From 7d461a7d4f62d357a224741b9e808f1abada8d15 Mon Sep 17 00:00:00 2001
From: Sean Allred <code@seanallred.com>
Date: Sun, 2 Nov 2014 11:52:08 -0500
Subject: Introduce persistent storage for filters

---
 stack-filter.el | 39 +++++++++++++++++++++++++++++++++++++++
 test/tests.el   | 19 +++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/stack-filter.el b/stack-filter.el
index 0229ad1..e5fb54d 100644
--- a/stack-filter.el
+++ b/stack-filter.el
@@ -32,6 +32,9 @@
 
 ;;; Customizations
 
+(defconst stack-filter-cache-file
+  "filters.el")
+
 (defvar stack-filter
   'default
   "The current filter.
@@ -66,6 +69,42 @@ or string."
        (cdr (assoc 'filter
                    (elt response 0)))))))
 
+
+;;; Storage and Retrieval
+
+(defun stack-filter-get (filter)
+  "Retrieve named FILTER from `stack-filter-cache-file'."
+  (with-current-buffer (stack-cache-get-file stack-filter-cache-file)
+    (or (cdr (ignore-errors (assoc filter (read (buffer-string)))))
+        nil)))
+
+(defun stack-filter-store (name filter)
+  "Store NAME as FILTER in `stack-filter-cache-file'.
+
+NAME should be a symbol and FILTER is a string as compiled by
+`stack-filter-compile'."
+  (unless (symbolp name)
+    (error "Name must be a symbol: %S" name))
+  (with-current-buffer (stack-cache-get-file stack-filter-cache-file)
+    (let* ((dict (or (ignore-errors
+                       (read (buffer-string)))
+                     nil))
+           (entry (assoc name dict)))
+      (if entry (setf (cdr entry) filter)
+        (setq dict (cons (cons name filter) dict)))
+      (erase-buffer)
+      (insert (prin1-to-string dict))
+      (save-buffer)
+      dict)))
+
+;;; TODO tail recursion should be made more efficient for the
+;;; byte-compiler
+(defun stack-filter-store-all (name-filter-alist)
+  (when name-filter-alist
+    (stack-filter-store
+     (caar name-filter-alist)
+     (cdar name-filter-alist))
+    (stack-filter-store-all (cdr name-filter-alist))))
 
 (provide 'stack-filter)
 ;;; stack-filter.el ends here
diff --git a/test/tests.el b/test/tests.el
index 44b0de0..fa60364 100644
--- a/test/tests.el
+++ b/test/tests.el
@@ -75,3 +75,22 @@
                              ((should-not-go))
                              ((1 . alpha) (2 . beta))]
                             '(1 2 3)))))
+
+(ert-deftest test-filters ()
+  ;; Ensure the file is empty
+  (ignore-errors
+    (delete-file
+     (stack-cache-get-file-name
+      stack-filter-cache-file)))
+
+  (should-error (stack-filter-store "names must be symbols"
+                                    "this is a filter"))
+  ;; basic use
+  (should (equal '((test . "filter"))
+                 (stack-filter-store 'test "filter")))
+  ;; aggregation
+  (should (equal '((test2 . "filter2") (test . "filter"))
+                 (stack-filter-store 'test2 "filter2")))
+  ;; mutation
+  (should (equal '((test2 . "filter2") (test . "filter-test"))
+                 (stack-filter-store 'test "filter-test"))))
-- 
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