nixfiles/src/utils/format_detection.rs

use bytes::{Buf, Bytes};
use std::{fs::File, io::Read, path::Path};
use thiserror::Error;

#[derive(Error, Debug)]
pub enum FormatDetectionError {
	#[error("could not read file")]
	FileReadError,
	#[error("file format unrecognised")]
	UnrecognisedFormat,
}

#[derive(Clone, Copy, Debug, PartialEq)]
pub enum FileFormat {
	FLAC,
	MP3,
	OggVorbis,
	OggOpus,
	OggFLAC,
	OggSpeex,
	OggTheora,
	AIFF,
	Wav,
	WavPack,
}

impl ToString for FileFormat {
	fn to_string(&self) -> String {
		match self {
			FileFormat::FLAC => "FLAC".to_string(),
			FileFormat::MP3 => "MP3".to_string(),
			FileFormat::OggVorbis => "Ogg (Vorbis)".to_string(),
			FileFormat::OggOpus => "Ogg (Opus)".to_string(),
			FileFormat::OggFLAC => "Ogg (FLAC)".to_string(),
			FileFormat::OggSpeex => "Ogg (Speex)".to_string(),
			FileFormat::OggTheora => "Ogg (Theora)".to_string(),
			FileFormat::AIFF => "AIFF".to_string(),
			FileFormat::Wav => "Wav".to_string(),
			FileFormat::WavPack => "WavPack".to_string(),
		}
	}
}

pub fn detect_ogg_subformat(path: &Path) -> Result<FileFormat, FormatDetectionError> {
	let file = File::open(path);

	if let Err(_error) = file {
		return Err(FormatDetectionError::FileReadError);
	}

	let file = file.unwrap();

	let limit = file
		.metadata()
		.map(|m| std::cmp::min(m.len(), 128) as usize + 1)
		.unwrap_or(0);

	let mut bytes = Vec::with_capacity(limit);
	if let Err(_err) = file.take(128).read_to_end(&mut bytes) {
		return Err(FormatDetectionError::FileReadError);
	}

	let mut mem = Bytes::from(bytes);
	mem.advance(28);

	let vorbis_type = mem.get_u8();

	match vorbis_type {
		0x01 => return Ok(FileFormat::OggVorbis),
		0x7f => return Ok(FileFormat::OggFLAC),
		0x80 => return Ok(FileFormat::OggTheora),
		// S for speex
		0x53 => return Ok(FileFormat::OggSpeex),
		_ => {}
	}

	Err(FormatDetectionError::UnrecognisedFormat)
}

fn wavpack_matcher(buf: &[u8]) -> bool {
	// 77 76 70 6b
	buf.len() >= 4 && buf[0] == 0x77 && buf[1] == 0x76 && buf[2] == 0x70 && buf[3] == 0x6b
}

pub fn detect_format(path: &Path) -> Result<FileFormat, FormatDetectionError> {
	let mut info = infer::Infer::new();
	info.add("custom/wavpack", "wv", wavpack_matcher);

	let kind = info.get_from_path(path);

	if let Err(_error) = kind {
		return Err(FormatDetectionError::FileReadError);
	}

	let kind = kind.unwrap();

	if kind.is_none() {
		return Err(FormatDetectionError::UnrecognisedFormat);
	}

	let kind = kind.unwrap();

	match kind.mime_type() {
		"audio/mpeg" => {
			return Ok(FileFormat::MP3);
		}
		"audio/x-wav" => {
			return Ok(FileFormat::Wav);
		}
		"custom/wavpack" => {
			return Ok(FileFormat::WavPack);
		}
		"audio/ogg" => {
			return detect_ogg_subformat(path);
		}
		"audio/x-flac" => {
			return Ok(FileFormat::FLAC);
		}
		"audio/x-aiff" => {
			return Ok(FileFormat::AIFF);
		}
		"audio/opus" => {
			return Ok(FileFormat::OggOpus);
		}
		_ => {}
	}

	Err(FormatDetectionError::UnrecognisedFormat)
}