Batch up async conversions until end of conversion

3 files changed, 159 insertions, 130 deletions

diff --git a/lib/document-to-html.js b/lib/document-to-html.js
index 33b6d46..747e12f 100644
--- a/lib/document-to-html.js
+++ b/lib/document-to-html.js
@@ -1,4 +1,3 @@
-var async = require("async");
 var _ = require("underscore");
 
 var promises = require("./promises");
@@ -12,14 +11,6 @@ var writers = require("./writers");
 exports.DocumentConverter = DocumentConverter;
 
 
-// TODO: investigate tidier solutions
-if (typeof setImmediate === "undefined") {
-    var setImmediate = function(callback) {
-        setTimeout(callback, 0);
-    };
-}
-
-
 function DocumentConverter(options) {
     return {
         convertToHtml: function() {
@@ -44,48 +35,69 @@ function DocumentConversion(options) {
     function convertToHtml(document) {
         var messages = [];
         
-        return promises.nfcall(elementToHtml, document, messages).then(function(html) {
+        var html = elementToHtml(document, messages);
+        
+        var deferredNodes = [];
+        walkHtml(html, function(node) {
+            if (node.type === "deferred") {
+                deferredNodes.push(node);
+            }
+        });
+        var deferredValues = {};
+        return promises.mapSeries(deferredNodes, function(deferred) {
+            return deferred.value().then(function(value) {
+                deferredValues[deferred.id] = value;
+            });
+        }).then(function() {
+            function replaceDeferred(nodes) {
+                return flatMap(nodes, function(node) {
+                    if (node.type === "deferred") {
+                        return deferredValues[node.id];
+                    } else if (node.children) {
+                        return [
+                            _.extend({}, node, {
+                                children: replaceDeferred(node.children)
+                            })
+                        ];
+                    } else {
+                        return [node];
+                    }
+                });
+            }
+            html = replaceDeferred(html);
+            
             var writer = writers.writer({
                 prettyPrint: options.prettyPrint,
                 outputFormat: options.outputFormat
             });
             Html.write(writer, Html.simplify(html));
-            return new results.Result(writer.asString(), messages);
+            return promises.when(new results.Result(writer.asString(), messages));
         });
     }
     
-    function convertElements(elements, messages, callback) {
-        async.mapSeries(elements, function(element, callback) {
-            return elementToHtml(element, messages, callback);
-        }, function(error, results) {
-            if (error) {
-                callback(error);
-            } else {
-                callback(null, _.flatten(results, true));
-            }
+    function convertElements(elements, messages) {
+        return flatMap(elements, function(element) {
+            return elementToHtml(element, messages);
         });
     }
 
-    function elementToHtml(element, messages, callback) {
+    function elementToHtml(element, messages) {
         var handler = elementConverters[element.type];
         if (handler) {
-            handler(element, messages, callback);
+            return handler(element, messages);
         } else {
-            callback();
+            return [];
         }
     }
     
-    function convertParagraph(element, messages, callback) {
+    function convertParagraph(element, messages) {
         var style = styleForParagraph(element, messages);
         
-        setImmediate(function() {
-            convertElements(element.children, messages, function(error, children) {
-                if (!options.ignoreEmptyParagraphs) {
-                    children = [Html.forceWrite].concat(children);
-                }
-                callback(null, Html.pathToNodes(style, children));
-            });
-        });
+        var children = convertElements(element.children, messages);
+        if (!options.ignoreEmptyParagraphs) {
+            children = [Html.forceWrite].concat(children);
+        }
+        return Html.pathToNodes(style, children);
     }
     
     function styleForParagraph(element, messages) {
@@ -101,38 +113,37 @@ function DocumentConversion(options) {
         }
     }
     
-    function convertRun(run, messages, callback) {
+    function convertRun(run, messages) {
+        var style;
         if (run.styleId) {
-            var style = findStyle(run);
+            style = findStyle(run);
             if (!style) {
                 messages.push(unrecognisedStyleWarning("run", run));
             }
         }
-        convertElements(run.children, messages, function(error, children) {
-            var result = children;
-            if (run.isStrikethrough) {
-                result = convertRunProperty(result, "strikethrough", "s");
-            }
-            if (run.isUnderline) {
-                result = convertUnderline(result);
-            }
-            if (run.verticalAlignment === documents.verticalAlignment.subscript) {
-                result = wrapInNonFreshElement(result, "sub");
-            }
-            if (run.verticalAlignment === documents.verticalAlignment.superscript) {
-                result = wrapInNonFreshElement(result, "sup");
-            }
-            if (run.isItalic) {
-                result = convertRunProperty(result, "italic", "em");
-            }
-            if (run.isBold) {
-                result = convertRunProperty(result, "bold", "strong");
-            }
-            if (style) {
-                result = Html.pathToNodes(style.to, result);
-            }
-            callback(null, result);
-        });
+        var result = convertElements(run.children, messages);
+        if (run.isStrikethrough) {
+            result = convertRunProperty(result, "strikethrough", "s");
+        }
+        if (run.isUnderline) {
+            result = convertUnderline(result);
+        }
+        if (run.verticalAlignment === documents.verticalAlignment.subscript) {
+            result = wrapInNonFreshElement(result, "sub");
+        }
+        if (run.verticalAlignment === documents.verticalAlignment.superscript) {
+            result = wrapInNonFreshElement(result, "sup");
+        }
+        if (run.isItalic) {
+            result = convertRunProperty(result, "italic", "em");
+        }
+        if (run.isBold) {
+            result = convertRunProperty(result, "bold", "strong");
+        }
+        if (style) {
+            result = Html.pathToNodes(style.to, result);
+        }
+        return result;
     }
     
