Move command plugin interface to libnixcmd

src/libcmd/markdown.cc

@@ -0,0 +1,50 @@
+#include "markdown.hh"
+#include "util.hh"
+#include "finally.hh"
+
+#include <sys/queue.h>
+extern "C" {
+#include <lowdown.h>
+}
+
+namespace nix {
+
+std::string renderMarkdownToTerminal(std::string_view markdown)
+{
+    struct lowdown_opts opts {
+        .type = LOWDOWN_TERM,
+        .maxdepth = 20,
+        .cols = std::min(getWindowSize().second, (unsigned short) 80),
+        .hmargin = 0,
+        .vmargin = 0,
+        .feat = LOWDOWN_COMMONMARK | LOWDOWN_FENCED | LOWDOWN_DEFLIST | LOWDOWN_TABLES,
+        .oflags = 0,
+    };
+
+    auto doc = lowdown_doc_new(&opts);
+    if (!doc)
+        throw Error("cannot allocate Markdown document");
+    Finally freeDoc([&]() { lowdown_doc_free(doc); });
+
+    size_t maxn = 0;
+    auto node = lowdown_doc_parse(doc, &maxn, markdown.data(), markdown.size());
+    if (!node)
+        throw Error("cannot parse Markdown document");
+    Finally freeNode([&]() { lowdown_node_free(node); });
+
+    auto renderer = lowdown_term_new(&opts);
+    if (!renderer)
+        throw Error("cannot allocate Markdown renderer");
+    Finally freeRenderer([&]() { lowdown_term_free(renderer); });
+
+    auto buf = lowdown_buf_new(16384);
+    if (!buf)
+        throw Error("cannot allocate Markdown output buffer");
+    Finally freeBuffer([&]() { lowdown_buf_free(buf); });
+
+    lowdown_term_rndr(buf, nullptr, renderer, node);
+
+    return std::string(buf->data, buf->size);
+}
+
+}