#!/usr/bin/env python3
"""csv_summary.py — Read a CSV from stdin or a file argument and emit JSON summary statistics."""

import sys
import json
import csv
from collections import defaultdict
from statistics import mean, median

def summarize_csv(path=None):
    fh = open(path, newline='') if path else sys.stdin
    reader = csv.DictReader(fh)
    rows = list(reader)
    fh.close() if path else None

    if not rows:
        return {"rows": 0, "columns": [], "numeric": {}}

    columns = reader.fieldnames or []
    numeric = {}
    for col in columns:
        values = []
        for row in rows:
            try:
                values.append(float(row[col]))
            except (ValueError, TypeError):
                pass
        if values:
            numeric[col] = {
                "count": len(values),
                "sum": round(sum(values), 4),
                "mean": round(mean(values), 4),
                "median": round(median(values), 4),
                "min": round(min(values), 4),
                "max": round(max(values), 4),
            }

    return {
        "rows": len(rows),
        "columns": columns,
        "numeric": numeric,
    }

def main():
    path = sys.argv[1] if len(sys.argv) > 1 else None
    result = summarize_csv(path)
    json.dump(result, sys.stdout, indent=2)
    sys.stdout.write("\n")

if __name__ == "__main__":
    main()