#![allow(unused_variables)]
use async_trait::async_trait;
use lazy_static::lazy_static;
#[cfg(test)]
use std::collections::HashMap;
#[cfg(test)]
use std::sync::Arc;
#[cfg(test)]
use async_std::sync::RwLock;
use log::error;
use futures::stream;
use futures_util::FutureExt;
use futures_util::StreamExt;
use serde::{Serialize,Deserialize};
use serde_json::json;
use redis;
use redis::AsyncCommands;

use crate::indieauth::User;

#[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,
    Other
}

// TODO get rid of your own errors and use a crate?
#[derive(Debug)]
pub struct StorageError {
    msg: String,
    source: Option<Box<dyn std::error::Error>>,
    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<redis::RedisError> for StorageError {
    fn from(err: redis::RedisError) -> Self {
        Self {
            msg: format!("{}", err),
            source: Some(Box::new(err)),
            kind: ErrorKind::Backend
        }
    }
}
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::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 {
    fn new(kind: ErrorKind, msg: &str) -> Self {
        return StorageError {
            msg: msg.to_string(),
            source: None,
            kind
        }
    }
    pub fn kind(&self) -> ErrorKind {
        self.kind
    }
}

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)]
#[derive(Clone)]
pub struct MemoryStorage {
    pub mapping: Arc<RwLock<HashMap<String, serde_json::Value>>>,
    pub channels: Arc<RwLock<HashMap<String, Vec<String>>>>
}

#[cfg(test)]
#[async_trait]
impl Storage for MemoryStorage {
    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>> {
        todo!()
    }

    async fn update_post<'a>(&self, url: &'a str, update: serde_json::Value) -> Result<()> {
        todo!()
    }

    async fn delete_post<'a>(&self, url: &'a str) -> Result<()> {
        self.mapping.write().await.remove(url);
        Ok(())
    }

    async fn post_exists(&self, url: &str) -> Result<bool> {
        return Ok(self.mapping.read().await.contains_key(url))
    }

    async fn get_post(&self, url: &str) ->Result<Option<serde_json::Value>> {
        let mapping = self.mapping.read().await;
        match mapping.get(url) {
            Some(val) => {
                if let Some(new_url) = val["see_other"].as_str() {
                    match mapping.get(new_url) {
                        Some(val) => Ok(Some(val.clone())),
                        None => {
                            drop(mapping);
                            self.mapping.write().await.remove(url);
                            Ok(None)
                        }
                    }
                } else {
                    Ok(Some(val.clone()))
                }
            },
            _ => Ok(None)
        }
    }

    async fn get_channels(&self, user: &User) -> Result<Vec<MicropubChannel>> {
        match self.channels.read().await.get(&user.me.to_string()) {
            Some(channels) => Ok(futures_util::future::join_all(channels.iter()
                .map(|channel| self.get_post(channel)
                    .map(|result| result.unwrap())
                    .map(|post: Option<serde_json::Value>| {
                        if let Some(post) = post {
                            Some(MicropubChannel {
                                uid: post["properties"]["uid"][0].as_str().unwrap().to_string(),
                                name: post["properties"]["name"][0].as_str().unwrap().to_string()
                            })
                        } else { None }
                    })
                ).collect::<Vec<_>>()).await.into_iter().filter_map(|chan| chan).collect::<Vec<_>>()),
            None => Ok(vec![])
        }
        
    }

    async fn put_post<'a>(&self, post: &'a serde_json::Value) -> Result<()> {
        let mapping = &mut self.mapping.write().await;
        let key: &str;
        match post["properties"]["uid"][0].as_str() {
            Some(uid) => key = uid,
            None => return Err(StorageError::new(ErrorKind::Other, "post doesn't have a UID"))
        }
        mapping.insert(key.to_string(), post.clone());
        if post["properties"]["url"].is_array() {
            for url in post["properties"]["url"].as_array().unwrap().iter().map(|i| i.as_str().unwrap().to_string()) {
                if &url != key {
                    mapping.insert(url, json!({"see_other": key}));
                }
            }
        }
        if post["type"].as_array().unwrap().iter().any(|i| i == "h-feed") {
            // This is a feed. Add it to the channels array if it's not already there.
            println!("{:#}", post);
            self.channels.write().await.entry(post["properties"]["author"][0].as_str().unwrap().to_string()).or_insert(vec![]).push(key.to_string())
        }
        Ok(())
    }
}
#[cfg(test)]
impl MemoryStorage {
    pub fn new() -> Self {
        Self {
            mapping: Arc::new(RwLock::new(HashMap::new())),
            channels: Arc::new(RwLock::new(HashMap::new()))
        }
    }
}

