// Init of configuration files could also be done via Config crate.
// But at this point of development it seems like unjustified overhead.

extern crate serde_json;
use std::fs::File;
use byteorder::{ByteOrder, LittleEndian};
use std::collections::HashMap;
use std::fs;
use std::io::prelude::*;
//use std::thread::{spawn, JoinHandle};
//use std::sync::mpsc::{channel, Receiver};

const PCAPNG_SIGNATURE: [u8; 4] = [0x0a, 0x0d, 0x0d, 0x0a];
const PCAP_SIGNATURE: [u8; 4] = [0xd4, 0xc3, 0xb2, 0xa1];
const PCAP_SIGNATURE_BE: [u8; 4] = [0xa1, 0xb2, 0xc3, 0xa1];

pub struct Config {
    pub filter: String,
    pub regex_filter: String,
    pub insert_max: usize,
    pub pcap_file: String,
    pub connection: String,
    pub device: String,
    pub is_device: bool,
    pub pcap_dir: String,
}

#[derive(Debug)]
pub struct FileInfo {
    pub encapsulation_type: u16,
    pub file_size:           u64,
    pub metadata:           std::fs::Metadata,
}

impl FileInfo {
    fn new(file: std::path::PathBuf, encapsulation_type: u16) -> FileInfo {
      FileInfo { 
        encapsulation_type:  encapsulation_type,
        file_size:          fs::metadata(&file).unwrap().len(),
        metadata:           fs::metadata(&file).unwrap(),
        }
    }
}
        


pub fn from_json_file() -> Option<Config> {
    let config_file = File::open("parser.json").expect("file should open read only");
    let json: serde_json::Value = serde_json::from_reader(config_file).unwrap();
    Some(Config {
        filter: json.get("filter").unwrap().as_str().unwrap().to_owned(),
        regex_filter:  json.get("regex_filter").unwrap().as_str().unwrap().to_owned(),
        insert_max: json.get("insert_max").unwrap().as_u64().unwrap() as usize,
        pcap_file: json.get("pcap_file").unwrap().as_str().unwrap().to_owned(),
        connection: format!(
            "host={} user={} password={}",
            json.get("database_host").unwrap().as_str().unwrap(),
            json.get("database_user").unwrap().as_str().unwrap(),
            json.get("database_password").unwrap().as_str().unwrap(),
        ),
        device: json
            .get("parse_device")
            .unwrap()
            .as_str()
            .unwrap()
            .to_owned(),
        is_device: json.get("from_device").unwrap().as_bool().unwrap(),
        pcap_dir: json.get("pcap_dir").unwrap().as_str().unwrap().to_owned(),
    })
}

/* 
File signature and encapsulation type from file
 See: https://www.tcpdump.org/linktypes.html 
*/
// Futher:file.len() is included in metadata() but only shows up if called explicitly. Maybe this is not needed at all in the end
// This would be needed for comparability over time. print metadata and  you will see
fn bytes_from_file( entry: std::path::PathBuf ) -> Result<([u8;4], u16, u16), std::io::Error> {
                        let mut magic_number: [u8;4] = [0;4];
                        let mut buffer: [u8;32] = [0;32];
                        let mut _file = File::open(entry.to_owned())?;
                        _file.read_exact(&mut buffer)?;
                        magic_number.clone_from_slice(&buffer[0..4]);
                        let enc_pcap: u16 = LittleEndian::read_u16(&buffer[20..22]);
                        let enc_pcapng: u16 = LittleEndian::read_u16(&buffer[12..14]);

   Ok((magic_number, enc_pcap, enc_pcapng))
}

pub fn map_pcap_dir ( pcap_dir: &str ) -> Option<std::collections::HashMap<std::path::PathBuf, FileInfo>> {
    let mut pcap_map = HashMap::new();
    if let Ok(entries) = fs::read_dir(pcap_dir) {
        for entry in entries {
            if let Ok(entry) = entry {
                if let Ok(_file_type) = entry.file_type() {
                    if entry.metadata().unwrap().is_file() {
                        let (magic_number, enc_pcap, enc_pcapng) = bytes_from_file(entry.path()).unwrap();
                        match magic_number {
                            PCAPNG_SIGNATURE => pcap_map.insert(entry.path(), FileInfo::new(entry.path(), enc_pcapng) ), 
                            PCAP_SIGNATURE | PCAP_SIGNATURE_BE => pcap_map.insert(entry.path(), FileInfo::new(entry.path(), enc_pcap)), // TEST: Endiannes for SIGNATURE_BE may be incorrect after introducing fn bytes_from_file()
                            _ => None,
                        };
                        // println!("{:?}", &entry.metadata().unwrap().modified());
                    }
                } else {
                    println!("Couldn't get file type for {:?}", entry.path());
                }
            }
        }
    }
    Some(pcap_map)
}