import os
import sys

# Hugging Face safe cache
os.environ["HF_HOME"] = "/tmp/huggingface"
os.environ["TRANSFORMERS_CACHE"] = "/tmp/huggingface/transformers"
os.environ["HUGGINGFACE_HUB_CACHE"] = "/tmp/huggingface/hub"

# Force Flask instance path to a writable temporary folder
safe_instance_path = "/tmp/flask_instance"

# Create the safe instance path after imports
os.makedirs(safe_instance_path, exist_ok=True)

from flask import Flask, render_template, redirect, url_for, flash, request, jsonify
from flask_login import LoginManager, login_required, current_user
from werkzeug.utils import secure_filename
import sys
import json
from datetime import datetime

# Adjust sys.path for import flexibility
current_dir = os.path.dirname(os.path.abspath(__file__))
sys.path.append(current_dir)

# Import and initialize DB
from backend.models.database import db, Job, Application, init_db
from backend.models.user import User
from backend.routes.auth import auth_bp, handle_resume_upload
from backend.routes.interview_api import interview_api
# Import additional utilities
import re
import json

# -----------------------------------------------------------------------------
# Chatbot setup
#
# The chatbot feature uses a local vector database (Chroma) to search the
# ``chatbot/chatbot.txt`` knowledge base and then calls the Groq API via the
# OpenAI client.  To avoid the expensive model and database initialisation on
# every request, we lazily load the embeddings and collection the first time
# a chat query is processed.  Subsequent requests reuse the same global
# objects.  See ``init_chatbot()`` and ``get_chatbot_response()`` below for
# implementation details.

# Paths for the chatbot knowledge base and persistent vector store.  We
# compute these relative to the current file so that the app can be deployed
# anywhere without needing to change configuration.  The ``chroma_db``
# directory will be created automatically by the Chroma client if it does not
# exist.
import shutil

# Remove any old unwritable Chroma DB path from previous versions
shutil.rmtree("/app/chatbot/chroma_db", ignore_errors=True)
CHATBOT_TXT_PATH = os.path.join(current_dir, 'chatbot', 'chatbot.txt')
CHATBOT_DB_DIR = "/tmp/chroma_db"
# -----------------------------------------------------------------------------
# Hugging Face model configuration
#
# The original chatbot implementation sent queries to the Groq API via the
# OpenAI client.  To remove that dependency we now load a small conversational
# model from Hugging Face.  ``HF_MODEL_NAME`` defines which model to use.  The
# default value, ``facebook/blenderbot-400M-distill``, provides a good
# balance between quality and resource consumption and is available on
# Hugging Face without requiring authentication.  Should you wish to swap to
# another conversational model (e.g. ``microsoft/DialoGPT-medium``), update
# this constant accordingly.  The model and tokenizer are loaded lazily in
# ``init_hf_model()`` to avoid impacting application startup time.
HF_MODEL_NAME = "facebook/blenderbot-400M-distill"

# Global Hugging Face model and tokenizer.  These variables remain ``None``
# until ``init_hf_model()`` is called.  They are reused across all chatbot
# requests to prevent repeatedly loading the large model into memory.
_hf_model = None
_hf_tokenizer = None

def init_hf_model() -> None:
    """Initialise the Hugging Face conversational model and tokenizer.

    Loading large Transformer models can be expensive.  This helper ensures
    that we only perform the download and model initialisation once.  On
    subsequent calls the function returns immediately if the model and
    tokenizer are already loaded.  The model is moved to GPU if one is
    available; otherwise it will run on the CPU.  Any import of heavy
    dependencies such as ``transformers`` or ``torch`` is performed inside
    this function to keep the global import section lightweight.
    """
    global _hf_model, _hf_tokenizer
    if _hf_model is not None and _hf_tokenizer is not None:
        return
    # Local imports to avoid pulling heavy dependencies during module import.
    from transformers import AutoModelForSeq2SeqLM, AutoTokenizer
    import torch

