use std::path::Path;

use anyhow::Result;
use kdam::tqdm;
use walkdir::WalkDir;

async fn copy(from: String, to: String) -> std::io::Result<()> {
    let from_path = std::path::Path::new(&from);
    let to_path = std::path::Path::new(&to);
    if from_path.is_dir() {
        std::fs::create_dir_all(to)?;
    } else if from_path.is_file() {
        std::fs::create_dir_all(to_path.parent().unwrap())?;
        std::fs::copy(from, to)?;
    }
    Ok(())
}

#[tokio::main]
async fn main() -> Result<()> {
    let args: Vec<String> = std::env::args().collect();

    if args.len() != 3 {
        println!("{} <source> <destination>", args.first().unwrap());
        return Ok(());
    }

    let source = Path::new(&args[1]);
    let destination = Path::new(&args[2]);
    const MAX: usize = 100;
    let mut tasks = Vec::new();
    let count = WalkDir::new(source)
        .into_iter()
        .filter_map(|e| e.ok())
        .filter(|e| e.file_type().is_file()).count();

    for entry in tqdm!(WalkDir::new(source)
        .into_iter()
        .filter_map(|e| e.ok())
        .filter(|e| e.file_type().is_file()), total = count)
    {
        let from = entry.path().to_str().unwrap().to_string();
        let rel = entry.path().strip_prefix(source)?;

        let to = {
            let mut target = destination.to_path_buf();
            target.push(rel);
            target.to_str().unwrap().to_string()
        };

        tasks.push(tokio::spawn(copy(from, to)));

        if tasks.len() > MAX {
            for task in tasks {
                task.await.unwrap()?
            }
            tasks = Vec::new();
        }
    }

    Ok(())
}