struct RedisScripts {
    edit_post: redis::Script
}

lazy_static! {
    static ref SCRIPTS: RedisScripts = RedisScripts {
        edit_post: redis::Script::new(include_str!("./edit_post.lua"))
    };
}

#[derive(Clone)]
pub struct RedisStorage {
    // TODO: use mobc crate to create a connection pool and reuse connections for efficiency
    redis: redis::Client,
}

fn filter_post<'a>(mut post: serde_json::Value, user: &'a Option<String>) -> Option<serde_json::Value> {
    if post["properties"]["deleted"][0].is_string() {
        return Some(json!({
            "type": post["type"],
            "properties": {
                "deleted": post["properties"]["deleted"]
            }
        }));
    }
    let empty_vec: Vec<serde_json::Value> = vec![];
    let author = post["properties"]["author"].as_array().unwrap_or(&empty_vec).iter().map(|i| i.as_str().unwrap().to_string());
    let visibility = post["properties"]["visibility"][0].as_str().unwrap_or("public");
    let mut audience = author.chain(post["properties"]["audience"].as_array().unwrap_or(&empty_vec).iter().map(|i| i.as_str().unwrap().to_string()));
    if visibility == "private" {
        if !audience.any(|i| Some(i) == *user) {
            return None
        }
    }
    if post["properties"]["location"].is_array() {
        let location_visibility = post["properties"]["location-visibility"][0].as_str().unwrap_or("private");
        let mut author = post["properties"]["author"].as_array().unwrap_or(&empty_vec).iter().map(|i| i.as_str().unwrap().to_string());
        if location_visibility == "private" && !author.any(|i| Some(i) == *user) {
            post["properties"].as_object_mut().unwrap().remove("location");
        }
    }
    Some(post)
}

#[async_trait]
impl Storage for RedisStorage {
    async fn delete_post<'a>(&self, url: &'a str) -> Result<()> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => if let Err(err) = conn.hdel::<&str, &str, bool>("posts", url).await {
                return Err(err.into());
            },
            Err(err) => return Err(err.into())
        }
        Ok(())
    }

    async fn post_exists(&self, url: &str) -> Result<bool> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => match conn.hexists::<&str, &str, bool>(&"posts", url).await {
                Ok(val) => Ok(val),
                Err(err) => Err(err.into())
            },
            Err(err) => Err(err.into())
        }
    }
    
    async fn get_post(&self, url: &str) -> Result<Option<serde_json::Value>> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => match conn.hget::<&str, &str, Option<String>>(&"posts", url).await {
                Ok(val) => match val {
                    Some(val) => match serde_json::from_str::<serde_json::Value>(&val) {
                        Ok(parsed) => if let Some(new_url) = parsed["see_other"].as_str() {
                            match conn.hget::<&str, &str, Option<String>>(&"posts", new_url).await {
                                Ok(val) => match val {
                                    Some(val) => match serde_json::from_str::<serde_json::Value>(&val) {
                                        Ok(parsed) => Ok(Some(parsed)),
                                        Err(err) => Err(err.into())
                                    },
                                    None => Ok(None)
                                }
                                Err(err) => {
                                    Ok(None)
                                }
                            }
                        } else {
                            Ok(Some(parsed))
                        },
                        Err(err) => Err(err.into())
                    },
                    None => Ok(None)
                },
                Err(err) => Err(err.into())
            },
            Err(err) => Err(err.into())
        }
    }

