# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/pylint-dev/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/pylint/blob/main/CONTRIBUTORS.txt

"""Imports checkers for Python code."""

from __future__ import annotations

import collections
import copy
import os
import sys
from collections import defaultdict
from collections.abc import ItemsView, Sequence
from functools import cached_property
from typing import TYPE_CHECKING, Any

import astroid
import astroid.modutils
import isort
from astroid import nodes
from astroid.nodes._base_nodes import ImportNode

from pylint.checkers import BaseChecker, DeprecatedMixin
from pylint.checkers.utils import (
    get_import_name,
    in_type_checking_block,
    is_from_fallback_block,
    is_module_ignored,
    is_sys_guard,
    node_ignores_exception,
)
from pylint.constants import MAX_NUMBER_OF_IMPORT_SHOWN
from pylint.exceptions import EmptyReportError
from pylint.graph import DotBackend, get_cycles
from pylint.interfaces import HIGH
from pylint.reporters.ureports.nodes import Paragraph, Section, VerbatimText
from pylint.typing import MessageDefinitionTuple
from pylint.utils.linterstats import LinterStats

if TYPE_CHECKING:
    from pylint.lint import PyLinter


# The dictionary with Any should actually be a _ImportTree again
# but mypy doesn't support recursive types yet
_ImportTree = dict[str, list[dict[str, Any]] | list[str]]

DEPRECATED_MODULES = {
    (0, 0, 0): {"tkinter.tix", "fpectl"},
    (3, 3, 0): {"xml.etree.cElementTree"},
    (3, 4, 0): {"imp"},
    (3, 5, 0): {"formatter"},
    (3, 6, 0): {"asynchat", "asyncore", "smtpd"},
    (3, 7, 0): {"macpath"},
    (3, 9, 0): {"lib2to3", "parser", "symbol", "binhex"},
    (3, 10, 0): {"distutils", "typing.io", "typing.re"},
    (3, 11, 0): {
        "aifc",
        "audioop",
        "cgi",
        "cgitb",
        "chunk",
        "crypt",
        "imghdr",
        "msilib",
        "mailcap",
        "nis",
        "nntplib",
        "ossaudiodev",
        "pipes",
        "sndhdr",
        "spwd",
        "sunau",
        "sre_compile",
        "sre_constants",
        "sre_parse",
        "telnetlib",
        "uu",
        "xdrlib",
    },
}


def _get_first_import(
    node: ImportNode,
    context: nodes.LocalsDictNodeNG,
    name: str,
    base: str | None,
    level: int | None,
    alias: str | None,
) -> tuple[nodes.Import | nodes.ImportFrom | None, str | None]:
    """Return the node where [base.]<name> is imported or None if not found."""
    fullname = f"{base}.{name}" if base else name

    first = None
    found = False
    msg = "reimported"

    for first in context.body:
        if first is node:
            continue
        if first.scope() is node.scope() and first.fromlineno > node.fromlineno:
            continue
        if isinstance(first, nodes.Import):
            if any(fullname == iname[0] for iname in first.names):
                found = True
                break
            for imported_name, imported_alias in first.names:
                if not imported_alias and imported_name == alias:
                    found = True
                    msg = "shadowed-import"
                    break
            if found:
                break
        elif isinstance(first, nodes.ImportFrom):
            if level == first.level:
                for imported_name, imported_alias in first.names:
                    if fullname == f"{first.modname}.{imported_name}":
                        found = True
                        break
                    if (
                        name != "*"
                        and name == imported_name
                        and not (alias or imported_alias)
                    ):
                        found = True
                        break
                    if not imported_alias and imported_name == alias:
                        found = True
                        msg = "shadowed-import"
                        break
                if found:
                    break
    if found and not astroid.are_exclusive(first, node):
        return first, msg
    return None, None


def _ignore_import_failure(
    node: ImportNode,
    modname: str,
    ignored_modules: Sequence[str],
) -> bool:
    if is_module_ignored(modname, ignored_modules):
        return True

    # Ignore import failure if part of guarded import block
    # I.e. `sys.version_info` or `typing.TYPE_CHECKING`
    if in_type_checking_block(node):
        return True
    if isinstance(node.parent, nodes.If) and is_sys_guard(node.parent):
        return True

    return node_ignores_exception(node, ImportError)


# utilities to represents import dependencies as tree and dot graph ###########


def _make_tree_defs(mod_files_list: ItemsView[str, set[str]]) -> _ImportTree:
    """Get a list of 2-uple (module, list_of_files_which_import_this_module),
    it will return a dictionary to represent this as a tree.
    """
    tree_defs: _ImportTree = {}
    for mod, files in mod_files_list:
        node: list[_ImportTree | list[str]] = [tree_defs, []]
        for prefix in mod.split("."):
            assert isinstance(node[0], dict)
            node = node[0].setdefault(prefix, ({}, []))  # type: ignore[arg-type,assignment]
        assert isinstance(node[1], list)
        node[1].extend(files)
    return tree_defs


