import json
from datetime import date, datetime
from flask import (Blueprint, render_template, redirect, url_for,
                   flash, request, current_app, jsonify)
from flask_login import login_required, current_user
from app.extensions import db
from app.models.maintenance import MaintenanceRecord, MAINTENANCE_STATUSES
from app.models.asset import Asset, ASSET_STATUSES
from app.models.audit_log import AuditLog
from app.utils.decorators import editor_required

bp = Blueprint('maintenance', __name__, url_prefix='/maintenance')


def _parse_date(value):
    if not value:
        return None
    if isinstance(value, date):
        return value
    try:
        return date.fromisoformat(value.strip())
    except (ValueError, AttributeError):
        return None


def _log(action, record_id, description, old=None, new=None):
    entry = AuditLog(
        table_name='maintenance_records',
        record_id=record_id,
        action=action,
        old_values=json.dumps(old) if old else None,
        new_values=json.dumps(new) if new else None,
        performed_by_id=current_user.id,
        ip_address=request.remote_addr,
        description=description,
    )
    db.session.add(entry)


# ── List ─────────────────────────────────────────────────────────────────────

@bp.route('/')
@login_required
def index():
    status_filter = request.args.get('status', '')
    asset_filter  = request.args.get('asset_id', type=int)
    page          = request.args.get('page', 1, type=int)

    query = MaintenanceRecord.query.join(MaintenanceRecord.asset)
    if status_filter:
        query = query.filter(MaintenanceRecord.status == status_filter)
    if asset_filter:
        query = query.filter(MaintenanceRecord.asset_id == asset_filter)

    pagination = query.order_by(MaintenanceRecord.start_date.desc()).paginate(
        page=page, per_page=current_app.config['ITEMS_PER_PAGE'], error_out=False
    )

    # Assets available for the "add record" dropdown
    all_assets = Asset.query.order_by(Asset.serial_number).all()

    return render_template(
        'maintenance/index.html',
        pagination=pagination,
        status_filter=status_filter,
        asset_filter=asset_filter,
        statuses=MAINTENANCE_STATUSES,
        all_assets=all_assets,
        edit_record=None,
    )


# ── Create ───────────────────────────────────────────────────────────────────

@bp.route('/new', methods=['POST'])
@login_required
@editor_required
def create():
    asset_id = request.form.get('asset_id', type=int)
    asset = Asset.query.get(asset_id) if asset_id else None
    if not asset:
        flash('Please select a valid asset.', 'danger')
        return redirect(url_for('maintenance.index'))

    start = _parse_date(request.form.get('start_date'))
    if not start:
        flash('Start date is required.', 'danger')
        return redirect(url_for('maintenance.index'))

    record = MaintenanceRecord(
        asset_id          = asset.id,
        start_date        = start,
        end_date          = _parse_date(request.form.get('end_date')),
        status            = request.form.get('status', 'open'),
        initial_diagnosis = request.form.get('initial_diagnosis', '').strip() or None,
        action_taken      = request.form.get('action_taken', '').strip() or None,
        action_result     = request.form.get('action_result', '').strip() or None,
        created_by_id     = current_user.id,
    )
    db.session.add(record)

    # Auto-set asset status to 'maintenance' when a new open record is created
    if record.status in ('open', 'in_progress') and asset.status != 'maintenance':
        asset.status = 'maintenance'

    db.session.flush()
    _log('create', record.id,
         f'Created maintenance record for asset SN={asset.serial_number}',
         new={'asset_id': asset.id, 'status': record.status, 'start_date': str(start)})
    db.session.commit()
    flash(f'Maintenance record added for {asset.serial_number}.', 'success')
    return redirect(url_for('maintenance.index'))


# ── Edit (GET — opens modal pre-filled) ─────────────────────────────────────

@bp.route('/<int:record_id>/edit')
@login_required
@editor_required
def edit(record_id):
    record      = MaintenanceRecord.query.get_or_404(record_id)
    all_assets  = Asset.query.order_by(Asset.serial_number).all()
    status_filter = request.args.get('status', '')
    asset_filter  = request.args.get('asset_id', type=int)
    page          = request.args.get('page', 1, type=int)

    query = MaintenanceRecord.query.join(MaintenanceRecord.asset)
    if status_filter:
        query = query.filter(MaintenanceRecord.status == status_filter)
    if asset_filter:
        query = query.filter(MaintenanceRecord.asset_id == asset_filter)

    pagination = query.order_by(MaintenanceRecord.start_date.desc()).paginate(
        page=page, per_page=current_app.config['ITEMS_PER_PAGE'], error_out=False
    )

    return render_template(
        'maintenance/index.html',
        pagination=pagination,
        status_filter=status_filter,
        asset_filter=asset_filter,
        statuses=MAINTENANCE_STATUSES,
        all_assets=all_assets,
        edit_record=record,
    )


# ── Update ───────────────────────────────────────────────────────────────────

@bp.route('/<int:record_id>/update', methods=['POST'])
@login_required
@editor_required
def update(record_id):
    record = MaintenanceRecord.query.get_or_404(record_id)
    old = {
        'status':            record.status,
        'start_date':        str(record.start_date),
        'end_date':          str(record.end_date) if record.end_date else None,
        'initial_diagnosis': record.initial_diagnosis,
        'action_taken':      record.action_taken,
        'action_result':     record.action_result,
    }

    new_status = request.form.get('status', record.status)
    record.start_date        = _parse_date(request.form.get('start_date')) or record.start_date
    record.end_date          = _parse_date(request.form.get('end_date'))
    record.status            = new_status
    record.initial_diagnosis = request.form.get('initial_diagnosis', '').strip() or None
    record.action_taken      = request.form.get('action_taken', '').strip() or None
    record.action_result     = request.form.get('action_result', '').strip() or None

    # If closed, clear asset's maintenance status (if no other open records)
    if new_status == 'closed' and record.asset:
        other_open = MaintenanceRecord.query.filter(
            MaintenanceRecord.asset_id == record.asset_id,
            MaintenanceRecord.status != 'closed',
            MaintenanceRecord.id != record.id,
        ).first()
        if not other_open and record.asset.status == 'maintenance':
            record.asset.status = 'available'

    _log('update', record.id,
         f'Updated maintenance record id={record_id}', old=old,
         new={'status': record.status, 'end_date': str(record.end_date) if record.end_date else None})
    db.session.commit()
    flash('Maintenance record updated.', 'success')
    return redirect(url_for('maintenance.index'))


# ── Delete ───────────────────────────────────────────────────────────────────

@bp.route('/<int:record_id>/delete', methods=['POST'])
@login_required
@editor_required
def delete(record_id):
    record = MaintenanceRecord.query.get_or_404(record_id)
    asset_sn = record.asset.serial_number if record.asset else '?'
    _log('delete', record.id, f'Deleted maintenance record for asset SN={asset_sn}')
    db.session.delete(record)
    db.session.commit()
    flash('Maintenance record deleted.', 'success')
    return redirect(url_for('maintenance.index'))