    async fn get_channels(&self, user: &User) -> Result<Vec<MicropubChannel>> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => match conn.smembers::<String, Vec<String>>("channels_".to_string() + user.me.as_str()).await {
                Ok(channels) => {
                    Ok(futures_util::future::join_all(channels.iter()
                        .map(|channel| self.get_post(channel)
                            .map(|result| result.unwrap())
                            .map(|post: Option<serde_json::Value>| {
                                if let Some(post) = post {
                                    Some(MicropubChannel {
                                        uid: post["properties"]["uid"][0].as_str().unwrap().to_string(),
                                        name: post["properties"]["name"][0].as_str().unwrap().to_string()
                                    })
                                } else { None }
                            })
                        ).collect::<Vec<_>>()).await.into_iter().filter_map(|chan| chan).collect::<Vec<_>>())
                },
                Err(err) => Err(err.into())
            },
            Err(err) => Err(err.into())
        }
    }

    async fn put_post<'a>(&self, post: &'a serde_json::Value) -> Result<()> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => {
                let key: &str;
                match post["properties"]["uid"][0].as_str() {
                    Some(uid) => key = uid,
                    None => return Err(StorageError::new(ErrorKind::Other, "post doesn't have a UID"))
                }        
                match conn.hset::<&str, &str, String, ()>(&"posts", key, post.to_string()).await {
                    Err(err) => return Err(err.into()),
                    _ => {}
                }
                if post["properties"]["url"].is_array() {
                    for url in post["properties"]["url"].as_array().unwrap().iter().map(|i| i.as_str().unwrap().to_string()) {
                        if &url != key {
                            match conn.hset::<&str, &str, String, ()>(&"posts", &url, json!({"see_other": key}).to_string()).await {
                                Err(err) => return Err(err.into()),
                                _ => {}
                            }
                        }
                    }
                }
                if post["type"].as_array().unwrap().iter().any(|i| i == "h-feed") {
                    // This is a feed. Add it to the channels array if it's not already there.
                    match conn.sadd::<String, &str, ()>("channels_".to_string() + post["properties"]["author"][0].as_str().unwrap(), key).await {
                        Err(err) => return Err(err.into()),
                        _ => {},
                    }
                }
                Ok(())
            },
            Err(err) => Err(err.into())
        }
    }

    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>> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => {
                let mut feed;
                match conn.hget::<&str, &str, Option<String>>(&"posts", url).await {
                    Ok(post) => {
                        match post {
                            Some(post) => match serde_json::from_str::<serde_json::Value>(&post) {
                                Ok(post) => feed = post,
                                Err(err) => return Err(err.into())
                            },
                            None => return Ok(None)
                        }
                    },
                    Err(err) => return Err(err.into())
                }
                if feed["see_other"].is_string() {
                    match conn.hget::<&str, &str, Option<String>>(&"posts", feed["see_other"].as_str().unwrap()).await {
                        Ok(post) => {
                            match post {
                                Some(post) => match serde_json::from_str::<serde_json::Value>(&post) {
                                    Ok(post) => feed = post,
                                    Err(err) => return Err(err.into())
                                },
                                None => return Ok(None)
                            }
                        },
                        Err(err) => return Err(err.into())
                    }
                }
                if let Some(post) = filter_post(feed, user) {
                    feed = post
                } else {
                    return Err(StorageError::new(ErrorKind::PermissionDenied, "specified user cannot access this post"))
                }
                if feed["children"].is_array() {
                    let children = feed["children"].as_array().unwrap();
                    let posts_iter: Box<dyn std::iter::Iterator<Item = String> + Send>;
                    if let Some(after) = after {
                        posts_iter = Box::new(children.iter().map(|i| i.as_str().unwrap().to_string()).skip_while(move |i| i != after).skip(1));
                    } else {
                        posts_iter = Box::new(children.iter().map(|i| i.as_str().unwrap().to_string()));
                    }
                    let posts = stream::iter(posts_iter)
                        .map(|url| async move {
                            // Is it rational to use a new connection for every post fetched?
                            match self.redis.get_async_std_connection().await {
                                Ok(mut conn) => match conn.hget::<&str, &str, Option<String>>("posts", &url).await {
                                    Ok(post) => match post {
                                        Some(post) => match serde_json::from_str::<serde_json::Value>(&post) {
                                            Ok(post) => Some(post),
                                            Err(err) => {
                                                let err = StorageError::from(err);
                                                error!("{}", err);
                                                panic!("{}", err)
                                            }
                                        },
                                        // Happens because of a broken link (result of an improper deletion?)
                                        None => None,
                                    },
                                    Err(err) => {
                                        let err = StorageError::from(err);
                                        error!("{}", err);
                                        panic!("{}", err)
                                    }
                                },
                                Err(err) => {
                                    let err = StorageError::from(err);
                                    error!("{}", err);
                                    panic!("{}", err)
                                }
                            }
                        })
                        // TODO: determine the optimal value for this buffer
                        // It will probably depend on how often can you encounter a private post on the page
                        // It shouldn't be too large, or we'll start fetching too many posts from the database
                        // It MUST NOT be larger than the typical page size
                        .buffered(std::cmp::min(3, limit))
                        // Hack to unwrap the Option and sieve out broken links
                        // Broken links return None, and Stream::filter_map skips all Nones.
                        .filter_map(|post: Option<serde_json::Value>| async move { post })
                        .filter_map(|post| async move {
                            return filter_post(post, user)
                        })
                        .take(limit);
                    match std::panic::AssertUnwindSafe(posts.collect::<Vec<serde_json::Value>>()).catch_unwind().await {
                        Ok(posts) => feed["children"] = json!(posts),
                        Err(err) => return Err(StorageError::new(ErrorKind::Other, "Unknown error encountered while assembling feed, see logs for more info"))
                    }
                }
                return Ok(Some(feed));
            }
            Err(err) => Err(err.into())
        }
    }

