import os
import re
import uuid
import pytz
import psycopg2
import requests
import gradio as gr
import json
import pickle
import base64

from google.auth.transport.requests import Request
from googleapiclient.discovery import build
from google.oauth2.credentials import Credentials

from email.mime.text import MIMEText
from datetime import datetime, date
from dotenv import load_dotenv


# ================= LOAD ENV =================

load_dotenv()

DB_URL = os.getenv("DB_URL")
GMAIL_USER = os.getenv("GMAIL_USER")
CRON_SECRET = os.getenv("CRON")
HF_URL = os.getenv("HF_URL")

LEETCODE_API = "https://leetcode-api-vercel.vercel.app"

SCOPES = ["https://www.googleapis.com/auth/gmail.send"]
TOKEN_FILE = "token.pkl"


# ================= DB =================

def get_db():
    return psycopg2.connect(DB_URL, sslmode="require")


# ================= GMAIL =================

def get_gmail_service():

    creds = None

    if os.path.exists(TOKEN_FILE):
        try:
            with open(TOKEN_FILE, "rb") as f:
                creds = pickle.load(f)
        except:
            creds = None

    if creds and creds.expired and creds.refresh_token:
        try:
            creds.refresh(Request())

            with open(TOKEN_FILE, "wb") as f:
                pickle.dump(creds, f)

        except:
            creds = None

    if not creds:
        raise Exception("❌ token.pkl missing. Upload valid token.")

    return build("gmail", "v1", credentials=creds)


def send_email(to, subject, html):

    try:
        service = get_gmail_service()

        msg = MIMEText(html, "html")
        msg["To"] = to
        msg["From"] = GMAIL_USER
        msg["Subject"] = subject

        raw = base64.urlsafe_b64encode(
            msg.as_bytes()
        ).decode()

        body = {"raw": raw}

        service.users().messages().send(
            userId="me",
            body=body
        ).execute()

        print("✅ Sent:", to)
        return True

    except Exception as e:
        print("❌ Gmail error:", e)
        return False


def create_email_template(title, content, unsubscribe_link, email_type="reminder", problem_link=None, difficulty=None):
    """Create a beautiful HTML email template"""
    
    # Color scheme based on email type
    colors = {
        "morning": {"primary": "#4CAF50", "secondary": "#81C784", "bg": "#E8F5E8"},
        "afternoon": {"primary": "#FF9800", "secondary": "#FFB74D", "bg": "#FFF3E0"},
        "night": {"primary": "#F44336", "secondary": "#EF5350", "bg": "#FFEBEE"},
        "verification": {"primary": "#2196F3", "secondary": "#64B5F6", "bg": "#E3F2FD"}
    }
    
    color = colors.get(email_type, colors["morning"])
    
    # Difficulty badge colors
    difficulty_colors = {
        "Easy": "#00B04F",
        "Medium": "#FFA116", 
        "Hard": "#FF375F"
    }
    
    # Handle special cases for verification emails
    if email_type == "verification":
        problem_button = f"""
        <div style="text-align: center; margin: 30px 0;">
            <a href="{unsubscribe_link}" 
               style="display: inline-block; background: linear-gradient(135deg, {color['primary']}, {color['secondary']}); 
                      color: white; padding: 15px 30px; text-decoration: none; border-radius: 25px; 
                      font-weight: bold; font-size: 16px; box-shadow: 0 4px 15px rgba(0,0,0,0.2); 
                      transition: transform 0.2s;">
                ✅ Verify Email
            </a>
        </div>
        """
        tips_section = ""
        motivation_section = ""
        difficulty_badge = ""
    else:
        # Use provided problem_link or construct from title
        if problem_link:
            link_url = problem_link
        else:
            link_url = f"https://leetcode.com/problems/{title.lower().replace(' ', '-').replace('.', '')}"
            
        # Add difficulty badge
        if difficulty:
            diff_color = difficulty_colors.get(difficulty, "#666")
            difficulty_badge = f"""
            <div style="text-align: center; margin: 10px 0;">
                <span style="background-color: {diff_color}; color: white; padding: 4px 12px; 
                           border-radius: 12px; font-size: 12px; font-weight: bold;">
                    {difficulty}
                </span>
            </div>
            """
        else:
            difficulty_badge = ""
            
        problem_button = f"""
        <div style="text-align: center; margin: 30px 0;">
            <a href="{link_url}" 
               style="display: inline-block; background: linear-gradient(135deg, {color['primary']}, {color['secondary']}); 
                      color: white; padding: 15px 30px; text-decoration: none; border-radius: 25px; 
                      font-weight: bold; font-size: 16px; box-shadow: 0 4px 15px rgba(0,0,0,0.2); 
                      transition: transform 0.2s;">
                🚀 Solve Problem
            </a>
        </div>
        """
        
