refactor(dirvish): extract playlist-target resolution from the create command

Lift the name-validate plus overwrite-prompt loop out of
cj/dired-create-playlist-from-marked into cj/--playlist-resolve-target, leaving
the command a flat filter -> resolve -> write. Add Normal/Boundary/Error tests
for the new seam (real temp music-dir, stubbed prompts only).

2 files changed, 85 insertions, 21 deletions

diff --git a/modules/dirvish-config.el b/modules/dirvish-config.el
index b7e33337e..c86f3d1bf 100644
--- a/modules/dirvish-config.el
+++ b/modules/dirvish-config.el
@@ -119,6 +119,35 @@ through a `../' or absolute path.  Pure helper."
   (and (not (string-empty-p name))
        (not (string-match-p "/" name))))
 
+(defun cj/--playlist-resolve-target ()
+  "Prompt for a playlist name and return the .m3u path to write under `music-dir'.
+Re-prompt until the name is a safe bare filename (no `/').  When the target
+already exists, ask whether to overwrite, cancel, or rename: overwrite returns
+the path, cancel signals a `user-error', rename re-prompts.  Interactive
+prompting only -- the caller does the file write."
+  (let ((base-name nil)
+        (playlist-path nil)
+        (done nil))
+    (while (not done)
+      (setq base-name (cj/--playlist-sanitize-name
+                       (read-string "Playlist name (without .m3u): ")))
+      (cond
+       ((not (cj/--playlist-name-safe-p base-name))
+        (message "Playlist name must be a bare filename, without '/'."))
+       (t
+        (setq playlist-path (expand-file-name (concat base-name ".m3u") music-dir))
+        (if (not (file-exists-p playlist-path))
+            (setq done t)
+          (let ((choice (read-char-choice
+                         (format "Playlist '%s' exists. [o]verwrite, [c]ancel, [r]ename? "
+                                 (file-name-nondirectory playlist-path))
+                         '(?o ?c ?r))))
+            (cl-case choice
+              (?o (setq done t))
+              (?c (user-error "Cancelled playlist creation"))
+              (?r (setq done nil))))))))
+    playlist-path))
+
 (defun cj/dired-create-playlist-from-marked ()
   "Create an .m3u playlist file from marked files in Dired (or Dirvish).
 Filters for audio files, prompts for the playlist name, and saves the resulting
@@ -131,27 +160,7 @@ Filters for audio files, prompts for the playlist name, and saves the resulting
     (if (zerop count)
         (user-error "No audio files marked (extensions: %s)"
                     (string-join cj/audio-file-extensions ", "))
-      (let ((base-name nil)
-            (playlist-path nil)
-            (done nil))
-        (while (not done)
-          (setq base-name (cj/--playlist-sanitize-name
-                           (read-string "Playlist name (without .m3u): ")))
-          (cond
-           ((not (cj/--playlist-name-safe-p base-name))
-            (message "Playlist name must be a bare filename, without '/'."))
-           (t
-            (setq playlist-path (expand-file-name (concat base-name ".m3u") music-dir))
-            (if (not (file-exists-p playlist-path))
-                (setq done t)
-              (let ((choice (read-char-choice
-                             (format "Playlist '%s' exists. [o]verwrite, [c]ancel, [r]ename? "
-                                     (file-name-nondirectory playlist-path))
-                             '(?o ?c ?r))))
-                (cl-case choice
-                  (?o (setq done t))
-                  (?c (user-error "Cancelled playlist creation"))
-                  (?r (setq done nil))))))))
+      (let ((playlist-path (cj/--playlist-resolve-target)))
         (with-temp-file playlist-path
           (dolist (af audio-files)
             (insert af "\n")))
diff --git a/tests/test-dirvish-config-playlist.el b/tests/test-dirvish-config-playlist.el
index d059a899a..14bb94ac7 100644
--- a/tests/test-dirvish-config-playlist.el
+++ b/tests/test-dirvish-config-playlist.el
@@ -10,6 +10,7 @@
 ;;; Code:
 
 (require 'ert)
+(require 'cl-lib)
 (require 'package)
 
 (setq package-user-dir (expand-file-name "elpa" user-emacs-directory))
@@ -93,5 +94,59 @@ lowercase extension list."
   (dolist (bad '("../evil" "../../etc/cron" "/etc/passwd" "sub/dir/name"))
     (should-not (cj/--playlist-name-safe-p bad))))
 
+;;; cj/--playlist-resolve-target
+;;
+;; Drives the real `file-exists-p' against a temp `music-dir' (mocking a C
+;; primitive triggers a native-comp trampoline rebuild that fails under
+;; --batch); only the ordinary `read-string' / `read-char-choice' prompts are
+;; stubbed.
+
+(ert-deftest test-cj--playlist-resolve-target-returns-path-for-new-name ()
+  "Normal: a safe name with no existing file returns its .m3u path under music-dir."
+  (let* ((music-dir (make-temp-file "cj-playlist-" t)))
+    (unwind-protect
+        (cl-letf (((symbol-function 'read-string) (lambda (&rest _) "roadtrip")))
+          (should (equal (expand-file-name "roadtrip.m3u" music-dir)
+                         (cj/--playlist-resolve-target))))
+      (delete-directory music-dir t))))
+
+(ert-deftest test-cj--playlist-resolve-target-reprompts-on-unsafe-name ()
+  "Boundary: an unsafe name (with `/') re-prompts until a safe name is given."
+  (let* ((music-dir (make-temp-file "cj-playlist-" t))
+         (answers '("../escape" "safe"))
+         (asked 0))
+    (unwind-protect
+        (cl-letf (((symbol-function 'read-string)
+                   (lambda (&rest _) (prog1 (nth asked answers) (cl-incf asked))))
+                  ((symbol-function 'message) (lambda (&rest _) nil)))
+          (should (equal (expand-file-name "safe.m3u" music-dir)
+                         (cj/--playlist-resolve-target)))
+          (should (= 2 asked)))
+      (delete-directory music-dir t))))
+
+(ert-deftest test-cj--playlist-resolve-target-overwrite-returns-existing-path ()
+  "Normal: when the target exists, choosing overwrite returns the same path."
+  (let* ((music-dir (make-temp-file "cj-playlist-" t))
+         (existing (expand-file-name "mix.m3u" music-dir)))
+    (unwind-protect
+        (progn
+          (with-temp-file existing (insert "old\n"))
+          (cl-letf (((symbol-function 'read-string) (lambda (&rest _) "mix"))
+                    ((symbol-function 'read-char-choice) (lambda (&rest _) ?o)))
+            (should (equal existing (cj/--playlist-resolve-target)))))
+      (delete-directory music-dir t))))
+
+(ert-deftest test-cj--playlist-resolve-target-cancel-signals-user-error ()
+  "Error: when the target exists, choosing cancel aborts with a `user-error'."
+  (let* ((music-dir (make-temp-file "cj-playlist-" t))
+         (existing (expand-file-name "mix.m3u" music-dir)))
+    (unwind-protect
+        (progn
+          (with-temp-file existing (insert "old\n"))
+          (cl-letf (((symbol-function 'read-string) (lambda (&rest _) "mix"))
+                    ((symbol-function 'read-char-choice) (lambda (&rest _) ?c)))
+            (should-error (cj/--playlist-resolve-target) :type 'user-error)))
+      (delete-directory music-dir t))))
+
 (provide 'test-dirvish-config-playlist)
 ;;; test-dirvish-config-playlist.el ends here