use std::collections::HashMap;
use std::cmp::Ordering;
use std::cmp::min;
use fixed::types::U32F32;

#[derive(Debug, Clone)]
struct Offer {
  sell_qty: u64,
  sell_remain: u64,
  buy_qty: u64,
  }

trait Dumpable {
    fn dump(&self);
    }

impl Dumpable for Offer {
    fn dump(&self) {
        println!("Giving {} to get {}",fxp_to_fp(self.sell_qty),fxp_to_fp(self.buy_qty));
        }
    }
  

impl Offer {
    fn dump(self) {
        println!("Remaining: {} Price: {}",self.sell_remain,fxp_to_fp(fxp_div(self.buy_qty,self.sell_qty)));
        }
    }

struct Market {
  asset_name2num: HashMap<String,i32>,
  asset_num2name: HashMap<i32,String>,
  asset_count:i32,
  offers: HashMap<(i32,i32),PQueue<Offer>>,
  }

impl Market {
    fn new() -> Self {
        Market {
            asset_name2num: HashMap::new(),
            asset_num2name: HashMap::new(),
            asset_count:0,
            offers: HashMap::new()
            }
        }
    fn register_asset(&mut self, name:&str) -> i32 {
        self.asset_count+=1;
        self.asset_name2num.insert(String::from(name),self.asset_count);
        self.asset_num2name.insert(self.asset_count,String::from(name));
        self.asset_count
        }
    fn name_to_number(&self, name:&str) -> i32 {
        *self.asset_name2num.get(name).unwrap()
        }
    fn number_to_name(&self, num:i32) -> &str {
        &*self.asset_num2name.get(&num).unwrap()
        }
    fn dump(&self) {
        println!("Dumping Market:");
        for (key,value) in &self.offers {
            println!("Offers selling {} to buy {}:",self.number_to_name(key.0),self.number_to_name(key.1));
            value.dump();
            }
        }
    fn make_offer(&mut self, sell_type:i32, buy_type:i32, sell_qty_initial:u64, buy_qty_initial:u64) // Dollars, Bitcoin, 64000, 1
        { // Comments assume someone is asking 48000 USD for 1 Bitcoin. Then someone comes along and bids $64000 for 1 Bitcoin (sells 64000 USD to buy 1 Bitcoin.
        println!("Making offer to sell {} {} and get {} {}",fxp_to_fp(sell_qty_initial),self.number_to_name(sell_type),fxp_to_fp(buy_qty_initial),self.number_to_name(buy_type));
        let mut sell_qty=sell_qty_initial;      // 64000 Dollars
        let mut buy_qty=buy_qty_initial;        //     1 Bitcoin
        let sell_rate=fxp_div(buy_qty,sell_qty);
        let ap=(buy_type,sell_type);
        while sell_qty>0 {
            if let Some(asks)=self.offers.get_mut(&ap) {
                if asks.v.len()>0 {
                    let elt=&mut asks.v[0];
                    let ask_rate=fxp_div(elt.buy_qty,elt.sell_qty);
                    if sell_rate>=ask_rate { // Transact at ask_rate
                        let ask_transact =fxp_mult(elt.sell_remain,fxp_div(elt.sell_price,elt.sell_qty)); // 48000 USD
                        let sell_transact=sell_qty;
                        let transact=std::cmp::min(ask_transact,sell_transact); // 48000 USD
                        println!("Before: elt.sell_remain={} sell_qty={} transact={}",fxp_to_fp(elt.sell_remain),fxp_to_fp(sell_qty),fxp_to_fp(transact));
                        elt.sell_remain-=transact;
                        sell_qty-=transact;
                        println!("After:  elt.sell_remain={} sell_qty={}",elt.sell_remain,sell_qty);
                        if elt.sell_remain==0 {
                            println!("Popping asks");
                            asks.pop();
                            }
                        } else { break; }
                    } else { break; }
                } else { break; }
            }
        if sell_qty>0 {
            let ap=(sell_type,buy_type);
            if let None=self.offers.get_mut(&ap) { self.offers.insert(ap,PQueue::new()); }
            let mut bids=self.offers.get_mut(&ap).unwrap();
            let sell_price=fxp_div(fxp_mult(sell_price,sell_qty),sell_qty_initial);
            bids.insert(Offer { sell_qty:sell_qty, sell_remain:sell_qty, sell_price:sell_price } );
            }
        }
    }

