local BD = require("ui/bidi")
local ConfirmBox = require("ui/widget/confirmbox")
local DataStorage = require("datastorage")
local Device = require("device")
local DictQuickLookup = require("ui/widget/dictquicklookup")
local Event = require("ui/event")
local Geom = require("ui/geometry")
local InfoMessage = require("ui/widget/infomessage")
local InputDialog = require("ui/widget/inputdialog")
local JSON = require("json")
local KeyValuePage = require("ui/widget/keyvaluepage")
local LuaData = require("luadata")
local MultiConfirmBox = require("ui/widget/multiconfirmbox")
local NetworkMgr = require("ui/network/manager")
local SortWidget = require("ui/widget/sortwidget")
local Trapper = require("ui/trapper")
local UIManager = require("ui/uimanager")
local WidgetContainer = require("ui/widget/container/widgetcontainer")
local ffi = require("ffi")
local C = ffi.C
local ffiUtil  = require("ffi/util")
local lfs = require("libs/libkoreader-lfs")
local logger = require("logger")
local time = require("ui/time")
local util  = require("util")
local _ = require("gettext")
local Input = Device.input
local T = ffiUtil.template

-- We'll store the list of available dictionaries as a module local
-- so we only have to look for them on the first :init()
local available_ifos = nil
local lookup_history = nil

local function getIfosInDir(path)
    -- Get all the .ifo under directory path.
    -- Don't walk into "res/" subdirectories, as per Stardict specs, they
    -- may contain possibly many resource files (image, audio files...)
    -- that could slow down our walk here.
    local ifos = {}
    local ok, iter, dir_obj = pcall(lfs.dir, path)
    if ok then
        for name in iter, dir_obj do
            if name ~= "." and name ~= ".." and name ~= "res" then
                local fullpath = path.."/"..name
                local attributes = lfs.attributes(fullpath)
                if attributes ~= nil then
                    if attributes.mode == "directory" then
                        local dirifos = getIfosInDir(fullpath) -- recurse
                        for _, ifo in pairs(dirifos) do
                            table.insert(ifos, ifo)
                        end
                    elseif fullpath:match("%.ifo$") then
                        table.insert(ifos, fullpath)
                    end
                end
            end
        end
    end
    return ifos
end

local ReaderDictionary = WidgetContainer:extend{
    data_dir = nil,
    lookup_msg = _("Searching dictionary for:\n%1"),
}

-- For a HTML dict, one can specify a specific stylesheet
-- in a file named as the .ifo with a .css extension
local function readDictionaryCss(path)
    local f = io.open(path, "r")
    if not f then
        return nil
    end

    local content = f:read("*all")
    f:close()
    return content
end

-- For a HTML dict, one can specify a function called on
-- the raw returned definition to "fix" the HTML if needed
-- (as MuPDF, used for rendering, is quite sensitive to the
-- HTML quality) in a file named as the .ifo with a .lua
-- extension, containing for example:
--    return function(html)
--        html = html:gsub("<hr>", "<hr/>")
--        return html
--    end
local function getDictionaryFixHtmlFunc(path)
    if lfs.attributes(path, "mode") == "file" then
        local ok, func = pcall(dofile, path)
        if ok and func then
            return func
        else
            logger.warn("Dict's user provided file failed:", func)
        end
    end
end

function ReaderDictionary:init()
    self.disable_lookup_history = G_reader_settings:isTrue("disable_lookup_history")
    self.dicts_order = G_reader_settings:readSetting("dicts_order", {})
    self.dicts_disabled = G_reader_settings:readSetting("dicts_disabled", {})
    self.disable_fuzzy_search_fm = G_reader_settings:isTrue("disable_fuzzy_search")

    if self.ui then
        self.ui.menu:registerToMainMenu(self)
    end
    self.data_dir = G_defaults:readSetting("STARDICT_DATA_DIR") or
        os.getenv("STARDICT_DATA_DIR") or
        DataStorage:getDataDir() .. "/data/dict"

    -- Show the "Seaching..." InfoMessage after this delay
    self.lookup_msg_delay = 0.5
    -- Allow quick interruption or dismiss of search result window
    -- with tap if done before this delay. After this delay, the
    -- result window is shown and dismiss prevented for a few 100ms
    self.quick_dismiss_before_delay = time.s(3)

    -- Gather info about available dictionaries
    if not available_ifos then
        available_ifos = {}
        logger.dbg("Getting list of dictionaries")
        local ifo_files = getIfosInDir(self.data_dir)
        local dict_ext = self.data_dir.."_ext"
        if lfs.attributes(dict_ext, "mode") == "directory" then
            local extifos = getIfosInDir(dict_ext)
            for _, ifo in pairs(extifos) do
                table.insert(ifo_files, ifo)
            end
        end
        for _, ifo_file in pairs(ifo_files) do
            local f = io.open(ifo_file, "r")
            if f then
                local content = f:read("*all")
                f:close()
                local dictname = content:match("\nbookname=(.-)\r?\n")
                local is_html = content:find("sametypesequence=h", 1, true) ~= nil
                local lang_in, lang_out = content:match("lang=(%a+)-?(%a*)\r?\n?")
                -- sdcv won't use dict that don't have a bookname=
                if dictname then
                    table.insert(available_ifos, {
                        file = ifo_file,
                        name = dictname,
                        is_html = is_html,
                        css = readDictionaryCss(ifo_file:gsub("%.ifo$", ".css")),
                        fix_html_func = getDictionaryFixHtmlFunc(ifo_file:gsub("%.ifo$", ".lua")),
                        lang = lang_in and { lang_in = lang_in, lang_out = lang_out },
                    })
                end
            end
        end
        logger.dbg("found", #available_ifos, "dictionaries")
        self:sortAvailableIfos()
    end
    -- Prepare the -u options to give to sdcv the dictionary order and if some are disabled
    self:updateSdcvDictNamesOptions()

    if not lookup_history then
        lookup_history = LuaData:open(DataStorage:getSettingsDir() .. "/lookup_history.lua", "LookupHistory")
    end
end

function ReaderDictionary:sortAvailableIfos()
    table.sort(available_ifos, function(lifo, rifo)
        local lord = self.dicts_order[lifo.file]
        local rord = self.dicts_order[rifo.file]

