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use crate::Error;
use std::fs::File;
use std::io::prelude::Read;

fn read_random(buf: &mut [u8]) -> Result<(), Error> {
    let mut rand_file = match File::open("/dev/urandom") {
        Ok(rand_file) => rand_file,
        Err(err) => return Error::from(err),
    };

    if let Err(err) = rand_file.read(buf) {
        return Error::from(err);
    }

    Ok(())
}

/// Read a random byte from /dev/urandom
pub fn rand_byte() -> Result<u8, Error> {
    let mut buf = vec![0; 1];
    match read_random(&mut buf) {
        Ok(_) => match buf.get(0) {
            Some(b) => Ok(*b),
            None => Error::from("vector out of bounds"),
        },
        Err(err) => Error::from(err),
    }
}

/// Read random bytes from /dev/urandom
pub fn rand_bytes(size: usize) -> Result<Vec<u8>, Error> {
    let mut buf = vec![0; size];
    match read_random(&mut buf) {
        Ok(_) => Ok(buf),
        Err(err) => Error::from(err),
    }
}

/// Generate random u16
pub fn rand_u16() -> Result<u16, Error> {
    let bytes = match rand_bytes(2) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut safe_bytes = [0u16; 2];
    for (i, b) in safe_bytes.iter_mut().enumerate() {
        *b = match bytes.get(i) {
            Some(&b) => u16::from(b),
            None => return Error::from("vector out of bounds"),
        };
    }
    Ok(safe_bytes[0] * safe_bytes[1])
}

/// Generate random u16s
pub fn rand_u16s(size: usize) -> Result<Vec<u16>, Error> {
    let bytes = match rand_bytes(size * 2 + 2) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut ext = vec![0; size];
    for ei in (1..(size * 2 + 2)).filter(|i| i % 2 == 0) {
        let mut safe_bytes = [0u16; 2];
        for (i, b) in safe_bytes.iter_mut().enumerate() {
            *b = match bytes.get(ei - i) {
                Some(&b) => u16::from(b),
                None => return Error::from("vector out of bounds"),
            };
        }
        ext[(ei - 1) / 2] = safe_bytes[0] * safe_bytes[1];
    }
    Ok(ext)
}

/// Generate random u32
pub fn rand_u32() -> Result<u32, Error> {
    let bytes = match rand_bytes(4) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut safe_bytes = [0u32; 4];
    for (i, b) in safe_bytes.iter_mut().enumerate() {
        *b = match bytes.get(i) {
            Some(&b) => u32::from(b),
            None => return Error::from("vector out of bounds"),
        };
    }
    Ok(safe_bytes[0] * safe_bytes[1] * safe_bytes[2] * safe_bytes[3])
}

/// Generate random u32s
pub fn rand_u32s(size: usize) -> Result<Vec<u32>, Error> {
    let bytes = match rand_bytes(size * 4 + 4) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut ext = vec![0; size];
    for ei in (1..(size * 4 + 4)).filter(|i| i % 4 == 0) {
        let mut safe_bytes = [0u32; 4];
        for (i, b) in safe_bytes.iter_mut().enumerate() {
            *b = match bytes.get(ei - i) {
                Some(&b) => u32::from(b),
                None => return Error::from("vector out of bounds"),
            };
        }
        ext[(ei - 3) / 4] = safe_bytes[0] * safe_bytes[1] * safe_bytes[2] * safe_bytes[3];
    }
    Ok(ext)
}

/// Generate random u64
pub fn rand_u64() -> Result<u64, Error> {
    let bytes = match rand_bytes(8) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut safe_bytes = [0u64; 8];
    for (i, b) in safe_bytes.iter_mut().enumerate() {
        *b = match bytes.get(i) {
            Some(&b) => u64::from(b),
            None => return Error::from("vector out of bounds"),
        };
    }
    Ok(safe_bytes[0]
        * safe_bytes[1]
        * safe_bytes[2]
        * safe_bytes[3]
        * safe_bytes[4]
        * safe_bytes[5]
        * safe_bytes[6]
        * safe_bytes[7])
}

/// Generate random u64s
pub fn rand_u64s(size: usize) -> Result<Vec<u64>, Error> {
    let bytes = match rand_bytes(size * 8 + 8) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut ext = vec![0; size];
    for ei in (1..(size * 8 + 8)).filter(|i| i % 8 == 0) {
        let mut safe_bytes = [0u64; 8];
        for (i, b) in safe_bytes.iter_mut().enumerate() {
            *b = match bytes.get(ei - i) {
                Some(&b) => u64::from(b),
                None => return Error::from("vector out of bounds"),
            };
        }
        ext[(ei - 7) / 8] = safe_bytes[0]
            * safe_bytes[1]
            * safe_bytes[2]
            * safe_bytes[3]
            * safe_bytes[4]
            * safe_bytes[5]
            * safe_bytes[6]
            * safe_bytes[7];
    }
    Ok(ext)
}

/// Generate random u128
pub fn rand_u128() -> Result<u128, Error> {
    let bytes = match rand_bytes(16) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut safe_bytes = [0u128; 16];
    for (i, b) in safe_bytes.iter_mut().enumerate() {
        *b = match bytes.get(i) {
            Some(&b) => u128::from(b),
            None => return Error::from("vector out of bounds"),
        };
    }
    Ok(safe_bytes[0]
        * safe_bytes[1]
        * safe_bytes[2]
        * safe_bytes[3]
        * safe_bytes[4]
        * safe_bytes[5]
        * safe_bytes[6]
        * safe_bytes[7]
        * safe_bytes[8]
        * safe_bytes[9]
        * safe_bytes[10]
        * safe_bytes[11]
        * safe_bytes[12]
        * safe_bytes[13]
        * safe_bytes[14]
        * safe_bytes[15])
}

/// Generate random u128s
pub fn rand_u128s(size: usize) -> Result<Vec<u128>, Error> {
    let bytes = match rand_bytes(size * 16 + 16) {
        Ok(bytes) => bytes,
        Err(err) => return Error::from(err),
    };
    let mut ext = vec![0; size];
    for ei in (1..(size * 16 + 16)).filter(|i| i % 16 == 0) {
        let mut safe_bytes = [0u128; 16];
        for (i, b) in safe_bytes.iter_mut().enumerate() {
            *b = match bytes.get(ei - i) {
                Some(&b) => u128::from(b),
                None => return Error::from("vector out of bounds"),
            };
        }
        ext[(ei - 15) / 16] = safe_bytes[0]
            * safe_bytes[1]
            * safe_bytes[2]
            * safe_bytes[3]
            * safe_bytes[4]
            * safe_bytes[5]
            * safe_bytes[6]
            * safe_bytes[7]
            * safe_bytes[8]
            * safe_bytes[9]
            * safe_bytes[10]
            * safe_bytes[11]
            * safe_bytes[12]
            * safe_bytes[13]
            * safe_bytes[14]
            * safe_bytes[15];
    }
    Ok(ext)
}