import os
import re
import csv
import secrets
import unicodedata
from datetime import datetime, timedelta
from io import BytesIO

from flask import (
    Flask,
    render_template,
    request,
    redirect,
    url_for,
    send_file,
    flash,
    session,
    abort,
)
from flask_sqlalchemy import SQLAlchemy
from flask_login import (
    LoginManager,
    UserMixin,
    login_user,
    login_required,
    current_user,
    logout_user,
)
from werkzeug.security import generate_password_hash, check_password_hash
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter

from sendgrid import SendGridAPIClient
from sendgrid.helpers.mail import Mail

# your HF-based classifier
from model import classify_tone_rich


# =========================================================
# APP CONFIG
# =========================================================

app = Flask(__name__)

app.config["SECRET_KEY"] = os.getenv("SECRET_KEY", "change-this-in-prod")
app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///data.db"
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False

# Detect if running on Hugging Face Spaces (they set SPACE_ID)
IS_HF = os.getenv("SPACE_ID") is not None

# cookie security
app.config["SESSION_COOKIE_HTTPONLY"] = True

if IS_HF:
    # Needed because app runs inside an iframe on huggingface.co
    app.config["SESSION_COOKIE_SAMESITE"] = "None"
    app.config["SESSION_COOKIE_SECURE"] = True
else:
    # Local dev / normal hosting
    app.config["SESSION_COOKIE_SAMESITE"] = "Lax"
    app.config["SESSION_COOKIE_SECURE"] = False

db = SQLAlchemy(app)
login_manager = LoginManager(app)
login_manager.login_view = "login"

# Email (SendGrid)
SENDGRID_API_KEY = os.getenv("SENDGRID_API_KEY")
SENDER_EMAIL = os.getenv("SENDER_EMAIL", "no-reply@example.com")

# simple email regex
EMAIL_RE = re.compile(r"^[^@\s]+@[^@\s]+\.[^@\s]+$")

os.makedirs("exports", exist_ok=True)


# =========================================================
# HELPER FUNCTIONS – SANITIZATION, CSRF, PASSWORDS
# =========================================================

def normalize_text(value: str) -> str:
    if not value:
        return ""
    value = unicodedata.normalize("NFKC", value)
    value = value.replace("\u200b", "").replace("\u200c", "").replace("\u200d", "")
    return value.strip()


def sanitize_string(value: str, max_len: int = 255) -> str:
    value = normalize_text(value)
    if len(value) > max_len:
        value = value[:max_len]
    return value


def sanitize_long_text(value: str, max_len: int = 4000) -> str:
    value = normalize_text(value)
    if len(value) > max_len:
        value = value[:max_len]
    return value


def is_valid_email(email: str) -> bool:
    return bool(email and EMAIL_RE.match(email))


def is_strong_password(pw: str) -> bool:
    if not pw or len(pw) < 8:
        return False
    has_letter = any(c.isalpha() for c in pw)
    has_digit = any(c.isdigit() for c in pw)
    return has_letter and has_digit


def generate_code() -> str:
    """6-digit numeric code used for verify + reset."""
    return f"{secrets.randbelow(1000000):06d}"


def generate_csrf_token() -> str:
    token = session.get("csrf_token")
    if not token:
        token = secrets.token_hex(16)
        session["csrf_token"] = token
    return token


@app.before_request
def csrf_protect():
    # ensure CSRF token exists
    generate_csrf_token()

    if request.method == "POST":
        form_token = request.form.get("csrf_token", "")
        sess_token = session.get("csrf_token", "")
        if not form_token or form_token != sess_token:
            abort(400, description="Invalid CSRF token")


@app.context_processor
def inject_csrf():
    return {"csrf_token": session.get("csrf_token", "")}


# =========================================================
# MODELS
# =========================================================

class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(255), unique=True, nullable=False)
    password_hash = db.Column(db.String(255), nullable=False)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)

    # login security
    failed_logins = db.Column(db.Integer, default=0)
    lock_until = db.Column(db.DateTime, nullable=True)

    # email verification
    is_verified = db.Column(db.Boolean, default=False)
    verification_code = db.Column(db.String(6), nullable=True)
    verification_expires = db.Column(db.DateTime, nullable=True)

