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

from apps.books.models import EBook


class ReadingGroup(models.Model):
    """A reading group with an admin and members."""

    name = models.CharField(max_length=256, db_index=True)
    description = models.TextField(blank=True, default="")
    admin = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="administered_groups",
    )
    members = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        through="ReadingGroupMembership",
        related_name="reading_groups",
    )
    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


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

    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    group = models.ForeignKey(ReadingGroup, on_delete=models.CASCADE, related_name="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"
        unique_together = [("user", "group")]
        verbose_name = "Reading Group Membership"
        verbose_name_plural = "Reading Group Memberships"

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


class GroupBook(models.Model):
    """Links an uploaded EBook to a reading group."""

    class Status(models.TextChoices):
        ACTIVE = "active", "Active"
        REPLACED = "replaced", "Replaced"

    group = models.ForeignKey(
        ReadingGroup, on_delete=models.CASCADE, related_name="group_books"
    )
    ebook = models.ForeignKey(
        EBook, on_delete=models.CASCADE, related_name="group_books"
    )
    uploaded_by = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="uploaded_group_books"
    )
    title = models.CharField(max_length=512, db_index=True)
    status = models.CharField(
        max_length=16, choices=Status.choices, default=Status.ACTIVE, db_index=True
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "groups_group_book"
        verbose_name = "Group Book"
        verbose_name_plural = "Group Books"
        ordering = ["-created_at"]
        indexes = [models.Index(fields=["group", "status"])]

    def __str__(self) -> str:
        return f"{self.group.name} — {self.title}"


class Section(models.Model):
    """A section/chunk of a GroupBook for group reading."""

    group_book = models.ForeignKey(
        GroupBook, on_delete=models.CASCADE, related_name="sections"
    )
    title = models.CharField(max_length=512)
    order = models.PositiveIntegerField(db_index=True)
    start_chapter_index = models.PositiveIntegerField(default=0)
    end_chapter_index = models.PositiveIntegerField(default=0)
    estimated_reading_minutes = models.PositiveIntegerField(default=0)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "groups_section"
        verbose_name = "Section"
        verbose_name_plural = "Sections"
        ordering = ["order"]
        unique_together = [("group_book", "order")]
        indexes = [models.Index(fields=["group_book", "order"])]

    def __str__(self) -> str:
        return f"{self.group_book.title} — Section {self.order}: {self.title}"


class ReadingSchedule(models.Model):
    """Reading schedule mapping sections to weekly meetings."""

    group_book = models.ForeignKey(
        GroupBook, on_delete=models.CASCADE, related_name="schedules"
    )
    meeting_number = models.PositiveIntegerField()
    week_date = models.DateField()
    section_ids = models.JSONField(default=list, help_text="Ordered list of Section IDs for this meeting")
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "groups_reading_schedule"
        verbose_name = "Reading Schedule"
        verbose_name_plural = "Reading Schedules"
        ordering = ["meeting_number"]
        unique_together = [("group_book", "meeting_number")]
        indexes = [models.Index(fields=["group_book", "meeting_number"])]

    def __str__(self) -> str:
        return f"{self.group_book.title} — Meeting {self.meeting_number}"


class MemberProgress(models.Model):
    """Tracks a member's progress through sections of a group book."""

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="group_progress"
    )
    group_book = models.ForeignKey(
        GroupBook, on_delete=models.CASCADE, related_name="member_progress"
    )
    current_section = models.ForeignKey(
        Section, on_delete=models.SET_NULL, null=True, blank=True, related_name="current_readers"
    )
    completed_sections = models.JSONField(
        default=list, help_text="Ordered list of completed Section IDs"
    )
    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 = [("user", "group_book")]

    def __str__(self) -> str:
        return f"{self.user} — {self.group_book.title}"