"""Build Chroma (and BM25) indexes from the seed corpus on disk.

Reads ``corpus/<source>/<source_key>.json`` sidecars, chunks each
variety via ``rag.chunk.chunks_from_variety``, upserts into Chroma.
With ``--rebuild``, drops + recreates the collection (clean state).
With ``--bm25-only``, skips Chroma and rebuilds only the FTS5 index
— useful for fast iteration when the chunker didn't change.

Collection name is ``<PRODUCT_NAME>_docs`` (default: ``crop_seed_docs``).
Override via the PRODUCT_NAME env var.
"""
from __future__ import annotations

import argparse
import logging
import os
import time
from pathlib import Path
from typing import Iterator

import chromadb
from chromadb.config import Settings

from .chunk import chunks_from_variety
from .embeddings import embedding_function

log = logging.getLogger(__name__)
logging.basicConfig(level=logging.INFO, format="%(asctime)s  %(message)s")

ROOT = Path(__file__).resolve().parent.parent
CORPUS = ROOT / "corpus"
CHROMA_DIR = ROOT / "chroma"

PRODUCT_NAME = os.environ.get("PRODUCT_NAME", "crop_seed")
COLLECTION = f"{PRODUCT_NAME}_docs"


def variety_records() -> Iterator[dict]:
    """Walk ``corpus/<source>/<source_key>.json``, yield one chunk per
    variety."""
    if not CORPUS.exists():
        log.error("corpus/ doesn't exist; run a scraper first")
        return
    for source_dir in sorted(CORPUS.iterdir()):
        if not source_dir.is_dir() or source_dir.name.startswith("."):
            continue
        for sidecar_path in sorted(source_dir.glob("*.json")):
            yield from chunks_from_variety(sidecar_path)


def upsert_to_chroma(records: list[dict]) -> int:
    client = chromadb.PersistentClient(
        path=str(CHROMA_DIR),
        settings=Settings(anonymized_telemetry=False),
    )
    # Drop + recreate for --rebuild semantics.
    try:
        client.delete_collection(COLLECTION)
    except Exception:
        pass
    col = client.create_collection(COLLECTION, embedding_function=embedding_function())

    BATCH = 64
    total = 0
    for i in range(0, len(records), BATCH):
        chunk = records[i:i + BATCH]
        col.upsert(
            ids=[r["id"] for r in chunk],
            documents=[r["text"] for r in chunk],
            metadatas=[r["metadata"] for r in chunk],
        )
        total += len(chunk)
        log.info("upserted %d / %d chunks", total, len(records))
    return total


def main() -> int:
    p = argparse.ArgumentParser()
    p.add_argument("--rebuild", action="store_true",
                   help="Drop and recreate the Chroma collection.")
    p.add_argument("--bm25-only", action="store_true",
                   help="Rebuild only the BM25 index, skip Chroma.")
    p.add_argument("--bm25-db", type=Path,
                   default=ROOT / "bm25" / f"{PRODUCT_NAME}_docs.db",
                   help="Path to the BM25 sqlite db.")
    args = p.parse_args()

    log.info("reading corpus from %s", CORPUS)
    t0 = time.time()
    records = list(variety_records())
    log.info("loaded %d chunks in %.1fs", len(records), time.time() - t0)
    if not records:
        log.error("no chunks — is corpus/ populated?")
        return 1

    if args.bm25_only:
        from .bm25 import BM25Index
        log.info("--bm25-only: building FTS5 only")
        BM25Index(args.bm25_db).build(records)
        return 0

    if not args.rebuild:
        log.info("no --rebuild; nothing to do. (Use --rebuild to upsert.)")
        return 0

    t_c = time.time()
    n = upsert_to_chroma(records)
    log.info("chroma: %d chunks in %.1fs", n, time.time() - t_c)

    try:
        from .bm25 import BM25Index
        t_b = time.time()
        BM25Index(args.bm25_db).build(records)
        log.info("bm25 done in %.1fs", time.time() - t_b)
    except ImportError:
        log.info("rag.bm25 not available — skipping BM25 build")
    return 0


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