manager: Simplify very complex mermaid graphs

Forgejo has a limit of 5000 characters per mermaid graph.  We started
hitting this for some issues.  Regenerate a somewhat simplified version
of the subtree in this case which hopefully does not hit the same limit
again.

techtree-manager/src/issue.rs

@@ -111,17 +111,33 @@ pub async fn update_bot_comment_from_subtree(
     subtree: &crate::tree::Subtree<'_>,
     hash: &str,
 ) -> anyhow::Result<()> {
-    let mermaid = subtree.to_mermaid(&ctx.repo_url.to_string());
+    let mut mermaid = subtree.to_mermaid(&ctx.repo_url.to_string(), false);
 
-    let full_text = format!(
-        r##"## Partial Techtree
+    // When the mermaid graph gets too big, regenerate a simplified version.
+    if mermaid.len() > 4990 {
+        log::info!("Mermaid graph is too big, generating simplified version...");
+        mermaid = subtree.to_mermaid(&ctx.repo_url.to_string(), true);
+    }
+
+    let full_text = if mermaid.len() > 4990 {
+        format!(
+            r##"## Partial Techtree
+_Sorry, the partial techtree is still too big to be displayed for this element..._
+
+<small>Digest: {hash}; Last Updated: {timestamp}</small>"##,
+            timestamp = ctx.timestamp,
+        )
+    } else {
+        format!(
+            r##"## Partial Techtree
 ```mermaid
 {mermaid}
 ```
 
 <small>Digest: {hash}; Last Updated: {timestamp}</small>"##,
-        timestamp = ctx.timestamp,
-    );
+            timestamp = ctx.timestamp,
+        )
+    };
 
     update_bot_comment(&ctx, id, full_text).await?;
 

techtree-manager/src/tree.rs

@@ -51,6 +51,7 @@ impl Element {
         index: ElementIndex,
         role: Option<SubtreeElementRole>,
         repo_url: &str,
+        simple: bool,
     ) -> String {
         let Element {
             issue_number,
@@ -59,9 +60,13 @@ impl Element {
             status,
         } = self;
 
-        let label = format!(
-            r##"<a href='{repo_url}/issues/{issue_number}' target='_blank'>#{issue_number}</a> | {status}\n<i>{ty}</i>\n<b>{description}</b>"##
-        );
+        let label = if simple {
+            format!(r##"#{issue_number} | {status}\n<i>{ty}</i>\n<b>{description}</b>"##)
+        } else {
+            format!(
+                r##"<a href='{repo_url}/issues/{issue_number}' target='_blank'>#{issue_number}</a> | {status}\n<i>{ty}</i>\n<b>{description}</b>"##
+            )
+        };
 
         let class = match (role, status) {
             (Some(SubtreeElementRole::ElementOfInterest), _) => "eoi",
@@ -176,13 +181,13 @@ impl Tree {
         )
     }
 
-    pub fn to_mermaid(&self, repo_url: &str) -> String {
+    pub fn to_mermaid(&self, repo_url: &str, simple: bool) -> String {
         let mut mermaid = String::new();
         mermaid.push_str("flowchart BT\n");
         mermaid.push_str(&mermaid_classes());
 
         for index in self.graph.node_indices() {
-            mermaid.push_str(&self.graph[index].to_mermaid_node(index, None, repo_url));
+            mermaid.push_str(&self.graph[index].to_mermaid_node(index, None, repo_url, simple));
             mermaid.push_str("\n");
         }
 
@@ -300,18 +305,19 @@ impl<'a> Subtree<'a> {
         format!("{:?}", dot)
     }
 
-    pub fn to_mermaid(&self, repo_url: &str) -> String {
+    pub fn to_mermaid(&self, repo_url: &str, simple: bool) -> String {
         let mut mermaid = String::new();
         mermaid.push_str("flowchart BT\n");
         mermaid.push_str(&mermaid_classes());
 
         for index in self.graph.node_indices() {
             let node = &self.graph[index];
-            mermaid.push_str(
-                &node
-                    .element
-                    .to_mermaid_node(index, Some(node.role), repo_url),
-            );
+            mermaid.push_str(&node.element.to_mermaid_node(
+                index,
+                Some(node.role),
+                repo_url,
+                simple,
+            ));
             mermaid.push_str("\n");
         }
 

techtree-manager/src/wiki.rs

@@ -5,7 +5,7 @@ pub async fn update_wiki_from_tree(
     ctx: &crate::Context,
     tree: &crate::tree::Tree,
 ) -> anyhow::Result<()> {
-    let mermaid = tree.to_mermaid(&ctx.repo_url.to_string());
+    let mermaid = tree.to_mermaid(&ctx.repo_url.to_string(), false);
     let wiki_text = format!(
         r##"This page is automatically updated to show the latest and greatest FAFO techtree: