"""Read-only sender candidates for mail triage; never chooses between companies."""
from email.utils import parseaddr


def find_sender_candidates(sender, query, ignored_domains=()):
    address = parseaddr(str(sender or ''))[1].strip().lower()
    domain = address.rsplit('@', 1)[1] if '@' in address else ''
    if not domain:
        return {'address': address, 'domain': domain, 'candidates': [], 'ambiguous': False}
    rows = query("""
        SELECT c.id, c.name, 'customer' AS kind, 'contact_email' AS source,
               ct.id AS contact_id, CONCAT_WS(' ', ct.first_name, ct.last_name) AS contact_name
        FROM contacts ct
        JOIN contact_companies cc ON cc.contact_id = ct.id
        JOIN customers c ON c.id = cc.customer_id
        WHERE ct.is_active = true AND c.is_active = true
          AND LOWER(TRIM(ct.email)) = %s
        UNION ALL
        SELECT v.id, v.name, 'vendor', 'contact_email', ct.id,
               CONCAT_WS(' ', ct.first_name, ct.last_name)
        FROM contacts ct
        JOIN vendor_contacts vc ON vc.contact_id = ct.id
        JOIN vendors v ON v.id = vc.vendor_id
        WHERE ct.is_active = true AND v.is_active = true
          AND LOWER(TRIM(ct.email)) = %s
        UNION ALL
        SELECT id, name, 'customer', 'exact_email', NULL, NULL FROM customers
        WHERE is_active = true AND LOWER(TRIM(email)) = %s
        UNION ALL
        SELECT id, name, 'vendor', 'exact_email', NULL, NULL FROM vendors
        WHERE is_active = true AND LOWER(TRIM(email)) = %s
    """, (address, address, address, address)) or []
    if domain not in ignored_domains and 'bmc' not in domain:
        rows += query("""
            SELECT c.id, c.name, 'customer' AS kind, 'saved_domain' AS source,
                   NULL AS contact_id, NULL AS contact_name
            FROM email_domain_customer_mappings m JOIN customers c ON c.id = m.customer_id
            WHERE c.is_active = true AND LOWER(TRIM(m.domain)) = %s
            UNION ALL
            SELECT id, name, 'customer', 'exact_domain', NULL, NULL FROM customers
            WHERE is_active = true AND LOWER(TRIM(email_domain)) IN (%s, %s)
            UNION ALL
            SELECT v.id, v.name, 'vendor', 'exact_domain', NULL, NULL
            FROM vendors v JOIN vendor_email_domains d ON d.vendor_id = v.id
            WHERE v.is_active = true AND LOWER(TRIM(d.domain)) = %s
        """, (domain, domain, 'www.' + domain, domain)) or []
    candidates = {}
    priority = {'contact_email': 0, 'exact_email': 1, 'saved_domain': 2, 'exact_domain': 3}
    for row in sorted(rows, key=lambda row: (priority[row['source']], row['name'].lower(), row['id'])):
        key = (row['kind'], row['id'])
        if key not in candidates:
            candidates[key] = dict(row)
    values = list(candidates.values())
    return {'address': address, 'domain': domain, 'candidates': values,
            'ambiguous': len(values) > 1}