Add task conditions

modules/ordo/condition.scm

@@ -0,0 +1,38 @@
+(define-module (ordo condition)
+  #:use-moudle (ordo context)
+  #:use-module (ordo action filesystem))
+
+(define (cond:any preds)
+  (lambda (ctx)
+    (let loop ((preds preds))
+      (if (null? preds)
+          #f
+          (let ((p (car preds)))
+            (if (p ctx)
+                #t
+                (loop (cdr preds))))))))
+
+(define (cond:every preds)
+  (lambda (ctx)
+    (let loop ((preds preds))
+      (if (null? preds)
+          #t
+          (let ((p (car preds)))
+            (if (p ctx)
+                (loop (cdr preds))
+                #f))))))
+
+(define (cond:command-available? cmd-name)
+  (lambda (ctx)
+    (let ((_ rc) (run "which" `(,cmd-name)))
+      (zero? rc))))
+
+(define (cond:directory? path)
+  (lambda (ctx)
+    (let ((st ((action:stat path) ctx)))
+      (and st (string=? "directory" (assoc-ref st 'file-type))))))
+
+(define (cond:regular-file? path)
+  (lambda (ctx)
+    (let ((st ((action:stat path) ctx)))
+      (and st (string=? "regular-file" (assoc-ref st 'file-type))))))

modules/ordo/task.scm

@@ -7,28 +7,33 @@
   #:export (task
             task?
             task-description
+            task-condition
             task-action
             task-register
             task-triggers
             run-task))
 
 (define-record-type <task>
-  (make-task description action register triggers)
+  (make-task description condition action register triggers)
   task?
   (description task-description)
+  (condition task-condition)
   (action task-action)
   (register task-register)
   (triggers task-triggers))
 
-(define* (task description action #:key (register #f) (triggers '()))
-  (make-task description action register triggers))
+(define* (task description action #:key (condition (const #t)) (register #f) (triggers '()))
+  (make-task description condition action register triggers))
 
 (define (run-task ctx t)
   (match t
-    (($ <task> description action register triggers)
-     (format #t "RUNNING TASK ~a~%" description)
-     (let ((result (action ctx)))
-       (when register
-         (register-context-var! ctx register result))
-       (when triggers
-         (add-context-triggers! ctx triggers))))))
+    (($ <task> description condition action register triggers)
+     (if (not (condition ctx))
+         (format #t "SKIPPING TASK ~a (precondition not met)~%" description)
+         (begin
+           (format #t "RUNNING TASK ~a~%" description)
+           (let ((result (action ctx)))
+             (when register
+               (register-context-var! ctx register result))
+             (when triggers
+               (add-context-triggers! ctx triggers))))))))