-- The functions and variables in this file are only for use in the mod itself.
-- Those that do real work should be local and wrapped in public functions
local debug = yl_scheduler.settings.debug or true

local function say(text)
    if debug then minetest.log("action", "[MOD] yl_scheduler : " .. text) end
end

-- Helpers

local function filename2uuid(filename) return filename:sub(1, -6) end

local function is_visible(filename) return (string.sub(filename, 1, 1) ~= ".") end

local function is_json(filename) return (filename:match("%.json$")) end

local function generate_uuid()
    local template = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
    return string.gsub(template, '[xy]', function(c)
        local v = (c == 'x') and math.random(0, 15) or math.random(8, 11)
        return string.format('%x', v)
    end)
end

local function is_uuid_duplicate(UUID)
    for i, task in ipairs(yl_scheduler.tasks) do
        say("action", "task.id=" .. dump(task.id) .. ", UUID=" .. dump(UUID))
        if task.id == UUID then return true end
    end
    return false
end

local function create_uuid()
    local max_attempts = 10

    local UUID

    repeat
        UUID = generate_uuid()
        max_attempts = max_attempts - 1
        if max_attempts < 0 then
            return false, "Cannot find non-duplicate UUID"
        end
    until (is_uuid_duplicate(UUID) == false)

    if UUID == "" then return false, "UUID empty" end

    return true, UUID

end

function yl_scheduler.create_uuid() return create_uuid() end

--- ###

local function sort_by_timestamp(tasks)

    local function compare(task1, task2) return task1.at < task2.at end

    table.sort(tasks, compare)

    return tasks
end

function yl_scheduler.sort_by_timestamp(tasks) return sort_by_timestamp(tasks) end

local function split(str)
    local parts = {}
    for part in str:gmatch("[^,%s]+") do table.insert(parts, part) end
    return parts
end

local function ends_with(str, suffix) return str:sub(-suffix:len()) == suffix end

-- Validate values

local function validate_at(at)
    -- Let's assume the calcuation already happened and we're dealing with a
    -- unix epoch timestamp in utc. We can't detect utc though.
    if (at == nil) then
        return false, "at: No time given"
    elseif type(at) ~= "number" then
        return false, "at: Wrong type"
    elseif at > os.time(os.date("!*t")) + (10 * 365 * 24 * 60 * 60) then
        return false, "at: Not within 10 years"
    else
        return true, "at: all good"
    end
end

local function validate_func(func)
    -- Should we check existence of the function at set time?? No.
    -- Functions may be retrofitted. We need to check their existance
    -- at runtime, not during storing
    if (func == nil) then
        return false, "func: No func given"
    elseif type(func) ~= "string" then
        return false, "func: Wrong type"
    else
        return true, "func: all good"
    end
end

local function validate_params(params)
    -- We don't know much about params.
    -- Could be nil, could be a table
    if (type(params) ~= "nil") and (type(params) ~= "table") then
        return false, "params: Wrong type"
    else
        return true, "params: all good"
    end
end

local function validate_owner(owner)
    -- Owner could be an ingame player but also a mod or mechanic
    if (owner == nil) then
        return false, "func: No owner given"
    elseif type(owner) ~= "string" then
        return false, "owner: Wrong type"
    else
        return true, "owner: all good"
    end
end

local function validate_notes(notes)
    -- Notes are optional
    -- Could be nil, could be a string
    if (type(notes) ~= "nil") and (type(notes) ~= "string") then
        return false, "notes: Wrong type"
    else
        return true, "notes: all good"
    end
end

local function validate(at, func, params, owner, notes)

    local at_succes, at_message = validate_at(at)
    if (at_succes == false) then return false, at_message end
    local func_succes, func_message = validate_func(func)
    if (func_succes == false) then return false, func_message end
    local params_succes, params_message = validate_params(params)
    if (params_succes == false) then return false, params_message end
    local owner_succes, owner_message = validate_owner(owner)
    if (owner_succes == false) then return false, owner_message end
    local notes_succes, notes_message = validate_notes(notes)
    if (notes_succes == false) then return false, notes_message end

    return true, "All good"
end

function yl_scheduler.validate(at, func, params, owner, notes)
    return validate(at, func, params, owner, notes)
end

