import ast

from mccabe import PathGraphingAstVisitor

from prospector.encoding import CouldNotHandleEncoding, read_py_file
from prospector.message import Location, Message, make_tool_error_message
from prospector.tools.base import ToolBase

__all__ = ("McCabeTool",)


class McCabeTool(ToolBase):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.ignore_codes = ()
        self.max_complexity = 10

    def configure(self, prospector_config, _):
        self.ignore_codes = prospector_config.get_disabled_messages("mccabe")

        options = prospector_config.tool_options("mccabe")
        if "max-complexity" in options:
            self.max_complexity = options["max-complexity"]

    def run(self, found_files):
        messages = []

        for code_file in found_files.python_modules:
            try:
                contents = read_py_file(code_file)
                tree = ast.parse(
                    contents,
                    filename=code_file,
                )
            except CouldNotHandleEncoding as err:
                messages.append(
                    make_tool_error_message(
                        code_file,
                        "mccabe",
                        "MC0000",
                        message=f"Could not handle the encoding of this file: {err.encoding}",
                    )
                )
                continue
            except SyntaxError as err:
                messages.append(
                    make_tool_error_message(
                        code_file,
                        "mccabe",
                        "MC0000",
                        line=err.lineno,
                        character=err.offset,
                        message="Syntax Error",
                    )
                )
                continue
            except TypeError:
                messages.append(make_tool_error_message(code_file, "mccabe", "MC0000", message="Unable to parse file"))
                continue

            visitor = PathGraphingAstVisitor()
            visitor.preorder(tree, visitor)

            for graph in visitor.graphs.values():
                complexity = graph.complexity()
                if complexity > self.max_complexity:
                    location = Location(
                        path=code_file, module=None, function=graph.entity, line=graph.lineno, character=0
                    )
                    message = Message(
                        source="mccabe",
                        code="MC0001",
                        location=location,
                        message=f"{graph.entity} is too complex ({complexity})",
                    )
                    messages.append(message)

        return self.filter_messages(messages)

    def filter_messages(self, messages):
        return [message for message in messages if message.code not in self.ignore_codes]