    # password reset
    reset_code = db.Column(db.String(6), nullable=True)
    reset_expires = db.Column(db.DateTime, nullable=True)

    # activity (for possible retention rules)
    last_active_at = db.Column(db.DateTime, nullable=True)


class Entry(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    text = db.Column(db.Text, nullable=False)
    label = db.Column(db.String(32))
    confidence = db.Column(db.Float)
    severity = db.Column(db.Integer)
    threat_score = db.Column(db.Integer)
    politeness_score = db.Column(db.Integer)
    friendly_score = db.Column(db.Integer)
    has_threat = db.Column(db.Boolean, default=False)
    has_profanity = db.Column(db.Boolean, default=False)
    has_sarcasm = db.Column(db.Boolean, default=False)
    user_id = db.Column(db.Integer, db.ForeignKey("user.id"), nullable=False)

    user = db.relationship("User", backref="entries")


@login_manager.user_loader
def load_user(user_id):
    try:
        return User.query.get(int(user_id))
    except Exception:
        return None


# =========================================================
# EMAIL HELPERS
# =========================================================

def send_email(to_email: str, subject: str, html: str):
    if not SENDGRID_API_KEY:
        print("[WARN] SENDGRID_API_KEY not set. Skipping email send.")
        print(f"Subject: {subject}\nTo: {to_email}\n{html}")
        return

    message = Mail(
        from_email=SENDER_EMAIL,
        to_emails=to_email,
        subject=subject,
        html_content=html,
    )
    try:
        sg = SendGridAPIClient(SENDGRID_API_KEY)
        sg.send(message)
        print(f"[INFO] Sent email to {to_email}: {subject}")
    except Exception as e:
        print(f"[ERROR] Failed to send email to {to_email}: {e}")


def send_verification_email(to_email: str, code: str):
    html = f"""
    <p>Thanks for signing up for the AI Email Tone Classifier.</p>
    <p>Your verification code is: <strong>{code}</strong></p>
    <p>This code will expire in 15 minutes.</p>
    """
    send_email(to_email, "Verify your email", html)


def send_password_reset_email(to_email: str, code: str):
    html = f"""
    <p>You requested to reset your password for the AI Email Tone Classifier.</p>
    <p>Your password reset code is: <strong>{code}</strong></p>
    <p>This code will expire in 15 minutes.</p>
    <p>If you did not request this, you can ignore this email.</p>
    """
    send_email(to_email, "Password reset code", html)


# =========================================================
# AUTH ROUTES: REGISTER / LOGIN / LOGOUT / VERIFY
# =========================================================

@app.route("/register", methods=["GET", "POST"])
def register():
    if current_user.is_authenticated:
        return redirect(url_for("index"))

    if request.method == "POST":
        email = sanitize_string(request.form.get("email", ""), 255).lower()
        password = normalize_text(request.form.get("password", ""))
        consent = request.form.get("consent_privacy") == "on"

        if not email or not password:
            flash("Email and password are required.", "error")
            return redirect(url_for("register"))

        if not is_valid_email(email):
            flash("Please enter a valid email address.", "error")
            return redirect(url_for("register"))

        if not is_strong_password(password):
            flash("Password must be at least 8 characters and contain letters and numbers.", "error")
            return redirect(url_for("register"))

        if not consent:
            flash("You must agree to the Privacy Policy to create an account.", "error")
            return redirect(url_for("register"))

        existing = User.query.filter_by(email=email).first()
        if existing:
            flash("An account with that email already exists.", "error")
            return redirect(url_for("register"))

        user = User(
            email=email,
            password_hash=generate_password_hash(password),
            last_active_at=datetime.utcnow(),
        )

        code = generate_code()
        user.verification_code = code
        user.verification_expires = datetime.utcnow() + timedelta(minutes=15)
        user.is_verified = False

        db.session.add(user)
        db.session.commit()

        send_verification_email(email, code)
        session["pending_email"] = email

        flash("Account created. Check your email for the verification code.", "success")
        return redirect(url_for("verify"))

    return render_template("login.html", mode="register", title="Register")


