use async_trait::async_trait;
use axum::extract::multipart::Field;
use tokio_stream::Stream;
use bytes::Bytes;
use serde::{Deserialize, Serialize};
use std::pin::Pin;
use std::fmt::Debug;
use std::num::NonZeroUsize;

pub mod file;

#[derive(Debug, Deserialize, Serialize)]
pub struct Metadata {
    /// Content type of the file. If None, the content-type is considered undefined.
    pub content_type: Option<String>,
    /// The original filename that was passed.
    pub filename: Option<String>,
    /// The recorded length of the file.
    pub length: Option<NonZeroUsize>,
    /// The e-tag of a file. Note: it must be a strong e-tag, for example, a hash.
    pub etag: Option<String>,
}
impl From<&Field<'_>> for Metadata {
    fn from(field: &Field<'_>) -> Self {
        Self {
            content_type: field.content_type()
                .map(|i| i.to_owned()),
            filename: field.file_name()
                .map(|i| i.to_owned()),
            length: None,
            etag: None,
        }
    }
}


#[derive(Debug, Clone, Copy)]
pub enum ErrorKind {
    Backend,
    Permission,
    Json,
    NotFound,
    Other,
}

#[derive(Debug)]
pub struct MediaStoreError {
    kind: ErrorKind,
    source: Option<Box<dyn std::error::Error + Send + Sync>>,
    msg: String,
}

impl MediaStoreError {
    pub fn kind(&self) -> ErrorKind {
        self.kind
    }
}

impl std::error::Error for MediaStoreError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.source
            .as_ref()
            .map(|i| i.as_ref() as &dyn std::error::Error)
    }
}

impl std::fmt::Display for MediaStoreError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}: {}",
            match self.kind {
                ErrorKind::Backend => "media storage backend error",
                ErrorKind::Permission => "permission denied",
                ErrorKind::Json => "failed to parse json",
                ErrorKind::NotFound => "blob not found",
                ErrorKind::Other => "unknown media storage error",
            },
            self.msg
        )
    }
}

pub type Result<T> = std::result::Result<T, MediaStoreError>;

#[async_trait]
pub trait MediaStore: 'static + Send + Sync + Clone {
    async fn write_streaming<T>(
        &self,
        domain: &str,
        metadata: Metadata,
        content: T,
    ) -> Result<String>
    where
        T: tokio_stream::Stream<Item = std::result::Result<bytes::Bytes, axum::extract::multipart::MultipartError>> + Unpin + Send + Debug;

    async fn read_streaming(
        &self,
        domain: &str,
        filename: &str,
    ) -> Result<(Metadata, Pin<Box<dyn Stream<Item = std::io::Result<Bytes>> + Send>>)>;

    async fn delete(&self, domain: &str, filename: &str) -> Result<()>;
}