Merge pull request #25 from async-telegram-bot/feature/GetFile

add getFile implementation

src/core/requests/get_file.rs

@@ -1,8 +1,46 @@
-use crate::core::requests::RequestContext;
-//TODO:: need implementation
+use crate::core::requests::{RequestContext, RequestFuture, ResponseResult, Request};
+use crate::core::types::File;
+use crate::core::network;
 
+/// Use this method to get basic info about a file and prepare it for downloading.
+/// For the moment, bots can download files of up to 20MB in size.
+/// On success, a File object is returned.
+/// The file can then be downloaded via the link https://api.telegram.org/file/bot<token>/<file_path>,
+/// where <file_path> is taken from the response.
+/// It is guaranteed that the link will be valid for at least 1 hour.
+/// When the link expires, a new one can be requested by calling getFile again.
 #[derive(Debug, Clone, Serialize)]
 struct GetFile<'a> {
     #[serde(skip_serializing)]
     ctx: RequestContext<'a>,
+    /// File identifier to get info about
+    file_id: String
+}
+
+
+impl<'a> Request<'a> for GetFile<'a> {
+    type ReturnValue = File;
+
+    fn send(self) -> RequestFuture<'a, ResponseResult<Self::ReturnValue>> {
+        Box::pin(async move {
+            network::request_json(
+                &self.ctx.client,
+                &self.ctx.token,
+                "getFile",
+                &self,
+            )
+                .await
+        })
+    }
+}
+
+
+impl<'a> GetFile<'a>{
+    pub fn file_id<T>(mut self, file_id: T) -> Self
+        where
+            T: Into<String>,
+    {
+        self.file_id = message_id.into();
+        self
+    }
 }