local ConfirmBox = require("ui/widget/confirmbox")
local DataStorage = require("datastorage")
local Device = require("device")
local DocSettings = require("docsettings")
local InfoMessage = require("ui/widget/infomessage")
local MultiInputDialog = require("ui/widget/multiinputdialog")
local NetworkMgr = require("ui/network/manager")
local ReadHistory = require("readhistory")
local SQ3 = require("lua-ljsqlite3/init")
local T = require("ffi/util").template
local UIManager = require("ui/uimanager")
local WidgetContainer = require("ui/widget/container/widgetcontainer")
local _ = require("gettext")
local logger = require("logger")
local md5 = require("ffi/sha2").md5
local random = require("random")

------------------------------------------
------------ Helper Functions ------------
------------------------------------------
local function dump(o)
    if type(o) == 'table' then
        local s = '{ '
        for k, v in pairs(o) do
            if type(k) ~= 'number' then k = '"' .. k .. '"' end
            s = s .. '[' .. k .. '] = ' .. dump(v) .. ','
        end
        return s .. '} '
    else
        return tostring(o)
    end
end

local function validate(entry)
    if not entry then return false end
    if type(entry) == "string" then
        if entry == "" or not entry:match("%S") then return false end
    end
    return true
end

local function validateUser(user, pass)
    local error_message = nil
    local user_ok = validate(user)
    local pass_ok = validate(pass)
    if not user_ok and not pass_ok then
        error_message = _("invalid username and password")
    elseif not user_ok then
        error_message = _("invalid username")
    elseif not pass_ok then
        error_message = _("invalid password")
    end

    if not error_message then
        return user_ok and pass_ok
    else
        return user_ok and pass_ok, error_message
    end
end

------------------------------------------
-------------- Plugin Start --------------
------------------------------------------
local MERGE_SETTINGS_IN = "IN"
local MERGE_SETTINGS_OUT = "OUT"

local STATISTICS_ACTIVITY_SINCE_QUERY = [[
    SELECT
	b.md5 AS document,
	psd.start_time AS start_time,
	psd.duration AS duration,
	psd.page AS current_page,
	psd.total_pages 
    FROM page_stat_data AS psd
    JOIN book AS b 
    ON b.id = psd.id_book
    WHERE start_time > %d
    ORDER BY start_time ASC LIMIT 5000;
]]

local STATISTICS_BOOK_QUERY = [[
    SELECT
	md5,
	title,
	authors,
	series,
	language
      FROM book;
]]

local BOOKINFO_BOOK_QUERY = [[
    SELECT
	(directory || filename) as filepath,
	title,
	authors,
	series,
	series_index,
	language,
	description
    FROM bookinfo;
]]

-- Validate Device ID Exists
if G_reader_settings:hasNot("device_id") then
    G_reader_settings:saveSetting("device_id", random.uuid())
end

-- Define DB Location
local statistics_db = DataStorage:getSettingsDir() .. "/statistics.sqlite3"
local bookinfo_db = DataStorage:getSettingsDir() .. "/bookinfo_cache.sqlite3"

local SyncNinja = WidgetContainer:extend{
    name = "syncninja",
    settings = nil,
    is_doc_only = false
}

SyncNinja.default_settings = {
    server = nil,
    username = nil,
    password = nil,
    sync_frequency = 30,
    sync_activity = true,
    sync_documents = true,
    sync_document_files = true
}

function SyncNinja:init()
    logger.dbg("SyncNinja: init")

    -- Instance Specific (Non Interactive)
    self.periodic_push_task = function() self:performSync(false) end

    -- Load Settings
    self.device_id = G_reader_settings:readSetting("device_id")
    self.settings = G_reader_settings:readSetting("syncninja",
                                                  self.default_settings)

    -- Register Menu Items
    self.ui.menu:registerToMainMenu(self)

    -- Initial Periodic Push Schedule (5 Minutes)
    self:schedulePeriodicPush(5)
end

