use base64::Engine;
use thiserror::Error;
use std::io;

#[derive(Error, Debug)]
pub enum UriReadError {
    #[error("IOError: '{0}'")]
    IoError(io::Error),

    // From is implemented for this field in each loader module
    #[error("Base64 decoding error: '{0}'")]
    Base64Decode(base64::DecodeError),

    #[error("Some data was missing from the uri")]
    None
}

/// Read a buffer's uri string into a byte buffer.
///
/// * `containing_path`: The path of the containing folder of the buffers "parent",
///     the parent being where this buffer is defined in,
///     i.e. parent="resources/models/player.gltf", containing="reousrce/models"
pub(crate) fn gltf_read_buffer_uri(containing_path: &str, uri: &str) -> Result<Vec<u8>, UriReadError> {
    let uri = uri.strip_prefix("data").ok_or(UriReadError::None)?;
    let (mime, data) = uri.split_once(",").ok_or(UriReadError::None)?;

    let (_mime, is_base64) = match mime.strip_suffix(";base64") {
        Some(mime) => (mime, true),
        None => (mime, false),
    };

    if is_base64 {
        base64::engine::general_purpose::STANDARD.decode(data).map_err(|e| UriReadError::Base64Decode(e))
    } else {
        let full_path = format!("{containing_path}/{data}");
        std::fs::read(&full_path).map_err(|e| UriReadError::IoError(e))
    }
}