
    message = f"[Skipped test] {reason}"
    if is_pytest:
        pytest.skip(message)
    else:
        raise SkippedTest(message)


def spec_test(fn):
    # Bls switch must be wrapped by vector_test,
    # to fully go through the yielded bls switch data, before setting back the BLS setting.
    # A test may apply BLS overrides such as @always_bls,
    #  but if it yields data (n.b. @always_bls yields the bls setting), it should be wrapped by this decorator.
    #  This is why @alway_bls has its own bls switch, since the override is beyond the reach of the outer switch.
    return vector_test()(bls_switch(fn))


# shorthand for decorating @spectest() @with_state @single_phase
def spec_state_test(fn):
    return spec_test(with_state(single_phase(fn)))


def spec_configured_state_test(conf):
    overrides = with_config_overrides(conf)

    def decorator(fn):
        return spec_test(overrides(with_state(single_phase(fn))))
    return decorator


def expect_assertion_error(fn):
    bad = False
    try:
        fn()
        bad = True
    except AssertionError:
        pass
    except IndexError:
        # Index errors are special; the spec is not explicit on bound checking, an IndexError is like a failed assert.
        pass
    if bad:
        raise AssertionError('expected an assertion error, but got none.')


def never_bls(fn):
    """
    Decorator to apply on ``bls_switch`` decorator to force BLS de-activation. Useful to mark tests as BLS-ignorant.
    This decorator may only be applied to yielding spec test functions, and should be wrapped by vector_test,
     as the yielding needs to complete before setting back the BLS setting.
    """
    def entry(*args, **kw):
        # override bls setting
        kw['bls_active'] = False
        return bls_switch(fn)(*args, **kw)
    return with_meta_tags({'bls_setting': 2})(entry)


def always_bls(fn):
    """
    Decorator to apply on ``bls_switch`` decorator to force BLS activation. Useful to mark tests as BLS-dependent.
    This decorator may only be applied to yielding spec test functions, and should be wrapped by vector_test,
     as the yielding needs to complete before setting back the BLS setting.
    """
    def entry(*args, **kw):
        # override bls setting
        kw['bls_active'] = True
        return bls_switch(fn)(*args, **kw)
    return with_meta_tags({'bls_setting': 1})(entry)


def bls_switch(fn):
    """
    Decorator to make a function execute with BLS ON, or BLS off.
    Based on an optional bool argument ``bls_active``, passed to the function at runtime.
    This decorator may only be applied to yielding spec test functions, and should be wrapped by vector_test,
     as the yielding needs to complete before setting back the BLS setting.
    """
    def entry(*args, **kw):
        old_state = bls.bls_active
        bls.bls_active = kw.pop('bls_active', DEFAULT_BLS_ACTIVE)
        res = fn(*args, **kw)
        if res is not None:
            yield from res
        bls.bls_active = old_state
    return entry


def disable_process_reveal_deadlines(fn):
    """
    Decorator to make a function execute with `process_reveal_deadlines` OFF.
    This is for testing long-range epochs transition without considering the reveal-deadline slashing effect.
    """
    def entry(*args, spec: Spec, **kw):
        if hasattr(spec, 'process_reveal_deadlines'):
            old_state = spec.process_reveal_deadlines
            spec.process_reveal_deadlines = lambda state: None

        yield from fn(*args, spec=spec, **kw)

        if hasattr(spec, 'process_reveal_deadlines'):
            spec.process_reveal_deadlines = old_state

    return with_meta_tags({'reveal_deadlines_setting': 1})(entry)


def with_all_phases(fn):
    """
    A decorator for running a test with every phase
    """
    return with_phases(ALL_PHASES)(fn)


def with_all_phases_except(exclusion_phases):
    """
    A decorator factory for running a tests with every phase except the ones listed
    """
    def decorator(fn):
        return with_phases([phase for phase in ALL_PHASES if phase not in exclusion_phases])(fn)
    return decorator


def with_phases(phases, other_phases=None):
    """
    Decorator factory that returns a decorator that runs a test for the appropriate phases.
    Additional phases that do not initially run, but are made available through the test, are optional.
    """
    def decorator(fn):
        def wrapper(*args, **kw):
            run_phases = phases

            # limit phases if one explicitly specified
            if 'phase' in kw:
                phase = kw.pop('phase')
                if phase not in phases:
                    dump_skipping_message(f"doesn't support this fork: {phase}")
                    return None
                run_phases = [phase]

            if PHASE0 not in run_phases and ALTAIR not in run_phases and MERGE not in run_phases:
                dump_skipping_message("none of the recognized phases are executable, skipping test.")
                return None

            available_phases = set(run_phases)
            if other_phases is not None:
                available_phases |= set(other_phases)

            preset_name = DEFAULT_TEST_PRESET
            if 'preset' in kw:
                preset_name = kw.pop('preset')
            targets = spec_targets[preset_name]

            # TODO: test state is dependent on phase0 but is immediately transitioned to later phases.
            #  A new state-creation helper for later phases may be in place, and then tests can run without phase0
            available_phases.add(PHASE0)

