From d149bc1dfd8466ba6a6175c14a9a0c9b604c9490 Mon Sep 17 00:00:00 2001
From: Eric Rykwalder <e.rykwalder@gmail.com>
Date: Wed, 9 Mar 2022 16:55:54 -0500
Subject: [PATCH] add tex parsing

---
 __tests__/extensions.ts | 57 +++++++++++++++++++++++++++++++++
 src/extensions.ts       | 70 +++++++++++++++++++++++++++++++++++++++++
 src/index.ts            |  1 +
 3 files changed, 128 insertions(+)

diff --git a/__tests__/extensions.ts b/__tests__/extensions.ts
index 38e0e29..6679eba 100644
--- a/__tests__/extensions.ts
+++ b/__tests__/extensions.ts
@@ -28,6 +28,9 @@ const specParser = new SpecParser(parser, {
   YF: "YAMLFrontMatter",
   ym: "YAMLMarker",
   yc: "YAMLContent",
+  XB: "TexBlock",
+  XI: "TexInline",
+  xm: "TexMarker",
 });
 
 /*
@@ -189,6 +192,60 @@ Line 5}
     `
   );
 
+  test(
+    "Tex Block (End Leaf)",
+    `
+{P:plaintext}
+{XB:{xm:$$}tex content
+- still tex
+> and still tex
+{xm:$$}}
+    `
+  );
+
+  test(
+    "Tex Block (Tailing Text)",
+    `
+{XB:{xm:$$}tex content{xm:$$}} {P:plaintext}
+    `
+  );
+
+  test(
+    "Tex Block (Unterminated)",
+    `
+{XB:{xm:$$}tex content
+
+# this is never terminated
+    }`
+  );
+
+  test(
+    "Tex Inline (1)",
+    `
+{P:plaintext {XI:{xm:$}tex content{xm:$}} more plaintext}
+
+{P:{XI:{xm:$}1.234{xm:$}}}
+    `
+  );
+
+  test(
+    "Tex Inline (2)",
+    `
+{P:$not tex$1.234}
+
+{P:$also not tex $}
+
+{P:$ still not tex$}
+
+{P:{XI:{xm:$}actually tex
+{xm:$}}}
+
+{P:{XI:{xm:$}tex
+more text
+{xm:$}}}
+    `
+  );
+
   test(
     "YAMLFrontMatter",
     `
diff --git a/src/extensions.ts b/src/extensions.ts
index 0309d32..2b23783 100644
--- a/src/extensions.ts
+++ b/src/extensions.ts
@@ -317,6 +317,75 @@ export const TaskList: MarkdownConfig = {
 };
 /* End Copyright */
 
+export const Tex: MarkdownConfig = {
+  defineNodes: ["TexBlock", "TexInline", "TexMarker"],
+  parseBlock: [
+    {
+      name: "TexBlock",
+      endLeaf: (_, line: Line) =>
+        line.text.slice(line.pos, line.pos + 2) == "$$",
+      // This is an imperfect match for HyperMD, because
+      // in HyperMD the block can start even in inline content.
+      parse(cx: BlockContext, line: Line) {
+        if (line.text.slice(line.pos, line.pos + 2) != "$$") {
+          return false;
+        }
+        const start = cx.lineStart + line.pos;
+        const markers = [cx.elt("TexMarker", start, start + 2)];
+        const regex = /(^|[^\\])\$\$/;
+        let remaining = line.text.slice(line.pos + 2);
+        let startOffset = 2;
+        let match;
+        while (!(match = regex.exec(remaining)) && cx.nextLine()) {
+          remaining = line.text;
+          startOffset = 0;
+        }
+        let end;
+        if (match) {
+          const lineEnd = match.index + match[0].length + startOffset;
+          end = cx.lineStart + lineEnd;
+          markers.push(cx.elt("TexMarker", end - 2, end));
+          if (
+            lineEnd == line.text.length ||
+            /^\s+$/.test(line.text.slice(lineEnd))
+          ) {
+            cx.nextLine();
+          } else {
+            line.pos = line.skipSpace(lineEnd);
+          }
+        } else {
+          end = cx.lineStart + line.text.length;
+        }
+        cx.addElement(cx.elt("TexBlock", start, end, markers));
+        return true;
+      },
+    },
+  ],
+  parseInline: [
+    {
+      name: "TexInline",
+      parse(cx: InlineContext, next: number, pos: number) {
+        let match = /^\$[^$\s]/.exec(cx.text.slice(pos - cx.offset));
+        if (!match) {
+          return -1;
+        }
+        const start = pos;
+        match = /[^\t \\]\$(\D|$)/.exec(cx.text.slice(pos - cx.offset + 1));
+        if (!match) {
+          return -1;
+        }
+        const end = start + 1 + match.index + 2;
+        return cx.addElement(
+          cx.elt("TexInline", start, end, [
+            cx.elt("TexMarker", start, start + 1),
+            cx.elt("TexMarker", end - 1, end),
+          ])
+        );
+      },
+    },
+  ],
+};
+
 export const YAMLFrontMatter: MarkdownConfig = {
   defineNodes: ["YAMLFrontMatter", "YAMLMarker", "YAMLContent"],
   parseBlock: [
@@ -357,6 +426,7 @@ export const ObsidianMDExtensions = [
   Strikethrough,
   Table,
   TaskList,
+  Tex,
   YAMLFrontMatter,
 ];
 
diff --git a/src/index.ts b/src/index.ts
index 1e011bf..b54bba3 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -5,5 +5,6 @@ export {
   ObsidianMDExtensions,
   parser,
   TaskList,
+  Tex,
   YAMLFrontMatter,
 } from "./extensions";