impl PartialOrd for Offer {  
    fn partial_cmp(&self, other:&Self) -> Option<Ordering> {
        let ord0=self .sell_price/self .sell_qty;
        let ord1=other.sell_price/other.sell_qty;
        if      ord0<ord1 { Some(Ordering::Less) }
        else if ord0>ord1 { Some(Ordering::Greater) }
        else              { Some(Ordering::Equal) }
        }
    }

impl PartialEq for Offer {
    fn eq(&self, other:&Self) -> bool {
        let ord0=self .sell_price/self .sell_qty;
        let ord1=other.sell_price/other.sell_qty;
        ord0==ord1
        }
    }

struct PQueue<T: Dumpable> {
  v: Vec<T>,
  }

impl<T: Dumpable + std::cmp::PartialOrd + std::fmt::Debug> PQueue<T> {
    fn new()->Self {
        PQueue {
            v: Vec::new()
            }
        }
    fn peek(&self) -> &T {
        &self.v[0]
        }
    fn bubble_up(&mut self, pos: usize) {
        if pos>0 {
            let parent=(pos-1)/2;
            if self.v[parent]<self.v[pos] {
                self.v.swap(parent,pos);
                self.bubble_up(parent);
                }
            }
        }
    fn trickle_down(&mut self, pos: usize) {
        let mut pivot=pos;
        let child0=pos*2+1;
        let child1=pos*2+2;
        if child0<self.v.len() {
            if self.v[pos]<self.v[child0] { pivot=child0; }
            if child1<self.v.len() {
                if self.v[pivot]<self.v[child1] { pivot=child1; }
                }
            if pivot!=pos {
                self.v.swap(pivot,pos);
                self.trickle_down(pivot);
                }
            }
        }
    fn insert(&mut self, item: T) {
        self.v.push(item);
        self.bubble_up(self.v.len()-1);
        }
    fn pop(&mut self) -> Option<T> {
        if self.v.len()==0 { None }
        else {
            let end=self.v.len()-1;
            self.v.swap(0,end);
            let rval=self.v.pop();
            self.trickle_down(0);
            rval
            }
        }
    fn dump(&self) {
        for index in 0..self.v.len() {
            self.v[index].dump();
            }
        }
    }

fn fxp_mult(n0:u64, n1:u64) ->u64 { (n0>>32)*(n1>>32)+(n0>>32)*(n1&0xFFFFFFFF)+(n0&0xFFFFFFFF)*(n1>>32)+(n0&0xFFFFFFFF)*(n1&0xFFFFFFFF) }
fn fxp_div(n0:u64, n1:u64) -> u64 { fxp_mult(n0,fxp_recip(n1)) }
fn fxp_from_int(n:u32) -> u64 { (n as u64)<<32 }
fn fxp_recip(n:u64) -> u64 { 0xFFFFFFFFFFFFFFFFu64/n }
fn fxp_to_fp(n:u64) -> f64 { (n as f64)/(1u64<<32) as f64 }


fn main() {
  let mut m=Market::new(); // USD type is 1, EUR type is 2, BTC type is 10, ETH type is 11, SOL type is 12
  let usd=m.register_asset("USD");
  let btc=m.register_asset("BTC");
  let n=64000u64<<32;
  println!("Testing recip: {} {} {}",fxp_to_fp(n),fxp_recip(n),fxp_to_fp(fxp_recip(fxp_recip(n))));
  m.make_offer(btc,usd,fxp_from_int(1),fxp_from_int(1));
  m.dump();
  m.make_offer(usd,btc,fxp_from_int(64000),fxp_from_int(64000)); // Buy 1 BTC for 64000 USD
  m.dump();
}