Add support for Vercel as a language model provider (#33292)

Vercel v0 is an OpenAI-compatible model, so this is mostly a dupe of the
OpenAI provider files with some adaptations for v0, including going
ahead and using the custom endpoint for the API URL field.

Release Notes:

- Added support for Vercel as a language model provider.

crates/vercel/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "vercel"
+version = "0.1.0"
+edition.workspace = true
+publish.workspace = true
+license = "GPL-3.0-or-later"
+
+[lints]
+workspace = true
+
+[lib]
+path = "src/vercel.rs"
+
+[features]
+default = []
+schemars = ["dep:schemars"]
+
+[dependencies]
+anyhow.workspace = true
+futures.workspace = true
+http_client.workspace = true
+schemars = { workspace = true, optional = true }
+serde.workspace = true
+serde_json.workspace = true
+strum.workspace = true
+workspace-hack.workspace = true

crates/vercel/LICENSE-GPL

@@ -0,0 +1 @@
+../../LICENSE-GPL

crates/vercel/src/vercel.rs

@@ -0,0 +1,438 @@
+use anyhow::{Context as _, Result, anyhow};
+use futures::{AsyncBufReadExt, AsyncReadExt, StreamExt, io::BufReader, stream::BoxStream};
+use http_client::{AsyncBody, HttpClient, Method, Request as HttpRequest};
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use std::{convert::TryFrom, future::Future};
+use strum::EnumIter;
+
+pub const VERCEL_API_URL: &str = "https://api.v0.dev/v1";
+
+fn is_none_or_empty<T: AsRef<[U]>, U>(opt: &Option<T>) -> bool {
+    opt.as_ref().map_or(true, |v| v.as_ref().is_empty())
+}
+
+#[derive(Clone, Copy, Serialize, Deserialize, Debug, Eq, PartialEq)]
+#[serde(rename_all = "lowercase")]
+pub enum Role {
+    User,
+    Assistant,
+    System,
+    Tool,
+}
+
+impl TryFrom<String> for Role {
+    type Error = anyhow::Error;
+
+    fn try_from(value: String) -> Result<Self> {
+        match value.as_str() {
+            "user" => Ok(Self::User),
+            "assistant" => Ok(Self::Assistant),
+            "system" => Ok(Self::System),
+            "tool" => Ok(Self::Tool),
+            _ => anyhow::bail!("invalid role '{value}'"),
+        }
+    }
+}
+
+impl From<Role> for String {
+    fn from(val: Role) -> Self {
+        match val {
+            Role::User => "user".to_owned(),
+            Role::Assistant => "assistant".to_owned(),
+            Role::System => "system".to_owned(),
+            Role::Tool => "tool".to_owned(),
+        }
+    }
+}
+
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+#[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, EnumIter)]
+pub enum Model {
+    #[serde(rename = "v-0")]
+    #[default]
+    VZero,
+
+    #[serde(rename = "custom")]
+    Custom {
+        name: String,
+        /// The name displayed in the UI, such as in the assistant panel model dropdown menu.
+        display_name: Option<String>,
+        max_tokens: u64,
+        max_output_tokens: Option<u64>,
+        max_completion_tokens: Option<u64>,
+    },
+}
+
+impl Model {
+    pub fn default_fast() -> Self {
+        Self::VZero
+    }
+
+    pub fn from_id(id: &str) -> Result<Self> {
+        match id {
+            "v-0" => Ok(Self::VZero),
+            invalid_id => anyhow::bail!("invalid model id '{invalid_id}'"),
+        }
+    }
+
+    pub fn id(&self) -> &str {
+        match self {
+            Self::VZero => "v-0",
+            Self::Custom { name, .. } => name,
+        }
+    }
+
+    pub fn display_name(&self) -> &str {
+        match self {
+            Self::VZero => "Vercel v0",
+            Self::Custom {
+                name, display_name, ..
+            } => display_name.as_ref().unwrap_or(name),
+        }
+    }
+
+    pub fn max_token_count(&self) -> u64 {
+        match self {
+            Self::VZero => 128_000,
+            Self::Custom { max_tokens, .. } => *max_tokens,
+        }
+    }
+
+    pub fn max_output_tokens(&self) -> Option<u64> {
+        match self {
+            Self::Custom {
+                max_output_tokens, ..
+            } => *max_output_tokens,
+            Self::VZero => Some(32_768),
+        }
+    }
+
+    /// Returns whether the given model supports the `parallel_tool_calls` parameter.
+    ///
+    /// If the model does not support the parameter, do not pass it up, or the API will return an error.
+    pub fn supports_parallel_tool_calls(&self) -> bool {
+        match self {
+            Self::VZero => true,
+            Model::Custom { .. } => false,
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Request {
+    pub model: String,
+    pub messages: Vec<RequestMessage>,
