use clap::Parser;
use std::{
    fs::File,
    io::{BufRead, BufReader, BufWriter, Write},
    path::PathBuf,
};

#[derive(Parser)]
struct Args {
    atlas_out: PathBuf,
    atlas_meta_out: PathBuf,
    inputs: Vec<PathBuf>,
}

fn main() {
    let Args {
        inputs,
        atlas_meta_out,
        atlas_out,
    } = Args::parse();

    let atlas_size = 1024;

    let mut cursor_x = 0;
    let mut cursor_y = 0;
    let mut row_height = 0;

    let mut texels = vec![vec![' '; atlas_size]; atlas_size];
    let mut metadata = Vec::new();

    for path in inputs {
        let file = BufReader::new(File::open(&path).unwrap());
        let tex = file.lines().map(Result::unwrap).collect::<Vec<String>>();
        let (width, height) = (tex[0].len(), tex.len());

        if cursor_x + width > atlas_size {
            cursor_y += row_height;
            row_height = 0;
            cursor_x = 0;
        }
        if cursor_y + height > atlas_size {
            panic!("texture too big or atlas full")
        }
        row_height = row_height.max(atlas_size);
        let texcoord = [cursor_x, cursor_y];

        for (y, line) in tex.iter().enumerate() {
            if line.is_empty() {
                continue;
            }
            for (x, char) in line.chars().enumerate() {
                texels[cursor_y + y][cursor_x + x] = char;
            }
        }

        metadata.push((
            texcoord,
            path.file_stem().unwrap().to_str().unwrap().to_string(),
        ));

        cursor_x += atlas_size;
    }

    let mut atlas_out = BufWriter::new(File::create(atlas_out).unwrap());
    let mut atlas_meta_out = BufWriter::new(File::create(atlas_meta_out).unwrap());

    for line in texels {
        for char in line {
            write!(atlas_out, "{char}").unwrap()
        }
        writeln!(atlas_out).unwrap();
    }

    for ([x, y], name) in metadata {
        writeln!(atlas_meta_out, "{x},{y},{name}").unwrap();
    }
}