use async_std::{
    channel::{unbounded, Receiver, Sender},
    path::PathBuf,
    task::spawn,
};
use std::{collections::HashMap, error::Error, fmt};

const ENTRY: &str = "EntryPoint";

#[derive(Debug)]
enum ErrorCode {
    Undefined(String),
    IncorrectDataType(String),
}

impl fmt::Display for ErrorCode {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            ErrorCode::Undefined(msg) => write!(f, "{}", msg),
            ErrorCode::IncorrectDataType(item) => write!(f, "data type '{}' does not exist", item),
        }
    }
}

mod errorcodes {
    use super::*;

    const ITEMS: [&str; 2] = ["one", "two"];

    #[test]
    fn undefined_display() {
        for item in ITEMS {
            let err = ErrorCode::Undefined(item.to_string());
            assert_eq!(err.to_string(), item);
        }
    }

    #[test]
    fn incorrect_data_type() {
        for item in ITEMS {
            let err = ErrorCode::IncorrectDataType(item.to_string());
            assert_eq!(
                err.to_string(),
                format!("data type '{}' does not exist", item)
            );
        }
    }
}

#[derive(Debug)]
pub struct MTTError {
    code: ErrorCode,
}

impl MTTError {
    fn new<S>(msg: S) -> Self
    where
        S: Into<String>,
    {
        let text = msg.into();
        Self {
            code: ErrorCode::Undefined(text),
        }
    }

    fn from_code(code: ErrorCode) -> Self {
        Self { code: code }
    }
}

impl Error for MTTError {}

impl fmt::Display for MTTError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.code)
    }
}

#[cfg(test)]
mod errors {
    use super::*;

    #[test]
    fn create_with_str() {
        let msgs = ["one", "two"];
        for msg in msgs {
            let err = MTTError::new(msg);
            assert_eq!(err.to_string(), msg);
        }
    }

    #[test]
    fn create_with_string() {
        let msg = "three";
        let err = MTTError::new(msg.to_string());
        assert_eq!(err.to_string(), msg);
    }

    #[test]
    fn create_from_code() {
        let code = ErrorCode::Undefined("oops".to_string());
        let err = MTTError::from_code(code);
        match err.code {
            ErrorCode::Undefined(_) => (),
            _ => assert!(false, "{:?} is not undefined", err.code),
        }
    }

    #[test]
    fn create_from_different_code() {
        let code = ErrorCode::IncorrectDataType("nuts".to_string());
        let err = MTTError::from_code(code);
        match err.code {
            ErrorCode::IncorrectDataType(_) => (),
            _ => assert!(false, "{:?} is not incorrect data type", err.code),
        }
    }
}

#[derive(Clone, Debug)]
struct Store;

impl Store {
    fn new() -> Self {
        Self {}
    }
}

#[cfg(test)]
mod stores {
    use super::*;

    #[test]
    fn create() {
        Store::new();
    }
}

#[derive(Clone, Debug)]
enum DataType {
    DBMap(Store),
}

impl DataType {
    fn new(dtype: &str) -> Result<DataType, MTTError> {
        match dtype {
            "store" => Ok(Self::DBMap(Store::new())),
            _ => Err(MTTError::from_code(ErrorCode::IncorrectDataType(
                dtype.to_string(),
            ))),
        }
    }
}

#[cfg(test)]
mod datatypes {
    use super::*;

    #[test]
    fn error_on_bad_datatype() {
        let items = ["sdgthsth", "jfjty"];
        for item in items {
            match DataType::new(item) {
                Ok(_) => assert!(false, "bad data types should return an error"),
                Err(err) => match err.code {
                    ErrorCode::IncorrectDataType(dtype) => assert_eq!(dtype, item),
                    _ => assert!(false, "{:?} is not incorrect data type", err.code),
                },
            }
        }
    }

    #[test]
    fn create_store() {
        let dtype = DataType::new("store").unwrap();
        match dtype {
            DataType::DBMap(_) => (),
            _ => assert!(false, "{:?} is not incorrect data type", dtype),
        }
    }
}

