use std::collections::{HashMap, HashSet, BTreeMap};
use std::rc::Rc;
use std::cell::RefCell;
use std::sync::{Arc, Mutex};
use std::marker::PhantomData;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum Status {
    Active,
    Inactive,
    Pending,
    Banned,
}

#[derive(Debug)]
pub struct TreeNode<T> {
    pub value: T,
    pub left: Option<Box<TreeNode<T>>>,
    pub right: Option<Box<TreeNode<T>>>,
}

impl<T: Ord> TreeNode<T> {
    pub fn insert(&mut self, value: T) {
        let target = if value <= self.value {
            &mut self.left
        } else {
            &mut self.right
        };
        match target {
            Some(node) => node.insert(value),
            None => *target = Some(Box::new(TreeNode {
                value,
                left: None,
                right: None,
            })),
        }
    }

    pub fn contains(&self, value: &T) -> bool {
        &self.value == value
            || self.left.as_ref().map_or(false, |n| n.contains(value))
            || self.right.as_ref().map_or(false, |n| n.contains(value))
    }
}

pub trait Monoid {
    fn empty() -> Self;
    fn combine(&self, other: &Self) -> Self;
}

impl Monoid for i32 {
    fn empty() -> Self { 0 }
    fn combine(&self, other: &Self) -> Self { self + other }
}

impl Monoid for String {
    fn empty() -> Self { String::new() }
    fn combine(&self, other: &Self) -> Self { format!("{}{}", self, other) }
}

pub fn reduce<T: Monoid>(items: &[T]) -> T {
    items.iter().fold(T::empty(), |acc, x| acc.combine(x))
}

macro_rules! vec_of_strings {
    ($($x:expr),*) => (vec![$($x.to_string()),*]);
}

pub struct Lazy<T, F = fn() -> T>
where
    F: Fn() -> T,
{
    value: Option<T>,
    factory: F,
}

impl<T, F: Fn() -> T> Lazy<T, F> {
    pub fn new(factory: F) -> Self {
        Self {
            value: None,
            factory,
        }
    }

    pub fn get(&mut self) -> &T {
        self.value.get_or_insert_with(&self.factory)
    }
}

pub async fn parallel_map<T, U, F>(items: Vec<T>, f: F) -> Vec<U>
where
    T: Send + 'static,
    U: Send + 'static,
    F: Fn(T) -> U + Send + Sync + 'static,
{
    use tokio::task;
    let mut handles = Vec::new();
    for item in items {
        handles.push(task::spawn(async move { f(item) }));
    }
    let mut results = Vec::new();
    for handle in handles {
        results.push(handle.await.unwrap());
    }
    results
}

pub struct CustomIterator<T> {
    items: Vec<T>,
    index: usize,
}

impl<T: Clone> Iterator for CustomIterator<T> {
    type Item = T;
    fn next(&mut self) -> Option<Self::Item> {
        if self.index < self.items.len() {
            let item = self.items[self.index].clone();
            self.index += 1;
            Some(item)
        } else {
            None
        }
    }
}

const DEFAULT_PORT: u16 = 8080;
static APP_NAME: &str = "nimcheck-rs";
thread_local! {
    static CACHE: RefCell<HashMap<String, String>> = RefCell::new(HashMap::new());
}

unsafe impl Send for User {}
unsafe impl Sync for User {}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_insert() {
        let mut root = TreeNode { value: 5, left: None, right: None };
        root.insert(3);
        root.insert(7);
        assert!(root.contains(&3));
        assert!(root.contains(&7));
    }
}