Extract slash commands to their own crate (#23261)

This PR extracts the slash command definitions out of the `assistant`
crate and into their own `assistant_slash_commands` crate.

Release Notes:

- N/A

crates/assistant_slash_commands/src/selection_command.rs

@@ -0,0 +1,194 @@
+use anyhow::{anyhow, Result};
+use assistant_slash_command::{
+    ArgumentCompletion, SlashCommand, SlashCommandContent, SlashCommandEvent,
+    SlashCommandOutputSection, SlashCommandResult,
+};
+use editor::Editor;
+use futures::StreamExt;
+use gpui::{AppContext, Task, WeakView};
+use gpui::{SharedString, ViewContext, WindowContext};
+use language::{BufferSnapshot, CodeLabel, LspAdapterDelegate};
+use std::sync::atomic::AtomicBool;
+use std::sync::Arc;
+use ui::IconName;
+use workspace::Workspace;
+
+use crate::file_command::codeblock_fence_for_path;
+
+pub struct SelectionCommand;
+
+impl SlashCommand for SelectionCommand {
+    fn name(&self) -> String {
+        "selection".into()
+    }
+
+    fn label(&self, _cx: &AppContext) -> CodeLabel {
+        CodeLabel::plain(self.name(), None)
+    }
+
+    fn description(&self) -> String {
+        "Insert editor selection".into()
+    }
+
+    fn icon(&self) -> IconName {
+        IconName::Quote
+    }
+
+    fn menu_text(&self) -> String {
+        self.description()
+    }
+
+    fn requires_argument(&self) -> bool {
+        false
+    }
+
+    fn accepts_arguments(&self) -> bool {
+        true
+    }
+
+    fn complete_argument(
+        self: Arc<Self>,
+        _arguments: &[String],
+        _cancel: Arc<AtomicBool>,
+        _workspace: Option<WeakView<Workspace>>,
+        _cx: &mut WindowContext,
+    ) -> Task<Result<Vec<ArgumentCompletion>>> {
+        Task::ready(Err(anyhow!("this command does not require argument")))
+    }
+
+    fn run(
+        self: Arc<Self>,
+        _arguments: &[String],
+        _context_slash_command_output_sections: &[SlashCommandOutputSection<language::Anchor>],
+        _context_buffer: BufferSnapshot,
+        workspace: WeakView<Workspace>,
+        _delegate: Option<Arc<dyn LspAdapterDelegate>>,
+        cx: &mut WindowContext,
+    ) -> Task<SlashCommandResult> {
+        let mut events = vec![];
+
+        let Some(creases) = workspace
+            .update(cx, selections_creases)
+            .unwrap_or_else(|e| {
+                events.push(Err(e));
+                None
+            })
+        else {
+            return Task::ready(Err(anyhow!("no active selection")));
+        };
+
+        for (text, title) in creases {
+            events.push(Ok(SlashCommandEvent::StartSection {
+                icon: IconName::TextSnippet,
+                label: SharedString::from(title),
+                metadata: None,
+            }));
+            events.push(Ok(SlashCommandEvent::Content(SlashCommandContent::Text {
+                text,
+                run_commands_in_text: false,
+            })));
+            events.push(Ok(SlashCommandEvent::EndSection));
+            events.push(Ok(SlashCommandEvent::Content(SlashCommandContent::Text {
+                text: "\n".to_string(),
+                run_commands_in_text: false,
+            })));
+        }
+
+        let result = futures::stream::iter(events).boxed();
+
+        Task::ready(Ok(result))
+    }
+}
+
+pub fn selections_creases(
+    workspace: &mut workspace::Workspace,
+    cx: &mut ViewContext<Workspace>,
+) -> Option<Vec<(String, String)>> {
+    let editor = workspace
+        .active_item(cx)
+        .and_then(|item| item.act_as::<Editor>(cx))?;
+
+    let mut creases = vec![];
+    editor.update(cx, |editor, cx| {
+        let selections = editor.selections.all_adjusted(cx);
+        let buffer = editor.buffer().read(cx).snapshot(cx);
+        for selection in selections {
+            let range = editor::ToOffset::to_offset(&selection.start, &buffer)
+                ..editor::ToOffset::to_offset(&selection.end, &buffer);
+            let selected_text = buffer.text_for_range(range.clone()).collect::<String>();
+            if selected_text.is_empty() {
+                continue;
+            }
+            let start_language = buffer.language_at(range.start);
+            let end_language = buffer.language_at(range.end);
+            let language_name = if start_language == end_language {
+                start_language.map(|language| language.code_fence_block_name())
+            } else {
+                None
+            };
+            let language_name = language_name.as_deref().unwrap_or("");
+            let filename = buffer
+                .file_at(selection.start)
+                .map(|file| file.full_path(cx));
+            let text = if language_name == "markdown" {
+                selected_text
+                    .lines()
+                    .map(|line| format!("> {}", line))
+                    .collect::<Vec<_>>()
+                    .join("\n")
+            } else {
+                let start_symbols = buffer
+                    .symbols_containing(selection.start, None)
+                    .map(|(_, symbols)| symbols);
+                let end_symbols = buffer
+                    .symbols_containing(selection.end, None)
+                    .map(|(_, symbols)| symbols);
+
+                let outline_text =
+                    if let Some((start_symbols, end_symbols)) = start_symbols.zip(end_symbols) {
+                        Some(
+                            start_symbols
+                                .into_iter()
+                                .zip(end_symbols)
+                                .take_while(|(a, b)| a == b)
+                                .map(|(a, _)| a.text)
+                                .collect::<Vec<_>>()
+                                .join(" > "),
+                        )
+                    } else {
+                        None
+                    };
+
+                let line_comment_prefix = start_language
+                    .and_then(|l| l.default_scope().line_comment_prefixes().first().cloned());
+
+                let fence = codeblock_fence_for_path(
+                    filename.as_deref(),
+                    Some(selection.start.row..=selection.end.row),
+                );
+
+                if let Some((line_comment_prefix, outline_text)) =
+                    line_comment_prefix.zip(outline_text)
+                {
+                    let breadcrumb = format!("{line_comment_prefix}Excerpt from: {outline_text}\n");
+                    format!("{fence}{breadcrumb}{selected_text}\n```")
+                } else {
+                    format!("{fence}{selected_text}\n```")
+                }
+            };
+            let crease_title = if let Some(path) = filename {
+                let start_line = selection.start.row + 1;
+                let end_line = selection.end.row + 1;
+                if start_line == end_line {
+                    format!("{}, Line {}", path.display(), start_line)
+                } else {
+                    format!("{}, Lines {} to {}", path.display(), start_line, end_line)
+                }
+            } else {
+                "Quoted selection".to_string()
+            };
+            creases.push((text, crease_title));
+        }
+    });
+    Some(creases)
+}