            # Populate all phases for multi-phase tests
            phase_dir = {}
            if PHASE0 in available_phases:
                phase_dir[PHASE0] = targets[PHASE0]
            if ALTAIR in available_phases:
                phase_dir[ALTAIR] = targets[ALTAIR]
            if MERGE in available_phases:
                phase_dir[MERGE] = targets[MERGE]

            # return is ignored whenever multiple phases are ran.
            # This return is for test generators to emit python generators (yielding test vector outputs)
            if PHASE0 in run_phases:
                ret = fn(spec=targets[PHASE0], phases=phase_dir, *args, **kw)
            if ALTAIR in run_phases:
                ret = fn(spec=targets[ALTAIR], phases=phase_dir, *args, **kw)
            if MERGE in run_phases:
                ret = fn(spec=targets[MERGE], phases=phase_dir, *args, **kw)

            # TODO: merge, sharding, custody_game and das are not executable yet.
            #  Tests that specify these features will not run, and get ignored for these specific phases.
            return ret
        return wrapper
    return decorator


def with_presets(preset_bases, reason=None):
    available_presets = set(preset_bases)

    def decorator(fn):
        def wrapper(*args, spec: Spec, **kw):
            if spec.config.PRESET_BASE not in available_presets:
                message = f"doesn't support this preset base: {spec.config.PRESET_BASE}."
                if reason is not None:
                    message = f"{message} Reason: {reason}"
                dump_skipping_message(message)
                return None

            return fn(*args, spec=spec, **kw)
        return wrapper
    return decorator


def with_config_overrides(config_overrides):
    """
    WARNING: the spec_test decorator must wrap this, to ensure the decorated test actually runs.
    This decorator forces the test to yield, and pytest doesn't run generator tests, and instead silently passes it.
    Use 'spec_configured_state_test' instead of 'spec_state_test' if you are unsure.

    This is a decorator that applies a dict of config value overrides to the spec during execution.
    """
    def decorator(fn):
        def wrapper(*args, spec: Spec, **kw):
            # remember the old config
            old_config = spec.config

            # apply our overrides to a copy of it, and apply it to the spec
            tmp_config = deepcopy(old_config._asdict())  # not a private method, there are multiple
            tmp_config.update(config_overrides)
            config_types = spec.Configuration.__annotations__
            # Retain types of all config values
            test_config = {k: config_types[k](v) for k, v in tmp_config.items()}

            # Output the config for test vectors  (TODO: check config YAML encoding)
            yield 'config', 'data', test_config

            spec.config = spec.Configuration(**test_config)

            # Run the function
            out = fn(*args, spec=spec, **kw)
            # If it's not returning None like a normal test function,
            # it's generating things, and we need to complete it before setting back the config.
            if out is not None:
                yield from out

            # Restore the old config and apply it
            spec.config = old_config

        return wrapper
    return decorator


def is_post_altair(spec):
    if spec.fork == MERGE:  # TODO: remove parallel Altair-Merge condition after rebase.
        return False
    if spec.fork in FORKS_BEFORE_ALTAIR:
        return False
    return True


def is_post_merge(spec):
    if spec.fork == ALTAIR:  # TODO: remove parallel Altair-Merge condition after rebase.
        return False
    if spec.fork in FORKS_BEFORE_MERGE:
        return False
    return True


with_altair_and_later = with_phases([ALTAIR])  # TODO: include Merge, but not until Merge work is rebased.
with_merge_and_later = with_phases([MERGE])


def fork_transition_test(pre_fork_name, post_fork_name, fork_epoch=None):
    """
    A decorator to construct a "transition" test from one fork of the eth2 spec
    to another.

    Decorator assumes a transition from the `pre_fork_name` fork to the
    `post_fork_name` fork. The user can supply a `fork_epoch` at which the
    fork occurs or they must compute one (yielding to the generator) during the test
    if more custom behavior is desired.

    A test using this decorator should expect to receive as parameters:
    `state`: the default state constructed for the `pre_fork_name` fork
        according to the `with_state` decorator.
    `fork_epoch`: the `fork_epoch` provided to this decorator, if given.
    `spec`: the version of the eth2 spec corresponding to `pre_fork_name`.
    `post_spec`: the version of the eth2 spec corresponding to `post_fork_name`.
    `pre_tag`: a function to tag data as belonging to `pre_fork_name` fork.
        Used to discriminate data during consumption of the generated spec tests.
    `post_tag`: a function to tag data as belonging to `post_fork_name` fork.
        Used to discriminate data during consumption of the generated spec tests.
    """
    def _wrapper(fn):
        @with_phases([pre_fork_name], other_phases=[post_fork_name])
        @spec_test
        @with_state
        def _adapter(*args, **kwargs):
            wrapped = build_transition_test(fn,
                                            pre_fork_name,
                                            post_fork_name,
                                            fork_epoch=fork_epoch)
            return wrapped(*args, **kwargs)
        return _adapter
    return _wrapper