"""Django management command: ``python manage.py import_tlsdb``

Reads ``TlsDB.csv`` from the project root and populates the
``tls_ref_data`` SQLite table, replacing the CSV as the authoritative
source of TLS field-code reference metadata.

Usage:
    python manage.py import_tlsdb
    python manage.py import_tlsdb --csv /path/to/TlsDB.csv
    python manage.py import_tlsdb --clear              # re-import from scratch
"""

import csv
import os
from pathlib import Path

from django.conf import settings
from django.core.management.base import BaseCommand, CommandError
from django.db import connection, transaction


class Command(BaseCommand):
    """Import ``TlsDB.csv`` field definitions into ``tls_ref_data``."""

    help = 'Import TlsDB.csv reference data into the tls_ref_data SQLite table'

    def add_arguments(self, parser):
        parser.add_argument(
            '--csv', type=str, default=None,
            help='Path to TlsDB.csv (default: project-root/TlsDB.csv)',
        )
        parser.add_argument(
            '--clear', action='store_true', default=False,
            help='Clear existing data before importing (default: upsert)',
        )

    def _resolve_csv_path(self, provided: str | None) -> Path:
        """Locate the TlsDB.csv file.

        Priority:
        1. Explicit ``--csv`` path.
        2. Project root (where ``manage.py`` lives).
        """
        if provided:
            path = Path(provided).resolve()
        else:
            # manage.py lives in the project root — use that as anchor
            manage_dir = Path(__file__).resolve().parent.parent.parent.parent
            path = manage_dir / 'TlsDB.csv'

        if not path.exists():
            raise CommandError(f'TlsDB.csv not found at: {path}')
        return path

    def handle(self, *args, **options):
        csv_path = self._resolve_csv_path(options['csv'])
        clear = options['clear']

        # ── Parse CSV ────────────────────────────────────────────────────────
        rows: list[dict[str, str]] = []
        with open(csv_path, 'r', encoding='utf-8-sig') as f:
            reader = csv.DictReader(f)
            # Expected columns: 标题,含义,数据类型
            for line_no, row in enumerate(reader, start=2):
                field_code = (row.get('标题') or '').strip()
                meaning = (row.get('含义') or '').strip()
                data_type = (row.get('数据类型') or '').strip()
                if not field_code:
                    self.stderr.write(self.style.WARNING(
                        f'  [SKIP] Line {line_no}: empty field_code, skipping'
                    ))
                    continue
                rows.append({
                    'field_code': field_code,
                    'meaning': meaning,
                    'data_type': data_type,
                })

        if not rows:
            self.stderr.write(self.style.ERROR('No valid rows found in TlsDB.csv'))
            return

        # ── Insert into tls_ref_data ─────────────────────────────────────────
        with connection.cursor() as cursor:
            with transaction.atomic():
                if clear:
                    cursor.execute('DELETE FROM tls_ref_data')
                    self.stdout.write(self.style.WARNING(f'  Cleared existing data ({len(rows)} rows to insert)'))

                inserted = 0
                updated = 0
                for r in rows:
                    cursor.execute(
                        """
                        INSERT INTO tls_ref_data (field_code, meaning, data_type)
                        VALUES (%s, %s, %s)
                        ON CONFLICT(field_code) DO UPDATE SET
                            meaning = EXCLUDED.meaning,
                            data_type = EXCLUDED.data_type
                        """,
                        [r['field_code'], r['meaning'], r['data_type']],
                    )
                    if cursor.rowcount == 1:
                        inserted += 1
                    else:
                        updated += 1

        self.stdout.write(self.style.SUCCESS(
            f'\n[OK] Imported {len(rows)} TLS field definitions from: {csv_path}'
        ))
        self.stdout.write(self.style.SUCCESS(
            f'      New: {inserted}  |  Updated: {updated}  |  Total: {len(rows)}'
        ))