from __future__ import annotations

from django.db import models
from django.utils.translation import gettext_lazy as _


class ReadingStatus(models.TextChoices):
    """Enumeration of possible reading statuses for a book."""

    NOT_STARTED = "not_started", _("Not Started")
    READING = "reading", _("Reading")
    FINISHED = "finished", _("Finished")
    DNF = "dnf", _("Did Not Finish")


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

    title = models.CharField(max_length=500, verbose_name=_("Title"))
    author = models.CharField(max_length=500, verbose_name=_("Author"))
    genre = models.CharField(max_length=200, blank=True, default="", verbose_name=_("Genre"))
    description = models.TextField(blank=True, default="", verbose_name=_("Description"))
    cover_image_url = models.URLField(blank=True, default="", verbose_name=_("Cover Image URL"))
    isbn = models.CharField(max_length=20, blank=True, default="", verbose_name=_("ISBN"))
    total_pages = models.PositiveIntegerField(default=0, verbose_name=_("Total Pages"))
    current_page = models.PositiveIntegerField(default=0, verbose_name=_("Current Page"))
    reading_status = models.CharField(
        max_length=20,
        choices=ReadingStatus.choices,
        default=ReadingStatus.NOT_STARTED,
        verbose_name=_("Reading Status"),
    )
    owner = models.ForeignKey(
        "auth.User",
        on_delete=models.CASCADE,
        related_name="books",
        verbose_name=_("Owner"),
    )
    created_at = models.DateTimeField(auto_now_add=True, verbose_name=_("Created At"))
    updated_at = models.DateTimeField(auto_now=True, verbose_name=_("Updated At"))

    class Meta:
        ordering = ["-updated_at"]
        verbose_name = _("Book")
        verbose_name_plural = _("Books")
        indexes = [
            models.Index(fields=["owner", "reading_status"]),
            models.Index(fields=["owner", "title"]),
            models.Index(fields=["owner", "author"]),
        ]

    def __str__(self) -> str:
        return f"{self.title} by {self.author}"

    @property
    def reading_progress(self) -> float:
        """Calculate reading progress as a percentage (0.0 - 100.0)."""
        if self.total_pages == 0:
            return 0.0
        return round((self.current_page / self.total_pages) * 100, 1)

    def mark_as_finished(self) -> None:
        """Mark the book as finished, setting progress to 100%."""
        self.reading_status = ReadingStatus.FINISHED
        self.current_page = self.total_pages
        self.save(update_fields=["reading_status", "current_page", "updated_at"])