def _repr_tree_defs(data: _ImportTree, indent_str: str | None = None) -> str:
    """Return a string which represents imports as a tree."""
    lines = []
    nodes_items = data.items()
    for i, (mod, (sub, files)) in enumerate(sorted(nodes_items, key=lambda x: x[0])):
        files_list = "" if not files else f"({','.join(sorted(files))})"
        if indent_str is None:
            lines.append(f"{mod} {files_list}")
            sub_indent_str = "  "
        else:
            lines.append(rf"{indent_str}\-{mod} {files_list}")
            if i == len(nodes_items) - 1:
                sub_indent_str = f"{indent_str}  "
            else:
                sub_indent_str = f"{indent_str}| "
        if sub and isinstance(sub, dict):
            lines.append(_repr_tree_defs(sub, sub_indent_str))
    return "\n".join(lines)


def _dependencies_graph(filename: str, dep_info: dict[str, set[str]]) -> str:
    """Write dependencies as a dot (graphviz) file."""
    done = {}
    printer = DotBackend(os.path.splitext(os.path.basename(filename))[0], rankdir="LR")
    printer.emit('URL="." node[shape="box"]')
    for modname, dependencies in sorted(dep_info.items()):
        sorted_dependencies = sorted(dependencies)
        done[modname] = 1
        printer.emit_node(modname)
        for depmodname in sorted_dependencies:
            if depmodname not in done:
                done[depmodname] = 1
                printer.emit_node(depmodname)
    for depmodname, dependencies in sorted(dep_info.items()):
        for modname in sorted(dependencies):
            printer.emit_edge(modname, depmodname)
    return printer.generate(filename)


def _make_graph(
    filename: str, dep_info: dict[str, set[str]], sect: Section, gtype: str
) -> None:
    """Generate a dependencies graph and add some information about it in the
    report's section.
    """
    outputfile = _dependencies_graph(filename, dep_info)
    sect.append(Paragraph((f"{gtype}imports graph has been written to {outputfile}",)))


# the import checker itself ###################################################

MSGS: dict[str, MessageDefinitionTuple] = {
    "E0401": (
        "Unable to import %s",
        "import-error",
        "Used when pylint has been unable to import a module.",
        {"old_names": [("F0401", "old-import-error")]},
    ),
    "E0402": (
        "Attempted relative import beyond top-level package",
        "relative-beyond-top-level",
        "Used when a relative import tries to access too many levels "
        "in the current package.",
    ),
    "R0401": (
        "Cyclic import (%s)",
        "cyclic-import",
        "Used when a cyclic import between two or more modules is detected.",
    ),
    "R0402": (
        "Use 'from %s import %s' instead",
        "consider-using-from-import",
        "Emitted when a submodule of a package is imported and "
        "aliased with the same name, "
        "e.g., instead of ``import concurrent.futures as futures`` use "
        "``from concurrent import futures``.",
    ),
    "W0401": (
        "Wildcard import %s",
        "wildcard-import",
        "Used when `from module import *` is detected.",
    ),
    "W0404": (
        "Reimport %r (imported line %s)",
        "reimported",
        "Used when a module is imported more than once.",
    ),
    "W0406": (
        "Module import itself",
        "import-self",
        "Used when a module is importing itself.",
    ),
    "W0407": (
        "Prefer importing %r instead of %r",
        "preferred-module",
        "Used when a module imported has a preferred replacement module.",
    ),
    "W0410": (
        "__future__ import is not the first non docstring statement",
        "misplaced-future",
        "Python 2.5 and greater require __future__ import to be the "
        "first non docstring statement in the module.",
    ),
    "C0410": (
        "Multiple imports on one line (%s)",
        "multiple-imports",
        "Used when import statement importing multiple modules is detected.",
    ),
    "C0411": (
        "%s should be placed before %s",
        "wrong-import-order",
        "Used when PEP8 import order is not respected (standard imports "
        "first, then third-party libraries, then local imports).",
    ),
    "C0412": (
        "Imports from package %s are not grouped",
        "ungrouped-imports",
        "Used when imports are not grouped by packages.",
    ),
    "C0413": (
        'Import "%s" should be placed at the top of the module',
        "wrong-import-position",
        "Used when code and imports are mixed.",
    ),
    "C0414": (
        "Import alias does not rename original package",
        "useless-import-alias",
        "Used when an import alias is same as original package, "
        "e.g., using import numpy as numpy instead of import numpy as np.",
    ),
    "C0415": (
        "Import outside toplevel (%s)",
        "import-outside-toplevel",
        "Used when an import statement is used anywhere other than the module "
        "toplevel. Move this import to the top of the file.",
    ),
    "W0416": (
        "Shadowed %r (imported line %s)",
        "shadowed-import",
        "Used when a module is aliased with a name that shadows another import.",
    ),
}


DEFAULT_STANDARD_LIBRARY = ()
DEFAULT_KNOWN_THIRD_PARTY = ("enchant",)
DEFAULT_PREFERRED_MODULES = ()


class ImportsChecker(DeprecatedMixin, BaseChecker):
    """BaseChecker for import statements.

