From f5b53e074c08a5c6a044c1ef2bae5445ff621028 Mon Sep 17 00:00:00 2001
From: Omnikar <Omnikar5@gmail.com>
Date: Sat, 6 Nov 2021 16:54:26 -0400
Subject: [PATCH] Help command WIP

---
 helix-term/src/commands.rs                   | 46 ++++++++++++++++++++
 helix-term/src/ui/mod.rs                     | 30 +++++++++++++
 runtime/help/copy_selection_on_next_line.txt | 18 ++++++++
 3 files changed, 94 insertions(+)
 create mode 100644 runtime/help/copy_selection_on_next_line.txt

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 80cbd6d29..2891d8172 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -2229,6 +2229,45 @@ mod cmd {
         Ok(())
     }
 
+    fn help(
+        cx: &mut compositor::Context,
+        args: &[&str],
+        _event: PromptEvent,
+    ) -> anyhow::Result<()> {
+        if args.is_empty() {
+            // TODO: Open a list of commands?
+            todo!()
+        }
+
+        let command = {
+            if Command::COMMAND_LIST
+                .iter()
+                .any(|command| command.name() == args[0])
+            {
+                args[0]
+            } else {
+                let _keys = args
+                    .iter()
+                    .map(|key| key.parse::<KeyEvent>())
+                    .collect::<Result<Vec<KeyEvent>, _>>()?;
+                // TODO: Need to access the keymap here to find the corresponding command
+                todo!()
+            }
+        };
+
+        let mut path = helix_core::runtime_dir();
+        path.push("help");
+        path.push(format!("{}.txt", command));
+
+        if !path.is_file() {
+            return Err(anyhow!("No help available for '{}'", args.join(" ")));
+        }
+        let id = cx.editor.open(path, Action::HorizontalSplit)?;
+        cx.editor.document_mut(id).unwrap().set_path(None)?;
+
+        Ok(())
+    }
+
     pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
         TypableCommand {
             name: "quit",
@@ -2489,6 +2528,13 @@ mod cmd {
             fun: tutor,
             completer: None,
         },
+        TypableCommand {
+            name: "help",
+            aliases: &["h"],
+            doc: "Open documentation for a command or keybind.",
+            fun: help,
+            completer: Some(completers::help),
+        },
     ];
 
     pub static COMMANDS: Lazy<HashMap<&'static str, &'static TypableCommand>> = Lazy::new(|| {
diff --git a/helix-term/src/ui/mod.rs b/helix-term/src/ui/mod.rs
index 24eb7acdf..d489abc02 100644
--- a/helix-term/src/ui/mod.rs
+++ b/helix-term/src/ui/mod.rs
@@ -220,6 +220,36 @@ pub mod completers {
         })
     }
 
+    pub fn help(input: &str) -> Vec<Completion> {
+        let path = helix_core::runtime_dir().join("help");
+        let commands: Vec<String> = std::fs::read_dir(path)
+            .map(|entries| {
+                entries
+                    .filter_map(|entry| {
+                        let entry = entry.ok()?;
+                        let path = entry.path();
+                        (path.extension()? == "txt")
+                            .then(|| path.file_stem().unwrap().to_string_lossy().into_owned())
+                    })
+                    .collect()
+            })
+            .unwrap_or_default();
+
+        let matcher = Matcher::default();
+
+        let mut matches: Vec<_> = commands
+            .into_iter()
+            .map(|name| ((0..), Cow::from(name)))
+            .filter_map(|(_range, name)| {
+                matcher.fuzzy_match(&name, input).map(|score| (name, score))
+            })
+            .collect();
+
+        matches.sort_unstable_by_key(|(_file, score)| Reverse(*score));
+
+        matches.into_iter().map(|(name, _)| ((0..), name)).collect()
+    }
+
     #[derive(Copy, Clone, PartialEq, Eq)]
     enum FileMatch {
         /// Entry should be ignored
diff --git a/runtime/help/copy_selection_on_next_line.txt b/runtime/help/copy_selection_on_next_line.txt
new file mode 100644
index 000000000..4a29dae4a
--- /dev/null
+++ b/runtime/help/copy_selection_on_next_line.txt
@@ -0,0 +1,18 @@
+`copy_selection_on_next_line`
+
+Copies the current primary selection to the next line long enough to accomodate it.
+
+--- Examples ---
+
+The selection is copied from line 1 to line 2.
+┌───────────────────────────┐     ┌───────────────────────────┐
+│ This is text [on line 1]. │ --> │ This is text [on line 1]. │
+│ This is text on line 2.   │     │ This is text [on line 2]. │
+└───────────────────────────┘     └───────────────────────────┘
+
+The selection duplication skips line 2 because it is too short.
+┌──────────────────────────────────┐     ┌──────────────────────────────────┐
+│ This is a longer li[ne of t]ext. │     │ This is a longer li[ne of t]ext. │
+│ This is a shorter line.          │ --> │ This is a shorter line.          │
+│ This is another longer line.     │     │ This is another lon[ger lin]e.   │
+└──────────────────────────────────┘     └──────────────────────────────────┘