"""
Upload queue: when Supabase Storage is ≥95% full, uploads are queued.
The queue is stored in the `upload_queue` table. A background sweep runs
on every /upload and /health request to drain the queue when space frees up
(docs expire and are cleaned up by the expiry sweeper in app.py).
"""
from __future__ import annotations

from datetime import datetime, UTC
from supabase import create_client
import os
import uuid as _uuid

# ── configurable limits ──────────────────────────────────────────────────────
# Default: 950 MB = ~95% of Supabase free 1 GB storage tier
QUOTA_BYTES: int = int(os.environ.get("STORAGE_QUOTA_BYTES", str(950 * 1024 * 1024)))
# Average seconds to fully process one document (parse+embed)
AVG_PROCESS_SECS: int = int(os.environ.get("AVG_PROCESS_SECS", "120"))


def _client():
    return create_client(os.environ["SUPABASE_URL"], os.environ["SUPABASE_KEY"])


# ── storage accounting ───────────────────────────────────────────────────────

def get_used_storage_bytes() -> int:
    """Sum file_size_bytes of all non-expired, non-failed documents."""
    now = datetime.now(UTC).isoformat()
    result = (
        _client()
        .table("documents")
        .select("file_size_bytes")
        .gt("expires_at", now)
        .neq("status", "error")
        .execute()
    )
    return sum((row.get("file_size_bytes") or 0) for row in (result.data or []))


def is_storage_near_full(new_file_bytes: int = 0) -> bool:
    return (get_used_storage_bytes() + new_file_bytes) >= QUOTA_BYTES


# ── queue management ─────────────────────────────────────────────────────────

def enqueue_upload(
    user_id: str,
    filename: str,
    file_size_bytes: int,
    file_content: bytes,
    content_type: str,
) -> dict:
    """
    Store the raw file in Supabase Storage under a temp 'queue/' prefix,
    insert a row into upload_queue, and return queue position + ETA.
    """
    client = _client()
    queue_id = str(_uuid.uuid4())
    storage_path = f"queue/{user_id}/{queue_id}/{filename}"

    client.storage.from_("documents").upload(
        path=storage_path,
        file=file_content,
        file_options={"content-type": content_type or "application/octet-stream"},
    )

    # Count items already waiting so we can give an accurate position
    waiting: int = (
        client.table("upload_queue")
        .select("id", count="exact")
        .eq("status", "waiting")
        .execute()
        .count
        or 0
    )
    position = waiting + 1

    client.table("upload_queue").insert({
        "id": queue_id,
        "user_id": user_id,
        "filename": filename,
        "file_size_bytes": file_size_bytes,
        "content_type": content_type or "application/octet-stream",
        "storage_path": storage_path,
        "status": "waiting",
    }).execute()

    est_mins = round((position * AVG_PROCESS_SECS) / 60, 1)
    return {
        "queued": True,
        "queue_id": queue_id,
        "position": position,
        "estimated_wait_minutes": est_mins,
    }


def get_queue_status(user_id: str, queue_id: str) -> dict:
    """Return current queue position, ETA, or final doc_id if done."""
    client = _client()
    try:
        row = (
            client.table("upload_queue")
            .select("*")
            .eq("id", queue_id)
            .eq("user_id", user_id)
            .single()
            .execute()
        )
    except Exception:
        return {"status": "not_found"}

    if not row.data:
        return {"status": "not_found"}

    data = row.data
    if data["status"] == "done":
        return {"status": "done", "doc_id": data.get("doc_id")}
    if data["status"] == "failed":
        return {"status": "failed", "error": data.get("error", "Unknown error")}
    if data["status"] == "processing":
        return {"status": "processing", "position": 0, "estimated_wait_minutes": 1}

    # Count items queued before this one
    position: int = (
        client.table("upload_queue")
        .select("id", count="exact")
        .eq("status", "waiting")
        .lt("queued_at", data["queued_at"])
        .execute()
        .count
        or 0
    ) + 1

    est_mins = round((position * AVG_PROCESS_SECS) / 60, 1)
    return {
        "status": "waiting",
        "position": position,
        "estimated_wait_minutes": est_mins,
    }


