"""Where uploaded documents live, and how the database refers to them.

Contracts were stored at `os.path.join(os.getcwd(), 'documents', …)`,
evaluated at upload time, and the resulting absolute path was written into
`Contract.file_path`. The storage root therefore moved with whatever
directory the process happened to be started from. Two consequences:

  - one latent: start the server from elsewhere and new contracts land in a
    new tree while the old ones become unreadable — with the database still
    saying they are there, so the failure surfaces as a 500 on download
    rather than as anything a person could act on;
  - one blocking: it rules out a release-directory deployment (OPS-011)
    outright. Every stored path would point inside a release that is about
    to be replaced, so the first switch would take every contract ever
    uploaded with it.

New rows keep a path *relative* to the document root. Old rows keep their
absolute path and are returned untouched, so this change needs no data
migration and can ship before Alembic does (DB-002).
"""

import os

#: Environment override for the document root. What a release-directory
#: deployment sets, to a path outside the releases — alongside them, not
#: inside whichever one is current.
DOCUMENTS_ROOT_ENV = 'DOCUMENTS_ROOT'

#: Sub-directory holding uploaded contracts, under the document root.
CONTRACTS_DIR = 'contrats signés'


def documents_root():
    """Absolute path of the document store.

    Falls back to `documents/` beside this package — the project root
    wherever it is installed, rather than wherever the process was launched.
    """
    configured = os.getenv(DOCUMENTS_ROOT_ENV)
    if configured:
        return os.path.abspath(configured)
    package_dir = os.path.dirname(os.path.abspath(__file__))
    return os.path.join(os.path.dirname(package_dir), 'documents')


def document_path(stored_path):
    """Absolute path of a document, from what the database holds.

    Args:
        stored_path: The value of Contract.file_path or signed_file_path.
            Relative for rows written since this module existed, absolute
            for the ones written before.

    Returns:
        str: An absolute path.
    """
    if os.path.isabs(stored_path):
        return stored_path
    return os.path.join(documents_root(), stored_path)