@app.route("/login", methods=["GET", "POST"])
def login():
    if current_user.is_authenticated:
        return redirect(url_for("index"))

    if request.method == "POST":
        email = sanitize_string(request.form.get("email", ""), 255).lower()
        password = normalize_text(request.form.get("password", ""))

        if not email or not password:
            flash("Email and password are required.", "error")
            return redirect(url_for("login"))

        user = User.query.filter_by(email=email).first()
        if not user:
            flash("Invalid email or password.", "error")
            return redirect(url_for("login"))

        now = datetime.utcnow()

        # lockout check
        if user.lock_until and user.lock_until > now:
            remaining = int((user.lock_until - now).total_seconds() // 60) + 1
            flash(f"Account locked due to too many failed attempts. Try again in ~{remaining} minutes.", "error")
            return redirect(url_for("login"))

        if not check_password_hash(user.password_hash, password):
            user.failed_logins = (user.failed_logins or 0) + 1
            if user.failed_logins >= 5:
                user.lock_until = now + timedelta(minutes=10)
                user.failed_logins = 0
            db.session.commit()
            flash("Invalid email or password.", "error")
            return redirect(url_for("login"))

        # reset counters
        user.failed_logins = 0
        user.lock_until = None
        user.last_active_at = now
        db.session.commit()

        if not user.is_verified:
            session["pending_email"] = user.email
            flash("Please verify your email before logging in.", "error")
            return redirect(url_for("verify"))

        login_user(user)
        flash("Logged in successfully.", "success")
        return redirect(url_for("index"))

    return render_template("login.html", mode="login", title="Login")


@app.route("/logout")
@login_required
def logout():
    logout_user()
    flash("You have been logged out.", "success")
    return redirect(url_for("login"))


@app.route("/verify", methods=["GET", "POST"])
def verify():
    email = sanitize_string(
        request.args.get("email", "") or session.get("pending_email", ""), 255
    ).lower()

    if not email:
        flash("No email specified for verification. Please register or log in again.", "error")
        return redirect(url_for("register"))

    user = User.query.filter_by(email=email).first()
    if not user:
        flash("Account not found. Please register again.", "error")
        return redirect(url_for("register"))

    if user.is_verified:
        flash("Your email is already verified. You can log in.", "success")
        return redirect(url_for("login"))

    if request.method == "POST":
        action = request.form.get("action", "verify")

        if action == "resend":
            code = generate_code()
            user.verification_code = code
            user.verification_expires = datetime.utcnow() + timedelta(minutes=15)
            db.session.commit()
            send_verification_email(user.email, code)
            flash("A new verification code has been sent.", "success")
            return redirect(url_for("verify", email=user.email))

        code_input = sanitize_string(request.form.get("code", ""), 6)

        if not code_input:
            flash("Please enter the verification code.", "error")
            return redirect(url_for("verify", email=user.email))

        if not user.verification_code or not user.verification_expires:
            flash("No active verification code. Please resend.", "error")
            return redirect(url_for("verify", email=user.email))

        if datetime.utcnow() > user.verification_expires:
            flash("Verification code expired. Please request a new one.", "error")
            return redirect(url_for("verify", email=user.email))

        if code_input != user.verification_code:
            flash("Invalid verification code.", "error")
            return redirect(url_for("verify", email=user.email))

        user.is_verified = True
        user.verification_code = None
        user.verification_expires = None
        user.last_active_at = datetime.utcnow()
        db.session.commit()

        flash("Email verified successfully. You can now log in.", "success")
        return redirect(url_for("login"))

    session["pending_email"] = email
    return render_template("verify.html", email=email, title="Verify Email")


# =========================================================
# FORGOT PASSWORD + RESET
# =========================================================

@app.route("/forgot", methods=["GET", "POST"])
def forgot_password():
    if request.method == "POST":
        email = sanitize_string(request.form.get("email", ""), 255).lower()

        if not is_valid_email(email):
            flash("If that email exists, a reset code has been sent. Check your email, then enter the code below.", "success")
            return redirect(url_for("reset_password"))

        user = User.query.filter_by(email=email).first()
        if user:
            code = generate_code()
            user.reset_code = code
            user.reset_expires = datetime.utcnow() + timedelta(minutes=15)
            db.session.commit()
            send_password_reset_email(user.email, code)

        flash("If that email exists, a reset code has been sent. Check your email, then enter the code below.", "success")
        return redirect(url_for("reset_password"))

    return render_template("forgot.html", title="Forgot Password")


