# See https://zulip.readthedocs.io/en/latest/subsystems/thumbnailing.html
import base64
import os
import sys
import urllib
from urllib.parse import urljoin

from django.conf import settings
from django.utils.http import url_has_allowed_host_and_scheme
from libthumbor import CryptoURL

ZULIP_PATH = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
sys.path.append(ZULIP_PATH)

from zerver.lib.camo import get_camo_url
from zthumbor.loaders.helpers import THUMBOR_EXTERNAL_TYPE, THUMBOR_LOCAL_FILE_TYPE, THUMBOR_S3_TYPE


def is_thumbor_enabled() -> bool:
    return settings.THUMBOR_URL != ""


def user_uploads_or_external(url: str) -> bool:
    return not url_has_allowed_host_and_scheme(url, allowed_hosts=None) or url.startswith(
        "/user_uploads/"
    )


def get_source_type(url: str) -> str:
    if not url.startswith("/user_uploads/"):
        return THUMBOR_EXTERNAL_TYPE

    local_uploads_dir = settings.LOCAL_UPLOADS_DIR
    if local_uploads_dir:
        return THUMBOR_LOCAL_FILE_TYPE
    return THUMBOR_S3_TYPE


def generate_thumbnail_url(path: str, size: str = "0x0", is_camo_url: bool = False) -> str:
    path = urljoin("/", path)

    if not is_thumbor_enabled():
        if url_has_allowed_host_and_scheme(path, allowed_hosts=None):
            return path
        return get_camo_url(path)

    if url_has_allowed_host_and_scheme(path, allowed_hosts=None) and not path.startswith(
        "/user_uploads/"
    ):
        return path

    source_type = get_source_type(path)
    safe_url = base64.urlsafe_b64encode(path.encode()).decode("utf-8")
    image_url = f"{safe_url}/source_type/{source_type}"
    width, height = map(int, size.split("x"))
    crypto = CryptoURL(key=settings.THUMBOR_KEY)

    smart_crop_enabled = True
    apply_filters = ["no_upscale()"]
    if is_camo_url:
        smart_crop_enabled = False
        apply_filters.append("quality(100)")
    if size != "0x0":
        apply_filters.append("sharpen(0.5,0.2,true)")

    encrypted_url = crypto.generate(
        width=width,
        height=height,
        smart=smart_crop_enabled,
        filters=apply_filters,
        image_url=image_url,
    )

    if settings.THUMBOR_URL == "http://127.0.0.1:9995":
        # If THUMBOR_URL is the default then thumbor is hosted on same machine
        # as the Zulip server and we should serve a relative URL.
        # We add a /thumbor in front of the relative URL because we make
        # use of a proxy pass to redirect request internally in Nginx to 9995
        # port where thumbor is running.
        thumbnail_url = "/thumbor" + encrypted_url
    else:
        thumbnail_url = urllib.parse.urljoin(settings.THUMBOR_URL, encrypted_url)
    return thumbnail_url