;; https://www.youtube.com/watch?v=dQWcD2_FzAU

;; schema
[{:db/ident :user/name
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an identifier for a user"}
 {:db/ident :user/email
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an email address"}
 {:db/ident :org/name
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an identifier for an organization"}
 {:db/ident :repo/slug
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an owner/repository"}
 {:db/ident :repo/owner
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an owning entity for an repository"}
 {:db/ident :repo/fork
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an fork of a repository"}
 {:db/ident :repo/lang
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/many
     :db/doc "a programming language used in the given repository"}
 {:db/ident :org/name
     :db/valueType :db.type/string
     :db/cardinality :db.cardinality/one
     :db/doc "an identifier for an organization"}
]

;; data
[
 {:user/name "richhickey"
  :user/email "rich@e.com"}
 {:user/name "tonsky"
  :user/email "nikita@e.com"}
 {:user/name "pithyless"
  :user/email "norbert@e.com"}
 {:org/name "clojure"}
 {:repo/slug "clojure/clojure"
  :repo/owner [:org/name "clojure"]
  :repo/lang ["clojure", "java"]}
 {:repo/slug "tonsky/datascript"
  :repo/owner [:user/name "tonsky"]
  :repo/lang ["clojure", "javascript"]}
 {:repo/slug "pithyless/datascript"
  :repo/owner [:user/name "pithyless"]
  :repo/fork [:repo/slug "tonsky/datascript"]
  :repo/lang ["clojure", "javascript"]}
]

;; queries
[:find ?e :where [?e _ _]]
[:find ?a :where [_ ?a _]]
[:find ?v :where [_ _ ?v]]
[:find ?e ?a :where [?e ?a _]]
[:find ?e ?v :where [?e _ ?v]]
[:find ?a ?v :where [_ ?a ?v]]
[:find ?e ?a ?v :where [?e ?a ?v]]

[:find ?e :where [?e _ "richhickey"]]
[:find ?e ?v :where [?e :user/name ?v]]
[:find ?name :where [65537 :user/name ?name]]
[:find ?id :where [?id :user/name "tonsky"]]
[:find ?name :where [_ :user/name ?name]]
[:find [?name ...] :where [_ :user/name ?name]]
[:find ?name . :where [_ :user/name ?name]]
[:find ?id ?name :where [?id :user/name ?name]]
[:find ?email :where [?id :user/name "richhickey"] [?id :user/email ?email]]
[:find ?name :where [?id :user/name ?name] [?id :user/email "rich@e.com"]]
[:find ?name ?email :where [?id :user/name ?name] [?id :user/email ?email]]
[:find ?repo :where [?p :user/name "tonsky"] [?r :repo/owner ?p] [?r :repo/slug ?repo]]
[:find ?name :where [?p :user/name ?name] [?r :repo/owner ?p] [?r :repo/slug "tonsky/datascript"]]
[:find ?name ?repo :where [?p :user/name ?name] [?r :repo/owner ?p] [?r :repo/slug ?repo]]
[:find ?name ?repo :where [?p :org/name ?name] [?r :repo/owner ?p] [?r :repo/slug ?repo]]
[:find ?name ?repo :where (or [?p :user/name ?name] [?p :org/name ?name]) [?r :repo/owner ?p] [?r :repo/slug ?repo]]
[:find ?repo :where [?r :repo/slug ?repo] [?r :repo/fork _]]
[:find ?repo :where [?r :repo/slug ?repo] [(missing ?r :repo/fork)]]
[:find ?orig ?fork :where [?orig-id :repo/slug ?orig] [?fork-id :repo/slug ?fork] [?fork-id :repo/fork ?orig-id]]