implement caching of packages for 12 hours

_conda

@@ -16,6 +16,14 @@
 #     $ fpath+=$PWD/conda-zsh-completion
 #     $ compinit conda-zsh-completion
 #
+# To activate the completion cache for packages, add the following to your
+# .zshrc:
+#
+#     zstyle ':completion::complete:*' use-cache 1
+#
+# To forcefully clean the completion cache, look in '~/.zcompcache' and remove
+# file starting with 'conda_'.
+#
 # TODO
 # ----
 #
@@ -24,8 +32,8 @@
 #   * 'conda config --get' only completes a single option.
 #   * 'conda config --add' completes only the key, not the value.
 #   * Similar issues for other options.
-# * Completion for 'conda install' and others that query list of available or
-#   existing packages is slow, consider caching.
+# * Example of activating cache only for conda completion
+# * Make cache policy configurable
 # * Completion for version numbers is entirely missing:
 #   e.g. 'conda install numpy==<TAB>' should complete all available versions of
 #   numpy.
@@ -46,21 +54,29 @@ __conda_envs(){
 }
 
 __conda_packages_installed(){
-    local -a packages
-    packages=($(conda list | sed 1,2d | cut -f1 -d' '))
-    _describe -t packages 'installed packages' packages
+    zstyle ":completion:${curcontext}:" cache-policy _conda_caching_policy
+    local -a installed_packages
+    if _cache_invalid conda_installed_packages || ! _retrieve_cache conda_installed_packages ; then
+        installed_packages=($(conda list | sed 1,2d | cut -f1 -d' '))
+        _store_cache conda_installed_packages installed_packages
+    fi
+    _describe -t installed_packages 'installed packages' installed_packages
 }
 
 __conda_packages_search(){
-    local -a packages
-    packages=($(conda search --use-index-cache --json |
-    python -c "
+    zstyle ":completion:${curcontext}:" cache-policy _conda_caching_policy
+    local -a available_packages
+    if _cache_invalid conda_available_packages || ! _retrieve_cache conda_available_packages ; then
+        available_packages=($(conda search --use-index-cache --json |
+        python -c "
 import json, sys
 parsed = json.load(sys.stdin)
 for k in parsed.keys():
     print(k)
         "))
-    _describe -t packages 'available packages' packages
+        _store_cache conda_available_packages available_packages
+    fi
+    _describe -t available_packages 'available packages' available_packages
 }
 
 __conda_channels(){
@@ -128,6 +144,12 @@ __conda_commands(){
     _describe -t special_commands "special commands"  special
 }
 
+_conda_caching_policy() {
+  local -a oldp
+  oldp=( "$1"(Nmh+12) ) # 12 hour
+  (( $#oldp ))
+}
+
 local -a opts
 opts=(
     '(-h --help)'{-h,--help}'[show this help message and exit]'