import uuid
from io import BytesIO

from flask import (
    current_app,
    flash,
    redirect,
    render_template,
    request,
    url_for,
)
from notifications_utils.pdf import pdf_page_count
from PyPDF2.utils import PdfReadError
from requests import RequestException

from app import current_service
from app.extensions import antivirus_client
from app.main import main
from app.main.forms import PDFUploadForm
from app.s3_client.s3_letter_upload_client import (
    get_transient_letter_file_location,
    upload_letter_to_s3,
)
from app.template_previews import sanitise_letter
from app.utils import user_has_permissions

MAX_FILE_UPLOAD_SIZE = 2 * 1024 * 1024  # 2MB


@main.route("/services/<service_id>/uploads")
@user_has_permissions('send_messages')
def uploads(service_id):
    return render_template('views/uploads/index.html')


@main.route("/services/<service_id>/upload-letter", methods=['GET', 'POST'])
@user_has_permissions('send_messages')
def upload_letter(service_id):
    form = PDFUploadForm()

    if form.validate_on_submit():
        pdf_file_bytes = form.file.data.read()

        virus_free = antivirus_client.scan(BytesIO(pdf_file_bytes))
        if not virus_free:
            return invalid_upload_error('Your file has failed the virus check')

        if len(pdf_file_bytes) > MAX_FILE_UPLOAD_SIZE:
            return invalid_upload_error('Your file must be smaller than 2MB')

        try:
            pdf_page_count(BytesIO(pdf_file_bytes))
        except PdfReadError:
            current_app.logger.info('Invalid PDF uploaded for service_id: {}'.format(service_id))
            return invalid_upload_error('Your file must be a valid PDF')

        upload_id = uuid.uuid4()
        file_location = get_transient_letter_file_location(service_id, upload_id)

        try:
            response = sanitise_letter(BytesIO(pdf_file_bytes))
            response.raise_for_status()
        except RequestException as ex:
            if ex.response is not None and ex.response.status_code == 400:
                status = 'invalid'
                upload_letter_to_s3(pdf_file_bytes, file_location, status)
            else:
                raise ex
        else:
            status = 'valid'
            upload_letter_to_s3(response.content, file_location, status)

        return redirect(
            url_for(
                'main.uploaded_letter_preview',
                service_id=current_service.id,
                file_id=upload_id,
                original_filename=form.file.data.filename,
                status=status,
            )
        )

    return render_template('views/uploads/choose-file.html', form=form)


def invalid_upload_error(message):
    flash(message, 'dangerous')
    return render_template('views/uploads/choose-file.html', form=PDFUploadForm()), 400


@main.route("/services/<service_id>/preview-letter/<file_id>")
@user_has_permissions('send_messages')
def uploaded_letter_preview(service_id, file_id):
    original_filename = request.args.get('original_filename')
    status = request.args.get('status')

    return render_template('views/uploads/preview.html', original_filename=original_filename, status=status)