        -- Both ifos without an explicit position -> lexical comparison
        if lord == rord then
            return ffiUtil.strcoll(lifo.name, rifo.name)
        end

        -- Ifos without an explicit position come last.
        return lord ~= nil and (rord == nil or lord < rord)
    end)
end


function ReaderDictionary:updateSdcvDictNamesOptions()
    -- We cannot tell sdcv which dictionaries to ignore, but we
    -- can tell it which dictionaries to use, by using multiple
    -- -u <dictname> options.
    -- The order of the -u options controls the dictionary order
    -- that sdcv uses to order its results.

    self.enabled_dict_names = {}

    -- First, insert any preferred dicts, even if globally disabled
    -- (this might allow enabling a dict only for a specific book,
    -- while keeping it disabled for all others)
    local preferred_names_already_in = {}
    if self.preferred_dictionaries then
        for _, name in ipairs(self.preferred_dictionaries) do
            table.insert(self.enabled_dict_names, name)
            preferred_names_already_in[name] = true
        end
    end

    local dicts_disabled = G_reader_settings:readSetting("dicts_disabled")
    for _, ifo in pairs(available_ifos) do
        if not dicts_disabled[ifo.file] and not preferred_names_already_in[ifo.name] then
            table.insert(self.enabled_dict_names, ifo.name)
        end
    end
end

function ReaderDictionary:addToMainMenu(menu_items)
    menu_items.search_settings = { -- submenu with Dict, Wiki, Translation settings
        text = _("Settings"),
    }
    menu_items.dictionary_lookup = {
        text = _("Dictionary lookup"),
        callback = function()
            self:onShowDictionaryLookup()
        end,
    }
    menu_items.dictionary_lookup_history = {
        text = _("Dictionary lookup history"),
        enabled_func = function()
            return lookup_history:has("lookup_history")
        end,
        callback = function()
            local lookup_history_table = lookup_history:readSetting("lookup_history")
            local kv_pairs = {}
            local previous_title
            for i = #lookup_history_table, 1, -1 do
                local value = lookup_history_table[i]
                if value.book_title ~= previous_title then
                    table.insert(kv_pairs, { value.book_title..":", "" })
                end
                previous_title = value.book_title
                table.insert(kv_pairs, {
                    os.date("%Y-%m-%d %H:%M:%S", value.time),
                    value.word,
                    callback = function()
                        -- Word had been cleaned before being added to history
                        self:onLookupWord(value.word, true)
                    end
                })
            end
            UIManager:show(KeyValuePage:new{
                title = _("Dictionary lookup history"),
                value_overflow_align = "right",
                kv_pairs = kv_pairs,
            })
        end,
    }
    menu_items.dictionary_settings = {
        text = _("Dictionary settings"),
        sub_item_table = {
            {
                keep_menu_open = true,
                text_func = function()
                    local nb_available, nb_enabled, nb_disabled = self:getNumberOfDictionaries()
                    local nb_str = nb_available
                    if nb_disabled > 0 then
                        nb_str = nb_enabled .. "/" .. nb_available
                    end
                    return T(_("Manage dictionaries: %1"), nb_str)
                end,
                enabled_func = function()
                    return self:getNumberOfDictionaries() > 0
                end,
                callback = function(touchmenu_instance)
                    self:showDictionariesMenu(function()
                        if touchmenu_instance then touchmenu_instance:updateItems() end
                    end)
                end,
            },
            {
                text = _("Download dictionaries"),
                sub_item_table_func = function() return self:_genDownloadDictionariesMenu() end,
            },
            {
                text_func = function()
                    local text = _("Enable fuzzy search")
                    if G_reader_settings:nilOrFalse("disable_fuzzy_search") then
                        text = text .. "   ★"
                    end
                    return text
                end,
                checked_func = function()
                    if self.ui.doc_settings then
                        return not self.disable_fuzzy_search
                    end
                    return not self.disable_fuzzy_search_fm
                end,
                callback = function()
                    if self.ui.doc_settings then
                        self.disable_fuzzy_search = not self.disable_fuzzy_search
                        self.ui.doc_settings:saveSetting("disable_fuzzy_search", self.disable_fuzzy_search)
                    else
                        self.disable_fuzzy_search_fm = not self.disable_fuzzy_search_fm
                    end
                end,
                hold_callback = function(touchmenu_instance)
                    self:toggleFuzzyDefault(touchmenu_instance)
                end,
                separator = true,
            },
            {
                text = _("Enable dictionary lookup history"),
                checked_func = function()
                    return not self.disable_lookup_history
                end,
                callback = function()
                    self.disable_lookup_history = not self.disable_lookup_history
                    G_reader_settings:saveSetting("disable_lookup_history", self.disable_lookup_history)
                end,
            },
            {
                text = _("Clean dictionary lookup history"),
                enabled_func = function()
                    return lookup_history:has("lookup_history")
                end,
                keep_menu_open = true,
                callback = function(touchmenu_instance)
                    UIManager:show(ConfirmBox:new{
                        text = _("Clean dictionary lookup history?"),
                        ok_text = _("Clean"),
                        ok_callback = function()
                            -- empty data table to replace current one
                            lookup_history:reset{}
                            touchmenu_instance:updateItems()
                        end,
                    })
                end,
                separator = true,
            },
            { -- setting used by dictquicklookup
                text = _("Large window"),
                checked_func = function()
                    return G_reader_settings:isTrue("dict_largewindow")
                end,
                callback = function()
                    G_reader_settings:flipNilOrFalse("dict_largewindow")
                end,
            },
            { -- setting used by dictquicklookup
                text = _("Justify text"),
                checked_func = function()
                    return G_reader_settings:nilOrTrue("dict_justify")
                end,
                callback = function()
                    G_reader_settings:flipNilOrTrue("dict_justify")
                end,
            },
            { -- setting used by dictquicklookup
                text_func = function()
                    local font_size = G_reader_settings:readSetting("dict_font_size") or 20
                    return T(_("Font size: %1"), font_size)
                end,
                callback = function(touchmenu_instance)
                    local SpinWidget = require("ui/widget/spinwidget")
                    local font_size = G_reader_settings:readSetting("dict_font_size") or 20
                    local items_font = SpinWidget:new{
                        value = font_size,
                        value_min = 8,
                        value_max = 32,
                        default_value = 20,
                        title_text = _("Dictionary font size"),
                        callback = function(spin)
                            G_reader_settings:saveSetting("dict_font_size", spin.value)
                            if touchmenu_instance then touchmenu_instance:updateItems() end
                        end,
                    }
                    UIManager:show(items_font)
                end,
                keep_menu_open = true,
            }
        }
    }
    if Device:canExternalDictLookup() then
        local function genExternalDictItems()
            local items_table = {}
            for i, v in ipairs(Device:getExternalDictLookupList()) do
                local setting = v[1]
                local dict_name = v[2]
                local is_enabled = v[3]
                table.insert(items_table, {
                    text = dict_name,
                    checked_func = function()
                        return setting == G_reader_settings:readSetting("external_dict_lookup_method")
                    end,
                    enabled_func = function()
                        return is_enabled == true
                    end,
                    callback = function()
                        G_reader_settings:saveSetting("external_dict_lookup_method", v[1])
                    end,
                })
            end
            return items_table
        end
        table.insert(menu_items.dictionary_settings.sub_item_table, 1, {
            text = _("Use external dictionary"),
            checked_func = function()
                return G_reader_settings:isTrue("external_dict_lookup")
            end,
            callback = function()
                G_reader_settings:flipNilOrFalse("external_dict_lookup")
            end,
        })
        table.insert(menu_items.dictionary_settings.sub_item_table, 2, {
            text_func = function()
                local display_name = _("none")
                local ext_id = G_reader_settings:readSetting("external_dict_lookup_method")
                for i, v in ipairs(Device:getExternalDictLookupList()) do
                    if v[1] == ext_id then
                        display_name = v[2]
                        break
                    end
                end
                return T(_("Dictionary: %1"), display_name)
            end,
            enabled_func = function()
                return G_reader_settings:isTrue("external_dict_lookup")
            end,
            sub_item_table = genExternalDictItems(),
            separator = true,
        })
    end
end