-- Loading and Saving

local function get_savepath()
    -- TODO: Can we assume the path exists?
    local savepath = yl_scheduler.worldpath .. yl_scheduler.settings.save_path
    say("savepath : " .. dump(savepath))
    return savepath
end

local function get_filepath(UUID)
    local path_to_file = yl_scheduler.worldpath ..
                             yl_scheduler.settings.save_path .. DIR_DELIM ..
                             UUID .. ".json"
    say(UUID .. ":" .. dump(path_to_file))
    return path_to_file
end

local function save_json(UUID, content)
    if type(UUID) ~= "string" or type(content) ~= "table" then return false end
    local savepath = get_filepath(UUID)
    local savecontent = minetest.write_json(content)
    return minetest.safe_file_write(savepath, savecontent)
end

local function load_json(path)
    local file = io.open(path, "r")
    if not file then return false, "Error opening file: " .. path end

    local content = file:read("*all")
    file:close()

    if not content then return false, "Error reading file: " .. path end

    return true, minetest.parse_json(content)
end

-- Public functions wrap the private ones, so they can be exchanged easily

function yl_scheduler.load_json(filename, ...) return load_json(filename, ...) end

function yl_scheduler.save_json(filename, content, ...)
    return save_json(filename, content, ...)
end

-- ### yl_scheduler.load_all_tasks ###

local function load_all_tasks()
    -- Get all json files from savepath
    -- Excluding invisible
    -- Excluding non-json files
    local save_path = get_savepath()
    local files = minetest.get_dir_list(save_path, false) or {}
    local tasks = {}
    local total = 0
    local good = 0
    local bad = 0
    for key, filename in ipairs(files) do
        total = total + 1
        if is_visible(filename) and is_json(filename) then
            local UUID = filename2uuid(filename)
            local filepath = get_filepath(UUID)
            local success, content = load_json(filepath)

            if success then
                good = good + 1
                table.insert(tasks, content)
            else
                bad = bad + 1
            end

        end
    end

    -- Sort table for "at"
    yl_scheduler.tasks = sort_by_timestamp(tasks)

    if bad == 0 then
        minetest.log("action",
                     "[MOD] yl_scheduler : bad = " .. tostring(bad) ..
                         ", good = " .. tostring(good) .. ", total = " ..
                         tostring(total))
        return true, good, bad
    else
        minetest.log("warning",
                     "[MOD] yl_scheduler : bad = " .. tostring(bad) ..
                         ", good = " .. tostring(good) .. ", total = " ..
                         tostring(total))
        return false, good, bad
    end
end

function yl_scheduler.load_all_tasks() return load_all_tasks() end

-- ### priv exists ###

local function priv_exists(priv)
    return (minetest.registered_privileges[priv] ~= nil) or false
end

function yl_scheduler.priv_exists(priv) return priv_exists(priv) end

-- ### get_privs ###
-- {[yl_scheduler.settings.admin_priv] = true}

local cmds = {}

cmds["scheduler_add"] = "taskadd_privs"
cmds["scheduler_remove"] = "taskremove_privs"
cmds["scheduler_list"] = "tasklist_privs"
cmds["scheduler_clean"] = "taskclean_privs"

local function get_privs(chatcommand_cmd) -- scheduler_add -- taskadd_privs
    local privs = split(yl_scheduler.settings[cmds[chatcommand_cmd]])
    local ret = {}
    for _, priv in ipairs(privs) do ret[priv] = true end
    return ret
end

function yl_scheduler.get_privs(chatcommand_cmd)
    return get_privs(chatcommand_cmd)
end

