#!/usr/bin/env python3
"""Structural verifier for the countries extraction table.

Usage:
    python3 check_countries.py <csv_path> <expected_rows>

Exits 0 iff the CSV satisfies the contract:
  - header is exactly the 14-column contract (see HEADERS)
  - every data row has exactly 14 fields
  - alpha-2 codes are unique and there are exactly expected_rows rows

Exits 1 with a detailed message otherwise. The exit code IS the verdict:
0 = correct, nonzero = wrong.
"""
import csv
import sys

EXPECTED_HEADER = [
    'name_common', 'name_official', 'alpha2', 'alpha3', 'numeric',
    'region', 'subregion', 'capital', 'population', 'area_km2',
    'currencies', 'languages', 'tlds', 'flag',
]


def main():
    if len(sys.argv) != 3:
        sys.stderr.write('usage: check_countries.py <csv_path> <expected_rows>\n')
        return 2
    csv_path, expected_raw = sys.argv[1], sys.argv[2]
    try:
        expected = int(expected_raw)
    except ValueError:
        sys.stderr.write('expected_rows must be an integer\n')
        return 2
    try:
        fh = open(csv_path, encoding='utf-8')
    except OSError as exc:
        sys.stderr.write('cannot open %s: %s\n' % (csv_path, exc))
        return 1

    with fh:
        reader = csv.reader(fh)
        try:
            header = next(reader)
        except StopIteration:
            sys.stderr.write('CSV is empty\n')
            return 1
        if header != EXPECTED_HEADER:
            sys.stderr.write('bad header: %r\n' % header)
            return 1
        rows = list(reader)
        codes = []
        for index, row in enumerate(rows, start=2):
            if len(row) != len(EXPECTED_HEADER):
                sys.stderr.write('row %d has %d fields (expected %d)\n'
                                 % (index, len(row), len(EXPECTED_HEADER)))
                return 1
            codes.append(row[2])
        seen = set()
        duplicates = []
        for code in codes:
            if code in seen:
                duplicates.append(code)
            seen.add(code)

        ok = True
        if len(rows) != expected:
            sys.stderr.write('row count %d != expected %d\n'
                             % (len(rows), expected))
            ok = False
        if duplicates:
            sys.stderr.write('duplicate alpha-2 codes: %r\n' % sorted(duplicates))
            ok = False
        print('rows=%d fields=%d unique_alpha2=%d header_ok=True'
              % (len(rows), len(header), len(seen)))
        return 0 if ok else 1


if __name__ == '__main__':
    sys.exit(main())