2-custom-sort.lua

local DocSettings = require("docsettings")
local ffiUtil = require("ffi/util")
local FileChooser = require("ui/widget/filechooser")
local _ = require("gettext")

--[[
This algorithm sorts books as follows.

First, it sorts them into three blocks in the following order: in progress,
unread and finished.

The in progress block is then further sorted by access time, where the last
accessed book is sorted first. If the access time is equal, they will be sorted
by their name. Equal access times are not rare on FAT32 because it is only
precise to a day.

The other blocks are sorted only by name.

Directories are considered to have the properties of their 'smallest' child
item, except for the name.
--]]

local function weirdsort(x, y)
    local a = x.sort_item
    local b = y.sort_item

    -- If any sort_item is nil, they are empty directories
    if not a then
        return false
    elseif not b then
        return true
    end

    -- Note that we use the original x and y for the strcoll calls, to sort by
    -- the original directory name.
    if a.opened == b.opened then
        if a.opened then
            if a.status == b.status then
                if a.status == "reading" then
                    if a.attr.access == b.attr.access then
                        return ffiUtil.strcoll(x.text, y.text)
                    else
                        return a.attr.access > b.attr.access
                    end
                else
                    return ffiUtil.strcoll(x.text, y.text)
                end
            else
                return a.status == "reading"
            end
        else
            return ffiUtil.strcoll(x.text, y.text)
        end
    else
        if a.opened then
            return a.status == "reading"
        else
            return b.status ~= "reading"
        end
    end
end

FileChooser.collates.weirdsort = {
    text = _("Wim's custom sort"),
    menu_order = 999,
    can_collate_mixed = true,
    init_sort_func = function(cache)
        return weirdsort, cache
    end,
    mandatory_func = function(item)
        return item.opened and string.format("%d %%", 100 * item.percent_finished) or "–"
    end,
    item_func = function(item)
        if item.attr.mode == "file" then
            local percent_finished, summary
            item.opened = DocSettings:hasSidecarFile(item.path)
            if item.opened then
                local doc_settings = DocSettings:open(item.path)
                percent_finished = doc_settings:readSetting("percent_finished")
                summary = doc_settings:readSetting("summary")
            end
            item.percent_finished = percent_finished or 0
            item.status = summary and summary.status or nil
            item.sort_item = item
        elseif item.attr.mode == "directory" then
            local function smallest_child(dirs, files)
                local first
                if #dirs > 0 then
                    first = dirs[1]
                elseif #files > 0 then
                    first = files[1]
                end

                for i, d in ipairs(dirs) do
                    if weirdsort(d.sort_item, first) then
                        first = d.sort_item
                    end
                end

                for i, f in ipairs(files) do
                    if weirdsort(f.sort_item, first) then
                        first = f.sort_item
                    end
                end
                return first
            end

            local dirs, files = FileChooser:getList(item.path, FileChooser.collates.weirdsort)

            for i, d in ipairs(dirs) do
                local subdirs, subfiles = FileChooser:getList(d.path, FileChooser.collates.weirdsort)
                d.sort_item = smallest_child(subdirs, subfiles)
            end

            item.sort_item = smallest_child(dirs, files)
        end
        return item
    end,
}