        # Dynamic tips based on difficulty
        if difficulty == "Easy":
            tips_content = """
                <li>Focus on understanding the problem clearly</li>
                <li>Think about the simplest approach first</li>
                <li>Test with the given examples</li>
                <li>Consider edge cases like empty inputs</li>
            """
        elif difficulty == "Medium":
            tips_content = """
                <li>Break the problem into smaller subproblems</li>
                <li>Consider multiple approaches (greedy, DP, etc.)</li>
                <li>Think about time and space complexity</li>
                <li>Use appropriate data structures</li>
            """
        else:  # Hard
            tips_content = """
                <li>Study similar problems and patterns</li>
                <li>Don't rush - take time to understand</li>
                <li>Consider advanced algorithms and techniques</li>
                <li>Break it down step by step</li>
            """
            
        tips_section = f"""
        <!-- Tips Section -->
        <div style="background-color: #f8f9fa; padding: 20px; border-radius: 8px; margin: 25px 0;">
            <h3 style="color: #333; margin: 0 0 15px 0; font-size: 18px;">💡 {difficulty} Problem Tips</h3>
            <ul style="color: #666; margin: 0; padding-left: 20px; line-height: 1.6;">
                {tips_content}
            </ul>
        </div>
        """
        
        motivation_quotes = [
            "The expert in anything was once a beginner.",
            "Every problem is a step forward in your journey.",
            "Consistency beats perfection every time.",
            "Code today, conquer tomorrow.",
            "Small progress is still progress."
        ]
        import random
        quote = random.choice(motivation_quotes)
        
        motivation_section = f"""
        <!-- Stats or Motivation -->
        <div style="text-align: center; padding: 20px; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); border-radius: 8px; margin: 25px 0;">
            <p style="color: white; margin: 0; font-size: 16px; font-style: italic;">
                "{quote}" 💪
            </p>
        </div>
        """
    
    return f"""
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>LeetCode Daily Tracker</title>
    </head>
    <body style="margin: 0; padding: 0; font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f5f5f5;">
        <div style="max-width: 600px; margin: 0 auto; background-color: white; box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);">
            
            <!-- Header -->
            <div style="background: linear-gradient(135deg, {color['primary']}, {color['secondary']}); padding: 30px; text-align: center;">
                <h1 style="color: white; margin: 0; font-size: 28px; font-weight: 300;">
                    🧠 LeetCode Daily Tracker
                </h1>
                <p style="color: rgba(255,255,255,0.9); margin: 10px 0 0 0; font-size: 16px;">
                    Your coding journey companion
                </p>
            </div>
            
            <!-- Content -->
            <div style="padding: 40px 30px;">
                <div style="background-color: {color['bg']}; border-left: 4px solid {color['primary']}; padding: 20px; margin-bottom: 25px; border-radius: 0 8px 8px 0;">
                    {content}
                    {difficulty_badge}
                </div>
                
                {problem_button}
                
                {tips_section}
                
                {motivation_section}
            </div>
            
            <!-- Footer -->
            <div style="background-color: #f8f9fa; padding: 25px 30px; border-top: 1px solid #eee;">
                <div style="text-align: center;">
                    <p style="color: #666; margin: 0 0 15px 0; font-size: 14px;">
                        Keep coding, keep growing! 🌱
                    </p>
                    <div style="margin: 15px 0;">
                        <a href="https://leetcode.com" style="color: {color['primary']}; text-decoration: none; margin: 0 10px;">📊 LeetCode</a>
                        <span style="color: #ccc;">|</span>
                        <a href="https://github.com" style="color: {color['primary']}; text-decoration: none; margin: 0 10px;">💻 GitHub</a>
                        <span style="color: #ccc;">|</span>
                        <a href="{unsubscribe_link if email_type != 'verification' else '#'}" style="color: #999; text-decoration: none; margin: 0 10px; font-size: 12px;">{'Unsubscribe' if email_type != 'verification' else ''}</a>
                    </div>
                    <p style="color: #999; font-size: 12px; margin: 15px 0 0 0;">
                        © 2024 LeetCode Daily Tracker. Made with ❤️ for coders.
                    </p>
                </div>
            </div>
        </div>
    </body>
    </html>
    """