------------------------------------------
-------------- UX Functions --------------
------------------------------------------
function SyncNinja:addToMainMenu(menu_items)
    logger.dbg("SyncNinja: addToMainMenu")
    menu_items.syncninja = {
        text = _("Sync Ninja"),
        sorting_hint = "tools",
        sub_item_table = {
            {
                text = _("Sync Server"),
                keep_menu_open = true,
                tap_input_func = function(menu)
                    return {
                        title = _("Sync server address"),
                        input = self.settings.server or "https://",
                        type = "text",
                        callback = function(input)
                            self.settings.server = input ~= "" and input or nil
                            if menu then
                                menu:updateItems()
                            end
                        end
                    }
                end
            }, {
                text_func = function()
                    return self.settings.password and (_("Logout")) or
                               _("Register") .. " / " .. _("Login")
                end,
                enabled_func = function()
                    return self.settings.server ~= nil
                end,
                keep_menu_open = true,
                callback_func = function()
                    if self.settings.password then
                        return function(menu)
                            self:logoutUI(menu)
                        end
                    else
                        return function(menu)
                            self:loginUI(menu)
                        end
                    end
                end
            }, {
                text = _("Manual Sync"),
                keep_menu_open = true,
                enabled_func = function()
                    return self.settings.password ~= nil and
                               self.settings.username ~= nil and
                               self.settings.server ~= nil
                end,
                callback = function()
                    UIManager:unschedule(self.performSync)
                    self:performSync(true) -- Interactive
                end
            }, {
                text = _("KOSync Auth Merge"),
                sub_item_table = {
                    {
                        text = _("KOSync Merge In"),
                        keep_menu_open = true,
                        callback = function()
                            self:mergeKOSync(MERGE_SETTINGS_IN)
                        end
                    }, {
                        text = _("KOSync Merge Out"),
                        keep_menu_open = true,
                        callback = function()
                            self:mergeKOSync(MERGE_SETTINGS_OUT)
                        end
                    }

                },
                separator = true
            }, {
                text_func = function()
                    return T(_("Sync Frequency (%1 Minutes)"),
                             self.settings.sync_frequency or 30)
                end,
                keep_menu_open = true,
                callback = function(touchmenu_instance)
                    local SpinWidget = require("ui/widget/spinwidget")
                    local items = SpinWidget:new{
                        text = _(
                            [[This value determines the cadence at which the syncs will be performed.
If set to 0, periodic sync will be disabled.]]),
                        value = self.settings.sync_frequency or 30,
                        value_min = 0,
                        value_max = 1440,
                        value_step = 30,
                        value_hold_step = 60,
                        ok_text = _("Set"),
                        title_text = _("Minutes between syncs"),
                        default_value = 30,
                        callback = function(spin)
                            self.settings.sync_frequency = spin.value > 0 and
                                                               spin.value or 30
                            if touchmenu_instance then
                                touchmenu_instance:updateItems()
                            end
                            self:schedulePeriodicPush()
                        end
                    }
                    UIManager:show(items)
                end
            }, {
                text_func = function()
                    return T(_("Sync Activity (%1)"), self.settings
                                 .sync_activity == true and (_("Enabled")) or
                                 (_("Disabled")))
                end,
                sub_item_table = {
                    {
                        text = _("Enabled"),
                        checked_func = function()
                            return self.settings.sync_activity == true
                        end,
                        callback = function()
                            self.settings.sync_activity = true
                        end
                    }, {
                        text = _("Disabled"),
                        checked_func = function()
                            return self.settings.sync_activity ~= true
                        end,
                        callback = function()
                            self.settings.sync_activity = false
                        end
                    }
                }
            }, {
                text_func = function()
                    return T(_("Sync Documents (%1)"), self.settings
                                 .sync_documents == true and (_("Enabled")) or
                                 (_("Disabled")))
                end,
                sub_item_table = {
                    {
                        text = _("Enabled"),
                        checked_func = function()
                            return self.settings.sync_documents == true
                        end,
                        callback = function()
                            self.settings.sync_documents = true
                        end
                    }, {
                        text = _("Disabled"),
                        checked_func = function()
                            return self.settings.sync_documents ~= true
                        end,
                        callback = function()
                            self.settings.sync_documents = false
                        end
                    }
                }
            }, {
                text_func = function()
                    return T(_("Sync Document Files (%1)"),
                             self.settings.sync_documents == true and
                                 self.settings.sync_document_files == true and
                                 (_("Enabled")) or (_("Disabled")))
                end,
                enabled_func = function()
                    return self.settings.sync_documents == true
                end,
                sub_item_table = {
                    {
                        text = _("Enabled"),
                        checked_func = function()
                            return self.settings.sync_document_files == true
                        end,
                        callback = function()
                            self.settings.sync_document_files = true
                        end
                    }, {
                        text = _("Disabled"),
                        checked_func = function()
                            return self.settings.sync_document_files ~= true
                        end,
                        callback = function()
                            self.settings.sync_document_files = false
                        end
                    }
                }
            }
        }
    }
end