function ReaderDictionary:onLookupWord(word, is_sane, boxes, highlight, link, tweak_buttons_func)
    logger.dbg("dict lookup word:", word, boxes)
    -- escape quotes and other funny characters in word
    word = self:cleanSelection(word, is_sane)
    logger.dbg("dict stripped word:", word)

    self.highlight = highlight
    local disable_fuzzy_search
    if self.ui.doc_settings then
        disable_fuzzy_search = self.disable_fuzzy_search
    else
        disable_fuzzy_search = self.disable_fuzzy_search_fm
    end

    -- Wrapped through Trapper, as we may be using Trapper:dismissablePopen() in it
    Trapper:wrap(function()
        self:stardictLookup(word, self.enabled_dict_names, not disable_fuzzy_search, boxes, link, tweak_buttons_func)
    end)
    return true
end

function ReaderDictionary:onHtmlDictionaryLinkTapped(dictionary, link)
    if not link.uri then
        return
    end

    -- The protocol is either "bword" or there is no protocol, only the word.
    -- https://github.com/koreader/koreader/issues/3588#issuecomment-357088125
    local url_prefix = "bword://"
    local word
    if link.uri:sub(1,url_prefix:len()) == url_prefix then
        word = link.uri:sub(url_prefix:len() + 1)
    elseif link.uri:find("://") then
        return
    else
        word = link.uri
    end

    if word == "" then
        return
    end

    local link_box = Geom:new{
        x = link.x0,
        y = link.y0,
        w = math.abs(link.x1 - link.x0),
        h = math.abs(link.y1 - link.y0),
    }

    -- Only the first dictionary window stores the highlight, this way the highlight
    -- is only removed when there are no more dictionary windows open.
    self.highlight = nil

    -- Wrapped through Trapper, as we may be using Trapper:dismissablePopen() in it
    Trapper:wrap(function()
        self:stardictLookup(word, {dictionary}, false, {link_box}, nil)
    end)
end