# ── background queue drainer ─────────────────────────────────────────────────

async def try_process_next_queued() -> bool:
    """
    Process the oldest waiting queue item if storage has freed up.
    Returns True if an item was processed (caller can chain calls).
    Designed to run as a FastAPI BackgroundTask.
    """
    # Lazy imports to avoid circular dependencies
    from ingestion.parser import parse_file
    from ingestion.chunker import smart_chunk
    from retrieval.embedder import embed_chunks
    from retrieval.vectorstore import store_chunks
    from persistence.tier import get_user_tier, get_expiry

    client = _client()

    # Check storage; bail early if still full
    if is_storage_near_full():
        return False

    # Grab oldest waiting item
    result = (
        client.table("upload_queue")
        .select("*")
        .eq("status", "waiting")
        .order("queued_at")
        .limit(1)
        .execute()
    )
    if not result.data:
        return False

    item = result.data[0]
    queue_id = item["id"]

    # Mark as processing (prevents double-processing if two requests fire simultaneously)
    client.table("upload_queue").update({"status": "processing"}).eq("id", queue_id).execute()

    try:
        # Retrieve from temp storage
        file_bytes: bytes = client.storage.from_("documents").download(item["storage_path"])

        user_id   = item["user_id"]
        filename  = item["filename"]
        file_size = item.get("file_size_bytes", len(file_bytes))
        tier      = get_user_tier(user_id)
        expires   = get_expiry(tier)
        doc_id    = str(_uuid.uuid4())
        perm_path = f"{user_id}/{doc_id}/{filename}"

        # Move to permanent storage path
        client.storage.from_("documents").upload(
            path=perm_path,
            file=file_bytes,
            file_options={"content-type": item["content_type"]},
        )

        # Create document metadata row
        client.table("documents").insert({
            "id": doc_id,
            "user_id": user_id,
            "filename": filename,
            "status": "processing",
            "tier_at_upload": str(tier),
            "expires_at": expires.isoformat(),
            "file_size_bytes": file_size,
        }).execute()

        # Parse → chunk → embed → store
        text   = parse_file(file_bytes, filename)
        chunks = smart_chunk(text)
        embeds = embed_chunks(chunks)
        store_chunks(doc_id, user_id, chunks, embeds, expires)

        client.table("documents").update({
            "status": "ready",
            "chunk_count": len(chunks),
        }).eq("id", doc_id).execute()

        # Mark queue item done
        client.table("upload_queue").update({
            "status": "done",
            "doc_id": doc_id,
            "processed_at": datetime.now(UTC).isoformat(),
        }).eq("id", queue_id).execute()

        # Remove temp file to free storage
        try:
            client.storage.from_("documents").remove([item["storage_path"]])
        except Exception:
            pass

        return True

    except Exception as exc:
        client.table("upload_queue").update({
            "status": "failed",
            "error": str(exc),
        }).eq("id", queue_id).execute()
        return False


# ── expiry sweeper ───────────────────────────────────────────────────────────

def sweep_expired_documents() -> int:
    """
    Delete expired documents from Storage + their DB rows.
    Returns count deleted. Call from background tasks so the queue can drain.
    """
    client = _client()
    now = datetime.now(UTC).isoformat()
    expired = (
        client.table("documents")
        .select("id,user_id,filename")
        .lt("expires_at", now)
        .execute()
        .data
        or []
    )
    deleted = 0
    for doc in expired:
        # Best-effort storage delete
        try:
            path = f"{doc['user_id']}/{doc['id']}/{doc['filename']}"
            client.storage.from_("documents").remove([path])
        except Exception:
            pass
        # Remove chunks
        try:
            client.table("chunks").delete().eq("doc_id", doc["id"]).execute()
        except Exception:
            pass
        # Remove doc row
        try:
            client.table("documents").delete().eq("id", doc["id"]).execute()
        except Exception:
            pass
        deleted += 1

    return deleted