import magic
from django.utils.text import slugify
from rest_framework import serializers
from rest_framework.fields import SerializerMethodField

from . import bulk_edit
from .models import Correspondent, Tag, Document, Log, DocumentType, \
    SavedView, SavedViewFilterRule
from .parsers import is_mime_type_supported

from django.utils.translation import gettext as _


# https://www.django-rest-framework.org/api-guide/serializers/#example
class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    """
    A ModelSerializer that takes an additional `fields` argument that
    controls which fields should be displayed.
    """

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

        # Instantiate the superclass normally
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

        if fields is not None:
            # Drop any fields that are not specified in the `fields` argument.
            allowed = set(fields)
            existing = set(self.fields)
            for field_name in existing - allowed:
                self.fields.pop(field_name)


class CorrespondentSerializer(serializers.ModelSerializer):

    document_count = serializers.IntegerField(read_only=True)

    last_correspondence = serializers.DateTimeField(read_only=True)

    def get_slug(self, obj):
        return slugify(obj.name)
    slug = SerializerMethodField()

    class Meta:
        model = Correspondent
        fields = (
            "id",
            "slug",
            "name",
            "match",
            "matching_algorithm",
            "is_insensitive",
            "document_count",
            "last_correspondence"
        )


class DocumentTypeSerializer(serializers.ModelSerializer):

    document_count = serializers.IntegerField(read_only=True)

    def get_slug(self, obj):
        return slugify(obj.name)
    slug = SerializerMethodField()

    class Meta:
        model = DocumentType
        fields = (
            "id",
            "slug",
            "name",
            "match",
            "matching_algorithm",
            "is_insensitive",
            "document_count"
        )


class TagSerializer(serializers.ModelSerializer):

    document_count = serializers.IntegerField(read_only=True)

    def get_slug(self, obj):
        return slugify(obj.name)
    slug = SerializerMethodField()

    class Meta:
        model = Tag
        fields = (
            "id",
            "slug",
            "name",
            "colour",
            "match",
            "matching_algorithm",
            "is_insensitive",
            "is_inbox_tag",
            "document_count"
        )


class CorrespondentField(serializers.PrimaryKeyRelatedField):
    def get_queryset(self):
        return Correspondent.objects.all()


class TagsField(serializers.PrimaryKeyRelatedField):
    def get_queryset(self):
        return Tag.objects.all()


class DocumentTypeField(serializers.PrimaryKeyRelatedField):
    def get_queryset(self):
        return DocumentType.objects.all()


class DocumentSerializer(DynamicFieldsModelSerializer):

    correspondent = CorrespondentField(allow_null=True)
    tags = TagsField(many=True)
    document_type = DocumentTypeField(allow_null=True)

    original_file_name = SerializerMethodField()
    archived_file_name = SerializerMethodField()

    def get_original_file_name(self, obj):
        return obj.get_public_filename()

    def get_archived_file_name(self, obj):
        if obj.archive_checksum:
            return obj.get_public_filename(archive=True)
        else:
            return None

    class Meta:
        model = Document
        depth = 1
        fields = (
            "id",
            "correspondent",
            "document_type",
            "title",
            "content",
            "tags",
            "created",
            "modified",
            "added",
            "archive_serial_number",
            "original_file_name",
            "archived_file_name",
        )


class LogSerializer(serializers.ModelSerializer):

    class Meta:
        model = Log
        fields = (
            "id",
            "created",
            "message",
            "group",
            "level"
        )


class SavedViewFilterRuleSerializer(serializers.ModelSerializer):

    class Meta:
        model = SavedViewFilterRule
        fields = ["rule_type", "value"]


class SavedViewSerializer(serializers.ModelSerializer):

    filter_rules = SavedViewFilterRuleSerializer(many=True)

    class Meta:
        model = SavedView
        depth = 1
        fields = ["id", "name", "show_on_dashboard", "show_in_sidebar",
                  "sort_field", "sort_reverse", "filter_rules"]

    def update(self, instance, validated_data):
        if 'filter_rules' in validated_data:
            rules_data = validated_data.pop('filter_rules')
        else:
            rules_data = None
        super(SavedViewSerializer, self).update(instance, validated_data)
        if rules_data is not None:
            SavedViewFilterRule.objects.filter(saved_view=instance).delete()
            for rule_data in rules_data:
                SavedViewFilterRule.objects.create(
                    saved_view=instance, **rule_data)
        return instance

    def create(self, validated_data):
        rules_data = validated_data.pop('filter_rules')
        saved_view = SavedView.objects.create(**validated_data)
        for rule_data in rules_data:
            SavedViewFilterRule.objects.create(
                saved_view=saved_view, **rule_data)
        return saved_view


class BulkEditSerializer(serializers.Serializer):

    documents = serializers.ListField(
        child=serializers.IntegerField(),
        label="Documents",
        write_only=True
    )

    method = serializers.ChoiceField(
        choices=[
            "set_correspondent",
            "set_document_type",
            "add_tag",
            "remove_tag",
            "modify_tags",
            "delete"
        ],
        label="Method",
        write_only=True,
    )

    parameters = serializers.DictField(allow_empty=True)

    def _validate_document_id_list(self, documents, name="documents"):
        if not type(documents) == list:
            raise serializers.ValidationError(f"{name} must be a list")
        if not all([type(i) == int for i in documents]):
            raise serializers.ValidationError(
                f"{name} must be a list of integers")
        count = Document.objects.filter(id__in=documents).count()
        if not count == len(documents):
            raise serializers.ValidationError(
                f"Some documents in {name} don't exist or were "
                f"specified twice.")

