from django.contrib.auth import get_user_model
from django.utils import timezone
from django.utils.translation import gettext_lazy as _
from rest_framework import serializers
from drf_spectacular.utils import extend_schema_field

from apps.cms.models.post import (
    PostCategory,
    PostTag,
    Post,
    PostRevision,
    PostComment,
    PostLike,
    MediaAsset,
)
from apps.profiles.models.institution import Institution
from apps.cms.permissions import can_publish_or_moderate_post

User = get_user_model()


class PostCategorySerializer(serializers.ModelSerializer):
    posts_count = serializers.SerializerMethodField()

    class Meta:
        model = PostCategory
        fields = [
            'id',
            'name',
            'slug',
            'language',
            'description',
            'created_at',
            'posts_count',
        ]
        read_only_fields = ['id', 'slug', 'created_at', 'posts_count']

    @extend_schema_field(serializers.IntegerField)
    def get_posts_count(self, obj) -> int:
        return obj.posts.filter(status=Post.Status.PUBLISHED).count()


class PostTagSerializer(serializers.ModelSerializer):
    class Meta:
        model = PostTag
        fields = ['id', 'name', 'slug']
        read_only_fields = ['id', 'slug']


class PostAuthorMiniSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ['id', 'email', 'fullname', 'avatar']
        read_only_fields = fields


class PostInstitutionMiniSerializer(serializers.ModelSerializer):
    type_display = serializers.CharField(source='get_type_display', read_only=True)

    class Meta:
        model = Institution
        fields = ['id', 'name', 'slug', 'type', 'type_display', 'avatar', 'city', 'country']
        read_only_fields = fields


class PostAuthorDisplaySerializer(serializers.Serializer):
    type = serializers.CharField(help_text="Author type: 'user' or 'institution'")
    id = serializers.IntegerField(help_text="ID of the user or institution", allow_null=True)
    name = serializers.CharField(help_text="Name of the author or institution")
    slug = serializers.CharField(allow_null=True, required=False)
    avatar = serializers.CharField(allow_null=True, required=False)
    role_label = serializers.CharField(allow_null=True, required=False)
    submitted_by = serializers.DictField(allow_null=True, required=False)


def resolve_post_author_display(obj, request=None) -> dict:
    custom_avatar = obj.author_custom_avatar.url if getattr(obj, 'author_custom_avatar', None) else None
    if custom_avatar and request and not custom_avatar.startswith(('http://', 'https://')):
        custom_avatar = request.build_absolute_uri(custom_avatar)

    if obj.author_type == Post.AuthorType.INSTITUTION and obj.institution:
        inst = obj.institution
        avatar_url = custom_avatar or (inst.avatar.url if getattr(inst, 'avatar', None) else None)
        if avatar_url and request and not avatar_url.startswith(('http://', 'https://')):
            avatar_url = request.build_absolute_uri(avatar_url)

        user = obj.author
        submitted_by = None
        if user:
            submitted_by = {
                'id': user.id,
                'name': getattr(user, 'fullname', None) or user.get_full_name() or user.email,
            }

        return {
            'type': 'institution',
            'id': inst.id,
            'name': inst.name,
            'slug': inst.slug,
            'avatar': avatar_url,
            'role_label': obj.author_role_label,
            'submitted_by': submitted_by,
        }

    user = obj.author
    avatar_url = custom_avatar or (user.avatar.url if (user and getattr(user, 'avatar', None)) else None)
    if avatar_url and request and not avatar_url.startswith(('http://', 'https://')):
        avatar_url = request.build_absolute_uri(avatar_url)

    return {
        'type': 'user',
        'id': user.id if user else None,
        'name': (getattr(user, 'fullname', None) or user.get_full_name() or user.email) if user else '',
        'slug': getattr(user, 'username', None),
        'avatar': avatar_url,
        'role_label': obj.author_role_label,
        'submitted_by': None,
    }


class PostRevisionSerializer(serializers.ModelSerializer):
    author = PostAuthorMiniSerializer(read_only=True)
    reviewed_by = PostAuthorMiniSerializer(read_only=True)
    status_display = serializers.CharField(source='get_status_display', read_only=True)
    category_name = serializers.CharField(source='category.name', read_only=True, allow_null=True)

    class Meta:
        model = PostRevision
        fields = [
            'id',
            'post',
            'author',
            'title',
            'excerpt',
            'content',
            'tags',
            'featured_image',
            'category',
            'category_name',
            'status',
            'status_display',
            'rejection_reason',
            'reviewed_by',
            'reviewed_at',
            'created_at',
            'updated_at',
        ]
        read_only_fields = fields


class PostRevisionCreateSerializer(serializers.ModelSerializer):
    class Meta:
        model = PostRevision
        fields = [
            'title',
            'excerpt',
            'content',
            'tags',
            'featured_image',
            'category',
        ]


class PostCommentSerializer(serializers.ModelSerializer):
    user = PostAuthorMiniSerializer(read_only=True)
    status_display = serializers.CharField(source='get_status_display', read_only=True)