# ================= VALIDATION =================

EMAIL_REGEX = re.compile(
    r"^[\w\.-]+@[\w\.-]+\.\w+$"
)


def valid_email(email):
    return bool(email and EMAIL_REGEX.match(email))


def valid_leetcode(username):

    if not username or len(username) < 3:
        return False

    try:
        r = requests.get(
            f"{LEETCODE_API}/{username}",
            timeout=8
        )
        return r.status_code == 200

    except:
        return False


# ================= LEETCODE =================

def get_daily_problem():
    try:
        r = requests.get(f"{LEETCODE_API}/daily", timeout=10)
        r.raise_for_status()

        d = r.json()
        print("📡 Daily API response keys:", list(d.keys()))

        # Handle the current API format
        if "questionTitle" in d and "titleSlug" in d:
            title = d["questionTitle"]
            slug = d["titleSlug"]
            link = d.get("questionLink", f"https://leetcode.com/problems/{slug}/")
            difficulty = d.get("difficulty", "Unknown")
            print(f"✅ Found daily problem: {title} ({difficulty}) - {slug}")
            return title, slug, link, difficulty

        # Fallback for older format
        if "title" in d and "titleSlug" in d:
            title = d["title"] 
            slug = d["titleSlug"]
            link = f"https://leetcode.com/problems/{slug}/"
            difficulty = d.get("difficulty", "Unknown")
            print(f"✅ Found daily problem (fallback): {title} ({difficulty}) - {slug}")
            return title, slug, link, difficulty

        # If we can't find the expected fields, print the response
        print("❌ Available fields in API response:", list(d.keys()))
        raise Exception("Could not find title and slug in daily API response")

    except requests.exceptions.RequestException as e:
        print(f"❌ Network error calling daily API: {e}")
        raise Exception(f"Failed to fetch daily problem: {e}")
    
    except json.JSONDecodeError as e:
        print(f"❌ JSON decode error: {e}")
        raise Exception("Invalid JSON response from daily API")


def solved_today(username, slug):

    try:
        r = requests.get(
            f"{LEETCODE_API}/{username}/acSubmission?limit=20",
            timeout=10
        )

        if r.status_code != 200:
            return False

        d = r.json()

        if "submission" in d:
            subs = d["submission"]
        elif "data" in d:
            subs = d["data"]
        elif isinstance(d, list):
            subs = d
        else:
            return False

        today = date.today()

        for s in subs:

            if not isinstance(s, dict):
                continue

            if s.get("titleSlug") != slug:
                continue

            ts = s.get("timestamp")

            if not ts:
                continue

            solved = datetime.fromtimestamp(
                int(ts),
                tz=pytz.utc
            ).date()

            if solved == today:
                return True

        return False

    except:
        return False


# ================= SUBSCRIBE =================

def subscribe(username, email, timezone):

    if not valid_leetcode(username):
        return "❌ Invalid LeetCode username"

    if not valid_email(email):
        return "❌ Invalid email"

    conn = get_db()
    cur = conn.cursor()

    cur.execute("""
        SELECT email_verified, verification_token, unsubscribed
        FROM users WHERE email=%s
    """, (email,))

    row = cur.fetchone()

    # Existing user logic...
    if row:
        verified, token, unsub = row

        if verified and not unsub:
            cur.close()
            conn.close()
            return "⚠️ Already subscribed"

        if verified and unsub:
            cur.execute("""
                UPDATE users
                SET unsubscribed=false,
                    leetcode_username=%s,
                    timezone=%s,
                    last_sent_date=NULL,
                    last_sent_slot=NULL
                WHERE email=%s
            """, (username, timezone, email))

            conn.commit()
            cur.close()
            conn.close()
            return "✅ Re-subscribed"

        # Resend verification with enhanced template
        verification_content = f"""
        <h2 style="color: #2196F3; margin: 0 0 15px 0;">Welcome back! 👋</h2>
        <p style="color: #333; font-size: 16px; line-height: 1.6; margin: 0 0 15px 0;">
            We're excited to have you on your coding journey again! 
        </p>
        <p style="color: #666; font-size: 14px; margin: 0;">
            Click the verification button above to activate your daily LeetCode reminders.
        </p>
        """
        
        html_email = create_email_template(
            "Email Verification", 
            verification_content, 
            f"{HF_URL}?verify={token}", 
            "verification"
        )

        send_email(email, "🔔 Please verify your email", html_email)
        cur.close()
        conn.close()
        return "📩 Verification re-sent"

    # New user - remove duplicate code
    token = uuid.uuid4().hex

    cur.execute("""
        INSERT INTO users(
            leetcode_username,email,timezone,
            email_verified,verification_token,unsubscribed
        )
        VALUES(%s,%s,%s,false,%s,false)
    """, (username, email, timezone, token))

    conn.commit()
    cur.close()
    conn.close()

