//! Utility methods.
use std::fmt::Debug;

use async_std::{io::Read, net::TcpStream, stream::Stream};
use async_stream::stream;
use kuska_ssb::rpc::{RecvMsg, RequestNo, RpcReader};
use serde_json::Value;

use crate::error::GolgiError;
use crate::messages::{SsbMessageKVT, SsbMessageValue};

/// Parse an array of bytes (returned by an rpc call) into a `KVT`.
///
/// # Arguments
///
/// * `body` - An array of u8 to be parsed.
pub fn kvt_res_parse(body: &[u8]) -> Result<SsbMessageKVT, GolgiError> {
    let value: Value = serde_json::from_slice(body)?;
    let kvt: SsbMessageKVT = serde_json::from_value(value)?;
    Ok(kvt)
}

/// Parse an array of bytes (returned by an rpc call) into a `String`.
///
/// # Arguments
///
/// * `body` - An array of u8 to be parsed.
pub fn string_res_parse(body: &[u8]) -> Result<String, GolgiError> {
    Ok(std::str::from_utf8(body)?.to_string())
}

/// Parse an array of bytes (returned by an rpc call) into a `serde_json::Value`.
///
/// # Arguments
///
/// * `body` - An array of u8 to be parsed.
pub fn json_res_parse(body: &[u8]) -> Result<Value, GolgiError> {
    let message: Value = serde_json::from_slice(body)?;
    Ok(message)
}

/// Parse an array of bytes (returned by an rpc call) into an `SsbMessageValue`.
///
/// # Arguments
///
/// * `body` - An array of u8 to be parsed.
pub fn ssb_message_res_parse(body: &[u8]) -> Result<SsbMessageValue, GolgiError> {
    let message: SsbMessageValue = serde_json::from_slice(body)?;
    Ok(message)
}

/// Take in an RPC request number along with a handling function and wait for
/// an RPC response which matches the request number. Then, call the handling
/// function on the response.
///
/// # Arguments
///
/// * `rpc_reader` - A `RpcReader` which can return Messages in a loop
/// * `req_no` - A `RequestNo` of the response to listen for
/// * `f` - A function which takes in an array of `u8` and returns a
/// `Result<T, GolgiError>`. This is a function which parses the response from
/// the `RpcReader`. `T` is a generic type, so this parse function can return
/// multiple possible types (`String`, JSON, custom struct etc.)
pub async fn get_async<'a, R, T, F>(
    rpc_reader: &mut RpcReader<R>,
    req_no: RequestNo,
    f: F,
) -> Result<T, GolgiError>
where
    R: Read + Unpin,
    F: Fn(&[u8]) -> Result<T, GolgiError>,
    T: Debug,
{
    loop {
        let (id, msg) = rpc_reader.recv().await?;
        if id == req_no {
            match msg {
                RecvMsg::RpcResponse(_type, body) => {
                    return f(&body);
                }
                RecvMsg::ErrorResponse(message) => {
                    return Err(GolgiError::Sbot(message));
                }
                RecvMsg::CancelStreamRespose() => {
                    return Err(GolgiError::Sbot(
                        "sbot returned CancelStreamResponse before any content".to_string(),
                    ));
                }
                _ => {}
            }
        }
    }
}

/// Take in an RPC request number along with a handling function and call
/// the handling function on all RPC responses which match the request number,
/// appending the result of each parsed message to a vector until a
/// `CancelStreamResponse` is found (marking the end of the stream).
///
/// # Arguments
///
/// * `rpc_reader` - A `RpcReader` which can return Messages in a loop
/// * `req_no` - A `RequestNo` of the response to listen for
/// * `f` - A function which takes in an array of `u8` and returns a
/// `Result<T, GolgiError>`. This is a function which parses the response from
/// the `RpcReader`. `T` is a generic type, so this parse function can return
/// multiple possible types (`String`, JSON, custom struct etc.)
pub async fn get_source_until_eof<'a, R, T, F>(
    rpc_reader: &mut RpcReader<R>,
    req_no: RequestNo,
    f: F,
) -> Result<Vec<T>, GolgiError>
where
    R: Read + Unpin,
    F: Fn(&[u8]) -> Result<T, GolgiError>,
    T: Debug,
{
    let mut messages: Vec<T> = Vec::new();
    loop {
        let (id, msg) = rpc_reader.recv().await?;
        if id == req_no {
            match msg {
                RecvMsg::RpcResponse(_type, body) => {
                    let parsed_response: Result<T, GolgiError> = f(&body);
                    match parsed_response {
                        Ok(parsed_message) => {
                            messages.push(parsed_message);
                        }
                        Err(err) => {
                            return Err(err);
                        }
                    }
                }
                RecvMsg::ErrorResponse(message) => {
                    return Err(GolgiError::Sbot(message));
                }
                RecvMsg::CancelStreamRespose() => break,
                _ => {}
            }
        }
    }
    Ok(messages)
}

