"""Compress existing raw mouth crop blocks without changing their public bytes."""

import hashlib
import zlib

from django.core.management.base import BaseCommand, CommandError
from django.db import transaction
from django.db.models.deletion import ProtectedError

from clips import blobs
from clips.models import Blob, Block


class Command(BaseCommand):
    help = "Compress existing source/crops blobs and remove unreferenced raw copies"

    def handle(self, *args, **options):
        converted = 0
        before = after = 0
        for block in Block.objects.filter(role="source/crops").select_related("data"):
            old = block.data
            if old.media_type == blobs.CROP_MEDIA_TYPE:
                continue
            old_digest = old.digest
            with open(blobs.path_for(old_digest), "rb") as source:
                digest, size = blobs.write_compressed_stream(
                    iter(lambda: source.read(blobs.CHUNK), b"")
                )
            check = hashlib.sha256()
            decompressor = zlib.decompressobj()
            with open(blobs.path_for(digest), "rb") as compressed:
                while chunk := compressed.read(blobs.CHUNK):
                    check.update(decompressor.decompress(chunk))
                check.update(decompressor.flush())
            if not decompressor.eof or check.hexdigest() != old_digest:
                raise CommandError(f"crop compression failed verification: {block.key}")
            with transaction.atomic():
                new, _ = Blob.objects.get_or_create(
                    digest=digest,
                    defaults={"size": size, "media_type": blobs.CROP_MEDIA_TYPE},
                )
                changed = Block.objects.filter(key=block.key, data=old).update(data=new)
            if not changed:
                continue
            converted += 1
            before += old.size
            after += size
            if old_digest != new.digest:
                try:
                    old.delete()
                except ProtectedError:
                    pass
                else:
                    blobs.path_for(old_digest).unlink(missing_ok=True)
        self.stdout.write(
            f"Compressed {converted} crop blocks: {before:,} -> {after:,} bytes"
        )