--- Gets number of available, enabled, and disabled dictionaries
-- @treturn int nb_available
-- @treturn int nb_enabled
-- @treturn int nb_disabled
function ReaderDictionary:getNumberOfDictionaries()
    local nb_available = #available_ifos
    local nb_enabled = 0
    local nb_disabled = 0
    for _, ifo in pairs(available_ifos) do
        if self.dicts_disabled[ifo.file] then
            nb_disabled = nb_disabled + 1
        else
            nb_enabled = nb_enabled + 1
        end
    end
    return nb_available, nb_enabled, nb_disabled
end

function ReaderDictionary:_genDownloadDictionariesMenu()
    local downloadable_dicts = require("ui/data/dictionaries")
    local IsoLanguage = require("ui/data/isolanguage")
    local languages = {}

    for i = 1, #downloadable_dicts do
        local dict = downloadable_dicts[i]
        if not dict.ifo_lang then
            -- this only needs to happen the first time this function is called
            local ifo_in = IsoLanguage:getBCPLanguageTag(dict.lang_in)
            local ifo_out = IsoLanguage:getBCPLanguageTag(dict.lang_out)
            dict.ifo_lang = ("%s-%s"):format(ifo_in, ifo_out)
            dict.lang_in = IsoLanguage:getLocalizedLanguage(dict.lang_in)
            dict.lang_out = IsoLanguage:getLocalizedLanguage(dict.lang_out)
        end
        local dict_lang_in = dict.lang_in
        local dict_lang_out = dict.lang_out
        if not languages[dict_lang_in] then
            languages[dict_lang_in] = {}
        end
        table.insert(languages[dict_lang_in], dict)
        if not languages[dict_lang_out] then
            languages[dict_lang_out] = {}
        end
        table.insert(languages[dict_lang_out], dict)
    end

    -- remove duplicates
    for lang_key,lang in pairs(languages) do
        local hash = {}
        local res = {}
        for k,v in ipairs(lang) do
           if not hash[v.name] then
               res[#res+1] = v
               hash[v.name] = true
           end
        end
        languages[lang_key] = res
    end

    local menu_items = {}
    for lang_key, available_langs in ffiUtil.orderedPairs(languages) do
        table.insert(menu_items, {
            keep_menu_open = true,
            text = lang_key,
            callback = function()
                self:showDownload(available_langs)
            end
        })
    end

    return menu_items
end

function ReaderDictionary:showDictionariesMenu(changed_callback)
    -- Work on local copy, save to settings only when SortWidget is closed with the accept button
    local dicts_disabled = util.tableDeepCopy(self.dicts_disabled)

    local sort_items = {}
    for _, ifo in pairs(available_ifos) do
        table.insert(sort_items, {
            text = ifo.name,
            callback = function()
                if dicts_disabled[ifo.file] then
                    dicts_disabled[ifo.file] = nil
                else
                    dicts_disabled[ifo.file] = true
                end
            end,
            checked_func = function()
                return not dicts_disabled[ifo.file]
            end,
            ifo = ifo,
        })
    end

    local sort_widget = SortWidget:new{
        title = _("Manage installed dictionaries"),
        item_table = sort_items,
        callback = function()
            -- Update both references to point to that new object
            self.dicts_disabled = dicts_disabled
            G_reader_settings:saveSetting("dicts_disabled", self.dicts_disabled)

            -- Write back the sorted items array to dicts_order
            local dicts_order = {}
            for i, sort_item in ipairs(sort_items) do
                dicts_order[sort_item.ifo.file] = i
            end
            self.dicts_order = dicts_order
            G_reader_settings:saveSetting("dicts_order", self.dicts_order)

            self:sortAvailableIfos()

            self:updateSdcvDictNamesOptions()

            UIManager:setDirty(nil, "ui")
            changed_callback()
        end
    }
    UIManager:show(sort_widget)
end

local function dictDirsEmpty(dict_dirs)
    for _, dict_dir in ipairs(dict_dirs) do
        if not util.isEmptyDir(dict_dir) then
            return false
        end
    end
    return true
end

local function getAvailableIfoByName(dictionary_name)
    for _, ifo in ipairs(available_ifos) do
        if ifo.name == dictionary_name then
            return ifo
        end
    end

    return nil
end

local function tidyMarkup(results)
    local cdata_tag = "<!%[CDATA%[(.-)%]%]>"
    local format_escape = "&[29Ib%+]{(.-)}"
    for _, result in ipairs(results) do
        local ifo = getAvailableIfoByName(result.dict)
        if ifo and ifo.lang then
            result.ifo_lang = ifo.lang
        end
        if ifo and ifo.is_html then
            result.is_html = ifo.is_html
            result.css = ifo.css
            if ifo.fix_html_func then
                local dict_path = util.splitFilePathName(ifo.file)
                local ok, fixed_definition = pcall(ifo.fix_html_func, result.definition, dict_path)
                if ok then
                    result.definition = fixed_definition
                else
                    logger.warn("Dict's user provided funcion failed:", fixed_definition)
                end
            end
        else
            local def = result.definition
            -- preserve the <br> tag for line break
            def = def:gsub("<[bB][rR] ?/?>", "\n")
            -- parse CDATA text in XML
            if def:find(cdata_tag) then
                def = def:gsub(cdata_tag, "%1")
                -- ignore format strings
                while def:find(format_escape) do
                    def = def:gsub(format_escape, "%1")
                end
            end
            -- convert any htmlentities (&gt;, &quot;...)
            def = util.htmlEntitiesToUtf8(def)
            -- ignore all markup tags
            def = def:gsub("%b<>", "")
            -- strip all leading empty lines/spaces
            def = def:gsub("^%s+", "")
            result.definition = def
        end
    end
    return results
end

