#![warn(missing_docs)]
use async_trait::async_trait;
use serde::{Serialize,Deserialize};

#[cfg(test)]
mod memory;
#[cfg(test)]
pub(crate) use crate::database::memory::MemoryStorage;

use crate::indieauth::User;

mod redis;
pub use crate::database::redis::RedisStorage;

#[derive(Serialize, Deserialize, PartialEq, Debug)]
pub struct MicropubChannel {
    pub uid: String,
    pub name: String
}

#[derive(Debug, Clone, Copy)]
pub enum ErrorKind {
    Backend,
    PermissionDenied,
    JSONParsing,
    NotFound,
    BadRequest,
    Other
}

#[derive(Debug)]
pub struct StorageError {
    pub msg: String,
    source: Option<Box<dyn std::error::Error>>,
    pub kind: ErrorKind
}
unsafe impl Send for StorageError {}
unsafe impl Sync for StorageError {}
impl std::error::Error for StorageError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.source.as_ref().map(|e| e.as_ref())
    }
}
impl From<serde_json::Error> for StorageError {
    fn from(err: serde_json::Error) -> Self {
        Self {
            msg: format!("{}", err),
            source: Some(Box::new(err)),
            kind: ErrorKind::JSONParsing
        }
    }
}
impl std::fmt::Display for StorageError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match match self.kind {
            ErrorKind::Backend => write!(f, "backend error: "),
            ErrorKind::JSONParsing => write!(f, "error while parsing JSON: "),
            ErrorKind::PermissionDenied => write!(f, "permission denied: "),
            ErrorKind::NotFound => write!(f, "not found: "),
            ErrorKind::BadRequest => write!(f, "bad request: "),
            ErrorKind::Other => write!(f, "generic storage layer error: ")
        } {
            Ok(_) => write!(f, "{}", self.msg),
            Err(err) => Err(err)
        }
    }
}
impl serde::Serialize for StorageError {
    fn serialize<S: serde::Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {
        serializer.serialize_str(&self.to_string())
    }
}
impl StorageError {
    /// Create a new StorageError of an ErrorKind with a message.
    fn new(kind: ErrorKind, msg: &str) -> Self {
        return StorageError {
            msg: msg.to_string(),
            source: None,
            kind
        }
    }
    /// Get the kind of an error.
    pub fn kind(&self) -> ErrorKind {
        self.kind
    }
}


/// A special Result type for the Micropub backing storage.
pub type Result<T> = std::result::Result<T, StorageError>;

/// A storage backend for the Micropub server.
/// 
/// Implementations should note that all methods listed on this trait MUST be fully atomic
/// or lock the database so that write conflicts or reading half-written data should not occur.
#[async_trait]
pub trait Storage: Clone + Send + Sync {
    /// Check if a post exists in the database.
    async fn post_exists(&self, url: &str) -> Result<bool>;

    /// Load a post from the database in MF2-JSON format, deserialized from JSON.
    async fn get_post(&self, url: &str) -> Result<Option<serde_json::Value>>;

    /// Save a post to the database as an MF2-JSON structure.
    /// 
    /// Note that the `post` object MUST have `post["properties"]["uid"][0]` defined.
    async fn put_post<'a>(&self, post: &'a serde_json::Value) -> Result<()>;

    /*/// Save a post and add it to the relevant feeds listed in `post["properties"]["channel"]`.
    /// 
    /// Note that the `post` object MUST have `post["properties"]["uid"][0]` defined 
    /// and `post["properties"]["channel"]` defined, even if it's empty.
    async fn put_and_index_post<'a>(&mut self, post: &'a serde_json::Value) -> Result<()>;*/
    
    /// Modify a post using an update object as defined in the Micropub spec.
    /// 
    /// Note to implementors: the update operation MUST be atomic OR MUST lock the database
    /// to prevent two clients overwriting each other's changes.
    /// 
    /// You can assume concurrent updates will never contradict each other, since that will be dumb.
    /// The last update always wins.
    async fn update_post<'a>(&self, url: &'a str, update: serde_json::Value) -> Result<()>;

    /// Get a list of channels available for the user represented by the `user` object to write.
    async fn get_channels(&self, user: &User) -> Result<Vec<MicropubChannel>>;

    /// Fetch a feed at `url` and return a an h-feed object containing
    /// `limit` posts after a post by url `after`, filtering the content
    /// in context of a user specified by `user` (or an anonymous user).
    /// 
    /// Specifically, private posts that don't include the user in the audience
    /// will be elided from the feed, and the posts containing location and not
    /// specifying post["properties"]["location-visibility"][0] == "public"
    /// will have their location data (but not check-in data) stripped.
    /// 
    /// This function is used as an optimization so the client, whatever it is,
    /// doesn't have to fetch posts, then realize some of them are private, and
    /// fetch more posts.
    /// 
    /// Note for implementors: if you use streams to fetch posts in parallel
    /// from the database, preferably make this method use a connection pool
    /// to reduce overhead of creating a database connection per post for
    /// parallel fetching.
    async fn read_feed_with_limit<'a>(&self, url: &'a str, after: &'a Option<String>, limit: usize, user: &'a Option<String>) -> Result<Option<serde_json::Value>>;