#[derive(Debug)]
enum FromCache {
    Data(HashMap<String, DataType>),
    Error(MTTError),
}

struct CacheQuery {
    ids: Vec<String>,
    reply: Sender<FromCache>,
}

enum ToCache {
    Query(CacheQuery),
}

#[derive(Clone)]
pub struct MoreThanText {
    session: Vec<String>,
    cache: Sender<Vec<String>>,
}

impl MoreThanText {
    async fn new(cache: Sender<Vec<String>>) -> Result<Self, MTTError> {
        Ok(Self {
            session: [ENTRY.to_string()].to_vec(),
            cache: cache,
        })
    }
}

#[cfg(test)]
mod mtt {
    use super::*;

    #[async_std::test]
    async fn create() {
        let (s, _) = unbounded();
        let mtt = MoreThanText::new(s).await.unwrap();
        assert_eq!(mtt.session, [ENTRY]);
    }
}

struct Cache {
    channel: Receiver<ToCache>,
}

impl Cache {
    async fn new<P>(_dir: P, channel: Receiver<ToCache>) -> Result<Self, MTTError>
    where
        P: Into<PathBuf>,
    {
        Ok(Self { channel: channel })
    }

    async fn start(&self) {
        loop {
            match self.channel.recv().await.unwrap() {
                ToCache::Query(data) => {
                    for id in data.ids {
                        if id == ENTRY {
                            let mut holder = HashMap::new();
                            holder.insert(ENTRY.to_string(), DataType::new("store").unwrap());
                            data.reply.send(FromCache::Data(holder)).await.unwrap();
                        } else {
                            data.reply
                                .send(FromCache::Error(MTTError::new("fred")))
                                .await
                                .unwrap();
                        }
                    }
                }
            }
        }
    }
}

#[cfg(test)]
mod caches {
    use super::*;
    use tempfile::tempdir;

    async fn start_cache<P>(dir: P) -> Sender<ToCache>
    where
        P: Into<PathBuf>,
    {
        let (s, r) = unbounded();
        let datadir = dir.into();
        spawn(async move {
            let cache = Cache::new(datadir, r).await.unwrap();
            cache.start().await;
        });
        s
    }

    async fn send_request(data: Vec<&str>, channel: Sender<ToCache>) -> FromCache {
        let mut ids = Vec::new();
        for id in data.iter() {
            ids.push(id.to_string());
        }
        let (s, r) = unbounded();
        let msg = ToCache::Query( CacheQuery {
            ids: ids,
            reply: s,
        });
        channel.send(msg).await.unwrap();
        r.recv().await.unwrap()
    }

    #[async_std::test]
    async fn create() {
        let dir = tempdir().unwrap();
        let s_cache = start_cache(dir.path()).await;
        let result = send_request(vec![ENTRY], s_cache).await;
        match result {
            FromCache::Data(data) => match data.get(ENTRY) {
                Some(output) => match output {
                    DataType::DBMap(_) => (),
                    _ => assert!(false, "{:?} is not a database store.", output),
                },
                None => assert!(false, "Should contain entry point."),
            },
            _ => assert!(false, "{:?} should have been a store.", result),
        }
    }

    #[async_std::test]
    async fn bad_entry() {
        let dir = tempdir().unwrap();
        let s_cache = start_cache(dir.path()).await;
        let result = send_request(vec!["bad_id"], s_cache).await;
        match result {
            FromCache::Error(_) => (),
            _ => assert!(false, "{:?} should have been an error.", result),
        }
    }
}

pub async fn start_db<P>(_dir: P) -> Result<MoreThanText, MTTError>
where
    P: Into<PathBuf>,
{
    let (s, r) = unbounded();
    spawn(async move {
        loop {
            r.recv().await.unwrap();
        }
    });
    Ok(MoreThanText::new(s).await.unwrap())
}

#[cfg(test)]
mod db_start_up {
    use super::*;
    use tempfile::tempdir;

    #[async_std::test]
    async fn initial_session() {
        let dir = tempdir().unwrap();
        let mtt = start_db(dir.path()).await.unwrap();
        assert_eq!(mtt.session, [ENTRY]);
    }
}