import os
import logging
from io import BytesIO
from typing import Any, Mapping

from django.core.files import File
from django.conf import settings
from django.template import Template, Context
from django.utils.text import slugify

from labs.models import CertificateIssuance, CertificateType
from labs.certificate.exceptions import CertificateFileGenerationError

logger = logging.getLogger(__name__)


# Remove this function after we have migrated all the certificates from tlms to labs.
def deprecated_upload_certificate_file_to_aliyun_oss(
    file_path: str, file: File
) -> None:
    import opendal
    retry_layer = opendal.layers.RetryLayer(max_times=3, factor=2.0, jitter=True)
    operator = opendal.Operator(
        "oss",
        bucket=settings.ALIYUN_OSS_BUCKET,
        endpoint=f"https://oss-{settings.ALIYUN_OSS_REGION}.aliyuncs.com",
        access_key_id=settings.ALIYUN_OSS_ACCESS_KEY_ID,
        access_key_secret=settings.ALIYUN_OSS_ACCESS_KEY_SECRET,
    ).layer(retry_layer)

    file.seek(0)
    operator.write(file_path, file.read(), content_type="application/pdf")


class CertificateStorage:
    storage_provider: str
    issuance: CertificateIssuance

    def __init__(self, issuance: CertificateIssuance):
        self.issuance = issuance

    def get_file_path(self) -> str:
        cert_type: CertificateType = self.issuance.cert_type
        cert_number: str = self.issuance.cert_number
        file_path = f"certificates/{slugify(f'{cert_type.short_name}_{cert_number}')}.pdf"
        if settings.DEBUG:
            file_path = f"debug/{file_path}"
        return file_path

    def save(self, file: File, content_type: str) -> None:
        raise NotImplementedError("Subclass must implement this method")


class CeritificateOSSStorage(CertificateStorage):
    storage_provider = "aliyun"

    def save(self, file: File, content_type: str) -> None:
        import opendal

        retry_layer = opendal.layers.RetryLayer(max_times=3, factor=2.0, jitter=True)
        operator = opendal.Operator(
            "oss",
            bucket=settings.ALIYUN_OSS_BUCKET,
            endpoint=f"https://oss-{settings.ALIYUN_OSS_REGION}.aliyuncs.com",
            access_key_id=settings.ALIYUN_OSS_ACCESS_KEY_ID,
            access_key_secret=settings.ALIYUN_OSS_ACCESS_KEY_SECRET,
        ).layer(retry_layer)

        file.seek(0)
        file_path = self.get_file_path()
        operator.write(file_path, file.read(), content_type=content_type)
        self.issuance.file_storage_provider = self.storage_provider
        self.issuance.file_bucket = settings.ALIYUN_OSS_BUCKET
        self.issuance.file_object_key = file_path
        self.issuance.file_content_type = content_type
        self.issuance.save()


class CertificateLocalStorage(CertificateStorage):
    storage_provider = "local"
    local_storage_path = "labs/certificates_local_storage/"

    def get_file_path(self) -> str:
        cert_type: CertificateType = self.issuance.cert_type
        cert_number: str = self.issuance.cert_number
        file_name = slugify(f"{cert_type.short_name}_{cert_number}") + ".pdf"
        return f"{self.local_storage_path}{file_name}"

    def save(self, file: File, content_type: str) -> None:
        file.seek(0)
        file_path = self.get_file_path()
        if not os.path.exists(os.path.dirname(file_path)):
            os.makedirs(os.path.dirname(file_path))
        with open(file_path, "wb") as f:
            f.write(file.read())
        self.issuance.file_storage_provider = self.storage_provider
        self.issuance.file_bucket = ""
        self.issuance.file_object_key = file_path
        self.issuance.file_content_type = content_type
        self.issuance.save()


def get_storage_provider(storage_provider: str) -> CertificateStorage:
    if storage_provider == "aliyun":
        return CeritificateOSSStorage
    elif storage_provider == "local":
        return CertificateLocalStorage
    else:
        raise ValueError(f"Invalid storage provider: {storage_provider}")


def render_certificate_pdf(template_str: str, context: Mapping[str, Any]) -> bytes:
    from weasyprint import HTML
    from weasyprint.text.fonts import FontConfiguration

    template = Template(template_str)
    html = template.render(Context(dict(context)))
    font_config = FontConfiguration()
    return HTML(string=html).write_pdf(font_config=font_config)


def generate_issuance_pdf(issuance: CertificateIssuance):
    # generate_issuance_pdf is used to generate a PDF file for a certificate issuance record and upload it to Aliyun OSS.
    # Raise `CertificateFileGenerationError` if failed to generate the PDF file.
    cert_type = issuance.cert_type
    if not cert_type.template:
        raise CertificateFileGenerationError(
            f"Certificate type {cert_type.short_name} does not have a template"
        )

    pdf = render_certificate_pdf(
        cert_type.template,
        {
            "name": issuance.recipient.first_name + " " + issuance.recipient.last_name,
            "issued_at": issuance.issued_at.strftime("%d/%m/%Y"),
            "certificate_number": issuance.cert_number.upper(),
        },
    )
    pdf_file = BytesIO(pdf)
    content_type = "application/pdf"

    storage: CertificateStorage = get_storage_provider(
        settings.CERTIFICATE_STORAGE_PROVIDER
    )(issuance)
    storage.save(pdf_file, content_type)
    logger.info(
        f"Successfully generated certificate PDF file for issuance {issuance.id}"
    )