1 files changed, 51 insertions, 0 deletions
diff --git a/app/models/concerns/taskable.rb b/app/models/concerns/taskable.rb
new file mode 100644
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+++ b/app/models/concerns/taskable.rb
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+# Contains functionality for objects that can have task lists in their
+# descriptions.  Task list items can be added with Markdown like "* [x] Fix
+# bugs".
+#
+# Used by MergeRequest and Issue
+module Taskable
+  TASK_PATTERN_MD = /^(?<bullet> *[*-] *)\[(?<checked>[ xX])\]/.freeze
+  TASK_PATTERN_HTML = /^<li>\[(?<checked>[ xX])\]/.freeze
+
+  # Change the state of a task list item for this Taskable.  Edit the object's
+  # description by finding the nth task item and changing its checkbox
+  # placeholder to "[x]" if +checked+ is true, or "[ ]" if it's false.
+  # Note: task numbering starts with 1
+  def update_nth_task(n, checked)
+    index = 0
+    check_char = checked ? 'x' : ' '
+
+    # Do this instead of using #gsub! so that ActiveRecord detects that a field
+    # has changed.
+    self.description = self.description.gsub(TASK_PATTERN_MD) do |match|
+      index += 1
+      case index
+      when n then "#{$LAST_MATCH_INFO[:bullet]}[#{check_char}]"
+      else match
+      end
+    end
+
+    save
+  end
+
+  # Return true if this object's description has any task list items.
+  def tasks?
+    description && description.match(TASK_PATTERN_MD)
+  end
+
+  # Return a string that describes the current state of this Taskable's task
+  # list items, e.g. "20 tasks (12 done, 8 unfinished)"
+  def task_status
+    return nil unless description
+
+    num_tasks = 0
+    num_done = 0
+
+    description.scan(TASK_PATTERN_MD) do
+      num_tasks += 1
+      num_done += 1 unless $LAST_MATCH_INFO[:checked] == ' '
+    end
+
+    "#{num_tasks} tasks (#{num_done} done, #{num_tasks - num_done} unfinished)"
+  end
+end