    async fn update_post<'a>(&self, mut url: &'a str, update: serde_json::Value) -> Result<()> {
        match self.redis.get_async_std_connection().await {
            Ok(mut conn) => {
                if !conn.hexists::<&str, &str, bool>("posts", url).await.unwrap() {
                    return Err(StorageError::new(ErrorKind::NotFound, "can't edit a non-existent post"))
                }
                let post: serde_json::Value = serde_json::from_str(&conn.hget::<&str, &str, String>("posts", url).await.unwrap()).unwrap();
                if let Some(new_url) = post["see_other"].as_str() {
                    url = new_url
                }
                if let Err(err) = SCRIPTS.edit_post.key("posts").arg(url).arg(update.to_string()).invoke_async::<_, ()>(&mut conn).await {
                    return Err(err.into())
                }
            },
            Err(err) => return Err(err.into())
        }
        Ok(())
    }
}


impl RedisStorage {
    /// Create a new RedisDatabase that will connect to Redis at `redis_uri` to store data.
    pub async fn new(redis_uri: String) -> Result<Self> {
        match redis::Client::open(redis_uri) {
            Ok(client) => Ok(Self { redis: client }),
            Err(e) => Err(e.into())
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{Storage, MicropubChannel};
    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_channel_support<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": []
        });
        let key = feed["properties"]["uid"][0].as_str().unwrap().to_string();
        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_channel_support(backend).await
    }

    #[async_std::test]
    #[ignore]
    async fn test_redis_storage_basic_operations() {
        let backend = super::RedisStorage::new(std::env::var("REDIS_URI").unwrap_or("redis://127.0.0.1:6379/0".to_string())).await.unwrap();
        redis::cmd("FLUSHDB").query_async::<_, ()>(&mut backend.redis.get_async_std_connection().await.unwrap()).await.unwrap();
        test_backend_basic_operations(backend).await
    }
    #[async_std::test]
    #[ignore]
    async fn test_redis_storage_channel_support() {
        let backend = super::RedisStorage::new(std::env::var("REDIS_URI").unwrap_or("redis://127.0.0.1:6379/1".to_string())).await.unwrap();
        redis::cmd("FLUSHDB").query_async::<_, ()>(&mut backend.redis.get_async_std_connection().await.unwrap()).await.unwrap();
        test_backend_channel_support(backend).await
    }
}