Add caching for CLI

Cargo.toml

@@ -10,6 +10,7 @@ path = "src/lib.rs"
 [[bin]]
 name = "popgetter"
 path = "src/main.rs"
+required-features = ["cache", "formatters"]
 
 [dependencies]
 anyhow = "1.0.75"
@@ -58,5 +59,6 @@ tempfile = "3.12"
 
 
 [features]
-default = ["formatters"]
+default = ["cache", "formatters"]
+cache = []
 formatters = ["dep:geojson"]

src/cli.rs

@@ -1,9 +1,9 @@
 // FromStr is required by EnumString. The compiler seems to not be able to
 // see that and so is giving a warning. Dont remove it
-use anyhow::Result;
+use anyhow::{Context, Result};
 use clap::{Args, Parser, Subcommand};
 use enum_dispatch::enum_dispatch;
-use log::{debug, info};
+use log::{debug, error, info};
 use nonempty::nonempty;
 use polars::frame::DataFrame;
 use popgetter::{
@@ -144,6 +144,33 @@ impl From<OutputFormat> for OutputFormatter {
     }
 }
 
+async fn read_popgetter(config: Config) -> anyhow::Result<Popgetter> {
+    let xdg_dirs = xdg::BaseDirectories::with_prefix("popgetter")?;
+    // TODO: enable cache to be optional
+    let path = xdg_dirs.get_cache_home();
+    // Try to read metadata from cache
+    if path.exists() {
+        match Popgetter::new_with_config_and_cache(config.clone(), &path) {
+            Ok(popgetter) => return Ok(popgetter),
+            Err(err) => {
+                // Log error, continue without cache and attempt to create one
+                error!("Failed to read metadata from cache with error: {err}");
+            }
+        }
+    }
+    // If no metadata cache, get metadata and try to cache
+    std::fs::create_dir_all(&path)?;
+    let popgetter = Popgetter::new_with_config(config).await?;
+
+    // If error creating cache, remove cache path
+    if let Err(err) = popgetter.metadata.write_cache(&path) {
+        std::fs::remove_dir_all(&path)
+            .with_context(|| "Failed to remove cache dir following error writing cache: {err}")?;
+        Err(err)?
+    }
+    Ok(popgetter)
+}
+
 impl RunCommand for DataCommand {
     async fn run(&self, config: Config) -> Result<()> {
         info!("Running `data` subcommand");
@@ -153,7 +180,7 @@ impl RunCommand for DataCommand {
                 DOWNLOADING_SEARCHING_STRING.to_string() + RUNNING_TAIL_STRING,
             )
         });
-        let popgetter = Popgetter::new_with_config(config).await?;
+        let popgetter = read_popgetter(config).await?;
         let search_params: SearchParams = self.search_params_args.clone().into();
         let search_results = popgetter.search(&search_params);
 
@@ -360,7 +387,7 @@ impl RunCommand for MetricsCommand {
                 DOWNLOADING_SEARCHING_STRING.into(),
             )
         });
-        let popgetter = Popgetter::new_with_config(config).await?;
+        let popgetter = read_popgetter(config).await?;
         let search_results = popgetter.search(&self.search_params_args.to_owned().into());
         if let Some(mut s) = sp {
             s.stop_with_symbol(COMPLETE_PROGRESS_STRING);
@@ -400,7 +427,7 @@ impl RunCommand for CountriesCommand {
                 spinner_message.to_string() + RUNNING_TAIL_STRING,
             )
         });
-        let popgetter = Popgetter::new_with_config(config).await?;
+        let popgetter = read_popgetter(config).await?;
         if let Some(mut s) = sp {
             s.stop_with_symbol(COMPLETE_PROGRESS_STRING);
         }

src/config.rs

@@ -1,6 +1,6 @@
 use serde::{Deserialize, Serialize};
 
-#[derive(Serialize, Deserialize, Debug, Clone)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
 #[serde(default)]
 pub struct Config {
     pub base_path: String,

src/lib.rs

@@ -1,9 +1,11 @@
+use std::path::Path;
+
 use anyhow::Result;
 use data_request_spec::DataRequestSpec;
 use log::debug;
 use metadata::Metadata;
 use polars::frame::DataFrame;
-use search::{DownloadParams, Params, SearchParams, SearchResults};
+use search::{Params, SearchParams, SearchResults};
 
 use crate::config::Config;
 
@@ -22,7 +24,8 @@ pub mod metadata;
 pub mod parquet;
 pub mod search;
 
-/// Type for popgetter data and API
+/// Type for popgetter metadata, config and API
+#[derive(Debug, PartialEq)]
 pub struct Popgetter {
     pub metadata: Metadata,
     pub config: Config,
@@ -41,7 +44,16 @@ impl Popgetter {
         Ok(Self { metadata, config })
     }
 