    # Welcome email with enhanced template
    welcome_content = f"""
    <h2 style="color: #4CAF50; margin: 0 0 15px 0;">Welcome to the club! 🎉</h2>
    <p style="color: #333; font-size: 16px; line-height: 1.6; margin: 0 0 15px 0;">
        You're about to embark on an amazing coding journey with daily LeetCode challenges!
    </p>
    <div style="background-color: white; border: 2px dashed #4CAF50; padding: 15px; border-radius: 8px; margin: 15px 0;">
        <p style="color: #4CAF50; font-weight: bold; margin: 0 0 5px 0;">📅 Your Schedule:</p>
        <p style="color: #666; font-size: 14px; margin: 0;">
            🌅 <strong>9 AM</strong> - Daily problem<br>
            🌆 <strong>3 PM</strong> - Gentle reminder<br>
            🌙 <strong>8 PM</strong> - Final reminder
        </p>
    </div>
    <p style="color: #666; font-size: 14px; margin: 0;">
        Click the verification button above to start receiving your personalized reminders!
    </p>
    """
    
    html_email = create_email_template(
        "Welcome", 
        welcome_content, 
        f"{HF_URL}?verify={token}", 
        "verification"
    )

    send_email(email, "🎯 Verify your LeetCode journey!", html_email)
    return "📩 Verification sent"


# ================= VERIFY =================

def verify_user(token):

    conn = get_db()
    cur = conn.cursor()

    cur.execute("""
        UPDATE users
        SET email_verified=true
        WHERE verification_token=%s
        AND email_verified=false
    """, (token,))

    ok = cur.rowcount

    conn.commit()
    cur.close()
    conn.close()

    if ok == 0:
        return "❌ Invalid link"

    return "✅ Email verified"


# ================= UNSUBSCRIBE =================

def unsubscribe_user(token):

    conn = get_db()
    cur = conn.cursor()

    cur.execute("""
        UPDATE users
        SET unsubscribed=true
        WHERE verification_token=%s
    """, (token,))

    ok = cur.rowcount

    conn.commit()
    cur.close()
    conn.close()

    if ok == 0:
        return "❌ Invalid link"

    return "✅ Unsubscribed"


# ================= URL HANDLER =================

def handle_url(request: gr.Request):

    try:
        params = request.query_params

        if "verify" in params:
            return verify_user(params["verify"])

        if "unsubscribe" in params:
            return unsubscribe_user(params["unsubscribe"])

        return ""

    except Exception as e:
        print("URL error:", e)
        return ""



def run_scheduler(secret):

    if secret != CRON_SECRET:
        return "❌ Unauthorized"

    conn = get_db()
    cur = conn.cursor()

    cur.execute("""
        SELECT id,leetcode_username,email,timezone,
               last_sent_date,last_sent_slot,verification_token
        FROM users
        WHERE email_verified=true
        AND unsubscribed=false
    """)

    users = cur.fetchall()

    try:
        title, slug, problem_link, difficulty = get_daily_problem()
    except Exception as e:
        cur.close()
        conn.close()
        return f"❌ Failed to get daily problem: {e}"

    now = datetime.now(pytz.utc)
    sent = 0

    for uid, user, mail, tz, last_d, last_s, token in users:

        try:
            local = now.astimezone(pytz.timezone(tz))
            h = local.hour

            # Enhanced email content based on time
            if 8 <= h <= 9:
                slot = "morning"
                subject = f"🌅 Today's LeetCode Challenge: {title}"
                content = f"""
                <h2 style="color: #4CAF50; margin: 0 0 15px 0;">Good morning, coder! ☀️</h2>
                <p style="color: #333; font-size: 18px; font-weight: bold; margin: 0 0 10px 0;">
                    Today's Problem: <span style="color: #4CAF50;">{title}</span>
                </p>
                <p style="color: #666; font-size: 16px; line-height: 1.6; margin: 0;">
                    Start your day with a fresh challenge! This {difficulty} problem is perfect for warming up 
                    your coding muscles. Take your time to understand the requirements! 🚀
                </p>
                """
                email_type = "morning"

