from __future__ import annotations

import importlib
import os
import pkgutil
import re
import sys
import token
import tokenize
from importlib.machinery import FileFinder
from io import StringIO
from contextlib import contextmanager
from dataclasses import dataclass
from itertools import chain
from tokenize import TokenInfo

TYPE_CHECKING = False

if TYPE_CHECKING:
    from types import ModuleType
    from typing import Any, Iterable, Iterator, Mapping
    from .types import CompletionAction


HARDCODED_SUBMODULES = {
    # Standard library submodules that are not detected by pkgutil.iter_modules
    # but can be imported, so should be proposed in completion
    "collections": ["abc"],
    "math": ["integer"],
    "os": ["path"],
    "xml.parsers.expat": ["errors", "model"],
}

AUTO_IMPORT_DENYLIST = {
    # Standard library modules/submodules that have import side effects
    # and must not be automatically imported to complete attributes
    re.compile(r"antigravity"),  # Calls webbrowser.open
    re.compile(r"idlelib\..+"),  # May open IDLE GUI
    re.compile(r"test\..+"),  # Various side-effects
    re.compile(r"this"),  # Prints to stdout
    re.compile(r"_ios_support"),  # Spawns a subprocess
    re.compile(r".+\.__main__"),  # Should not be imported
}


def make_default_module_completer() -> ModuleCompleter:
    # Inside pyrepl, __package__ is set to None by default
    return ModuleCompleter(namespace={'__package__': None})


class ModuleCompleter:
    """A completer for Python import statements.

    Examples:
        - import <tab>
        - import foo<tab>
        - import foo.<tab>
        - import foo as bar, baz<tab>

        - from <tab>
        - from foo<tab>
        - from foo import <tab>
        - from foo import bar<tab>
        - from foo import (bar as baz, qux<tab>
    """

    def __init__(self, namespace: Mapping[str, Any] | None = None) -> None:
        self.namespace = namespace or {}
        self._global_cache: list[pkgutil.ModuleInfo] = []
        self._failed_imports: set[str] = set()
        self._curr_sys_path: list[str] = sys.path[:]
        self._stdlib_path = os.path.dirname(importlib.__path__[0])

    def get_completions(self, line: str) -> tuple[list[str], CompletionAction | None] | None:
        """Return the next possible import completions for 'line'.

        For attributes completion, if the module to complete from is not
        imported, also return an action (prompt + callback to run if the
        user press TAB again) to import the module.
        """
        result = ImportParser(line).parse()
        if not result:
            return None
        try:
            return self.complete(*result)
        except Exception:
            # Some unexpected error occurred, make it look like
            # no completions are available
            return [], None

    def complete(self, from_name: str | None, name: str | None) -> tuple[list[str], CompletionAction | None]:
        if from_name is None:
            # import x.y.z<tab>
            assert name is not None
            path, prefix = self.get_path_and_prefix(name)
            modules = self.find_modules(path, prefix)
            return [self.format_completion(path, module) for module in modules], None

        if name is None:
            # from x.y.z<tab>
            path, prefix = self.get_path_and_prefix(from_name)
            modules = self.find_modules(path, prefix)
            return [self.format_completion(path, module) for module in modules], None

        # from x.y import z<tab>
        submodules = self.find_modules(from_name, name)
        attributes, action = self.find_attributes(from_name, name)
        return sorted({*submodules, *attributes}), action

    def find_modules(self, path: str, prefix: str) -> list[str]:
        """Find all modules under 'path' that start with 'prefix'."""
        modules = self._find_modules(path, prefix)
        # Filter out invalid module names
        # (for example those containing dashes that cannot be imported with 'import')
        return [mod for mod in modules if mod.isidentifier()]

    def _find_modules(self, path: str, prefix: str) -> list[str]:
        if not path:
            # Top-level import (e.g. `import foo<tab>`` or `from foo<tab>`)`
            builtin_modules = [name for name in sys.builtin_module_names
                               if self.is_suggestion_match(name, prefix)]
            third_party_modules = [module.name for module in self.global_cache
                                   if self.is_suggestion_match(module.name, prefix)]
            return sorted(builtin_modules + third_party_modules)

        path = self._resolve_relative_path(path)  # type: ignore[assignment]
        if path is None:
            return []

