Simplify LLM protocol (#15366)

In this pull request, we change the zed.dev protocol so that we pass the
raw JSON for the specified provider directly to our server. This avoids
the need to define a protobuf message that's a superset of all these
formats.

@bennetbo: We also changed the settings for available_models under
zed.dev to be a flat format, because the nesting seemed too confusing.
Can you help us upgrade the local provider configuration to be
consistent with this? We do whatever we need to do when parsing the
settings to make this simple for users, even if it's a bit more complex
on our end. We want to use versioning to avoid breaking existing users,
but need to keep making progress.

```json
"zed.dev": {
  "available_models": [
    {
      "provider": "anthropic",
        "name": "some-newly-released-model-we-havent-added",
        "max_tokens": 200000
      }
  ]
}
```

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/language_model/src/provider/anthropic.rs

@@ -1,4 +1,4 @@
-use anthropic::{stream_completion, Request, RequestMessage};
+use anthropic::stream_completion;
 use anyhow::{anyhow, Result};
 use collections::BTreeMap;
 use editor::{Editor, EditorElement, EditorStyle};
@@ -18,7 +18,7 @@ use util::ResultExt;
 use crate::{
     settings::AllLanguageModelSettings, LanguageModel, LanguageModelId, LanguageModelName,
     LanguageModelProvider, LanguageModelProviderId, LanguageModelProviderName,
-    LanguageModelProviderState, LanguageModelRequest, LanguageModelRequestMessage, Role,
+    LanguageModelProviderState, LanguageModelRequest, Role,
 };
 
 const PROVIDER_ID: &str = "anthropic";
@@ -160,40 +160,6 @@ pub struct AnthropicModel {
     http_client: Arc<dyn HttpClient>,
 }
 
-impl AnthropicModel {
-    fn to_anthropic_request(&self, mut request: LanguageModelRequest) -> Request {
-        preprocess_anthropic_request(&mut request);
-
-        let mut system_message = String::new();
-        if request
-            .messages
-            .first()
-            .map_or(false, |message| message.role == Role::System)
-        {
-            system_message = request.messages.remove(0).content;
-        }
-
-        Request {
-            model: self.model.id().to_string(),
-            messages: request
-                .messages
-                .iter()
-                .map(|msg| RequestMessage {
-                    role: match msg.role {
-                        Role::User => anthropic::Role::User,
-                        Role::Assistant => anthropic::Role::Assistant,
-                        Role::System => unreachable!("filtered out by preprocess_request"),
-                    },
-                    content: msg.content.clone(),
-                })
-                .collect(),
-            stream: true,
-            system: system_message,
-            max_tokens: 4092,
-        }
-    }
-}
-
 pub fn count_anthropic_tokens(
     request: LanguageModelRequest,
     cx: &AppContext,
@@ -260,7 +226,7 @@ impl LanguageModel for AnthropicModel {
         request: LanguageModelRequest,
         cx: &AsyncAppContext,
     ) -> BoxFuture<'static, Result<BoxStream<'static, Result<String>>>> {
-        let request = self.to_anthropic_request(request);
+        let request = request.into_anthropic(self.model.id().into());
 
         let http_client = self.http_client.clone();
 
@@ -285,75 +251,12 @@ impl LanguageModel for AnthropicModel {
                 low_speed_timeout,
             );
             let response = request.await?;
-            let stream = response
-                .filter_map(|response| async move {
-                    match response {
-                        Ok(response) => match response {
-                            anthropic::ResponseEvent::ContentBlockStart {
-                                content_block, ..
-                            } => match content_block {
-                                anthropic::ContentBlock::Text { text } => Some(Ok(text)),
-                            },
-                            anthropic::ResponseEvent::ContentBlockDelta { delta, .. } => {
-                                match delta {
-                                    anthropic::TextDelta::TextDelta { text } => Some(Ok(text)),
-                                }
-                            }
-                            _ => None,
-                        },
-                        Err(error) => Some(Err(error)),
-                    }
-                })
-                .boxed();
-            Ok(stream)
+            Ok(anthropic::extract_text_from_events(response).boxed())
         }
         .boxed()
     }
 }
 
-pub fn preprocess_anthropic_request(request: &mut LanguageModelRequest) {
-    let mut new_messages: Vec<LanguageModelRequestMessage> = Vec::new();
-    let mut system_message = String::new();
-
-    for message in request.messages.drain(..) {
-        if message.content.is_empty() {
-            continue;
-        }
-
-        match message.role {
-            Role::User | Role::Assistant => {
-                if let Some(last_message) = new_messages.last_mut() {
-                    if last_message.role == message.role {
-                        last_message.content.push_str("\n\n");
-                        last_message.content.push_str(&message.content);
-                        continue;
-                    }
-                }
-
-                new_messages.push(message);
-            }
-            Role::System => {
-                if !system_message.is_empty() {
-                    system_message.push_str("\n\n");
-                }
-                system_message.push_str(&message.content);
-            }
-        }
-    }
-
-    if !system_message.is_empty() {
-        new_messages.insert(
-            0,
-            LanguageModelRequestMessage {
-                role: Role::System,
-                content: system_message,
-            },
-        );
-    }
-
-    request.messages = new_messages;
-}
-
 struct AuthenticationPrompt {
     api_key: View<Editor>,
     state: gpui::Model<State>,