feat: add FastEmbed text embedding support (#108)

* feat: add FastEmbed text embedding support

This commit includes changes made to add support for FastEmbed text embedding. We've added a new dependency 'fastembed' in our Cargo.toml. New error message has been added in 'error.rs' to handle any FastEmbed related errors. Created a new struct 'FastEmbed' under 'fastembed.rs' that utilizes the FastEmbed library for text embedding. Also, added FastEmbed related modules and updated embedding/mod.rs accordingly. Tests for FastEmbed have been included as well.

* chore: add example

Cargo.toml

@@ -41,6 +41,7 @@ tokio-stream = "0.1.15"
 secrecy = "0.8.0"
 readability = "0.3.0"
 url = "2.5.0"
+fastembed = "3.3.0"
 
 [features]
 default = []

examples/fastembed.rs

@@ -0,0 +1,31 @@
+use langchain_rust::embedding::{Embedder, EmbeddingModel, FastEmbed, InitOptions, TextEmbedding};
+
+#[tokio::main]
+async fn main() {
+    //Default
+    let fastembed = FastEmbed::try_new().unwrap();
+    let embeddings = fastembed
+        .embed_documents(&["hello world".to_string(), "foo bar".to_string()])
+        .await
+        .unwrap();
+
+    println!("Len: {:?}", embeddings.len());
+
+    //With custom model
+
+    let model = TextEmbedding::try_new(InitOptions {
+        model_name: EmbeddingModel::AllMiniLML6V2,
+        show_download_progress: true,
+        ..Default::default()
+    })
+    .unwrap();
+
+    let fastembed = FastEmbed::from(model);
+
+    fastembed
+        .embed_documents(&["hello world".to_string(), "foo bar".to_string()])
+        .await
+        .unwrap();
+
+    println!("Len: {:?}", embeddings.len());
+}

src/embedding/error.rs

@@ -18,4 +18,7 @@ pub enum EmbedderError {
         status_code: StatusCode,
         error_message: String,
     },
+
+    #[error("FastEmbed error: {0}")]
+    FastEmbedError(String),
 }

src/embedding/fastembed/fastembed.rs

@@ -0,0 +1,76 @@
+use async_trait::async_trait;
+pub use fastembed::{EmbeddingModel, InitOptions, TextEmbedding};
+
+use crate::embedding::{Embedder, EmbedderError};
+
+pub struct FastEmbed {
+    model: TextEmbedding,
+    batch_size: Option<usize>,
+}
+
+impl FastEmbed {
+    pub fn try_new() -> Result<Self, EmbedderError> {
+        Ok(Self {
+            model: TextEmbedding::try_new(Default::default())
+                .map_err(|e| EmbedderError::FastEmbedError(e.to_string()))?,
+            batch_size: None,
+        })
+    }
+
+    pub fn with_batch_size(mut self, batch_size: usize) -> Self {
+        self.batch_size = Some(batch_size);
+        self
+    }
+}
+
+impl From<TextEmbedding> for FastEmbed {
+    fn from(model: TextEmbedding) -> Self {
+        Self {
+            model,
+            batch_size: None,
+        }
+    }
+}
+
+#[async_trait]
+impl Embedder for FastEmbed {
+    async fn embed_documents(&self, documents: &[String]) -> Result<Vec<Vec<f64>>, EmbedderError> {
+        let embeddings = self
+            .model
+            .embed(documents.to_vec(), self.batch_size)
+            .map_err(|e| EmbedderError::FastEmbedError(e.to_string()))?;
+
+        Ok(embeddings
+            .into_iter()
+            .map(|inner_vec| {
+                inner_vec
+                    .into_iter()
+                    .map(|x| x as f64)
+                    .collect::<Vec<f64>>()
+            })
+            .collect::<Vec<Vec<f64>>>())
+    }
+
+    async fn embed_query(&self, text: &str) -> Result<Vec<f64>, EmbedderError> {
+        let embedding = self
+            .model
+            .embed(vec![text], self.batch_size)
+            .map_err(|e| EmbedderError::FastEmbedError(e.to_string()))?;
+
+        Ok(embedding[0].iter().map(|x| *x as f64).collect())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[tokio::test]
+    async fn test_fastembed() {
+        let fastembed = FastEmbed::try_new().unwrap();
+        let embeddings = fastembed
+            .embed_documents(&["hello world".to_string(), "foo bar".to_string()])
+            .await
+            .unwrap();
+        assert_eq!(embeddings.len(), 2);
+    }
+}

src/embedding/fastembed/mod.rs

@@ -0,0 +1,2 @@
+mod fastembed;
+pub use fastembed::*;

src/embedding/mod.rs

@@ -4,3 +4,6 @@ mod error;
 pub mod ollama;
 pub mod openai;
 pub use error::*;
+
+mod fastembed;
+pub use fastembed::*;