--
-- Surveys
--
-- yl_survey.get_data
--
local function get_data()
    if next(yl_survey.data) then
        return true, yl_survey.data
    else
        return false, {}
    end
end

function yl_survey.get_data() return get_data() end

-- yl_survey.get_survey
--

local function get_record(id)
    local success, data = yl_survey.get_data()
    if (success == false) then return nil end
    return table.copy(data[id]) -- {data} or nil
end

function yl_survey.get_record(id) return get_record(id) end

-- yl_survey.create_survey
--

local function validate_nil_or_positive(value)
    if (value == nil) then return true end
    if ((type(value) == "number") and (value >= 0)) then return true end
    return false
end

local function validate(value, expect_type, allow_nil)
    if ((allow_nil == true) and (value == nil)) then return true end
    if ((allow_nil == false) and (value == nil)) then return false end
    if (type(value) == expect_type) then return true end
    return false
end

local function validate_questiontype(allowed_types)
    local valid_types = {
        singlechoice = true,
        multiplechoice = true,
        freetext = true
    }

    local sm_count = 0
    local ft_count = 0

    for _, t in ipairs(allowed_types) do

        -- Invalid question type
        if (valid_types[t] == nil) then return false end

        -- Either singlechoice OR multiplechoice
        if ((t == "singlechoice") or (t == "multiplechoice")) then
            sm_count = sm_count + 1
        end

        if sm_count > 1 then return false end

        -- Only one freetext allowed
        if (t == "freetext") then ft_count = ft_count + 1 end

        if ft_count > 1 then return false end

    end

    if ((ft_count + sm_count) == 0) then return false end

    return true
end

local function create_survey(owner, allow_names, allow_anonymous, allow_changes,
                             timestamp_start, timestamp_end)
    -- Defense
    if ((type(owner) ~= "string") or (owner == "")) then
        return false, yl_survey.t("owner must be string")
    end

    if (allow_names == nil) then allow_names = true end -- set default
    if (type(allow_names) ~= "boolean") then
        return false, yl_survey.t("allow_names must be boolean")
    end
    if (allow_anonymous == nil) then allow_anonymous = true end -- set default
    if (type(allow_anonymous) ~= "boolean") then
        return false, yl_survey.t("allow_anonymous must be boolean")
    end
    if (allow_changes == nil) then allow_changes = false end -- set default
    if (type(allow_changes) ~= "boolean") then
        return false, yl_survey.t("allow_changes must be boolean")
    end

    if (validate_nil_or_positive(timestamp_start) == false) then
        return false, yl_survey.t(
                   "timestamp_start if given then must be number and not negative")
    end
    if (validate_nil_or_positive(timestamp_end) == false) then
        return false, yl_survey.t(
                   "timestamp_end if given then must be number and not negative")
    end

    -- Specialcase: We don't accept surveys NOONE can take part in
    --[[
    if ((allow_names == false) and (allow_anonymous == false)) then
        return false, yl_survey.t("Noone can take part in that survey. " ..
                                      "Neither named nor anonymous participants are allowed")
    end
    ]] --

    if ((allow_names == false) and (allow_anonymous == false) and
        (allow_changes == false)) then
        return false, yl_survey.t("Noone can take part in that survey. " ..
                                      "Neither named nor anonymous participants are allowed. " ..
                                      " You can't change it later")
    end

    -- Specialcase: We don't accept surveys where the enddate is smaller than the startdate
    if (timestamp_start and timestamp_end and (timestamp_start >= timestamp_end) and
        (allow_changes == false)) then
        return false, yl_survey.t("Noone can take part in that survey. " ..
                                      "It ends before it starts and you can't change it later")
    end

    -- UUID
    local get_uuid_success, UUID = yl_survey.create_uuid()
    if (get_uuid_success == false) then return false, UUID end

    -- Add to list
    local metadata = {
        id = UUID,
        owner = owner,
        allow_names = allow_names,
        allow_anonymous = allow_anonymous,
        allow_changes = allow_changes,
        timestamp_start = timestamp_start,
        timestamp_end = timestamp_end,
        creation_date = os.time(),
        modification_date = os.time()
    }
    local record = {}
    record["metadata"] = metadata

    -- Store
    local success = yl_survey.save(UUID, record)
    if (success == true) then
        yl_survey.data[UUID] = record
        return true, UUID
    else
        return false, yl_survey.t("Could not store")
    end
end

function yl_survey.create_survey(owner, allow_names, allow_anonymous,
                                 allow_changes, timestamp_start, timestamp_end)
    return create_survey(owner, allow_names, allow_anonymous, allow_changes,
                         timestamp_start, timestamp_end)
end

-- yl_survey.edit_survey
--

local function edit_survey(id, owner, allow_names, allow_anonymous,
                           allow_changes, timestamp_start, timestamp_end,
                           delete_responses)
    -- Defense
    if (validate(id, "string", false) == false) then
        return false, yl_survey.t("id must be string")
    end
    if (validate(owner, "string", true) == false) then
        return false, yl_survey.t("owner must be string")
    end
    if (validate(allow_names, "boolean", true) == false) then
        return false, yl_survey.t("allow_names must be boolean")
    end
    if (validate(allow_anonymous, "boolean", true) == false) then
        return false, yl_survey.t("allow_anonymous must be boolean")
    end
    if (validate(allow_changes, "boolean", true) == false) then
        return false, yl_survey.t("allow_changes must be boolean")
    end
    if (validate(timestamp_start, "number", true) == false) then
        return false, yl_survey.t("timestamp_start must be number")
    end
    if (validate(timestamp_end, "number", true) == false) then
        return false, yl_survey.t("timestamp_end must be number")
    end
    if (validate(delete_responses, "boolean", true) == false) then
        return false, yl_survey.t("delete_responses must be boolean")
    end
    if (validate_nil_or_positive(timestamp_start) == false) then
        return false, yl_survey.t(
                   "timestamp_start if given then must be number and not negative")
    end
    if (validate_nil_or_positive(timestamp_end) == false) then
        return false, yl_survey.t(
                   "timestamp_end if given then must be number and not negative")
    end

