mod cache;
mod database;
pub mod error;
mod store;

use async_std::{
    fs::{create_dir, read, remove_file, write},
    path::Path,
    sync::{Arc, Mutex},
    task::{sleep, spawn},
};
use database::Database;
use error::{DBError, ErrorCode};
use rand::{distributions::Alphanumeric, thread_rng, Rng};
use std::{
    collections::HashMap,
    fmt, slice, str,
    time::{Duration, Instant},
};
use store::Store;

const DATA: &str = "data";
const ENTRY: &str = "databases";

trait FileData<F> {
    fn to_bytes(&self) -> Vec<u8>;
    fn from_bytes(data: &mut slice::Iter<u8>) -> Result<F, DBError>;
}

trait SessionData {
    fn add(&mut self, key: &str, value: &str, data: &str) -> Result<Vec<String>, DBError>;
    fn eq(&self, key: &str, value: &str) -> Result<Vec<String>, DBError>;
    fn list(&self, keys: Vec<&str>) -> Result<Vec<String>, DBError>;
}

#[derive(Clone)]
pub enum CacheType {
    Raw(String),
    DBMap(Store),
    TableMap,
}

impl CacheType {
    pub fn entry_type(&self) -> String {
        match self {
            CacheType::Raw(_) => "Raw".to_string(),
            CacheType::DBMap(_) => "DBMap".to_string(),
            CacheType::TableMap => "TableMap".to_string(),
        }
    }

    pub fn to_bytes(&self) -> Vec<u8> {
        let mut output = self.entry_type().into_bytes();
        output.push(0);
        match self {
            CacheType::Raw(s) => output.append(&mut s.as_bytes().to_vec()),
            CacheType::DBMap(_) => (),
            CacheType::TableMap => (),
        }
        return output;
    }

    pub fn from_bytes(data: Vec<u8>) -> Result<CacheType, DBError> {
        let mut data_iter = data.iter();
        let mut letter: u8;
        match data_iter.next() {
            Some(item) => letter = *item,
            None => return Err(DBError::new("empty file")),
        }
        let mut header: Vec<u8> = Vec::new();
        while letter != 0 {
            header.push(letter.clone());
            match data_iter.next() {
                Some(item) => letter = *item,
                None => return Err(DBError::new("incomplete file")),
            }
        }
        let header = str::from_utf8(&header).unwrap().to_string();
        match header.as_str() {
            "Raw" => {
                let mut output: Vec<u8> = Vec::new();
                for letter in data_iter {
                    output.push(letter.clone());
                }
                Ok(CacheType::Raw(str::from_utf8(&output).unwrap().to_string()))
            }
            "DBMap" => Ok(CacheType::DBMap(Store::new())),
            "TableMap" => Ok(CacheType::TableMap),
            _ => Err(DBError::new("data corruption")),
        }
    }
}

impl fmt::Display for CacheType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            CacheType::Raw(s) => write!(f, "{}", s),
            CacheType::DBMap(_) => todo!(),
            CacheType::TableMap => todo!(),
        }
    }
}

#[derive(Clone)]
struct CacheEntry {
    data: CacheType,
    last_used: Instant,
}

impl CacheEntry {
    fn new(data: CacheType) -> Self {
        Self {
            data: data,
            last_used: Instant::now(),
        }
    }

    fn elapsed(&self) -> Duration {
        self.last_used.elapsed()
    }

    fn touch(&mut self) {
        self.last_used = Instant::now();
    }

    fn update(&mut self, data: CacheType) {
        self.data = data;
        self.touch();
    }
}

