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 mobc_redis::redis;
use mobc_redis::redis::AsyncCommands;
use serde_json::json;
use mobc::Pool;
use mobc_redis::RedisConnectionManager;

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

struct RedisScripts {
    edit_post: redis::Script
}

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

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<()> {
        let mut conn = self.redis.get().await?;
        Ok(conn.hdel::<&str, &str, ()>("posts", url).await?)
    }

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

    async fn get_channels(&self, user: &User) -> Result<Vec<MicropubChannel>> {
        let mut conn = self.redis.get().await?;
        let channels = conn.smembers::<String, Vec<String>>("channels_".to_string() + user.me.as_str()).await?;
        // TODO: use streams here instead of this weird thing... how did I even write this?!
        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<_>>())
    }

    async fn put_post<'a>(&self, post: &'a serde_json::Value) -> Result<()> {
        let mut conn = self.redis.get().await?;
        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"))
        }
        conn.hset::<&str, &str, String, ()>(&"posts", key, post.to_string()).await?;
        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 {
                    conn.hset::<&str, &str, String, ()>(&"posts", &url, json!({"see_other": key}).to_string()).await?;
                }
            }
        }
        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.
            conn.sadd::<String, &str, ()>("channels_".to_string() + post["properties"]["author"][0].as_str().unwrap(), key).await?
        }
        Ok(())
    }

    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>> {
        let mut conn = self.redis.get().await?;
        let mut feed;
        match conn.hget::<&str, &str, Option<String>>(&"posts", url).await? {
            Some(post) => feed = serde_json::from_str::<serde_json::Value>(&post)?,
            None => return Ok(None)
        }
        if feed["see_other"].is_string() {
            match conn.hget::<&str, &str, Option<String>>(&"posts", feed["see_other"].as_str().unwrap()).await? {
                Some(post) => feed = serde_json::from_str::<serde_json::Value>(&post)?,
                None => return Ok(None)
            }
        }
        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>;
            // TODO: refactor this to apply the skip on the &mut iterator
            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 {
                    match self.redis.get().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)
                            }
                        },
                        // TODO: Instead of causing a panic, investigate how can you fail the whole stream
                        // Somehow fuse it maybe?
                        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
                // It MUST NOT be a significant amount of the connection pool 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);
            // TODO: Instead of catching panics, find a way to make the whole stream fail with Result<Vec<serde_json::Value>>
            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));
    }

    async fn update_post<'a>(&self, mut url: &'a str, update: serde_json::Value) -> Result<()> {
        let mut conn = self.redis.get().await?;
        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?)?;
        if let Some(new_url) = post["see_other"].as_str() {
            url = new_url
        }
        Ok(SCRIPTS.edit_post.key("posts").arg(url).arg(update.to_string()).invoke_async::<_, ()>(&mut conn as &mut redis::aio::Connection).await?)
    }
}


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: Pool::builder().max_open(20).build(RedisConnectionManager::new(client)) }),
            Err(e) => Err(e.into())
        }
    }
}