from adrf.serializers import (
    ModelSerializer, SerializerMethodField,
)
from asgiref.sync import sync_to_async

from .models import Course, Chapter, ChapterContent, CourseMaterial


def _author_display(obj):
    """同步取作者展示名（跑在 sync_to_async 线程里，避免 ASGI 下 SynchronousOnlyOperation）。"""
    try:
        author = obj.author
    except Exception:
        return ''
    if author is None:
        return ''
    try:
        full = author.get_full_name()
    except Exception:
        full = ''
    try:
        username = author.username
    except Exception:
        username = ''
    return full or username or ''


def parse_duration_minutes(raw):
    """把章节 duration 字符串解析为分钟数；解析不出返回 None。

    存量格式为中文字符串（如 '30分钟'），纯数字视为分钟。
    total_minutes 只对可解析章节求和，不可解析章节不计入（不伪造）。
    """
    import re
    if raw is None:
        return None
    s = str(raw).strip()
    if not s:
        return None
    m = re.search(r'(\d+(?:\.\d+)?)', s)
    if not m:
        return None
    try:
        return int(float(m.group(1)))
    except (ValueError, OverflowError):
        return None


def _course_total_minutes(obj):
    """同步聚合课程总分钟数（跑在 sync_to_async 线程里）。"""
    try:
        durations = list(obj.chapters.values_list('duration', flat=True))
    except Exception:
        return None
    total = 0
    any_parsed = False
    for d in durations:
        m = parse_duration_minutes(d)
        if m is not None:
            total += m
            any_parsed = True
    return total if any_parsed else None


class ChapterSerializer(ModelSerializer):
    video_poster_url = SerializerMethodField()
    video_local_url = SerializerMethodField()

    class Meta:
        model = Chapter
        fields = ['id', 'title', 'sort_order', 'duration', 'is_free', 'video_url', 'video_source', 'video_local_url', 'video_poster_url', 'created_at', 'updated_at']

    async def get_video_poster_url(self, obj):
        if obj.video_poster:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.video_poster.url)
            return obj.video_poster.url
        return ''

    async def get_video_local_url(self, obj):
        if obj.video_local:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.video_local.url)
            return obj.video_local.url
        return ''


class ChapterContentSerializer(ModelSerializer):
    class Meta:
        model = ChapterContent
        fields = ['id', 'chapter', 'content_md', 'content_html', 'md_file_path', 'updated_at']


class MaterialSerializer(ModelSerializer):
    file_url = SerializerMethodField()
    file_size_display = SerializerMethodField()
    file_type_display = SerializerMethodField()

    class Meta:
        model = CourseMaterial
        fields = ['id', 'title', 'file_url', 'file_type', 'file_type_display', 'file_size', 'file_size_display', 'download_count', 'sort_order', 'created_at']

    async def get_file_url(self, obj):
        if obj.file:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.file.url)
            return obj.file.url
        return ''

    async def get_file_size_display(self, obj):
        size = obj.file_size
        if size < 1024:
            return f'{size} B'
        elif size < 1024 * 1024:
            return f'{size / 1024:.1f} KB'
        else:
            return f'{size / (1024 * 1024):.1f} MB'

    async def get_file_type_display(self, obj):
        type_map = {
            'pdf': 'PDF',
            'code': '代码',
            'doc': '文档',
            'video': '视频',
            'dataset': '数据集',
            'zip': '压缩包',
            'other': '其他',
        }
        return type_map.get(obj.file_type, '其他')


class ChapterSerializer(ModelSerializer):
    video_poster_url = SerializerMethodField()

    class Meta:
        model = Chapter
        fields = ['id', 'title', 'sort_order', 'duration', 'is_free', 'video_url', 'video_poster_url', 'created_at', 'updated_at']

    async def get_video_poster_url(self, obj):
        if obj.video_poster:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.video_poster.url)
            return obj.video_poster.url
        return ''


class ChapterContentSerializer(ModelSerializer):
    class Meta:
        model = ChapterContent
        fields = ['id', 'chapter', 'content_md', 'content_html', 'md_file_path', 'updated_at']


class CourseListSerializer(ModelSerializer):
    author_name = SerializerMethodField()
    chapters_count = SerializerMethodField()
    students_count = SerializerMethodField()
    total_minutes = SerializerMethodField()
    cover_image_url = SerializerMethodField()

    class Meta:
        model = Course
        fields = [
            'id', 'title', 'description', 'category', 'level',
            'cover_image_url', 'color', 'icon_name', 'author_name',
            'chapters_count', 'students_count', 'total_minutes', 'status',
            'sort_order', 'is_hot', 'is_new', 'created_at', 'updated_at',
        ]

    async def get_chapters_count(self, obj):
        return await obj.chapters.acount()

    async def get_students_count(self, obj):
        # 从章节阅读记录去重统计真实在学人数
        from user.models import FUser
        return await FUser.objects.filter(
            chapter_reads__course=obj
        ).distinct().acount()

    async def get_total_minutes(self, obj):
        # 可解析章节 duration 求和；全不可解析返回 None（前端不显示，不伪造）
        return await sync_to_async(_course_total_minutes)(obj)

    async def get_cover_image_url(self, obj):
        if obj.cover_image:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.cover_image.url)
            return obj.cover_image.url
        return ''

    async def get_author_name(self, obj):
        return await sync_to_async(_author_display)(obj)


class CourseDetailSerializer(ModelSerializer):
    author_name = SerializerMethodField()
    chapters = ChapterSerializer(many=True, read_only=True)
    chapters_count = SerializerMethodField()
    students_count = SerializerMethodField()
    total_minutes = SerializerMethodField()
    cover_image_url = SerializerMethodField()

    class Meta:
        model = Course
        fields = [
            'id', 'title', 'description', 'category', 'level',
            'cover_image_url', 'color', 'icon_name', 'author_name',
            'chapters', 'chapters_count', 'students_count', 'total_minutes', 'status',
            'sort_order', 'is_hot', 'is_new', 'created_at', 'updated_at',
        ]

    async def get_chapters_count(self, obj):
        return await obj.chapters.acount()

    async def get_students_count(self, obj):
        # 从章节阅读记录去重统计真实在学人数
        from user.models import FUser
        return await FUser.objects.filter(
            chapter_reads__course=obj
        ).distinct().acount()

    async def get_total_minutes(self, obj):
        return await sync_to_async(_course_total_minutes)(obj)

    async def get_cover_image_url(self, obj):
        if obj.cover_image:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.cover_image.url)
            return obj.cover_image.url
        return ''

    async def get_author_name(self, obj):
        return await sync_to_async(_author_display)(obj)


class CourseCreateUpdateSerializer(ModelSerializer):
    class Meta:
        model = Course
        fields = ['title', 'description', 'category', 'level', 'cover_image', 'color', 'icon_name', 'status', 'sort_order', 'is_hot', 'is_new']

    async def acreate(self, validated_data):
        validated_data['author'] = self.context['request'].user
        return await super().acreate(validated_data)


class CourseManageSerializer(ModelSerializer):
    author_name = SerializerMethodField()
    chapters_count = SerializerMethodField()

    class Meta:
        model = Course
        fields = [
            'id', 'title', 'category', 'level', 'status',
            'sort_order', 'is_hot', 'is_new', 'chapters_count',
            'author_name', 'created_at', 'updated_at',
        ]

    async def get_chapters_count(self, obj):
        return await obj.chapters.acount()

    async def get_author_name(self, obj):
        if obj.author:
            return obj.author.get_full_name() or obj.author.username
        return ''