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

#[derive(Clone)]
pub struct MoreThanText {
    cache: Arc<Mutex<HashMap<String, CacheEntry>>>,
    dir: String,
    session: Vec<String>,
}

impl MoreThanText {
    pub async fn new(dir: &str) -> Result<Self, DBError> {
        let data_dir = Path::new(dir).join(DATA);
        if !data_dir.is_dir().await {
            match create_dir(&data_dir).await {
                Ok(_) => (),
                Err(err) => {
                    let mut error = DBError::new("failed to create data directory");
                    error.add_source(err);
                    return Err(error);
                }
            }
        }
        let mut output = Self {
            cache: Arc::new(Mutex::new(HashMap::new())),
            dir: data_dir.to_str().unwrap().to_string(),
            session: Vec::new(),
        };
        let entry_file = Path::new(dir).join(ENTRY);
        let id: String;
        if entry_file.is_file().await {
            let holder = read(entry_file).await.unwrap();
            id = str::from_utf8(&holder).unwrap().to_string();
        } else {
            id = output
                .add_entry(CacheType::DBMap(Store::new()))
                .await
                .unwrap();
            write(entry_file, id.as_bytes()).await.unwrap();
        }
        output.session.push(id);
        let looper = output.cache.clone();
        spawn(async move {
            let hold_time = Duration::from_secs(300);
            loop {
                sleep(Duration::from_secs(1)).await;
                let mut ids: Vec<String> = Vec::new();
                let mut cache = looper.lock().await;
                for (id, entry) in cache.iter() {
                    if entry.elapsed() > hold_time {
                        ids.push(id.to_string());
                    }
                }
                for id in ids.iter() {
                    cache.remove(id);
                }
            }
        });
        Ok(output)
    }

    fn filename(&self, id: &str) -> String {
        let filename = Path::new(&self.dir).join(&id);
        filename.into_os_string().into_string().unwrap()
    }

    fn new_id(&self) -> String {
        thread_rng().sample_iter(&Alphanumeric).take(64).collect()
    }

    async fn add(&self, feature: &str, key: &str, value: &str) -> Self {
        let mut ids: Vec<String> = Vec::new();
        for id in self.session.clone().into_iter() {
            let holder = self.get_entry(&id).await.unwrap();
            //holder.add(feature, key, value);
        }
        let mut output = self.clone();
        output.session.clear();
        output.session.push(value.to_string());
        output
    }

    async fn list(&self, feature: Vec<&str>) -> Result<Vec<String>, DBError> {
        Ok(Vec::new())
    }

    async fn add_entry(&self, entry: CacheType) -> Result<String, DBError> {
        let mut id: String = "".to_string();
        let mut dup = true;
        while dup {
            id = thread_rng().sample_iter(&Alphanumeric).take(32).collect();
            dup = Path::new(&self.dir).join(&id).as_path().exists().await;
        }
        match write(Path::new(&self.filename(&id)), entry.to_bytes()).await {
            Ok(_) => (),
            Err(err) => {
                let mut error = DBError::new("data write");
                error.add_source(err);
                return Err(error);
            }
        };
        let mut cache = self.cache.lock().await;
        let data = CacheEntry::new(entry);
        cache.insert(id.clone(), data);
        Ok(id)
    }

    async fn get_entry(&self, id: &str) -> Result<CacheEntry, DBError> {
        let mut cache = self.cache.lock().await;
        match cache.get_mut(id) {
            Some(entry) => {
                entry.touch();
                Ok(entry.clone())
            }
            None => match read(Path::new(&self.filename(id))).await {
                Ok(content) => {
                    let data = CacheEntry::new(CacheType::from_bytes(content).unwrap());
                    cache.insert(id.to_string(), data.clone());
                    Ok(data)
                }
                Err(_) => Err(DBError::new("cache entry not found")),
            },
        }
    }

    async fn update_entry(&self, id: &str, entry: CacheType) -> Result<(), DBError> {
        match self.get_entry(id).await {
            Ok(_) => (),
            Err(err) => return Err(err),
        }
        match write(Path::new(&self.filename(id)), entry.to_bytes()).await {
            Ok(_) => (),
            Err(err) => {
                let mut error = DBError::new("data write");
                error.add_source(err);
                return Err(error);
            }
        }
        let mut cache = self.cache.lock().await;
        let data = CacheEntry::new(entry);
        cache.insert(id.to_string(), data);
        Ok(())
    }

    async fn delete_entry(&self, id: &str) -> Result<(), DBError> {
        let mut cache = self.cache.lock().await;
        cache.remove(id);
        match remove_file(Path::new(&self.filename(id))).await {
            Ok(_) => Ok(()),
            Err(err) => {
                let mut error = DBError::new("data delete");
                error.add_source(err);
                Err(error)
            }
        }
    }
}

