From 433e9677d4fdb8a695c25bbe848647d7b9bcfbd6 Mon Sep 17 00:00:00 2001
From: Devin Smith <dsmith@walleyesoftware.com>
Date: Tue, 21 Aug 2018 17:20:00 -0500
Subject: [PATCH] added MustacheCustomContext

---
 README.md                                            |  1 +
 .../java/com/samskivert/mustache/BasicCollector.java | 12 ++++++++++++
 .../samskivert/mustache/MustacheCustomContext.java   |  8 ++++++++
 .../java/com/samskivert/mustache/MustacheTest.java   |  9 +++++++++
 4 files changed, 30 insertions(+)
 create mode 100644 src/main/java/com/samskivert/mustache/MustacheCustomContext.java

diff --git a/README.md b/README.md
index 83c1ee2..4cd749f 100644
--- a/README.md
+++ b/README.md
@@ -75,6 +75,7 @@ void executeTemplate (Reader template, Writer out, Map<String, String> data) {
 The execution context can be any Java object. Variables will be resolved via the following
 mechanisms:
 
+  * If the context is a `MustacheCustomContext`, `MustacheCustomContext.get` will be used.
   * If the context is a `Map`, `Map.get` will be used.
   * If a non-void method with the same name as the variable exists, it will be called.
   * If a non-void method named (for variable `foo`) `getFoo` exists, it will be called.
diff --git a/src/main/java/com/samskivert/mustache/BasicCollector.java b/src/main/java/com/samskivert/mustache/BasicCollector.java
index 38e14a9..0765f32 100644
--- a/src/main/java/com/samskivert/mustache/BasicCollector.java
+++ b/src/main/java/com/samskivert/mustache/BasicCollector.java
@@ -35,6 +35,7 @@ public abstract class BasicCollector implements Mustache.Collector
     }
 
     public Mustache.VariableFetcher createFetcher (Object ctx, String name) {
+        if (ctx instanceof MustacheCustomContext) return CUSTOM_FETCHER;
         if (ctx instanceof Map<?,?>) return MAP_FETCHER;
 
         // if the name looks like a number, potentially use one of our 'indexing' fetchers
@@ -65,6 +66,17 @@ public abstract class BasicCollector implements Mustache.Collector
         return null;
     }
 
+    protected static final Mustache.VariableFetcher CUSTOM_FETCHER = new Mustache.VariableFetcher() {
+        public Object get (Object ctx, String name) throws Exception {
+            MustacheCustomContext custom = (MustacheCustomContext)ctx;
+            Object val = custom.get(name);
+            return val == null ? Template.NO_FETCHER_FOUND : val;
+        }
+        @Override public String toString () {
+            return "CUSTOM_FETCHER";
+        }
+    };
+
     protected static final Mustache.VariableFetcher MAP_FETCHER = new Mustache.VariableFetcher() {
         public Object get (Object ctx, String name) throws Exception {
             Map<?,?> map = (Map<?,?>)ctx;
diff --git a/src/main/java/com/samskivert/mustache/MustacheCustomContext.java b/src/main/java/com/samskivert/mustache/MustacheCustomContext.java
new file mode 100644
index 0000000..2f9d5cb
--- /dev/null
+++ b/src/main/java/com/samskivert/mustache/MustacheCustomContext.java
@@ -0,0 +1,8 @@
+package com.samskivert.mustache;
+
+/**
+ * Provides a simple interface for callers to implement their own logic for contextual values.
+ */
+public interface MustacheCustomContext {
+    Object get(String name) throws Exception;
+}
diff --git a/src/test/java/com/samskivert/mustache/MustacheTest.java b/src/test/java/com/samskivert/mustache/MustacheTest.java
index f0f5738..ce446ae 100644
--- a/src/test/java/com/samskivert/mustache/MustacheTest.java
+++ b/src/test/java/com/samskivert/mustache/MustacheTest.java
@@ -45,6 +45,15 @@ public class MustacheTest extends SharedTests
         });
     }
 
+    @Test public void testMustacheCustomContext() {
+        test("bar", "{{foo}}", new MustacheCustomContext() {
+            @Override
+            public Object get(String name) {
+                return "foo".equals(name) ? "bar" : null;
+            }
+        });
+    }
+
     public interface HasDefault {
         default String getFoo () { return "bar"; }
     }