1 files changed, 44 insertions, 0 deletions
diff --git a/packages/gitbook/src/api/decodePage.js b/packages/gitbook/src/api/decodePage.js
new file mode 100644
index 0000000..4fd78af
--- /dev/null
+++ b/packages/gitbook/src/api/decodePage.js
@@ -0,0 +1,44 @@
+const deprecate = require('./deprecate');
+
+/**
+    Decode changes from a JS API to a page object.
+    Only the content can be edited by plugin's hooks.
+
+    @param {Output} output
+    @param {Page} page: page instance to edit
+    @param {Object} result: result from API
+    @return {Page}
+*/
+function decodePage(output, page, result) {
+    const originalContent = page.getContent();
+
+    // No returned value
+    // Existing content will be used
+    if (!result) {
+        return page;
+    }
+
+    deprecate.disable('page.sections');
+
+    // GitBook 3
+    // Use returned page.content if different from original content
+    if (result.content != originalContent) {
+        page = page.set('content', result.content);
+    }
+
+    // GitBook 2 compatibility
+    // Finally, use page.sections
+    else if (result.sections) {
+        page = page.set('content',
+            result.sections.map(function(section) {
+                return section.content;
+            }).join('\n')
+        );
+    }
+
+    deprecate.enable('page.sections');
+
+    return page;
+}
+
+module.exports = decodePage;