wip(emacs): Abstract strategy-running

- Show docs and goto def are confirmed working

users/crumb/programs/emacs/lib/syd-strategies-lookup.el

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+;; syd-strategies-lookup.el -*- lexical-binding: t; -*-
+
+(require 'syd-strategies)
+(use-package better-jumper)
+(require 'better-jumper)
+
+(defun syd-strat--run-lookup-strategy (strategy identifier origin)
+  "Safely call a lookup STRATEGY.  A lookup strategy, if it is not an
+interactive command, will be called with the lone argument IDENTIFIER.
+Interactive or not, the procedure is expected to return nil on failure.  Returns
+a marker if STRATEGY returns a buffer or marker, or nil on failure.
+Modifications to the window configuration will be discarded if STRATEGY fails to
+return a buffer or marker."
+  (condition-case-unless-debug e
+      (let ((wconf (current-window-configuration))
+            (result (condition-case-unless-debug e
+                        (if (commandp strategy)
+                            (call-interactively strategy)
+                          (funcall strategy identifier))
+                      (error
+                       (message "Lookup strategy %S threw an error: %s" strategy e)
+                       'fail))))
+        (cond ((eq result 'fail)
+               (set-window-configuration wconf)
+               nil)
+              ((bufferp result)
+               (with-current-buffer result
+                 (point-marker)))
+              ((or result
+                   (null origin)
+                   (/= (point-marker) origin))
+               (prog1 (point-marker)
+                 (set-window-configuration wconf)))))
+    ((error user-error)
+     (message "Lookup strategy %S: %s" strategy e)
+     nil)))
+
+(cl-defun syd-strat--lookup-and-jump-to
+    (strategy-category identifier &key (display-fn #'switch-to-buffer))
+  (let* ((origin (point-marker))
+         (strategies (alist-get strategy-category syd-strat--strategies))
+         ;; TODO: If called with a prefix argument, prompt the user to select a
+         ;; strategy.
+         (result (syd-strat-try-functions-wrapped
+                  #'syd-strat--run-lookup-strategy
+                  strategies identifier origin)))
+    (unwind-protect
+        (when (cond ((null result)
+                     (message "No lookup strategy could find %S" identifier)
+                     nil)
+                    ((markerp result)
+                     (funcall display-fn (marker-buffer result))
+                     (goto-char result)
+                     result)
+                    (result))
+          (with-current-buffer (marker-buffer origin)
+            (better-jumper-set-jump (marker-position origin)))
+          result))
+    (set-marker origin nil)))
+
+(defun syd-strat-lookup-documentation (identifier)
+  (interactive (list (syd-thing-at-point-or-region)))
+  (syd-strat--lookup-and-jump-to :documentation identifier
+                                 :display-fn #'pop-to-buffer))
+
+(defun syd-strat-lookup-definition (identifier)
+  (interactive (list (syd-thing-at-point-or-region)))
+  (syd-strat--lookup-and-jump-to :definition identifier))
+
+(provide 'syd-strategies-lookup)

users/crumb/programs/emacs/lib/syd-strategies-repl.el

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+;; syd-strategies-repl.el -*- lexical-binding: t; -*-
+
+;;;###autoload
+(define-minor-mode syd-repl-mode
+  "A minor mode for repl buffers.  One use is to universally customise the
+display of all repl buffers.")
+
+(provide 'syd-strategies-repl)

users/crumb/programs/emacs/lib/syd-strategies.el

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+;; syd-strategies.el -*- lexical-binding: t; -*-
+
+(require 'syd-text)
+
+;; :documentation : Identifier -> Marker
+(defvar-local syd-strat--strategies nil)
+
+(defun syd-strat-try-functions-wrapped (wrapper fns &rest args)
+  "For each FN in FNS, call WRAPPER with the arguments FN followed by ARGS,
+until a FN returns non-nil."
+  (cl-loop for fn in fns
+           with r = nil
+           do (setq r (apply wrapper fn args))
+           until r
+           finally return r))
+
+(defun syd-strat--set-strategies (category strategies)
+  (cl-loop for ref in-ref syd-strat--strategies
+           until (eq category (car ref))
+           finally do (pp ref)))
+
+(defun syd-set-strategies (modes &rest args)
+  (dolist (mode (ensure-list modes))
+    (let ((hook (intern (format "%s-hook" mode)))
+          (fn-name (intern (format "syd-strat--init-for-%s-h" mode))))
+      (unless (cl-evenp (length args))
+        (signal 'wrong-number-of-arguments args))
+      ;; We use this `defalias' incantation instead of a raw `fset' because the
+      ;; former will properly associate a source location to the definition.
+      (defalias fn-name
+        (function
+         (lambda ()
+           (cl-loop for (category strategies) on args by (lambda (x) (-drop 2 x))
+                    do (syd-strat--set-strategies category strategies)))))
+      (add-hook hook fn-name))))
+
+(provide 'syd-strategies)