# trading: order matching

###### Sprint: ?


###DOC
* in case of reading first part processor please skip this part.

for matching and executing orders openware creates a flow that manage by RabbitMQ and its consumers.
we have three consumers that works on trades:
1. order processor:<br >
   does preliminary calculations and works on order like locking order<br >
2. matching:<br >
   match orders and pass them to executor
3. trade executor:<br >
   execute trades that matching creates


```mermaid
stateDiagram-v2
    [*] --> API
    API --> RabbitMQ
    RabbitMQ --> OrderProcessor
    OrderProcessor --> RabbitMQ
    RabbitMQ --> Matching
    Matching --> RabbitMQ
    RabbitMQ --> Executor
    Executor --> Notify
    Notify --> [*]
```

#### Order matching
##### what does order matching do step by step:
1. submit order ro engine
2. match method
    1. get orderbooks
    2. loop
        1. is order filled?(all amount)
        2. get top order of opposite order book(top means order with best price)
           * for better and faster searching they use rbtree. for more information [click here](https://www.geeksforgeeks.org/red-black-tree-set-1-introduction-2/)
        3. check can they create a trade
        4. is trade valid?(trade validation):<br >
           * not zero,calculation problems
        5. fill both orders:<br >
           * decrease order volume(if the opposite order is filled, we remove it from orderbook)
           * filled order means that order completely get its needed volume
        6. send to trade executor
    
```mermaid
graph TD
    A[RabbitMQ] -->|submit payload| B(Matching)
    B -->|submit engine|C(match method)
    C --> D(get orderbooks)
    D --> E(loop)
    E --> F{order filled?}
    F --> |yes|X(break)
    F --> |no|G{opposit orderbook is blanked}
    G --> |yes|H{is it limit order?}
    H --> |yes|I(add to orderbook)
    I --> X
    H --> |no|J(cancel order)
    J --> X
    G --> |no|K(get top of opposit orderbook)
    K --> L(make trade with top of opposit)
    L --> |created trade|M{trade.blank?}
    M --> |yes|H
    M --> |no|N(validate trade)
    N --> O(fill order)
    O --> P(fill opposit order)
    O --> |publish to executor|A
    O --> E
    X --> A
```