From b00e8ccf423c2c3a31b21643977134d152f64289 Mon Sep 17 00:00:00 2001
From: Gustav Westling <gustav@polar.sh>
Date: Tue, 19 Mar 2024 13:14:08 +0100
Subject: [PATCH] Multiline footnotes

---
 index.compiler.spec.tsx | 143 ++++++++++++++++++++++++++++++++++++++++
 index.tsx               |  36 +++++++++-
 2 files changed, 178 insertions(+), 1 deletion(-)

diff --git a/index.compiler.spec.tsx b/index.compiler.spec.tsx
index 05453f2c..fef10ea8 100644
--- a/index.compiler.spec.tsx
+++ b/index.compiler.spec.tsx
@@ -3529,6 +3529,149 @@ describe('footnotes', () => {
       </span>
     `)
   })
+
+  it('should handle multiline footnotes', () => {
+    render(
+      compiler(theredoc`
+        foo[^abc] bar
+
+        [^abc]: Baz
+          line2
+          line3
+
+        After footnotes content
+      `)
+    )
+
+    expect(root.innerHTML).toMatchInlineSnapshot(`
+      <div>
+        <div>
+          <p>
+            foo
+            <a href="#abc">
+              <sup>
+                abc
+              </sup>
+            </a>
+            bar
+          </p>
+          <p>
+            After footnotes content
+          </p>
+        </div>
+        <footer>
+          <div id="abc">
+            abc: Baz
+        line2
+        line3
+          </div>
+        </footer>
+      </div>
+    `)
+  })
+
+  it('should handle mixed multiline and singleline footnotes', () => {
+    render(
+      compiler(theredoc`
+        a[^a] b[^b] c[^c]
+
+        [^a]: single
+        [^b]: bbbb
+          bbbb
+          bbbb
+        [^c]: single-c
+      `)
+    )
+
+    expect(root.innerHTML).toMatchInlineSnapshot(`
+      <div>
+        <p>
+          a
+          <a href="#a">
+            <sup>
+              a
+            </sup>
+          </a>
+          b
+          <a href="#b">
+            <sup>
+              b
+            </sup>
+          </a>
+          c
+          <a href="#c">
+            <sup>
+              c
+            </sup>
+          </a>
+        </p>
+        <footer>
+          <div id="a">
+            a: single
+          </div>
+          <div id="b">
+            b: bbbb
+        bbbb
+        bbbb
+          </div>
+          <div id="c">
+            c: single-c
+          </div>
+        </footer>
+      </div>
+    `)
+  })
+
+  it('should handle indented multiline footnote', () => {
+    render(
+      compiler(theredoc`
+        Here's a simple footnote,[^1] and here's a longer one.[^bignote]
+
+        [^1]: This is the first footnote.
+        
+        [^bignote]: Here's one with multiple paragraphs and code.
+
+            Indent paragraphs to include them in the footnote.
+
+            \`{ my code }\`
+
+            Add as many paragraphs as you like.
+      `)
+    )
+
+    expect(root.innerHTML).toMatchInlineSnapshot(`
+      <div>
+        <p>
+          Here's a simple footnote,
+          <a href="#1">
+            <sup>
+              1
+            </sup>
+          </a>
+          and here's a longer one.
+          <a href="#bignote">
+            <sup>
+              bignote
+            </sup>
+          </a>
+        </p>
+        <footer>
+          <div id="1">
+            1: This is the first footnote.
+          </div>
+          <div id="bignote">
+            bignote: Here's one with multiple paragraphs and code.
+
+          Indent paragraphs to include them in the footnote.
+            <code>
+              { my code }
+            </code>
+            Add as many paragraphs as you like.
+          </div>
+        </footer>
+      </div>
+      `)
+  })
 })
 
 describe('options.namedCodesToUnicode', () => {
diff --git a/index.tsx b/index.tsx
index cb68d27c..80157acd 100644
--- a/index.tsx
+++ b/index.tsx
@@ -187,7 +187,41 @@ const CODE_BLOCK_R = /^(?: {4}[^\n]+\n*)+(?:\n *)+\n?/
 const CODE_INLINE_R = /^(`+)\s*([\s\S]*?[^`])\s*\1(?!`)/
 const CONSECUTIVE_NEWLINE_R = /^(?:\n *)*\n/
 const CR_NEWLINE_R = /\r\n?/g
-const FOOTNOTE_R = /^\[\^([^\]]+)](:.*)\n/
+
+/**
+ * Matches footnotes on the format:
+ *
+ * [^key]: value
+ *
+ * Matches multiline footnotes
+ *
+ * [^key]: row
+ * row
+ * row
+ * 
+ * And empty lines in indented multiline footnotes
+ * 
+ * [^key]: indented with 
+ *     row
+ * 
+ *     row
+ *
+ * Explanation:
+ *
+ * 1. Look for the starting tag, eg: [^key]
+ *    ^\[\^([^\]]+)]
+ *
+ * 2. The first line starts with a colon, and continues for the rest of the line
+ *   :(.*)
+ *
+ * 3. Parse as many additional lines as possible. Matches new non-empty lines that doesn't begin with a new footnote definition.
+ *    (\n(?!\[\^).+)
+ * 
+ * 4. ...or allows for repeated newlines if the next line begins with at least four whitespaces.
+ *    (\n+ {4,}.*)
+ */
+const FOOTNOTE_R = /^\[\^([^\]]+)](:(.*)((\n+ {4,}.*)|(\n(?!\[\^).+))*)/
+
 const FOOTNOTE_REFERENCE_R = /^\[\^([^\]]+)]/
 const FORMFEED_R = /\f/g
 const FRONT_MATTER_R = /^---[ \t]*\n(.|\n)*\n---[ \t]*\n/