    class Meta:
        model = PostComment
        fields = [
            'id',
            'post',
            'user',
            'author_name',
            'author_email',
            'content',
            'status',
            'status_display',
            'created_at',
        ]
        read_only_fields = ['id', 'post', 'user', 'status', 'status_display', 'created_at']


class PostCommentCreateSerializer(serializers.Serializer):
    content = serializers.CharField(required=True)
    author_name = serializers.CharField(required=False, allow_blank=True, max_length=255)
    author_email = serializers.EmailField(required=False, allow_blank=True)


class PostListSerializer(serializers.ModelSerializer):
    post_type_display = serializers.CharField(source='get_post_type_display', read_only=True)
    author_type_display = serializers.CharField(source='get_author_type_display', read_only=True)
    author_display = serializers.SerializerMethodField()
    category_name = serializers.CharField(source='category.name', read_only=True, allow_null=True)
    author = PostAuthorMiniSerializer(read_only=True)
    institution = PostInstitutionMiniSerializer(read_only=True)
    comments_count = serializers.SerializerMethodField()
    is_liked = serializers.SerializerMethodField()
    has_pending_revision = serializers.BooleanField(read_only=True)

    class Meta:
        model = Post
        fields = [
            'id',
            'title',
            'slug',
            'post_type',
            'post_type_display',
            'author_type',
            'author_type_display',
            'author_display',
            'category',
            'category_name',
            'language',
            'status',
            'rejection_reason',
            'author',
            'institution',
            'author_role_label',
            'author_custom_avatar',
            'featured_image',
            'excerpt',
            'tags',
            'reading_time_minutes',
            'views_count',
            'likes_count',
            'comments_count',
            'is_featured',
            'publish_date',
            'is_liked',
            'has_pending_revision',
            'reviewed_at',
            'created_at',
        ]
        read_only_fields = fields

    @extend_schema_field(PostAuthorDisplaySerializer)
    def get_author_display(self, obj) -> dict:
        return resolve_post_author_display(obj, self.context.get('request'))

    @extend_schema_field(serializers.IntegerField)
    def get_comments_count(self, obj) -> int:
        return obj.comments.filter(status=PostComment.Status.APPROVED).count()

    @extend_schema_field(serializers.BooleanField)
    def get_is_liked(self, obj) -> bool:
        request = self.context.get('request')
        if not request or not request.user.is_authenticated:
            return False
        return obj.is_liked_by(request.user)


class PostDetailSerializer(serializers.ModelSerializer):
    post_type_display = serializers.CharField(source='get_post_type_display', read_only=True)
    author_type_display = serializers.CharField(source='get_author_type_display', read_only=True)
    author_display = serializers.SerializerMethodField()
    category = PostCategorySerializer(read_only=True)
    author = PostAuthorMiniSerializer(read_only=True)
    institution = PostInstitutionMiniSerializer(read_only=True)
    reviewed_by = PostAuthorMiniSerializer(read_only=True)
    comments = serializers.SerializerMethodField()
    comments_count = serializers.SerializerMethodField()
    is_liked = serializers.SerializerMethodField()
    has_pending_revision = serializers.BooleanField(read_only=True)
    pending_revision = serializers.SerializerMethodField()

    class Meta:
        model = Post
        fields = [
            'id',
            'title',
            'slug',
            'post_type',
            'post_type_display',
            'author_type',
            'author_type_display',
            'author_display',
            'category',
            'language',
            'status',
            'rejection_reason',
            'author',
            'institution',
            'author_role_label',
            'author_custom_avatar',
            'featured_image',
            'excerpt',
            'content',
            'tags',
            'reading_time_minutes',
            'views_count',
            'likes_count',
            'comments_count',
            'is_featured',
            'publish_date',
            'is_liked',
            'has_pending_revision',
            'pending_revision',
            'comments',
            'reviewed_by',
            'reviewed_at',
            'created_at',
            'updated_at',
        ]
        read_only_fields = [
            'id',
            'slug',
            'reading_time_minutes',
            'views_count',
            'likes_count',
            'comments_count',
            'is_liked',
            'has_pending_revision',
            'pending_revision',
            'comments',
            'reviewed_by',
            'reviewed_at',
            'created_at',
            'updated_at',
        ]

    @extend_schema_field(PostAuthorDisplaySerializer)
    def get_author_display(self, obj) -> dict:
        return resolve_post_author_display(obj, self.context.get('request'))

    @extend_schema_field(PostRevisionSerializer)
    def get_pending_revision(self, obj):
        request = self.context.get('request')
        if not request or not request.user.is_authenticated:
            return None
        user = request.user
        is_author = (obj.author_id == user.id)
        is_editor = can_publish_or_moderate_post(user, obj.institution)
        if is_author or is_editor:
            pending = obj.get_pending_revision()
            if pending:
                return PostRevisionSerializer(pending, context=self.context).data
        return None

    @extend_schema_field(PostCommentSerializer(many=True))
    def get_comments(self, obj):
        approved_comments = obj.comments.filter(status=PostComment.Status.APPROVED).order_by('-created_at')
        return PostCommentSerializer(approved_comments, many=True).data