function SyncNinja:loginUI(menu)
    logger.dbg("SyncNinja: loginUI")
    if NetworkMgr:willRerunWhenOnline(function() self:loginUI(menu) end) then
        return
    end

    local dialog
    dialog = MultiInputDialog:new{
        title = _("Register/login to SyncNinja server"),
        fields = {
            {text = self.settings.username, hint = "username"},
            {hint = "password", text_type = "password"}
        },
        buttons = {
            {
                {
                    text = _("Cancel"),
                    id = "close",
                    callback = function()
                        UIManager:close(dialog)
                    end
                }, {
                    text = _("Login"),
                    callback = function()
                        local username, password = unpack(dialog:getFields())
                        local ok, err = validateUser(username, password)
                        if not ok then
                            UIManager:show(InfoMessage:new{
                                text = T(_("Cannot login: %1"), err),
                                timeout = 2
                            })
                        else
                            UIManager:close(dialog)
                            UIManager:scheduleIn(0.5, function()
                                self:userLogin(username, password, menu)
                            end)
                            UIManager:show(InfoMessage:new{
                                text = _("Logging in. Please wait…"),
                                timeout = 1
                            })
                        end
                    end
                }, {
                    text = _("Register"),
                    callback = function()
                        local username, password = unpack(dialog:getFields())
                        local ok, err = validateUser(username, password)
                        if not ok then
                            UIManager:show(InfoMessage:new{
                                text = T(_("Cannot register: %1"), err),
                                timeout = 2
                            })
                        else
                            UIManager:close(dialog)
                            UIManager:scheduleIn(0.5, function()
                                self:userRegister(username, password, menu)
                            end)
                            UIManager:show(InfoMessage:new{
                                text = _("Registering. Please wait…"),
                                timeout = 1
                            })
                        end
                    end
                }
            }
        }
    }
    UIManager:show(dialog)
    dialog:onShowKeyboard()
end

function SyncNinja:logoutUI(menu)
    logger.dbg("SyncNinja: logoutUI")
    self.settings.username = nil
    self.settings.password = nil
    if menu then menu:updateItems() end
    UIManager:unschedule(self.periodic_push_task)
end

function SyncNinja:mergeKOSync(direction)
    logger.dbg("SyncNinja: mergeKOSync")
    local kosync_settings = G_reader_settings:readSetting("kosync")
    if kosync_settings == nil then return end

    if direction == MERGE_SETTINGS_OUT then
        -- Validate Configured
        if not self.settings.server or not self.settings.username or
            not self.settings.password then
            return UIManager:show(InfoMessage:new{
                text = _("Error: SyncNinja not configured")
            })
        end

        kosync_settings.custom_server = self.settings.server ..
                                            (self.settings.server:sub(-#"/") ==
                                                "/" and "api/ko" or "/api/ko")
        kosync_settings.username = self.settings.username
        kosync_settings.userkey = self.settings.password

        UIManager:show(InfoMessage:new{text = _("Synced to KOSync")})
    elseif direction == MERGE_SETTINGS_IN then
        -- Validate Configured
        if not kosync_settings.custom_server or not kosync_settings.username or
            not kosync_settings.userkey then
            return UIManager:show(InfoMessage:new{
                text = _("Error: KOSync not configured")
            })
        end

