import csv
from pathlib import Path

def merge_wgcompany_times(local_path, merge_path, output_path=None):
    """
    Merge two wgcompany_times.csv files, deduplicate by listing_id and timestamp.
    local_path: main data/wgcompany_times.csv
    merge_path: data/to_merge/wgcompany_times.csv
    output_path: where to write merged file (default: overwrite local_path)
    """
    output_path = output_path or local_path
    seen = set()
    rows = []
    # Read both files
    for path in [local_path, merge_path]:
        with open(path, newline='', encoding='utf-8') as f:
            reader = csv.DictReader(f)
            for row in reader:
                key = (row['listing_id'], row['timestamp'])
                if key not in seen:
                    seen.add(key)
                    rows.append(row)
    # Write merged file
    with open(output_path, 'w', newline='', encoding='utf-8') as f:
        writer = csv.DictWriter(f, fieldnames=rows[0].keys())
        writer.writeheader()
        writer.writerows(rows)
    print(f"Merged {len(rows)} unique rows to {output_path}")

if __name__ == "__main__":
    merge_wgcompany_times(
        "data/wgcompany_times.csv",
        "data/to_merge/wgcompany_times.csv"
    )