@app.route("/reset", methods=["GET", "POST"])
def reset_password():
    if request.method == "POST":
        email = sanitize_string(request.form.get("email", ""), 255).lower()
        code_input = sanitize_string(request.form.get("code", ""), 6)
        new_pw = normalize_text(request.form.get("password", ""))
        confirm_pw = normalize_text(request.form.get("confirm_password", ""))

        if not email or not code_input or not new_pw or not confirm_pw:
            flash("All fields are required.", "error")
            return redirect(url_for("reset_password"))

        if new_pw != confirm_pw:
            flash("Passwords do not match.", "error")
            return redirect(url_for("reset_password"))

        if not is_strong_password(new_pw):
            flash("Password must be at least 8 characters and contain letters and numbers.", "error")
            return redirect(url_for("reset_password"))

        user = User.query.filter_by(email=email).first()
        if (
            not user
            or not user.reset_code
            or not user.reset_expires
            or datetime.utcnow() > user.reset_expires
            or code_input != user.reset_code
        ):
            flash("Invalid or expired reset code.", "error")
            return redirect(url_for("reset_password"))

        user.password_hash = generate_password_hash(new_pw)
        user.reset_code = None
        user.reset_expires = None
        db.session.commit()

        flash("Password reset successfully. You can now log in.", "success")
        return redirect(url_for("login"))

    return render_template("reset_password.html", title="Reset Password")


# =========================================================
# MAIN CLASSIFIER
# =========================================================

@app.route("/", methods=["GET", "POST"])
@login_required
def index():
    if not current_user.is_verified:
        flash("Please verify your email to use the classifier.", "error")
        return redirect(url_for("verify", email=current_user.email))

    result = None    # dict from classify_tone_rich
    text = ""

    if request.method == "POST":
        text = sanitize_long_text(request.form.get("email_text", ""))
        if text:
            result = classify_tone_rich(text)

            entry = Entry(
                text=text,
                label=result["label"],
                confidence=float(result["confidence"]),
                severity=int(result["severity"]),
                threat_score=int(result["threat_score"]),
                politeness_score=int(result["politeness_score"]),
                friendly_score=int(result["friendly_score"]),
                has_threat=bool(result["has_threat"]),
                has_profanity=bool(result["has_profanity"]),
                has_sarcasm=bool(result["has_sarcasm"]),
                user_id=current_user.id,
            )
            db.session.add(entry)
            db.session.commit()

    return render_template(
        "index.html",
        title="Analyze Email",
        email_text=text,
        result=result,
    )


# =========================================================
# HISTORY + EXPORTS
# =========================================================

@app.route("/history")
@login_required
def history_view():
    if not current_user.is_verified:
        flash("Please verify your email to view history.", "error")
        return redirect(url_for("verify", email=current_user.email))

    q = sanitize_string(request.args.get("q", ""), 255).lower()
    filter_label = sanitize_string(request.args.get("label", ""), 32).lower()

    query = Entry.query.filter_by(user_id=current_user.id)

    if q:
        query = query.filter(Entry.text.ilike(f"%{q}%"))

    if filter_label:
        query = query.filter(Entry.label.ilike(filter_label))

    entries = query.order_by(Entry.created_at.desc()).all()

    return render_template(
        "history.html",
        title="History",
        history=entries,
        search=q,
        active_filter=filter_label,
    )


@app.route("/export/csv")
@login_required
def export_csv():
    if not current_user.is_verified:
        flash("Please verify your email to export data.", "error")
        return redirect(url_for("verify", email=current_user.email))

    filepath = os.path.join("exports", f"history_{current_user.id}.csv")
    entries = Entry.query.filter_by(user_id=current_user.id).order_by(Entry.created_at.asc())

    with open(filepath, "w", newline="", encoding="utf-8") as f:
        writer = csv.writer(f)
        writer.writerow(
            [
                "Time UTC",
                "Label",
                "Confidence",
                "Severity",
                "ThreatScore",
                "PolitenessScore",
                "FriendlyScore",
                "HasThreat",
                "HasProfanity",
                "HasSarcasm",
                "Text",
            ]
        )
        for e in entries:
            writer.writerow(
                [
                    e.created_at.isoformat(),
                    e.label,
                    f"{e.confidence:.1f}",
                    e.severity,
                    e.threat_score,
                    e.politeness_score,
                    e.friendly_score,
                    int(e.has_threat),
                    int(e.has_profanity),
                    int(e.has_sarcasm),
                    e.text,
                ]
            )

    return send_file(filepath, as_attachment=True)


