-- 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("is_uuid_duplicate 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

function string_to_boolean(value)
    if value == "true" then
        return true
    elseif value == "false" then
        return false
    else
        return nil
    end
end

function string_to_table(value)
    -- TODO: imppement that somehow
    return {}
end

-- taken from yl_cinema
-- TODO: Shoudl we API-fy this?

local function format_table(t)
    -- Format of t must be {{row1,row2,row3, ...},{row1,row2,row3, ...},...}
    local blanks_between_rows = 3
    local max_row_length = {}
    for linenumber = 1, #t do
        for rownumber = 1, #t[linenumber] do
            local row_length = #tostring(t[linenumber][rownumber])
            if (max_row_length[rownumber] or 0) < row_length then
                max_row_length[rownumber] = row_length
            end
        end
    end

    local ret = {}

    for linenumber = 1, #t do
        local line_s = ""
        for rownumber = 1, #t[linenumber] do
            local text = t[linenumber][rownumber]
            local text_length = #tostring(text)
            local add_blanks = max_row_length[rownumber] - text_length
            local newtext = t[linenumber][rownumber]
            for add = 1, (add_blanks + blanks_between_rows) do
                newtext = newtext .. " "
            end
            line_s = line_s .. newtext
        end
        table.insert(ret, line_s)
    end
    return table.concat(ret, "\n")
end

function split_with_escapes(str, separator, escaper)
    local ret = {}
    local current = ""
    local esc = false

    for i = 1, #str do
        local char = str:sub(i, i)
        if char == escaper then
            if esc == true then
                current = current .. char
                esc = false
            else
                esc = true
            end
        elseif char == separator then
            if esc == true then
                current = current .. char
                esc = false
            else
                table.insert(ret, current)
                current = ""
                -- esc = true
            end
        else
            current = current .. char
        end
    end

    table.insert(ret, current)
    return ret
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 maximum_timeframe_to_seconds(str)
    local pattern = "(%d+)%s*([mdw])"
    local amount, unit = str:match(pattern)
    if (unit == "m") then
        return amount * 60
    elseif (unit == "d") then
        return amount * 60 * 60 * 24
    elseif (unit == "w") then
        return amount * 60 * 60 * 24 * 7
    else
        return 0
    end
end

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 (yl_scheduler.settings.maximum_timeframe ~= nil) and
        (at > os.time() +
            maximum_timeframe_to_seconds(yl_scheduler.settings.maximum_timeframe)) then
        return false, "at: Not within " ..
                   dump(yl_scheduler.settings.maximum_timeframe)
    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

-- Unmask parameters
-- We need to take in the parameter table and the mask table
-- and return a parameter table casted to the types indicated
-- by the mask

function unmask_params(string_params, masks)
    -- Defense

    -- What happens if there are more parameters than masks?
    -- Then we only mask the first couple and assume string for the rest

    -- What happens if there are more masks than parameters?
    -- Then there is clearly something wrong

    -- Same number? Cool.

    if #string_params < #masks then return false, "Too many masks" end

    -- mask may be any of "string", "number", "table", "boolean", "nil"

    for _, mask in ipairs(masks) do
        if ((mask ~= "string") and (mask ~= "number") and (mask ~= "table") and
            (mask ~= "nil") and (mask ~= "boolean") and (mask ~= "bool")) then
            return false, "Unknown type " .. dump(mask)
        end
    end

    local ret = {}
    for i, param in ipairs(string_params) do
        local mask = masks[i] and string.trim(masks[i]) or "string" -- defaults to string
        param = string.trim(param)
        if ((mask == "") or (mask == nil) or (mask == "string")) then
            local r_param = param
            if type(r_param) ~= "string" then
                return false, "Cannot cast " .. param .. " to string"
            end
            ret[i] = r_param
        elseif (mask == "number") then
            local r_param = tonumber(param)
            if type(r_param) ~= "number" then
                return false, "Cannot cast " .. param .. " to number"
            end
            ret[i] = r_param
        elseif (mask == "table") then
            local r_param = string_to_table(param) -- TODO: implement string_to_table
            if type(r_param) ~= "table" then
                return false, "Cannot cast " .. param .. " to table"
            end
            ret[i] = r_param
        elseif ((mask == "bool") or (mask == "boolean")) then
            local r_param = string_to_boolean(param)
            if type(r_param) ~= "boolean" then
                return false, "Cannot cast " .. param .. " to boolean"
            end
            ret[i] = r_param
        else
            return false, "Unknown type " .. dump(mask)
        end
    end

    return true, ret
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("get_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("get_filepath : " .. dump(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
        if is_visible(filename) and is_json(filename) then
            total = total + 1
            local UUID = filename2uuid(filename)
            local filepath = get_filepath(UUID)
            local success, content = load_json(filepath)

            if success and (content.id == UUID) 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 = 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 yl_scheduler.settings.taskadd_privs == "" then
        return false, "Feature disabled"
    end

    if not c_params or 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 = t_parameters[3] and
                              split_with_escapes(t_parameters[3], ",", "\\") or
                              {} -- optional
    local masks = t_parameters[4] and 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, masks)