    # Determine execution device.  Prefer CUDA if available; otherwise
    # fallback to CPU.  The application will run correctly on CPU-only
    # systems albeit with higher latency.
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    # Load tokenizer and model.  The model weights will be downloaded the
    # first time this function runs.  Hugging Face caches models under
    # ``HF_HOME`` / ``TRANSFORMERS_CACHE`` which are set at the top of
    # this file to a writable temporary directory.
    tokenizer = AutoTokenizer.from_pretrained(HF_MODEL_NAME)
    model = AutoModelForSeq2SeqLM.from_pretrained(HF_MODEL_NAME)
    model.to(device)

    _hf_model = model
    _hf_tokenizer = tokenizer

# Global objects used by the chatbot.  They remain ``None`` until
# ``init_chatbot()`` runs.  After initialisation, ``_chatbot_embedder`` holds
# the SentenceTransformer model and ``_chatbot_collection`` is the Chroma
# collection with embedded knowledge base documents.  A separate import of
# the OpenAI client is performed in ``get_chatbot_response()`` to avoid
# unintentional import side effects at module import time.
_chatbot_embedder = None
_chatbot_collection = None

def init_hf_model() -> None:
    """Initialise the Hugging Face conversational model and tokenizer."""
    global _hf_model, _hf_tokenizer
    if _hf_model is not None and _hf_tokenizer is not None:
        return

    from transformers import AutoModelForSeq2SeqLM, AutoTokenizer
    import torch

    model_name = "facebook/blenderbot-400M-distill"
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    tokenizer = AutoTokenizer.from_pretrained(model_name)
    model = AutoModelForSeq2SeqLM.from_pretrained(model_name).to(device)

    _hf_model = model
    _hf_tokenizer = tokenizer


def get_chatbot_response(query: str) -> str:
    """Generate a reply to the user's query using Chroma + Hugging Face model."""
    init_chatbot()
    init_hf_model()

    # Safety: prevent empty input
    if not query or not query.strip():
        return "Please type a question about the Codingo platform."

    embedder = _chatbot_embedder
    collection = _chatbot_collection
    model = _hf_model
    tokenizer = _hf_tokenizer
    device = model.device

    # Retrieve context from Chroma
    query_embedding = embedder.encode([query])[0]
    results = collection.query(query_embeddings=[query_embedding], n_results=3)
    retrieved_docs = results.get("documents", [[]])[0] if results else []
    context = "\n".join(retrieved_docs)

    # System instruction
    system_prompt = (
        "You are a helpful assistant for the Codingo website. "
        "Only answer questions relevant to the context provided. "
        "If unrelated, reply: 'I'm only trained to answer questions about the Codingo platform.'"
    )

    prompt = f"{system_prompt}\n\nContext:\n{context}\n\nQuestion: {query}\n\nAnswer:"

    # ✅ Safe tokenization with truncation to avoid CUDA indexing issues
    inputs = tokenizer(
        prompt,
        return_tensors="pt",
        truncation=True,
        max_length=256,  # Prevents long inputs
        padding=True
    ).to(device)

    try:
        output_ids = model.generate(
            **inputs,
            max_length=200,
            num_beams=3,
            do_sample=False,
            early_stopping=True
        )
        reply = tokenizer.decode(output_ids[0], skip_special_tokens=True)
        if reply.startswith(prompt):
            reply = reply[len(prompt):]
        return reply.strip()
    except Exception as e:
        return f"Error generating response: {str(e)}"

# Initialize Flask app
app = Flask(
    __name__,
    static_folder='backend/static',
    static_url_path='/static',
    template_folder='backend/templates',
    instance_path=safe_instance_path  # ✅ points to writable '/tmp/flask_instance'
)

app.config['SECRET_KEY'] = 'saadi'