            elif 14 <= h <= 15:
                slot = "afternoon"  
                subject = f"⏰ Afternoon Coding Break: {title}"
                content = f"""
                <h2 style="color: #FF9800; margin: 0 0 15px 0;">Time for a coding break! ⚡</h2>
                <p style="color: #333; font-size: 16px; margin: 0 0 15px 0;">
                    Haven't tackled <strong style="color: #FF9800;">{title}</strong> yet? No worries!
                </p>
                <p style="color: #666; font-size: 16px; line-height: 1.6; margin: 0;">
                    This {difficulty} problem is waiting for you. Sometimes a fresh afternoon perspective 
                    can lead to breakthrough solutions! 💡
                </p>
                """
                email_type = "afternoon"

            elif 19 <= h <= 20:
                slot = "night"
                subject = f"🌙 Last Call: {title}"
                content = f"""
                <h2 style="color: #F44336; margin: 0 0 15px 0;">Final reminder! 🔥</h2>
                <p style="color: #333; font-size: 16px; margin: 0 0 15px 0;">
                    <strong style="color: #F44336;">{title}</strong> ({difficulty}) is still waiting for you!
                </p>
                <p style="color: #666; font-size: 16px; line-height: 1.6; margin: 0 0 15px 0;">
                    Don't let the day end without giving it a try. Even reading through the problem 
                    and thinking about approaches counts as progress! 
                </p>
                <div style="background-color: #fff3cd; border: 1px solid #ffeaa7; padding: 15px; border-radius: 8px;">
                    <p style="color: #856404; margin: 0; font-size: 14px;">
                        💪 <strong>Remember:</strong> Consistency beats perfection. Every attempt makes you stronger!
                    </p>
                </div>
                """
                email_type = "night"

            else:
                continue

            today = date.today()

            # Check if already sent today
            if last_d == today and last_s == slot:
                print(f"⏭️ Skipping {mail} - already sent {slot} email today")
                continue

            # Check if user already solved the problem
            if solved_today(user, slug):
                print(f"✅ {user} already solved {slug} - skipping email")
                continue

            # Create beautiful HTML email with all enhancements
            html_email = create_email_template(
                title, 
                content, 
                f"{HF_URL}?unsubscribe={token}", 
                email_type,
                problem_link,
                difficulty
            )

            ok = send_email(mail, subject, html_email)

            if not ok:
                print(f"❌ Failed to send email to {mail}")
                continue

            # Update database
            cur.execute("""
                UPDATE users
                SET last_sent_date=%s,
                    last_sent_slot=%s
                WHERE id=%s
            """, (today, slot, uid))

            sent += 1

        except Exception as e:
            print(f"❌ Error processing user {user} ({mail}): {e}")
            continue

    conn.commit()
    cur.close()
    conn.close()

    return f"✅ Scheduler completed. Sent: {sent} emails"



# ================= UI =================
with gr.Blocks(
    title="LeetCode Notifier",
    theme=gr.themes.Soft(),
    css="""
    .gradio-container {
        max-width: 800px !important;
        margin: auto !important;
    }
    """
) as app:

    gr.Markdown("""
    # 📬 LeetCode Daily Email Notifier
    
    Get personalized daily LeetCode problem reminders sent directly to your inbox! 
    Never miss a day of coding practice.
    """)

    with gr.Row():
        with gr.Column():
            u = gr.Textbox(
                label="🧑‍💻 LeetCode Username", 
                placeholder="Enter your LeetCode username",
                info="We'll verify this username exists on LeetCode"
            )
            m = gr.Textbox(
                label="📧 Email Address", 
                placeholder="your.email@gmail.com",
                info="You'll receive a verification email"
            )
            tz = gr.Dropdown(
                choices=sorted(pytz.all_timezones), 
                value="Asia/Kolkata", 
                label="🌍 Timezone",
                info="Choose your timezone for proper scheduling"
            )

    with gr.Row():
        subscribe_btn = gr.Button("🚀 Subscribe", variant="primary", scale=2)
        
    out = gr.Textbox(label="📝 Status", interactive=False, lines=2)
    
    subscribe_btn.click(subscribe, [u, m, tz], out)

    gr.Markdown("""
    ---
    ### ⏰ Email Schedule
    - **🌅 9:00 AM** - Daily problem notification
    - **🌆 3:00 PM** - Gentle reminder (if not solved)
    - **🌙 8:00 PM** - Final reminder (if not solved)
    
    ### 🔒 Admin Panel
    """)

    with gr.Row():
        sec = gr.Textbox(
            label="🔑 Secret Key", 
            type="password", 
            placeholder="Enter scheduler secret key"
        )
        run_btn = gr.Button("▶️ Run Scheduler", variant="secondary")

    run_btn.click(run_scheduler, sec, out)

    # URL handler for verification/unsubscribe
    app.load(handle_url, outputs=out)


if __name__ == "__main__":
    app.launch(debug=True)