First commit

.gitignore

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+/target
+/classes
+/checkouts
+pom.xml
+pom.xml.asc
+*.jar
+*.class
+/.lein-*
+/.nrepl-port
+.hgignore
+.hg/
+.idea/

CHANGELOG.md

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+# Change Log
+All notable changes to this project will be documented in this file. This change log follows the conventions of [keepachangelog.com](http://keepachangelog.com/).
+
+## [Unreleased]
+### Changed
+- Add a new arity to `make-widget-async` to provide a different widget shape.
+
+## [0.1.1] - 2018-05-21
+### Changed
+- Documentation on how to make the widgets.
+
+### Removed
+- `make-widget-sync` - we're all async, all the time.
+
+### Fixed
+- Fixed widget maker to keep working when daylight savings switches over.
+
+## 0.1.0 - 2018-05-21
+### Added
+- Files from the new template.
+- Widget maker public API - `make-widget-sync`.
+
+[Unreleased]: https://github.com/your-name/book/compare/0.1.1...HEAD
+[0.1.1]: https://github.com/your-name/book/compare/0.1.0...0.1.1

LICENSE

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+THE ACCOMPANYING PROGRAM IS PROVIDED UNDER THE TERMS OF THIS ECLIPSE PUBLIC
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README.md

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+# book
+
+FIXME: description
+
+## Installation
+
+Download from http://example.com/FIXME.
+
+## Usage
+
+FIXME: explanation
+
+    $ java -jar book-0.1.0-standalone.jar [args]
+
+## Options
+
+FIXME: listing of options this app accepts.
+
+## Examples
+
+...
+
+### Bugs
+
+...
+
+### Any Other Sections
+### That You Think
+### Might be Useful
+
+## License
+
+Copyright © 2018 FIXME
+
+Distributed under the Eclipse Public License either version 1.0 or (at
+your option) any later version.

book.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module cursive.leiningen.project.LeiningenProjectsManager.displayName="book:0.1.0-SNAPSHOT" cursive.leiningen.project.LeiningenProjectsManager.isLeinModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager">
+    <output url="file://$MODULE_DIR$/target/default/classes" />
+    <output-test url="file://$MODULE_DIR$/target/default/classes" />
+    <exclude-output />
+    <option name="createStubs" value="true" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/resources" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/dev-resources" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/test" isTestSource="true" />
+      <excludeFolder url="file://$MODULE_DIR$/target/default" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="Leiningen: clojure-complete:0.2.4" level="project" />
+    <orderEntry type="library" name="Leiningen: org.clojure/clojure:1.8.0" level="project" />
+    <orderEntry type="library" name="Leiningen: org.clojure/tools.nrepl:0.2.12" level="project" />
+  </component>
+</module>

doc/intro.md

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+# Introduction to book
+
+TODO: write [great documentation](http://jacobian.org/writing/what-to-write/)

project.clj

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+(defproject book "0.1.0-SNAPSHOT"
+  :description "FIXME: write description"
+  :url "http://example.com/FIXME"
+  :license {:name "Eclipse Public License"
+            :url "http://www.eclipse.org/legal/epl-v10.html"}
+  :dependencies [[org.clojure/clojure "1.9.0"]]
+  :main ^:skip-aot book.core
+  :target-path "target/%s"
+  :profiles {:uberjar {:aot :all}})

