From 691b6b2959d0ee5ca02c495fdb0f7d03947f6da1 Mon Sep 17 00:00:00 2001
From: Simon Brooke <simon@journeyman.cc>
Date: Sun, 12 Apr 2020 16:19:11 +0100
Subject: [PATCH] Starting to get `The spread of knowledge in a large game
 world` working

---
 project.clj                              |   1 +
 src/the_great_game/gossip/gossip.clj     |   4 +-
 src/the_great_game/gossip/news_items.clj | 251 +++++++++++++++++++++++
 src/the_great_game/world/location.clj    |  10 +
 4 files changed, 264 insertions(+), 2 deletions(-)
 create mode 100644 src/the_great_game/gossip/news_items.clj
 create mode 100644 src/the_great_game/world/location.clj

diff --git a/project.clj b/project.clj
index ff35841..f7dd23b 100644
--- a/project.clj
+++ b/project.clj
@@ -5,6 +5,7 @@
           :output-path "docs/codox"
           :source-uri "https://github.com/simon-brooke/the-great-game/blob/master/{filepath}#L{line}"}
   :dependencies [[org.clojure/clojure "1.8.0"]
+                 [org.clojure/math.numeric-tower "0.0.4"]
                  [environ "1.1.0"]
                  [com.taoensso/timbre "4.10.0"]]
   :description "Prototype code towards the great game I've been writing about for ten years, and know I will never finish."
diff --git a/src/the_great_game/gossip/gossip.clj b/src/the_great_game/gossip/gossip.clj
index efe442f..13aa961 100644
--- a/src/the_great_game/gossip/gossip.clj
+++ b/src/the_great_game/gossip/gossip.clj
@@ -1,5 +1,5 @@
 (ns the-great-game.gossip.gossip
-  "Interchange of news events between agents agents"
+  "Interchange of news events between gossip agents"
   (:require [the-great-game.utils :refer [deep-merge]]))
 
 ;; Note that habitual travellers are all gossip agents; specifically, at this
@@ -43,7 +43,7 @@
 (defn move-gossip
   "Return a world like this `world` but with this `gossip` moved to this
   `new-location`. Many gossips are essentially shadow-records of agents of
-  other types, and the movement if the gossip should be controlled by the
+  other types, and the movement of the gossip should be controlled by the
   run function of the type of the record they shadow. The [[#run]] function
   below does NOT call this function."
   [gossip world new-location]
diff --git a/src/the_great_game/gossip/news_items.clj b/src/the_great_game/gossip/news_items.clj
new file mode 100644
index 0000000..bcb0398
--- /dev/null
+++ b/src/the_great_game/gossip/news_items.clj
@@ -0,0 +1,251 @@
+(ns the-great-game.gossip.news-items
+  "Categories of news events interesting to gossip agents"
+  (:require [clojure.math.numeric-tower :refer [expt sqrt]]))
+
+;; The ideas here are based on the essay 'The spread of knowledge in a large
+;; game world', q.v.; they've advanced a little beyond that and will doubtless
+;; advance further in the course of writing and debugging this namespace.
+
+;; A news item is a map with the keys:
+;;
+;; * `date` - the date on which the reported event happened;
+;; * `nth-hand` - the number of agents the news item has passed through;
+;; * `verb` - what it is that happened (key into `news-topics`);
+;;
+;; plus other keys taken from the `keys` value associated with the verb in
+;; `news-topics`
+
+(def news-topics
+  "Topics of interest to gossip agents. Topics are keyed in this map by
+  their `verbs`. The `keys` associated with each topic are the extra pieces
+  of information required to give context to a gossip item. Generally:
+
+  * `actor` is the id of the character who performed the action;
+  * `other` is the id of the character on whom the action was performed;
+  * `location` is the place at which the action was performed;
+  * `object` is an object (or possibly list of objects?) relevant to the action;
+  * `price` is special to buy/sell, but of significant interest to merchants.
+
+  #### Notes:
+
+  ##### Locations:
+
+  A 'location' value is a list comprising at most the x/y coordinate location
+  and the ids of the settlement and region (possibly hierarchically) that contain
+  the location. If the x/y is not local to the home of the receiving agent, they
+  won't remember it and won't pass it on; if any of the ids are not interesting
+  So location information will degrade progressively as the item is passed along.
+
+  It is assumed that the `:home` of a character is a location in this sense.
