#![allow(dead_code)]
use crate::bytes::Bytes;
use std::str;

pub struct BytesBase64(pub Vec<u8>);

impl std::fmt::Display for BytesBase64 {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let BytesBase64(digits) = self;
        let mut r: Vec<u8> = digits
            .iter()
            .map(|d| match d {
                0..=25 => *d + b'A',
                26..=51 => *d - 26 + b'a',
                52..=61 => *d - 52 + b'0',
                62 => b'+',
                63 => b'/',
                _ => panic!("Unexpected base64 digit '{}'", d),
            })
            .collect();
        // Handle padding
        let pad = b'=';
        match r.len() % 4 {
            0 => (),
            2 => {
                r.push(pad);
                r.push(pad);
            }
            3 => r.push(pad),
            _ => panic!("Unexpected lenght for padding '{}'", r.len()),
        }
        let s = str::from_utf8(r.as_slice()).unwrap().to_string();
        write!(f, "{}", s)
    }
}

impl BytesBase64 {
    pub fn from_bytes(Bytes(bytes): Bytes) -> BytesBase64 {
        fn to_base64(c: &[u8]) -> Vec<u8> {
            let mut v = c.to_vec();
            // pad with bytes for conversion
            while v.len() < 3 {
                v.push(0);
            }
            let mut result = vec![
                (v[0] & 0b1111_1100) >> 2,
                (v[0] & 0b0000_0011) << 4 | (v[1] & 0b1111_0000) >> 4,
                (v[1] & 0b0000_1111) << 2 | (v[2] & 0b1100_0000) >> 6,
                (v[2] & 0b0011_1111),
            ];
            // removed padded bytes
            for _ in c.len()..3 {
                result.pop();
            }
            result
        }
        BytesBase64(bytes.chunks(3).flat_map(to_base64).collect())
    }

    pub fn to_bytes(&self) -> Bytes {
        fn to_bytes(c: &[u8]) -> Vec<u8> {
            let mut v = c.to_vec();
            // pad with bytes for conversion
            while v.len() < 4 {
                v.push(0);
            }
            let mut result: Vec<u8> = vec![
                ((v[0] & 0b0011_1111) << 2) | ((v[1] & 0b0011_0000) >> 4),
                ((v[1] & 0b0000_1111) << 4) | ((v[2] & 0b0011_1100) >> 2),
                ((v[2] & 0b0000_0011) << 6) | (v[3] & 0b0011_1111),
            ];
            // removed padded bytes
            for _ in c.len()..4 {
                result.pop();
            }
            result
        }
        let BytesBase64(v) = self;
        Bytes(v.chunks(4).flat_map(to_bytes).collect())
    }

    pub fn from_base64(s: &str) -> Result<BytesBase64, String> {
        let mut r: Vec<u8> = Vec::with_capacity(s.len());
        for c in s.chars() {
            match c {
                'A'..='Z' => r.push((c as u8) - b'A'),
                'a'..='z' => r.push((c as u8) - b'a' + 26),
                '0'..='9' => r.push((c as u8) - b'0' + 52),
                '+' => r.push(62),
                '/' => r.push(63),
                '\n' | '=' | ' ' => (),
                _ => {
                    return Err(format!("Unexpected character '{}'", c));
                }
            }
        }
        Ok(BytesBase64(r))
    }
}