#!/usr/bin/env python3
"""
Self-hosted email verification for campaign lists.

Three-step verification:
  1. Syntax check (regex)
  2. MX record lookup (domain has mail server?)
  3. SMTP RCPT TO handshake (mailbox exists?)

Usage:
    python3 -m scripts.workers.email_verifier --table fmcsa_carriers --limit 1000
    python3 -m scripts.workers.email_verifier --table fmcsa_carriers --dry-run
    python3 -m scripts.workers.email_verifier --email test@example.com  # single check

Results stored in email_verified (boolean) and email_verify_result (text) columns.
"""

from __future__ import annotations

import argparse
import dns.resolver
import logging
import os
import re
import smtplib
import socket
import sys
import time
from concurrent.futures import ThreadPoolExecutor, as_completed

import psycopg2

LOG = logging.getLogger("workers.email_verifier")
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(name)s] %(levelname)s %(message)s",
    stream=sys.stdout,
)

DATABASE_URL = os.environ.get("DATABASE_URL", "postgresql://pw:pw@localhost:5432/performancewest")
OUR_DOMAIN = "performancewest.net"
OUR_EMAIL = f"verify@{OUR_DOMAIN}"

# Regex for basic email validation
EMAIL_RE = re.compile(r"^[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}$")

# Domains known to accept all (catch-all) — can't verify individual addresses
CATCH_ALL_DOMAINS = {
    "gmail.com", "googlemail.com",
    "outlook.com", "hotmail.com", "live.com", "msn.com",
    "yahoo.com", "ymail.com", "aol.com",
    "icloud.com", "me.com", "mac.com",
    "protonmail.com", "proton.me",
}

# Cache MX lookups to avoid repeated DNS queries
_mx_cache: dict[str, list[str] | None] = {}


def get_mx_hosts(domain: str) -> list[str] | None:
    """Get MX hosts for a domain, cached."""
    if domain in _mx_cache:
        return _mx_cache[domain]

    try:
        answers = dns.resolver.resolve(domain, "MX")
        hosts = sorted(
            [(r.preference, str(r.exchange).rstrip(".")) for r in answers],
            key=lambda x: x[0],
        )
        result = [h[1] for h in hosts]
        _mx_cache[domain] = result
        return result
    except (dns.resolver.NoAnswer, dns.resolver.NXDOMAIN,
            dns.resolver.NoNameservers, dns.exception.Timeout):
        _mx_cache[domain] = None
        return None
    except Exception:
        _mx_cache[domain] = None
        return None


def verify_email(email: str) -> tuple[bool, str]:
    """
    Verify a single email address.

    Returns (is_valid, reason).
    """
    email = email.strip().lower()

    # Step 1: Syntax
    if not EMAIL_RE.match(email):
        return False, "invalid_syntax"

    domain = email.split("@")[1]

    # Step 2: MX lookup
    mx_hosts = get_mx_hosts(domain)
    if not mx_hosts:
        return False, "no_mx_records"

    # Step 3: Catch-all domains — can't verify, assume valid
    if domain in CATCH_ALL_DOMAINS:
        return True, "catch_all_domain"

    # Step 4: SMTP handshake
    for mx_host in mx_hosts[:2]:  # Try first 2 MX servers
        try:
            with smtplib.SMTP(timeout=10) as smtp:
                smtp.connect(mx_host, 25)
                smtp.helo(OUR_DOMAIN)
                code, _ = smtp.mail(OUR_EMAIL)
                if code != 250:
                    continue
                code, msg = smtp.rcpt(email)
                smtp.quit()

                if code == 250:
                    return True, "smtp_valid"
                elif code == 550 or code == 551 or code == 553:
                    return False, f"smtp_rejected_{code}"
                elif code == 452 or code == 421:
                    # Temp error — can't determine, assume valid
                    return True, "smtp_temp_error"
                else:
                    return True, f"smtp_unknown_{code}"

        except smtplib.SMTPServerDisconnected:
            continue
        except smtplib.SMTPConnectError:
            continue
        except socket.timeout:
            continue
        except ConnectionRefusedError:
            continue
        except OSError:
            continue
        except Exception as e:
            LOG.debug("SMTP error for %s via %s: %s", email, mx_host, e)
            continue

    # Couldn't connect to any MX — domain exists but server unreachable
    return True, "mx_unreachable"


def verify_table(table: str, limit: int | None = None, dry_run: bool = False) -> dict:
    """Verify emails in a database table."""
    conn = psycopg2.connect(DATABASE_URL)
    cur = conn.cursor()

    # Add columns if needed
    if not dry_run:
        for col in ["email_verified BOOLEAN", "email_verify_result TEXT"]:
            try:
                cur.execute(f"ALTER TABLE {table} ADD COLUMN IF NOT EXISTS {col}")
            except Exception:
                conn.rollback()
        conn.commit()

    # Get unverified emails
    limit_clause = f"LIMIT {limit}" if limit else ""
    cur.execute(f"""
        SELECT dot_number, email_address FROM {table}
        WHERE email_address IS NOT NULL
          AND email_address != ''
          AND (email_verified IS NULL)
        {limit_clause}
    """)

    rows = cur.fetchall()
    LOG.info("Found %d unverified emails to check", len(rows))

    stats = {"total": len(rows), "valid": 0, "invalid": 0, "catch_all": 0, "error": 0}

    # Verify in batches with threading (but not too aggressive)
    results = []

    def check_one(row):
        dot, email = row
        is_valid, reason = verify_email(email)
        return dot, email, is_valid, reason

    with ThreadPoolExecutor(max_workers=5) as executor:
        futures = {executor.submit(check_one, row): row for row in rows}
        done = 0
        for future in as_completed(futures):
            dot, email, is_valid, reason = future.result()
            results.append((is_valid, reason, dot))

            if is_valid:
                if reason == "catch_all_domain":
                    stats["catch_all"] += 1
                stats["valid"] += 1
            else:
                stats["invalid"] += 1

            done += 1
            if done % 500 == 0:
                LOG.info("  Verified %d / %d (valid: %d, invalid: %d)",
                         done, len(rows), stats["valid"], stats["invalid"])

    # Update database
    if not dry_run and results:
        LOG.info("Updating %d verification results...", len(results))
        for i in range(0, len(results), 1000):
            chunk = results[i:i+1000]
            for is_valid, reason, dot in chunk:
                cur.execute(f"""
                    UPDATE {table} SET
                        email_verified = %s,
                        email_verify_result = %s
                    WHERE dot_number = %s
                """, (is_valid, reason, dot))
            conn.commit()
            LOG.info("  Updated %d / %d", min(i + 1000, len(results)), len(results))

    conn.close()
    return stats


def main():
    parser = argparse.ArgumentParser(description="Verify email addresses")
    parser.add_argument("--table", default="fmcsa_carriers", help="Table to verify")
    parser.add_argument("--limit", type=int, default=None, help="Limit records")
    parser.add_argument("--dry-run", action="store_true", help="Check but don't save")
    parser.add_argument("--email", type=str, help="Verify a single email")
    args = parser.parse_args()

    if args.email:
        is_valid, reason = verify_email(args.email)
        print(f"{args.email}: {'VALID' if is_valid else 'INVALID'} ({reason})")
        return

    stats = verify_table(args.table, limit=args.limit, dry_run=args.dry_run)

    LOG.info("=== Verification Results ===")
    for k, v in stats.items():
        LOG.info("  %s: %s", k, v)

    if stats["total"] > 0:
        valid_pct = stats["valid"] / stats["total"] * 100
        LOG.info("  Valid rate: %.1f%%", valid_pct)


if __name__ == "__main__":
    main()