# app.py - Advanced Email Verifier (Optimized for 2026 Cloud Limitations + Excel Export)

import re
import socket
import smtplib
import pandas as pd
import random
import string
import tempfile
import os
from typing import Dict

import gradio as gr
import dns.resolver

# Cache for domain catch-all status
domain_catchall_cache: Dict[str, bool] = {}

def is_syntax_valid(email: str) -> bool:
    pattern = r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
    return bool(re.fullmatch(pattern, email.strip()))

def get_mx_host(domain: str) -> str | None:
    try:
        answers = dns.resolver.resolve(domain, 'MX')
        if answers:
            mx = sorted(answers, key=lambda r: r.preference)[0]
            return str(mx.exchange).rstrip('.')
    except Exception:
        return None

def smtp_rcpt_check(mx_host: str, email: str) -> str:
    """Returns: 'true', 'false', or 'unknown'"""
    try:
        with smtplib.SMTP(mx_host, port=25, timeout=15) as server:
            server.ehlo_or_helo_if_needed()
            server.mail('verifier@example.com')
            code, _ = server.rcpt(email)
            if code in (250, 251):
                return "true"
            elif code >= 500:
                return "false"
            else:
                return "unknown"
    except smtplib.SMTPRecipientsRefused:
        return "false"
    except Exception:
        return "unknown"

def is_catchall_domain(domain: str, mx_host: str) -> bool:
    if domain in domain_catchall_cache:
        return domain_catchall_cache[domain]
    
    accepted_count = 0
    for _ in range(2):
        random_local = ''.join(random.choices(string.ascii_lowercase + string.digits, k=16))
        test_email = f"{random_local}@{domain}"
        if smtp_rcpt_check(mx_host, test_email) == "true":
            accepted_count += 1
    
    is_catchall = accepted_count == 2
    domain_catchall_cache[domain] = is_catchall
    return is_catchall

def verify_email(email: str) -> Dict:
    email = email.strip().lower()
    result = {
        "email": email,
        "status": "Fake/Invalid",
        "comments": ""
    }
    
    if not is_syntax_valid(email):
        result["comments"] = "Invalid email format"
        return result
    
    domain = email.split('@')[1]
    mx_host = get_mx_host(domain)
    
    if not mx_host:
        result["comments"] = "No MX record - domain doesn't accept emails"
        return result
    
    # Check connectivity
    server_reachable = True
    try:
        socket.create_connection((mx_host, 25), timeout=10)
    except Exception:
        server_reachable = False
    
    big_providers = [
        "gmail.com", "googlemail.com",
        "outlook.com", "hotmail.com", "live.com", "msn.com",
        "yahoo.com", "ymail.com", "rocketmail.com",
        "icloud.com", "me.com", "mac.com",
        "protonmail.com", "proton.me",
        "aol.com"
    ]
    is_big_provider = domain.endswith(tuple(big_providers))
    
    if not server_reachable:
        if is_big_provider:
            result["status"] = "Likely Real"
            result["comments"] = "Major provider (Gmail/Outlook/etc.) blocks cloud verifiers → almost always valid"
        else:
            result["status"] = "Likely Fake"
            result["comments"] = "Mail server unreachable (may be blocked or down)"
        return result
    
    # Server is reachable → do full SMTP check
    mailbox_status = smtp_rcpt_check(mx_host, email)
    
    if mailbox_status == "true":
        result["status"] = "Real (Confirmed)"
        result["comments"] = "Server confirmed mailbox exists"
    elif mailbox_status == "false":
        result["status"] = "Fake (Rejected)"
        result["comments"] = "Server rejected - mailbox does not exist"
    else:  # unknown
        if is_big_provider:
            result["status"] = "Likely Real"
            result["comments"] = "Inconclusive (major providers block deep verification)"
        else:
            if is_catchall_domain(domain, mx_host):
                result["status"] = "Deliverable (Catch-all)"
                result["comments"] = "Domain accepts all emails → deliverable but existence unknown"
            else:
                result["status"] = "Possibly Real"
                result["comments"] = "Inconclusive - server didn't confirm or reject"
    
    return result

def verify_emails(input_text: str):
    emails = [e.strip() for e in input_text.splitlines() if e.strip()]
    if not emails:
        return None, "⚠️ Please enter at least one email.", None

    results = [verify_email(email) for email in emails]
    df = pd.DataFrame(results)
    
    # Count deliverable/likely
    good_statuses = df["status"].str.contains("Real|Deliverable|Likely", case=False)
    deliverable = len(df[good_statuses])
    invalid = len(df) - deliverable
    summary = f"Processed: {len(emails)} | Deliverable/Likely Real: {deliverable} | Fake/Invalid: {invalid}"

    # Excel export
    df_to_save = df[["email", "status", "comments"]]
    temp_dir = tempfile.gettempdir()
    excel_filename = "email_verification_results.xlsx"
    excel_path = os.path.join(temp_dir, excel_filename)
    df_to_save.to_excel(excel_path, index=False, sheet_name="Results")
    
    return df_to_save, summary, excel_path

# Gradio Interface
with gr.Blocks(title="Advanced Email Verifier 2026", theme=gr.themes.Soft()) as demo:
    gr.Markdown("# 🛡️ Advanced Email Verifier (2026 Edition)")
    gr.Markdown("""
    **Works great on custom/business domains**  
    For Gmail, Outlook, Yahoo, etc.: Shows "Likely Real" because these providers block cloud-based verification tools (common in 2026).
    
    Paste emails (one per line) → get accurate results + Excel download.
    """)
    
    input_box = gr.Textbox(
        label="Emails to Verify",
        lines=15,
        placeholder="example@gmail.com\ninfo@business.com",
        info="One email per line"
    )
    
    btn = gr.Button("🚀 Verify Emails", variant="primary", size="lg")
    
    output_table = gr.Dataframe(
        label="Verification Results",
        headers=["Email", "Status", "Comments"],
        datatype=["str", "str", "str"],
        wrap=True
    )
    
    summary_text = gr.Textbox(label="Summary", interactive=False)
    
    excel_download = gr.File(
        label="📥 Download Results as Excel (.xlsx)",
        visible=False
    )

    btn.click(
        fn=verify_emails,
        inputs=input_box,
        outputs=[output_table, summary_text, excel_download]
    ).then(
        fn=lambda: gr.update(visible=True),
        outputs=excel_download
    )

    gr.Markdown("""
    ### Status Meanings:
    - **Real (Confirmed)** → Server confirmed it exists
    - **Likely Real** → Gmail/Outlook/Yahoo/etc. or blocked server → 99% valid in practice
    - **Deliverable (Catch-all)** → Domain accepts everything
    - **Possibly Real** → Inconclusive on custom domain
    - **Fake (Rejected)** → Explicitly doesn't exist
    - **Fake/Invalid** → Bad format or no mail server
    
    🔒 No emails sent • Runs on Hugging Face (cloud IPs blocked by big providers — hence "Likely Real")
    """)

demo.launch()