docs: add a simple chat client for example (#119)

1. optimize the readme in root
2. add example

Signed-off-by: jokemanfire <hu.dingyang@zte.com.cn>

examples/simple-chat-client/src/client.rs

@@ -0,0 +1,68 @@
+use anyhow::Result;
+use async_trait::async_trait;
+use reqwest::Client as HttpClient;
+
+use crate::model::{CompletionRequest, CompletionResponse};
+
+#[async_trait]
+pub trait ChatClient: Send + Sync {
+    async fn complete(&self, request: CompletionRequest) -> Result<CompletionResponse>;
+}
+
+pub struct OpenAIClient {
+    api_key: String,
+    client: HttpClient,
+    base_url: String,
+}
+
+impl OpenAIClient {
+    pub fn new(api_key: String, url: Option<String>) -> Self {
+        let base_url = url.unwrap_or("https://api.openai.com/v1/chat/completions".to_string());
+
+        // create http client without proxy
+        let client = HttpClient::builder()
+            .no_proxy()
+            .build()
+            .unwrap_or_else(|_| HttpClient::new());
+
+        Self {
+            api_key,
+            client,
+            base_url,
+        }
+    }
+
+    pub fn with_base_url(mut self, base_url: impl Into<String>) -> Self {
+        self.base_url = base_url.into();
+        self
+    }
+}
+
+#[async_trait]
+impl ChatClient for OpenAIClient {
+    async fn complete(&self, request: CompletionRequest) -> Result<CompletionResponse> {
+        println!("sending request to {}", self.base_url);
+        println!("using api key: {}", self.api_key);
+        let request_json = serde_json::to_string(&request)?;
+        println!("request content: {}", request_json);
+        // no proxy
+
+        let response = self
+            .client
+            .post(&self.base_url)
+            .header("Authorization", format!("Bearer {}", self.api_key))
+            .header("Content-Type", "application/json")
+            .json(&request)
+            .send()
+            .await?;
+
+        if !response.status().is_success() {
+            let error_text = response.text().await?;
+            println!("API error: {}", error_text);
+            return Err(anyhow::anyhow!("API Error: {}", error_text));
+        }
+
+        let completion: CompletionResponse = response.json().await?;
+        Ok(completion)
+    }
+}