        -- Validate Compatible Server
        if kosync_settings.custom_server:sub(-#"/api/ko") ~= "/api/ko" and
            kosync_settings.custom_server:sub(-#"/api/ko/") ~= "/api/ko/" then
            return UIManager:show(InfoMessage:new{
                text = _("Error: Configured KOSync server not compatible")
            })
        end

        self.settings.server = string.gsub(kosync_settings.custom_server,
                                           "/api/ko/?$", "")
        self.settings.username = kosync_settings.username
        self.settings.password = kosync_settings.userkey

        UIManager:show(InfoMessage:new{text = _("Synced from KOSync")})
    end
end

------------------------------------------
------------- Login Functions ------------
------------------------------------------
function SyncNinja:userLogin(username, password, menu)
    logger.dbg("SyncNinja: userLogin")
    if not self.settings.server then return end

    local SyncNinjaClient = require("SyncNinjaClient")
    local client = SyncNinjaClient:new{
        custom_url = self.settings.server,
        service_spec = self.path .. "/api.json"
    }
    Device:setIgnoreInput(true)
    local userkey = md5(password)
    local ok, status, body = pcall(client.authorize, client, username, userkey)
    if not ok then
        if status then
            UIManager:show(InfoMessage:new{
                text = _("An error occurred while logging in:") .. "\n" ..
                    status
            })
        else
            UIManager:show(InfoMessage:new{
                text = _("An unknown error occurred while logging in.")
            })
        end
        Device:setIgnoreInput(false)
        return
    elseif status then
        self.settings.username = username
        self.settings.password = userkey
        if menu then menu:updateItems() end
        UIManager:show(InfoMessage:new{
            text = _("Logged in to KOReader server.")
        })

        self:schedulePeriodicPush(0)
    else
        logger.dbg("SyncNinja: userLogin Error:", dump(body))
    end
    Device:setIgnoreInput(false)
end

function SyncNinja:userRegister(username, password, menu)
    logger.dbg("SyncNinja: userRegister")
    if not self.settings.server then return end

    local SyncNinjaClient = require("SyncNinjaClient")
    local client = SyncNinjaClient:new{
        custom_url = self.settings.server,
        service_spec = self.path .. "/api.json"
    }
    -- on Android to avoid ANR (no-op on other platforms)
    Device:setIgnoreInput(true)
    local userkey = md5(password)
    local ok, status, body = pcall(client.register, client, username, userkey)
    if not ok then
        if status then
            UIManager:show(InfoMessage:new{
                text = _("An error occurred while registering:") .. "\n" ..
                    status
            })
        else
            UIManager:show(InfoMessage:new{
                text = _("An unknown error occurred while registering.")
            })
        end
    elseif status then
        self.settings.username = username
        self.settings.password = userkey
        if menu then menu:updateItems() end
        UIManager:show(InfoMessage:new{
            text = _("Registered to KOReader server.")
        })

        self:schedulePeriodicPush(0)
    else
        UIManager:show(InfoMessage:new{
            text = body and body.message or _("Unknown server error")
        })
    end
    Device:setIgnoreInput(false)
end

------------------------------------------
------------- Sync Functions -------------
------------------------------------------
function SyncNinja:schedulePeriodicPush(minutes)
    logger.dbg("SyncNinja: schedulePeriodicPush")

    -- Validate Configured
    if not self.settings then return end
    if not self.settings.username then return end
    if not self.settings.password then return end
    if not self.settings.server then return end

    -- Unschedule & Schedule
    local sync_frequency = minutes or self.settings.sync_frequency or 30
    UIManager:unschedule(self.periodic_push_task)
    UIManager:scheduleIn(60 * sync_frequency, self.periodic_push_task)
end

function SyncNinja:performSync(interactive)
    logger.dbg("SyncNinja: performSync")

    -- Upload Activity & Check Documents
    self:checkActivity(interactive)
    self:checkDocuments(interactive)

    -- Notify
    if interactive == true then
        UIManager:show(InfoMessage:new{
            text = _("SyncNinja: Manual Sync Initiated"),
            timeout = 3
        })
    end

    -- Schedule Push Again
    self:schedulePeriodicPush()
end

function SyncNinja:checkActivity(interactive)
    logger.dbg("SyncNinja: checkActivity")

