"""Direct Delivery ERN XML model.

Reads the DDEX ERN delivery file for a delivery job from the delivery XML
(vector-audit) S3 bucket and derives delivery attributes from it.
"""

import hashlib

import defusedxml.ElementTree as ElementTree

from deliveryhistory import config
from deliveryhistory.connectors import s3

# S3 key pattern for a delivery's ERN XML, keyed by the md5 hex digest of the
# job id (encoding_queue_detail_id). Mirrors the layout written by the delivery
# pipeline into the delivery XML bucket.
XML_FILE_PATH_PATTERN = 'metadata/{0}-0.xml'

# DDEX ERN tag holding the rights share for a delivery. A takedown delivers a
# share of 0.
RIGHT_SHARE_PERCENTAGE_TAG = 'RightSharePercentage'

DELIVERY_TYPE_TAKEDOWN = 'takedown'
DELIVERY_TYPE_METADATA_UPDATE = 'metadata_update'
DELIVERY_TYPE_DELIVERY = 'delivery'


def get_delivery_type(job_id):
    """Resolve the delivery type for a delivery job from its ERN XML.

    A delivery is a takedown when the RightSharePercentage in its ERN file
    is 0.

    Args:
        job_id (int): the delivery job id (encoding_queue_detail_id)

    Returns:
        str: DELIVERY_TYPE_TAKEDOWN when the delivery is a takedown,
            otherwise None.

    """
    if job_id is None:
        return None

    xml_body = s3.get_object_body(
        config.DELIVERY_XML_S3_BUCKET_NAME, _build_xml_key(job_id))
    if not xml_body:
        return None

    percentages = _right_share_percentages(xml_body)
    if percentages and all(value == 0 for value in percentages):
        return DELIVERY_TYPE_TAKEDOWN
    return None


def _build_xml_key(job_id):
    """Build the S3 key for a delivery job's ERN XML."""
    digest = hashlib.md5(str(job_id).encode(), usedforsecurity=False).hexdigest()
    return XML_FILE_PATH_PATTERN.format(digest)


def _right_share_percentages(xml_body):
    """Extract all numeric RightSharePercentage values from an ERN file."""
    root = ElementTree.fromstring(xml_body)
    values = []
    for element in root.iter():
        # ERN content elements are unqualified, but strip any namespace
        # prefix defensively before comparing the tag.
        if element.tag.rsplit('}', 1)[-1] != RIGHT_SHARE_PERCENTAGE_TAG:
            continue
        value = _to_number(element.text)
        if value is not None:
            values.append(value)
    return values


def _to_number(text):
    """Parse element text into a float, or None when not numeric."""
    try:
        return float(text)
    except (TypeError, ValueError):
        return None