#!/usr/bin/env python3
"""
csv_to_json.py

Convert a CSV into a JSON array where each element is

{
  "<value from column 2>": {
    "data_type": "<value from column 4>",
    "tag_name": "<value from column 2>"
  }
}

Only rows whose first column is exactly "TAG" are included.
"""

import csv
import json
import sys
from pathlib import Path

def csv_to_tag_json(csv_path: Path, json_path: Path) -> None:
    """
    Parameters
    ----------
    csv_path : Path
        Path to the source CSV file.
    json_path : Path
        Path where the output JSON should be written.
    """
    tag_rows = {}

    # open the CSV file.  Assume UTF‑8, but you can change if needed.
    with csv_path.open(newline='', encoding='utf-8') as f:
        reader = csv.reader(f)
        for row_index, row in enumerate(reader, start=1):
            # guard against empty rows
            if not row:
                continue

            # Ensure we have at least 5 columns (index 0..4)
            if len(row) < 5:
                print(f"⚠️  Skipping line {row_index}: not enough columns", file=sys.stderr)
                continue

            # Row 0 must be exactly "TAG" (case‑sensitive)
            if row[0] != "TAG":
                continue

            tag_name  = row[2]
            data_type = row[4]

            # Build the object exactly as you asked
            tag_rows[tag_name] = {
                "data_type": data_type,
                "tag_name": tag_name
            }
           

    # Write the list of objects as pretty‑printed JSON
    with json_path.open('w', encoding='utf-8') as f:
        json.dump(tag_rows, f, indent=2, ensure_ascii=False)

    print(f"✅  Wrote {len(tag_rows)} rows to {json_path}")

if __name__ == "__main__":
    # Usage:  python csv_to_json.py input.csv output.json
    if len(sys.argv) != 3:
        print(f"Usage: {sys.argv[0]} <input.csv> <output.json>", file=sys.stderr)
        sys.exit(1)

    csv_file  = Path(sys.argv[1])
    json_file = Path(sys.argv[2])

    if not csv_file.exists():
        print(f"❌  File not found: {csv_file}", file=sys.stderr)
        sys.exit(1)

    csv_to_tag_json(csv_file, json_file)