    Checks for
    * external modules dependencies
    * relative / wildcard imports
    * cyclic imports
    * uses of deprecated modules
    * uses of modules instead of preferred modules
    """

    name = "imports"
    msgs = {**DeprecatedMixin.DEPRECATED_MODULE_MESSAGE, **MSGS}
    default_deprecated_modules = ()

    options = (
        (
            "deprecated-modules",
            {
                "default": default_deprecated_modules,
                "type": "csv",
                "metavar": "<modules>",
                "help": "Deprecated modules which should not be used,"
                " separated by a comma.",
            },
        ),
        (
            "preferred-modules",
            {
                "default": DEFAULT_PREFERRED_MODULES,
                "type": "csv",
                "metavar": "<module:preferred-module>",
                "help": "Couples of modules and preferred modules,"
                " separated by a comma.",
            },
        ),
        (
            "import-graph",
            {
                "default": "",
                "type": "path",
                "metavar": "<file.gv>",
                "help": "Output a graph (.gv or any supported image format) of"
                " all (i.e. internal and external) dependencies to the given file"
                " (report RP0402 must not be disabled).",
            },
        ),
        (
            "ext-import-graph",
            {
                "default": "",
                "type": "path",
                "metavar": "<file.gv>",
                "help": "Output a graph (.gv or any supported image format)"
                " of external dependencies to the given file"
                " (report RP0402 must not be disabled).",
            },
        ),
        (
            "int-import-graph",
            {
                "default": "",
                "type": "path",
                "metavar": "<file.gv>",
                "help": "Output a graph (.gv or any supported image format)"
                " of internal dependencies to the given file"
                " (report RP0402 must not be disabled).",
            },
        ),
        (
            "known-standard-library",
            {
                "default": DEFAULT_STANDARD_LIBRARY,
                "type": "csv",
                "metavar": "<modules>",
                "help": "Force import order to recognize a module as part of "
                "the standard compatibility libraries.",
            },
        ),
        (
            "known-third-party",
            {
                "default": DEFAULT_KNOWN_THIRD_PARTY,
                "type": "csv",
                "metavar": "<modules>",
                "help": "Force import order to recognize a module as part of "
                "a third party library.",
            },
        ),
        (
            "allow-any-import-level",
            {
                "default": (),
                "type": "csv",
                "metavar": "<modules>",
                "help": (
                    "List of modules that can be imported at any level, not just "
                    "the top level one."
                ),
            },
        ),
        (
            "allow-wildcard-with-all",
            {
                "default": False,
                "type": "yn",
                "metavar": "<y or n>",
                "help": "Allow wildcard imports from modules that define __all__.",
            },
        ),
        (
            "allow-reexport-from-package",
            {
                "default": False,
                "type": "yn",
                "metavar": "<y or n>",
                "help": "Allow explicit reexports by alias from a package __init__.",
            },
        ),
    )

    def __init__(self, linter: PyLinter) -> None:
        BaseChecker.__init__(self, linter)
        self.import_graph: defaultdict[str, set[str]] = defaultdict(set)
        self._imports_stack: list[tuple[ImportNode, str]] = []
        self._first_non_import_node = None
        self._module_pkg: dict[Any, Any] = (
            {}
        )  # mapping of modules to the pkg they belong in
        self._allow_any_import_level: set[Any] = set()
        self.reports = (
            ("RP0401", "External dependencies", self._report_external_dependencies),
            ("RP0402", "Modules dependencies graph", self._report_dependencies_graph),
        )
        self._excluded_edges: defaultdict[str, set[str]] = defaultdict(set)

    def open(self) -> None:
        """Called before visiting project (i.e set of modules)."""
        self.linter.stats.dependencies = {}
        self.linter.stats = self.linter.stats
        self.import_graph = defaultdict(set)
        self._module_pkg = {}  # mapping of modules to the pkg they belong in
        self._current_module_package = False
        self._ignored_modules: Sequence[str] = self.linter.config.ignored_modules
        # Build a mapping {'module': 'preferred-module'}
        self.preferred_modules = dict(
            module.split(":")
            for module in self.linter.config.preferred_modules
            if ":" in module
        )
        self._allow_any_import_level = set(self.linter.config.allow_any_import_level)
        self._allow_reexport_package = self.linter.config.allow_reexport_from_package

    def _import_graph_without_ignored_edges(self) -> defaultdict[str, set[str]]:
        filtered_graph = copy.deepcopy(self.import_graph)
        for node in filtered_graph:
            filtered_graph[node].difference_update(self._excluded_edges[node])
        return filtered_graph

    def close(self) -> None:
        """Called before visiting project (i.e set of modules)."""
        if self.linter.is_message_enabled("cyclic-import"):
            graph = self._import_graph_without_ignored_edges()
            vertices = list(graph)
            for cycle in get_cycles(graph, vertices=vertices):
                self.add_message("cyclic-import", args=" -> ".join(cycle))

    def get_map_data(
        self,
    ) -> tuple[defaultdict[str, set[str]], defaultdict[str, set[str]]]:
        if self.linter.is_message_enabled("cyclic-import"):
            return (self.import_graph, self._excluded_edges)
        return (defaultdict(set), defaultdict(set))

