feat: add prometheus and protobuf messages

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/nodata-storage/src/backend.rs

@@ -0,0 +1,84 @@
+use std::{
+    env::temp_dir,
+    path::{Path, PathBuf},
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+use anyhow::Context;
+use tokio::io::AsyncWriteExt;
+
+pub struct StorageBackend {
+    location: PathBuf,
+}
+
+impl StorageBackend {
+    pub fn new(location: &Path) -> Self {
+        Self {
+            location: location.into(),
+        }
+    }
+
+    pub fn temp() -> Self {
+        Self::new(&temp_dir().join("nodata"))
+    }
+
+    pub async fn flush_segment(&self, topic: &str, buffer: &[u8]) -> anyhow::Result<String> {
+        let segment_key = uuid::Uuid::now_v7();
+        let segment_path = PathBuf::from("logs")
+            .join(topic)
+            .join(segment_key.to_string());
+        tracing::trace!("writing segment file: {}", segment_path.display());
+        let file_location = self.location.join(&segment_path);
+        if let Some(parent) = file_location.parent() {
+            tokio::fs::create_dir_all(parent)
+                .await
+                .context("failed to create storage backend dir")?;
+        }
+
+        let mut segment_file = tokio::fs::File::create(&file_location).await?;
+        segment_file.write_all(buffer).await?;
+        segment_file.flush().await?;
+
+        Ok(segment_key.to_string())
+    }
+
+    pub async fn append_index(
+        &self,
+        topic: &str,
+        segment_file: &str,
+        time: SystemTime,
+    ) -> anyhow::Result<()> {
+        let index_path = PathBuf::from("indexes").join(topic);
+        tracing::trace!("writing index file: {}", index_path.display());
+        let file_location = self.location.join(&index_path);
+        if let Some(parent) = file_location.parent() {
+            tokio::fs::create_dir_all(parent)
+                .await
+                .context("failed to create storage backend dir, index")?;
+        }
+
+        if !file_location.exists() {
+            tokio::fs::File::create(&file_location).await?;
+        }
+
+        let mut index_file = tokio::fs::File::options()
+            .append(true)
+            .open(&file_location)
+            .await?;
+        index_file
+            .write_all(
+                format!(
+                    "{},{}\n",
+                    time.duration_since(UNIX_EPOCH)
+                        .expect("to be able to get time")
+                        .as_secs(),
+                    segment_file
+                )
+                .as_bytes(),
+            )
+            .await?;
+        index_file.flush().await?;
+
+        Ok(())
+    }
+}