    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)

    if yl_scheduler.settings.taskremove_privs == "" then
        return false, "Feature disabled"
    end

    if not params or params == "" or params == "help" then
        return true, "Removes an existing task from the list.\n" ..
                   "Example: /scheduler_remove 11a47d48-4d0c-47ab-a5ef-4f56781cae03"
    end

    local UUID = string.trim(params)

    local success, message = yl_scheduler.remove_task(UUID)

    if success == true then
        yl_scheduler.tasks = sort_by_timestamp(yl_scheduler.tasks)
    end

    return success, "Removed: " .. dump(message)
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)

    if yl_scheduler.settings.tasklist_privs == "" then
        return false, "Feature disabled"
    end

    if not params or params == "help" then
        return true, "Lists all existing tasks from the list.\n" ..
                   "Example: /scheduler_remove 11a47d48-4d0c-47ab-a5ef-4f56781cae03"
    end

    local tasks = {}
    local success

    local args = string.split(params, "=")

    if params == "" then
        -- return whole list
        say("cmd_scheduler_list Whole list")
        success, tasks = yl_scheduler.list_all_tasks()
    elseif #args == 1 then
        -- return UUID search
        say("cmd_scheduler_list UUID search")
        local UUID = string.trim(params)
        success, tasks = yl_scheduler.find_task(UUID)
    elseif #args == 2 then
        -- search for key
        say("cmd_scheduler_list Key search")
        local key = args[1]
        local value = args[2]
        local s_success, all_tasks = yl_scheduler.list_all_tasks()
        for _, task in ipairs(all_tasks) do
            -- TODO: Should we exact match or string.find?
            if task[key] == value then table.insert(tasks, task) end
        end
        success = s_success
    else
        return false, "Parameter unclear, please do /scheduler_remove help"
    end

    if (#tasks == 0) or (success == false) then return true, "No match" end

    -- Formatting output
    local f_tasks = {{"ID", "at/done", "func", "#params", "owner", "notes"}}

    for _, task in ipairs(tasks) do

        local id = task.id or "N/A"
        local atdone
        if not task.done or (task.done and (task.done == -1)) then
            atdone = "at " .. os.date("!%c", task.at or 0)
        elseif task.done and (task.done > 0) then
            atdone = "done " .. os.date("!%c", task.done or 0)
        else
            atdone = "N/A"
        end
        local func = task.func or "N/A"

        local f_params = task.params and tostring(#task.params or 0) or "N/A"
        if task.params and (type(task.params) ~= "table") then
            f_params = "N/A"
            minetest.log("warning", "[MOD] yl_scheduler : UUID " .. dump(id) ..
                             " has string param instead of table")
        end

        local owner = task.owner or "N/A"
        local notes = task.notes or ""

        local t = {id, atdone, func, f_params, owner, notes}
        table.insert(f_tasks, t)
    end

    return true, format_table(f_tasks)
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()

    if yl_scheduler.settings.taskclean_privs == "" then
        return false, "Feature disabled"
    end

    local args = string.split(params, " ")

    if ((#args > 1) or (not params) or (params == "help")) then
        return true,
               "Cleans executed tasks or tasks of which the scheduled execution date is in the past.\n" ..
                   "Omitting the parameter results in both past and done tasks cleaned.\n" ..
                   "Examples: /scheduler_clean or /scheduler_clean past or /scheduler_clean done"
    end

    local past_success
    local past_amount_deleted
    local past_amount_remaining

    local done_success
    local done_amount_deleted
    local done_amount_remaining

    if args[1] == "past" then
        past_success, past_amount_deleted, past_amount_remaining =
            yl_scheduler.clean_past_tasks()
    elseif args[1] == "done" then
        done_success, done_amount_deleted, done_amount_remaining =
            yl_scheduler.clean_executed_tasks()
    elseif args[1] == nil then
        past_success, past_amount_deleted, past_amount_remaining =
            yl_scheduler.clean_past_tasks()
        done_success, done_amount_deleted, done_amount_remaining =
            yl_scheduler.clean_executed_tasks()
    else
        return false, "Unknown parameter, please do /scheduler_clean help"
    end

    if ((past_success == true) or (done_success == true)) then
        yl_scheduler.tasks = sort_by_timestamp(yl_scheduler.tasks)
    end

    local ret = ""

    if (past_success == true) then
        ret = ret .. "Cleaned up " .. tostring(past_amount_deleted) ..
                  " past tasks, remaining " .. tostring(past_amount_remaining) ..
                  ". "
    elseif (past_success == false) then
        ret = ret .. "Cleaning of past tasks failed: " ..
                  dump(past_amount_deleted) .. " "
    end
    if (done_success == true) then
        ret = ret .. "Cleaned up " .. tostring(done_amount_deleted) ..
                  " done tasks, remaining " .. tostring(done_amount_remaining) ..
                  ". "
    elseif (done_success == false) then
        ret = ret .. "Cleaning of done tasks failed: " ..
                  dump(done_amount_deleted) .. " "
    end

    return true, ret
end

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