From 89bbffdf3c19fecd00391c2800fd7e90db77a482 Mon Sep 17 00:00:00 2001
From: Joshua Lambert <joshua.lambert@lshtm.ac.uk>
Date: Fri, 22 Nov 2024 15:57:02 +0000
Subject: [PATCH 1/3] add cachem to Imports in DESCRIPTION

---
 DESCRIPTION | 1 +
 1 file changed, 1 insertion(+)

diff --git a/DESCRIPTION b/DESCRIPTION
index b83ed4309..ced76728e 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -32,6 +32,7 @@ BugReports: https://github.com/epiverse-trace/epiparameter/issues
 Depends: 
     R (>= 4.1.0)
 Imports:
+    cachem,
     checkmate,
     cli,
     distcrete,

From 6b4d8a3bc394f1fc81af34a5f3fe7af8f4ebc997 Mon Sep 17 00:00:00 2001
From: Joshua Lambert <joshua.lambert@lshtm.ac.uk>
Date: Fri, 22 Nov 2024 15:57:43 +0000
Subject: [PATCH 2/3] create empty env and cache DB in .onLoad

---
 R/zzz.R | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/R/zzz.R b/R/zzz.R
index 4596c0f14..815a3b69b 100644
--- a/R/zzz.R
+++ b/R/zzz.R
@@ -1,3 +1,15 @@
+# package environment for storing global objects for caching
+cache_env <- new.env(parent = emptyenv())
+
 .onLoad <- function(libname, pkgname) {
   options(epiparameter = epiparameter_options) # nolint undersirable_function_linter
+
+  # create an in-memory cache
+  cache_env$cache <- cachem::cache_mem()
+
+  # suppress DB loading message on package loading
+  db <- suppressMessages(epiparameter_db())
+
+  # store epiparameter library in cache
+  cache_env$cache$set("multi_epiparameter", db)
 }

From 450afceab6636899843b5aa2d7e4937d1de0232b Mon Sep 17 00:00:00 2001
From: Joshua Lambert <joshua.lambert@lshtm.ac.uk>
Date: Fri, 22 Nov 2024 15:58:06 +0000
Subject: [PATCH 3/3] update epiparamter_db to use cached DB

---
 R/epiparameter_db.R | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/R/epiparameter_db.R b/R/epiparameter_db.R
index aee5b4b89..7bfbfac72 100644
--- a/R/epiparameter_db.R
+++ b/R/epiparameter_db.R
@@ -129,7 +129,13 @@ epiparameter_db <- function(disease = "all",
     )
   }
 
-  multi_epiparameter <- .read_epiparameter_db()
+  cache_db <- cache_env$cache$get("multi_epiparameter")
+  if (inherits(cache_db, "multi_epiparameter")) {
+    multi_epiparameter <- cache_env$cache$get("multi_epiparameter")
+  } else {
+    multi_epiparameter <- .read_epiparameter_db()
+  }
+
   attrib <- attributes(multi_epiparameter)
 
   multi_epiparameter <- .filter_epiparameter_db(