Libraries: Add LibMarkdown

Libraries/LibMarkdown/MDText.cpp

@@ -0,0 +1,138 @@
+#include <AK/StringBuilder.h>
+#include <LibMarkdown/MDText.h>
+
+String MDText::render_to_html() const
+{
+    StringBuilder builder;
+
+    Vector<String> open_tags;
+    Style current_style;
+
+    for (auto& span : m_spans) {
+        struct TagAndFlag {
+            String tag;
+            bool Style::*flag;
+        };
+        TagAndFlag tags_and_flags[] = {
+            { "i", &Style::emph },
+            { "b", &Style::strong },
+            { "code", &Style::code }
+        };
+        auto it = open_tags.find([&](const String& open_tag) {
+            for (auto& tag_and_flag : tags_and_flags) {
+                if (open_tag == tag_and_flag.tag && !(span.style.*tag_and_flag.flag))
+                    return true;
+            }
+            return false;
+        });
+
+        if (!it.is_end()) {
+            // We found an open tag that should
+            // not be open for the new span. Close
+            // it and all the open tags that follow
+            // it.
+            for (auto it2 = --open_tags.end(); it2 >= it; --it2) {
+                const String& tag = *it2;
+                builder.appendf("</%s>", tag.characters());
+                for (auto& tag_and_flag : tags_and_flags)
+                    if (tag == tag_and_flag.tag)
+                        current_style.*tag_and_flag.flag = false;
+            }
+            open_tags.shrink(it.index());
+        }
+        for (auto& tag_and_flag : tags_and_flags) {
+            if (current_style.*tag_and_flag.flag != span.style.*tag_and_flag.flag) {
+                open_tags.append(tag_and_flag.tag);
+                builder.appendf("<%s>", tag_and_flag.tag.characters());
+            }
+        }
+
+        current_style = span.style;
+        builder.append(span.text);
+    }
+
+    for (auto it = --open_tags.end(); it >= open_tags.begin(); --it) {
+        const String& tag = *it;
+        builder.appendf("</%s>", tag.characters());
+    }
+
+    return builder.build();
+}
+
+String MDText::render_for_terminal() const
+{
+    StringBuilder builder;
+
+    for (auto& span : m_spans) {
+        bool needs_styling = span.style.strong || span.style.emph || span.style.code;
+        if (needs_styling) {
+            builder.append("\033[");
+            bool first = true;
+            if (span.style.strong || span.style.code) {
+                builder.append('1');
+                first = false;
+            }
+            if (span.style.emph) {
+                if (!first)
+                    builder.append(';');
+                builder.append('4');
+            }
+            builder.append('m');
+        }
+
+        builder.append(span.text.characters());
+
+        if (needs_styling)
+            builder.append("\033[0m");
+    }
+
+    return builder.build();
+}
+
+bool MDText::parse(const StringView& str)
+{
+    Style current_style;
+    int current_span_start = 0;
+
+    for (int offset = 0; offset < str.length(); offset++) {
+        char ch = str[offset];
+
+        bool is_special_character = false;
+        is_special_character |= ch == '`';
+        if (!current_style.code)
+            is_special_character |= ch == '*' || ch == '_';
+        if (!is_special_character)
+            continue;
+
+        if (current_span_start != offset) {
+            Span span {
+                str.substring_view(current_span_start, offset - current_span_start),
+                current_style
+            };
+            m_spans.append(move(span));
+        }
+
+        if (ch == '`') {
+            current_style.code = !current_style.code;
+        } else {
+            if (offset + 1 < str.length() && str[offset + 1] == ch) {
+                offset++;
+                current_style.strong = !current_style.strong;
+            } else {
+                current_style.emph = !current_style.emph;
+            }
+        }
+
+        current_span_start = offset + 1;
+    }
+
+    if (current_span_start < str.length()) {
+        Span span {
+            str.substring_view(current_span_start, str.length() - current_span_start),
+            current_style
+        };
+        m_spans.append(move(span));
+    }
+
+    return true;
+}