#[cfg(test)]
mod setup {
    use super::*;
    use async_std::fs::remove_dir_all;
    use tempfile::{tempdir, TempDir};

    pub struct MTT {
        pub db: MoreThanText,
        pub dir: TempDir,
    }

    impl MTT {
        pub async fn new() -> Self {
            let dir = tempdir().unwrap();
            let db = MoreThanText::new(dir.path().to_str().unwrap())
                .await
                .unwrap();
            Self { db: db, dir: dir }
        }

        pub async fn create_io_error(&self) {
            remove_dir_all(self.dir.path().join(DATA)).await.unwrap();
        }
    }
}

#[cfg(test)]
mod init {
    use super::*;
    use std::error::Error;
    use tempfile::tempdir;

    #[async_std::test]
    async fn create_data_dir() {
        let dir = tempdir().unwrap();
        MoreThanText::new(dir.path().to_str().unwrap())
            .await
            .unwrap();
        let data_dir = dir.path().join(DATA);
        assert!(data_dir.is_dir(), "Did not create the data directory.");
        dir.close().unwrap();
    }

    #[async_std::test]
    async fn existing_data_dir() {
        let dir = tempdir().unwrap();
        let data_dir = dir.path().join(DATA);
        create_dir(data_dir).await.unwrap();
        MoreThanText::new(dir.path().to_str().unwrap())
            .await
            .unwrap();
        dir.close().unwrap();
    }

    #[async_std::test]
    async fn bad_data_dir() {
        let msg = "could not create directory";
        match MoreThanText::new("kljsdgfhslkfrh").await {
            Ok(_) => assert!(false, "This test should fail to create a data directory"),
            Err(err) => {
                assert_eq!(err.to_string(), "failed to create data directory");
                assert!(err.source().is_some(), "Must include the source error.");
                let err_msg = err.source().unwrap().to_string();
                assert!(err_msg.contains(msg), "'{}' not in '{}'", msg, err_msg);
            }
        };
    }

    #[async_std::test]
    async fn creates_entry_point() {
        let dir = tempdir().unwrap();
        let db = MoreThanText::new(dir.path().to_str().unwrap())
            .await
            .unwrap();
        let entry = dir.path().join(ENTRY);
        assert!(entry.is_file(), "Did not create entry point file.");
        let data = read(entry).await.unwrap();
        let id = str::from_utf8(&data).unwrap();
        let cache = db.get_entry(&id).await.unwrap();
        assert_eq!(cache.data.entry_type(), "DBMap");
        assert_eq!(db.session, [id]);
    }

    #[async_std::test]
    async fn use_existing_entry_point() {
        let dir = tempdir().unwrap();
        let db1 = MoreThanText::new(dir.path().to_str().unwrap())
            .await
            .unwrap();
        let db2 = MoreThanText::new(dir.path().to_str().unwrap())
            .await
            .unwrap();
        assert_eq!(db1.session, db2.session, "Did not read existing entry.");
    }
}

#[cfg(test)]
mod data {
    use super::*;
    use setup::MTT;

    #[async_std::test]
    async fn ids_are_random() {
        let mtt = MTT::new().await;
        let id1 = mtt.db.new_id();
        let id2 = mtt.db.new_id();
        assert_ne!(id1, id2, "Ids should be random");
    }

    #[async_std::test]
    async fn add_database() {
        let mtt = MTT::new().await;
        let name = "fred";
        let id = "*gsdfg";
        let output = mtt.db.add("database", name, id).await;
        assert_eq!(output.session, [id], "should update session info.");
        /*
        assert_eq!(
            mtt.db.list(["database"].to_vec()).await.unwrap(),
            [name],
            "Should list the databases."
        );
        */
    }
}

#[cfg(test)]
mod cache_test {
    use super::*;
    use async_std::fs::read;
    use setup::MTT;
    use std::error::Error;

    #[async_std::test]
    async fn entry_ids_are_random() {
        let mtt = MTT::new().await;
        let data1 = CacheType::Raw("one".to_string());
        let data2 = CacheType::Raw("two".to_string());
        let id1 = mtt.db.add_entry(data1).await.unwrap();
        let id2 = mtt.db.add_entry(data2).await.unwrap();
        assert_ne!(id1, id2, "Ids should be unique.")
    }

