LibMarkdown: Add LineIterator

LineIterator wraps a vector's ConstIterator, to provide an iterator that
can work on indented container blocks (like lists and blockquotes).

Userland/Libraries/LibMarkdown/CMakeLists.txt

@@ -4,6 +4,7 @@ set(SOURCES
     Document.cpp
     Heading.cpp
     HorizontalRule.cpp
+    LineIterator.cpp
     List.cpp
     Paragraph.cpp
     Table.cpp

Userland/Libraries/LibMarkdown/CodeBlock.cpp

@@ -56,7 +56,7 @@ String CodeBlock::render_for_terminal(size_t) const
 
 static Regex<ECMA262> style_spec_re("\\s*([\\*_]*)\\s*([^\\*_\\s]*).*");
 
-OwnPtr<CodeBlock> CodeBlock::parse(Vector<StringView>::ConstIterator& lines)
+OwnPtr<CodeBlock> CodeBlock::parse(LineIterator& lines)
 {
     if (lines.is_end())
         return {};

Userland/Libraries/LibMarkdown/CodeBlock.h

@@ -8,6 +8,7 @@
 
 #include <AK/OwnPtr.h>
 #include <LibMarkdown/Block.h>
+#include <LibMarkdown/LineIterator.h>
 #include <LibMarkdown/Text.h>
 
 namespace Markdown {
@@ -24,7 +25,7 @@ public:
 
     virtual String render_to_html() const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
-    static OwnPtr<CodeBlock> parse(Vector<StringView>::ConstIterator& lines);
+    static OwnPtr<CodeBlock> parse(LineIterator& lines);
 
 private:
     String m_code;

Userland/Libraries/LibMarkdown/ContainerBlock.cpp

@@ -39,7 +39,7 @@ String ContainerBlock::render_for_terminal(size_t view_width) const
 }
 
 template<typename BlockType>
-static bool try_parse_block(Vector<StringView>::ConstIterator& lines, NonnullOwnPtrVector<Block>& blocks)
+static bool try_parse_block(LineIterator& lines, NonnullOwnPtrVector<Block>& blocks)
 {
     OwnPtr<BlockType> block = BlockType::parse(lines);
     if (!block)
@@ -48,7 +48,7 @@ static bool try_parse_block(Vector<StringView>::ConstIterator& lines, NonnullOwn
     return true;
 }
 
-OwnPtr<ContainerBlock> ContainerBlock::parse(Vector<StringView>::ConstIterator& lines)
+OwnPtr<ContainerBlock> ContainerBlock::parse(LineIterator& lines)
 {
     NonnullOwnPtrVector<Block> blocks;
 

Userland/Libraries/LibMarkdown/ContainerBlock.h

@@ -10,6 +10,7 @@
 #include <AK/OwnPtr.h>
 #include <AK/String.h>
 #include <LibMarkdown/Block.h>
+#include <LibMarkdown/LineIterator.h>
 
 namespace Markdown {
 
@@ -25,7 +26,7 @@ public:
     virtual String render_to_html() const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
 
-    static OwnPtr<ContainerBlock> parse(Vector<StringView>::ConstIterator& lines);
+    static OwnPtr<ContainerBlock> parse(LineIterator& lines);
 
 private:
     NonnullOwnPtrVector<Block> m_blocks;

Userland/Libraries/LibMarkdown/Document.cpp

@@ -6,13 +6,8 @@
  */
 
 #include <AK/StringBuilder.h>
-#include <LibMarkdown/CodeBlock.h>
 #include <LibMarkdown/Document.h>
-#include <LibMarkdown/Heading.h>
-#include <LibMarkdown/HorizontalRule.h>
-#include <LibMarkdown/List.h>
-#include <LibMarkdown/Paragraph.h>
-#include <LibMarkdown/Table.h>
+#include <LibMarkdown/LineIterator.h>
 
 namespace Markdown {
 
@@ -49,7 +44,7 @@ String Document::render_for_terminal(size_t view_width) const
 OwnPtr<Document> Document::parse(const StringView& str)
 {
     const Vector<StringView> lines_vec = str.lines();
-    auto lines = lines_vec.begin();
+    LineIterator lines(lines_vec.begin());
     return make<Document>(ContainerBlock::parse(lines));
 }
 

Userland/Libraries/LibMarkdown/Heading.cpp

@@ -35,7 +35,7 @@ String Heading::render_for_terminal(size_t) const
     return builder.build();
 }
 
-OwnPtr<Heading> Heading::parse(Vector<StringView>::ConstIterator& lines)
+OwnPtr<Heading> Heading::parse(LineIterator& lines)
 {
     if (lines.is_end())
         return {};

Userland/Libraries/LibMarkdown/Heading.h

@@ -10,6 +10,7 @@
 #include <AK/StringView.h>
 #include <AK/Vector.h>
 #include <LibMarkdown/Block.h>
+#include <LibMarkdown/LineIterator.h>
 #include <LibMarkdown/Text.h>
 
 namespace Markdown {
@@ -26,7 +27,7 @@ public:
 
     virtual String render_to_html() const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
-    static OwnPtr<Heading> parse(Vector<StringView>::ConstIterator& lines);
+    static OwnPtr<Heading> parse(LineIterator& lines);
 
 private:
     Text m_text;

Userland/Libraries/LibMarkdown/HorizontalRule.cpp

@@ -24,7 +24,7 @@ String HorizontalRule::render_for_terminal(size_t view_width) const
     return builder.to_string();
 }
 