# -----------------------------------------------------------------------------
# Cookie configuration for Hugging Face Spaces
#
# When running this app inside an iframe (as is typical on Hugging Face Spaces),
# browsers will drop cookies that have the default SameSite policy of ``Lax``.
# This prevents the Flask session cookie from being stored and means that
# ``login_user()`` will appear to have no effect – the user will be redirected
# back to the home page but remain anonymous. By explicitly setting the
# SameSite policy to ``None`` and enabling the ``Secure`` flag, we allow the
# session and remember cookies to be sent even when the app is embedded in an
# iframe. Without these settings the sign‑up and login flows work locally
# but silently fail in Spaces, causing the "redirect to home page without
# anything" behaviour reported by users.
app.config['SESSION_COOKIE_SAMESITE'] = 'None'
app.config['SESSION_COOKIE_SECURE'] = True
app.config['REMEMBER_COOKIE_SAMESITE'] = 'None'
app.config['REMEMBER_COOKIE_SECURE'] = True

# Configure the database connection
# Use /tmp directory for database in Hugging Face Spaces
# Note: Data will be lost when the space restarts
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/codingo.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
from flask_wtf.csrf import CSRFProtect

# csrf = CSRFProtect(app)

# Create necessary directories in writable locations
os.makedirs('/tmp/static/audio', exist_ok=True)
os.makedirs('/tmp/temp', exist_ok=True)

# Initialize DB with app
init_db(app)

# Flask-Login setup
login_manager = LoginManager()
login_manager.login_view = 'auth.login'
login_manager.init_app(app)

@login_manager.user_loader
def load_user(user_id):
    return db.session.get(User, int(user_id))

# Register blueprints
app.register_blueprint(auth_bp)
app.register_blueprint(interview_api, url_prefix="/api")

# Routes (keep your existing routes)
@app.route('/')
def index():
    return render_template('index.html')

@app.route('/jobs')
def jobs():
    all_jobs = Job.query.order_by(Job.date_posted.desc()).all()
    return render_template('jobs.html', jobs=all_jobs)

@app.route('/job/<int:job_id>')
def job_detail(job_id):
    job = Job.query.get_or_404(job_id)
    return render_template('job_detail.html', job=job)

@app.route('/apply/<int:job_id>', methods=['GET', 'POST'])
@login_required
def apply(job_id):
    job = Job.query.get_or_404(job_id)
    if request.method == 'POST':
        # Retrieve the uploaded resume file from the request.  The ``name``
        # attribute in the HTML form is ``resume``.
        file = request.files.get('resume')
        # Use our safe upload helper to store the resume.  ``filepath``
        # contains the location where the file was saved so that recruiters
        # can download it later. Resume parsing has been disabled, so
        # ``features`` will always be an empty dictionary.
        features, error, filepath = handle_resume_upload(file)

        # If there was an error saving the resume, notify the user.  We no
        # longer attempt to parse the resume contents, so the manual fields
        # collected below will form the entire feature set.
        if error:
            flash("Resume upload failed. Please try again.", "danger")
            return render_template('apply.html', job=job)

        # Collect the manually entered fields for skills, experience and education.
        # Users can separate entries with commas, semicolons or newlines; we
        # normalise the input into lists of trimmed strings.
        def parse_entries(raw_value: str):
            import re
            entries = []
            if raw_value:
                # Split on commas, semicolons or newlines
                for item in re.split(r'[\n,;]+', raw_value):
                    item = item.strip()
                    if item:
                        entries.append(item)
            return entries

        skills_input = request.form.get('skills', '')
        experience_input = request.form.get('experience', '')
        education_input = request.form.get('education', '')

        manual_features = {
            "skills": parse_entries(skills_input),
            "experience": parse_entries(experience_input),
            "education": parse_entries(education_input)
        }

