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use super::{Error, Writer};
use crate::helpers::RateLimit;
use std::io::Write;

/// Writer extensions
pub trait WriterExt {
    /// Join a (huge) list of channels
    ///
    /// This will efficiently partition all of the JOIN commands into max-sized
    /// messages
    ///
    /// Ensuring the channel names are properly formatted and doing the least
    /// amount of actual writes as possible
    ///
    /// ```no_run
    /// # use twitchchat::{helpers::TestStream, Client};
    /// # let mut stream = TestStream::new();
    /// # let (r, w) = (stream.clone(), stream.clone());
    /// # let mut client = Client::new(r, w);
    /// use twitchchat::WriterExt as _;
    /// let writer = client.writer();
    /// writer
    ///     .join_many(
    ///         std::fs::read_to_string("active.txt")
    ///             .unwrap()
    ///             .split('\n')
    ///             .map(str::trim),
    ///     )
    ///     .unwrap();
    /// ```
    fn join_many<'a, I, S>(&self, channels: I) -> Result<(), Error>
    where
        I: IntoIterator<Item = S> + 'a,
        S: AsRef<str> + 'a;

    /// Join a (huge) list of channels but using a [`RateLimit`](./helpers/struct.RateLimit.html)
    ///
    /// Same as [`WriterExt::join_many`](./trait.WriterExt.html#method.join_many), but takes in an optional RateLimit
    ///
    /// If no rate limiter is provided then a default is used (50 channels per 15 seconds)
    fn join_many_limited<'a, I, S>(
        &self,
        channels: I,
        rate: Option<RateLimit>,
    ) -> Result<(), Error>
    where
        I: IntoIterator<Item = S> + 'a,
        S: AsRef<str> + 'a;
}

impl<W: Write> WriterExt for Writer<W> {
    fn join_many_limited<'a, I, S>(&self, channels: I, rate: Option<RateLimit>) -> Result<(), Error>
    where
        I: IntoIterator<Item = S> + 'a,
        S: AsRef<str> + 'a,
    {
        join_limited(channels, self, true, rate)
    }

    fn join_many<'a, I, S>(&self, channels: I) -> Result<(), Error>
    where
        I: IntoIterator<Item = S> + 'a,
        S: AsRef<str> + 'a,
    {
        join_limited(channels, self, false, None)
    }
}

fn join_limited<'a, I, S, W>(
    channels: I,
    w: &Writer<W>,
    try_rate: bool,
    rate: Option<RateLimit>,
) -> Result<(), Error>
where
    I: IntoIterator<Item = S> + 'a,
    S: AsRef<str> + 'a,
    W: Write,
{
    use std::time::Duration;

    let mut rate = if try_rate {
        Some(rate.unwrap_or_else(|| RateLimit::full_unsync(50, Duration::from_secs(15))))
    } else {
        None
    };

    let cap = rate.as_ref().map(RateLimit::cap);

    let mut buf = String::with_capacity(512);

    let mut count = 0;
    let mut prev = 0;
    for channel in channels.into_iter() {
        let channel = channel.as_ref();
        if buf.len() + channel.len() + 1 > 510 || Some(count) == cap {
            // TODO have writer return a MutexGuard
            w.write_line(&buf)?;
            buf.clear();

            if let Some(ref mut rate) = &mut rate {
                for _ in 0..if prev != 0 { prev } else { count } {
                    let _ = rate.take();
                }
            }

            if let Some(cap) = cap {
                prev = 0;
                if count == cap {
                    count = 0
                } else {
                    prev = cap - prev
                }
            }
        }

        if buf.is_empty() {
            buf.push_str("JOIN ");
        } else {
            buf.push(',');
        }

        if !channel.starts_with('#') {
            buf.push_str(&["#", channel].concat());
        } else {
            buf.push_str(&channel);
        }
        count += 1;
    }

    if !buf.is_empty() {
        w.write_line(&buf)?;
    }

    Ok(())
}