    -- Ensure Activity Sync Enabled
    if self.settings.sync_activity ~= true then return end

    -- API Callback Function
    local callback_func = function(ok, body)
        if not ok then
            if interactive == true then
                UIManager:show(InfoMessage:new{
                    text = _("SyncNinja: checkActivity Error"),
                    timeout = 3
                })
            end
            return logger.dbg("SyncNinja: checkActivity Error:", dump(body))
        end

        local last_sync = body.last_sync
        local activity_data = self:getStatisticsActivity(last_sync)

        -- Activity Data Exists
        if not (next(activity_data) == nil) then
            self:uploadActivity(activity_data, interactive)
        end
    end

    -- API Call
    local SyncNinjaClient = require("SyncNinjaClient")
    local client = SyncNinjaClient:new{
        custom_url = self.settings.server,
        service_spec = self.path .. "/api.json"
    }
    local ok, err = pcall(client.check_activity, client, self.settings.username,
                          self.settings.password, self.device_id, callback_func)
end

function SyncNinja:uploadActivity(activity_data, interactive)
    logger.dbg("SyncNinja: uploadActivity")

    -- API Callback Function
    local callback_func = function(ok, body)
        if not ok then
            if interactive == true then
                UIManager:show(InfoMessage:new{
                    text = _("SyncNinja: uploadActivity Error"),
                    timeout = 3
                })
            end
            return logger.dbg("SyncNinja: uploadActivity Error:", dump(body))
        end
    end

    -- API Call
    local SyncNinjaClient = require("SyncNinjaClient")
    local client = SyncNinjaClient:new{
        custom_url = self.settings.server,
        service_spec = self.path .. "/api.json"
    }
    local ok, err = pcall(client.add_activity, client, self.settings.username,
                          self.settings.password, self.device_id, Device.model,
                          activity_data, callback_func)
end

function SyncNinja:checkDocuments(interactive)
    logger.dbg("SyncNinja: checkDocuments")

    -- ensure document sync enabled
    if self.settings.sync_documents ~= true then return end

    -- API Request Data
    local doc_metadata = self:getLocalDocumentMetadata()
    local doc_ids = self:getLocalDocumentIDs(doc_metadata)

    -- API Callback Function
    local callback_func = function(ok, body)
        if not ok then
            if interactive == true then
                UIManager:show(InfoMessage:new{
                    text = _("SyncNinja: checkDocuments Error"),
                    timeout = 3
                })
            end
            return logger.dbg("SyncNinja: checkDocuments Error:", dump(body))
        end

        -- Document Metadata Wanted
        if not (next(body.want_metadata) == nil) then
            local hash_want_metadata = {}
            for _, v in pairs(body.want_metadata) do
                hash_want_metadata[v] = true
            end

            local upload_doc_metadata = {}
            for _, v in pairs(doc_metadata) do
                if hash_want_metadata[v.id] == true then
                    table.insert(upload_doc_metadata, v)
                end
            end

            self:uploadDocumentMetadata(upload_doc_metadata, interactive)
        end

        -- Document Files Wanted
        if not (next(body.want_files) == nil) then
            local hash_want_files = {}
            for _, v in pairs(body.want_files) do
                hash_want_files[v] = true
            end

            local upload_doc_files = {}
            for _, v in pairs(doc_metadata) do
                if hash_want_files[v.id] == true then
                    table.insert(upload_doc_files, v)
                end
            end

            self:uploadDocumentFiles(upload_doc_files, interactive)
        end

        -- Documents Provided
        if not (next(body.give) == nil) then
            self:downloadDocuments(body.give, interactive)
        end
    end

    -- API Call
    local SyncNinjaClient = require("SyncNinjaClient")
    local client = SyncNinjaClient:new{
        custom_url = self.settings.server,
        service_spec = self.path .. "/api.json"
    }
    local ok, err = pcall(client.check_documents, client,
                          self.settings.username, self.settings.password,
                          self.device_id, Device.model, doc_ids, callback_func)
end

function SyncNinja:downloadDocuments(doc_metadata, interactive)
    logger.dbg("SyncNinja: downloadDocuments")

