thumbnails 0.2.1

use std::{collections::HashMap, fs::File, path::Path};

use anyhow::Context;
use image::DynamicImage;

use crate::thumbs::*;

type ThumbnailFn = fn(&Thumbnailer, &Path) -> anyhow::Result<DynamicImage>;

/// A struct for generating thumbnails.
///
/// Output thumbnails will be resized according to fit inside `width` and `height`, while
/// preserving original aspect ratios.
#[derive(Debug, Clone)]
pub struct Thumbnailer<'a> {
    /// The maximum output width.
    pub width: u32,
    /// The maximum output height.
    pub height: u32,
    mappings: HashMap<&'a str, ThumbnailFn>,
}

impl Thumbnailer<'_> {
    /// Creates a new Thumbnailer with the given output width and height.
    pub fn new(width: u32, height: u32) -> Self {
        let mut mappings: HashMap<&str, ThumbnailFn> = HashMap::new();

        #[cfg(feature = "img")]
        img::Img::load(&mut mappings);

        #[cfg(feature = "zip")]
        zip::Zip::load(&mut mappings);

        #[cfg(feature = "ffmpeg")]
        if video_rs::init().is_ok() {
            video::Video::load(&mut mappings);
        }

        #[cfg(feature = "pdfium")]
        pdf::Pdf::load(&mut mappings);

        Thumbnailer {
            width,
            height,
            mappings,
        }
    }

    /// Attempt to get an image thumbnail from the given file path.
    pub fn get<T: AsRef<Path>>(&self, path: T) -> anyhow::Result<DynamicImage> {
        let path = path.as_ref();
        let file = File::open(path)?;
        let mime = tree_magic_mini::from_file(&file).context("Failed to find MIME type.")?;

        let func = self
            .mappings
            .get(mime)
            .context(format!("Unsupported MIME type: {mime}"))?;
        func(self, path)
    }
}

pub trait Thumbnailable {
    const MIME_TYPES: &'static [&'static str];
    fn run(thumbnailer: &Thumbnailer, path: &Path) -> anyhow::Result<DynamicImage>;

    fn load(mappings: &mut HashMap<&str, ThumbnailFn>) {
        for mime in Self::MIME_TYPES {
            mappings.insert(mime, Self::run);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::Thumbnailer;

    #[test]
    fn test_thumbnailer_new() {
        let thumbnailer = Thumbnailer::new(500, 300);
        assert_eq!(thumbnailer.width, 500);
        assert_eq!(thumbnailer.height, 300);
    }

    #[test]
    fn test_thumbnailer_get_missing() {
        let thumbnailer = Thumbnailer::new(250, 250);
        let missing = thumbnailer.get("");
        assert!(missing.is_err());
    }
}