1 files changed, 77 insertions, 0 deletions
diff --git a/src/convert/markdown.rs b/src/convert/markdown.rs
new file mode 100644
index 0000000..3401940
--- /dev/null
+++ b/src/convert/markdown.rs
@@ -0,0 +1,77 @@
+// This file is part of Germ <https://github.com/gemrest/germ>.
+// Copyright (C) 2022-2022 Fuwn <[email protected]>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, version 3.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// Copyright (C) 2022-2022 Fuwn <[email protected]>
+// SPDX-License-Identifier: GPL-3.0-only
+
+use crate::ast::Node;
+
+pub fn convert(source: &[Node]) -> String {
+  let mut markdown = String::new();
+
+  // Since we have an AST tree of the Gemtext, it is very easy to convert from
+  // this AST tree to an alternative markup format.
+  for node in source {
+    match node {
+      Node::Text(text) => markdown.push_str(&format!("{text}\n")),
+      Node::Link {
+        to,
+        text,
+      } =>
+        markdown.push_str(&text.clone().map_or_else(
+          || format!("<{to}>\n"),
+          |text| format!("[{text}]({to})\n"),
+        )),
+      Node::Heading {
+        level,
+        text,
+      } => {
+        markdown.push_str(&format!(
+          "{} {}\n",
+          match level {
+            1 => "#",
+            2 => "##",
+            3 => "###",
+            _ => "",
+          },
+          text
+        ));
+      }
+      Node::List(items) =>
+        markdown.push_str(&format!(
+          "{}\n",
+          items
+            .iter()
+            .map(|i| format!("- {i}"))
+            .collect::<Vec<String>>()
+            .join("\n"),
+        )),
+      Node::Blockquote(text) => markdown.push_str(&format!("> {text}\n")),
+      Node::PreformattedText {
+        alt_text,
+        text,
+      } => {
+        markdown.push_str(&format!(
+          "```{}\n{}```\n",
+          alt_text.clone().unwrap_or_default(),
+          text
+        ));
+      }
+      Node::Whitespace => markdown.push('\n'),
+    }
+  }
+
+  markdown
+}