From 05a5f9c124adc34278026748ba03c55e232810fd Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Wed, 12 Mar 2014 13:39:12 -0700
Subject: [PATCH] Add function for notifying documents of edits

---
 include/tree_sitter/runtime.h |  2 ++
 spec/runtime/parser_spec.cc   | 63 ++++++++++++++++++++++++++++-------
 src/runtime/document.c        |  7 ++++
 3 files changed, 60 insertions(+), 12 deletions(-)

diff --git a/include/tree_sitter/runtime.h b/include/tree_sitter/runtime.h
index cff6a4d2..6d883ecf 100644
--- a/include/tree_sitter/runtime.h
+++ b/include/tree_sitter/runtime.h
@@ -59,6 +59,8 @@ void ts_document_free(ts_document *doc);
 void ts_document_set_parser(ts_document *doc, ts_parse_config parser);
 void ts_document_set_input(ts_document *doc, ts_input input);
 void ts_document_set_input_string(ts_document *doc, const char *text);
+void ts_document_edit(ts_document *doc, size_t position, size_t deleted_bytes, size_t inserted_bytes);
+
 const ts_tree * ts_document_tree(const ts_document *doc);
 const char * ts_document_string(const ts_document *doc);
 
diff --git a/spec/runtime/parser_spec.cc b/spec/runtime/parser_spec.cc
index 15cf1af2..895a7a86 100644
--- a/spec/runtime/parser_spec.cc
+++ b/spec/runtime/parser_spec.cc
@@ -5,32 +5,71 @@ extern ts_parse_config ts_parse_config_json;
 
 START_TEST
 
-describe("reading from an input", [&]() {
+describe("parsing", [&]() {
     ts_document *doc;
+    SpyReader *reader;
 
     before_each([&]() {
         doc = ts_document_make();
         ts_document_set_parser(doc, ts_parse_config_json);
+
+        reader = new SpyReader("{ \"key\": [1, 2] }", 5);
+        ts_document_set_input(doc, reader->input);
     });
 
     after_each([&]() {
         ts_document_free(doc);
+        delete reader;
     });
 
+    it("parses the input", [&]() {
+        AssertThat(string(ts_document_string(doc)), Equals(
+            "(value "
+                "(object "
+                    "(string) "
+                    "(value (array "
+                        "(value (number)) "
+                        "(value (number))))))"));
+    });
+    
     it("reads the entire input", [&]() {
-        SpyReader reader("\"ok go do it!\"", 3);
-        ts_document_set_input(doc, reader.input);
-
-        AssertThat(string(ts_document_string(doc)), Equals("(value (string))"));
-        AssertThat(reader.chunks_read, Equals(vector<string>({
-            "\"ok",
-            " go",
-            " do",
-            " it",
-            "!\"",
+        AssertThat(reader->chunks_read, Equals(vector<string>({
+            "{ \"ke",
+            "y\": [",
+            "1, 2]",
+            " }",
             ""
         })));
     });
+
+    describe("modifying the input", [&]() {
+        before_each([&]() {
+            size_t position(string("{ \"key\": [1, 2]").length());
+            string inserted_text(", \"key2\": 4 ");
+
+            reader->content.insert(position, inserted_text);
+            ts_document_edit(doc, position, 0, inserted_text.length());
+        });
+
+        it("updates the parse tree", [&]() {
+            AssertThat(string(ts_document_string(doc)), Equals(
+                "(value "
+                    "(object "
+                        "(string) "
+                        "(value (array "
+                            "(value (number)) "
+                            "(value (number)))) "
+                        "(string) "
+                        "(value (number))))"
+            ));
+        });
+        
+        it_skip("re-reads only the changed portion of the input", [&]() {
+            AssertThat(reader->chunks_read, Equals(vector<string>({
+                ""
+            })));
+        });
+    });
 });
 
-END_TEST
\ No newline at end of file
+END_TEST
diff --git a/src/runtime/document.c b/src/runtime/document.c
index 26e33823..8a65f495 100644
--- a/src/runtime/document.c
+++ b/src/runtime/document.c
@@ -4,6 +4,7 @@
 struct ts_document {
     ts_parse_config parse_config;
     const ts_tree *tree;
+    ts_input input;
     size_t error_count;
 };
 
@@ -28,9 +29,15 @@ const char * ts_document_string(const ts_document *document) {
 }
 
 void ts_document_set_input(ts_document *document, ts_input input) {
+    document->input = input;
     document->tree = document->parse_config.parse_fn(input);
 }
 
+void ts_document_edit(ts_document *document, size_t position, size_t bytes_removed, size_t bytes_inserted) {
+    document->input.seek_fn(document->input.data, 0);
+    document->tree = document->parse_config.parse_fn(document->input);
+}
+
 typedef struct {
     const char *string;
     size_t position;