    def reduce_map_data(
        self,
        linter: PyLinter,
        data: list[tuple[defaultdict[str, set[str]], defaultdict[str, set[str]]]],
    ) -> None:
        if self.linter.is_message_enabled("cyclic-import"):
            self.import_graph = defaultdict(set)
            self._excluded_edges = defaultdict(set)
            for to_update in data:
                graph, excluded_edges = to_update
                self.import_graph.update(graph)
                self._excluded_edges.update(excluded_edges)

            self.close()

    def deprecated_modules(self) -> set[str]:
        """Callback returning the deprecated modules."""
        # First get the modules the user indicated
        all_deprecated_modules = set(self.linter.config.deprecated_modules)
        # Now get the hard-coded ones from the stdlib
        for since_vers, mod_set in DEPRECATED_MODULES.items():
            if since_vers <= sys.version_info:
                all_deprecated_modules = all_deprecated_modules.union(mod_set)
        return all_deprecated_modules

    def visit_module(self, node: nodes.Module) -> None:
        """Store if current module is a package, i.e. an __init__ file."""
        self._current_module_package = node.package

    def visit_import(self, node: nodes.Import) -> None:
        """Triggered when an import statement is seen."""
        self._check_reimport(node)
        self._check_import_as_rename(node)
        self._check_toplevel(node)

        names = [name for name, _ in node.names]
        if len(names) >= 2:
            self.add_message("multiple-imports", args=", ".join(names), node=node)

        for name in names:
            self.check_deprecated_module(node, name)
            self._check_preferred_module(node, name)
            imported_module = self._get_imported_module(node, name)
            if isinstance(node.parent, nodes.Module):
                # Allow imports nested
                self._check_position(node)
            if isinstance(node.scope(), nodes.Module):
                self._record_import(node, imported_module)

            if imported_module is None:
                continue

            self._add_imported_module(node, imported_module.name)

    def visit_importfrom(self, node: nodes.ImportFrom) -> None:
        """Triggered when a from statement is seen."""
        basename = node.modname
        imported_module = self._get_imported_module(node, basename)
        absolute_name = get_import_name(node, basename)

        self._check_import_as_rename(node)
        self._check_misplaced_future(node)
        self.check_deprecated_module(node, absolute_name)
        self._check_preferred_module(node, basename)
        self._check_wildcard_imports(node, imported_module)
        self._check_same_line_imports(node)
        self._check_reimport(node, basename=basename, level=node.level)
        self._check_toplevel(node)

        if isinstance(node.parent, nodes.Module):
            # Allow imports nested
            self._check_position(node)
        if isinstance(node.scope(), nodes.Module):
            self._record_import(node, imported_module)
        if imported_module is None:
            return
        for name, _ in node.names:
            if name != "*":
                self._add_imported_module(node, f"{imported_module.name}.{name}")
            else:
                self._add_imported_module(node, imported_module.name)

    def leave_module(self, node: nodes.Module) -> None:
        # Check imports are grouped by category (standard, 3rd party, local)
        std_imports, ext_imports, loc_imports = self._check_imports_order(node)

        # Check that imports are grouped by package within a given category
        met_import: set[str] = set()  # set for 'import x' style
        met_from: set[str] = set()  # set for 'from x import y' style
        current_package = None
        for import_node, import_name in std_imports + ext_imports + loc_imports:
            met = met_from if isinstance(import_node, nodes.ImportFrom) else met_import
            package, _, _ = import_name.partition(".")
            if (
                current_package
                and current_package != package
                and package in met
                and not in_type_checking_block(import_node)
                and not (
                    isinstance(import_node.parent, nodes.If)
                    and is_sys_guard(import_node.parent)
                )
            ):
                self.add_message("ungrouped-imports", node=import_node, args=package)
            current_package = package
            if not self.linter.is_message_enabled(
                "ungrouped-imports", import_node.fromlineno
            ):
                continue
            met.add(package)

        self._imports_stack = []
        self._first_non_import_node = None

    def compute_first_non_import_node(
        self,
        node: (
            nodes.If
            | nodes.Expr
            | nodes.Comprehension
            | nodes.IfExp
            | nodes.Assign
            | nodes.AssignAttr
            | nodes.Try
        ),
    ) -> None:
        # if the node does not contain an import instruction, and if it is the
        # first node of the module, keep a track of it (all the import positions
        # of the module will be compared to the position of this first
        # instruction)
        if self._first_non_import_node:
            return
        if not isinstance(node.parent, nodes.Module):
            return
        if isinstance(node, nodes.Try) and any(
            node.nodes_of_class((nodes.Import, nodes.ImportFrom))
        ):
            return
        if isinstance(node, nodes.Assign):
            # Add compatibility for module level dunder names
            # https://www.python.org/dev/peps/pep-0008/#module-level-dunder-names
            valid_targets = [
                isinstance(target, nodes.AssignName)
                and target.name.startswith("__")
                and target.name.endswith("__")
                for target in node.targets
            ]
            if all(valid_targets):
                return
        self._first_non_import_node = node

    visit_try = visit_assignattr = visit_assign = visit_ifexp = visit_comprehension = (
        visit_expr
    ) = visit_if = compute_first_non_import_node

    def visit_functiondef(
        self, node: nodes.FunctionDef | nodes.While | nodes.For | nodes.ClassDef
    ) -> None:
        # If it is the first non import instruction of the module, record it.
        if self._first_non_import_node:
            return

