add sorter (not working yet)

lua/telescope/_extensions/frecency.lua

@@ -18,7 +18,7 @@ local entry_display = require "telescope.pickers.entry_display"
 local finders       = require "telescope.finders"
 local pickers       = require "telescope.pickers"
 local previewers    = require "telescope.previewers"
-local sorters       = require "telescope.sorters"
+local sorters       = require "telescope._extensions.frecency.sorter"
 local conf          = require('telescope.config').values
 local path = require('telescope.path')
 local utils = require('telescope.utils')
@@ -72,7 +72,7 @@ local frecency = function(opts)
       end,
     },
     previewer = conf.file_previewer(opts),
-    sorter = sorters.get_generic_fuzzy_sorter(), -- TODO: do we have to have our own sorter? we only want filtering
+    sorter    = sorters.get_frecency_sorter()
   }):find()
 end
 

lua/telescope/_extensions/frecency/sorter.lua

@@ -0,0 +1,29 @@
+local sorters = require "telescope.sorters"
+
+local my_sorters = {}
+
+my_sorters.get_frecency_sorter = function(opts)
+  opts = opts or {}
+  opts.ngram_len = 2
+
+  local fuzzy_sorter = sorters.get_generic_fuzzy_sorter(opts)
+
+  local frecency = sorters:new()
+  frecency.scoring_function = function(_, prompt, _, entry)
+    local base_score = fuzzy_sorter:score(prompt, entry)
+
+    if base_score == -1 then
+      return -1
+    end
+
+    if base_score == 0 then
+      return entry.index
+    else
+      return math.min(math.pow(entry.index, 0.25), 2) * base_score
+    end
+  end
+
+  return frecency
+end
+
+return my_sorters