    @extend_schema_field(serializers.IntegerField)
    def get_comments_count(self, obj) -> int:
        return obj.comments.filter(status=PostComment.Status.APPROVED).count()

    @extend_schema_field(serializers.BooleanField)
    def get_is_liked(self, obj) -> bool:
        request = self.context.get('request')
        if not request or not request.user.is_authenticated:
            return False
        return obj.is_liked_by(request.user)


class PostCreateUpdateSerializer(serializers.ModelSerializer):
    class Meta:
        model = Post
        fields = [
            'title',
            'post_type',
            'author_type',
            'category',
            'language',
            'status',
            'rejection_reason',
            'institution',
            'author_role_label',
            'author_custom_avatar',
            'featured_image',
            'excerpt',
            'content',
            'tags',
            'is_featured',
            'publish_date',
        ]

    def validate(self, attrs):
        request = self.context.get('request')
        user = request.user if request else None
        instance = getattr(self, 'instance', None)

        target_author_type = attrs.get('author_type') or (instance.author_type if instance else Post.AuthorType.USER)
        target_institution = attrs.get('institution') or (instance.institution if instance else None)

        if target_author_type == Post.AuthorType.INSTITUTION:
            if not target_institution:
                raise serializers.ValidationError({
                    "institution": _("An institution is required when authoring on behalf of an institution.")
                })

            if user and not (user.is_superuser or getattr(user, 'is_super_admin', False)):
                is_inst_editor = target_institution.is_editor(user)
                has_reg_perm = False
                if getattr(user, 'is_regional_admin', False) and hasattr(user, 'can_manage_region'):
                    has_reg_perm = user.can_manage_region(target_institution.region)

                if not (is_inst_editor or has_reg_perm):
                    raise serializers.ValidationError({
                        "institution": _("You are not authorized to author content on behalf of this institution.")
                    })

        target_status = attrs.get('status')

        if target_status:
            has_mod_cap = can_publish_or_moderate_post(user, target_institution)

            if target_status == Post.Status.PUBLISHED:
                if not has_mod_cap:
                    raise serializers.ValidationError({
                        "status": _("You do not have direct publishing capability for this institution. Please save as draft or submit for review.")
                    })

            elif target_status == Post.Status.REJECTED:
                if not has_mod_cap:
                    raise serializers.ValidationError({
                        "status": _("You do not have authority to reject posts for this institution.")
                    })
                reason = attrs.get('rejection_reason', '') or (instance.rejection_reason if instance else '')
                if not reason or not str(reason).strip():
                    raise serializers.ValidationError({
                        "rejection_reason": _("A rejection reason is required when rejecting a post.")
                    })

            elif target_status == Post.Status.ARCHIVED:
                if not has_mod_cap:
                    raise serializers.ValidationError({
                        "status": _("You do not have authority to archive posts for this institution.")
                    })

            elif target_status in [Post.Status.PENDING_REVIEW, Post.Status.DRAFT]:
                # If resubmitting from rejected to draft/pending_review, clear old rejection reason
                if instance and instance.status == Post.Status.REJECTED and 'rejection_reason' not in attrs:
                    attrs['rejection_reason'] = ''
        else:
            if not instance:
                attrs['status'] = Post.Status.DRAFT

        return attrs

    def create(self, validated_data):
        request = self.context.get('request')
        if request and request.user.is_authenticated:
            validated_data['author'] = request.user
        target_status = validated_data.get('status')
        if target_status in [Post.Status.PUBLISHED, Post.Status.REJECTED]:
            validated_data['reviewed_by'] = request.user
            validated_data['reviewed_at'] = timezone.now()
        return super().create(validated_data)

    def update(self, instance, validated_data):
        request = self.context.get('request')
        target_status = validated_data.get('status')
        if target_status and target_status != instance.status:
            if target_status in [Post.Status.PUBLISHED, Post.Status.REJECTED]:
                if request and request.user.is_authenticated:
                    validated_data['reviewed_by'] = request.user
                    validated_data['reviewed_at'] = timezone.now()
        return super().update(instance, validated_data)


class PostLikeResponseSerializer(serializers.Serializer):
    is_liked = serializers.BooleanField()
    likes_count = serializers.IntegerField()
    message = serializers.CharField()


class MediaAssetSerializer(serializers.ModelSerializer):
    media_type_display = serializers.CharField(source='get_media_type_display', read_only=True)
    uploaded_by_email = serializers.EmailField(source='uploaded_by.email', read_only=True, allow_null=True)

    class Meta:
        model = MediaAsset
        fields = [
            'id',
            'file',
            'title',
            'media_type',
            'media_type_display',
            'file_size',
            'dimensions',
            'uploaded_by_email',
            'created_at',
        ]
        read_only_fields = ['id', 'media_type_display', 'file_size', 'uploaded_by_email', 'created_at']

    def create(self, validated_data):
        request = self.context.get('request')
        if request and request.user.is_authenticated:
            validated_data['uploaded_by'] = request.user
        return super().create(validated_data)