// Import pure and fast JSON library written in Rust
use serde_json::json;
use serde_json::Value;
// Import chrono library to handle time related operation conveniently
use chrono::{Utc, TimeZone};
use std::slice;
use std::str;
use std::os::raw::c_char;
use std::io::Write;

#[no_mangle]
pub extern "C" fn rust_filter(tag: *const c_char, tag_len: u32, time_sec: u32, time_nsec: u32, record: *const c_char, record_len: u32) -> *const u8 {
  let slice_tag: &[u8] = unsafe { slice::from_raw_parts(tag as *const u8, tag_len as usize) };
  let slice_record: &[u8] = unsafe { slice::from_raw_parts(record as *const u8, record_len as usize) };
  let mut vt: Vec<u8> = Vec::new();
  vt.write(slice_tag).expect("Unable to write");
  let vtag = str::from_utf8(&vt).unwrap();
  let v: Value = serde_json::from_slice(slice_record).unwrap();
  let dt = Utc.timestamp(time_sec as i64, time_nsec);
  let time = dt.format("%Y-%m-%dT%H:%M:%S.%9f %z").to_string();

  let message = json!({
      "message": v["message"],
      "time": format!("{}", time),
      "tag": vtag,
      "original": v.to_string(),
      "lang": "Rust",
  });

  let buf: String = message.to_string();
  buf.as_ptr()
}