"""Private, best-effort acquisition observations, separate from source evidence."""
from datetime import datetime, timezone

from .capture_job import atomic_json, fingerprint


VERSION = "arr-acquisition-progress/v1"
PHASES = frozenset({"queued", "searching", "fetching", "verifying", "completed", "failed", "interrupted"})
PUBLIC_FIELDS = frozenset({"phase", "completed", "total", "percent", "updated_at"})


def snapshot(phase, completed=0, total=None, *, updated_at=None):
    percent = (100 if phase == "completed" else 0 if phase == "queued" else
               min(99, completed * 100 // total) if total else 99 if total == 0 else None)
    return validate({"phase": phase, "completed": completed, "total": total, "percent": percent,
                     "updated_at": updated_at or datetime.now(timezone.utc).isoformat()})


def validate(value):
    """Return only the fixed privacy-safe public contract; reject malformed data."""
    if type(value) is not dict or set(value) != PUBLIC_FIELDS or value["phase"] not in PHASES:
        raise ValueError("invalid acquisition progress")
    completed, total, percent = value["completed"], value["total"], value["percent"]
    if type(completed) is not int or not 0 <= completed <= 10000000:
        raise ValueError("invalid acquisition count")
    if total is not None and (type(total) is not int or not completed <= total <= 10000000):
        raise ValueError("invalid acquisition total")
    if percent is not None and (type(percent) is not int or not 0 <= percent <= 100):
        raise ValueError("invalid acquisition percent")
    if value["phase"] == "completed":
        if total is None or completed != total or percent != 100:
            raise ValueError("incomplete acquisition")
    elif percent == 100:
        raise ValueError("premature acquisition completion")
    stamp = value["updated_at"]
    if type(stamp) is not str or len(stamp) > 40 or datetime.fromisoformat(stamp).tzinfo is None:
        raise ValueError("invalid acquisition timestamp")
    return dict(value)


def publish(folder, identity, phase, completed=0, total=None):
    """An observation failure must never change the source collection outcome."""
    try:
        atomic_json(folder / "progress.json", {"version": VERSION, "identity_sha256": fingerprint(identity),
                    "progress": snapshot(phase, completed, total)}, replace=True)
    except Exception:
        pass