#!/usr/bin/env python3
"""
Extract the structural schema of a compliance xlsx file as JSON.
Usage: python3 extract_xlsx_schema.py <path_to_xlsx>

Output:
{
  "sheets": [
    {
      "name": "Summary",
      "columns": ["Metric", "Non-Compliant", "..."],
      "metric_values": ["2.3.4i", "5.2.4", "..."]
    },
    {
      "name": "2.3.4i",
      "columns": ["Preferred - Hostname", "GRANITE - IPv4_Address", "..."]
    }
  ]
}

- Uses openpyxl in read-only mode.
- Extracts sheet names, first-row column headers per sheet, and unique metric
  values from the Summary sheet (header at row 4, data from row 5 onward).
- On error, returns { "error": "..." } on stdout and exits with non-zero code.

Dependencies: openpyxl (already in requirements.txt)
"""
import sys
import json
from openpyxl import load_workbook


def main():
    if len(sys.argv) < 2:
        print(json.dumps({"error": "No file path provided"}))
        sys.exit(1)

    filepath = sys.argv[1]

    try:
        wb = load_workbook(filepath, read_only=True, data_only=True)
    except Exception as e:
        print(json.dumps({"error": f"Cannot open file: {str(e)}"}))
        sys.exit(1)

    if not wb.sheetnames:
        print(json.dumps({"error": "Workbook contains no sheets"}))
        wb.close()
        sys.exit(1)

    sheets = []
    for sheet_name in wb.sheetnames:
        ws = wb[sheet_name]

        # Extract first-row column headers
        rows = list(ws.iter_rows(max_row=1, values_only=True))
        columns = [str(c).strip() for c in rows[0] if c is not None] if rows else []

        entry = {
            "name": sheet_name,
            "columns": columns,
        }

        # Extract metric values from the Summary sheet
        # Summary has header at row 4, data from row 5 onward
        if sheet_name == "Summary":
            metric_values = []
            header_rows = list(ws.iter_rows(min_row=4, max_row=4, values_only=True))
            if header_rows:
                summary_cols = [str(c).strip() if c else "" for c in header_rows[0]]
                metric_idx = None
                for i, col in enumerate(summary_cols):
                    if col == "Metric":
                        metric_idx = i
                        break
                if metric_idx is not None:
                    for row in ws.iter_rows(min_row=5, values_only=True):
                        if row[metric_idx] is not None:
                            val = str(row[metric_idx]).strip()
                            if val and val != "Metric":
                                metric_values.append(val)
            entry["metric_values"] = sorted(set(metric_values))

        sheets.append(entry)

    wb.close()
    print(json.dumps({"sheets": sheets}))


if __name__ == "__main__":
    main()