import json
import hmac
import hashlib
import logging
from datetime import date
from flask import (Blueprint, render_template, redirect, url_for, flash,
                   request, jsonify, current_app, session)
from flask_login import login_required, current_user
from app.extensions import db
from app.models.teller_enrollment import TellerEnrollment, TellerAccount
from app.models.account import Account
from app.services.teller_service import (
    get_accounts, get_balance, sync_preview, import_transactions,
    ACCOUNT_TYPE_MAP,
)

teller_bp = Blueprint('teller', __name__, url_prefix='/teller')
log = logging.getLogger(__name__)

from app.extensions import csrf as _csrf
# Webhook receives POSTs from Teller servers — no CSRF token
_csrf_exempt_views = ['teller.webhook']


# ── Connect callback ──────────────────────────────────────────────────────────

@teller_bp.route('/callback', methods=['POST'])
@login_required
def callback():
    """
    Teller Connect posts here after user successfully enrolls.
    Body: { enrollment: { id, accessToken }, selectedAccount: { ... } }
    We store the enrollment and discovered accounts, then redirect to mapping.
    """
    data = request.get_json()
    if not data:
        return jsonify({'error': 'No data'}), 400

    enrollment_data = data.get('enrollment', {})
    enrollment_id = enrollment_data.get('id', '')
    access_token = enrollment_data.get('accessToken', '')

    if not enrollment_id or not access_token:
        return jsonify({'error': 'Missing enrollment data'}), 400

    # Upsert enrollment
    enrollment = TellerEnrollment.query.filter_by(enrollment_id=enrollment_id).first()
    if not enrollment:
        enrollment = TellerEnrollment(
            enrollment_id=enrollment_id,
            access_token=access_token,
        )
        db.session.add(enrollment)

    # Fetch accounts from Teller
    try:
        teller_accounts = get_accounts(access_token)
    except Exception as e:
        log.error(f'[teller] get_accounts failed: {e}')
        return jsonify({'error': f'Could not fetch accounts: {e}'}), 502

    institution_name = ''
    for ta in teller_accounts:
        institution_name = ta.get('institution', {}).get('name', '')
        ta_id = ta['id']

        existing = TellerAccount.query.filter_by(teller_account_id=ta_id).first()
        if not existing:
            subtype = ta.get('subtype', 'other').lower()
            db.session.add(TellerAccount(
                enrollment=enrollment,
                teller_account_id=ta_id,
                account_name=ta.get('name', ''),
                account_type=ta.get('type', ''),
                account_subtype=subtype,
                institution_name=institution_name,
            ))

    enrollment.institution_name = institution_name
    enrollment.user_id = enrollment_data.get('user', {}).get('id', '')
    db.session.commit()

    return jsonify({'status': 'ok', 'redirect': url_for('teller.map_accounts', enrollment_id=enrollment_id)})


@teller_bp.route('/map/<enrollment_id>', methods=['GET', 'POST'])
@login_required
def map_accounts(enrollment_id):
    """
    Let user map each Teller account to a PFM account (or create new).
    POST saves the mapping and redirects to sync preview.
    """
    enrollment = TellerEnrollment.query.filter_by(enrollment_id=enrollment_id).first_or_404()
    teller_accounts = enrollment.accounts.filter_by(is_active=True).all()
    pfm_accounts = Account.query.filter_by(is_active=True).order_by(Account.name).all()

    if request.method == 'POST':
        for ta in teller_accounts:
            key = f'pfm_account_{ta.id}'
            val = request.form.get(key, '')
            if val == 'new':
                # Auto-create a new PFM account
                subtype = ta.account_subtype or 'checking'
                pfm_type = ACCOUNT_TYPE_MAP.get(subtype, 'other')
                new_acct = Account(
                    name=f'{ta.institution_name} — {ta.account_name}',
                    account_type=pfm_type,
                    color='#4F81C7',
                    icon='bi-bank',
                    balance=0,
                )
                db.session.add(new_acct)
                db.session.flush()
                ta.pfm_account_id = new_acct.id
            elif val.isdigit():
                ta.pfm_account_id = int(val)
            # val == '' means skip this account
        db.session.commit()

