assistant: Add term slash command (#13162)

This adds a `term` slash command to the assistant which allows to inject
the latest terminal output into the context.

Release Notes:

- N/A

crates/assistant/src/slash_command/term_command.rs

@@ -0,0 +1,105 @@
+use std::sync::atomic::AtomicBool;
+use std::sync::Arc;
+
+use anyhow::Result;
+use assistant_slash_command::{SlashCommand, SlashCommandOutput, SlashCommandOutputSection};
+use gpui::{AppContext, Task, WeakView};
+use language::{CodeLabel, LspAdapterDelegate};
+use terminal_view::{terminal_panel::TerminalPanel, TerminalView};
+use ui::prelude::*;
+use workspace::Workspace;
+
+use super::create_label_for_command;
+
+pub(crate) struct TermSlashCommand;
+
+const LINE_COUNT_ARG: &str = "--line-count";
+
+impl SlashCommand for TermSlashCommand {
+    fn name(&self) -> String {
+        "term".into()
+    }
+
+    fn label(&self, cx: &AppContext) -> CodeLabel {
+        create_label_for_command("term", &[LINE_COUNT_ARG], cx)
+    }
+
+    fn description(&self) -> String {
+        "insert terminal output".into()
+    }
+
+    fn menu_text(&self) -> String {
+        "Insert terminal output".into()
+    }
+
+    fn requires_argument(&self) -> bool {
+        false
+    }
+
+    fn complete_argument(
+        self: Arc<Self>,
+        _query: String,
+        _cancel: Arc<AtomicBool>,
+        _workspace: Option<WeakView<Workspace>>,
+        _cx: &mut AppContext,
+    ) -> Task<Result<Vec<String>>> {
+        Task::ready(Ok(vec![LINE_COUNT_ARG.to_string()]))
+    }
+
+    fn run(
+        self: Arc<Self>,
+        argument: Option<&str>,
+        workspace: WeakView<Workspace>,
+        _delegate: Arc<dyn LspAdapterDelegate>,
+        cx: &mut WindowContext,
+    ) -> Task<Result<SlashCommandOutput>> {
+        let Some(workspace) = workspace.upgrade() else {
+            return Task::ready(Err(anyhow::anyhow!("workspace was dropped")));
+        };
+        let Some(terminal_panel) = workspace.read(cx).panel::<TerminalPanel>(cx) else {
+            return Task::ready(Err(anyhow::anyhow!("no terminal panel open")));
+        };
+        let Some(active_terminal) = terminal_panel
+            .read(cx)
+            .pane()
+            .read(cx)
+            .active_item()
+            .and_then(|t| t.downcast::<TerminalView>())
+        else {
+            return Task::ready(Err(anyhow::anyhow!("no active terminal")));
+        };
+
+        let line_count = argument.and_then(|a| parse_argument(a)).unwrap_or(20);
+
+        let lines = active_terminal
+            .read(cx)
+            .model()
+            .read(cx)
+            .last_n_non_empty_lines(line_count);
+
+        let mut text = String::new();
+        text.push_str("Terminal output:\n");
+        text.push_str(&lines.join("\n"));
+        let range = 0..text.len();
+
+        Task::ready(Ok(SlashCommandOutput {
+            text,
+            sections: vec![SlashCommandOutputSection {
+                range,
+                icon: IconName::Terminal,
+                label: "Terminal".into(),
+            }],
+            run_commands_in_text: false,
+        }))
+    }
+}
+
+fn parse_argument(argument: &str) -> Option<usize> {
+    let mut args = argument.split(' ');
+    if args.next() == Some(LINE_COUNT_ARG) {
+        if let Some(line_count) = args.next().and_then(|s| s.parse::<usize>().ok()) {
+            return Some(line_count);
+        }
+    }
+    None
+}