feat(views): make queue view sort order configurable (#154)

Problem: the queue/priority view sort in `sort_tasks_priority()` uses a
hardcoded tiebreak chain (status, priority, due, order, id). Users who
care more about due dates than priority have no way to reorder it.

Solution: add `view.queue.sort` config field (string[]) that defines an
ordered tiebreak chain. `build_queue_comparator()` maps each key to a
comparison function and returns a single comparator. Unknown keys emit a
`log.warn`. The default matches the previous hardcoded behavior.

lua/pending/config.lua

@@ -87,6 +87,7 @@
 ---@field hide_done_categories? boolean
 
 ---@class pending.QueueViewConfig
+---@field sort? string[]
 
 ---@class pending.ViewConfig
 ---@field default? 'category'|'priority'
@@ -133,7 +134,9 @@ local defaults = {
       folding = true,
       hide_done_categories = false,
     },
-    queue = {},
+    queue = {
+      sort = { 'status', 'priority', 'due', 'order', 'id' },
+    },
   },
   keymaps = {
     close = 'q',

lua/pending/views.lua

@@ -106,17 +106,23 @@ local function sort_tasks(tasks)
   end)
 end
 
----@param tasks pending.Task[]
-local function sort_tasks_priority(tasks)
-  table.sort(tasks, function(a, b)
+---@type table<string, fun(a: pending.Task, b: pending.Task): boolean?>
+local sort_key_comparators = {
+  status = function(a, b)
     local ra = status_rank[a.status] or 1
     local rb = status_rank[b.status] or 1
     if ra ~= rb then
       return ra < rb
     end
+    return nil
+  end,
+  priority = function(a, b)
     if a.priority ~= b.priority then
       return a.priority > b.priority
     end
+    return nil
+  end,
+  due = function(a, b)
     local a_due = a.due or ''
     local b_due = b.due or ''
     if a_due ~= b_due then
@@ -128,11 +134,56 @@ local function sort_tasks_priority(tasks)
       end
       return a_due < b_due
     end
+    return nil
+  end,
+  order = function(a, b)
     if a.order ~= b.order then
       return a.order < b.order
     end
-    return a.id < b.id
-  end)
+    return nil
+  end,
+  id = function(a, b)
+    if a.id ~= b.id then
+      return a.id < b.id
+    end
+    return nil
+  end,
+  age = function(a, b)
+    if a.id ~= b.id then
+      return a.id < b.id
+    end
+    return nil
+  end,
+}
+
+---@return fun(a: pending.Task, b: pending.Task): boolean
+local function build_queue_comparator()
+  local log = require('pending.log')
+  local keys = config.get().view.queue.sort or { 'status', 'priority', 'due', 'order', 'id' }
+  local comparators = {}
+  for _, key in ipairs(keys) do
+    local cmp = sort_key_comparators[key]
+    if cmp then
+      table.insert(comparators, cmp)
+    else
+      log.warn('unknown queue sort key: ' .. key)
+    end
+  end
+  return function(a, b)
+    for _, cmp in ipairs(comparators) do
+      local result = cmp(a, b)
+      if result ~= nil then
+        return result
+      end
+    end
+    return false
+  end
+end
+
+---@param tasks pending.Task[]
+local function sort_tasks_priority(tasks)
+  local cmp = build_queue_comparator()
+  table.sort(tasks, cmp)
 end
 
 ---@param tasks pending.Task[]