from __future__ import annotations

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


class FrequencyChoice(models.TextChoices):
    DAILY = "daily", "Daily"
    WEEKLY = "weekly", "Weekly"


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


class NotificationStatus(models.TextChoices):
    PENDING = "pending", "Pending"
    SENT = "sent", "Sent"
    DISMISSED = "dismissed", "Dismissed"


class ReadingGroup(models.Model):
    """A group of users reading a book together with scheduled meetings."""

    name = models.CharField(max_length=256, db_index=True)
    description = models.TextField(blank=True, default="")
    book = models.ForeignKey(
        "books.Book",
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="reading_groups",
    )
    ebook = models.ForeignKey(
        "books.EBook",
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="reading_groups",
    )
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="created_groups",
    )
    created_at = models.DateTimeField(auto_now_add=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 GroupMembership(models.Model):
    """User membership in a reading group."""

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="group_memberships",
    )
    group = models.ForeignKey(
        ReadingGroup,
        on_delete=models.CASCADE,
        related_name="memberships",
    )
    role = models.CharField(
        max_length=16,
        choices=MembershipRole.choices,
        default=MembershipRole.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 = [("user", "group")]
        indexes = [models.Index(fields=["user", "group"])]

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


class GroupMeeting(models.Model):
    """A scheduled meeting for a reading group with a target section."""

    group = models.ForeignKey(
        ReadingGroup,
        on_delete=models.CASCADE,
        related_name="meetings",
    )
    title = models.CharField(max_length=512, blank=True, default="")
    scheduled_at = models.DateTimeField(db_index=True)
    target_section = models.PositiveIntegerField(
        default=0,
        help_text="Target chapter/section index to reach by this meeting",
    )
    target_section_label = models.CharField(
        max_length=512,
        blank=True,
        default="",
        help_text="Human-readable label for the target section (e.g. 'Section 3')",
    )
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "groups_meeting"
        verbose_name = "Group Meeting"
        verbose_name_plural = "Group Meetings"
        ordering = ["scheduled_at"]

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


class NotificationPreference(models.Model):
    """Per-user notification settings for reading pace alerts."""

    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="notification_preference",
        primary_key=True,
    )
    pace_notifications_enabled = models.BooleanField(default=True)
    reminder_enabled = models.BooleanField(default=True)
    frequency = models.CharField(
        max_length=16,
        choices=FrequencyChoice.choices,
        default=FrequencyChoice.DAILY,
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "groups_notification_preference"
        verbose_name = "Notification Preference"
        verbose_name_plural = "Notification Preferences"

    def __str__(self) -> str:
        return f"{self.user} — pace={'on' if self.pace_notifications_enabled else 'off'}, freq={self.frequency}"


class PaceNotification(models.Model):
    """Tracks reading pace notifications sent to users to avoid duplicates."""

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="pace_notifications",
    )
    meeting = models.ForeignKey(
        GroupMeeting,
        on_delete=models.CASCADE,
        related_name="pace_notifications",
    )
    ebook = models.ForeignKey(
        "books.EBook",
        on_delete=models.CASCADE,
        related_name="pace_notifications",
        null=True,
        blank=True,
    )
    status = models.CharField(
        max_length=16,
        choices=NotificationStatus.choices,
        default=NotificationStatus.PENDING,
    )
    current_section = models.PositiveIntegerField(default=0)
    target_section = models.PositiveIntegerField(default=0)
    ahead_behind_delta = models.IntegerField(default=0)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "groups_pace_notification"
        verbose_name = "Pace Notification"
        verbose_name_plural = "Pace Notifications"
        ordering = ["-created_at"]
        indexes = [
            models.Index(fields=["user", "meeting", "ebook"]),
        ]

    def __str__(self) -> str:
        return f"{self.user} — meeting {self.meeting_id}: {self.get_status_display()}"