use std::{fs::File, sync::Arc, path::Path, ffi::OsStr, io::Read};

use image::ImageError;

use crate::{resource_manager::ResourceStorage, texture::Texture, resource::Resource};

use super::{LoaderError, ResourceLoader};

impl From<ImageError> for LoaderError {
    fn from(value: ImageError) -> Self {
        LoaderError::DecodingError(value.into())
    }
}

/// A struct that implements the `ResourceLoader` trait used for loading textures.
#[derive(Default)]
pub struct TextureLoader;

impl ResourceLoader for TextureLoader {
    fn extensions(&self) -> &[&str] {
        &[
            // the extensions of these are the names of the formats
            "bmp", "dds", "gif", "ico", "jpeg", "jpg", "png", "qoi", "tga", "tiff", "webp",

            // farbfeld
            "ff",
            
            // pnm
            "pnm", "pbm", "pgm", "ppm", "pam",
        ]
    }

    fn load(&self, path: &str) -> Result<Arc<dyn ResourceStorage>, LoaderError> {
        // check if the file is supported by this loader
        if !self.does_support_file(path) {
            return Err(LoaderError::UnsupportedExtension(path.to_string()));
        }

        // read file bytes
        let mut file = File::open(path)?;
        let mut buf = vec![];
        file.read_to_end(&mut buf)?;

        // load the image and construct Resource<Texture>
        let image = image::load_from_memory(&buf)
            .map_err(|e| match e {
                ImageError::IoError(e) => LoaderError::IoError(e),
                _ => LoaderError::DecodingError(e.into()),
            })?;
        let texture = Texture {
            image,
        };
        let res = Resource::with_data(path, texture);

        Ok(Arc::new(res))
    }
}

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

    fn get_image(path: &str) -> String {
        let manifest = std::env::var("CARGO_MANIFEST_DIR").unwrap();
        
        format!("{manifest}/test_files/img/{path}")
    }

    #[test]
    fn check_unsupport() {
        let loader = TextureLoader::default();
        assert_eq!(loader.does_support_file("test.gltf"), false);
    }

    /// Tests loading an image
    #[test]
    fn image_load() {
        let loader = TextureLoader::default();
        loader.load(&get_image("squiggles.png")).unwrap();
    }

    #[test]
    fn image_load_unsupported() {
        let loader = TextureLoader::default();
        assert!(loader.load(&get_image("squiggles.gltf")).is_err());
    }
}