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use std::io;

pub trait Write7BitEncodedI32Ext {
	fn write_7_bit_encoded_i32(&mut self, n: i32) -> io::Result<()>;
}

impl<T: io::Write> Write7BitEncodedI32Ext for T {
	fn write_7_bit_encoded_i32(&mut self, n: i32) -> io::Result<()> {
		let mut n = n as u32;
		let mut byte: u8;
		let mut buff = Vec::<u8>::with_capacity(4);
		loop {
			byte = (n & 127) as u8;
			if n < 128 {
				break;
			}

			byte |= 128;
			n >>= 7;
			buff.push(byte);
		}

		buff.push(byte);
		self.write_all(&buff)
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use crate::write_byte_vec::WriteByteVec;
	#[test]
	fn writing_ints() {
		let mut out = Vec::<u8>::with_capacity(40);
		let mut writer = WriteByteVec::new(&mut out);
		writer.write_7_bit_encoded_i32(-1).unwrap();
		writer.write_7_bit_encoded_i32(-2147483648).unwrap();
		writer.write_7_bit_encoded_i32(1).unwrap();
		writer.write_7_bit_encoded_i32(2147483647).unwrap();
		writer.write_7_bit_encoded_i32(0).unwrap();
		writer.write_7_bit_encoded_i32(2).unwrap();
		writer.write_7_bit_encoded_i32(5).unwrap();
		writer.write_7_bit_encoded_i32(8000000).unwrap();
		writer.write_7_bit_encoded_i32(160000000).unwrap();
		writer.write_7_bit_encoded_i32(30000).unwrap();
		writer.write_7_bit_encoded_i32(-2323232).unwrap();
		writer.write_7_bit_encoded_i32(-23232).unwrap();
		assert_eq!(
			out,
			[
				0xff, 0xff, 0xff, 0xff, 0x0f, 0x80, 0x80, 0x80, 0x80, 0x08, 0x01, 0xff, 0xff, 0xff,
				0xff, 0x07, 0x00, 0x02, 0x05, 0x80, 0xa4, 0xe8, 0x03, 0x80, 0xd0, 0xa5, 0x4c, 0xb0,
				0xea, 0x01, 0xe0, 0x99, 0xf2, 0xfe, 0x0f, 0xc0, 0xca, 0xfe, 0xff, 0x0f,
			]
		);
	}
}