"""Reference document persistence, delete, and re-ingest."""

from __future__ import annotations

import logging
import shutil
import threading
import time
from datetime import UTC, datetime
from pathlib import Path

from backend.config import settings
from backend.core import ingest
from backend.core.rag_store import TIER_REFERENCE, get_rag_store
from backend.core.report_session import (
    UploadedDocument,
    delete_document,
    get_document,
    list_documents,
    save_document,
)
from backend.core.style_profile import invalidate_style_profile
from backend.utils import tenant_store

logger = logging.getLogger(__name__)

_reingest_lock = threading.Lock()
_reingest_running: set[str] = set()


def is_reingest_running(tenant_id: str) -> bool:
    with _reingest_lock:
        return tenant_id in _reingest_running


def recover_stale_processing_documents(tenant_id: str) -> int:
    """Reset orphaned ``processing`` rows when no re-ingest worker is active."""
    if is_reingest_running(tenant_id):
        return 0
    recovered = 0
    for _doc_id, doc in list_documents(tenant_id).items():
        if doc.status == "processing":
            doc.status = "complete"
            doc.error = None
            save_document(tenant_id, doc)
            recovered += 1
    if recovered:
        logger.info(
            "Recovered %d stale processing document(s) for tenant=%s",
            recovered,
            tenant_id,
        )
    return recovered


def recover_all_tenants_stale_processing() -> int:
    """On startup, clear processing flags left by a killed background worker."""
    tenants_root = settings.data_dir_path / "tenants"
    if not tenants_root.is_dir():
        return 0
    total = 0
    for tenant_dir in sorted(tenants_root.iterdir()):
        if not tenant_dir.is_dir():
            continue
        if not (tenant_dir / "compat_documents.json").is_file():
            continue
        total += recover_stale_processing_documents(tenant_dir.name)
    return total


def reingest_progress(tenant_id: str) -> dict:
    docs = list_documents(tenant_id)
    counts = {"complete": 0, "processing": 0, "failed": 0, "pending": 0}
    for doc in docs.values():
        key = doc.status if doc.status in counts else "pending"
        counts[key] = counts.get(key, 0) + 1
    return {
        "total": len(docs),
        "running": is_reingest_running(tenant_id),
        **counts,
    }


def document_created_at_iso(doc: UploadedDocument) -> str:
    """Serialize ``created_at`` for API responses (ISO-8601 UTC)."""
    ts = doc.created_at
    if isinstance(ts, (int, float)) and ts > 0:
        return datetime.fromtimestamp(ts, tz=UTC).isoformat()
    if isinstance(ts, str) and ts.strip():
        return ts.strip()
    return datetime.now(tz=UTC).isoformat()


def persist_reference_file(
    tenant_id: str,
    document_id: str,
    source_path: Path,
    *,
    original_filename: str,
) -> Path:
    """Copy an uploaded file into tenant storage for later re-ingest."""
    suffix = source_path.suffix.lower() or Path(original_filename).suffix.lower()
    dest = tenant_store.reference_upload_path(tenant_id, document_id, suffix)
    shutil.copy2(source_path, dest)
    return dest


def ingest_and_register(
    tenant_id: str,
    source_path: Path,
    *,
    original_filename: str,
    document_id: str | None = None,
) -> UploadedDocument:
    """Ingest a reference file and record it in the document library."""
    from backend.core.report_session import new_document_id

    doc_id = document_id or new_document_id()
    stored = persist_reference_file(
        tenant_id, doc_id, source_path, original_filename=original_filename
    )
    chunks = ingest.ingest_reference(tenant_id, stored)
    doc = UploadedDocument(
        document_id=doc_id,
        filename=original_filename or stored.name,
        status="complete",
        ingested_chunks=chunks,
        storage_path=str(stored),
        file_size=stored.stat().st_size if stored.is_file() else 0,
        created_at=time.time(),
    )
    save_document(tenant_id, doc)
    invalidate_style_profile(tenant_id)
    return doc


def remove_reference_document(tenant_id: str, document_id: str) -> int:
    """Remove chunks, stored file, and library record. Returns chunks removed."""
    doc = get_document(tenant_id, document_id)
    if doc is None:
        raise KeyError("Document not found")

    removed = get_rag_store().remove_document(
        tenant_id,
        TIER_REFERENCE,
        source_filename=doc.filename,
        doc_id=f"reference:{doc.filename}",
    )
    if doc.storage_path:
        path = Path(doc.storage_path)
        if path.is_file():
            path.unlink(missing_ok=True)
    delete_document(tenant_id, document_id)
    invalidate_style_profile(tenant_id)
    return removed


def reingest_reference_document(tenant_id: str, document_id: str) -> UploadedDocument:
    """Re-process one stored reference file through the current pipeline."""
    doc = get_document(tenant_id, document_id)
    if doc is None:
        raise KeyError("Document not found")

    path = Path(doc.storage_path) if doc.storage_path else None
    if path is None or not path.is_file():
        raise FileNotFoundError("Source file is no longer on disk; cannot re-ingest.")

