podfeed 0.3.2

//! Convert from info files to rss.

use std::path::{Path, PathBuf};

use futures::stream::StreamExt;
use hard_xml::XmlWrite;
use image::{DynamicImage, GenericImageView, imageops};

use crate::{Result, info, rss};

const TARGET_SIZE: u32 = 1400;

/// List all playlist directories.
pub async fn available_directories<P: AsRef<Path>>(data_dirpath: P) -> Result<Vec<PathBuf>> {
    let mut directories: Vec<PathBuf> = vec![];

    let mut entries = smol::fs::read_dir(data_dirpath.as_ref()).await?;
    while let Some(entry) = entries.next().await {
        let entry = entry?;
        let path = entry.path();
        if path.file_name().unwrap() == "Cache" {
            continue;
        }
        if smol::fs::metadata(&path).await?.is_dir() {
            directories.push(path);
        }
    }

    Ok(directories)
}

/// Replace the parent base directory with the serving base url.
fn replace_base<P: AsRef<Path>>(base_dir: P, base_url: P, filepath: P) -> String {
    filepath
        .as_ref()
        .strip_prefix(base_dir)
        .map(|s| base_url.as_ref().join(s))
        .unwrap()
        .to_string_lossy()
        .to_string()
}

/// Parse channel & episodes, and return the rendered xml.
pub async fn process<P: AsRef<Path>>(base_dir: P, dirpath: P, base_url: P) -> Result<String> {
    let episode_infofiles = info::episode::available_episodes(dirpath.as_ref()).await?;
    println!(
        "- {} ({} episodes)",
        dirpath.as_ref().to_string_lossy(),
        episode_infofiles.len()
    );

    let mut episodes_with_indexes: Vec<(rss::episode::Episode, u32)> = vec![];
    for episode_infofile in episode_infofiles {
        let (episode_info, episode_enclosure, episode_image_filepath) =
            episode_infofile.parse().await?;

        let (rss_episode, playlist_index) = convert_episode(
            base_dir.as_ref(),
            base_url.as_ref(),
            &episode_info,
            &episode_enclosure,
            &episode_image_filepath,
        )?;
        episodes_with_indexes.push((rss_episode, playlist_index));
    }

    // Sort episodes by playlist index.
    let episodes = {
        episodes_with_indexes.sort_by(|a, b| a.1.cmp(&b.1));
        episodes_with_indexes
            .into_iter()
            .map(|(episode, _)| episode)
            .collect::<Vec<_>>()
    };

    let channel_infofile = info::channel::available_channel(&dirpath).await?;
    let (channel_info, channel_image_filepath) = channel_infofile.parse().await?;
    let rss_channel = convert_channel(
        base_dir.as_ref(),
        base_url.as_ref(),
        &channel_info,
        &channel_image_filepath,
        episodes,
    )?;

    let feed = rss::Rss {
        version: "2.0".into(),
        namespace: "http://www.itunes.com/dtds/podcast-1.0.dtd".into(),
        content_namespace: "http://purl.org/rss/1.0/modules/content/".into(),
        channel: rss_channel,
    };
    let rendered_rss = feed.to_string()?;
    let xml_prolog = r#"<?xml version="1.0" encoding="UTF-8"?>"#;

    let rendered_rss = format!("{xml_prolog}\n{rendered_rss}");
    Ok(rendered_rss)
}

/// Convert channel Info into a RSS Channel.
pub fn convert_channel<P: AsRef<Path>>(
    base_dir: P,
    base_url: P,
    source: &info::channel::Info,
    image_filepath: P,
    episodes: Vec<rss::episode::Episode>,
) -> Result<rss::channel::Channel> {
    // Resize channel image to fill 1400x1400 and add the "1400x1400" suffix.
    let resized_image_filepath = get_resized_image_filepath(image_filepath.as_ref(), TARGET_SIZE);

    // Resize the channel image if the resized image does not already exists.
    if !resized_image_filepath.exists() {
        resize_image_to_fill(
            image_filepath.as_ref(),
            resized_image_filepath.as_ref(),
            TARGET_SIZE,
        )?;
    }

    let channel = rss::channel::Channel {
        title: source.title.clone(),
        description: source.description.clone(),
        link: source.link.clone(),
        image: rss::channel::Image {
            image_url: replace_base(
                base_dir.as_ref(),
                base_url.as_ref(),
                resized_image_filepath.as_ref(),
            ),
        },
        author: source.author.clone(),
        language: source.language().to_string(),
        last_build_date: format!(
            "{}",
            source.last_build_date().format("%a, %d %b %Y %H:%M:%S %z")
        ),
        pub_date: format!("{}", source.pub_date().format("%a, %d %b %Y %H:%M:%S %z")),
        category: source.category().to_string(),
        generator: source.generator().to_string(),
        explicit_content: source.explicit_content().to_string(),
        channel_type: source.channel_type().to_string(),
        episodes,
    };

    Ok(channel)
}

/// Convert episode Info to a RSS Episode.
pub fn convert_episode<P: AsRef<Path>>(
    base_dir: P,
    base_url: P,
    source: &info::episode::Info,
    enclosure: &info::episode::Enclosure,
    image_filepath: P,
) -> Result<(rss::episode::Episode, u32)> {
    // Resize episode image to fill 1400x1400 and add the "1400x1400" suffix.
    let resized_image_filepath = get_resized_image_filepath(image_filepath.as_ref(), TARGET_SIZE);

    // Resize the channel image if the resized image does not already exists.
    if !resized_image_filepath.exists() {
        resize_image_to_fill(
            image_filepath.as_ref(),
            resized_image_filepath.as_ref(),
            TARGET_SIZE,
        )?;
    }

    let target = rss::episode::Episode {
        guid: source.guid.clone(),
        pub_date: format!("{}", &source.pub_date().format("%a, %d %b %Y %H:%M:%S %z")),
        title: source.title.clone(),
        link: source.link.clone(),
        description: source.description.clone(),
        enclosure: rss::episode::Enclosure {
            file_url: replace_base(
                base_dir.as_ref(),
                base_url.as_ref(),
                enclosure.video_filepath.as_ref(),
            ),
            file_length: enclosure.video_filelength.to_string(),
            file_type: enclosure.video_filetype.clone(),
        },
        author: source.author.clone(),
        image: rss::episode::Image {
            file_url: replace_base(
                base_dir.as_ref(),
                base_url.as_ref(),
                resized_image_filepath.as_ref(),
            ),
        },
        duration: source.duration_seconds.to_string(),
        explicit_content: "false".into(),
    };

    let playlist_index = source.playlist_index;

    Ok((target, playlist_index))
}

/// Return the filepath to the resized image (same extension as the original image).
fn get_resized_image_filepath<P: AsRef<Path>>(image_filepath: P, target_size: u32) -> PathBuf {
    let mut path = image_filepath.as_ref().to_path_buf();
    let filename = path.file_stem().unwrap().to_string_lossy();
    let extension = image_filepath.as_ref().extension().unwrap();
    let filename = format!("{filename}-{target_size}x{target_size}");
    path.set_file_name(filename);
    path.set_extension(extension);
    path
}

/// Pad an image with the given color on all sides.
fn pad_image(
    img: &DynamicImage,
    pad_left: u32,
    pad_right: u32,
    pad_top: u32,
    pad_bottom: u32,
    pad_color: image::Rgb<u8>,
) -> image::RgbImage {
    let (w, h) = img.dimensions();
    let new_w = w + pad_left + pad_right;
    let new_h = h + pad_top + pad_bottom;
    let mut new_img = image::RgbImage::from_pixel(new_w, new_h, pad_color);
    image::imageops::replace(
        &mut new_img,
        &img.to_rgb8(),
        pad_left as i64,
        pad_top as i64,
    );
    new_img
}

/// Resize an image to fill a square of `target_size` pixels.
///
/// This function saves the resized image to `path-1400x1400.png` if the `target_size` is 1400.
///
#[must_use = "Use the return value of this function"]
fn resize_image_to_fill<P: AsRef<Path>>(
    image_filepath: P,
    resized_image_filepath: P,
    target_size: u32,
) -> Result<()> {
    let img = image::open(image_filepath)?;
    let (a, b) = img.dimensions();
    let t = target_size;

    let (na, nb, p_left, p_right, p_top, p_bot) = if a > b {
        let pb = t - t * b / a;
        let p_top = pb / 2;
        let p_bot = pb - p_top;
        (t, t * b / a, 0, 0, p_top, p_bot)
    } else {
        let pa = t - t * a / b;
        let p_left = pa / 2;
        let p_right = pa - p_left;
        (t * a / b, t, p_left, p_right, 0, 0)
    };

    let new_img = img.resize(na, nb, imageops::FilterType::CatmullRom);
    let black = image::Rgb::from([0, 0, 0]);
    let new_img = pad_image(&new_img, p_left, p_right, p_top, p_bot, black);

    // let (fa, fb) = (new_img.get_width(), new_img.get_height());
    // let path = image_filepath.as_ref().to_string_lossy();
    // println!("dims: {a}x{b} -> {na}, {nb}, {p_left}, {p_right}, {p_top}, {p_bot} -> {fa}x{fb} - {path}");

    new_img.save(resized_image_filepath)?;

    Ok(())
}