src/book/core.clj

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+(ns book.core
+  (:require [book.order]
+            [clojure.spec.alpha :as s]
+            [clojure.edn :as edn])
+  (:gen-class))
+
+
+
+;; Let say a book is two collections.  The first called
+;; sell-book contains all the sell orders.  The second
+;; called buy-book contains all the buy orders.
+
+(defn create-book [& args]
+  (let [cmp #(< (:price %1) (:price %2))]
+    (apply sorted-set-by cmp args)))
+
+
+(def book {:sell (create-book) :buy (create-book)})
+
+
+(defn buy? [order]
+  (= :buy (:type order)))
+
+
+(defn create-trade [order-to-fulfill book-order]
+  #:book.order{:type  (:type book-order)
+               :quantity (:quantity order-to-fulfill)
+               :price (min (:price order-to-fulfill) (:price book-order))
+               :order-id (:book.order/id order-to-fulfill)
+               :book-id  (:book.order/id book-order)})
+
+(defn create-sell-trade-factory [order-to-fulfill]
+  (fn [trade book-order]
+    (let [qtn-to-fulfill (min (:quantity book-order) (- (:quantity order-to-fulfill) (:already-fulfilled trade 0)))
+          can-fulfill? (< (:price book-order) (:price order-to-fulfill))]
+      (when (and can-fulfill? (< qtn-to-fulfill 0))
+        #:book.order{:type :sell
+                     :quantity qtn-to-fulfill
+                     :price (min (:price book-order) (:price order-to-fulfill))
+                     :order-id (:book.order/id order-to-fulfill)
+                     :book-id  (:book.order/id book-order)}))))
+
+
+(defn create-sell-trades [order-to-fulfill sell-book]
+  (take-while nil?
+              (reductions (create-sell-trade-factory order-to-fulfill) sell-book)))
+
+
+
+(defn partial-trade? [trade order]
+  (not= (:quantity order) (:book.order/quantity trade)))
+
+
+(defn compute-partial-order [order trade]
+  (assoc order :quantity (- (:quantity order) (:book.order/quantity trade 0))))
+
+
+(defn compute-new-sell-book-after-trades [sell-book trades]
+  (let [new-book (drop (-> trades count dec) sell-book)
+        possible-partial-trade (last trades)]
+    (if (partial-trade? possible-partial-trade (first new-book))
+      (conj (rest new-book) (compute-partial-order (first new-book) possible-partial-trade))
+      (rest new-book))))
+
+
+
+(defn match-buy-order-in-sell-book [sell-book order]
+  (let [trades (create-trade order (first sell-book))
+        trades (create-sell-trades order sell-book)
+        new-book (compute-new-sell-book-after-trades sell-book trades)]
+    [trades new-book]))
+
+
+(defn place-buy-order [book order]
+  (match-buy-order-in-sell-book (:sell book) order)
+  (println :bingo))  ;; should return multiple "trade" and a new book
+
+
+(defn place-order [book order]
+  (if (buy? order)
+    (place-buy-order book order)))
+
+
+(defn -main
+  [& args]
+  (let [order (-> args first edn/read-string)]
+      (if (not (s/valid? :book.order/order order))
+        (println "invalid order :( ")
+        (println (place-order book order)))))
+
+

src/book/order.clj

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+(ns book.order
+  (:require [clojure.spec.alpha :as s]))
+
+;;  Let say an order is a map of the following keys
+;;  :amount  the amount of security to exchange
+;;  :price   the price of each security to echange
+;;  :type    one of :sell :buy
+;;  ::id     maybe an id
+
+(s/def ::type #{:buy :sell})
+(s/def ::price pos-int?)
+(s/def ::quantity pos-int?)
+(s/def ::id    pos-int?)
+(s/def ::order (s/keys :req-un [::type ::price ::quantity] :opt [::id]))
+
+;; A trade is defined by the bellow map...
+;;  ::quantity  the amount of exchanged securities
+;;  ::price     the price of the security exchanged
+;;  ::book-id   the order id of the security traded on the book
+;;  ::order-id  the id of the processed ordered
+;;  ::type      the type of exchanged made.  :sell means the book
+;;              is selling securities.  ::buy means the book is
+;;              buying securities.

test/book/core_test.clj

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+(ns book.core-test
+  (:require [clojure.test :refer :all]
+            [book.core :refer :all]))
+
+
+
+(deftest test-match-buy-order-in-sell-book
+  (testing "Simplest case."
+    (let [sell-book (create-book {:type :sell :quantity 10 :price 2 :book.order/id 101})
+          order {:type :buy :quantity 10 :price 2 :book.order/id 102}
+          [trades new-book] (match-buy-order-in-sell-book sell-book order)]
+      (is (= new-book []))
+      (is (= trades [#:book.order{:quantity 10 :price 2 :book-id 101 :order-id 102 :type :sell}]))))
+
+  (testing "Simplest case II."
+    (let [sell-book (create-book {:type :sell :quantity 10 :price 2 :book.order/id 103})
+          order {:type :buy :quantity 10 :price 3 :book.order/id 104}
+          [trades new-book] (match-buy-order-in-sell-book sell-book order)]
+      (is (= new-book []))
+      (is (= trades [#:book.order{:quantity 10 :price 2 :book-id 103 :order-id 104 :type :sell}]))))
+
+  (testing "Simplest case III."
+    (let [sell-book (create-book {:type :sell :quantity 10 :price 2 :book.order/id 105})
+          order {:type :buy :quantity 8 :price 2 :book.order/id 106}
+          [trades new-book] (match-buy-order-in-sell-book sell-book order)]
+      (is (= new-book [{:type :sell :quantity 2 :price 2 :book.order/id 105}]))
+      (is (= trades [#:book.order{:quantity 8 :price 2 :book-id 105 :order-id 106 :type :sell}]))))
+
+  (testing "Simplest case IV."
+    (let [sell-book (create-book {:type :sell :quantity 2 :price 12 :book.order/id 107} {:type :sell :quantity 8 :price 12 :book.order/id 108})
+          order {:type :buy :quantity 10 :price 12 :book.order/id 109}
+          [trades new-book] (match-buy-order-in-sell-book sell-book order)]
+      (is (= new-book []))
+      (is (= trades [#:book.order{:quantity 2 :price 12 :book-id 107 :order-id 109 :type :sell}
+                     #:book.order{:quantity 8 :price 12 :book-id 108 :order-id 109 :type :sell}])))))