+    pub stream: bool,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub max_completion_tokens: Option<u64>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub stop: Vec<String>,
+    pub temperature: f32,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub tool_choice: Option<ToolChoice>,
+    /// Whether to enable parallel function calling during tool use.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub parallel_tool_calls: Option<bool>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub tools: Vec<ToolDefinition>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum ToolChoice {
+    Auto,
+    Required,
+    None,
+    Other(ToolDefinition),
+}
+
+#[derive(Clone, Deserialize, Serialize, Debug)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum ToolDefinition {
+    #[allow(dead_code)]
+    Function { function: FunctionDefinition },
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct FunctionDefinition {
+    pub name: String,
+    pub description: Option<String>,
+    pub parameters: Option<Value>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+#[serde(tag = "role", rename_all = "lowercase")]
+pub enum RequestMessage {
+    Assistant {
+        content: Option<MessageContent>,
+        #[serde(default, skip_serializing_if = "Vec::is_empty")]
+        tool_calls: Vec<ToolCall>,
+    },
+    User {
+        content: MessageContent,
+    },
+    System {
+        content: MessageContent,
+    },
+    Tool {
+        content: MessageContent,
+        tool_call_id: String,
+    },
+}
+
+#[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)]
+#[serde(untagged)]
+pub enum MessageContent {
+    Plain(String),
+    Multipart(Vec<MessagePart>),
+}
+
+impl MessageContent {
+    pub fn empty() -> Self {
+        MessageContent::Multipart(vec![])
+    }
+
+    pub fn push_part(&mut self, part: MessagePart) {
+        match self {
+            MessageContent::Plain(text) => {
+                *self =
+                    MessageContent::Multipart(vec![MessagePart::Text { text: text.clone() }, part]);
+            }
+            MessageContent::Multipart(parts) if parts.is_empty() => match part {
+                MessagePart::Text { text } => *self = MessageContent::Plain(text),
+                MessagePart::Image { .. } => *self = MessageContent::Multipart(vec![part]),
+            },
+            MessageContent::Multipart(parts) => parts.push(part),
+        }
+    }
+}
+
+impl From<Vec<MessagePart>> for MessageContent {
+    fn from(mut parts: Vec<MessagePart>) -> Self {
+        if let [MessagePart::Text { text }] = parts.as_mut_slice() {
+            MessageContent::Plain(std::mem::take(text))
+        } else {
+            MessageContent::Multipart(parts)
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)]
+#[serde(tag = "type")]
+pub enum MessagePart {
+    #[serde(rename = "text")]
+    Text { text: String },
+    #[serde(rename = "image_url")]
+    Image { image_url: ImageUrl },
+}
+
+#[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)]
+pub struct ImageUrl {
+    pub url: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub detail: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+pub struct ToolCall {
+    pub id: String,
+    #[serde(flatten)]
+    pub content: ToolCallContent,
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+#[serde(tag = "type", rename_all = "lowercase")]
+pub enum ToolCallContent {
+    Function { function: FunctionContent },
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+pub struct FunctionContent {
+    pub name: String,
+    pub arguments: String,
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+pub struct ResponseMessageDelta {
+    pub role: Option<Role>,
+    pub content: Option<String>,
+    #[serde(default, skip_serializing_if = "is_none_or_empty")]
+    pub tool_calls: Option<Vec<ToolCallChunk>>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+pub struct ToolCallChunk {
+    pub index: usize,
+    pub id: Option<String>,
+
+    // There is also an optional `type` field that would determine if a
+    // function is there. Sometimes this streams in with the `function` before
+    // it streams in the `type`
+    pub function: Option<FunctionChunk>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
+pub struct FunctionChunk {
+    pub name: Option<String>,
+    pub arguments: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct Usage {
+    pub prompt_tokens: u32,
+    pub completion_tokens: u32,
+    pub total_tokens: u32,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct ChoiceDelta {
+    pub index: u32,
+    pub delta: ResponseMessageDelta,
