import os
import secrets
import smtplib
import logging
from pathlib import Path
from random import SystemRandom
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

from flask import Flask, request, jsonify, render_template

logging.basicConfig(level=logging.INFO, format="%(levelname)s %(message)s")
logger = logging.getLogger(__name__)

app = Flask(__name__)
app.secret_key = secrets.token_hex(32)

WORDS_DIR = Path(__file__).parent / "words"

def _load(path: Path) -> list[str]:
    words = [w.strip() for w in path.read_text().splitlines() if w.strip()]
    if not words:
        raise RuntimeError(f"Word list is empty: {path}")
    return words

ADJECTIVES = _load(WORDS_DIR / "Positive-Adjective-List.txt")
ANIMALS    = _load(WORDS_DIR / "animals.txt")
_rng       = SystemRandom()


def generate_pseudonym() -> str:
    return f"{_rng.choice(ADJECTIVES)} {_rng.choice(ANIMALS)}"


def send_pseudonym_emails(
    *,
    sender_email: str,
    app_password: str,
    teacher_email: str,
    student_email: str,
    student_name: str,
    pseudonym: str,
) -> None:
    """Send notification emails via SMTP.  Credentials live only in this
    function's local scope and are never written to disk or logged."""

    subject = "Pseudonym Generation / Генерация псевдонима"

    teacher_body = (
        f"Здравствуйте!\n\n"
        f"Студенту {student_name} был назначен псевдоним: {pseudonym}.\n\n"
        f"Это автоматическое уведомление. Хорошего дня!\n\n"
        f"---\n"
        f"Hello!\n\n"
        f"Student {student_name} has been assigned the pseudonym: {pseudonym}.\n\n"
        f"This is an automated notification. Have a great day!"
    )

    student_body = (
        f"Здравствуйте, {student_name}!\n\n"
        f"Вам был присвоен псевдоним: {pseudonym}.\n"
        f"Можете использовать его при получении своей оценки! \n\n"
        f"---\n"
        f"Hello, {student_name}!\n\n"
        f"You have been assigned the pseudonym: {pseudonym}.\n"
        f"Please use it when submitting your work.\n\n"
        f"This is an automated notification."
    )

    def _build(to_addr: str, body: str) -> MIMEMultipart:
        msg = MIMEMultipart()
        msg["Subject"] = subject
        msg["From"]    = sender_email
        msg["To"]      = to_addr
        msg.attach(MIMEText(body, "plain", "utf-8"))
        return msg

    with smtplib.SMTP("smtp.gmail.com", 587) as smtp:
        smtp.ehlo()
        smtp.starttls()
        smtp.login(sender_email, app_password)
        smtp.sendmail(sender_email, teacher_email, _build(teacher_email, teacher_body).as_string())
        smtp.sendmail(sender_email, student_email, _build(student_email, student_body).as_string())

@app.route("/")
def index():
    return render_template("index.html")

@app.route("/send", methods=["POST"])
def send():
    data = request.get_json(silent=True) or {}

    sender_email   = (data.get("sender_email")   or "").strip()
    app_password   = (data.get("app_password")   or "").strip()
    teacher_email  = (data.get("teacher_email")  or "").strip()
    student_email  = (data.get("student_email")  or "").strip()
    student_name   = (data.get("student_name")   or "").strip()

    errors = []
    for field, value in [
        ("sender_email",  sender_email),
        ("app_password",  app_password),
        ("teacher_email", teacher_email),
        ("student_email", student_email),
        ("student_name",  student_name),
    ]:
        if not value:
            errors.append(f"{field} is required")
    if errors:
        return jsonify({"ok": False, "error": "; ".join(errors)}), 400

    pseudonym = generate_pseudonym()

    try:
        send_pseudonym_emails(
            sender_email  = sender_email,
            app_password  = app_password,
            teacher_email = teacher_email,
            student_email = student_email,
            student_name  = student_name,
            pseudonym     = pseudonym,
        )
    except smtplib.SMTPAuthenticationError:
        logger.warning("SMTP auth failed for sender (address redacted)")
        return jsonify({"ok": False, "error": "Authentication failed. Check your sender email and app password."}), 401
    except smtplib.SMTPRecipientsRefused as exc:
        logger.warning("Recipient refused: %s", list(exc.recipients))
        return jsonify({"ok": False, "error": "One or more recipient addresses were refused."}), 400
    except Exception as exc:          # noqa: BLE001
        logger.exception("Unexpected SMTP error")
        return jsonify({"ok": False, "error": f"Could not send email: {exc}"}), 500
    finally:
        app_password  = None   # noqa: F841
        sender_email  = None   # noqa: F841

    logger.info("Pseudonym '%s' dispatched!", pseudonym)
    return jsonify({"ok": True, "pseudonym": pseudonym})


if __name__ == "__main__":
    port = int(os.environ.get("PORT", 7860))
    app.run(host="0.0.0.0", port=port, debug=False)