    local record = yl_survey.get_record(id)

    if (record == nil) then
        return false, yl_survey.t("record does not exist")
    end
    if (record["metadata"].allow_changes == false) then
        return false, yl_survey.t("no changes allowed")
    end

    local metadata = {
        id = record["metadata"].id, -- This value cannot change
        owner = owner or record["metadata"].owner,
        allow_names = allow_names or record["metadata"].allow_names,
        allow_anonymous = allow_anonymous or record["metadata"].allow_anonymous,
        allow_changes = allow_changes or record["metadata"].allow_changes,
        timestamp_start = timestamp_start or record["metadata"].timestamp_start,
        timestamp_end = timestamp_end or record["metadata"].timestamp_end,
        creation_date = record["metadata"].creation_date, -- This value cannot change
        modification_date = os.time() -- This value must change
    }

    record["metadata"] = metadata

    -- Delete responses
    local no
    if (delete_responses == true) then
        record, no = yl_survey.delete_responses(record)
    end

    -- Store
    local success = yl_survey.save(id, record)
    if (success == true) then
        yl_survey.data[id] = record
        return true, id
    else
        return false, yl_survey.t("Could not store")
    end

end

function yl_survey.edit_survey(id, owner, allow_names, allow_anonymous,
                               allow_changes, timestamp_start, timestamp_end,
                               delete_responses)
    return edit_survey(id, owner, allow_names, allow_anonymous, allow_changes,
                       timestamp_start, timestamp_end, delete_responses)
end

-- yl_survey.remove_record
--

local function remove_record(id)
    local data_success, data = yl_survey.get_data()
    if (data_success ~= true) then return false, "Cannot get data" end

    local remove_success = yl_survey.remove_file(id)
    if (remove_success ~= true) then
        return false, yl_survey.t("Could not remove")
    end

    local record = yl_survey.get_record(id)
    if (record == nil) then
        return false, yl_survey.t("record not found, cannot remove")
    end

    data[id] = nil
    return true, record
end

function yl_survey.remove_record(id) return remove_record(id) end

--
-- Questions
--

local function create_question(id, question, category, sort, allowed_types,
                               answers, enabled)
    -- Defense
    if (validate(id, "string", false) == false) then
        return false, yl_survey.t("id must be string")
    end
    if (validate(question, "string", false) == false) then
        return false, yl_survey.t("question must be string")
    end
    if (category == nil) then category = "" end
    if (validate(category, "string", false) == false) then
        return false, yl_survey.t("category must be string")
    end
    if (validate_nil_or_positive(sort) == false) then
        return false, yl_survey.t("sort must be positive number")
    end
    if (validate(allowed_types, "table", false) == false) then
        return false, yl_survey.t("allowed_types must be table")
    end
    if (validate(answers, "table", true) == false) then
        return false, yl_survey.t("answers must be table")
    end
    if (enabled == nil) then enabled = true end
    if (validate(enabled, "boolean", false) == false) then
        return false, yl_survey.t("enabled must be boolean")
    end

    -- Specialcase : allowed_types must be a combination of
    -- "singlechoice" or "multiplechoice" or "freetext"
    if (validate_questiontype(allowed_types) == false) then
        return false, yl_survey.t("wrong allowed_types")
    end

    -- Specialcase : answers cannot be nil or empty if allowedtypes has either multiplechoice or singlechoice
    if (((answers == nil) or (next(answers) == nil)) and
        ((allowed_types["multiplechoice"] ~= nil) or
            (allowed_types["singlechoice"] ~= nil))) then
        return false, yl_survey.t(
                   "answers cannot be nil or empty if allowedtypes has either multiplechoice or singlechoice")
    end

    -- Specialcase : given sort is a duplicate
    if ((type(sort) == "number") and (yl_survey.is_duplicate(record, sort) == true)) then
        return false, yl_survey.t("sort is duplicate")
    end

    local record = yl_survey.get_record(id)

    if (record == nil) then
        return false, yl_survey.t("record does not exist")
    end
    if (record["metadata"].allow_changes == false) then
        return false, yl_survey.t("no changes allowed")
    end

    -- Payload

    -- if sort is nil, then find next sort
    local next_sort = sort or yl_survey.find_next_free_number(record, "sort")

    -- Find next free q_id
    local next_q_id, dupe = yl_survey.find_next_free_number(record, "id")

    local t_question = {
        id = next_q_id,
        category = category,
        sort = next_sort,
        question = question,
        enabled = true,
        allowed_types = allowed_types,
        answers = answers,
        responses = {}
    }

    record[tostring(next_q_id)] = t_question

    -- Store
    local success = yl_survey.save(id, record)
    if (success == true) then
        yl_survey.data[id] = record
        return true, next_q_id
    else
        return false, yl_survey.t("Could not store")
    end
end

function yl_survey.create_question(id, question, category, sort, allowed_types,
                                   answers, enabled)
    return create_question(id, question, category, sort, allowed_types, answers, enabled)
end