import os
import shutil

import boto3
from django.conf import settings
from django.db import migrations, models
from django.db.backends.postgresql.schema import DatabaseSchemaEditor
from django.db.migrations.state import StateApps


class Uploader:
    def __init__(self) -> None:
        self.old_orig_image_path_template = "{realm_id}/emoji/{emoji_file_name}.original"
        self.old_path_template = "{realm_id}/emoji/{emoji_file_name}"
        self.new_orig_image_path_template = "{realm_id}/emoji/images/{emoji_file_name}.original"
        self.new_path_template = "{realm_id}/emoji/images/{emoji_file_name}"

    def copy_files(self, src_path: str, dst_path: str) -> None:
        raise NotImplementedError()

    def ensure_emoji_images(self, realm_id: int, old_filename: str, new_filename: str) -> None:
        # Copy original image file.
        old_file_path = self.old_orig_image_path_template.format(
            realm_id=realm_id, emoji_file_name=old_filename
        )
        new_file_path = self.new_orig_image_path_template.format(
            realm_id=realm_id, emoji_file_name=new_filename
        )
        self.copy_files(old_file_path, new_file_path)

        # Copy resized image file.
        old_file_path = self.old_path_template.format(
            realm_id=realm_id, emoji_file_name=old_filename
        )
        new_file_path = self.new_path_template.format(
            realm_id=realm_id, emoji_file_name=new_filename
        )
        self.copy_files(old_file_path, new_file_path)


class LocalUploader(Uploader):
    def __init__(self) -> None:
        super().__init__()

    @staticmethod
    def mkdirs(path: str) -> None:
        dirname = os.path.dirname(path)
        if not os.path.isdir(dirname):
            os.makedirs(dirname)

    def copy_files(self, src_path: str, dst_path: str) -> None:
        src_path = os.path.join(settings.LOCAL_UPLOADS_DIR, "avatars", src_path)
        self.mkdirs(src_path)
        dst_path = os.path.join(settings.LOCAL_UPLOADS_DIR, "avatars", dst_path)
        self.mkdirs(dst_path)
        shutil.copyfile(src_path, dst_path)


class S3Uploader(Uploader):
    def __init__(self) -> None:
        super().__init__()
        session = boto3.Session(settings.S3_KEY, settings.S3_SECRET_KEY)
        self.bucket_name = settings.S3_AVATAR_BUCKET
        self.bucket = session.resource(
            "s3", region_name=settings.S3_REGION, endpoint_url=settings.S3_ENDPOINT_URL
        ).Bucket(self.bucket_name)

    def copy_files(self, src_key: str, dst_key: str) -> None:
        source = dict(Bucket=self.bucket_name, Key=src_key)
        self.bucket.copy(source, dst_key)


def get_uploader() -> Uploader:
    if settings.LOCAL_UPLOADS_DIR is None:
        return S3Uploader()
    return LocalUploader()


def get_emoji_file_name(emoji_file_name: str, new_name: str) -> str:
    _, image_ext = os.path.splitext(emoji_file_name)
    return "".join((new_name, image_ext))


def migrate_realm_emoji_image_files(apps: StateApps, schema_editor: DatabaseSchemaEditor) -> None:
    RealmEmoji = apps.get_model("zerver", "RealmEmoji")
    uploader = get_uploader()
    for realm_emoji in RealmEmoji.objects.all():
        old_file_name = realm_emoji.file_name
        new_file_name = get_emoji_file_name(old_file_name, str(realm_emoji.id))
        uploader.ensure_emoji_images(realm_emoji.realm_id, old_file_name, new_file_name)
        realm_emoji.file_name = new_file_name
        realm_emoji.save(update_fields=["file_name"])


def reversal(apps: StateApps, schema_editor: DatabaseSchemaEditor) -> None:
    # Ensures that migration can be re-run in case of a failure.
    RealmEmoji = apps.get_model("zerver", "RealmEmoji")
    for realm_emoji in RealmEmoji.objects.all():
        corrupt_file_name = realm_emoji.file_name
        correct_file_name = get_emoji_file_name(corrupt_file_name, realm_emoji.name)
        realm_emoji.file_name = correct_file_name
        realm_emoji.save(update_fields=["file_name"])


class Migration(migrations.Migration):

    dependencies = [
        ("zerver", "0148_max_invites_forget_default"),
    ]

    operations = [
        migrations.AlterUniqueTogether(
            name="realmemoji",
            unique_together=set(),
        ),
        migrations.AlterField(
            model_name="realmemoji",
            name="file_name",
            field=models.TextField(db_index=True, null=True, blank=True),
        ),
        migrations.RunPython(migrate_realm_emoji_image_files, reverse_code=reversal, elidable=True),
    ]