"""Validation of dependencies of packages
"""
from __future__ import annotations

import logging
from typing import Callable
from typing import Dict
from typing import List
from typing import NamedTuple
from typing import Optional
from typing import Set
from typing import Tuple

from pip._internal.distributions import make_distribution_for_install_requirement
from pip._internal.metadata import get_default_environment
from pip._internal.metadata.base import DistributionVersion
from pip._internal.req.req_install import InstallRequirement
from pip._vendor.packaging.requirements import Requirement
from pip._vendor.packaging.utils import canonicalize_name
from pip._vendor.packaging.utils import NormalizedName

logger = logging.getLogger(__name__)


class PackageDetails(NamedTuple):
    version: DistributionVersion
    dependencies: list[Requirement]


# Shorthands
PackageSet = Dict[NormalizedName, PackageDetails]
Missing = Tuple[NormalizedName, Requirement]
Conflicting = Tuple[NormalizedName, DistributionVersion, Requirement]

MissingDict = Dict[NormalizedName, List[Missing]]
ConflictingDict = Dict[NormalizedName, List[Conflicting]]
CheckResult = Tuple[MissingDict, ConflictingDict]
ConflictDetails = Tuple[PackageSet, CheckResult]


def create_package_set_from_installed() -> tuple[PackageSet, bool]:
    """Converts a list of distributions into a PackageSet."""
    package_set = {}
    problems = False
    env = get_default_environment()
    for dist in env.iter_installed_distributions(local_only=False, skip=()):
        name = dist.canonical_name
        try:
            dependencies = list(dist.iter_dependencies())
            package_set[name] = PackageDetails(dist.version, dependencies)
        except (OSError, ValueError) as e:
            # Don't crash on unreadable or broken metadata.
            logger.warning('Error parsing requirements for %s: %s', name, e)
            problems = True
    return package_set, problems


def check_package_set(
    package_set: PackageSet, should_ignore: Callable[[str], bool] | None = None,
) -> CheckResult:
    """Check if a package set is consistent

    If should_ignore is passed, it should be a callable that takes a
    package name and returns a boolean.
    """

    missing = {}
    conflicting = {}

    for package_name, package_detail in package_set.items():
        # Info about dependencies of package_name
        missing_deps: set[Missing] = set()
        conflicting_deps: set[Conflicting] = set()

        if should_ignore and should_ignore(package_name):
            continue

        for req in package_detail.dependencies:
            name = canonicalize_name(req.name)

            # Check if it's missing
            if name not in package_set:
                missed = True
                if req.marker is not None:
                    missed = req.marker.evaluate()
                if missed:
                    missing_deps.add((name, req))
                continue

            # Check if there's a conflict
            version = package_set[name].version
            if not req.specifier.contains(version, prereleases=True):
                conflicting_deps.add((name, version, req))

        if missing_deps:
            missing[package_name] = sorted(missing_deps, key=str)
        if conflicting_deps:
            conflicting[package_name] = sorted(conflicting_deps, key=str)

    return missing, conflicting


def check_install_conflicts(to_install: list[InstallRequirement]) -> ConflictDetails:
    """For checking if the dependency graph would be consistent after \
    installing given requirements
    """
    # Start from the current state
    package_set, _ = create_package_set_from_installed()
    # Install packages
    would_be_installed = _simulate_installation_of(to_install, package_set)

    # Only warn about directly-dependent packages; create a whitelist of them
    whitelist = _create_whitelist(would_be_installed, package_set)

    return (
        package_set,
        check_package_set(
            package_set, should_ignore=lambda name: name not in whitelist,
        ),
    )


def _simulate_installation_of(
    to_install: list[InstallRequirement], package_set: PackageSet,
) -> set[NormalizedName]:
    """Computes the version of packages after installing to_install."""
    # Keep track of packages that were installed
    installed = set()

    # Modify it as installing requirement_set would (assuming no errors)
    for inst_req in to_install:
        abstract_dist = make_distribution_for_install_requirement(inst_req)
        dist = abstract_dist.get_metadata_distribution()
        name = dist.canonical_name
        package_set[name] = PackageDetails(dist.version, list(dist.iter_dependencies()))

        installed.add(name)

    return installed


def _create_whitelist(
    would_be_installed: set[NormalizedName], package_set: PackageSet,
) -> set[NormalizedName]:
    packages_affected = set(would_be_installed)

    for package_name in package_set:
        if package_name in packages_affected:
            continue

        for req in package_set[package_name].dependencies:
            if canonicalize_name(req.name) in packages_affected:
                packages_affected.add(package_name)
                break

    return packages_affected