use std::{
    fs,
    io::{self, ErrorKind},
    path::{Path, PathBuf},
};

use clap::Parser;
use color_eyre::eyre::{bail, eyre, Context, Result};
use hittekaart::{
    gpx::{self, Compression},
    renderer,
};
use indicatif::{MultiProgress, ProgressBar, ProgressDrawTarget, ProgressStyle};
use is_terminal::IsTerminal;
use rayon::ThreadPoolBuilder;

#[derive(Parser, Debug, Clone)]
#[command(author, version, about)]
struct Args {
    /// The GPX files to parse.
    #[arg(required = true)]
    files: Vec<PathBuf>,

    /// Minimum zoom level to generate tiles for.
    #[arg(long, default_value_t = 0)]
    min_zoom: u32,

    /// Maximum zoom level to generate tiles for.
    #[arg(long, default_value_t = 19)]
    max_zoom: u32,

    /// Number of threads to use. Set to 0 to use all available CPU cores.
    #[arg(long, short, default_value_t = 0)]
    threads: usize,

    /// The output directory. Will be created if it does not exist.
    #[arg(long, short, default_value = "tiles")]
    output_directory: PathBuf,
}

fn main() -> Result<()> {
    color_eyre::install()?;

    let args = Args::parse();

    if args.max_zoom < args.min_zoom {
        bail!("Max zoom cannot be smaller than min zoom!");
    }

    ThreadPoolBuilder::new()
        .num_threads(args.threads)
        .build_global()?;

    let progress_style =
        ProgressStyle::with_template("[{elapsed}] {prefix:.cyan} {wide_bar} {pos:.green}/{len}")?;
    let zoom_style =
        ProgressStyle::with_template("[{elapsed}] {prefix:.yellow} {wide_bar} {pos:.green}/{len}")?;

    let use_progress_bars = io::stdout().is_terminal();
    let make_bar = |len| {
        if use_progress_bars {
            ProgressBar::new(len)
        } else {
            ProgressBar::hidden()
        }
    };

    let bar = make_bar(args.files.len().try_into().unwrap()).with_style(progress_style.clone());
    bar.set_prefix("Reading GPX files");

    let mut tracks = Vec::new();
    for file in &args.files {
        let compression = Compression::suggest_from_path(file)
            .ok_or_else(|| eyre!("Could not determine format for {file:?}"))?;
        let data = gpx::extract_from_file(file, compression)?;
        tracks.push(data);
        bar.inc(1);
    }
    bar.finish();

    ensure_output_directory(&args.output_directory)?;

    let multibar = MultiProgress::new();
    if !use_progress_bars {
        multibar.set_draw_target(ProgressDrawTarget::hidden())
    }
    let zoom_bar = make_bar((args.max_zoom - args.min_zoom + 1).into()).with_style(zoom_style);
    multibar.add(zoom_bar.clone());
    zoom_bar.set_prefix("Zoom levels");

    for zoom in args.min_zoom..=args.max_zoom {
        let bar = make_bar(tracks.len().try_into().unwrap()).with_style(progress_style.clone());
        multibar.insert_from_back(1, bar.clone());
        bar.set_prefix("Rendering heat zones");
        let counter =
            renderer::render_heatcounter(zoom, &tracks, |x| bar.inc(x.try_into().unwrap()));
        bar.finish();
        multibar.remove(&bar);

        let target = [&args.output_directory, &zoom.to_string().into()]
            .iter()
            .collect::<PathBuf>();
        fs::create_dir(&target)?;

        let bar =
            make_bar(counter.tile_count().try_into().unwrap()).with_style(progress_style.clone());
        multibar.insert_from_back(1, bar.clone());
        bar.set_prefix("Saving heat tiles");
        renderer::lazy_colorization(counter, &target, |x| bar.inc(x.try_into().unwrap()))?;
        bar.finish();
        multibar.remove(&bar);
        zoom_bar.inc(1);
    }
    zoom_bar.finish();

    Ok(())
}

fn ensure_output_directory<P: AsRef<Path>>(path: P) -> Result<()> {
    let path = path.as_ref();
    let metadata = fs::metadata(path);
    match metadata {
        Err(e) if e.kind() == ErrorKind::NotFound => {
            let parent = path.parent().unwrap_or_else(|| Path::new("/"));
            fs::create_dir(path)
                .context(format!("Could not create output directory at {parent:?}"))?
        }
        Err(e) => Err(e).context("Error while checking output directory")?,
        Ok(m) if m.is_dir() => (),
        Ok(_) => bail!("Output directory is not a directory"),
    }
    Ok(())
}