        # Check if the node belongs to an `If` or a `Try` block. If they
        # contain imports, skip recording this node.
        if not isinstance(node.parent.scope(), nodes.Module):
            return

        root = node
        while not isinstance(root.parent, nodes.Module):
            root = root.parent

        if isinstance(root, (nodes.If, nodes.Try)):
            if any(root.nodes_of_class((nodes.Import, nodes.ImportFrom))):
                return

        self._first_non_import_node = node

    visit_classdef = visit_for = visit_while = visit_functiondef

    def _check_misplaced_future(self, node: nodes.ImportFrom) -> None:
        basename = node.modname
        if basename == "__future__":
            # check if this is the first non-docstring statement in the module
            prev = node.previous_sibling()
            if prev:
                # consecutive future statements are possible
                if not (
                    isinstance(prev, nodes.ImportFrom) and prev.modname == "__future__"
                ):
                    self.add_message("misplaced-future", node=node)

    def _check_same_line_imports(self, node: nodes.ImportFrom) -> None:
        # Detect duplicate imports on the same line.
        names = (name for name, _ in node.names)
        counter = collections.Counter(names)
        for name, count in counter.items():
            if count > 1:
                self.add_message("reimported", node=node, args=(name, node.fromlineno))

    def _check_position(self, node: ImportNode) -> None:
        """Check `node` import or importfrom node position is correct.

        Send a message  if `node` comes before another instruction
        """
        # if a first non-import instruction has already been encountered,
        # it means the import comes after it and therefore is not well placed
        if self._first_non_import_node:
            if self.linter.is_message_enabled(
                "wrong-import-position", self._first_non_import_node.fromlineno
            ):
                self.add_message(
                    "wrong-import-position", node=node, args=node.as_string()
                )
            else:
                self.linter.add_ignored_message(
                    "wrong-import-position", node.fromlineno, node
                )

    def _record_import(
        self,
        node: ImportNode,
        importedmodnode: nodes.Module | None,
    ) -> None:
        """Record the package `node` imports from."""
        if isinstance(node, nodes.ImportFrom):
            importedname = node.modname
        else:
            importedname = importedmodnode.name if importedmodnode else None
        if not importedname:
            importedname = node.names[0][0].split(".")[0]

        if isinstance(node, nodes.ImportFrom) and (node.level or 0) >= 1:
            # We need the importedname with first point to detect local package
            # Example of node:
            #  'from .my_package1 import MyClass1'
            #  the output should be '.my_package1' instead of 'my_package1'
            # Example of node:
            #  'from . import my_package2'
            #  the output should be '.my_package2' instead of '{pyfile}'
            importedname = "." + importedname

        self._imports_stack.append((node, importedname))

    @staticmethod
    def _is_fallback_import(
        node: ImportNode, imports: list[tuple[ImportNode, str]]
    ) -> bool:
        imports = [import_node for (import_node, _) in imports]
        return any(astroid.are_exclusive(import_node, node) for import_node in imports)

    @property
    def _isort_config(self) -> isort.Config:
        """Get the config for use with isort.

        Only valid after CLI parsing finished, i.e. not in __init__
        """
        return isort.Config(
            # There is no typo here. EXTRA_standard_library is
            # what most users want. The option has been named
            # KNOWN_standard_library for ages in pylint, and we
            # don't want to break compatibility.
            extra_standard_library=self.linter.config.known_standard_library,
            known_third_party=self.linter.config.known_third_party,
        )

    def _check_imports_order(self, _module_node: nodes.Module) -> tuple[
        list[tuple[ImportNode, str]],
        list[tuple[ImportNode, str]],
        list[tuple[ImportNode, str]],
    ]:
        """Checks imports of module `node` are grouped by category.

        Imports must follow this order: standard, 3rd party, 1st party, local
        """
        std_imports: list[tuple[ImportNode, str]] = []
        third_party_imports: list[tuple[ImportNode, str]] = []
        first_party_imports: list[tuple[ImportNode, str]] = []
        # need of a list that holds third or first party ordered import
        external_imports: list[tuple[ImportNode, str]] = []
        local_imports: list[tuple[ImportNode, str]] = []
        third_party_not_ignored: list[tuple[ImportNode, str]] = []
        first_party_not_ignored: list[tuple[ImportNode, str]] = []
        local_not_ignored: list[tuple[ImportNode, str]] = []
        for node, modname in self._imports_stack:
            if modname.startswith("."):
                package = "." + modname.split(".")[1]
            else:
                package = modname.split(".")[0]
            nested = not isinstance(node.parent, nodes.Module)
            ignore_for_import_order = not self.linter.is_message_enabled(
                "wrong-import-order", node.fromlineno
            )
            import_category = isort.place_module(package, config=self._isort_config)
            node_and_package_import = (node, package)

