#![allow(dead_code)]
use ed25519_dalek::SigningKey;
use ed25519_dalek::KEYPAIR_LENGTH;
use std::net::AddrParseError;
use std::net::Ipv4Addr;
use std::time::{Duration, SystemTime, UNIX_EPOCH};
use tokio::fs::File;
use tokio::io::{AsyncReadExt, AsyncSeekExt, AsyncWriteExt, SeekFrom};
use tokio::sync::Mutex;

const DATA_SIZE: usize = 76;

enum Error {
    CorruptedIP,
}

impl From<AddrParseError> for Error {
    fn from(_: AddrParseError) -> Self {
        Error::CorruptedIP
    }
}

#[derive(Clone)]
struct Node {
    ip: Ipv4Addr,
    keypair: SigningKey,
    joined_at: SystemTime,
}

impl TryFrom<(&str, SigningKey, SystemTime)> for Node {
    type Error = Error;
    fn try_from(value: (&str, SigningKey, SystemTime)) -> Result<Self, Self::Error> {
        Ok(Self {
            ip: value.0.parse()?,
            keypair: value.1,
            joined_at: value.2,
        })
    }
}

impl Node {
    fn ip_as_string(&self) -> String {
        self.ip.to_string()
    }

    fn signing_key(&self) -> SigningKey {
        self.keypair.clone()
    }

    fn to_bytes(self) -> [u8; DATA_SIZE] {
        let mut result = [0; DATA_SIZE];
        result[0..4].copy_from_slice(&self.ip.octets());
        result[4..68].copy_from_slice(&self.keypair.to_keypair_bytes());
        result[68..DATA_SIZE].copy_from_slice(
            &self
                .joined_at
                .duration_since(UNIX_EPOCH)
                .unwrap()
                .as_secs()
                .to_le_bytes(),
        );
        result
    }

    fn from_bytes(bytes: [u8; DATA_SIZE]) -> Self {
        let ip: [u8; 4] = bytes[0..4].try_into().unwrap();
        let ip: Ipv4Addr = ip.into();
        let keypair: [u8; KEYPAIR_LENGTH] = bytes[4..68].try_into().unwrap();
        let keypair: SigningKey = SigningKey::from_keypair_bytes(&keypair).unwrap();
        let joined_at: [u8; 8] = bytes[68..DATA_SIZE].try_into().unwrap();
        let joined_at: u64 = u64::from_le_bytes(joined_at);
        let joined_at = SystemTime::UNIX_EPOCH + Duration::from_secs(joined_at);
        Self {
            ip,
            keypair,
            joined_at,
        }
    }
}

struct FileManager {
    file: Mutex<File>,
}

impl FileManager {
    async fn init(path: &str) -> std::io::Result<Self> {
        let file = File::options().read(true).append(true).open(path).await?;
        Ok(Self {
            file: Mutex::new(file),
        })
    }

    async fn append_node(&self, node: Node) -> std::io::Result<()> {
        let mut file = self.file.lock().await;
        file.seek(SeekFrom::End(0)).await?;
        file.write_all(&node.to_bytes()).await?;
        file.flush().await?;
        Ok(())
    }

    async fn get_node_by_id(&self, id: u64) -> std::io::Result<Node> {
        let mut file = self.file.lock().await;
        file.seek(SeekFrom::Start(
            id.wrapping_mul(DATA_SIZE.try_into().unwrap_or(0)),
        ))
        .await?;
        let mut node_bytes = [0; DATA_SIZE];
        file.read_exact(&mut node_bytes).await?;
        Ok(Node::from_bytes(node_bytes))
    }

    /// Returns 20 nodes from the disk.
    /// Specify offset (the number of nodes to skip).
    async fn get_page_of_20(&self, offset: u64) -> std::io::Result<Vec<Node>> {
        let mut file = self.file.lock().await;
        file.seek(SeekFrom::Start(
            offset
                .wrapping_mul(DATA_SIZE.try_into().unwrap_or(0)),
        ))
        .await?;
        let mut nodes = Vec::new();
        let mut count = 0;
        loop {
            let mut node_bytes = [0; DATA_SIZE];
            if let Err(_) = file.read_exact(&mut node_bytes).await {
                break;
            };
            nodes.push(Node::from_bytes(node_bytes));
            count += 1;
            if count == 20 {
                break;
            }
        }
        Ok(nodes)
    }
}