     function wrapInNonFreshElement(nodes, tagName) {
@@ -174,14 +185,10 @@ function DocumentConversion(options) {
     });
     
     function recoveringConvertImage(convertImage) {
-        return function(image, messages, callback) {
-            convertImage(image, messages, function(error, result) {
-                if (error) {
-                    messages.push(results.warning(error.message));
-                    callback(null, []);
-                } else {
-                    callback(null, result);
-                }
+        return function(image, messages) {
+            return convertImage(image, messages).caught(function(error) {
+                messages.push(results.warning(error.message));
+                return [];
             });
         };
     }
@@ -198,98 +205,92 @@ function DocumentConversion(options) {
         return idPrefix + suffix;
     }
     
-    function convertTable(element, messages, callback) {
-        wrapChildrenInFreshElement(element, "table", messages, callback);
+    function convertTable(element, messages) {
+        return wrapChildrenInFreshElement(element, "table", messages);
     }
     
-    function convertTableRow(element, messages, callback) {
-        wrapChildrenInFreshElement(element, "tr", messages, callback);
+    function convertTableRow(element, messages) {
+        return wrapChildrenInFreshElement(element, "tr", messages);
     }
     
-    function convertTableCell(element, messages, callback) {
-        convertElements(element.children, messages, function(error, children) {
-            var attributes = {};
-            if (element.colSpan !== 1) {
-                attributes.colspan = element.colSpan.toString();
-            }
-            if (element.rowSpan !== 1) {
-                attributes.rowspan = element.rowSpan.toString();
-            }
+    function convertTableCell(element, messages) {
+        var children = convertElements(element.children, messages);
+        var attributes = {};
+        if (element.colSpan !== 1) {
+            attributes.colspan = element.colSpan.toString();
+        }
+        if (element.rowSpan !== 1) {
+            attributes.rowspan = element.rowSpan.toString();
+        }
             
-            callback(null, [
-                Html.freshElement("td", attributes, [Html.forceWrite].concat(children))
-            ]);
-        });
+        return [
+            Html.freshElement("td", attributes, [Html.forceWrite].concat(children))
+        ];
     }
     
-    function wrapChildrenInFreshElement(element, wrapElementName, messages, callback) {
-        convertElements(element.children, messages, function(error, children) {
-            callback(null, [
-                Html.freshElement(wrapElementName, {}, [Html.forceWrite].concat(children))
-            ]);
-        });
+    function wrapChildrenInFreshElement(element, wrapElementName, messages) {
+        var children = convertElements(element.children, messages);
+        return [
+            Html.freshElement(wrapElementName, {}, [Html.forceWrite].concat(children))
+        ];
     }
 
     var elementConverters = {
-        "document": function(document, messages, callback) {
-            convertElements(document.children, messages, function(error, children) {
-                var notes = noteReferences.map(function(noteReference) {
-                    return document.notes.resolve(noteReference);
-                });
-                convertElements(notes, messages, function(error, notesNodes) {
-                    callback(null, children.concat([
-                        Html.freshElement("ol", {}, notesNodes)
-                    ]));
-                });
+        "document": function(document, messages) {
+            var children = convertElements(document.children, messages);
+            var notes = noteReferences.map(function(noteReference) {
+                return document.notes.resolve(noteReference);
             });
+            var notesNodes = convertElements(notes, messages);
+            return children.concat([
+                Html.freshElement("ol", {}, notesNodes)
+            ]);
         },
         "paragraph": convertParagraph,
         "run": convertRun,
-        "text": function(element, messages, callback) {
-            callback(null, [Html.text(element.value)]);
+        "text": function(element, messages) {
+            return [Html.text(element.value)];
         },
-        "tab": function(element, messages, callback) {
-            callback(null, [Html.text("\t")]);
+        "tab": function(element, messages) {
+            return [Html.text("\t")];
         },
-        "hyperlink": function(element, messages, callback) {
+        "hyperlink": function(element, messages) {
             var href = element.anchor ? "#" + htmlId(element.anchor) : element.href;
 