    #[async_std::test]
    async fn store_cache() {
        let mtt = MTT::new().await;
        let data = "something";
        let expected = CacheType::Raw(data.to_string());
        let id = mtt.db.add_entry(expected.clone()).await.unwrap();
        let output = mtt.db.get_entry(&id).await.unwrap();
        assert_eq!(output.to_string(), data);
        let dfile = mtt.dir.path().join(DATA).join(&id);
        assert!(dfile.is_file(), "Cache file should exist.");
        let content = read(dfile).await.unwrap();
        assert_eq!(content, expected.to_bytes());
    }

    #[async_std::test]
    async fn get_entry_uodates_time() {
        let mtt = MTT::new().await;
        let id = "something";
        let holder = CacheEntry {
            data: CacheType::Raw("old".to_string()),
            last_used: Instant::now() - Duration::from_secs(200),
        };
        let mut cache = mtt.db.cache.lock().await;
        cache.insert(id.to_string(), holder);
        drop(cache);
        mtt.db.get_entry(&id).await.unwrap();
        let cache = mtt.db.cache.lock().await;
        let entry = cache.get(id).unwrap();
        let held = entry.elapsed();
        assert!(
            Duration::from_secs(1) > held,
            "Duration was {:?}, should have been close to 0s.",
            held
        );
    }

    #[async_std::test]
    async fn retrieve_from_disk() {
        let mtt = MTT::new().await;
        let id = "someid";
        let data = CacheType::Raw("stored".to_string());
        write(mtt.dir.path().join(DATA).join(id), data.to_bytes())
            .await
            .unwrap();
        let output = mtt.db.get_entry(id).await.unwrap();
        assert_eq!(output.to_string(), data.to_string());
        let cache = mtt.db.cache.lock().await;
        let stored = cache.get(id);
        assert!(stored.is_some(), "Did not store entry in the cache.");
    }

    #[async_std::test]
    async fn store_bad_file() {
        let mtt = MTT::new().await;
        let msg = "could not write to file";
        mtt.create_io_error().await;
        match mtt.db.add_entry(CacheType::Raw("fail".to_string())).await {
            Ok(_) => assert!(false, "This test should fail."),
            Err(err) => {
                assert_eq!(err.to_string(), "data write");
                assert!(err.source().is_some(), "Must include the source error.");
                let err_msg = err.source().unwrap().to_string();
                assert!(err_msg.contains(msg), "'{}' not in '{}'", msg, err_msg);
            }
        }
    }

    #[async_std::test]
    async fn retrieve_bad_id() {
        let mtt = MTT::new().await;
        match mtt.db.get_entry(&"Not Valid").await {
            Ok(_) => assert!(false, "Should have raised an error."),
            Err(err) => assert_eq!(err.to_string(), "cache entry not found"),
        }
    }

    #[async_std::test]
    async fn update_cache_entry() {
        let mtt = MTT::new().await;
        let id = "updateable";
        let holder = CacheEntry {
            data: CacheType::Raw("elder".to_string()),
            last_used: Instant::now() - Duration::from_secs(500),
        };
        let mut cache = mtt.db.cache.lock().await;
        cache.insert(id.to_string(), holder);
        drop(cache);
        let expected = "different";
        let expect = CacheType::Raw(expected.to_string());
        mtt.db.update_entry(id, expect.clone()).await.unwrap();
        let output = mtt.db.get_entry(id).await.unwrap();
        assert_eq!(output.to_string(), expected);
        let cache = mtt.db.cache.lock().await;
        let entry = cache.get(id).unwrap();
        let held = entry.elapsed();
        assert!(
            Duration::from_secs(1) > held,
            "Duration was {:?}, should have been close to 0s.",
            held
        );
        drop(cache);
        let content = read(mtt.dir.path().join(DATA).join(id)).await.unwrap();
        assert_eq!(content, expect.to_bytes());
    }