#[cfg(test)]
mod tests {

    use super::*;
    use ed25519_dalek::SigningKey;
    use rand::rngs::OsRng;
    use rand::Rng;
    use std::io::Result;
    use tokio::fs::remove_file;
    use tokio::io::AsyncWriteExt;

    const TEST_FILE_PREFIX: &str = ".tmp/test_";
    fn get_test_file_name(function: &str) -> String {
        TEST_FILE_PREFIX.to_string() + function
    }
    async fn setup_test_file(function: &str) -> Result<FileManager> {
        let _ = tokio::fs::create_dir_all(".tmp").await;
        let path = get_test_file_name(function);
        let mut file = File::create(path.clone()).await?;
        file.flush().await?;
        drop(file);
        FileManager::init(&path).await
    }

    #[test]
    fn node_round_trip() {
        let keypair = SigningKey::generate(&mut OsRng);

        let original_node = Node {
            ip: "192.168.1.1".parse().unwrap(),
            keypair: keypair.clone(),
            joined_at: SystemTime::now(),
        };

        let node_bytes = original_node.clone().to_bytes();
        let restored_node = Node::from_bytes(node_bytes);

        assert_eq!(original_node.ip_as_string(), restored_node.ip_as_string());
        assert_eq!(
            original_node.keypair.to_keypair_bytes(),
            restored_node.keypair.to_keypair_bytes()
        );
        assert_eq!(
            original_node
                .joined_at
                .duration_since(UNIX_EPOCH)
                .unwrap()
                .as_secs(),
            restored_node
                .joined_at
                .duration_since(UNIX_EPOCH)
                .unwrap()
                .as_secs()
        );
    }

    #[tokio::test]
    async fn setup_file_manager() {
        let function_name = "setup_file_manager";
        let _ = match setup_test_file(function_name).await {
            Err(e) => {
                panic!("Could not init File Manager: {}", e);
            }
            _ => remove_file(get_test_file_name(function_name)).await,
        };
    }

    fn get_random_node() -> Node {
        let keypair = SigningKey::generate(&mut OsRng);
        let mut rng = rand::thread_rng();
        let ipv4 = Ipv4Addr::new(rng.gen(), rng.gen(), rng.gen(), rng.gen());
        Node {
            ip: ipv4,
            keypair: keypair.clone(),
            joined_at: SystemTime::now(),
        }
    }

    #[tokio::test]
    async fn append_and_retrieve() -> Result<()> {
        let function_name = "append_and_retrieve";
        let manager = setup_test_file(function_name).await?;
        let node = get_random_node();
        manager.append_node(node.clone()).await?;
        let retrieved_node = manager.get_node_by_id(0).await?;
        assert_eq!(node.ip_as_string(), retrieved_node.ip_as_string());
        assert_eq!(node.keypair, retrieved_node.keypair);
        assert_eq!(
            node.joined_at.duration_since(UNIX_EPOCH).unwrap().as_secs(),
            retrieved_node
                .joined_at
                .duration_since(UNIX_EPOCH)
                .unwrap()
                .as_secs()
        );
        remove_file(get_test_file_name(function_name)).await?;
        Ok(())
    }