            match import_category:
                case "FUTURE" | "STDLIB":
                    std_imports.append(node_and_package_import)
                    wrong_import = (
                        third_party_not_ignored
                        or first_party_not_ignored
                        or local_not_ignored
                    )
                    if self._is_fallback_import(node, wrong_import):
                        continue
                    if wrong_import and not nested:
                        self.add_message(
                            "wrong-import-order",
                            node=node,
                            args=(  ## TODO - this isn't right for multiple on the same line...
                                f'standard import "{self._get_full_import_name((node, package))}"',
                                self._get_out_of_order_string(
                                    third_party_not_ignored,
                                    first_party_not_ignored,
                                    local_not_ignored,
                                ),
                            ),
                        )
                case "THIRDPARTY":
                    third_party_imports.append(node_and_package_import)
                    external_imports.append(node_and_package_import)
                    if not nested:
                        if not ignore_for_import_order:
                            third_party_not_ignored.append(node_and_package_import)
                        else:
                            self.linter.add_ignored_message(
                                "wrong-import-order", node.fromlineno, node
                            )
                    wrong_import = first_party_not_ignored or local_not_ignored
                    if wrong_import and not nested:
                        self.add_message(
                            "wrong-import-order",
                            node=node,
                            args=(
                                f'third party import "{self._get_full_import_name((node, package))}"',
                                self._get_out_of_order_string(
                                    None, first_party_not_ignored, local_not_ignored
                                ),
                            ),
                        )
                case "FIRSTPARTY":
                    first_party_imports.append(node_and_package_import)
                    external_imports.append(node_and_package_import)
                    if not nested:
                        if not ignore_for_import_order:
                            first_party_not_ignored.append(node_and_package_import)
                        else:
                            self.linter.add_ignored_message(
                                "wrong-import-order", node.fromlineno, node
                            )
                    wrong_import = local_not_ignored
                    if wrong_import and not nested:
                        self.add_message(
                            "wrong-import-order",
                            node=node,
                            args=(
                                f'first party import "{self._get_full_import_name((node, package))}"',
                                self._get_out_of_order_string(
                                    None, None, local_not_ignored
                                ),
                            ),
                        )
                case "LOCALFOLDER":
                    local_imports.append((node, package))
                    if not nested:
                        if not ignore_for_import_order:
                            local_not_ignored.append((node, package))
                        else:
                            self.linter.add_ignored_message(
                                "wrong-import-order", node.fromlineno, node
                            )
        return std_imports, external_imports, local_imports

    def _get_out_of_order_string(
        self,
        third_party_imports: list[tuple[ImportNode, str]] | None,
        first_party_imports: list[tuple[ImportNode, str]] | None,
        local_imports: list[tuple[ImportNode, str]] | None,
    ) -> str:
        # construct the string listing out of order imports used in the message
        # for wrong-import-order
        if third_party_imports:
            plural = "s" if len(third_party_imports) > 1 else ""
            if len(third_party_imports) > MAX_NUMBER_OF_IMPORT_SHOWN:
                imports_list = (
                    ", ".join(
                        [
                            f'"{self._get_full_import_name(tpi)}"'
                            for tpi in third_party_imports[
                                : int(MAX_NUMBER_OF_IMPORT_SHOWN // 2)
                            ]
                        ]
                    )
                    + " (...) "
                    + ", ".join(
                        [
                            f'"{self._get_full_import_name(tpi)}"'
                            for tpi in third_party_imports[
                                int(-MAX_NUMBER_OF_IMPORT_SHOWN // 2) :
                            ]
                        ]
                    )
                )
            else:
                imports_list = ", ".join(
                    [
                        f'"{self._get_full_import_name(tpi)}"'
                        for tpi in third_party_imports
                    ]
                )
            third_party = f"third party import{plural} {imports_list}"
        else:
            third_party = ""

        if first_party_imports:
            plural = "s" if len(first_party_imports) > 1 else ""
            if len(first_party_imports) > MAX_NUMBER_OF_IMPORT_SHOWN:
                imports_list = (
                    ", ".join(
                        [
                            f'"{self._get_full_import_name(tpi)}"'
                            for tpi in first_party_imports[
                                : int(MAX_NUMBER_OF_IMPORT_SHOWN // 2)
                            ]
                        ]
                    )
                    + " (...) "
                    + ", ".join(
                        [
                            f'"{self._get_full_import_name(tpi)}"'
                            for tpi in first_party_imports[
                                int(-MAX_NUMBER_OF_IMPORT_SHOWN // 2) :
                            ]
                        ]
                    )
                )
            else:
                imports_list = ", ".join(
                    [
                        f'"{self._get_full_import_name(fpi)}"'
                        for fpi in first_party_imports
                    ]
                )
            first_party = f"first party import{plural} {imports_list}"
        else:
            first_party = ""

        if local_imports:
            plural = "s" if len(local_imports) > 1 else ""
            if len(local_imports) > MAX_NUMBER_OF_IMPORT_SHOWN:
                imports_list = (
                    ", ".join(
                        [
                            f'"{self._get_full_import_name(tpi)}"'
                            for tpi in local_imports[
                                : int(MAX_NUMBER_OF_IMPORT_SHOWN // 2)
                            ]
                        ]
                    )
                    + " (...) "
                    + ", ".join(
                        [
                            f'"{self._get_full_import_name(tpi)}"'
                            for tpi in local_imports[
                                int(-MAX_NUMBER_OF_IMPORT_SHOWN // 2) :
                            ]
                        ]
                    )
                )
            else:
                imports_list = ", ".join(
                    [f'"{self._get_full_import_name(li)}"' for li in local_imports]
                )
            local = f"local import{plural} {imports_list}"
        else:
            local = ""