    #[async_std::test]
    async fn update_bad_id() {
        let mtt = MTT::new().await;
        match mtt
            .db
            .update_entry("wilma", CacheType::Raw("wrong".to_string()))
            .await
        {
            Ok(_) => assert!(false, "Bad id should raise an error."),
            Err(err) => assert_eq!(err.to_string(), "cache entry not found"),
        }
    }

    #[async_std::test]
    async fn update_bad_file() {
        let mtt = MTT::new().await;
        let msg = "could not write to file";
        let id = mtt
            .db
            .add_entry(CacheType::Raw("fleeting".to_string()))
            .await
            .unwrap();
        mtt.create_io_error().await;
        match mtt
            .db
            .update_entry(&id, CacheType::Raw("failure".to_string()))
            .await
        {
            Ok(_) => assert!(false, "This should produce a write failure."),
            Err(err) => {
                assert_eq!(err.to_string(), "data write");
                assert!(err.source().is_some(), "Must include the source error.");
                let err_msg = err.source().unwrap().to_string();
                assert!(err_msg.contains(msg), "'{}' not in '{}'", msg, err_msg);
            }
        }
    }

    #[async_std::test]
    async fn remove_entry() {
        let mtt = MTT::new().await;
        let id = mtt
            .db
            .add_entry(CacheType::Raw("delete".to_string()))
            .await
            .unwrap();
        mtt.db.delete_entry(&id).await.unwrap();
        match mtt.db.get_entry(&id).await {
            Ok(_) => assert!(false, "Entry should be removed from cache."),
            Err(_) => (),
        };
    }

    #[async_std::test]
    async fn remove_missing_entry() {
        let mtt = MTT::new().await;
        let msg = "could not remove file";
        match mtt.db.delete_entry("missing").await {
            Ok(_) => assert!(false, "This should produce a write failure."),
            Err(err) => {
                assert_eq!(err.to_string(), "data delete");
                assert!(err.source().is_some(), "Must include the source error.");
                let err_msg = err.source().unwrap().to_string();
                assert!(err_msg.contains(msg), "'{}' not in '{}'", msg, err_msg);
            }
        }
    }

    #[async_std::test]
    async fn remove_older() {
        let mtt = MTT::new().await;
        let id = mtt
            .db
            .add_entry(CacheType::Raw("removed".to_string()))
            .await
            .unwrap();
        let mut cache = mtt.db.cache.lock().await;
        let entry = cache.get_mut(&id).unwrap();
        entry.last_used = Instant::now() - Duration::from_secs(1000);
        drop(cache);
        sleep(Duration::from_secs(2)).await;
        let cache = mtt.db.cache.lock().await;
        let output = cache.get(&id);
        assert!(output.is_none(), "The entry shoould not be in memory.");
        drop(cache);
        let filename = mtt.db.filename(&id);
        let fpath = Path::new(&filename);
        assert!(
            fpath.is_file().await,
            "The stored version should still exist."
        );
    }

    #[async_std::test]
    async fn keep_newer() {
        let mtt = MTT::new().await;
        let id = mtt
            .db
            .add_entry(CacheType::Raw("keep".to_string()))
            .await
            .unwrap();
        sleep(Duration::from_secs(2)).await;
        let cache = mtt.db.cache.lock().await;
        let output = cache.get(&id);
        assert!(output.is_some(), "The entry shoould be in memory.");
    }
}

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

    #[test]
    fn init() {
        let text = "new entry";
        let holder = CacheEntry::new(CacheType::Raw(text.to_string()));
        assert_eq!(holder.to_string(), text);
        let held = holder.elapsed();
        assert!(
            Duration::from_secs(1) > held,
            "Duration was {:?}, should have been close to 0s.",
            held
        );
    }

    #[test]
    fn older() {
        let secs = 800;
        let holder = CacheEntry {
            data: CacheType::Raw("older".to_string()),
            last_used: Instant::now() - Duration::from_secs(secs),
        };
        let held = holder.elapsed() - Duration::from_secs(secs);
        assert!(
            Duration::from_secs(1) > held,
            "{:?} should be close to {}s",
            holder.elapsed(),
            secs
        );
    }

