ch-remote, api_client: Split HTTP/API client code into new crate

Split out the HTTP request handling code from ch-remote into a new
crate which can be used in other places where talking to the API server
by HTTP is necessary.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

api_client/Cargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "api_client"
+version = "0.1.0"
+authors = ["The Cloud Hypervisor Authors"]
+edition = "2018"

api_client/src/lib.rs

@@ -0,0 +1,175 @@
+// Copyright © 2020 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use std::fmt;
+use std::io::{Read, Write};
+
+#[derive(Debug)]
+pub enum Error {
+    Socket(std::io::Error),
+    StatusCodeParsing(std::num::ParseIntError),
+    MissingProtocol,
+    ContentLengthParsing(std::num::ParseIntError),
+    ServerResponse(StatusCode, Option<String>),
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use Error::*;
+        match self {
+            Socket(e) => write!(f, "Error writing to or reading from HTTP socket: {}", e),
+            StatusCodeParsing(e) => write!(f, "Error parsing HTTP status code: {}", e),
+            MissingProtocol => write!(f, "HTTP output is missing protocol statement"),
+            ContentLengthParsing(e) => write!(f, "Error parsing HTTP Content-Length field: {}", e),
+            ServerResponse(s, o) => {
+                if let Some(o) = o {
+                    write!(f, "Server responded with an error: {:?}: {}", s, o)
+                } else {
+                    write!(f, "Server responded with an error: {:?}", s)
+                }
+            }
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum StatusCode {
+    Continue,
+    OK,
+    NoContent,
+    BadRequest,
+    NotFound,
+    InternalServerError,
+    NotImplemented,
+    Unknown,
+}
+
+impl StatusCode {
+    fn from_raw(code: usize) -> StatusCode {
+        match code {
+            100 => StatusCode::Continue,
+            200 => StatusCode::OK,
+            204 => StatusCode::NoContent,
+            400 => StatusCode::BadRequest,
+            404 => StatusCode::NotFound,
+            500 => StatusCode::InternalServerError,
+            501 => StatusCode::NotImplemented,
+            _ => StatusCode::Unknown,
+        }
+    }
+
+    fn parse(code: &str) -> Result<StatusCode, Error> {
+        Ok(StatusCode::from_raw(
+            code.trim().parse().map_err(Error::StatusCodeParsing)?,
+        ))
+    }
+
+    fn is_server_error(self) -> bool {
+        !matches!(
+            self,
+            StatusCode::OK | StatusCode::Continue | StatusCode::NoContent
+        )
+    }
+}
+
+fn get_header<'a>(res: &'a str, header: &'a str) -> Option<&'a str> {
+    let header_str = format!("{}: ", header);
+    if let Some(o) = res.find(&header_str) {
+        Some(&res[o + header_str.len()..o + res[o..].find('\r').unwrap()])
+    } else {
+        None
+    }
+}
+
+fn get_status_code(res: &str) -> Result<StatusCode, Error> {
+    if let Some(o) = res.find("HTTP/1.1") {
+        Ok(StatusCode::parse(
+            &res[o + "HTTP/1.1 ".len()..res[o..].find('\r').unwrap()],
+        )?)
+    } else {
+        Err(Error::MissingProtocol)
+    }
+}
+
+fn parse_http_response(socket: &mut dyn Read) -> Result<Option<String>, Error> {
+    let mut res = String::new();
+    let mut body_offset = None;
+    let mut content_length: Option<usize> = None;
+    loop {
+        let mut bytes = vec![0; 256];
+        let count = socket.read(&mut bytes).map_err(Error::Socket)?;
+        res.push_str(std::str::from_utf8(&bytes[0..count]).unwrap());
+
+        // End of headers
+        if let Some(o) = res.find("\r\n\r\n") {
+            body_offset = Some(o + "\r\n\r\n".len());
+
+            // With all headers available we can see if there is any body
+            content_length = if let Some(length) = get_header(&res, "Content-Length") {
+                Some(length.trim().parse().map_err(Error::ContentLengthParsing)?)
+            } else {
+                None
+            };
+
+            if content_length.is_none() {
+                break;
+            }
+        }
+
+        if let Some(body_offset) = body_offset {
+            if let Some(content_length) = content_length {
+                if res.len() >= content_length + body_offset {
+                    break;
+                }
+            }
+        }
+    }
+    let body_string = content_length.and(Some(String::from(&res[body_offset.unwrap()..])));
+    let status_code = get_status_code(&res)?;
+
+    if status_code.is_server_error() {
+        Err(Error::ServerResponse(status_code, body_string))
+    } else {
+        Ok(body_string)
+    }
+}
+
+pub fn simple_api_command<T: Read + Write>(
+    socket: &mut T,
+    method: &str,
+    c: &str,
+    request_body: Option<&str>,
+) -> Result<(), Error> {
+    socket
+        .write_all(
+            format!(
+                "{} /api/v1/vm.{} HTTP/1.1\r\nHost: localhost\r\nAccept: */*\r\n",
+                method, c
+            )
+            .as_bytes(),
+        )
+        .map_err(Error::Socket)?;
+
+    if let Some(request_body) = request_body {
+        socket
+            .write_all(format!("Content-Length: {}\r\n", request_body.len()).as_bytes())
+            .map_err(Error::Socket)?;
+    }
+
+    socket.write_all(b"\r\n").map_err(Error::Socket)?;
+
+    if let Some(request_body) = request_body {
+        socket
+            .write_all(request_body.as_bytes())
+            .map_err(Error::Socket)?;
+    }
+
+    socket.flush().map_err(Error::Socket)?;
+
+    if let Some(body) = parse_http_response(socket)? {
+        println!("{}", body);
+    }
+    Ok(())
+}