use async_trait::async_trait;
use futures_util::FutureExt;
use futures_util::StreamExt;
use futures::stream;
use lazy_static::lazy_static;
use log::error;
use redis::AsyncCommands;
use serde_json::json;

use crate::database::{Storage, Result, StorageError, ErrorKind, MicropubChannel};
use crate::indieauth::User;

struct RedisScripts {
    edit_post: redis::Script
}

impl From<redis::RedisError> for StorageError {
    fn from(err: redis::RedisError) -> Self {
        Self {
            msg: format!("{}", err),
            source: Some(Box::new(err)),
            kind: ErrorKind::Backend
        }
    }
}

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(mut post: serde_json::Value, user: &'_ 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" && !audience.any(|i| Some(i) == *user)) || (visibility == "protected" && user.is_none()) {
        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) => {
                                    Err(err.into())
                                }
                            }
                        } 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::BadRequest, "post doesn't have a UID"))
                }        
                if let Err(err) = conn.hset::<&str, &str, String, ()>(&"posts", key, post.to_string()).await {
                    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 {
                            if let Err(err) = conn.hset::<&str, &str, String, ()>(&"posts", &url, json!({"see_other": key}).to_string()).await {
                                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.
                    if let Err(err) = conn.sadd::<String, &str, ()>("channels_".to_string() + post["properties"]["author"][0].as_str().unwrap(), key).await {
                        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 {
                            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(_) => 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())
        }
    }
}