from django.db import models


class Book(models.Model):
    """Represents a book in the user's library."""

    title = models.CharField(max_length=512)
    author = models.CharField(max_length=256, blank=True, default="")
    total_pages = models.PositiveIntegerField(default=0)
    cover_image = models.URLField(blank=True, default="")
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "books_book"
        verbose_name = "Book"
        verbose_name_plural = "Books"
        ordering = ["title"]

    def __str__(self) -> str:
        return self.title


class Chapter(models.Model):
    """A chapter within a book, containing the text/markdown content."""

    book = models.ForeignKey(
        Book,
        on_delete=models.CASCADE,
        related_name="chapters",
        db_index=True,
    )
    title = models.CharField(max_length=512)
    number = models.PositiveIntegerField()
    content = models.TextField(blank=True, default="")
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "books_chapter"
        verbose_name = "Chapter"
        verbose_name_plural = "Chapters"
        ordering = ["book", "number"]
        constraints = [
            models.UniqueConstraint(
                fields=["book", "number"],
                name="uq_book_chapter_number",
            )
        ]

    def __str__(self) -> str:
        return f"{self.book.title} — Ch. {self.number}: {self.title}"


class ReadingProgress(models.Model):
    """Tracks a user's reading progress within a book."""

    user = models.ForeignKey(
        "users.User",
        on_delete=models.CASCADE,
        related_name="reading_progress",
        db_index=True,
    )
    book = models.ForeignKey(
        Book,
        on_delete=models.CASCADE,
        related_name="reading_progress",
        db_index=True,
    )
    current_chapter = models.PositiveIntegerField(default=1)
    current_position = models.PositiveIntegerField(default=0)
    percentage = models.FloatField(default=0.0)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "books_reading_progress"
        verbose_name = "Reading Progress"
        verbose_name_plural = "Reading Progress"
        ordering = ["-updated_at"]
        constraints = [
            models.UniqueConstraint(
                fields=["user", "book"],
                name="uq_reading_progress_user_book",
            )
        ]

    def __str__(self) -> str:
        return f"{self.user} — {self.book.title} ({self.percentage:.0f}%)"