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


class ReadingGroup(models.Model):
    """A group of users reading the same book together."""

    name = models.CharField(max_length=256, db_index=True)
    ebook = models.ForeignKey(
        "books.EBook",
        on_delete=models.CASCADE,
        related_name="reading_groups",
    )
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="created_groups",
    )
    description = models.TextField(blank=True, default="")
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "groups_reading_group"
        verbose_name = "Reading Group"
        verbose_name_plural = "Reading Groups"
        ordering = ["-created_at"]

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

    @property
    def total_sections(self) -> int:
        return self.ebook.chapters.count()


class GroupMembership(models.Model):
    class Role(models.TextChoices):
        MEMBER = "member", "Member"
        ADMIN = "admin", "Admin"

    group = models.ForeignKey(
        ReadingGroup,
        on_delete=models.CASCADE,
        related_name="memberships",
    )
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="group_memberships",
    )
    role = models.CharField(
        max_length=16,
        choices=Role.choices,
        default=Role.MEMBER,
    )
    joined_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "groups_membership"
        verbose_name = "Group Membership"
        verbose_name_plural = "Group Memberships"
        unique_together = [("group", "user")]
        ordering = ["joined_at"]

    def __str__(self) -> str:
        return f"{self.user} in {self.group.name} ({self.role})"


class MemberProgress(models.Model):
    """Per-member reading progress within a reading group."""

    membership = models.OneToOneField(
        GroupMembership,
        on_delete=models.CASCADE,
        related_name="progress",
    )
    group = models.ForeignKey(
        ReadingGroup,
        on_delete=models.CASCADE,
        related_name="member_progress",
    )
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="member_progress",
    )
    current_section = models.PositiveIntegerField(default=0)
    percentage = models.FloatField(default=0.0)
    time_spent_seconds = models.PositiveIntegerField(default=0)
    last_position = models.JSONField(blank=True, default=dict)
    is_public = models.BooleanField(default=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "groups_member_progress"
        verbose_name = "Member Progress"
        verbose_name_plural = "Member Progress"
        unique_together = [("group", "user")]
        indexes = [
            models.Index(fields=["group", "-percentage"]),
            models.Index(fields=["group", "user"]),
        ]

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

    def total_sections(self) -> int:
        return self.group.total_sections

    def update_progress(
        self,
        current_section: int,
        percentage: float | None = None,
        time_spent_delta: int = 0,
        last_position: dict | None = None,
    ) -> None:
        """Update progress with computed percentage if not provided."""
        self.current_section = current_section
        if percentage is not None:
            self.percentage = min(100.0, max(0.0, percentage))
        elif (ts := self.total_sections()) > 0:
            self.percentage = min(100.0, (current_section / ts) * 100.0)
        else:
            self.percentage = 0.0
        if time_spent_delta > 0:
            self.time_spent_seconds += time_spent_delta
        if last_position is not None:
            self.last_position = last_position
        self.save(
            update_fields=[
                "current_section",
                "percentage",
                "time_spent_seconds",
                "last_position",
                "updated_at",
            ]
        )