        modules: Iterable[pkgutil.ModuleInfo] = self.global_cache
        imported_module = sys.modules.get(path.split('.')[0])
        if imported_module:
            # Filter modules to those whose name and specs match the
            # imported module to avoid invalid suggestions
            spec = imported_module.__spec__
            if spec:
                def _safe_find_spec(mod: pkgutil.ModuleInfo) -> bool:
                    try:
                        return mod.module_finder.find_spec(mod.name, None) == spec
                    except Exception:
                        return False
                modules = [mod for mod in modules
                           if mod.name == spec.name
                           and _safe_find_spec(mod)]
            else:
                modules = []

        is_stdlib_import: bool | None = None
        for segment in path.split('.'):
            modules = [mod_info for mod_info in modules
                       if mod_info.ispkg and mod_info.name == segment]
            if is_stdlib_import is None:
                # Top-level import decide if we import from stdlib or not
                is_stdlib_import = all(
                    self._is_stdlib_module(mod_info) for mod_info in modules
                )
            modules = self.iter_submodules(modules)

        module_names = [module.name for module in modules]
        if is_stdlib_import:
            module_names.extend(HARDCODED_SUBMODULES.get(path, ()))
        return [module_name for module_name in module_names
                if self.is_suggestion_match(module_name, prefix)]

    def _is_stdlib_module(self, module_info: pkgutil.ModuleInfo) -> bool:
        return (isinstance(module_info.module_finder, FileFinder)
                and module_info.module_finder.path == self._stdlib_path)

    def find_attributes(self, path: str, prefix: str) -> tuple[list[str], CompletionAction | None]:
        """Find all attributes of module 'path' that start with 'prefix'."""
        attributes, action = self._find_attributes(path, prefix)
        # Filter out invalid attribute names
        # (for example those containing dashes that cannot be imported with 'import')
        return [attr for attr in attributes if attr.isidentifier()], action

    def _find_attributes(self, path: str, prefix: str) -> tuple[list[str], CompletionAction | None]:
        path = self._resolve_relative_path(path)  # type: ignore[assignment]
        if path is None:
            return [], None

        imported_module = sys.modules.get(path)
        if not imported_module:
            if path in self._failed_imports:  # Do not propose to import again
                return [], None
            imported_module = self._maybe_import_module(path)
        if not imported_module:
            return [], self._get_import_completion_action(path)
        try:
            module_attributes = dir(imported_module)
        except Exception:
            module_attributes = []
        return [attr_name for attr_name in module_attributes
                if self.is_suggestion_match(attr_name, prefix)], None

    def is_suggestion_match(self, module_name: str, prefix: str) -> bool:
        if prefix:
            return module_name.startswith(prefix)
        # For consistency with attribute completion, which
        # does not suggest private attributes unless requested.
        return not module_name.startswith("_")

    def iter_submodules(self, parent_modules: list[pkgutil.ModuleInfo]) -> Iterator[pkgutil.ModuleInfo]:
        """Iterate over all submodules of the given parent modules."""
        specs = [info.module_finder.find_spec(info.name, None)
                 for info in parent_modules if info.ispkg]
        search_locations = set(chain.from_iterable(
            getattr(spec, 'submodule_search_locations', [])
            for spec in specs if spec
        ))
        return pkgutil.iter_modules(search_locations)

    def get_path_and_prefix(self, dotted_name: str) -> tuple[str, str]:
        """
        Split a dotted name into an import path and a
        final prefix that is to be completed.

        Examples:
            'foo.bar' -> 'foo', 'bar'
            'foo.' -> 'foo', ''
            '.foo' -> '.', 'foo'
        """
        if '.' not in dotted_name:
            return '', dotted_name
        if dotted_name.startswith('.'):
            stripped = dotted_name.lstrip('.')
            dots = '.' * (len(dotted_name) - len(stripped))
            if '.' not in stripped:
                return dots, stripped
            path, prefix = stripped.rsplit('.', 1)
            return dots + path, prefix
        path, prefix = dotted_name.rsplit('.', 1)
        return path, prefix

    def format_completion(self, path: str, module: str) -> str:
        if path == '' or path.endswith('.'):
            return f'{path}{module}'
        return f'{path}.{module}'

    def _resolve_relative_path(self, path: str) -> str | None:
        """Resolve a relative import path to absolute. Returns None if unresolvable."""
        if path.startswith('.'):
            package = self.namespace.get('__package__', '')
            return self.resolve_relative_name(path, package)
        return path

    def resolve_relative_name(self, name: str, package: str) -> str | None:
        """Resolve a relative module name to an absolute name.