function ReaderDictionary:cleanSelection(text, is_sane)
    -- Will be used by ReaderWikipedia too
    if not text then
        return ""
    end
    -- crengine does now a much better job at finding word boundaries, but
    -- some cleanup is still needed for selection we get from other engines
    -- (example: pdf selection "qu’autrefois," will be cleaned to "autrefois")
    --
    -- Replace no-break space with regular space
    text = text:gsub("\u{00A0}", ' ')
    -- Trim any space at start or end
    text = text:gsub("^%s+", "")
    text = text:gsub("%s+$", "")
    if not is_sane then
        -- Replace extended quote (included in the general puncturation range)
        -- with plain ascii quote (for french words like "aujourd’hui")
        text = text:gsub("\u{2019}", "'") -- Right single quotation mark
        -- Strip punctuation characters around selection
        text = util.stripPunctuation(text)
        -- Strip some common english grammatical construct
        text = text:gsub("'s$", '') -- english possessive
        -- Strip some common french grammatical constructs
        text = text:gsub("^[LSDMNTlsdmnt]'", '') -- french l' s' t'...
        text = text:gsub("^[Qq][Uu]'", '') -- french qu'
        -- There may be a need to remove some (all?) diacritical marks
        -- https://en.wikipedia.org/wiki/Combining_character#Unicode_ranges
        -- see discussion at https://github.com/koreader/koreader/issues/1649
        -- Commented for now, will have to be checked by people who read
        -- languages and texts that use them.
        -- text = text:gsub("\204[\128-\191]", '') -- U+0300 to U+033F
        -- text = text:gsub("\205[\128-\175]", '') -- U+0340 to U+036F
        -- Trim any space now at start or end after above changes
        text = text:gsub("^%s+", "")
        text = text:gsub("%s+$", "")
    end
    return text
end

function ReaderDictionary:showLookupInfo(word, show_delay)
    local text = T(self.lookup_msg, word)
    self.lookup_progress_msg = InfoMessage:new{
        text = text,
        show_delay = show_delay,
    }
    UIManager:show(self.lookup_progress_msg)
end

function ReaderDictionary:dismissLookupInfo()
    if self.lookup_progress_msg then
        UIManager:close(self.lookup_progress_msg)
    end
    self.lookup_progress_msg = nil
end

function ReaderDictionary:onShowDictionaryLookup()
    self.dictionary_lookup_dialog = InputDialog:new{
        title = _("Enter a word or phrase to look up"),
        input = "",
        input_type = "text",
        buttons = {
            {
                {
                    text = _("Cancel"),
                    id = "close",
                    callback = function()
                        UIManager:close(self.dictionary_lookup_dialog)
                    end,
                },
                {
                    text = _("Search dictionary"),
                    is_enter_default = true,
                    callback = function()
                        if self.dictionary_lookup_dialog:getInputText() == "" then return end
                        UIManager:close(self.dictionary_lookup_dialog)
                        -- Trust that input text does not need any cleaning (allows querying for "-suffix")
                        self:onLookupWord(self.dictionary_lookup_dialog:getInputText(), true)
                    end,
                },
            }
        },
    }
    UIManager:show(self.dictionary_lookup_dialog)
    self.dictionary_lookup_dialog:onShowKeyboard()
    return true
end

function ReaderDictionary:rawSdcv(words, dict_names, fuzzy_search, lookup_progress_msg)
    -- Allow for two sdcv calls : one in the classic data/dict, and
    -- another one in data/dict_ext if it exists
    -- We could put in data/dict_ext dictionaries with a great number of words
    -- but poor definitions as a fall back. If these were in data/dict,
    -- they would prevent fuzzy searches in other dictories with better
    -- definitions, and masks such results. This way, we can get both.
    local dict_dirs = {self.data_dir}
    local dict_ext = self.data_dir.."_ext"
    if lfs.attributes(dict_ext, "mode") == "directory" then
        table.insert(dict_dirs, dict_ext)
    end
    -- early exit if no dictionaries
    if dictDirsEmpty(dict_dirs) then
        return false, nil
    end
    local all_results = {}
    local lookup_cancelled = false
    for _, dict_dir in ipairs(dict_dirs) do
        if lookup_cancelled then
            break -- don't do any more lookup on additional dict_dirs
        end

        local args = {"./sdcv", "--utf8-input", "--utf8-output", "--json-output", "--non-interactive", "--data-dir", dict_dir}
        if not fuzzy_search then
            table.insert(args, "--exact-search")
        end
        if dict_names then
            for _, opt in pairs(dict_names) do
                table.insert(args, "-u")
                table.insert(args, opt)
            end
        end
        table.insert(args, "--") -- prevent words starting with a "-" to be interpreted as a sdcv option
        util.arrayAppend(args, words)

        local cmd = util.shell_escape(args)
        -- cmd = "sleep 7 ; " .. cmd     -- uncomment to simulate long lookup time