    -- TODO
end

function SyncNinja:uploadDocumentMetadata(doc_metadata, interactive)
    logger.dbg("SyncNinja: uploadDocumentMetadata")

    -- Ensure Document Sync Enabled
    if self.settings.sync_documents ~= true then return end

    -- API Callback Function
    local callback_func = function(ok, body)
        if not ok then
            if interactive == true then
                UIManager:show(InfoMessage:new{
                    text = _("SyncNinja: uploadDocumentMetadata Error"),
                    timeout = 3
                })
            end
            return logger.dbg("SyncNinja: uploadDocumentMetadata Error:",
                              dump(body))
        end
    end

    -- API Client
    local SyncNinjaClient = require("SyncNinjaClient")
    local client = SyncNinjaClient:new{
        custom_url = self.settings.server,
        service_spec = self.path .. "/api.json"
    }

    -- API Initial Metadata
    local ok, err = pcall(client.add_documents, client, self.settings.username,
                          self.settings.password, doc_metadata, callback_func)

end

function SyncNinja:uploadDocumentFiles(doc_metadata, interactive)
    logger.dbg("SyncNinja: uploadDocumentFiles")

    -- Ensure Document File Sync Enabled
    if self.settings.sync_document_files ~= true then return end
    if interactive ~= true then return end

    local callback_func = function(ok, body)
        if not ok then
            UIManager:show(InfoMessage:new{
                text = _("SyncNinja: uploadDocumentFiles Error"),
                timeout = 3
            })
            return logger.dbg("SyncNinja: uploadDocumentFiles Error:",
                              dump(body))
        end
    end

    -- API File Upload
    local confirm_upload_callback = function()
        UIManager:show(InfoMessage:new{
            text = _("Uploading Documents - Please Wait...")
        })

        UIManager:nextTick(function()
            -- API Client
            local SyncNinjaClient = require("SyncNinjaClient")
            local client = SyncNinjaClient:new{
                custom_url = self.settings.server,
                service_spec = self.path .. "/api.json"
            }

            for _, v in pairs(doc_metadata) do
                if v.filepath ~= nil then
                    local ok, err = pcall(client.upload_document, client,
                                          self.settings.username,
                                          self.settings.password, v.id,
                                          v.filepath, callback_func)
                else
                    logger.dbg("SyncNinja: uploadDocumentFiles - no file for:",
                               v.id)
                end
            end

            UIManager:show(InfoMessage:new{
                text = _("Uploading Documents Complete")
            })
        end)
    end

    UIManager:show(ConfirmBox:new{
        text = _("Upload documents? This can take awhile."),
        ok_text = _("Yes"),
        ok_callback = confirm_upload_callback
    })
end

------------------------------------------
------------ Getter Functions ------------
------------------------------------------
function SyncNinja:getLocalDocumentIDs(doc_metadata)
    logger.dbg("SyncNinja: getLocalDocumentIDs")

    local document_ids = {}

    if doc_metadata == nil then
        doc_metadata = self:getLocalDocumentMetadata()
    end

    for _, v in pairs(doc_metadata) do table.insert(document_ids, v.id) end

    return document_ids
end

function SyncNinja:getLocalDocumentMetadata()
    logger.dbg("SyncNinja: getLocalDocumentMetadata")

    local all_documents = {}

    local documents_kv = self:getStatisticsBookKV()
    local bookinfo_books = self:getBookInfoBookKV()

    for _, v in pairs(ReadHistory.hist) do
        if DocSettings:hasSidecarFile(v.file) then
            local docsettings = DocSettings:open(v.file)

            -- Ensure Partial MD5 Exists
            local pmd5 = docsettings:readSetting("partial_md5_checksum")
            if not pmd5 then
                pmd5 = self:getPartialMd5(v.file)
                docsettings:saveSetting("partial_md5_checksum", pmd5)
            end

            -- Get Document Props
            local doc_props = docsettings:readSetting("doc_props")
            local fdoc = bookinfo_books[v.file] or {}

            -- Update or Create
            if documents_kv[pmd5] ~= nil then
                local doc = documents_kv[pmd5]