+    pub finish_reason: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(untagged)]
+pub enum ResponseStreamResult {
+    Ok(ResponseStreamEvent),
+    Err { error: String },
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct ResponseStreamEvent {
+    pub model: String,
+    pub choices: Vec<ChoiceDelta>,
+    pub usage: Option<Usage>,
+}
+
+pub async fn stream_completion(
+    client: &dyn HttpClient,
+    api_url: &str,
+    api_key: &str,
+    request: Request,
+) -> Result<BoxStream<'static, Result<ResponseStreamEvent>>> {
+    let uri = format!("{api_url}/chat/completions");
+    let request_builder = HttpRequest::builder()
+        .method(Method::POST)
+        .uri(uri)
+        .header("Content-Type", "application/json")
+        .header("Authorization", format!("Bearer {}", api_key));
+
+    let request = request_builder.body(AsyncBody::from(serde_json::to_string(&request)?))?;
+    let mut response = client.send(request).await?;
+    if response.status().is_success() {
+        let reader = BufReader::new(response.into_body());
+        Ok(reader
+            .lines()
+            .filter_map(|line| async move {
+                match line {
+                    Ok(line) => {
+                        let line = line.strip_prefix("data: ")?;
+                        if line == "[DONE]" {
+                            None
+                        } else {
+                            match serde_json::from_str(line) {
+                                Ok(ResponseStreamResult::Ok(response)) => Some(Ok(response)),
+                                Ok(ResponseStreamResult::Err { error }) => {
+                                    Some(Err(anyhow!(error)))
+                                }
+                                Err(error) => Some(Err(anyhow!(error))),
+                            }
+                        }
+                    }
+                    Err(error) => Some(Err(anyhow!(error))),
+                }
+            })
+            .boxed())
+    } else {
+        let mut body = String::new();
+        response.body_mut().read_to_string(&mut body).await?;
+
+        #[derive(Deserialize)]
+        struct VercelResponse {
+            error: VercelError,
+        }
+
+        #[derive(Deserialize)]
+        struct VercelError {
+            message: String,
+        }
+
+        match serde_json::from_str::<VercelResponse>(&body) {
+            Ok(response) if !response.error.message.is_empty() => Err(anyhow!(
+                "Failed to connect to Vercel API: {}",
+                response.error.message,
+            )),
+
+            _ => anyhow::bail!(
+                "Failed to connect to Vercel API: {} {}",
+                response.status(),
+                body,
+            ),
+        }
+    }
+}
+
+#[derive(Copy, Clone, Serialize, Deserialize)]
+pub enum VercelEmbeddingModel {
+    #[serde(rename = "text-embedding-3-small")]
+    TextEmbedding3Small,
+    #[serde(rename = "text-embedding-3-large")]
+    TextEmbedding3Large,
+}
+
+#[derive(Serialize)]
+struct VercelEmbeddingRequest<'a> {
+    model: VercelEmbeddingModel,
+    input: Vec<&'a str>,
+}
+
+#[derive(Deserialize)]
+pub struct VercelEmbeddingResponse {
+    pub data: Vec<VercelEmbedding>,
+}
+
+#[derive(Deserialize)]
+pub struct VercelEmbedding {
+    pub embedding: Vec<f32>,
+}
+
+pub fn embed<'a>(
+    client: &dyn HttpClient,
+    api_url: &str,
+    api_key: &str,
+    model: VercelEmbeddingModel,
+    texts: impl IntoIterator<Item = &'a str>,
+) -> impl 'static + Future<Output = Result<VercelEmbeddingResponse>> {
+    let uri = format!("{api_url}/embeddings");
+
+    let request = VercelEmbeddingRequest {
+        model,
+        input: texts.into_iter().collect(),
+    };
+    let body = AsyncBody::from(serde_json::to_string(&request).unwrap());
+    let request = HttpRequest::builder()
+        .method(Method::POST)
+        .uri(uri)
+        .header("Content-Type", "application/json")
+        .header("Authorization", format!("Bearer {}", api_key))
+        .body(body)
+        .map(|request| client.send(request));
+
+    async move {
+        let mut response = request?.await?;
+        let mut body = String::new();
+        response.body_mut().read_to_string(&mut body).await?;
+
+        anyhow::ensure!(
+            response.status().is_success(),
+            "error during embedding, status: {:?}, body: {:?}",
+            response.status(),
+            body
+        );
+        let response: VercelEmbeddingResponse =
+            serde_json::from_str(&body).context("failed to parse Vercel embedding response")?;
+        Ok(response)
+    }
+}