# Source code for openpyxl.descriptors.sequence

    # Copyright (c) 2010-2024 openpyxl

    from openpyxl.compat import safe_string
    from openpyxl.xml.functions import Element
    from openpyxl.utils.indexed_list import IndexedList

    from .base import Descriptor, Alias, _convert
    from .namespace import namespaced

    class Sequence(Descriptor):
        """
        A sequence (list or tuple) that may only contain objects of the declared
        type
        """

        expected_type = type(None)
        seq_types = (list, tuple)
        idx_base = 0
        unique = False
        container = list

        def __set__(self, instance, seq):
            if not isinstance(seq, self.seq_types):
                raise TypeError("Value must be a sequence")
            seq = self.container(_convert(self.expected_type, value) for value in seq)
            if self.unique:
                seq = IndexedList(seq)

            super().__set__(instance, seq)

        def to_tree(self, tagname, obj, namespace=None):
            """
            Convert the sequence represented by the descriptor to an XML element
            """
            for idx, v in enumerate(obj, self.idx_base):
                if hasattr(v, "to_tree"):
                    el = v.to_tree(tagname, idx)
                else:
                    tagname = namespaced(obj, tagname, namespace)
                    el = Element(tagname)
                    el.text = safe_string(v)
                yield el

    class UniqueSequence(Sequence):
        """
        Use a set to keep values unique
        """
        seq_types = (list, tuple, set)
        container = set

    class ValueSequence(Sequence):
        """
        A sequence of primitive types that are stored as a single attribute.
        "val" is the default attribute
        """

        attribute = "val"

        def to_tree(self, tagname, obj, namespace=None):
            tagname = namespaced(self, tagname, namespace)
            for v in obj:
                yield Element(tagname, {self.attribute:safe_string(v)})

        def from_tree(self, node):

            return node.get(self.attribute)

    class NestedSequence(Sequence):
        """
        Wrap a sequence in an containing object
        """

        count = False

        def to_tree(self, tagname, obj, namespace=None):
            tagname = namespaced(self, tagname, namespace)
            container = Element(tagname)
            if self.count:
                container.set('count', str(len(obj)))
            for v in obj:
                container.append(v.to_tree())
            return container

        def from_tree(self, node):
            return [self.expected_type.from_tree(el) for el in node]

    class MultiSequence(Sequence):
        """
        Sequences can contain objects with different tags
        """

        def __set__(self, instance, seq):
            if not isinstance(seq, (tuple, list)):
                raise ValueError("Value must be a sequence")
            seq = list(seq)
            Descriptor.__set__(self, instance, seq)

        def to_tree(self, tagname, obj, namespace=None):
            """
            Convert the sequence represented by the descriptor to an XML element
            """
            for v in obj:
                el = v.to_tree(namespace=namespace)
                yield el

    class MultiSequencePart(Alias):
        """
        Allow a multisequence to be built up from parts

        Excluded from the instance __elements__ or __attrs__ as is effectively an Alias
        """

        def __init__(self, expected_type, store):
            self.expected_type = expected_type
            self.store = store

        def __set__(self, instance, value):
            value = _convert(self.expected_type, value)
            instance.__dict__[self.store].append(value)

        def __get__(self, instance, cls):
            return self