from typing import List, Optional

from xsdata.codegen.container import ClassContainer
from xsdata.codegen.models import Attr, Class, Extension, get_tag
from xsdata.codegen.utils import ClassUtils
from xsdata.logger import logger
from xsdata.models.enums import Tag
from xsdata.utils import collections
from xsdata.utils.collections import group_by


class ClassValidator:
    """Run validations against the class container in order to remove or merge
    invalid or redefined types."""

    __slots__ = "container"

    def __init__(self, container: ClassContainer):
        self.container = container

    def process(self):
        """
        Remove if possible classes with the same qualified name.

        Steps:
            1. Remove invalid classes
            2. Handle duplicate types
            3. Merge dummy types
        """
        for classes in self.container.data.values():
            if len(classes) > 1:
                self.remove_invalid_classes(classes)

            if len(classes) > 1:
                self.handle_duplicate_types(classes)

            if len(classes) > 1:
                self.merge_global_types(classes)

    def remove_invalid_classes(self, classes: List[Class]):
        """Remove from the given class list any class with missing extension
        type."""

        def is_invalid(ext: Extension) -> bool:
            """Check if given type declaration is not native and is missing."""
            return not ext.type.native and ext.type.qname not in self.container.data

        for target in list(classes):
            if any(is_invalid(extension) for extension in target.extensions):
                classes.remove(target)

    @classmethod
    def handle_duplicate_types(cls, classes: List[Class]):
        """Handle classes with same namespace, name that are derived from the
        same xs type."""

        for items in group_by(classes, get_tag).values():
            if len(items) == 1:
                continue

            index = cls.select_winner(list(items))

            if index == -1:
                logger.warning(
                    "Duplicate type %s, will keep the last defined",
                    items[0].qname,
                )

            winner = items.pop(index)

            for item in items:
                classes.remove(item)

                if winner.container == Tag.REDEFINE:
                    cls.merge_redefined_type(item, winner)

    @classmethod
    def merge_redefined_type(cls, source: Class, target: Class):
        """
        Copy any attributes and extensions to redefined types from the original
        definitions.

        Redefined inheritance is optional search for self references in
        extensions and attribute groups.
        """
        circular_extension = cls.find_circular_extension(target)
        circular_group = cls.find_circular_group(target)

        if circular_extension:
            ClassUtils.copy_attributes(source, target, circular_extension)
            ClassUtils.copy_extensions(source, target, circular_extension)

        if circular_group:
            ClassUtils.copy_group_attributes(source, target, circular_group)

    @classmethod
    def select_winner(cls, candidates: List[Class]) -> int:
        """
        Returns the index of the class that will survive the duplicate process.

        Classes that were extracted from in xs:override/xs:redefined
        containers have priority, otherwise pick the last in the list.
        """
        for index, item in enumerate(candidates):
            if item.container in (Tag.OVERRIDE, Tag.REDEFINE):
                return index

        return -1

    @classmethod
    def find_circular_extension(cls, target: Class) -> Optional[Extension]:
        """Search for any target class extensions that is a circular
        reference."""
        for ext in target.extensions:
            if ext.type.name == target.name:
                return ext

        return None

    @classmethod
    def find_circular_group(cls, target: Class) -> Optional[Attr]:
        """Search for any target class attributes that is a circular
        reference."""
        return ClassUtils.find_attr(target, target.name)

    @classmethod
    def merge_global_types(cls, classes: List[Class]):
        """
        Merge parent-child global types.

        Conditions
            1. One of them is derived from xs:element
            2. One of them is derived from xs:complexType
            3. The xs:element is a subclass of the xs:complexType
            4. The xs:element has no attributes (This can't happen in a valid schema)
        """
        el = collections.first(x for x in classes if x.tag == Tag.ELEMENT)
        ct = collections.first(x for x in classes if x.tag == Tag.COMPLEX_TYPE)

        if (
            el is None
            or ct is None
            or el is ct
            or el.attrs
            or len(el.extensions) != 1
            or el.extensions[0].type.qname != el.qname
        ):
            return

        ct.namespace = el.namespace or ct.namespace
        ct.help = el.help or ct.help
        ct.substitutions = el.substitutions
        classes.remove(el)