use anyhow::{Context, Result};
use itertools::{self, Itertools};
use std::{
    fs::File,
    io::{BufRead, BufReader},
    path::PathBuf,
};

fn parse_single_line(l: String) -> Result<(f64, u32, u32)> {
    let mut splitted = l.split_whitespace();
    let delay: f64 = splitted.next().context("No value found")?.parse()?;
    let high_count: u32 = splitted.next().context("No value found")?.parse()?;
    let low_count: u32 = splitted.next().context("No value found")?.parse()?;
    assert!(splitted.next().is_none());
    Ok((delay, high_count, low_count))
}

fn parse_counts(f: impl BufRead) -> Result<f64> {
    let delay = f
        .lines()
        .filter_map(|l| parse_single_line(l.ok()?).ok())
        .tuple_windows()
        .find(|((_, high1, _), (_, high2, _))| *high1 < 500 && *high2 >= 500)
        .context("Failed to get rise edge")?
        .1
         .0;
    Ok(delay)
}

/// Read clock scan file and get skew.
pub fn parse_count_file(filename: PathBuf) -> Result<f64> {
    let buf_reader = BufReader::new(
        File::open(filename.clone())
            .context(format!("Error opening file {}", filename.display()))?,
    );
    parse_counts(buf_reader)
}

#[cfg(test)]
mod test {
    use super::parse_counts;
    #[test]
    fn test_parse_counts1() {
        let file = "
            0.1 0 1000
            0.2 10 990
            0.3 470 530
            0.4 500 500
            0.5 510 490
            0.6 900 100
            0.7 1000 0
            "
        .as_bytes();
        assert_eq!(parse_counts(file).unwrap(), 0.4);
        let file2 = "
            0.1 0 1000
            0.2 10 990
            0.3 470 530
            0.4 499 501
            0.5 510 490
            0.6 900 100
            0.7 1000 0
            "
        .as_bytes();
        assert_eq!(parse_counts(file2).unwrap(), 0.5);
        let file3 = "
            0.1 0 1000
            0.2 10 990
            0.3 470 530
            0.4 501 499
            0.5 510 490
            0.6 900 100
            0.7 1000 0
            "
        .as_bytes();
        assert_eq!(parse_counts(file3).unwrap(), 0.4);
    }
}