        delimiter_third_party = (
            (
                ", "
                if (first_party and local)
                else (" and " if (first_party or local) else "")
            )
            if third_party
            else ""
        )
        delimiter_first_party1 = (
            (", " if (third_party and local) else " ") if first_party else ""
        )
        delimiter_first_party2 = ("and " if local else "") if first_party else ""
        delimiter_first_party = f"{delimiter_first_party1}{delimiter_first_party2}"
        msg = (
            f"{third_party}{delimiter_third_party}"
            f"{first_party}{delimiter_first_party}"
            f'{local if local else ""}'
        )

        return msg

    def _get_full_import_name(self, importNode: ImportNode) -> str:
        # construct a more descriptive name of the import
        # for: import X, this returns X
        # for: import X.Y this returns X.Y
        # for: from X import Y, this returns X.Y

        try:
            # this will only succeed for ImportFrom nodes, which in themselves
            # contain the information needed to reconstruct the package
            return f"{importNode[0].modname}.{importNode[0].names[0][0]}"
        except AttributeError:
            # in all other cases, the import will either be X or X.Y
            node: str = importNode[0].names[0][0]
            package: str = importNode[1]

            if node.split(".")[0] == package:
                # this is sufficient with one import per line, since package = X
                # and node = X.Y or X
                return node

            # when there is a node that contains multiple imports, the "current"
            # import being analyzed is specified by package (node is the first
            # import on the line and therefore != package in this case)
            return package

    def _get_imported_module(
        self, importnode: ImportNode, modname: str
    ) -> nodes.Module | None:
        try:
            return importnode.do_import_module(modname)
        except astroid.TooManyLevelsError:
            if _ignore_import_failure(importnode, modname, self._ignored_modules):
                return None
            self.add_message("relative-beyond-top-level", node=importnode)
        except astroid.AstroidSyntaxError as exc:
            message = f"Cannot import {modname!r} due to '{exc.error}'"
            self.add_message(
                "syntax-error", line=importnode.lineno, args=message, confidence=HIGH
            )

        except astroid.AstroidBuildingError:
            if not self.linter.is_message_enabled("import-error"):
                return None
            if _ignore_import_failure(importnode, modname, self._ignored_modules):
                return None
            if (
                not self.linter.config.analyse_fallback_blocks
                and is_from_fallback_block(importnode)
            ):
                return None

            dotted_modname = get_import_name(importnode, modname)
            self.add_message("import-error", args=repr(dotted_modname), node=importnode)
        except Exception as e:  # pragma: no cover
            raise astroid.AstroidError from e
        return None

    def _add_imported_module(self, node: ImportNode, importedmodname: str) -> None:
        """Notify an imported module, used to analyze dependencies."""
        module_file = node.root().file
        context_name = node.root().name
        base = os.path.splitext(os.path.basename(module_file))[0]

        try:
            if isinstance(node, nodes.ImportFrom) and node.level:
                importedmodname = astroid.modutils.get_module_part(
                    importedmodname, module_file
                )
            else:
                importedmodname = astroid.modutils.get_module_part(importedmodname)
        except ImportError:
            pass

        if context_name == importedmodname:
            self.add_message("import-self", node=node)

        elif not astroid.modutils.is_stdlib_module(importedmodname):
            # if this is not a package __init__ module
            if base != "__init__" and context_name not in self._module_pkg:
                # record the module's parent, or the module itself if this is
                # a top level module, as the package it belongs to
                self._module_pkg[context_name] = context_name.rsplit(".", 1)[0]

            # handle dependencies
            dependencies_stat: dict[str, set[str]] = self.linter.stats.dependencies
            importedmodnames = dependencies_stat.setdefault(importedmodname, set())
            if context_name not in importedmodnames:
                importedmodnames.add(context_name)

            # update import graph
            self.import_graph[context_name].add(importedmodname)
            if not self.linter.is_message_enabled(
                "cyclic-import", line=node.lineno
            ) or in_type_checking_block(node):
                self._excluded_edges[context_name].add(importedmodname)

    def _check_preferred_module(self, node: ImportNode, mod_path: str) -> None:
        """Check if the module has a preferred replacement."""
        mod_compare = [mod_path]
        # build a comparison list of possible names using importfrom
        if isinstance(node, nodes.ImportFrom):
            mod_compare = [f"{node.modname}.{name[0]}" for name in node.names]

        # find whether there are matches with the import vs preferred_modules keys
        matches = [
            k
            for k in self.preferred_modules
            for mod in mod_compare
            # exact match
            if k == mod
            # checks for base module matches
            or k in mod.split(".")[0]
        ]