        Example: resolve_relative_name('.foo', 'bar') -> 'bar.foo'
        """
        # taken from importlib._bootstrap
        level = 0
        for character in name:
            if character != '.':
                break
            level += 1
        bits = package.rsplit('.', level - 1)
        if len(bits) < level:
            return None
        base = bits[0]
        name = name[level:]
        return f'{base}.{name}' if name else base

    @property
    def global_cache(self) -> list[pkgutil.ModuleInfo]:
        """Global module cache"""
        if not self._global_cache or self._curr_sys_path != sys.path:
            self._curr_sys_path = sys.path[:]
            self._global_cache = list(pkgutil.iter_modules())
            self._failed_imports.clear()  # retry on sys.path change
        return self._global_cache

    def _maybe_import_module(self, fqname: str) -> ModuleType | None:
        if any(pattern.fullmatch(fqname) for pattern in AUTO_IMPORT_DENYLIST):
            # Special-cased modules with known import side-effects
            return None
        root = fqname.split(".")[0]
        mod_info = next((m for m in self.global_cache if m.name == root), None)
        if not mod_info or not self._is_stdlib_module(mod_info):
            # Only import stdlib modules (no risk of import side-effects)
            return None
        try:
            return importlib.import_module(fqname)
        except Exception:
            sys.modules.pop(fqname, None)  # Clean half-imported module
            return None

    def _get_import_completion_action(self, path: str) -> CompletionAction:
        prompt = ("[ module not imported, press again to import it "
                  "and propose attributes ]")

        def _do_import() -> str | None:
            try:
                importlib.import_module(path)
                return None
            except Exception as exc:
                sys.modules.pop(path, None)  # Clean half-imported module
                self._failed_imports.add(path)
                return f"[ error during import: {exc} ]"

        return (prompt, _do_import)


class ImportParser:
    """
    Parses incomplete import statements that are
    suitable for autocomplete suggestions.

    Examples:
        - import foo          -> Result(from_name=None, name='foo')
        - import foo.         -> Result(from_name=None, name='foo.')
        - from foo            -> Result(from_name='foo', name=None)
        - from foo import bar -> Result(from_name='foo', name='bar')
        - from .foo import (  -> Result(from_name='.foo', name='')

    Note that the parser works in reverse order, starting from the
    last token in the input string. This makes the parser more robust
    when parsing multiple statements.
    """
    _ignored_tokens = {
        token.INDENT, token.DEDENT, token.COMMENT,
        token.NL, token.NEWLINE, token.ENDMARKER
    }
    _keywords = {'import', 'from', 'as'}

    def __init__(self, code: str) -> None:
        self.code = code
        tokens = []
        try:
            for t in tokenize.generate_tokens(StringIO(code).readline):
                if t.type not in self._ignored_tokens:
                    tokens.append(t)
        except tokenize.TokenError as e:
            if 'unexpected EOF' not in str(e):
                # unexpected EOF is fine, since we're parsing an
                # incomplete statement, but other errors are not
                # because we may not have all the tokens so it's
                # safer to bail out
                tokens = []
        except SyntaxError:
            tokens = []
        self.tokens = TokenQueue(tokens[::-1])

    def parse(self) -> tuple[str | None, str | None] | None:
        if not (res := self._parse()):
            return None
        return res.from_name, res.name

    def _parse(self) -> Result | None:
        with self.tokens.save_state():
            return self.parse_from_import()
        with self.tokens.save_state():
            return self.parse_import()

    def parse_import(self) -> Result:
        if self.code.rstrip().endswith('import') and self.code.endswith(' '):
            return Result(name='')
        if self.tokens.peek_string(','):
            name = ''
        else:
            if self.code.endswith(' '):
                raise ParseError('parse_import')
            name = self.parse_dotted_name()
        if name.startswith('.'):
            raise ParseError('parse_import')
        while self.tokens.peek_string(','):
            self.tokens.pop()
            self.parse_dotted_as_name()
        if self.tokens.peek_string('import'):
            return Result(name=name)
        raise ParseError('parse_import')

