//! Generating the strings
use super::*;
use tokio::sync::mpsc::error::SendError;
use futures::StreamExt;

#[derive(Debug, Default)]
pub struct GenBodyError(Option<String>);

impl error::Error for GenBodyError{}
impl fmt::Display for GenBodyError
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	if let Some(z) = &self.0 {
	    write!(f, "failed to write read string {:?} to body", z)
	} else {
	    write!(f, "failed to read string from chain. it might be empty.")
	}
    }
}


pub async fn body(state: State, num: Option<usize>, mut output: mpsc::Sender<String>) -> Result<(), GenBodyError>
{
    let mut chain = state.chain_read();
    let filter = state.outbound_filter();
    match num {
	Some(num) if num < state.config().max_gen_size => {
	    let mut chain = chain.take(num);
	    while let Some(string) = chain.next().await {
		output.send(filter.filter_owned(string)).await?;
	    }
	},
	_ => output.send(filter.filter_owned(chain.next().await.ok_or_else(GenBodyError::default)?)).await?,
    }
    Ok(())
}


impl From<SendError<String>> for GenBodyError
{
    #[inline] fn from(from: SendError<String>) -> Self
    {
	Self(Some(from.0))
    }
}