-OwnPtr<HorizontalRule> HorizontalRule::parse(Vector<StringView>::ConstIterator& lines)
+OwnPtr<HorizontalRule> HorizontalRule::parse(LineIterator& lines)
 {
     if (lines.is_end())
         return {};

Userland/Libraries/LibMarkdown/HorizontalRule.h

@@ -10,6 +10,7 @@
 #include <AK/StringView.h>
 #include <AK/Vector.h>
 #include <LibMarkdown/Block.h>
+#include <LibMarkdown/LineIterator.h>
 
 namespace Markdown {
 
@@ -22,7 +23,7 @@ public:
 
     virtual String render_to_html() const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
-    static OwnPtr<HorizontalRule> parse(Vector<StringView>::ConstIterator& lines);
+    static OwnPtr<HorizontalRule> parse(LineIterator& lines);
 };
 
 }

Userland/Libraries/LibMarkdown/LineIterator.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2021, Peter Elliott <pelliott@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibMarkdown/LineIterator.h>
+
+namespace Markdown {
+
+bool LineIterator::is_indented(StringView const& line) const
+{
+    if (line.is_whitespace())
+        return true;
+
+    if (line.length() < m_indent)
+        return false;
+
+    for (size_t i = 0; i < m_indent; ++i) {
+        if (line[i] != ' ')
+            return false;
+    }
+
+    return true;
+}
+
+bool LineIterator::is_end() const
+{
+    return m_iterator.is_end() || (!m_ignore_prefix_mode && !is_indented(*m_iterator));
+}
+
+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);
+}
+
+}

Userland/Libraries/LibMarkdown/LineIterator.h

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2021, Peter Elliott <pelliott@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Iterator.h>
+#include <AK/StringView.h>
+#include <AK/Vector.h>
+
+namespace Markdown {
+
+template<typename T>
+class FakePtr {
+public:
+    FakePtr(T item)
+        : m_item(move(item))
+    {
+    }
+
+    T const* operator->() const { return &m_item; }
+    T* operator->() { return &m_item; }
+
+private:
+    T m_item;
+};
+
+class LineIterator {
+public:
+    LineIterator(Vector<StringView>::ConstIterator const& lines, size_t indent = 0)
+        : m_iterator(lines)
+        , m_indent(indent)
+    {
+    }
+
+    bool is_end() const;
+    StringView operator*() const;
+
+    LineIterator operator++()
+    {
+        reset_ignore_prefix();
+        ++m_iterator;
+        return *this;
+    }
+
+    LineIterator operator++(int)
+    {
+        LineIterator tmp = *this;
+        reset_ignore_prefix();
+        ++m_iterator;
+        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 }; }
+    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; }
+
+private:
+    void reset_ignore_prefix() { m_ignore_prefix_mode = false; }
+    bool is_indented(StringView const& line) const;
+
+    Vector<StringView>::ConstIterator m_iterator;
+    size_t m_indent;
+    bool m_ignore_prefix_mode { false };
+};
+
+}

Userland/Libraries/LibMarkdown/List.cpp

@@ -46,7 +46,7 @@ String List::render_for_terminal(size_t) const
     return builder.build();
 }
 
-OwnPtr<List> List::parse(Vector<StringView>::ConstIterator& lines)
+OwnPtr<List> List::parse(LineIterator& lines)
 {
     Vector<Text> items;
     bool is_ordered = false;

Userland/Libraries/LibMarkdown/List.h

@@ -9,6 +9,7 @@
 #include <AK/OwnPtr.h>
 #include <AK/Vector.h>
 #include <LibMarkdown/Block.h>
+#include <LibMarkdown/LineIterator.h>
 #include <LibMarkdown/Text.h>
 
 namespace Markdown {
@@ -25,7 +26,7 @@ public:
     virtual String render_to_html() const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
 
-    static OwnPtr<List> parse(Vector<StringView>::ConstIterator& lines);
+    static OwnPtr<List> parse(LineIterator& lines);
 
 private:
     // TODO: List items should be considered blocks of their own kind.

Userland/Libraries/LibMarkdown/Table.cpp

@@ -96,7 +96,7 @@ String Table::render_to_html() const
     return builder.to_string();
 }
 
-OwnPtr<Table> Table::parse(Vector<StringView>::ConstIterator& lines)
+OwnPtr<Table> Table::parse(LineIterator& lines)
 {
     auto peek_it = lines;
     auto first_line = *peek_it;
@@ -178,7 +178,7 @@ OwnPtr<Table> Table::parse(Vector<StringView>::ConstIterator& lines)
     size_t row_count = 0;
     ++lines;
     while (!lines.is_end()) {
-        auto& line = *lines;
+        auto line = *lines;
         if (!line.starts_with('|'))
             break;
 

Userland/Libraries/LibMarkdown/Table.h

@@ -9,6 +9,7 @@
 #include <AK/NonnullOwnPtrVector.h>
 #include <AK/OwnPtr.h>
 #include <LibMarkdown/Block.h>
+#include <LibMarkdown/LineIterator.h>
 #include <LibMarkdown/Text.h>
 
 namespace Markdown {
@@ -33,7 +34,7 @@ public:
 
     virtual String render_to_html() const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
-    static OwnPtr<Table> parse(Vector<StringView>::ConstIterator& lines);
+    static OwnPtr<Table> parse(LineIterator& lines);
 
 private:
     Vector<Column> m_columns;