import os
from django.db import models
from django.conf import settings


CATEGORY_CHOICES = [
    ('frontend', '前端'),
    ('backend', '后端'),
    ('tools', '工具'),
    ('devops', '运维'),
    ('security', '安全'),
    ('basic', '基础'),
]

LEVEL_CHOICES = [
    ('beginner', '入门'),
    ('advanced', '进阶'),
]

STATUS_CHOICES = [
    ('published', '已发布'),
    ('draft', '草稿'),
]


class Course(models.Model):
    title = models.CharField(max_length=200, verbose_name='标题')
    description = models.TextField(blank=True, default='', verbose_name='描述')
    category = models.CharField(max_length=20, choices=CATEGORY_CHOICES, default='frontend')
    level = models.CharField(max_length=10, choices=LEVEL_CHOICES, default='beginner')
    cover_image = models.ImageField(upload_to='learn/covers/%Y/%m/', blank=True, null=True)
    color = models.CharField(max_length=20, default='#667eea', verbose_name='主题色')
    icon_name = models.CharField(max_length=50, default='CodeOutlined', verbose_name='图标名称')
    author = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='courses',
        verbose_name='作者'
    )
    status = models.CharField(max_length=20, choices=STATUS_CHOICES, default='draft')
    sort_order = models.IntegerField(default=0)
    is_hot = models.BooleanField(default=False)
    is_new = models.BooleanField(default=False)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ['-sort_order', '-created_at']
        verbose_name = '课程'
        verbose_name_plural = '课程'

    def __str__(self):
        return self.title


class Chapter(models.Model):
    VIDEO_SOURCE_CHOICES = [
        ('bilibili', 'B站视频'),
        ('local', '本地视频'),
    ]

    course = models.ForeignKey(Course, on_delete=models.CASCADE, related_name='chapters', verbose_name='课程')
    title = models.CharField(max_length=200)
    sort_order = models.IntegerField(default=0)
    duration = models.CharField(max_length=50, blank=True, default='', verbose_name='时长')
    is_free = models.BooleanField(default=True)
    video_url = models.URLField(max_length=500, blank=True, default='', verbose_name='视频链接')
    video_source = models.CharField(max_length=20, choices=VIDEO_SOURCE_CHOICES, default='bilibili', verbose_name='视频来源')
    video_local = models.FileField(upload_to='learn/videos/%Y/%m/', blank=True, null=True, verbose_name='本地视频文件')
    video_poster = models.ImageField(upload_to='learn/video_posters/%Y/%m/', blank=True, null=True, verbose_name='视频封面')
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ['sort_order']
        verbose_name = '章节'
        verbose_name_plural = '章节'

    def __str__(self):
        return self.title


class ChapterContent(models.Model):
    chapter = models.OneToOneField(Chapter, on_delete=models.CASCADE, related_name='content', verbose_name='章节')
    content_md = models.TextField(blank=True, default='', verbose_name='Markdown内容')
    content_html = models.TextField(blank=True, default='', verbose_name='预渲染HTML')
    md_file_path = models.CharField(max_length=500, blank=True, default='', verbose_name='MD文件路径')
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        verbose_name = '章节内容'
        verbose_name_plural = '章节内容'

    def __str__(self):
        return f'{self.chapter.title} - 内容'

    def save(self, *args, **kwargs):
        super().save(*args, **kwargs)
        if self.content_md:
            try:
                import markdown
                self.content_html = markdown.markdown(
                    self.content_md,
                    extensions=['extra', 'codehilite', 'toc', 'tables']
                )
            except ImportError:
                self.content_html = self.content_md.replace('\n', '<br>')
            ChapterContent.objects.filter(pk=self.pk).update(content_html=self.content_html)
        self.export_md_file()

    def export_md_file(self):
        if not self.content_md:
            return
        course_id = self.chapter.course_id
        chapter_id = self.chapter_id
        file_path = os.path.join(
            settings.MEDIA_ROOT,
            'learn', 'courses', str(course_id), 'chapters', f'{chapter_id}.md'
        )
        os.makedirs(os.path.dirname(file_path), exist_ok=True)
        with open(file_path, 'w', encoding='utf-8') as f:
            f.write(self.content_md)
        relative_path = os.path.relpath(file_path, settings.MEDIA_ROOT).replace('\\', '/')
        ChapterContent.objects.filter(pk=self.pk).update(md_file_path=relative_path)


class ChapterRead(models.Model):
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='chapter_reads',
        verbose_name='用户'
    )
    chapter = models.ForeignKey(
        Chapter,
        on_delete=models.CASCADE,
        related_name='chapter_reads',
        verbose_name='章节'
    )
    course = models.ForeignKey(
        Course,
        on_delete=models.CASCADE,
        related_name='chapter_reads',
        verbose_name='课程'
    )
    completed = models.BooleanField(default=True, verbose_name='是否已完成')
    completed_at = models.DateTimeField(auto_now_add=True, verbose_name='完成时间')
    updated_at = models.DateTimeField(auto_now=True, verbose_name='更新时间')

    class Meta:
        verbose_name = '章节学习记录'
        verbose_name_plural = '章节学习记录'
        unique_together = ['user', 'chapter']
        ordering = ['-completed_at']

    def __str__(self):
        return f'{self.user} read {self.chapter}'


class CourseFavorite(models.Model):
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='course_favorites',
        verbose_name='用户'
    )
    course = models.ForeignKey(
        Course,
        on_delete=models.CASCADE,
        related_name='course_favorites',
        verbose_name='课程'
    )
    created_at = models.DateTimeField(
        auto_now_add=True,
        verbose_name='创建时间'
    )

    class Meta:
        verbose_name = '课程收藏'
        verbose_name_plural = '课程收藏'
        unique_together = ['user', 'course']
        ordering = ['-created_at']

    def __str__(self):
        return f'{self.user} favorites {self.course}'


class CourseMaterial(models.Model):
    FILE_TYPE_CHOICES = [
        ('pdf', 'PDF'),
        ('code', '代码'),
        ('doc', '文档'),
        ('video', '视频'),
        ('dataset', '数据集'),
        ('zip', '压缩包'),
        ('other', '其他'),
    ]

    chapter = models.ForeignKey(
        Chapter,
        on_delete=models.CASCADE,
        related_name='materials',
        verbose_name='章节'
    )
    title = models.CharField(max_length=200, verbose_name='资料名称')
    file = models.FileField(upload_to='learn/materials/%Y/%m/', verbose_name='文件')
    file_type = models.CharField(max_length=20, choices=FILE_TYPE_CHOICES, default='other', verbose_name='文件类型')
    file_size = models.PositiveIntegerField(default=0, verbose_name='文件大小（字节）')
    download_count = models.PositiveIntegerField(default=0, verbose_name='下载次数')
    sort_order = models.IntegerField(default=0, verbose_name='排序')
    created_at = models.DateTimeField(auto_now_add=True, verbose_name='创建时间')

    class Meta:
        ordering = ['sort_order']
        verbose_name = '课程资料'
        verbose_name_plural = '课程资料'

    def __str__(self):
        return self.title