"""
Preprocess raw UMLS data into a simplified CSV for FAISS indexing.
Accepts a TSV/CSV with columns CUI, STR (string), DEF, SAB (source).
Outputs a clean CSV with headers: cui,name,definition,source.

Usage:
 python preprocess_umls_data.py \
   --input raw_umls.tsv \
   --output processed/concepts.csv \
   --sep '\t'
"""
import argparse
import pandas as pd

def main():
    parser = argparse.ArgumentParser(description="Preprocess UMLS raw data.")
    parser.add_argument('--input', required=True,
                        help='Raw UMLS file (TSV/CSV)')
    parser.add_argument('--output', required=True,
                        help='Output CSV for concepts')
    parser.add_argument('--sep', default='\t',
                        help='Separator for input file')
    args = parser.parse_args()

    # Read raw file
    df = pd.read_csv(args.input, sep=args.sep, dtype=str)

    # Expect columns: CUI, STR, DEF, SAB
    df = df.rename(columns={
        'CUI': 'cui',
        'STR': 'name',
        'DEF': 'definition',
        'SAB': 'source'
    })

    # Drop rows missing CUI or name
    df = df.dropna(subset=['cui', 'name'])

    # Fill missing definitions/sources
    df['definition'] = df['definition'].fillna('')
    df['source'] = df['source'].fillna('')

    # Deduplicate by CUI + name
    df = df.drop_duplicates(subset=['cui', 'name'])

    # Output
    df.to_csv(args.output, index=False)
    print(f"Processed {len(df)} concepts to {args.output}")

if __name__ == '__main__':
    main()