From d5e3716ebae2654150401e5d809d51905b66fb56 Mon Sep 17 00:00:00 2001
From: Richard Newman <rnewman@twinql.com>
Date: Thu, 4 Aug 2016 16:40:03 -0700
Subject: [PATCH] Turn Source into a protocol. Allow source->from to switch on
 attribute.

---
 src/datomish/query/clauses.cljc | 11 ++++-
 src/datomish/query/source.cljc  | 75 ++++++++++++++++++++++-----------
 test/datomish/test/query.cljc   |  3 +-
 3 files changed, 61 insertions(+), 28 deletions(-)

diff --git a/src/datomish/query/clauses.cljc b/src/datomish/query/clauses.cljc
index 8b3d0dda..ce020148 100644
--- a/src/datomish/query/clauses.cljc
+++ b/src/datomish/query/clauses.cljc
@@ -143,11 +143,14 @@
             Constant
             (constrain-column-to-constant cc col position (:value pattern-part))
 
-            (raise-str "Unknown pattern part " pattern-part))))
+            (raise "Unknown pattern part." {:part pattern-part :clause pattern}))))
 
       cc
       places)))
 
+(defn pattern->attribute [pattern]
+  (second (:pattern pattern)))
+
 ;; Accumulates a pattern into the CC. Returns a new CC.
 (defn apply-pattern-clause
   "Transform a DataScript Pattern instance into the parts needed
@@ -162,7 +165,11 @@
   (when-not (instance? DefaultSrc (:source pattern))
     (raise-str "Non-default sources are not supported in patterns. Pattern: " pattern))
 
-  (let [[table alias] (source->from (:source cc))]   ; e.g., [:datoms :datoms123]
+  ;; TODO: look up the attribute in external bindings if it's a var. Perhaps we
+  ;; already know what it is…
+  (let [[table alias] (source->from
+                        (:source cc)     ; e.g., [:datoms :datoms123]
+                        (pattern->attribute pattern))]
     (apply-pattern-clause-for-alias
 
       ;; Record the new table mapping.
diff --git a/src/datomish/query/source.cljc b/src/datomish/query/source.cljc
index d5df8535..1e488279 100644
--- a/src/datomish/query/source.cljc
+++ b/src/datomish/query/source.cljc
@@ -4,7 +4,15 @@
 
 (ns datomish.query.source
   (:require
-   [datomish.query.transforms :as transforms]))
+     [datomish.query.transforms :as transforms]
+     [datascript.parser
+      #?@(:cljs
+            [:refer [Variable Constant Placeholder]])])
+  #?(:clj
+       (:import [datascript.parser Variable Constant Placeholder])))
+
+(defn- gensym-table-alias [table]
+  (gensym (name table)))
 
 ;;;
 ;;; A source is something that can match patterns. For example:
@@ -24,9 +32,17 @@
 ;;; * Transform constants and attributes into something usable
 ;;;   by the source.
 
+(defprotocol Source
+  (source->from [source attribute]
+    "Returns a pair, `[table alias]` for a pattern with the provided attribute.")
+  (source->constraints [source alias])
+  (attribute-in-source [source attribute])
+  (constant-in-source [source constant]))
+
 (defrecord
-  Source
-  [table               ; e.g., :datoms
+  DatomsSource
+  [table               ; Typically :datoms.
+   fts-view            ; Typically :fulltext_datoms.
    columns             ; e.g., [:e :a :v :tx]
 
    ;; `attribute-transform` is a function from attribute to constant value. Used to
@@ -41,29 +57,38 @@
 
    ;; Not currently used.
    make-constraints    ; ?fn [source alias] => [where-clauses]
-   ])
+   ]
+  Source
 
-(defn gensym-table-alias [table]
-  (gensym (name table)))
+  (source->from [source attribute]
+    (let [table 
+          (if (and (instance? Constant attribute)
+                   ;; TODO: look in the DB schema to see if `attribute` is known to not be
+                   ;; a fulltext attribute.
+                   true)
+            (:table source)
+
+            ;; It's variable. We must act as if it could be a fulltext datom.
+            (:fts-view source))]
+      [table ((:table-alias source) table)]))
+
+  (source->constraints [source alias]
+    (when-let [f (:make-constraints source)]
+      (f alias)))
+
+  (attribute-in-source [source attribute]
+    ((:attribute-transform source) attribute))
+
+  (constant-in-source [source constant]
+    ((:constant-transform source) constant)))
 
 (defn datoms-source [db]
-  (->Source :datoms
-            [:e :a :v :tx :added]
-            transforms/attribute-transform-string
-            transforms/constant-transform-default
-            gensym-table-alias
-            nil))
+  (map->DatomsSource
+    {:table :datoms
+     :fts-view :fulltext_datoms
+     :columns [:e :a :v :tx :added]
+     :attribute-transform transforms/attribute-transform-string
+     :constant-transform transforms/constant-transform-default
+     :table-alias gensym-table-alias
+     :make-constraints nil}))
 
-(defn source->from [source]
-  (let [table (:table source)]
-    [table ((:table-alias source) table)]))
-
-(defn source->constraints [source alias]
-  (when-let [f (:make-constraints source)]
-    (f alias)))
-
-(defn attribute-in-source [source attribute]
-  ((:attribute-transform source) attribute))
-
-(defn constant-in-source [source constant]
-  ((:constant-transform source) constant))
diff --git a/test/datomish/test/query.cljc b/test/datomish/test/query.cljc
index ffeef40d..2518a5a6 100644
--- a/test/datomish/test/query.cljc
+++ b/test/datomish/test/query.cljc
@@ -26,8 +26,9 @@
        (fgensym s (dec (swap! counter inc)))))))
 
 (defn mock-source [db]
-  (source/map->Source
+  (source/map->DatomsSource
     {:table :datoms
+     :fts-view :fulltext_datoms
      :columns [:e :a :v :tx :added]
      :attribute-transform transforms/attribute-transform-string
      :constant-transform transforms/constant-transform-default