                -- Merge Statistics, History, and BookInfo
                doc.title = doc.title or doc_props.title or fdoc.title
                doc.author = doc.author or doc_props.authors or fdoc.author
                doc.series = doc.series or doc_props.series or fdoc.series
                doc.lang = doc.lang or doc_props.language or fdoc.lang

                -- Merge History and BookInfo
                doc.series_index = doc_props.series_index or fdoc.series_index
                doc.description = doc_props.description or fdoc.description
                doc.filepath = v.file
            else
                -- Merge History and BookInfo
                documents_kv[pmd5] = {
                    title = doc_props.title or fdoc.title,
                    author = doc_props.authors or fdoc.author,
                    series = doc_props.series or fdoc.series,
                    series_index = doc_props.series_index or fdoc.series_index,
                    lang = doc_props.language or fdoc.lang,
                    description = doc_props.description or fdoc.description,
                    filepath = v.file
                }
            end
        end
    end

    -- Convert KV -> Array
    for pmd5, v in pairs(documents_kv) do
        table.insert(all_documents, {
            id = pmd5,
            title = v.title,
            author = v.author,
            series = v.series,
            series_index = v.series_index,
            lang = v.lang,
            description = v.description,
            filepath = v.filepath
        })
    end

    return all_documents
end

function SyncNinja:getStatisticsActivity(timestamp)
    logger.dbg("SyncNinja: getStatisticsActivity")

    local all_data = {}
    local conn = SQ3.open(statistics_db)
    local stmt = conn:prepare(string.format(STATISTICS_ACTIVITY_SINCE_QUERY,
                                            timestamp))
    local rows = stmt:resultset("i", 5000)
    conn:close()

    -- No Results
    if rows == nil then return all_data end

    -- Normalize
    for i, v in pairs(rows[1]) do
        table.insert(all_data, {
            document = rows[1][i],
            start_time = tonumber(rows[2][i]),
            duration = tonumber(rows[3][i]),
            page = tonumber(rows[4][i]),
            pages = tonumber(rows[5][i])
        })
    end

    return all_data
end

-- Returns KEY:VAL (MD5:<TABLE>)
function SyncNinja:getStatisticsBookKV()
    logger.dbg("SyncNinja: getStatisticsBookKV")

    local all_data = {}
    local conn = SQ3.open(statistics_db)
    local stmt = conn:prepare(STATISTICS_BOOK_QUERY)
    local rows = stmt:resultset("i", 1000)
    conn:close()

    -- No Results
    if rows == nil then return all_data end

    -- Normalize
    for i, v in pairs(rows[1]) do
        local pmd5 = rows[1][i]
        all_data[pmd5] = {
            title = rows[2][i],
            author = rows[3][i],
            series = rows[4][i],
            lang = rows[5][i]
        }
    end

    return all_data
end

-- Returns KEY:VAL (FILEPATH:<TABLE>)
function SyncNinja:getBookInfoBookKV()
    logger.dbg("SyncNinja: getBookInfoBookKV")

    local all_data = {}
    local conn = SQ3.open(bookinfo_db)
    local stmt = conn:prepare(BOOKINFO_BOOK_QUERY)
    local rows = stmt:resultset("i", 1000)
    conn:close()

    -- No Results
    if rows == nil then return all_data end

    -- Normalize
    for i, v in pairs(rows[1]) do
        filepath = rows[1][i]
        all_data[filepath] = {
            title = rows[2][i],
            author = rows[3][i],
            series = rows[4][i],
            series_index = tonumber(rows[5][i]),
            lang = rows[6][i],
            description = rows[7][i]
        }
    end

    return all_data
end

function SyncNinja:getPartialMd5(file)
    logger.dbg("SyncNinja: getPartialMd5")

    if file == nil then return nil end
    local bit = require("bit")
    local lshift = bit.lshift
    local step, size = 1024, 1024
    local update = md5()
    local file_handle = io.open(file, 'rb')
    if file_handle == nil then return nil end
    for i = -1, 10 do
        file_handle:seek("set", lshift(step, 2 * i))
        local sample = file_handle:read(size)
        if sample then
            update(sample)
        else
            break
        end
    end
    file_handle:close()
    return update()
end

return SyncNinja