        -- Some sdcv lookups, when using fuzzy search with many dictionaries
        -- and a really bad selected text, can take up to 10 seconds.
        -- It is nice to be able to cancel it when noticing wrong text was
        -- selected.
        -- Because sdcv starts outputing its output only at the end when it has
        -- done its work, we can use Trapper:dismissablePopen() to cancel it as
        -- long as we are waiting for output.
        -- When fuzzy search is enabled, we have a lookup_progress_msg that can
        -- be used to catch a tap and trigger cancellation.
        -- When fuzzy search is disabled, we provide false instead so an
        -- invisible non-event-forwarding TrapWidget is used to catch a tap
        -- and trigger cancellation (invisible so there's no need for repaint
        -- and refresh with the usually fast non-fuzzy search lookups).
        -- We must ensure we will have some output to be readable (if no
        -- definition found, sdcv will output some message on stderr, and
        -- let stdout empty) by appending an "echo":
        cmd = cmd .. "; echo"
        -- NOTE: Bionic doesn't support rpath, but does honor LD_LIBRARY_PATH...
        --       Give it a shove so it can actually find the STL.
        if Device:isAndroid() then
            C.setenv("LD_LIBRARY_PATH", "./libs", 1)
        end
        local completed, results_str = Trapper:dismissablePopen(cmd, lookup_progress_msg)
        if Device:isAndroid() then
            -- NOTE: It's unset by default, so this is perfectly fine.
            C.unsetenv("LD_LIBRARY_PATH")
        end
        lookup_cancelled = not completed
        if results_str and results_str ~= "\n" then -- \n is when lookup was cancelled
            -- sdcv can return multiple results if we passed multiple words to
            -- the cmdline. In this case, the lookup results for each word are
            -- newline separated. The JSON output doesn't contain raw newlines
            -- so it's safe to split. Ideally luajson would support jsonl but
            -- unfortunately it doesn't and it also seems to decode the last
            -- object rather than the first one if there are multiple.
            local result_word_idx = 0
            for _, entry_str in ipairs(util.splitToArray(results_str, "\n")) do
                result_word_idx = result_word_idx + 1
                local ok, results = pcall(JSON.decode, entry_str)
                if not ok or not results then
                    logger.warn("JSON data cannot be decoded", results)
                    -- Need to insert an empty table so that the word entries
                    -- match up to the result entries (so that callers can
                    -- batch lookups to reduce the cost of bulk lookups while
                    -- still being able to figure out which lookup came from
                    -- which word).
                    results = {}
                end
                if all_results[result_word_idx] then
                    util.arrayAppend(all_results[result_word_idx], results)
                else
                    table.insert(all_results, results)
                end
            end
            if result_word_idx ~= #words then
                logger.warn("sdcv returned a different number of results than the number of words")
            end
        end
    end
    return lookup_cancelled, all_results
end

function ReaderDictionary:startSdcv(word, dict_names, fuzzy_search)
    local words = {word}

    if self.ui.languagesupport and self.ui.languagesupport:hasActiveLanguagePlugins() then
        -- Get any other candidates from any language-specific plugins we have.
        -- We prefer the originally selected word first (in case there is a
        -- dictionary entry for whatever text the user selected).
        local candidates = self.ui.languagesupport:extraDictionaryFormCandidates(word)
        if candidates then
            util.arrayAppend(words, candidates)
        end
    end

    -- If every word contains a CJK character, every word candidate is
    -- (probably) a CJK word. We don't want fuzzy searching in this case
    -- because sdcv cannot handle CJK text properly when fuzzy searching (with
    -- Japanese, it returns hundreds of useless results).
    local shouldnt_fuzzy_search = true
    for _, w in ipairs(words) do
        if not util.hasCJKChar(w) then
            shouldnt_fuzzy_search = false
            break
        end
    end
    if shouldnt_fuzzy_search then
        logger.dbg("disabling fuzzy searching for all-CJK word search:", words)
        fuzzy_search = false
    end

    local lookup_cancelled, results = self:rawSdcv(words, dict_names, fuzzy_search, self.lookup_progress_msg or false)
    if results == nil then -- no dictionaries found
        return {
            {
                dict = "",
                word = word,
                definition = _([[No dictionaries installed. Please search for "Dictionary support" in the KOReader Wiki to get more information about installing new dictionaries.]]),
            }
        }
    else -- flatten any possible results
        local flat_results = {}
        local seen_results = {}
        -- Flatten the array, removing any duplicates we may have gotten (sdcv
        -- may do multiple queries, in fixed mode then in fuzzy mode, and the
        -- language-specific plugin may have also returned multiple equivalent
        -- results).
        local h
        for _, term_results in ipairs(results) do
            for _, r in ipairs(term_results) do
                h = r.dict .. r.word .. r.definition
                if seen_results[h] == nil then
                    table.insert(flat_results, r)
                    seen_results[h] = true
                end
            end
        end
        results = flat_results
    end
    if #results == 0 then -- no results found
        -- dummy results
        results = {
            {
                dict = _("Not available"),
                word = word,
                definition = lookup_cancelled and _("Dictionary lookup interrupted.") or _("No results."),
                no_result = true,
                lookup_cancelled = lookup_cancelled,
            }
        }
    end
    if lookup_cancelled then
        -- Also put this as a k/v into the results array: when using dict_ext,
        -- we may get results from the 1st lookup, and have interrupted the 2nd.
        results.lookup_cancelled = true
    end
    return results
end

function ReaderDictionary:stardictLookup(word, dict_names, fuzzy_search, boxes, link, tweak_buttons_func)
    if word == "" then
        return
    end

    local book_title = self.ui.doc_props and self.ui.doc_props.display_title or _("Dictionary lookup")

    -- Event for plugin to catch lookup with book title
    self.ui:handleEvent(Event:new("WordLookedUp", word, book_title))
    if not self.disable_lookup_history then
        lookup_history:addTableItem("lookup_history", {
            book_title = book_title,
            time = os.time(),
            word = word,
        })
    end

    if Device:canExternalDictLookup() and G_reader_settings:isTrue("external_dict_lookup") then
        Device:doExternalDictLookup(word, G_reader_settings:readSetting("external_dict_lookup_method"), function()
            if self.highlight then
                local clear_id = self.highlight:getClearId()
                UIManager:scheduleIn(0.5, function()
                    self.highlight:clear(clear_id)
                end)
            end
        end)
        return
    end