        # Prepare the application record.  We ignore the empty ``features``
        # returned by ``handle_resume_upload`` and instead persist the
        # manually collected attributes.  The extracted_features column
        # expects a JSON string; json.dumps handles proper serialization.
        application = Application(
            job_id=job_id,
            user_id=current_user.id,
            name=current_user.username,
            email=current_user.email,
            resume_path=filepath,
            extracted_features=json.dumps(manual_features)
        )

        db.session.add(application)
        db.session.commit()

        flash('Your application has been submitted successfully!', 'success')
        return redirect(url_for('jobs'))

    return render_template('apply.html', job=job)

@app.route('/my_applications')
@login_required
def my_applications():
    applications = Application.query.filter_by(
        user_id=current_user.id
    ).order_by(Application.date_applied.desc()).all()
    return render_template('my_applications.html', applications=applications)

# -----------------------------------------------------------------------------
# Chatbot API endpoint
#
# This route receives a JSON payload containing a ``message`` field from the
# front‑end chat widget.  It validates the input, invokes the chatbot
# response function and returns a JSON response.  Any errors are surfaced
# as a 400 or 500 response with an ``error`` message field.
@app.route('/chatbot', methods=['POST'])
def chatbot_endpoint():
    data = request.get_json(silent=True) or {}
    user_input = str(data.get('message', '')).strip()
    if not user_input:
        return jsonify({"error": "Empty message"}), 400
    try:
        reply = get_chatbot_response(user_input)
        return jsonify({"response": reply})
    except Exception as exc:
        # Log the exception to stderr for debugging in the console.  In a
        # production setting you might want to log this to a proper logging
        # facility instead.
        print(f"Chatbot error: {exc}", file=sys.stderr)
        return jsonify({"error": str(exc)}), 500

@app.route('/parse_resume', methods=['POST'])
def parse_resume():
    file = request.files.get('resume')
    features, error, filepath = handle_resume_upload(file)

    # If the upload failed, return an error.  Parsing is no longer
    # supported, so we do not attempt to inspect the resume contents.
    if error:
        return {"error": "Error processing resume. Please try again."}, 400

    # If no features were extracted (the normal case now), respond with
    # empty fields rather than an error.  This preserves the API
    # contract expected by any front‑end code that might call this
    # endpoint.
    if not features:
        return {
            "name": "",
            "email": "",
            "mobile_number": "",
            "skills": [],
            "experience": [],
            "education": [],
            "summary": ""
        }, 200

    # Should features contain values (unlikely in the new implementation),
    # pass them through to the client.
    response = {
        "name": features.get('name', ''),
        "email": features.get('email', ''),
        "mobile_number": features.get('mobile_number', ''),
        "skills": features.get('skills', []),
        "experience": features.get('experience', []),
        "education": features.get('education', []),
        "summary": features.get('summary', '')
    }
    return response, 200

@app.route("/interview/<int:job_id>")
@login_required
def interview_page(job_id):
    job = Job.query.get_or_404(job_id)
    application = Application.query.filter_by(
        user_id=current_user.id, 
        job_id=job_id
    ).first()
    
    if not application or not application.extracted_features:
        flash("Please apply for this job and upload your resume first.", "warning")
        return redirect(url_for('job_detail', job_id=job_id))
    
    cv_data = json.loads(application.extracted_features)
    return render_template("interview.html", job=job, cv=cv_data)


# -----------------------------------------------------------------------------
# Recruiter job posting route
#
# Authenticated users with a recruiter or admin role can access this page to
# create new job listings.  Posted jobs are associated with the current
# recruiter via the ``recruiter_id`` foreign key on the ``Job`` model.
@app.route('/post_job', methods=['GET', 'POST'])
@login_required
def post_job():
    # Only allow recruiters and admins to post jobs
    if current_user.role not in ('recruiter', 'admin'):
        flash('You do not have permission to post jobs.', 'warning')
        return redirect(url_for('jobs'))

    if request.method == 'POST':
        # Extract fields from the form
        role_title = request.form.get('role', '').strip()
        description = request.form.get('description', '').strip()
        seniority = request.form.get('seniority', '').strip()
        skills_input = request.form.get('skills', '').strip()
        company = request.form.get('company', '').strip()