        # Redirect to sync all mapped accounts
        mapped = [ta for ta in teller_accounts if ta.pfm_account_id]
        if not mapped:
            flash('No accounts mapped. Select at least one account to sync.', 'warning')
            return redirect(url_for('teller.map_accounts', enrollment_id=enrollment_id))

        flash(f'{len(mapped)} account(s) mapped. Ready to sync.', 'success')
        return redirect(url_for('teller.index'))

    return render_template('teller/map_accounts.html',
                           enrollment=enrollment,
                           teller_accounts=teller_accounts,
                           pfm_accounts=pfm_accounts)


# ── Index — enrolled accounts overview ───────────────────────────────────────

@teller_bp.route('/')
@login_required
def index():
    enrollments = TellerEnrollment.query.filter_by(is_active=True).all()
    return render_template('teller/index.html', enrollments=enrollments)


# ── Sync: preview then confirm ────────────────────────────────────────────────

@teller_bp.route('/sync/<int:teller_account_id>', methods=['GET'])
@login_required
def sync_preview_view(teller_account_id):
    """Fetch transactions from Teller and show preview before importing."""
    ta = db.get_or_404(TellerAccount, teller_account_id)

    if not ta.pfm_account_id:
        flash('This account is not mapped to a PFM account. Please map it first.', 'warning')
        return redirect(url_for('teller.map_accounts', enrollment_id=ta.enrollment.enrollment_id))

    try:
        preview = sync_preview(ta)
    except Exception as e:
        flash(f'Sync failed: {e}', 'danger')
        return redirect(url_for('teller.index'))

    # Store preview in session for confirm step
    session['teller_preview'] = [
        {
            'teller_id':        p['teller_id'],
            'date':             p['date'].isoformat(),
            'transaction_type': p['transaction_type'],
            'amount':           p['amount'],
            'description':      p['description'],
            'account_id':       p['account_id'],
            'category_id':      p['category_id'],
            'notes':            p['notes'],
        }
        for p in preview
    ]
    session['teller_account_id'] = teller_account_id

    return render_template('teller/preview.html',
                           ta=ta,
                           preview=preview,
                           count=len(preview))


@teller_bp.route('/sync/confirm', methods=['POST'])
@login_required
def sync_confirm():
    """Import the previewed transactions."""
    raw = session.pop('teller_preview', [])
    ta_id = session.pop('teller_account_id', None)

    if not raw or not ta_id:
        flash('No pending import. Please sync again.', 'warning')
        return redirect(url_for('teller.index'))

    ta = db.get_or_404(TellerAccount, ta_id)

    # Reconstruct parsed list with date objects
    from datetime import date as date_cls
    parsed = []
    for r in raw:
        r['date'] = date_cls.fromisoformat(r['date'])
        parsed.append(r)

    imported, skipped = import_transactions(parsed, ta)
    flash(f'Imported {imported} transaction(s). Skipped {skipped} duplicate(s).', 'success')
    return redirect(url_for('transactions.index'))


@teller_bp.route('/sync/all', methods=['POST'])
@login_required
def sync_all():
    """Sync all mapped accounts — redirects to first account's preview."""
    enrollments = TellerEnrollment.query.filter_by(is_active=True).all()
    mapped = []
    for e in enrollments:
        for ta in e.accounts.filter_by(is_active=True).all():
            if ta.pfm_account_id:
                mapped.append(ta)

    if not mapped:
        flash('No accounts mapped for sync.', 'warning')
        return redirect(url_for('teller.index'))

    # For simplicity, sync first account; user can chain through others
    return redirect(url_for('teller.sync_preview_view', teller_account_id=mapped[0].id))


