from django.db import models
from django.contrib.auth.models import User


class EBook(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='ebooks')
    meta_ct = models.TextField()          # base64 AES-GCM ciphertext of {title, author, filename}
    meta_iv = models.CharField(max_length=32)  # hex IV for metadata
    data_ct = models.TextField()          # base64 AES-GCM ciphertext of raw EPUB bytes
    data_iv = models.CharField(max_length=32)  # hex IV for EPUB data
    uploaded_at = models.DateTimeField(auto_now_add=True)
    is_read = models.BooleanField(default=False)
    # The cover, end-to-end encrypted like the rest (docs/library.md): a client that has
    # the file extracts it, encrypts it with the user's key and sends it once.
    cover_ct = models.TextField(blank=True, default='')
    cover_iv = models.CharField(max_length=32, blank=True, default='')

    class Meta:
        ordering = ['uploaded_at']
        # The list reads these from indexes, never from the row: the file (data_ct) stands
        # before them in it, and SQLite walks through all of a file to reach a column after it
        # — 37 s for a library of 400 books (docs/database.md). See book_rows().
        indexes = [
            models.Index(fields=['user', 'uploaded_at', 'is_read'], name='ebook_list_idx'),
            models.Index(fields=['user', 'cover_iv'], name='ebook_cover_idx'),
        ]

    def __str__(self):
        return f"EBook #{self.pk} (user={self.user_id})"


def book_rows(user):
    """Every book of the user as {id, meta_ct, meta_iv, uploaded_at (ISO), is_read, has_cover},
    oldest first — read without passing a book's file: meta_ct and meta_iv stand before it in
    the row, the rest comes from the covering indexes ebook_list_idx and ebook_cover_idx."""
    books = {b['id']: b for b in EBook.objects.filter(user=user).order_by().values('id', 'meta_ct', 'meta_iv')}
    for book_id, at, read in EBook.objects.filter(user=user).order_by().values_list('id', 'uploaded_at', 'is_read'):
        if book_id in books:
            books[book_id].update(uploaded_at=at, is_read=read)
    covered = set(EBook.objects.filter(user=user).exclude(cover_iv='').order_by().values_list('id', flat=True))
    out = sorted((b for b in books.values() if 'uploaded_at' in b), key=lambda b: (b['uploaded_at'], b['id']))
    for b in out:
        b['uploaded_at'] = b['uploaded_at'].isoformat()
        b['has_cover'] = b['id'] in covered
    return out


class LibraryPrefs(models.Model):
    """The library's own settings, encrypted with the user's key (the folder order:
    folder names are private, docs/library.md). One blob, replaced as a whole."""
    user = models.OneToOneField(User, on_delete=models.CASCADE, related_name='library_prefs')
    prefs_ct = models.TextField(blank=True, default='')
    prefs_iv = models.CharField(max_length=32, blank=True, default='')
    updated_at = models.DateTimeField(auto_now=True)


class EBookProgress(models.Model):
    """Where to continue a book: the place it was last read, on any device
    (docs/progress-sync.md), plus the furthest place ever reached."""
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='ebook_progress')
    book = models.ForeignKey(EBook, on_delete=models.CASCADE, related_name='progress')
    scroll_fraction = models.FloatField(default=0.0)
    position_anchor = models.CharField(max_length=30, blank=True, default='')
    # When the reader was at that place (ms since epoch, server clock); null before 2026-10-12.
    read_at = models.BigIntegerField(null=True, blank=True)
    device = models.CharField(max_length=40, blank=True, default='')
    furthest_fraction = models.FloatField(default=0.0)
    furthest_anchor = models.CharField(max_length=30, blank=True, default='')
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        unique_together = ('user', 'book')

    def __str__(self):
        return f"Progress book={self.book_id} user={self.user_id} {self.scroll_fraction:.2f}"


class EBookHighlights(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='ebook_highlights')
    book = models.ForeignKey(EBook, on_delete=models.CASCADE, related_name='highlights')
    ct   = models.TextField()                # base64 AES-GCM ciphertext of JSON array
    iv   = models.CharField(max_length=32)   # hex IV
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        unique_together = ('user', 'book')

    def __str__(self):
        return f"Highlights book={self.book_id} user={self.user_id}"


class EBookBookmarks(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='ebook_bookmarks')
    book = models.ForeignKey(EBook, on_delete=models.CASCADE, related_name='bookmarks')
    ct   = models.TextField()
    iv   = models.CharField(max_length=32)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        unique_together = ('user', 'book')

    def __str__(self):
        return f"Bookmarks book={self.book_id} user={self.user_id}"