    def _validate_tag_id_list(self, tags, name="tags"):
        if not type(tags) == list:
            raise serializers.ValidationError(f"{name} must be a list")
        if not all([type(i) == int for i in tags]):
            raise serializers.ValidationError(
                f"{name} must be a list of integers")
        count = Tag.objects.filter(id__in=tags).count()
        if not count == len(tags):
            raise serializers.ValidationError(
                f"Some tags in {name} don't exist or were specified twice.")

    def validate_documents(self, documents):
        self._validate_document_id_list(documents)
        return documents

    def validate_method(self, method):
        if method == "set_correspondent":
            return bulk_edit.set_correspondent
        elif method == "set_document_type":
            return bulk_edit.set_document_type
        elif method == "add_tag":
            return bulk_edit.add_tag
        elif method == "remove_tag":
            return bulk_edit.remove_tag
        elif method == "modify_tags":
            return bulk_edit.modify_tags
        elif method == "delete":
            return bulk_edit.delete
        else:
            raise serializers.ValidationError("Unsupported method.")

    def _validate_parameters_tags(self, parameters):
        if 'tag' in parameters:
            tag_id = parameters['tag']
            try:
                Tag.objects.get(id=tag_id)
            except Tag.DoesNotExist:
                raise serializers.ValidationError("Tag does not exist")
        else:
            raise serializers.ValidationError("tag not specified")

    def _validate_parameters_document_type(self, parameters):
        if 'document_type' in parameters:
            document_type_id = parameters['document_type']
            if document_type_id is None:
                # None is ok
                return
            try:
                DocumentType.objects.get(id=document_type_id)
            except DocumentType.DoesNotExist:
                raise serializers.ValidationError(
                    "Document type does not exist")
        else:
            raise serializers.ValidationError("document_type not specified")

    def _validate_parameters_correspondent(self, parameters):
        if 'correspondent' in parameters:
            correspondent_id = parameters['correspondent']
            if correspondent_id is None:
                return
            try:
                Correspondent.objects.get(id=correspondent_id)
            except Correspondent.DoesNotExist:
                raise serializers.ValidationError(
                    "Correspondent does not exist")
        else:
            raise serializers.ValidationError("correspondent not specified")

    def _validate_parameters_modify_tags(self, parameters):
        if "add_tags" in parameters:
            self._validate_tag_id_list(parameters['add_tags'], "add_tags")
        else:
            raise serializers.ValidationError("add_tags not specified")

        if "remove_tags" in parameters:
            self._validate_tag_id_list(parameters['remove_tags'],
                                       "remove_tags")
        else:
            raise serializers.ValidationError("remove_tags not specified")

    def validate(self, attrs):

        method = attrs['method']
        parameters = attrs['parameters']

        if method == bulk_edit.set_correspondent:
            self._validate_parameters_correspondent(parameters)
        elif method == bulk_edit.set_document_type:
            self._validate_parameters_document_type(parameters)
        elif method == bulk_edit.add_tag or method == bulk_edit.remove_tag:
            self._validate_parameters_tags(parameters)
        elif method == bulk_edit.modify_tags:
            self._validate_parameters_modify_tags(parameters)

        return attrs


class PostDocumentSerializer(serializers.Serializer):

    document = serializers.FileField(
        label="Document",
        write_only=True,
    )

    title = serializers.CharField(
        label="Title",
        write_only=True,
        required=False,
    )

    correspondent = serializers.PrimaryKeyRelatedField(
        queryset=Correspondent.objects.all(),
        label="Correspondent",
        allow_null=True,
        write_only=True,
        required=False,
    )

    document_type = serializers.PrimaryKeyRelatedField(
        queryset=DocumentType.objects.all(),
        label="Document type",
        allow_null=True,
        write_only=True,
        required=False,
    )

    tags = serializers.PrimaryKeyRelatedField(
        many=True,
        queryset=Tag.objects.all(),
        label="Tags",
        write_only=True,
        required=False,
    )

    def validate_document(self, document):
        document_data = document.file.read()
        mime_type = magic.from_buffer(document_data, mime=True)

        if not is_mime_type_supported(mime_type):
            raise serializers.ValidationError(
                _("File type %(type)s not supported") %
                {'type': mime_type}
            )

        return document.name, document_data

    def validate_correspondent(self, correspondent):
        if correspondent:
            return correspondent.id
        else:
            return None

    def validate_document_type(self, document_type):
        if document_type:
            return document_type.id
        else:
            return None

    def validate_tags(self, tags):
        if tags:
            return [tag.id for tag in tags]
        else:
            return None


class SelectionDataSerializer(serializers.Serializer):

    documents = serializers.ListField(
        required=True,
        child=serializers.IntegerField()
    )