    #[test]
    fn accessed() {
        let mut holder = CacheEntry {
            data: CacheType::Raw("older".to_string()),
            last_used: Instant::now() - Duration::from_secs(700),
        };
        holder.touch();
        let held = holder.elapsed();
        assert!(
            Duration::from_secs(1) > held,
            "Duration was {:?}, should have been close to 0s.",
            held
        );
    }

    #[test]
    fn updated() {
        let text = "new data";
        let mut holder = CacheEntry {
            data: CacheType::Raw("old data".to_string()),
            last_used: Instant::now() - Duration::from_secs(900),
        };
        holder.update(CacheType::Raw(text.to_string()));
        assert_eq!(holder.to_string(), text);
        let held = holder.elapsed();
        assert!(
            Duration::from_secs(1) > held,
            "Duration was {:?}, should have been close to 0s.",
            held
        );
    }
}

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

    #[test]
    fn bad_file_header() {
        let mut data: Vec<u8> = Vec::new();
        let mut ctype = "jlksdfg".as_bytes().to_vec();
        let mut cdata = "ghjk".as_bytes().to_vec();
        data.append(&mut ctype);
        data.push(0);
        data.append(&mut cdata);
        match CacheType::from_bytes(data) {
            Ok(_) => assert!(false, "This should fail."),
            Err(err) => assert_eq!(err.to_string(), "data corruption"),
        }
    }

    #[test]
    fn incomplete_file() {
        let mut data: Vec<u8> = Vec::new();
        let mut ctype = "uoisfde".as_bytes().to_vec();
        data.append(&mut ctype);
        match CacheType::from_bytes(data) {
            Ok(_) => assert!(false, "This should fail."),
            Err(err) => assert_eq!(err.to_string(), "incomplete file"),
        }
    }

    #[test]
    fn empty_file() {
        let data: Vec<u8> = Vec::new();
        match CacheType::from_bytes(data) {
            Ok(_) => assert!(false, "This should fail."),
            Err(err) => assert_eq!(err.to_string(), "empty file"),
        }
    }

    #[test]
    fn get_raw_type() {
        let holder = CacheType::Raw("nothing important".to_string());
        assert_eq!(holder.entry_type(), "Raw");
    }

    #[test]
    fn get_raw_bytes() {
        let data = "addams";
        let holder = CacheType::Raw(data.to_string());
        let mut expected = holder.entry_type().into_bytes();
        expected.push(0);
        expected.append(&mut data.as_bytes().to_vec());
        let output = holder.to_bytes();
        assert_eq!(output, expected);
    }

    #[test]
    fn from_raw_bytes() {
        let holder = CacheType::Raw("stored item".to_string());
        let data = holder.to_bytes();
        let output = CacheType::from_bytes(data).unwrap();
        assert_eq!(output.to_string(), holder.to_string());
    }

    #[test]
    fn get_dbmap_type() {
        let holder = CacheType::DBMap(Store::new());
        assert_eq!(holder.entry_type(), "DBMap");
    }

    #[test]
    fn get_new_databases_bytes() {
        let holder = CacheType::DBMap(Store::new());
        let mut expected = "DBMap".as_bytes().to_vec();
        expected.push(0);
        let output = holder.to_bytes();
        assert_eq!(output, expected);
    }

    #[test]
    fn from_new_databases_bytes() {
        let mut data = "DBMap".as_bytes().to_vec();
        data.push(0);
        let output = CacheType::from_bytes(data).unwrap();
        assert_eq!(output.entry_type(), "DBMap");
    }

    #[test]
    fn get_tablemap_type() {
        let holder = CacheType::TableMap;
        assert_eq!(holder.entry_type(), "TableMap");
    }

    #[test]
    fn get_new_database_bytes() {
        let holder = CacheType::TableMap;
        let mut expected = "TableMap".as_bytes().to_vec();
        expected.push(0);
        let output = holder.to_bytes();
        assert_eq!(output, expected);
    }

    #[test]
    fn from_new_database_bytes() {
        let mut data = "TableMap".as_bytes().to_vec();
        data.push(0);
        let output = CacheType::from_bytes(data).unwrap();
        assert_eq!(output.entry_type(), "TableMap");
    }
}