+
+  ##### Inferences:
+
+  If an agent learns that Adam has married Betty, they can infer that Betty has
+  married Adam; if they learn that Charles killed Dorothy, that Dorothy has died.
+  I'm not convinced that my representation of inferences here is ideal.
+  "
+  { ;; A significant attack is interesting whether or not it leads to deaths
+    :attack {:verb :attack :keys [:actor :other :location]}
+    ;; Deaths of characters may be interesting
+    :die {:verb :attack :keys [:actor :location]}
+    ;; Deliberate killings are interesting.
+    :kill {:verb :kill :keys [:actor :other :location]
+           :inferences [{:verb :die :actor :other :other :nil}]}
+    ;; Marriages may be interesting
+    :marry {:verb :marry :keys [:actor :other :location]
+            :inferences [{:verb :marry :actor :other :other :actor}]}
+    ;; The end of ongoing open conflict between to characters may be interesting
+    :peace {:verb :peace :keys [:actor :other :location]
+            :inferences [{:verb :peace :actor :other :other :actor}]}
+    ;; Things related to the plot are interesting, but will require special
+    ;; handling. Extra keys may be required by particular plot events.
+    :plot {:verb :plot :keys [:actor :other :object :location]}
+    ;; Rapes are interesting.
+    :rape {:verb :rape :keys [:actor :other :location]
+           :inferences [{:verb :attack}
+                        {:verb :sex}
+                        {:verb :sex :actor :other :other :actor}]}
+    ;; Merchants, especially, are interested in prices in other markets
+    :sell {:verb :sell :keys [:actor :other :object :location :price]}
+    ;; Sex can juicy gossip, although not normally if the participants are in an
+    ;; established sexual relationship.
+    :sex {:verb :sex :keys [:actor :other :location]
+          :inferences [{:verb :sex :actor :other :other :actor}]}
+    ;; Thefts are interesting
+    :steal {:verb :steal :keys [:actor :other :object :location]}
+    ;; The succession of rulers is interesting; of respected craftsmen,
+    ;; potentially also interesting.
+    :succession {:verb :succession :keys [:actor :other :location :rank]}
+    ;; The start of ongoing open conflict between to characters may be interesting
+    :war {:verb :war :keys [:actor :other :location]
+          :inferences [{:verb :war :actor :other :other :actor}]}
+    })
+
+
+(defn interest-in-character
+  "Integer representation of how interesting this `character` is to this
+  `gossip`."
+  [gossip character]
+  (count
+    (concat
+      (filter #(= (:actor % character)) (:knowledge gossip))
+      (filter #(= (:other % character)) (:knowledge gossip)))))
+
+(defn interesting-character?
+  "Boolean representation of whether this `character` is interesting to this
+  `gossip`."
+  [gossip character]
+  (> (interest-in-character gossip character) 0))
+
+(defn get-coords
+  "Return the coordinates in the game world of `location`, which may be
+  1. A coordinate pair in the format {:x 5 :y 32};
+  2. A location, as discussed above;
+  3. Any other gameworld object, having a `:location` property whose value
+    is one of the above."
+  [location]
+  (cond
+    (empty? location) nil
+    (map? location)
+    (cond
+      (and (number? (:x location)) (number? (:y location)))
+      location
+      (:location location)
+      (:location location))
+    :else
+    (get-coords (first (remove keyword? location)))))
+
+;; (get-coords {:x 5 :y 7})
+;; (get-coords [{:x -4 :y 55} :auchencairn :galloway :scotland])
+
+(defn distance-between
+  [location-1 location-2]
+  (let [c1 (get-coords location-1)
+        c2 (get-coords location-2)]
+    (if
+      (and c1 c2)
+      (sqrt (+ (expt (- (:x c1) (:x c2)) 2) (expt (- (:y c1) (:y c2)) 2))))))
+
+;; (distance-between {:x 5 :y 5} {:x 2 :y 2})
+;; (distance-between {:x 5 :y 5} {:x 2 :y 5})
+;; (distance-between {:x 5 :y 5} [{:x -4 :y 55} :auchencairn :galloway :scotland])
+;; (distance-between {:x 5 :y 5} [:auchencairn :galloway :scotland])
+
+(defn interest-in-location
+  "Integer representation of how interesting this `location` is to this
+  `gossip`."
