//! # Requests limit helper
//!
//! Handle the limitation of requests, depending on threshold criterias


use std::sync::{Arc, Mutex};

use crate::constants::LIMIT_COUNTER_LIFETIME;
use crate::controllers::routes::{LimitPolicy, Route};
use crate::data::error::{ExecError, ResultBoxError};
use crate::data::http_request_handler::HttpRequestHandler;
use crate::utils::date_utils;
use crate::utils::date_utils::time;

/// Information about a IP address limitation
struct IpInfo {
    ip: String,
    time_start: u64,
    uri: String,
    count: u64,
}

/// Limits cache
type Cache = Vec<IpInfo>;

static mut LIMITS_CACHE: Option<Arc<Mutex<Cache>>> = None;

/// Initialize limit cache storage
pub fn init() {
    let limits_cache = Vec::new();
    let limits_cache = Some(Arc::new(Mutex::new(limits_cache)));

    unsafe {
        LIMITS_CACHE = limits_cache;
    }
}

/// Get access to the cache. This resource must absolutely be released as quickly as possible
fn get_cache() -> ResultBoxError<Arc<Mutex<Cache>>> {
    let cache;

    unsafe {
        cache = LIMITS_CACHE.as_ref().unwrap().clone();
    }

    Ok(cache)
}

/// Clean cached information
pub fn clean_cache() -> ResultBoxError {
    let time = date_utils::time();

    let mut i = 0;

    let cache = get_cache()?;
    let mut cache = cache.lock().unwrap();

    while i < cache.len() {
        if cache[i].time_start + LIMIT_COUNTER_LIFETIME < time {
            cache.remove(i);
        } else {
            i = i + 1;
        }
    }

    Ok(())
}

/// Trigger limit helper at the beginning of requests
pub fn trigger_before(req: &HttpRequestHandler, route: &Route) -> ResultBoxError {
    if route.limit_policy.is_none() {
        return Ok(());
    }

    let max_count = route.limit_policy.get_count();
    let ip = req.remote_ip();

    let cache = get_cache()?;
    let found = cache.lock().unwrap()
        .iter()
        .find(
            |k| k.uri.eq(route.uri)
                && k.count >= max_count
                && k.ip.eq(&ip))
        .is_some();

    if found {
        return Err(ExecError::boxed_new("Limit exceeded!"));
    }

    Ok(())
}

/// Trigger limit at the end of the request
pub fn trigger_after(is_success: bool, req: &HttpRequestHandler, route: &Route) -> ResultBoxError {
    let need_trigger = match (&route.limit_policy, is_success)
    {
        (LimitPolicy::NONE, _) => false,
        (LimitPolicy::ANY(_), _) => true,
        (LimitPolicy::SUCCESS(_), res) => res,
        (LimitPolicy::FAILURE(_), res) => !res,
    };

    if !need_trigger {
        return Ok(());
    }

    let ip = req.remote_ip();

    let cache = get_cache()?;
    let mut cache = cache.lock().unwrap();

    // We search for existing entry
    for i in 0..cache.len() {
        if cache[i].ip.eq(&ip) && cache[i].uri.eq(route.uri) {
            cache[i].count += 1;

            return Ok(());
        }
    }

    // Otherwise we must add the entry to the table
    cache.push(IpInfo {
        ip,
        time_start: time(),
        uri: route.uri.to_string(),
        count: 1,
    });

    Ok(())
}