        # if we have matches, add message
        if matches:
            self.add_message(
                "preferred-module",
                node=node,
                args=(self.preferred_modules[matches[0]], matches[0]),
            )

    def _check_import_as_rename(self, node: ImportNode) -> None:
        names = node.names
        for name in names:
            if not all(name):
                return

            splitted_packages = name[0].rsplit(".", maxsplit=1)
            import_name = splitted_packages[-1]
            aliased_name = name[1]
            if import_name != aliased_name:
                continue

            if len(splitted_packages) == 1 and (
                self._allow_reexport_package is False
                or self._current_module_package is False
            ):
                self.add_message("useless-import-alias", node=node, confidence=HIGH)
            elif len(splitted_packages) == 2:
                self.add_message(
                    "consider-using-from-import",
                    node=node,
                    args=(splitted_packages[0], import_name),
                )

    def _check_reimport(
        self,
        node: ImportNode,
        basename: str | None = None,
        level: int | None = None,
    ) -> None:
        """Check if a module with the same name is already imported or aliased."""
        if not self.linter.is_message_enabled(
            "reimported"
        ) and not self.linter.is_message_enabled("shadowed-import"):
            return

        frame = node.frame()
        root = node.root()
        contexts = [(frame, level)]
        if root is not frame:
            contexts.append((root, None))

        for known_context, known_level in contexts:
            for name, alias in node.names:
                first, msg = _get_first_import(
                    node, known_context, name, basename, known_level, alias
                )
                if first is not None and msg is not None:
                    name = name if msg == "reimported" else alias
                    self.add_message(
                        msg, node=node, args=(name, first.fromlineno), confidence=HIGH
                    )

    def _report_external_dependencies(
        self, sect: Section, _: LinterStats, _dummy: LinterStats | None
    ) -> None:
        """Return a verbatim layout for displaying dependencies."""
        dep_info = _make_tree_defs(self._external_dependencies_info.items())
        if not dep_info:
            raise EmptyReportError()
        tree_str = _repr_tree_defs(dep_info)
        sect.append(VerbatimText(tree_str))

    def _report_dependencies_graph(
        self, sect: Section, _: LinterStats, _dummy: LinterStats | None
    ) -> None:
        """Write dependencies as a dot (graphviz) file."""
        dep_info = self.linter.stats.dependencies
        if not (
            dep_info
            and (
                self.linter.config.import_graph
                or self.linter.config.ext_import_graph
                or self.linter.config.int_import_graph
            )
        ):
            raise EmptyReportError()
        filename = self.linter.config.import_graph
        if filename:
            _make_graph(filename, dep_info, sect, "")
        filename = self.linter.config.ext_import_graph
        if filename:
            _make_graph(filename, self._external_dependencies_info, sect, "external ")
        filename = self.linter.config.int_import_graph
        if filename:
            _make_graph(filename, self._internal_dependencies_info, sect, "internal ")

    def _filter_dependencies_graph(self, internal: bool) -> defaultdict[str, set[str]]:
        """Build the internal or the external dependency graph."""
        graph: defaultdict[str, set[str]] = defaultdict(set)
        for importee, importers in self.linter.stats.dependencies.items():
            for importer in importers:
                package = self._module_pkg.get(importer, importer)
                is_inside = importee.startswith(package)
                if (is_inside and internal) or (not is_inside and not internal):
                    graph[importee].add(importer)
        return graph

    @cached_property
    def _external_dependencies_info(self) -> defaultdict[str, set[str]]:
        """Return cached external dependencies information or build and
        cache them.
        """
        return self._filter_dependencies_graph(internal=False)

    @cached_property
    def _internal_dependencies_info(self) -> defaultdict[str, set[str]]:
        """Return cached internal dependencies information or build and
        cache them.
        """
        return self._filter_dependencies_graph(internal=True)

    def _check_wildcard_imports(
        self, node: nodes.ImportFrom, imported_module: nodes.Module | None
    ) -> None:
        if node.root().package:
            # Skip the check if in __init__.py issue #2026
            return

        wildcard_import_is_allowed = self._wildcard_import_is_allowed(imported_module)
        for name, _ in node.names:
            if name == "*" and not wildcard_import_is_allowed:
                self.add_message("wildcard-import", args=node.modname, node=node)

    def _wildcard_import_is_allowed(self, imported_module: nodes.Module | None) -> bool:
        return (
            self.linter.config.allow_wildcard_with_all
            and imported_module is not None
            and "__all__" in imported_module.locals
        )

    def _check_toplevel(self, node: ImportNode) -> None:
        """Check whether the import is made outside the module toplevel."""
        # If the scope of the import is a module, then obviously it is
        # not outside the module toplevel.
        if isinstance(node.scope(), nodes.Module):
            return

        module_names = [
            (
                f"{node.modname}.{name[0]}"
                if isinstance(node, nodes.ImportFrom)
                else name[0]
            )
            for name in node.names
        ]

        # Get the full names of all the imports that are only allowed at the module level
        scoped_imports = [
            name for name in module_names if name not in self._allow_any_import_level
        ]

        if scoped_imports:
            self.add_message(
                "import-outside-toplevel", args=", ".join(scoped_imports), node=node
            )


def register(linter: PyLinter) -> None:
    linter.register_checker(ImportsChecker(linter))