        # Validate required fields
        errors = []
        if not role_title:
            errors.append('Job title is required.')
        if not description:
            errors.append('Job description is required.')
        if not seniority:
            errors.append('Seniority level is required.')
        if not skills_input:
            errors.append('Skills are required.')
        if not company:
            errors.append('Company name is required.')

        if errors:
            for err in errors:
                flash(err, 'danger')
            return render_template('post_job.html')

        # Normalise the skills input into a JSON encoded list.  Users can
        # separate entries with commas, semicolons or newlines.
        skills_list = [s.strip() for s in re.split(r'[\n,;]+', skills_input) if s.strip()]
        skills_json = json.dumps(skills_list)

        # Create and persist the new job
        new_job = Job(
            role=role_title,
            description=description,
            seniority=seniority,
            skills=skills_json,
            company=company,
            recruiter_id=current_user.id
        )
        db.session.add(new_job)
        db.session.commit()

        flash('Job posted successfully!', 'success')
        return redirect(url_for('jobs'))

    # GET request returns the form
    return render_template('post_job.html')


# -----------------------------------------------------------------------------
# Recruiter dashboard route
#
# Displays a list of candidates who applied to jobs posted by the current
# recruiter.  Candidates are sorted by a simple skill match score computed
# against the job requirements.  A placeholder download button is provided
# for future PDF report functionality.
@app.route('/dashboard')
@login_required
def dashboard():
    # Only recruiters and admins can view the dashboard
    if current_user.role not in ('recruiter', 'admin'):
        flash('You do not have permission to access the dashboard.', 'warning')
        return redirect(url_for('index'))

    # Fetch jobs posted by the current recruiter
    posted_jobs = Job.query.filter_by(recruiter_id=current_user.id).all()
    job_ids = [job.id for job in posted_jobs]

    candidates_with_scores = []
    if job_ids:
        # Fetch applications associated with these job IDs
        candidate_apps = Application.query.filter(Application.job_id.in_(job_ids)).all()

        # Helper to compute a match score based on skills overlap
        def compute_score(application):
            try:
                # Extract candidate skills from stored JSON
                candidate_features = json.loads(application.extracted_features) if application.extracted_features else {}
                candidate_skills = candidate_features.get('skills', [])
                # Retrieve the job's required skills and parse from JSON
                job_skills = json.loads(application.job.skills) if application.job and application.job.skills else []
                if not job_skills:
                    return ('Medium', 2)  # Default when job specifies no skills

                # Compute case‑insensitive intersection
                candidate_set = {s.lower() for s in candidate_skills}
                job_set = {s.lower() for s in job_skills}
                common = candidate_set & job_set
                ratio = len(common) / len(job_set) if job_set else 0

                # Map ratio to qualitative score
                if ratio >= 0.75:
                    return ('Excellent', 4)
                elif ratio >= 0.5:
                    return ('Good', 3)
                elif ratio >= 0.25:
                    return ('Medium', 2)
                else:
                    return ('Poor', 1)
            except Exception:
                return ('Medium', 2)

        # Build a list of candidate applications with computed scores
        for app_record in candidate_apps:
            score_label, score_value = compute_score(app_record)
            candidates_with_scores.append({
                'application': app_record,
                'score_label': score_label,
                'score_value': score_value
            })

        # Sort candidates from highest to lowest score
        candidates_with_scores.sort(key=lambda item: item['score_value'], reverse=True)

    return render_template('dashboard.html', candidates=candidates_with_scores)

if __name__ == '__main__':
    print("Starting Codingo application...")
    with app.app_context():
        db.create_all()
    
    # Use port from environment or default to 7860
    port = int(os.environ.get('PORT', 7860))
    app.run(debug=True, host='0.0.0.0', port=port)