    /// Deletes a post from the database irreversibly. 'nuff said. Must be idempotent.
    async fn delete_post<'a>(&self, url: &'a str) -> Result<()>;
}

#[cfg(test)]
mod tests {
    use super::{Storage, MicropubChannel};
    use std::{process};
    use std::time::Duration;
    use serde_json::json;

    async fn test_backend_basic_operations<Backend: Storage>(backend: Backend) {
        let post: serde_json::Value = json!({
            "type": ["h-entry"],
            "properties": {
                "content": ["Test content"],
                "author": ["https://fireburn.ru/"],
                "uid": ["https://fireburn.ru/posts/hello"],
                "url": ["https://fireburn.ru/posts/hello", "https://fireburn.ru/posts/test"]
            }
        });
        let key = post["properties"]["uid"][0].as_str().unwrap().to_string();
        let alt_url = post["properties"]["url"][1].as_str().unwrap().to_string();

        // Reading and writing
        backend.put_post(&post).await.unwrap();
        if let Ok(Some(returned_post)) = backend.get_post(&key).await {
            assert!(returned_post.is_object());
            assert_eq!(returned_post["type"].as_array().unwrap().len(), post["type"].as_array().unwrap().len());
            assert_eq!(returned_post["type"].as_array().unwrap(), post["type"].as_array().unwrap());
            let props: &serde_json::Map<String, serde_json::Value> = post["properties"].as_object().unwrap();
            for key in props.keys() {
                assert_eq!(returned_post["properties"][key].as_array().unwrap(), post["properties"][key].as_array().unwrap())
            }
        } else { panic!("For some reason the backend did not return the post.") }
        // Check the alternative URL - it should return the same post
        if let Ok(Some(returned_post)) = backend.get_post(&alt_url).await {
            assert!(returned_post.is_object());
            assert_eq!(returned_post["type"].as_array().unwrap().len(), post["type"].as_array().unwrap().len());
            assert_eq!(returned_post["type"].as_array().unwrap(), post["type"].as_array().unwrap());
            let props: &serde_json::Map<String, serde_json::Value> = post["properties"].as_object().unwrap();
            for key in props.keys() {
                assert_eq!(returned_post["properties"][key].as_array().unwrap(), post["properties"][key].as_array().unwrap())
            }
        } else { panic!("For some reason the backend did not return the post.") }
    }

    async fn test_backend_get_channel_list<Backend: Storage>(backend: Backend) {
        let feed = json!({
            "type": ["h-feed"],
            "properties": {
                "name": ["Main Page"],
                "author": ["https://fireburn.ru/"],
                "uid": ["https://fireburn.ru/feeds/main"]
            },
            "children": []
        });
        backend.put_post(&feed).await.unwrap();
        let chans = backend.get_channels(&crate::indieauth::User::new("https://fireburn.ru/", "https://quill.p3k.io/", "create update media")).await.unwrap();
        assert_eq!(chans.len(), 1);
        assert_eq!(chans[0], MicropubChannel { uid: "https://fireburn.ru/feeds/main".to_string(), name: "Main Page".to_string() });
    }

    #[async_std::test]
    async fn test_memory_storage_basic_operations() {
        let backend = super::MemoryStorage::new();
        test_backend_basic_operations(backend).await
    }
    #[async_std::test]
    async fn test_memory_storage_channel_support() {
        let backend = super::MemoryStorage::new();
        test_backend_get_channel_list(backend).await
    }

    async fn get_redis_backend() -> (tempdir::TempDir, process::Child, super::RedisStorage) {
        let tempdir = tempdir::TempDir::new("redis").expect("failed to create tempdir");
        let socket = tempdir.path().join("redis.sock");
        let redis_child = process::Command::new("redis-server")
            .current_dir(&tempdir)
            .arg("--port").arg("0")
            .arg("--unixsocket").arg(&socket)
            .stdout(process::Stdio::null())
            .stderr(process::Stdio::null())
            .spawn().expect("Failed to spawn Redis");
        println!("redis+unix:///{}", socket.to_str().unwrap());
        let uri = format!("redis+unix:///{}", socket.to_str().unwrap());
        // There should be a slight delay, we need to wait for Redis to spin up
        let client = redis::Client::open(uri.clone()).unwrap();
        let millisecond = Duration::from_millis(1);
        let mut retries: usize = 0;
        const MAX_RETRIES: usize = 10 * 1000/*ms*/;
        while let Err(err) = client.get_connection() {
            if err.is_connection_refusal() {
                async_std::task::sleep(millisecond).await;
                retries += 1;
                if retries > MAX_RETRIES {
                    panic!("Timeout waiting for Redis, last error: {}", err);
                }
            } else {
                panic!("Could not connect: {}", err);
            }
        }
        let backend = super::RedisStorage::new(uri).await.unwrap();

        return (tempdir, redis_child, backend)
    }

    #[async_std::test]
    async fn test_redis_storage_basic_operations() {
        let (_, mut redis, backend) = get_redis_backend().await;
        test_backend_basic_operations(backend).await;
        redis.kill().expect("Redis wasn't running");
    }
    #[async_std::test]
    async fn test_redis_storage_channel_support() {
        let (_, mut redis, backend) = get_redis_backend().await;
        test_backend_get_channel_list(backend).await;
        redis.kill().expect("Redis wasn't running");
    }
}