    #[tokio::test]
    async fn append_and_retrieve_multiple() -> Result<()> {
        let function_name = "append_and_retrieve_multiple";
        let manager = setup_test_file(function_name).await?;
        let node1 = get_random_node();
        let node2 = get_random_node();
        manager.append_node(node1.clone()).await?;
        manager.append_node(node2.clone()).await?;
        let retrieved_node1 = manager.get_node_by_id(0).await?;
        let node3 = get_random_node();
        manager.append_node(node3.clone()).await.unwrap();
        let retrieved_node2 = manager.get_node_by_id(1).await?;
        assert_eq!(node1.ip_as_string(), retrieved_node1.ip_as_string());
        assert_eq!(
            node1.keypair.to_keypair_bytes(),
            retrieved_node1.keypair.to_keypair_bytes()
        );
        assert_eq!(node2.ip_as_string(), retrieved_node2.ip_as_string());
        assert_eq!(node2.keypair, retrieved_node2.keypair);
        let retrieved_node3 = manager.get_node_by_id(2).await?;
        assert_eq!(node3.ip_as_string(), retrieved_node3.ip_as_string());
        assert_eq!(node3.keypair, retrieved_node3.keypair);
        remove_file(get_test_file_name(function_name)).await?;
        Ok(())
    }

    #[tokio::test]
    async fn append_20_and_retrieve_1_loop() -> Result<()> {
        let function_name = "append_20_and_retrieve_1_loop";
        let manager = setup_test_file(function_name).await?;
        let mut count = 0;
        let mut nodes_vec: Vec<Node> = Vec::new();
        while count < 100 {
            let node = get_random_node();
            if count % 10 == 0 {
                nodes_vec.push(node.clone());
            }
            manager.append_node(node).await?;

            count += 1;
        }

        count = 0;
        for node in nodes_vec.iter() {
            let r_node = manager.get_node_by_id(count * 10).await?;
            assert_eq!(node.ip_as_string(), r_node.ip_as_string());
            assert_eq!(node.keypair, r_node.keypair);
            count += 1;
            if count > 3 {
                break;
            }
        }

        count = 100;
        while count < 500 {
            let node = get_random_node();
            if count % 10 == 0 {
                nodes_vec.push(node.clone());
            }
            manager.append_node(node).await?;

            count += 1;
        }

        count = 0;
        for node in nodes_vec.iter() {
            let r_node = manager.get_node_by_id(count * 10).await?;
            assert_eq!(node.ip_as_string(), r_node.ip_as_string());
            assert_eq!(node.keypair, r_node.keypair);
            count += 1;
            if count > 49 {
                break;
            }
        }

        remove_file(get_test_file_name(function_name)).await?;
        Ok(())
    }

    #[tokio::test]
    async fn get_page_of_20_nodes() -> Result<()> {
        let function_name = "get_page_of_20_nodes";
        let manager = setup_test_file(function_name).await?;
        let mut count = 0;
        let mut nodes: Vec<Node> = Vec::new();
        while count < 100 {
            let node = get_random_node();
            if count >= 23 && count < 43 {
                nodes.push(node.clone());
            }
            manager.append_node(node).await?;
            count += 1;
        }
        count = 23;
        let mut r_nodes = manager.get_page_of_20(23).await?.into_iter();
        for node in nodes.iter() {
            let r_node = r_nodes.next().unwrap();
            println!("{} {} {}", count, node.ip_as_string(), r_node.ip_as_string());
            assert_eq!(node.ip_as_string(), r_node.ip_as_string());
            assert_eq!(node.keypair, r_node.keypair);
            count += 1;
            if count == 44 {
                break;
            }
        }
        remove_file(get_test_file_name(function_name)).await?;
        Ok(())
    }

    #[tokio::test]
    async fn get_last_page() -> Result<()> {
        let function_name = "get_last_page";
        let manager = setup_test_file(function_name).await?;
        let mut count = 0;
        let mut nodes: Vec<Node> = Vec::new();
        while count < 97 {
            let node = get_random_node();
            if count >= 90 {
                nodes.push(node.clone());
            }
            manager.append_node(node).await?;
            count += 1;
        }
        count = 23;
        let mut r_nodes = manager.get_page_of_20(90).await?.into_iter();
        for node in nodes.iter() {
            let r_node = r_nodes.next().unwrap();
            println!("{} {} {}", count, node.ip_as_string(), r_node.ip_as_string());
            assert_eq!(node.ip_as_string(), r_node.ip_as_string());
            assert_eq!(node.keypair, r_node.keypair);
            count += 1;
            if count == 44 {
                break;
            }
        }
        remove_file(get_test_file_name(function_name)).await?;
        Ok(())
    }
}