    -- If the user disabled all the dictionaries, go away.
    if dict_names and #dict_names == 0 then
        -- Dummy result
        local nope = {
            {
                dict = _("Not available"),
                word = word,
                definition = _("There are no enabled dictionaries.\nPlease check the 'Dictionary settings' menu."),
                no_result = true,
                lookup_cancelled = false,
            }
        }
        self:showDict(word, nope, boxes, link)
        return
    end

    self:showLookupInfo(word, self.lookup_msg_delay)

    self._lookup_start_time = UIManager:getTime()
    local results = self:startSdcv(word, dict_names, fuzzy_search)
    if results and results.lookup_cancelled
        and (time.now() - self._lookup_start_time) <= self.quick_dismiss_before_delay then
        -- If interrupted quickly just after launch, don't display anything
        -- (this might help avoiding refreshes and the need to dismiss
        -- after accidental long-press when holding a device).
        if self.highlight then
            self.highlight:clear()
        end
        return
    end

    self:showDict(word, tidyMarkup(results), boxes, link, tweak_buttons_func)
end

function ReaderDictionary:showDict(word, results, boxes, link, tweak_buttons_func)
    if results and results[1] then
        logger.dbg("showing quick lookup window", #DictQuickLookup.window_list+1, ":", word, results)
        self.dict_window = DictQuickLookup:new{
            ui = self.ui,
            highlight = self.highlight,
            tweak_buttons_func = tweak_buttons_func,
            dialog = self.dialog,
            -- original lookup word
            word = word,
            -- selected link, if any
            selected_link = link,
            results = results,
            word_boxes = boxes,
            preferred_dictionaries = self.preferred_dictionaries,
            -- differentiate between dict and wiki
            is_wiki = self.is_wiki,
            refresh_callback = function()
                if self.view then
                    -- update info in footer (time, battery, etc)
                    self.view.footer:onUpdateFooter()
                end
            end,
            html_dictionary_link_tapped_callback = function(dictionary, html_link)
                self:onHtmlDictionaryLinkTapped(dictionary, html_link)
            end,
        }
        if self.lookup_progress_msg then
            -- If we have a lookup InfoMessage that ended up being displayed, make
            -- it *not* refresh on close if it is hidden by our DictQuickLookup
            -- to avoid refreshes competition and possible glitches
            local msg_dimen = self.lookup_progress_msg:getVisibleArea()
            if msg_dimen then -- not invisible
                local dict_dimen = self.dict_window:getInitialVisibleArea()
                if dict_dimen and dict_dimen:contains(msg_dimen) then
                    self.lookup_progress_msg.no_refresh_on_close = true
                end
            end
        end
    end

    self:dismissLookupInfo()
    if results and results[1] then
        UIManager:show(self.dict_window)
        if not results.lookup_cancelled and self._lookup_start_time
            and (time.now() - self._lookup_start_time) > self.quick_dismiss_before_delay then
            -- If the search took more than a few seconds to be done, discard
            -- queued and upcoming input events to avoid a voluntary dismissal
            -- (because the user felt the result would not come) to kill the
            -- result that finally came and is about to be displayed
            Input:inhibitInputUntil(true)
        end
    end
end

function ReaderDictionary:showDownload(downloadable_dicts)
    local kv_pairs = {}
    for dummy, dict in ipairs(downloadable_dicts) do
        table.insert(kv_pairs, {dict.name, "",
            callback = function()
                local connect_callback = function()
                    self:downloadDictionaryPrep(dict)
                end
                NetworkMgr:runWhenOnline(connect_callback)
            end})
        local lang
        if dict.lang_in == dict.lang_out then
            lang = string.format("    %s", dict.lang_in)
        else
            lang = string.format("    %s–%s", dict.lang_in, dict.lang_out)
        end
        table.insert(kv_pairs, {lang, ""})
        table.insert(kv_pairs, {"    ".._("License"), dict.license})
        table.insert(kv_pairs, {"    ".._("Entries"), dict.entries, separator = true})
    end
    self.download_window = KeyValuePage:new{
        title = _("Tap dictionary name to download"),
        kv_pairs = kv_pairs,
    }
    UIManager:show(self.download_window)
end

function ReaderDictionary:downloadDictionaryPrep(dict, size)
    local dummy, filename = util.splitFilePathName(dict.url)
    local download_location = string.format("%s/%s", self.data_dir, filename)

    if lfs.attributes(download_location) then
        UIManager:show(ConfirmBox:new{
            text =  _("File already exists. Overwrite?"),
            ok_text =  _("Overwrite"),
            ok_callback = function()
                self:downloadDictionary(dict, download_location)
            end,
        })
    else
        self:downloadDictionary(dict, download_location)
    end
end

function ReaderDictionary:downloadDictionary(dict, download_location, continue)
    continue = continue or false
    local socket = require("socket")
    local socketutil = require("socketutil")
    local http = socket.http
    local ltn12 = require("ltn12")

    if not continue then
        local file_size
        -- Skip body & code args
        socketutil:set_timeout()
        local headers = socket.skip(2, http.request{
            method  = "HEAD",
            url     = dict.url,
            --redirect = true,
        })
        socketutil:reset_timeout()
        --logger.dbg(headers)
        file_size = headers and headers["content-length"]

        if file_size then
            UIManager:show(ConfirmBox:new{
                text =  T(_("Dictionary filesize is %1 (%2 bytes). Continue with download?"), util.getFriendlySize(file_size), util.getFormattedSize(file_size)),
                ok_text =  _("Download"),
                ok_callback = function()
                    -- call ourselves with continue = true
                    self:downloadDictionary(dict, download_location, true)
                end,
            })
            return
        else
            logger.dbg("ReaderDictionary: Request failed; response headers:", headers)
            UIManager:show(InfoMessage:new{
                text = _("Failed to fetch dictionary. Are you online?"),
                --timeout = 3,
            })
            return false
        end
    else
        UIManager:nextTick(function()
            UIManager:show(InfoMessage:new{
                text = _("Downloading…"),
                timeout = 3,
            })
        end)
    end

