add: implement basic server

src/server.rs

@@ -0,0 +1,61 @@
+use std::{fs, path::Path};
+
+use chrono::Utc;
+use log::info;
+use rouille::Request;
+use anyhow::{Context, Result};
+
+use crate::Rewriter;
+
+pub struct Server {
+    rewriter: Rewriter,
+    // Where we write temporary files
+    workspace_dir: String,
+    // Directory to read configs from
+    template_dir: String,
+    // The symlink that is updated
+    config_dir: String,
+}
+
+impl Server {
+    pub fn new(rewriter: Rewriter, workspace_dir: String, template_dir: String, config_dir: String) -> Self {
+        Self {
+            rewriter,
+            workspace_dir,
+            template_dir,
+            config_dir,
+        }
+    }
+
+    pub fn register(&mut self, request: &Request) -> Result<()> {
+        let ip = request.remote_addr().ip().to_string();
+        info!("Registering {} as a handler", ip);
+        self.rewriter.add_replacement(ip);
+        self.generate_config()?;
+        Ok(())
+    }
+
+    pub fn unregister(&mut self, request: &Request) -> Result<()> {
+        let ip = request.remote_addr().ip().to_string();
+        info!("Deregistering {} as a handler", ip);
+        self.rewriter.remove_replacement(&ip);
+        self.generate_config()?;
+        Ok(())
+    }
+
+    pub fn generate_config(&self) -> Result<()> {
+        // Create a new directory in our workspace
+        let now = Utc::now();
+        // Writes into 2020/01/01/<unix timestamp>
+        // This will fail if we have multiple requests per second
+        let path = Path::new(&self.workspace_dir).join(&now.format("%Y/%m/%d/%s").to_string());
+        let path = path.as_os_str().to_str().unwrap();
+        fs::create_dir_all(path).with_context(|| "creating directory")?;
+        self.rewriter.rewrite_folder(&self.template_dir, path).with_context(|| "generating configs")?;
+        // Finally, symlink it to the output folder; only support Linux for now
+        let symlink = Path::new(&self.workspace_dir).join("symlink.tmp");
+        std::os::unix::fs::symlink(path, &symlink).with_context(|| "creating symlink")?;
+        fs::rename(symlink, &self.config_dir).with_context(|| "renaming symlink")?;
+        Ok(())
+    }
+}