3 files changed, 78 insertions, 31 deletions

diff --git a/Userland/Libraries/LibMarkdown/LineIterator.cpp b/Userland/Libraries/LibMarkdown/LineIterator.cpp
index 6966112be8..ec77ca1642 100644
--- a/Userland/Libraries/LibMarkdown/LineIterator.cpp
+++ b/Userland/Libraries/LibMarkdown/LineIterator.cpp
@@ -4,38 +4,62 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Format.h>
 #include <LibMarkdown/LineIterator.h>
 
 namespace Markdown {
 
-bool LineIterator::is_indented(StringView const& line) const
+void LineIterator::reset_ignore_prefix()
 {
-    if (line.is_whitespace())
-        return true;
+    for (auto& context : m_context_stack) {
+        context.ignore_prefix = false;
+    }
+}
 
-    if (line.length() < m_indent)
-        return false;
+Optional<StringView> LineIterator::match_context(StringView const& line) const
+{
+    bool is_ws = line.is_whitespace();
+    size_t offset = 0;
+    for (auto& context : m_context_stack) {
+        switch (context.type) {
+        case Context::Type::ListItem:
+            if (is_ws)
+                break;
 
-    for (size_t i = 0; i < m_indent; ++i) {
-        if (line[i] != ' ')
-            return false;
-    }
+            if (offset + context.indent > line.length())
+                return {};
+
+            if (!context.ignore_prefix && !line.substring_view(offset, context.indent).is_whitespace())
+                return {};
 
-    return true;
+            offset += context.indent;
+
+            break;
+        case Context::Type::BlockQuote:
+            for (; offset < line.length() && line[offset] == ' '; ++offset) { }
+            if (offset >= line.length() || line[offset] != '>') {
+                return {};
+            }
+            ++offset;
+            break;
+        }
+
+        if (offset > line.length())
+            return {};
+    }
+    return line.substring_view(offset);
 }
 
 bool LineIterator::is_end() const
 {
-    return m_iterator.is_end() || (!m_ignore_prefix_mode && !is_indented(*m_iterator));
+    return m_iterator.is_end() || !match_context(*m_iterator).has_value();
 }
 
 StringView LineIterator::operator*() const
 {
-    VERIFY(m_ignore_prefix_mode || is_indented(*m_iterator));
-    if (m_iterator->is_whitespace())
-        return *m_iterator;
-
-    return m_iterator->substring_view(m_indent);
+    auto line = match_context(*m_iterator);
+    VERIFY(line.has_value());
+    return line.value();
 }
 
 }
diff --git a/Userland/Libraries/LibMarkdown/LineIterator.h b/Userland/Libraries/LibMarkdown/LineIterator.h
index 04faad3b4e..8109e1d8e4 100644
--- a/Userland/Libraries/LibMarkdown/LineIterator.h
+++ b/Userland/Libraries/LibMarkdown/LineIterator.h
@@ -29,9 +29,22 @@ private:
 
 class LineIterator {
 public:
-    LineIterator(Vector<StringView>::ConstIterator const& lines, size_t indent = 0)
+    struct Context {
+        enum class Type {
+            ListItem,
+            BlockQuote,
+        };
+
+        Type type;
+        size_t indent;
+        bool ignore_prefix;
+
+        static Context list_item(size_t indent) { return { Type::ListItem, indent, true }; }
+        static Context block_quote() { return { Type::BlockQuote, 0, false }; }
+    };
+
+    LineIterator(Vector<StringView>::ConstIterator const& lines)
         : m_iterator(lines)
-        , m_indent(indent)
     {
     }
 
@@ -53,23 +66,35 @@ public:
         return tmp;
     }
 
-    LineIterator operator+(ptrdiff_t delta) const { return LineIterator { m_iterator + delta, m_indent }; }
-    LineIterator operator-(ptrdiff_t delta) const { return LineIterator { m_iterator - delta, m_indent }; }
+    LineIterator operator+(ptrdiff_t delta) const
+    {
+        LineIterator copy = *this;
+        copy.reset_ignore_prefix();
+        copy.m_iterator = copy.m_iterator + delta;
+        return copy;
+    }
+
+    LineIterator operator-(ptrdiff_t delta) const
+    {
+        LineIterator copy = *this;
+        copy.reset_ignore_prefix();
+        copy.m_iterator = copy.m_iterator - delta;
+        return copy;
+    }
+
     ptrdiff_t operator-(LineIterator other) const { return m_iterator - other.m_iterator; }
 
     FakePtr<StringView> operator->() const { return FakePtr<StringView>(operator*()); }
 
-    size_t indent() const { return m_indent; }
-    void set_indent(size_t indent) { m_indent = indent; }
-    void ignore_next_prefix() { m_ignore_prefix_mode = true; }
+    void push_context(Context context) { m_context_stack.append(move(context)); }
+    void pop_context() { m_context_stack.take_last(); }
 
 private:
-    void reset_ignore_prefix() { m_ignore_prefix_mode = false; }
-    bool is_indented(StringView const& line) const;
+    void reset_ignore_prefix();
+    Optional<StringView> match_context(StringView const& line) const;
 
     Vector<StringView>::ConstIterator m_iterator;
-    size_t m_indent;
-    bool m_ignore_prefix_mode { false };
+    Vector<Context> m_context_stack;
 };
 
 }
diff --git a/Userland/Libraries/LibMarkdown/List.cpp b/Userland/Libraries/LibMarkdown/List.cpp
index 0b4df3584c..5308ec4b47 100644
--- a/Userland/Libraries/LibMarkdown/List.cpp
+++ b/Userland/Libraries/LibMarkdown/List.cpp
@@ -121,16 +121,14 @@ OwnPtr<List> List::parse(LineIterator& lines)
 
         is_tight = is_tight && !has_trailing_blank_lines;
 
-        size_t saved_indent = lines.indent();
-        lines.set_indent(saved_indent + offset);
-        lines.ignore_next_prefix();
+        lines.push_context(LineIterator::Context::list_item(offset));
 
         auto list_item = ContainerBlock::parse(lines);
         is_tight = is_tight && !list_item->has_blank_lines();
         has_trailing_blank_lines = has_trailing_blank_lines || list_item->has_trailing_blank_lines();
         items.append(move(list_item));
 
-        lines.set_indent(saved_indent);
+        lines.pop_context();
 
         first = false;
     }