+  [gossip location]
+  (cond
+    (coll? location)
+    (reduce
+      +
+      (map
+        #(interest-in-location gossip %)
+        location))
+    (and (map? location) (:x location) (:y location))
+    (if-let [home (:home gossip)]
+      (let [d (distance-between location home)
+            i (/ 10000 d) ;; 10000 at metre scale is 10km; interest should
+            ;;fall of with distance from home, but possibly on a log scale
+            ]
+        (if (i > 1) i 0)
+        i))
+    :else
+    (count
+      (filter
+        #(some (fn [x] (= x location)) (:location %))
+        (:knowledge gossip)))))
+
+;; (interest-in-location
+;;   {:knowledge [{:verb :steal
+;;              :actor :albert
+;;              :other :belinda
+;;              :object :foo
+;;              :location [{:x 35 :y 23} :auchencairn :galloway]}]}
+;;   :galloway)
+
+;; (interest-in-location
+;;   {:knowledge [{:verb :steal
+;;              :actor :albert
+;;              :other :belinda
+;;              :object :foo
+;;              :location [{:x 35 :y 23} :auchencairn :galloway]}]}
+;;   [:galloway :scotland])
+
+
+;; (interest-in-location
+;;   {:knowledge [{:verb :steal
+;;              :actor :albert
+;;              :other :belinda
+;;              :object :foo
+;;              :location [{:x 35 :y 23} :auchencairn :galloway]}]}
+;;   :dumfries)
+
+;; (interest-in-location
+;;   {:home {:x 35 :y 23}}
+;;   {:x 35 :y 24})
+
+(defn interesting-location?
+  "True if the location of this news `item` is interesting to this `gossip`."
+  [gossip item]
+  (> (interest-in-location gossip (:location item)) 1))
+
+(defn interesting-item?
+  "True if anything about this news `item` is interesting to this `gossip`."
+  [gossip item]
+     (or
+       (interesting-character? gossip (:actor item))
+       (interesting-character? gossip (:other item))
+       (interesting-location? gossip (:location item))
+       (interesting-object? gossip (:object item))
+       (interesting-topic? gossip (:verb item))))
+
+(defn infer
+  "Infer a new knowledge item from this `item`, following this `rule`"
+  [item rule]
+  (reduce merge
+          item
+          (cons
+            {:verb (:verb rule)}
+            (map (fn [k] {k (apply (k rule) (list item))})
+                 (remove
+                   #(= % :verb)
+                   (keys rule))))))
+
+;; (infer {:verb :marry :actor :adam :other :belinda}
+;;        {:verb :marry :actor :other :other :actor})
+;; (infer {:verb :rape :actor :adam :other :belinda}
+;;        {:verb :attack})
+;; (infer {:verb :rape :actor :adam :other :belinda}
+;;        {:verb :sex :actor :other :other :actor})
+
+(defn learn-news-item
+  "Return a gossip like this `gossip`, which has learned this news `item` if
+  it is of interest to them."
+  ([gossip item]
+   (learn-news-item gossip item false))
+  ([gossip item follow-inferences?]
+   (if
+     (interesting-item? gossip item)
+     (let [g (assoc gossip :knowledge
+               (cons
+                 (assoc
+                   item
+                   :nth-hand (if
+                               (number? (:nth-hand item))
+                               (inc (:nth-hand item))
+                               1)
+                   ;; ought to degrate the location
+                   ;; ought to maybe-degrade characters we're not yet interested in
+                   )
+                 ;; ought not to add knowledge items we already have, except
+                 ;; to replace if new item is of increased specificity
+                 (:knowledge gossip)))]
+       (if follow-inferences?
+         (reduce
+           merge
+           g
+           (map
+             #(learn-news-item gossip (infer item %) false)
+             (:inferences (news-topics (:verb item))))))))))
+
diff --git a/src/the_great_game/world/location.clj b/src/the_great_game/world/location.clj
new file mode 100644
index 0000000..6709f30
--- /dev/null
+++ b/src/the_great_game/world/location.clj
@@ -0,0 +1,10 @@
+(ns the-great-game.world.location
+  "Functions dealing with location in the world.")
+
+;;   A 'location' value is a list comprising at most the x/y coordinate location
+;;   and the ids of the settlement and region (possibly hierarchically) that contain
+;;   the location. If the x/y is not local to the home of the receiving agent, they
+;;   won't remember it and won't pass it on; if any of the ids are not interesting
+;;   So location information will degrade progressively as the item is passed along.
+
+;;   It is assumed that the `:home` of a character is a location in this sense.