"""§22 collection grain — resolution helpers beneath the project tier.

In S1 each project has exactly one collection (the default). These helpers
recover the collection for a project and read the per-corpus fields (`type`,
`initial_state`) that moved down from `projects` in migration 029. Project-grain
authz (auth.py) recovers a row's project by joining `collections` on
`collection_id`.
"""
from __future__ import annotations

from . import db

DEFAULT_COLLECTION_ID = "default"


def default_collection_id(project_id: str) -> str:
    """The id of a project's default (S1: sole) collection. Falls back to the
    literal 'default' when the project has no collection row yet."""
    row = db.conn().execute(
        "SELECT id FROM collections WHERE project_id = ? ORDER BY created_at, id LIMIT 1",
        (project_id,),
    ).fetchone()
    return row["id"] if row else DEFAULT_COLLECTION_ID


def project_of_collection(collection_id: str) -> str | None:
    """The project a collection belongs to, or None if unknown."""
    row = db.conn().execute(
        "SELECT project_id FROM collections WHERE id = ?", (collection_id,)
    ).fetchone()
    return row["project_id"] if row else None


def collection_initial_state(collection_id: str) -> str:
    """§22.4b landing state for new entries in a collection. 'super-draft'
    default for an unknown/unset row (today's safe flow)."""
    row = db.conn().execute(
        "SELECT initial_state FROM collections WHERE id = ?", (collection_id,)
    ).fetchone()
    if row is None or not row["initial_state"]:
        return "super-draft"
    return row["initial_state"]


def collection_type(collection_id: str) -> str:
    """The collection's immutable §22.4a type. 'document' default for unknown."""
    row = db.conn().execute(
        "SELECT type FROM collections WHERE id = ?", (collection_id,)
    ).fetchone()
    return row["type"] if row and row["type"] else "document"