    def parse_from_import(self) -> Result:
        stripped = self.code.rstrip()
        if stripped.endswith('import') and self.code.endswith(' '):
            return Result(from_name=self.parse_empty_from_import(), name='')
        if stripped.endswith('from') and self.code.endswith(' '):
            return Result(from_name='')
        if self.tokens.peek_string('(') or self.tokens.peek_string(','):
            return Result(from_name=self.parse_empty_from_import(), name='')
        if self.code.endswith(' '):
            raise ParseError('parse_from_import')
        name = self.parse_dotted_name()
        if '.' in name:
            self.tokens.pop_string('from')
            return Result(from_name=name)
        if self.tokens.peek_string('from'):
            return Result(from_name=name)
        from_name = self.parse_empty_from_import()
        return Result(from_name=from_name, name=name)

    def parse_empty_from_import(self) -> str:
        if self.tokens.peek_string(','):
            self.tokens.pop()
            self.parse_as_names()
        if self.tokens.peek_string('('):
            self.tokens.pop()
        self.tokens.pop_string('import')
        return self.parse_from()

    def parse_from(self) -> str:
        from_name = self.parse_dotted_name()
        self.tokens.pop_string('from')
        return from_name

    def parse_dotted_as_name(self) -> str:
        self.tokens.pop_name()
        if self.tokens.peek_string('as'):
            self.tokens.pop()
        with self.tokens.save_state():
            return self.parse_dotted_name()

    def parse_dotted_name(self) -> str:
        name = []
        if self.tokens.peek_string('.'):
            name.append('.')
            self.tokens.pop()
        if (self.tokens.peek_name()
            and (tok := self.tokens.peek())
            and tok.string not in self._keywords):
            name.append(self.tokens.pop_name())
        if not name:
            raise ParseError('parse_dotted_name')
        while self.tokens.peek_string('.'):
            name.append('.')
            self.tokens.pop()
            if (self.tokens.peek_name()
                and (tok := self.tokens.peek())
                and tok.string not in self._keywords):
                name.append(self.tokens.pop_name())
            else:
                break

        while self.tokens.peek_string('.'):
            name.append('.')
            self.tokens.pop()
        return ''.join(name[::-1])

    def parse_as_names(self) -> None:
        self.parse_as_name()
        while self.tokens.peek_string(','):
            self.tokens.pop()
            self.parse_as_name()

    def parse_as_name(self) -> None:
        self.tokens.pop_name()
        if self.tokens.peek_string('as'):
            self.tokens.pop()
            self.tokens.pop_name()


class ParseError(Exception):
    pass


@dataclass(frozen=True)
class Result:
    from_name: str | None = None
    name: str | None = None


class TokenQueue:
    """Provides helper functions for working with a sequence of tokens."""

    def __init__(self, tokens: list[TokenInfo]) -> None:
        self.tokens: list[TokenInfo] = tokens
        self.index: int = 0
        self.stack: list[int] = []

    @contextmanager
    def save_state(self) -> Any:
        try:
            self.stack.append(self.index)
            yield
        except ParseError:
            self.index = self.stack.pop()
        else:
            self.stack.pop()

    def __bool__(self) -> bool:
        return self.index < len(self.tokens)

    def peek(self) -> TokenInfo | None:
        if not self:
            return None
        return self.tokens[self.index]

    def peek_name(self) -> bool:
        if not (tok := self.peek()):
            return False
        return tok.type == token.NAME

    def pop_name(self) -> str:
        tok = self.pop()
        if tok.type != token.NAME:
            raise ParseError('pop_name')
        return tok.string

    def peek_string(self, string: str) -> bool:
        if not (tok := self.peek()):
            return False
        return tok.string == string

    def pop_string(self, string: str) -> str:
        tok = self.pop()
        if tok.string != string:
            raise ParseError('pop_string')
        return tok.string

    def pop(self) -> TokenInfo:
        if not self:
            raise ParseError('pop')
        tok = self.tokens[self.index]
        self.index += 1
        return tok
