Supermaven enhanced (#11521)

Fixes #11422 by accepting just the start of the line.

Release Notes:

- N/A

---------

Co-authored-by: max <max@zed.dev>
Co-authored-by: jacob <jacob@supermaven.com>

crates/supermaven/src/supermaven.rs

@@ -10,7 +10,9 @@ use collections::BTreeMap;
 
 use futures::{channel::mpsc, io::BufReader, AsyncBufReadExt, StreamExt};
 use gpui::{AppContext, AsyncAppContext, EntityId, Global, Model, ModelContext, Task, WeakModel};
-use language::{language_settings::all_language_settings, Anchor, Buffer, ToOffset};
+use language::{
+    language_settings::all_language_settings, Anchor, Buffer, BufferSnapshot, ToOffset,
+};
 use messages::*;
 use postage::watch;
 use serde::{Deserialize, Serialize};
@@ -19,7 +21,7 @@ use smol::{
     io::AsyncWriteExt,
     process::{Child, ChildStdin, ChildStdout, Command},
 };
-use std::{ops::Range, path::PathBuf, process::Stdio, sync::Arc};
+use std::{path::PathBuf, process::Stdio, sync::Arc};
 use ui::prelude::*;
 use util::ResultExt;
 
@@ -128,9 +130,9 @@ impl Supermaven {
                 state_id,
                 SupermavenCompletionState {
                     buffer_id,
-                    range: cursor_position.bias_left(buffer)..cursor_position.bias_right(buffer),
-                    completion: Vec::new(),
+                    prefix_anchor: cursor_position,
                     text: String::new(),
+                    dedent: String::new(),
                     updates_tx,
                 },
             );
@@ -158,16 +160,64 @@ impl Supermaven {
 
     pub fn completion(
         &self,
-        id: SupermavenCompletionStateId,
-    ) -> Option<&SupermavenCompletionState> {
+        buffer: &Model<Buffer>,
+        cursor_position: Anchor,
+        cx: &AppContext,
+    ) -> Option<&str> {
         if let Self::Spawned(agent) = self {
-            agent.states.get(&id)
+            find_relevant_completion(
+                &agent.states,
+                buffer.entity_id(),
+                &buffer.read(cx).snapshot(),
+                cursor_position,
+            )
         } else {
             None
         }
     }
 }
 
+fn find_relevant_completion<'a>(
+    states: &'a BTreeMap<SupermavenCompletionStateId, SupermavenCompletionState>,
+    buffer_id: EntityId,
+    buffer: &BufferSnapshot,
+    cursor_position: Anchor,
+) -> Option<&'a str> {
+    let mut best_completion: Option<&str> = None;
+    'completions: for state in states.values() {
+        if state.buffer_id != buffer_id {
+            continue;
+        }
+        let Some(state_completion) = state.text.strip_prefix(&state.dedent) else {
+            continue;
+        };
+
+        let current_cursor_offset = cursor_position.to_offset(buffer);
+        let original_cursor_offset = state.prefix_anchor.to_offset(buffer);
+        if current_cursor_offset < original_cursor_offset {
+            continue;
+        }
+
+        let text_inserted_since_completion_request =
+            buffer.text_for_range(original_cursor_offset..current_cursor_offset);
+        let mut trimmed_completion = state_completion;
+        for chunk in text_inserted_since_completion_request {
+            if let Some(suffix) = trimmed_completion.strip_prefix(chunk) {
+                trimmed_completion = suffix;
+            } else {
+                continue 'completions;
+            }
+        }
+
+        if best_completion.map_or(false, |best| best.len() > trimmed_completion.len()) {
+            continue;
+        }
+
+        best_completion = Some(trimmed_completion);
+    }
+    best_completion
+}
+
 pub struct SupermavenAgent {
     _process: Child,
     next_state_id: SupermavenCompletionStateId,
@@ -311,11 +361,12 @@ impl SupermavenAgent {
                 let state_id = SupermavenCompletionStateId(response.state_id.parse().unwrap());
                 if let Some(state) = self.states.get_mut(&state_id) {
                     for item in &response.items {
-                        if let ResponseItem::Text { text } = item {
-                            state.text.push_str(text);
+                        match item {
+                            ResponseItem::Text { text } => state.text.push_str(text),
+                            ResponseItem::Dedent { text } => state.dedent.push_str(text),
+                            _ => {}
                         }
                     }
-                    state.completion.extend(response.items);
                     *state.updates_tx.borrow_mut() = ();
                 }
             }
@@ -333,9 +384,9 @@ pub struct SupermavenCompletionStateId(usize);
 #[allow(dead_code)]
 pub struct SupermavenCompletionState {
     buffer_id: EntityId,
-    range: Range<Anchor>,
-    completion: Vec<ResponseItem>,
+    prefix_anchor: Anchor,
     text: String,
+    dedent: String,
     updates_tx: watch::Sender<()>,
 }