+    // Only include method with "cache" feature since it requires a filesystem
+    #[cfg(feature = "cache")]
+    /// Setup the Popgetter object with custom configuration from cache
+    pub fn new_with_config_and_cache<P: AsRef<Path>>(config: Config, cache: P) -> Result<Self> {
+        let metadata = Metadata::from_cache(cache)?;
+        Ok(Self { metadata, config })
+    }
+
     /// Generates `SearchResults` using popgetter given `SearchParams`
+    // TODO: consider reverting to an API where `SearchParams` are moved, add benches
     pub fn search(&self, search_params: &SearchParams) -> SearchResults {
         search_params
             .clone()
@@ -67,3 +79,23 @@ impl Popgetter {
             .await
     }
 }
+
+#[cfg(test)]
+#[cfg(feature = "cache")]
+mod tests {
+
+    use tempfile::TempDir;
+
+    use super::*;
+
+    #[tokio::test]
+    async fn test_popgetter_cache() -> anyhow::Result<()> {
+        let tempdir = TempDir::new()?;
+        let config = Config::default();
+        let popgetter = Popgetter::new_with_config(config.clone()).await?;
+        popgetter.metadata.write_cache(&tempdir)?;
+        let popgetter_from_cache = Popgetter::new_with_config_and_cache(config, &tempdir)?;
+        assert_eq!(popgetter, popgetter_from_cache);
+        Ok(())
+    }
+}

src/metadata.rs

@@ -1,32 +1,31 @@
 use std::default::Default;
 use std::fmt::Display;
+use std::path::Path;
 
 use anyhow::{anyhow, Result};
 use futures::future::join_all;
 use log::debug;
 use log::info;
 use polars::{
-    frame::DataFrame,
     lazy::{
         dsl::col,
         frame::{IntoLazy, LazyFrame, ScanArgsParquet},
     },
-    prelude::{JoinArgs, JoinType, UnionArgs},
+    prelude::{DataFrame, JoinArgs, JoinType, ParquetCompression, ParquetWriter, UnionArgs},
 };
 use tokio::try_join;
 
 use crate::{config::Config, search::MetricId, COL};
 
-/// This struct contains the base url and names of the files that contain the metadata.
-pub struct PATHS {}
-
-impl PATHS {
-    pub const GEOMETRY_METADATA: &'static str = "geometry_metadata.parquet";
-    pub const METRIC_METADATA: &'static str = "metric_metadata.parquet";
-    pub const COUNTRY: &'static str = "country_metadata.parquet";
-    pub const SOURCE: &'static str = "source_data_releases.parquet";
-    pub const PUBLISHER: &'static str = "data_publishers.parquet";
+/// This module contains the names of the files that contain the metadata.
+pub mod paths {
+    pub const GEOMETRY_METADATA: &str = "geometry_metadata.parquet";
+    pub const METRIC_METADATA: &str = "metric_metadata.parquet";
+    pub const COUNTRY: &str = "country_metadata.parquet";
+    pub const SOURCE: &str = "source_data_releases.parquet";
+    pub const PUBLISHER: &str = "data_publishers.parquet";
 }
+use paths as PATHS;
 
 /// `CountryMetadataLoader` takes a country iso string
 /// along with a CountryMetadataPaths and provides methods
@@ -50,7 +49,7 @@ impl ExpandedMetadata {
 /// from a single `CountryMetadataLoader` or for all countries.
 /// It also provides the various functions for searching and
 /// getting `MetricRequests` from the catalogue.
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub struct Metadata {
     pub metrics: DataFrame,
     pub geometries: DataFrame,
@@ -59,6 +58,59 @@ pub struct Metadata {
     pub countries: DataFrame,
 }
 
+#[cfg(feature = "cache")]
+fn path_to_df<P: AsRef<Path>>(path: P) -> anyhow::Result<DataFrame> {
+    Ok(LazyFrame::scan_parquet(path, ScanArgsParquet::default())?.collect()?)
+}
+
+#[cfg(feature = "cache")]
+fn df_to_file<P: AsRef<Path>>(path: P, df: &DataFrame) -> anyhow::Result<()> {
+    let file = std::fs::File::create(path)?;
+    ParquetWriter::new(file)
+        .with_compression(ParquetCompression::Zstd(None))
+        .finish(&mut df.clone())?;
+    Ok(())
+}
+
+#[cfg(feature = "cache")]
+fn prepend<P: AsRef<Path>>(cache_path: P, file_name: &str) -> std::path::PathBuf {
+    cache_path.as_ref().join(file_name)
+}
+
+// Only include methods with "cache" feature since it requires a filesystem
+#[cfg(feature = "cache")]
+impl Metadata {
+    pub fn from_cache<P: AsRef<Path>>(cache_dir: P) -> anyhow::Result<Self> {
+        let metrics = path_to_df(prepend(&cache_dir, PATHS::METRIC_METADATA))?;
+        let geometries = path_to_df(prepend(&cache_dir, PATHS::GEOMETRY_METADATA))?;
+        let source_data_releases = path_to_df(prepend(&cache_dir, PATHS::SOURCE))?;
+        let data_publishers = path_to_df(prepend(&cache_dir, PATHS::PUBLISHER))?;
+        let countries = path_to_df(prepend(&cache_dir, PATHS::COUNTRY))?;
+        Ok(Self {
+            metrics,
+            geometries,
+            source_data_releases,
+            data_publishers,
+            countries,
+        })
+    }
+
+    pub fn write_cache<P: AsRef<Path>>(&self, cache_dir: P) -> anyhow::Result<()> {
+        df_to_file(prepend(&cache_dir, PATHS::METRIC_METADATA), &self.metrics)?;
+        df_to_file(
+            prepend(&cache_dir, PATHS::GEOMETRY_METADATA),
+            &self.geometries,
+        )?;
+        df_to_file(
+            prepend(&cache_dir, PATHS::SOURCE),
+            &self.source_data_releases,
+        )?;
+        df_to_file(prepend(&cache_dir, PATHS::PUBLISHER), &self.data_publishers)?;
+        df_to_file(prepend(&cache_dir, PATHS::COUNTRY), &self.countries)?;
+        Ok(())
+    }
+}
+
 /// Describes a fully specified selection plan. The MetricIds should all
 /// be the ID variant. Geometry and years are backed in now.
 /// Advice specifies and alternative options that the user should