module bcrypt

const alphabet = './ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'

fn char64(c u8) u8 {
    for i, ch in alphabet {
        if ch == c {
            return u8(i)
        }
    }
    return 255
}

fn base64_decode(data string) []u8 {
    mut dest_index := 0
    mut result := []u8{}
    for src_index := 0; src_index < data.len - 1; src_index += 4 {
        c1 := char64(data[src_index])

        if src_index + 1 >= data.len {
            break
        }

        c2 := char64(data[src_index + 1])

        // Invalid data */
        if c1 == 255 || c2 == 255 {
            break
        }

        result << ((c1 << 2) | ((c2 & 0x30) >> 4))
        dest_index += 1

        if src_index + 2 >= data.len || dest_index == 16 {
            break
        }

        c3 := char64(data[src_index + 2])
        if c3 == 255 {
            break
        }

        result << (((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2))
        dest_index += 1

        if src_index + 3 >= data.len || dest_index == 16 {
            break
        }

        c4 := char64(data[src_index + 3])
        if c4 == 255 {
            break
        }

        result << (((c3 & 0x03) << 6) | c4)
        dest_index += 1

        if dest_index == 16 {
            break
        }
    }

    return result
}

fn base64_encode(data []u8) string {
    mut src_index := 0
    mut result := []u8{}
    for src_index < data.len {
        mut c1 := data[src_index]
        src_index += 1
        result << alphabet[c1 >> 2]
        c1 = (c1 & 0x03) << 4
        if src_index >= data.len {
            result << alphabet[c1]
            break
        }

        mut c2 := data[src_index]
        src_index += 1
        c1 |= (c2 >> 4) & 0x0f
        result << alphabet[c1]
        c1 = (c2 & 0x0f) << 2
        if src_index >= data.len {
            result << alphabet[c1]
            break
        }

        c2 = data[src_index]
        src_index += 1
        c1 |= (c2 >> 6) & 0x03
        result << alphabet[c1]
        result << alphabet[c2 & 0x3f]
    }

    return result.bytestr()
}