    doc.status = "processing"
    doc.error = None
    save_document(tenant_id, doc)

    get_rag_store().remove_document(
        tenant_id,
        TIER_REFERENCE,
        source_filename=doc.filename,
        doc_id=f"reference:{doc.filename}",
    )
    chunks = ingest.ingest_reference(tenant_id, path)
    doc.status = "complete"
    doc.error = None
    doc.ingested_chunks = chunks
    doc.file_size = path.stat().st_size
    save_document(tenant_id, doc)
    invalidate_style_profile(tenant_id)
    return doc


def reingest_all_documents(
    tenant_id: str,
    *,
    skip_document_ids: set[str] | None = None,
) -> dict:
    skip = skip_document_ids or set()
    docs = list_documents(tenant_id)
    queued: list[str] = []
    skipped_missing = 0
    skipped_active = 0

    for doc_id, doc in docs.items():
        if doc_id in skip:
            skipped_active += 1
            continue
        try:
            logger.info("Re-ingesting %s for tenant=%s", doc.filename, tenant_id)
            updated = reingest_reference_document(tenant_id, doc_id)
            queued.append(doc_id)
            logger.info(
                "Re-ingested %s (%d chunks)",
                updated.filename,
                updated.ingested_chunks,
            )
        except FileNotFoundError:
            skipped_missing += 1
        except Exception as exc:  # noqa: BLE001
            doc.status = "failed"
            doc.error = str(exc)
            save_document(tenant_id, doc)

    return {
        "queued": len(queued),
        "document_ids": queued,
        "skipped_active": skipped_active,
        "skipped_missing_file": skipped_missing,
        "detail": (
            f"Re-ingested {len(queued)} document(s); "
            f"skipped {skipped_active} blocked and {skipped_missing} missing-file."
        ),
    }


def schedule_reingest_all_documents(
    tenant_id: str,
    *,
    skip_document_ids: set[str] | None = None,
) -> dict:
    """Queue a full-library re-ingest on a background thread (non-blocking HTTP).

    Only the document currently being embedded is marked ``processing`` so a
    server restart cannot strand the whole library in that state.
    """
    skip = skip_document_ids or set()
    docs = list_documents(tenant_id)
    to_queue = [doc_id for doc_id in docs if doc_id not in skip]

    with _reingest_lock:
        if tenant_id in _reingest_running:
            progress = reingest_progress(tenant_id)
            return {
                "queued": 0,
                "document_ids": [],
                "skipped_active": len(skip),
                "skipped_missing_file": 0,
                "reingest_running": True,
                "progress": progress,
                "detail": (
                    f"Re-ingest already running "
                    f"({progress['processing']} processing, "
                    f"{progress['complete']} ready)."
                ),
            }
        _reingest_running.add(tenant_id)

    # Clear orphaned processing flags from a prior killed worker.
    recover_stale_processing_documents(tenant_id)

    def _worker() -> None:
        try:
            logger.info(
                "Background re-ingest started for tenant=%s (%d documents)",
                tenant_id,
                len(to_queue),
            )
            reingest_all_documents(tenant_id, skip_document_ids=skip)
        except Exception:  # noqa: BLE001
            logger.exception("Background re-ingest failed for tenant=%s", tenant_id)
            recover_stale_processing_documents(tenant_id)
        finally:
            with _reingest_lock:
                _reingest_running.discard(tenant_id)
            logger.info("Background re-ingest finished for tenant=%s", tenant_id)

    threading.Thread(
        target=_worker,
        name=f"reingest-{tenant_id}",
        daemon=True,
    ).start()

    progress = reingest_progress(tenant_id)
    return {
        "queued": len(to_queue),
        "document_ids": to_queue,
        "skipped_active": len(skip),
        "skipped_missing_file": 0,
        "reingest_running": True,
        "progress": progress,
        "detail": (
            f"Re-ingest started in the background for {len(to_queue)} document(s). "
            "Status updates every few seconds as each file completes."
        ),
    }


def schedule_reingest_reference_document(tenant_id: str, document_id: str) -> dict:
    """Queue a single-document re-ingest on a background thread."""
    doc = get_document(tenant_id, document_id)
    if doc is None:
        raise KeyError("Document not found")

    path = Path(doc.storage_path) if doc.storage_path else None
    if path is None or not path.is_file():
        raise FileNotFoundError("Source file is no longer on disk; cannot re-ingest.")

    doc.status = "processing"
    doc.error = None
    save_document(tenant_id, doc)

    def _worker() -> None:
        try:
            reingest_reference_document(tenant_id, document_id)
        except Exception as exc:  # noqa: BLE001
            failed = get_document(tenant_id, document_id)
            if failed is not None:
                failed.status = "failed"
                failed.error = str(exc)
                save_document(tenant_id, failed)

    threading.Thread(
        target=_worker,
        name=f"reingest-{tenant_id}-{document_id[:8]}",
        daemon=True,
    ).start()

    return {
        "queued": 1,
        "document_ids": [document_id],
        "detail": f"Re-ingest started in the background for {doc.filename}.",
    }