    socketutil:set_timeout(socketutil.FILE_BLOCK_TIMEOUT, socketutil.FILE_TOTAL_TIMEOUT)
    local code, headers, status = socket.skip(1, http.request{
        url     = dict.url,
        sink    = ltn12.sink.file(io.open(download_location, "w")),
    })
    socketutil:reset_timeout()
    if code == 200 then
        logger.dbg("file downloaded to", download_location)
    else
        logger.dbg("ReaderDictionary: Request failed:", status or code)
        logger.dbg("ReaderDictionary: Response headers:", headers)
        UIManager:show(InfoMessage:new{
            text = _("Could not save file to:\n") .. BD.filepath(download_location),
            --timeout = 3,
        })
        return false
    end

    -- stable target directory is needed so we can look through the folder later
    local dict_path = self.data_dir .. "/" .. dict.name
    util.makePath(dict_path)
    local ok, error = Device:unpackArchive(download_location, dict_path, true)

    if ok then
        if dict.ifo_lang then
            self:extendIfoWithLanguage(dict_path, dict.ifo_lang)
        end
        available_ifos = false
        self:init()
        UIManager:show(InfoMessage:new{
            text = _("Dictionary downloaded:\n") .. dict.name,
        })
        return true
    else
        UIManager:show(InfoMessage:new{
            text = _("Dictionary failed to download:\n") .. string.format("%s\n%s", dict.name, error),
        })
        return false
    end
end

function ReaderDictionary:extendIfoWithLanguage(dictionary_location, ifo_lang)
    local function cb(path, filename)
        if util.getFileNameSuffix(filename) == "ifo" then
            local fmt_string = "lang=%s"
            local f = io.open(path, "a+")
            if f then
                local ifo = f:read("a*")
                if ifo[#ifo] ~= "\n" then
                    fmt_string = "\n" .. fmt_string
                end
                f:write(fmt_string:format(ifo_lang))
                f:close()
            end
        end
    end
    util.findFiles(dictionary_location, cb)
end

function ReaderDictionary:onReadSettings(config)
    self.preferred_dictionaries = config:readSetting("preferred_dictionaries") or {}
    if #self.preferred_dictionaries == 0 then
        -- Legacy setting, when only one dict could be set as default/first to show
        local default_dictionary = config:readSetting("default_dictionary")
        if default_dictionary then
            table.insert(self.preferred_dictionaries, default_dictionary)
            config:delSetting("default_dictionary")
        end
    end
    if #self.preferred_dictionaries > 0 then
        self:updateSdcvDictNamesOptions()
    end
    if config:has("disable_fuzzy_search") then
        self.disable_fuzzy_search = config:isTrue("disable_fuzzy_search")
    else
        self.disable_fuzzy_search = G_reader_settings:isTrue("disable_fuzzy_search")
    end
end

function ReaderDictionary:onSaveSettings()
    if self.ui.doc_settings then
        self.ui.doc_settings:saveSetting("preferred_dictionaries", self.preferred_dictionaries)
    end
end

function ReaderDictionary:onTogglePreferredDict(dict)
    if not self.preferred_dictionaries then
        -- Invoked from FileManager: no preferred dict to manage
        return true
    end
    local removed = false
    for idx, name in ipairs(self.preferred_dictionaries) do
        if dict == name then
            removed = true
            table.remove(self.preferred_dictionaries, idx)
            break
        end
    end
    if not removed then -- insert it as first
        table.insert(self.preferred_dictionaries, 1, dict)
    end
    UIManager:show(InfoMessage:new{
        text = removed and T(_("%1 is no longer a preferred dictionary for this document."), dict)
                        or T(_("%1 is now the preferred dictionary for this document."), dict),
        timeout = 2,
    })
    self:updateSdcvDictNamesOptions()
    return true
end

function ReaderDictionary:toggleFuzzyDefault(touchmenu_instance)
    local disable_fuzzy_search = G_reader_settings:isTrue("disable_fuzzy_search")
    UIManager:show(MultiConfirmBox:new{
        text = T(
            disable_fuzzy_search
            and _([[
Would you like to enable or disable fuzzy search by default?

Fuzzy search can match epuisante, épuisante and épuisantes to épuisant, even if only the latter has an entry in the dictionary. It can be disabled to improve performance, but it might be worthwhile to look into disabling unneeded dictionaries before disabling fuzzy search.

The current default (★) is disabled.]])
            or _([[
Would you like to enable or disable fuzzy search by default?

Fuzzy search can match epuisante, épuisante and épuisantes to épuisant, even if only the latter has an entry in the dictionary. It can be disabled to improve performance, but it might be worthwhile to look into disabling unneeded dictionaries before disabling fuzzy search.

The current default (★) is enabled.]])
        ),
        choice1_text_func =  function()
            return disable_fuzzy_search and _("Disable (★)") or _("Disable")
        end,
        choice1_callback = function()
            G_reader_settings:makeTrue("disable_fuzzy_search")
            touchmenu_instance:updateItems()
        end,
        choice2_text_func = function()
            return disable_fuzzy_search and _("Enable") or _("Enable (★)")
        end,
        choice2_callback = function()
            G_reader_settings:makeFalse("disable_fuzzy_search")
            touchmenu_instance:updateItems()
        end,
    })
end

return ReaderDictionary
