use image::{imageops::FilterType, GenericImageView};
use log::info;
use std::env;
use std::error::Error;
use std::fs::File;
use std::io::{self, BufReader, Read};
use std::path::Path;
use std::str::FromStr;

fn main() -> Result<(), Box<dyn Error>> {
    let args: Vec<_> = env::args().collect();
    if args.len() != 4 {
        eprintln!("Usage: {} <size> <input> <output>", args[0]);
        std::process::exit(1);
    }

    let size = u32::from_str(&args[1])?;

    let mut input = Vec::new();
    if args[2] == "-" {
        io::stdin().read_to_end(&mut input)?;
    } else {
        let file = File::open(&args[2])?;
        let mut reader = BufReader::new(file);
        reader.read_to_end(&mut input)?;
    }

    let output = if args[3] == "-" {
        Path::new("/dev/stdout")
    } else {
        Path::new(&args[3])
    };

    // Guess the format of the input file.
    let format = image::guess_format(&input)?;

    // Decode the image file.
    let image = image::load_from_memory(&input)?;

    let (mut width, mut height) = image.dimensions();
    if width > size {
        width = size;
    }
    if height > size {
        height = size;
    }

    // Resize it to the requested size.
    let image = image.resize(width, height, FilterType::Triangle);

    // Then save it to the output.
    image.save_with_format(output, format)?;

    info!("Successfully resized!");
    Ok(())
}