/// Take in an RPC request number along with a handling function and call the
/// handling function on all responses which match the request number. Then,
/// prints out the result of the handling function.
///
/// This function useful for debugging and only prints the output.
///
/// # Arguments
///
/// * `rpc_reader` - A `RpcReader` which can return Messages in a loop
/// * `req_no` - A `RequestNo` of the response to listen for
/// * `f` - A function which takes in an array of `u8` and returns a
/// `Result<T, GolgiError>`. This is a function which parses the response from
/// the `RpcReader`. `T` is a generic type, so this parse function can return
/// multiple possible types (`String`, JSON, custom struct etc.)
pub async fn print_source_until_eof<'a, R, T, F>(
    rpc_reader: &mut RpcReader<R>,
    req_no: RequestNo,
    f: F,
) -> Result<(), GolgiError>
where
    R: Read + Unpin,
    F: Fn(&[u8]) -> Result<T, GolgiError>,
    T: Debug + serde::Deserialize<'a>,
{
    loop {
        let (id, msg) = rpc_reader.recv().await?;
        if id == req_no {
            match msg {
                RecvMsg::RpcResponse(_type, body) => {
                    let display = f(&body)?;
                    println!("{:?}", display);
                }
                RecvMsg::ErrorResponse(message) => {
                    return Err(GolgiError::Sbot(message));
                }
                RecvMsg::CancelStreamRespose() => break,
                _ => {}
            }
        }
    }
    Ok(())
}

/// Take in an RPC request number along with a handling function (parsing
/// results of type `T`) and produce an `async_std::stream::Stream` of results
/// of type `T`, where the handling function is called on all `RpcReader`
/// responses which match the request number.
///
/// # Arguments
///
/// * `req_no` - A `RequestNo` of the response to listen for
/// * `f` - A function which takes in an array of `u8` and returns a
/// `Result<T, GolgiError>`. This is a function which parses the response from
/// the `RpcReader`. `T` is a generic type, so this parse function can return
/// multiple possible types (`String`, JSON, custom struct etc.)
pub async fn get_source_stream<'a, F, T>(
    mut rpc_reader: RpcReader<TcpStream>,
    req_no: RequestNo,
    f: F,
) -> impl Stream<Item = Result<T, GolgiError>>
where
    F: Fn(&[u8]) -> Result<T, GolgiError>,
    T: Debug + serde::Deserialize<'a>,
{
    // we use the async_stream::stream macro to allow for creating a stream which calls async functions
    // see https://users.rust-lang.org/t/how-to-create-async-std-stream-which-calls-async-function-in-poll-next/69760
    let source_stream = stream! {
        loop {
            // get the next message from the rpc_reader
            let (id, msg) = rpc_reader.recv().await?;
            let x : i32 = id.clone();
            // check if the next message from rpc_reader matches the req_no we are looking for
            // if it matches, then this rpc response is for the given request
            // and if it doesn't match, then we ignore it
            if x == req_no {
                match msg {
                    RecvMsg::RpcResponse(_type, body) => {
                        // parse an item of type T from the message body using the provided
                        // function for parsing
                        let item = f(&body)?;
                        // return Ok(item) as the next value in the stream
                        yield Ok(item)
                    }
                    RecvMsg::ErrorResponse(message) => {
                        // if an error is received
                        // return an Err(err) as the next value in the stream
                        yield Err(GolgiError::Sbot(message.to_string()));
                    }
                    // if we find a CancelStreamResponse
                    // this is the end of the stream
                    RecvMsg::CancelStreamRespose() => break,
                    // if we find an unknown response, we just continue the loop
                    _ => {}
                }
            }
        }
    };
    // finally return the stream object
    source_stream
}