"""Backfill explicit project_id into chunk and vector metadata.

Dry-run by default. The script derives ownership from the registered project
ingest roots and updates both SQLite source_chunks.metadata and Chroma vector
metadata only when --apply is provided.
"""

from __future__ import annotations

import argparse
import json
import sqlite3
import sys
from pathlib import Path

sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))

from atocore.models.database import get_connection  # noqa: E402
from atocore.projects.registry import derive_project_id_for_path  # noqa: E402
from atocore.retrieval.vector_store import get_vector_store  # noqa: E402

DEFAULT_BATCH_SIZE = 500


def _decode_metadata(raw: str | None) -> dict | None:
    if not raw:
        return {}
    try:
        parsed = json.loads(raw)
    except json.JSONDecodeError:
        return None
    return parsed if isinstance(parsed, dict) else None


def _chunk_rows() -> tuple[list[dict], str]:
    try:
        with get_connection() as conn:
            rows = conn.execute(
                """
                SELECT
                    sc.id AS chunk_id,
                    sc.metadata AS chunk_metadata,
                    sd.file_path AS file_path
                FROM source_chunks sc
                JOIN source_documents sd ON sd.id = sc.document_id
                ORDER BY sd.file_path, sc.chunk_index
                """
            ).fetchall()
    except sqlite3.OperationalError as exc:
        if "source_chunks" in str(exc) or "source_documents" in str(exc):
            return [], f"missing ingestion tables: {exc}"
        raise
    return [dict(row) for row in rows], ""


def _batches(items: list, batch_size: int) -> list[list]:
    return [items[i:i + batch_size] for i in range(0, len(items), batch_size)]


def backfill(
    apply: bool = False,
    project_filter: str = "",
    batch_size: int = DEFAULT_BATCH_SIZE,
    require_chroma_snapshot: bool = False,
) -> dict:
    rows, db_warning = _chunk_rows()
    updates: list[tuple[str, str, dict]] = []
    by_project: dict[str, int] = {}
    skipped_unowned = 0
    already_tagged = 0
    malformed_metadata = 0

    for row in rows:
        project_id = derive_project_id_for_path(row["file_path"])
        if project_filter and project_id != project_filter:
            continue
        if not project_id:
            skipped_unowned += 1
            continue
        metadata = _decode_metadata(row["chunk_metadata"])
        if metadata is None:
            malformed_metadata += 1
            continue
        if metadata.get("project_id") == project_id:
            already_tagged += 1
            continue
        metadata["project_id"] = project_id
        updates.append((row["chunk_id"], project_id, metadata))
        by_project[project_id] = by_project.get(project_id, 0) + 1

    missing_vectors: list[str] = []
    applied_updates = 0
    if apply and updates:
        if not require_chroma_snapshot:
            raise ValueError(
                "--apply requires --chroma-snapshot-confirmed after taking a Chroma backup"
            )
        vector_store = get_vector_store()
        for batch in _batches(updates, max(1, batch_size)):
            chunk_ids = [chunk_id for chunk_id, _, _ in batch]
            vector_payload = vector_store.get_metadatas(chunk_ids)
            existing_vector_metadata = {
                chunk_id: metadata
                for chunk_id, metadata in zip(
                    vector_payload.get("ids", []),
                    vector_payload.get("metadatas", []),
                    strict=False,
                )
                if isinstance(metadata, dict)
            }

            vector_ids = []
            vector_metadatas = []
            sql_updates = []
            for chunk_id, project_id, chunk_metadata in batch:
                vector_metadata = existing_vector_metadata.get(chunk_id)
                if vector_metadata is None:
                    missing_vectors.append(chunk_id)
                    continue
                vector_metadata = dict(vector_metadata)
                vector_metadata["project_id"] = project_id
                vector_ids.append(chunk_id)
                vector_metadatas.append(vector_metadata)
                sql_updates.append((json.dumps(chunk_metadata, ensure_ascii=True), chunk_id))

            if not vector_ids:
                continue

            vector_store.update_metadatas(vector_ids, vector_metadatas)
            with get_connection() as conn:
                cursor = conn.executemany(
                    "UPDATE source_chunks SET metadata = ? WHERE id = ?",
                    sql_updates,
                )
                if cursor.rowcount != len(sql_updates):
                    raise RuntimeError(
                        f"SQLite rowcount mismatch: {cursor.rowcount} != {len(sql_updates)}"
                    )
            applied_updates += len(sql_updates)

    return {
        "apply": apply,
        "total_chunks": len(rows),
        "updates": len(updates),
        "applied_updates": applied_updates,
        "already_tagged": already_tagged,
        "skipped_unowned": skipped_unowned,
        "malformed_metadata": malformed_metadata,
        "missing_vectors": len(missing_vectors),
        "db_warning": db_warning,
        "by_project": dict(sorted(by_project.items())),
    }


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--apply", action="store_true", help="write SQLite and Chroma metadata updates")
    parser.add_argument("--project", default="", help="optional canonical project_id filter")
    parser.add_argument("--batch-size", type=int, default=DEFAULT_BATCH_SIZE)
    parser.add_argument(
        "--chroma-snapshot-confirmed",
        action="store_true",
        help="required with --apply; confirms a Chroma snapshot exists",
    )
    args = parser.parse_args()

    payload = backfill(
        apply=args.apply,
        project_filter=args.project.strip(),
        batch_size=args.batch_size,
        require_chroma_snapshot=args.chroma_snapshot_confirmed,
    )
    print(json.dumps(payload, indent=2, ensure_ascii=True))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())