From b8d031cd0cff8bc155d962e35a781ed934999a58 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arpad=20M=C3=BCller?= <arpad-m@users.noreply.github.com>
Date: Fri, 5 Jul 2024 22:18:05 +0200
Subject: [PATCH] Improve parsing of `ImageCompressionAlgorithm` (#8281)

Improve parsing of the `ImageCompressionAlgorithm` enum to allow level
customization like `zstd(1)`, as strum only takes `Default::default()`,
i.e. `None` as the level.

Part of #5431
---
 libs/pageserver_api/src/models.rs | 64 +++++++++++++++++++++++++------
 1 file changed, 52 insertions(+), 12 deletions(-)

diff --git a/libs/pageserver_api/src/models.rs b/libs/pageserver_api/src/models.rs
index ecc543917e56..49c942938dfd 100644
--- a/libs/pageserver_api/src/models.rs
+++ b/libs/pageserver_api/src/models.rs
@@ -9,6 +9,7 @@ use std::{
     collections::HashMap,
     io::{BufRead, Read},
     num::{NonZeroU64, NonZeroUsize},
+    str::FromStr,
     sync::atomic::AtomicUsize,
     time::{Duration, SystemTime},
 };
@@ -437,18 +438,7 @@ pub enum CompactionAlgorithm {
     Tiered,
 }
 
-#[derive(
-    Debug,
-    Clone,
-    Copy,
-    PartialEq,
-    Eq,
-    Serialize,
-    Deserialize,
-    strum_macros::FromRepr,
-    strum_macros::EnumString,
-)]
-#[strum(serialize_all = "kebab-case")]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub enum ImageCompressionAlgorithm {
     /// Disabled for writes, and never decompress during reading.
     /// Never set this after you've enabled compression once!
@@ -468,6 +458,31 @@ impl ImageCompressionAlgorithm {
     }
 }
 
+impl FromStr for ImageCompressionAlgorithm {
+    type Err = anyhow::Error;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut components = s.split(['(', ')']);
+        let first = components
+            .next()
+            .ok_or_else(|| anyhow::anyhow!("empty string"))?;
+        match first {
+            "disabled-no-decompress" => Ok(ImageCompressionAlgorithm::DisabledNoDecompress),
+            "disabled" => Ok(ImageCompressionAlgorithm::Disabled),
+            "zstd" => {
+                let level = if let Some(v) = components.next() {
+                    let v: i8 = v.parse()?;
+                    Some(v)
+                } else {
+                    None
+                };
+
+                Ok(ImageCompressionAlgorithm::Zstd { level })
+            }
+            _ => anyhow::bail!("invalid specifier '{first}'"),
+        }
+    }
+}
+
 #[derive(Eq, PartialEq, Debug, Clone, Serialize, Deserialize)]
 pub struct CompactionAlgorithmSettings {
     pub kind: CompactionAlgorithm,
@@ -1660,4 +1675,29 @@ mod tests {
             AuxFilePolicy::CrossValidation
         );
     }
+
+    #[test]
+    fn test_image_compression_algorithm_parsing() {
+        use ImageCompressionAlgorithm::*;
+        assert_eq!(
+            ImageCompressionAlgorithm::from_str("disabled").unwrap(),
+            Disabled
+        );
+        assert_eq!(
+            ImageCompressionAlgorithm::from_str("disabled-no-decompress").unwrap(),
+            DisabledNoDecompress
+        );
+        assert_eq!(
+            ImageCompressionAlgorithm::from_str("zstd").unwrap(),
+            Zstd { level: None }
+        );
+        assert_eq!(
+            ImageCompressionAlgorithm::from_str("zstd(18)").unwrap(),
+            Zstd { level: Some(18) }
+        );
+        assert_eq!(
+            ImageCompressionAlgorithm::from_str("zstd(-3)").unwrap(),
+            Zstd { level: Some(-3) }
+        );
+    }
 }