-- ### check privs ###

function check_privs()
    for key, value in pairs(yl_scheduler.settings) do
        if ends_with(key, "_privs") then
            local parts = split(value)
            for _, part in ipairs(parts) do
                assert(priv_exists(part), "yl_scheduler : configured priv " ..
                           dump(part) .. " doesn not exist.")
            end
        end
    end
    say("PASS priv check")
end

function yl_scheduler.check_privs() return check_privs() end

-- Remove file

local function remove_file(UUID)
    local path = yl_scheduler.get_filepath(UUID)
    return os.remove(path)
end

function yl_scheduler.remove_file(UUID) return remove_file(UUID) end

-- ### Chatcommands ###

-- ### scheduler_add ###

local function cmd_scheduler_add(name, c_params)
    -- This is what a chatcommand may look like:
    -- /scheduler_add 384756378465$minetest.log$action, text to be logged$$some notes
    -- /scheduler_add 384756378465$minetest.log$action, text to be logged
    -- /scheduler_add 384756378465$switch_maze
    -- /scheduler_add 384756378465$switch_maze$$$some more notes

    -- cast:
    -- /scheduler_add 384756378465$switch_maze$(int)456, (string)mystring$some more notes

    -- mask:
    -- /scheduler_add 384756378465$switch_maze$456,mystring$int, string$some more notes

    -- The mask should be optional, if none is given we assume strings

    if not c_params or c_params == "help" then
        return true,
               "Adds a new task that executes a function with params at the given time.\n" ..
                   "Separate time, function, parameters, mask and notes with $\n" ..
                   "Example: /scheduler_add 1712679465$minetest.log$action,mytext$string,string$mynotes\n"
    elseif c_params == "helpmask" then
        return true,
               "Provide a parameter mask to convert the parameters to number or table" ..
                   "Allowed values are \"string\",\"number\",\"table\"" ..
                   "If your use case requires other types, please create a wrapper function."
    end

    local t_parameters = string.split(c_params, "$", true)

    local at = tonumber(t_parameters[1])
    local func = t_parameters[2]
    -- local string_params = string.split(t_parameters[3], ",") -- optional
    local params = string.split(t_parameters[3], ",") -- optional
    local mask = string.split(t_parameters[4], ",") or {} -- optional
    local owner = name or "N/A"
    local notes = t_parameters[5] or "" -- optional

    -- local param_success, params = unmask_params(string_params, mask)

    if (param_success == false) then return false, params end

    local success, message = yl_scheduler.set_task(at, func, params, owner,
                                                   notes)
    if success == true then
        yl_scheduler.tasks = sort_by_timestamp(yl_scheduler.tasks)
    end

    return success, message
end

function yl_scheduler.cmd_scheduler_add(name, params)
    return cmd_scheduler_add(name, params)
end

-- ### scheduler_remove ###

local function cmd_scheduler_remove(name, params)
    -- Defense: Overlap with yl_scheduler.remove_task(UUID)
    -- Store
    -- Re-sort tasks table
end

function yl_scheduler.cmd_scheduler_remove(name, params)
    return cmd_scheduler_remove(name, params)
end

-- ### scheduler_list ###

local function cmd_scheduler_list(name, params)
    -- Defense: Overlap with yl_scheduler.list_all_tasks() and yl_scheduler.list_task(UUID)
    -- Display nicely. Steal from ... I mean INSPIRE ... by yl_cinema list? Or formspec output?
end

function yl_scheduler.cmd_scheduler_list(name, params)
    return cmd_scheduler_list(name, params)
end

-- ### scheduler_clean ###

local function cmd_scheduler_clean(name, params)
    -- Just do it and at best return how many were removed, how many remain and how many the list had before.
    -- Use yl_scheduler.clean_executed_tasks() and yl_scheduler.clean_past_tasks()
end

function yl_scheduler.cmd_scheduler_clean(name, params)
    return cmd_scheduler_clean(name, params)
end