-            convertElements(element.children, messages, function(error, children) {
-                callback(null, [Html.freshElement("a", {href: href}, children)]);
-            });
+            var children = convertElements(element.children, messages);
+            return [Html.freshElement("a", {href: href}, children)];
         },
-        "bookmarkStart": function(element, messages, callback) {
+        "bookmarkStart": function(element, messages) {
             var anchor = Html.freshElement("a", {
                 id: htmlId(element.name)
             }, [Html.forceWrite]);
-            callback(null, [anchor]);
+            return [anchor];
         },
-        "noteReference": function(element, messages, callback) {
+        "noteReference": function(element, messages) {
             noteReferences.push(element);
             var anchor = Html.freshElement("a", {
                 href: "#" + noteHtmlId(element),
                 id: noteRefHtmlId(element)
             }, [Html.text("[" + (noteNumber++) + "]")]);
             
-            callback(null, [Html.freshElement("sup", {}, [anchor])]);
+            return [Html.freshElement("sup", {}, [anchor])];
         },
-        "note": function(element, messages, callback) {
-            convertElements(element.body, messages, function(error, children) {
-                var backLink = Html.elementWithTag(htmlPaths.element("p", {}, {fresh: false}), [
-                    Html.text(" "),
-                    Html.freshElement("a", {href: "#" + noteRefHtmlId(element)}, [Html.text("↑")]),
-                ]);
-                var body = children.concat([backLink]);
-                
-                callback(null, Html.freshElement("li", {id: noteHtmlId(element)}, body));
-            });
+        "note": function(element, messages) {
+            var children = convertElements(element.body, messages);
+            var backLink = Html.elementWithTag(htmlPaths.element("p", {}, {fresh: false}), [
+                Html.text(" "),
+                Html.freshElement("a", {href: "#" + noteRefHtmlId(element)}, [Html.text("↑")]),
+            ]);
+            var body = children.concat([backLink]);
+            
+            return Html.freshElement("li", {id: noteHtmlId(element)}, body);
         },
-        "image": recoveringConvertImage(options.convertImage || defaultConvertImage),
+        "image": deferredConversion(recoveringConvertImage(options.convertImage || defaultConvertImage)),
         "table": convertTable,
         "tableRow": convertTableRow,
         "tableCell": convertTableCell,
-        "lineBreak": function(element, messages, callback) {
-            callback(null, [Html.selfClosingElement("br")]);
+        "lineBreak": function(element, messages) {
+            return [Html.selfClosingElement("br")];
         }
     };
     return {
@@ -297,9 +298,38 @@ function DocumentConversion(options) {
     };
 }
 
+var deferredId = 1;
+
+function deferredConversion(func) {
+    return function(element, messages) {
+        return [
+            {
+                type: "deferred",
+                id: deferredId++,
+                value: function() {
+                    return func(element, messages);
+                }
+            }
+        ];
+    };
+}
+
 function unrecognisedStyleWarning(type, element) {
     return results.warning(
         "Unrecognised " + type + " style: '" + element.styleName + "'" +
         " (Style ID: " + element.styleId + ")"
     );
 }
+
+function flatMap(values, func) {
+    return _.flatten(values.map(func), true);
+}
+
+function walkHtml(nodes, callback) {
+    nodes.forEach(function(node) {
+        callback(node);
+        if (node.children) {
+            walkHtml(node.children, callback);
+        }
+    });
+}
diff --git a/lib/images.js b/lib/images.js
index 6aac18a..fdc3601 100644
--- a/lib/images.js
+++ b/lib/images.js
@@ -4,16 +4,14 @@ var promises = require("./promises");
 var Html = require("./html");
 
 exports.imgElement = function(func) {
-    return function(element, messages, callback) {
+    return function(element, messages) {
         return promises.when(func(element)).then(function(result) {
             var attributes = _.clone(result);
             if (element.altText) {
                 attributes.alt = element.altText;
             }
             return [Html.selfClosingElement("img", attributes)];
-        }).then(function(value) {
-            callback(null, value);
-        }, callback);
+        });
     };
 };
 
diff --git a/lib/promises.js b/lib/promises.js
index 4c10285..24dc34a 100644
--- a/lib/promises.js
+++ b/lib/promises.js
@@ -1,5 +1,5 @@
 var _ = require("underscore");
-var bluebird = require("bluebird/js/main/promise")();
+var bluebird = require("bluebird/js/release/promise")();
 
 exports.defer = bluebird.defer;
 exports.when = bluebird.resolve;
@@ -8,6 +8,7 @@ exports.all = bluebird.all;
 exports.props = bluebird.props;
 exports.reject = bluebird.reject;
 exports.promisify = bluebird.promisify;
+exports.mapSeries = bluebird.mapSeries;
 
 exports.nfcall = function(func) {
     var args = Array.prototype.slice.call(arguments, 1);