500L Graph Database -- WIP, tons of "not-global" mutation

project.clj

@@ -1,6 +1,6 @@
 (defproject hub "0.1.0-SNAPSHOT"
   :description "Playground Clojure app for all the things I want but am too lazy to make a dedicated project for."
-  :dependencies [[org.clojure/clojure "1.10.1"]
+  :dependencies [[org.clojure/clojure "1.11.0"]
                  [org.clojure/core.match "1.0.0"]
                  [org.clojure/data.csv "1.0.1"]
                  [org.clojure/data.json "2.4.0"]

src/clj/hub/500lines/graph_db/core.clj

@@ -0,0 +1,120 @@
+(ns hub.500lines.graph-db.core
+  "https://aosabook.org/en/500L/dagoba-an-in-memory-graph-database.html"
+  (:refer-clojure :exclude [parents]))
+
+;;;; Take One
+
+(def V [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15])
+(def E [[1 2] [1 3] [2 4] [2 5] [3 6] [3 7]
+        [4 8] [4 9] [5 10] [5 11] [6 12] [6 13] [7 14] [7 15]])
+
+
+(defn val-in-vec? [x xs]
+  (some? (some #{x} xs)))
+
+(defn parent [edge] (first edge))
+(defn child [edge] (second edge))
+
+(defn has-parent? [vertices [parent child]]
+  (val-in-vec? parent vertices))
+(defn has-child? [vertices [parent child]]
+  (val-in-vec? child vertices))
+
+(defn parents [vertices]
+  (->> E (filter (partial has-child? vertices)) (map parent)))
+
+(defn children [vertices]
+  (->> E (filter (partial has-parent? vertices)) (map child)))
+
+;;;; Build a Better Graph
+
+(defrecord Vertex [id in out])
+(defn mk-vertex []
+  (Vertex. (random-uuid) [] []))
+
+(defrecord Edge [id in out])
+(defn mk-edge [^Vertex in ^Vertex out]
+  (Edge. (random-uuid) (:id in) (:id out)))
+
+
+;; I'm choosing to change the representation from [edge], [vertex],
+;; {vertexId vertex} to just [edge] {vertexId vertex}.
+(defrecord Graph [edges vertices])
+(defn mk-graph []
+  (Graph. {} {}))
+
+(defn get-vertex [graph vertex-id]
+  (get (:vertices graph) vertex-id))
+
+(defn add-vertex [graph vertex]
+  (when (get-vertex graph (:id vertex))
+    (throw (ex-info "A vertex with that ID already exists"
+                    {:error :Dagoba/AddVertexError
+                     :vertex vertex})))
+  (update graph :vertices assoc (:id vertex) vertex))
+
+(defn add-edge [graph edge]
+  (let [in-vertex  (get-vertex graph (:in edge))
+        out-vertex (get-vertex graph (:out edge))]
+    (when-not (and in-vertex out-vertex)
+      (throw (ex-info "Missing a vertex for this edge."
+                      {:edge       edge
+                       :in-vertex  in-vertex
+                       :out-vertex out-vertex})))
+    (-> graph
+        (update-in [:vertices (:in edge) :in] conj (:id edge))
+        (update-in [:vertices (:out edge) :out] conj (:id edge))
+        (update :edges assoc (:id edge) edge))))
+
+(defn add-vertices [graph vertices]
+  (reduce add-vertex graph vertices))
+
+(defn add-edges [graph edges]
+  (reduce add-edge graph edges))
+
+;;;; Enter the Query
+
+;;; The writeup here HEAVILY leverages JavaScript's prototype
+;;; capabilities. Converting them to Clojure is the whole challenge
+;;; but oof ouchie my brain. A direct mapping is possible but very
+;;; un-Clojure and I don't want to go for that yet.
+
+(defrecord Query [graph state program gremlins])
+(defn mk-query [graph] (Query. graph [] [] []))
+
+(defn add-step [query pipetype args]
+  (let [step [pipetype args]]
+    (update query :program conj step)))
+
+(defn v [graph & args]
+  (add-step (mk-query graph) "vertex" args))
+
+(def v1 (mk-vertex))
+(def v2 (mk-vertex))
+(def e1 (mk-edge v1 v2))
+(def graph
+  (-> (mk-graph)
+      (add-vertices [v1 v2])
+      (add-edges [e1])))
+(v graph "Thor")
+
+;;;; Pipetypes
+
+;;; I think I need to just read up on pipetype and gremlins.
+
+;; TODO: how do i deal with the mutated Q namespace
+(defn add-pipetype [pipetypes name f]
+  [#_ P (assoc pipetypes name f)
+   #_ Q (assoc Q name (fn [query & args] (add-step query name args)))])
+
+(defn faux-pipetype [_ _ maybe-gremlin]
+  (or maybe-gremlin || "pull"))
+
+(defn get-pipetype [pipetypes name]
+  (or (get pipetypes name) faux-pipetype))
+
+
+(add-pipetype pipetypes "vertex"
+              (fn [graph args gremlin state]
+                ;; TODO: I am here
+                ))