Extract some private submodules from 'bat::assets' (#1850)

src/assets/assets_metadata.rs

@@ -0,0 +1,82 @@
+use std::fs::File;
+use std::path::Path;
+use std::time::SystemTime;
+
+use semver::Version;
+use serde::{Deserialize, Serialize};
+
+use crate::error::*;
+
+#[derive(Debug, PartialEq, Default, Serialize, Deserialize)]
+pub struct AssetsMetadata {
+    bat_version: Option<String>,
+    creation_time: Option<SystemTime>,
+}
+
+const FILENAME: &str = "metadata.yaml";
+
+impl AssetsMetadata {
+    #[cfg(feature = "build-assets")]
+    pub(crate) fn new(current_version: &str) -> AssetsMetadata {
+        AssetsMetadata {
+            bat_version: Some(current_version.to_owned()),
+            creation_time: Some(SystemTime::now()),
+        }
+    }
+
+    #[cfg(feature = "build-assets")]
+    pub(crate) fn save_to_folder(&self, path: &Path) -> Result<()> {
+        let file = File::create(path.join(FILENAME))?;
+        serde_yaml::to_writer(file, self)?;
+
+        Ok(())
+    }
+
+    fn try_load_from_folder(path: &Path) -> Result<Self> {
+        let file = File::open(path.join(FILENAME))?;
+        Ok(serde_yaml::from_reader(file)?)
+    }
+
+    /// Load metadata about the stored cache file from the given folder.
+    ///
+    /// There are several possibilities:
+    ///   - We find a metadata.yaml file and are able to parse it
+    ///       => return the contained information
+    ///   - We find a metadata.yaml file and but are not able to parse it
+    ///       => return a SerdeYamlError
+    ///   - We do not find a metadata.yaml file but a syntaxes.bin or themes.bin file
+    ///       => assume that these were created by an old version of bat and return
+    ///          AssetsMetadata::default() without version information
+    ///   - We do not find a metadata.yaml file and no cached assets
+    ///       => no user provided assets are available, return None
+    pub fn load_from_folder(path: &Path) -> Result<Option<Self>> {
+        match Self::try_load_from_folder(path) {
+            Ok(metadata) => Ok(Some(metadata)),
+            Err(e) => {
+                if let Error::SerdeYamlError(_) = e {
+                    Err(e)
+                } else if path.join("syntaxes.bin").exists() || path.join("themes.bin").exists() {
+                    Ok(Some(Self::default()))
+                } else {
+                    Ok(None)
+                }
+            }
+        }
+    }
+
+    pub fn is_compatible_with(&self, current_version: &str) -> bool {
+        let current_version =
+            Version::parse(current_version).expect("bat follows semantic versioning");
+        let stored_version = self
+            .bat_version
+            .as_ref()
+            .and_then(|ver| Version::parse(ver).ok());
+
+        if let Some(stored_version) = stored_version {
+            current_version.major == stored_version.major
+                && current_version.minor == stored_version.minor
+        } else {
+            false
+        }
+    }
+}