From d6cecb387c867f14a3a9de793e158c874a974253 Mon Sep 17 00:00:00 2001
From: Wuzzy <almikes@aol.com>
Date: Sat, 13 Aug 2016 13:30:38 +0200
Subject: Allow function-based sorting

---
 API.md   | 21 ++++++++++++++++-----
 init.lua |  7 +++++--
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/API.md b/API.md
index 636263a..91dfe87 100644
--- a/API.md
+++ b/API.md
@@ -57,16 +57,27 @@ data.
         * `"abc"`: Alphabetical (default)
         * `"nosort"`: Entries appear in no particular order
         * `"custom"`: Manually define the order of entries in `sorting_data`
+        * `"function"`: Sort by function defined in `sorting_data`
     * `sorting_data`: Additional data for special sorting methods.
-       If `sorting=="custom"`, this field must contain a table (list form) in which
-       the entry IDs are specified in the order they are supposed to appear in the
-       entry list. All entries which are missing in this table will appear in no
-       particular order below the final specified one.
-       This field is not required if `sorting` has any other value
+        * If `sorting=="custom"`, this field must contain a table (list form) in which
+          the entry IDs are specified in the order they are supposed to appear in the
+          entry list. All entries which are missing in this table will appear in no
+          particular order below the final specified one.
+        * If `sorting=="function"`, this field is a compare function to be used as
+          the `comp` parameter of `table.sort`. The parameters given are two entries.
+        * This field is not required if `sorting` has any other value
     * `build_formspec`: The template function. Takes entry data as its
       only parameter (has the data type of the entry data) and must
       return a formspec which is inserted in the Entry tab.
 
+Note: For function-based sorting, the entries provided in the compare function have the
+following format:
+
+    {
+        name = n, -- entry name
+        data = d, -- arbitrary entry data
+    }
+
 #### Using `build_formspec`
 For `build_formspec` you can either define your own function which
 procedurally generates the entry formspec or you use one of the
diff --git a/init.lua b/init.lua
index 6c12494..d7f0860 100644
--- a/init.lua
+++ b/init.lua
@@ -286,13 +286,16 @@ function doc.get_sorted_entry_names(cid)
 	end
 	local comp
 	if cat.def.sorting ~= "nosort" then
+		-- Sorting by user function
+		if cat.def.sorting == "function" then
+			comp = cat.def.sorting_data
 		-- Alphabetic sorting
-		if cat.def.sorting == "abc" or cat.def.sorting == nil then
+		elseif cat.def.sorting == "abc" or cat.def.sorting == nil then
 			comp = function(e1, e2)
 				if reverse_sort_table[e1.name] < reverse_sort_table[e2.name] then return true else return false end
 			end
-			table.sort(entry_table, comp)
 		end
+		table.sort(entry_table, comp)
 	end
 
 	return entry_table
-- 
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