# ── Balance refresh ───────────────────────────────────────────────────────────

@teller_bp.route('/balance/<int:teller_account_id>', methods=['POST'])
@login_required
def refresh_balance(teller_account_id):
    """Fetch live balance from Teller and update the linked PFM account."""
    ta = db.get_or_404(TellerAccount, teller_account_id)
    if not ta.pfm_account_id:
        return jsonify({'error': 'Account not mapped'}), 400

    try:
        bal_data = get_balance(ta.enrollment.access_token, ta.teller_account_id)
        available = float(bal_data.get('available') or bal_data.get('ledger') or 0)
        ta.pfm_account.balance = available
        db.session.commit()
        return jsonify({'balance': available, 'status': 'ok'})
    except Exception as e:
        log.error(f'[teller] balance refresh failed: {e}')
        return jsonify({'error': str(e)}), 502


# ── Disconnect ────────────────────────────────────────────────────────────────

@teller_bp.route('/disconnect/<int:enrollment_db_id>', methods=['POST'])
@login_required
def disconnect(enrollment_db_id):
    enrollment = db.get_or_404(TellerEnrollment, enrollment_db_id)
    enrollment.is_active = False
    for ta in enrollment.accounts:
        ta.is_active = False
    db.session.commit()
    flash(f'Disconnected from {enrollment.institution_name}.', 'info')
    return redirect(url_for('teller.index'))


# ── Webhook: transactions.processed ──────────────────────────────────────────

@teller_bp.route('/webhook', methods=['GET', 'POST'])
@_csrf.exempt
def webhook():
    """
    Teller fires this when new transactions are available.
    Verifies signature then marks account as needing sync.
    Does NOT auto-import — user must confirm via the UI.
    """
    # Verify Teller webhook signature
    # Header format: Teller-Signature: t=<timestamp>,v1=<sig1>,v1=<sig2>
    # Signed message: <timestamp>.<raw_body>
    signing_secret = current_app.config.get('TELLER_WEBHOOK_SECRET', '')
    if signing_secret:
        sig_header = request.headers.get('Teller-Signature', '')
        body = request.get_data()

        if not sig_header:
            log.warning('[teller] missing Teller-Signature header')
            return jsonify({'error': 'Missing signature'}), 401

        # Parse header: t=<timestamp>,v1=<sig>,v1=<sig2>...
        parts = dict(
            (p.split('=', 1) if '=' in p else (p, ''))
            for p in sig_header.split(',')
        )
        timestamp = parts.get('t', '')
        # Collect all v1 signatures (may be multiple during key rotation)
        signatures = [v for k, v in
                      [p.split('=', 1) for p in sig_header.split(',') if p.startswith('v1=')]
                      ]

        if not timestamp or not signatures:
            log.warning('[teller] malformed Teller-Signature header')
            return jsonify({'error': 'Invalid signature'}), 401

        # Reject replays older than 5 minutes
        import time
        try:
            if abs(time.time() - int(timestamp)) > 300:
                log.warning('[teller] webhook replay attack detected')
                return jsonify({'error': 'Timestamp too old'}), 401
        except ValueError:
            pass

        # signed_message = timestamp + "." + raw_body
        signed_message = f'{timestamp}.'.encode() + body
        expected = hmac.new(
            signing_secret.encode(), signed_message, hashlib.sha256
        ).hexdigest()

        if not any(hmac.compare_digest(expected, sig) for sig in signatures):
            log.warning('[teller] webhook signature mismatch')
            return jsonify({'error': 'Invalid signature'}), 401

    # Teller sends GET to verify the endpoint is reachable
    if request.method == 'GET':
        return jsonify({'status': 'ok', 'service': 'pfm-teller-webhook'}), 200

    payload = request.get_json()
    if not payload:
        return jsonify({'error': 'No payload'}), 400

    event_type = payload.get('type', '')
    log.info(f'[teller] webhook received: {event_type}')

    if event_type == 'transactions.processed':
        enrollment_id = payload.get('enrollment_id', '')
        enrollment = TellerEnrollment.query.filter_by(enrollment_id=enrollment_id).first()
        if enrollment:
            # Just log — user syncs manually via UI preview flow
            log.info(f'[teller] new transactions available for enrollment {enrollment_id}')

    return jsonify({'status': 'received'}), 200