@app.route("/export/pdf")
@login_required
def export_pdf():
    if not current_user.is_verified:
        flash("Please verify your email to export data.", "error")
        return redirect(url_for("verify", email=current_user.email))

    buffer = BytesIO()
    c = canvas.Canvas(buffer, pagesize=letter)
    width, height = letter

    c.setFillColorRGB(0.12, 0.15, 0.20)
    c.rect(0, height - 60, width, 60, fill=1)
    c.setFillColorRGB(1, 1, 1)
    c.setFont("Helvetica-Bold", 18)
    c.drawString(40, height - 35, "Tone Classifier – History Report")

    entries = (
        Entry.query.filter_by(user_id=current_user.id)
        .order_by(Entry.created_at.desc())
        .all()
    )

    y = height - 80
    for e in entries:
        if y < 90:
            c.showPage()
            y = height - 60

        c.setFont("Helvetica-Bold", 10)
        c.setFillColorRGB(0, 0, 0)
        c.drawString(
            40,
            y,
            f"{e.created_at.isoformat()} | {e.label} | Severity {e.severity}",
        )
        y -= 12

        meta = f"Threat:{e.threat_score}  Polite:{e.politeness_score}  Friendly:{e.friendly_score}"
        c.setFont("Helvetica", 9)
        c.drawString(40, y, meta)
        y -= 12

        text = e.text
        while len(text) > 90:
            idx = text.rfind(" ", 0, 90)
            if idx == -1:
                idx = 90
            c.drawString(50, y, text[:idx])
            text = text[idx:].strip()
            y -= 11

        c.drawString(50, y, text)
        y -= 20

    c.showPage()
    c.save()

    buffer.seek(0)
    filepath = os.path.join("exports", f"history_{current_user.id}.pdf")
    with open(filepath, "wb") as f:
        f.write(buffer.getvalue())

    return send_file(filepath, as_attachment=True)


@app.route("/history/clear", methods=["POST"])
@login_required
def clear_history():
    if not current_user.is_verified:
        flash("Please verify your email to clear history.", "error")
        return redirect(url_for("verify", email=current_user.email))

    Entry.query.filter_by(user_id=current_user.id).delete()
    db.session.commit()
    flash("History cleared.", "success")
    return redirect(url_for("history_view"))


# =========================================================
# DELETE ACCOUNT + GDPR PAGES
# =========================================================

@app.route("/account/delete", methods=["GET", "POST"])
@login_required
def delete_account():
    if request.method == "POST":
        password = normalize_text(request.form.get("password", ""))

        if not check_password_hash(current_user.password_hash, password):
            flash("Incorrect password. Account not deleted.", "error")
            return redirect(url_for("delete_account"))

        try:
            uid = current_user.id
            Entry.query.filter_by(user_id=uid).delete()
            user = User.query.get(uid)
            logout_user()
            db.session.delete(user)
            db.session.commit()
            flash("Your account and all data have been deleted.", "success")
        except Exception as e:
            db.session.rollback()
            flash("Error deleting account. Please try again.", "error")
            print(f"[ERROR] delete_account failed: {e}")
            return redirect(url_for("delete_account"))

        return redirect(url_for("register"))

    return render_template("delete_account.html", title="Delete Account")


@app.route("/privacy")
def privacy():
    from datetime import datetime as dt
    return render_template("privacy.html", title="Privacy Policy", datetime=dt)


@app.route("/do-not-sell")
def do_not_sell():
    return render_template("do_not_sell.html", title="Do Not Sell My Info")


# =========================================================
# INIT DB & RUN (LOCAL)
# =========================================================

with app.app_context():
    db.create_all()

if __name__ == "__main__":
    # local dev
    app.run(debug=True, host="0.0.0.0", port=7860)