module:set_global();

local async = require("prosody.util.async");

local active_hosts = {}

function module.add_host(host_module)

    local last_run_times = host_module:open_store("cron", "map");
    active_hosts[host_module.host] = true;

    local function save_task(task, started_at)
        last_run_times:set(nil, task.id, started_at);
    end

    local function restore_task(task)
        if task.last == nil then
            task.last = last_run_times:get(nil, task.id);
        end
    end

    local function task_added(event)
        local task = event.item;
        if task.name == nil then task.name = task.when; end
        if task.id == nil then
            task.id = event.source.name .. "/" ..
                          task.name:gsub("%W", "_"):lower();
        end
        task.period = host_module:get_option_period(
                          task.id:gsub("/", "_") .. "_period", "1" .. task.when,
                          60, 86400 * 7 * 53);
        task.restore = restore_task;
        task.save = save_task;
        module:log("debug", "%s task %s added", task.when, task.id);
        return true
    end

    local function task_removed(event)
        local task = event.item;
        host_module:log("debug", "Task %s removed", task.id);
        return true
    end

    host_module:handle_items("task", task_added, task_removed, true);

    function host_module.unload() active_hosts[host_module.host] = nil; end
end

local function should_run(task, last)
    return not last or last + task.period * 0.995 <= os.time()
end

local function run_task(task)
    task:restore();
    if not should_run(task, task.last) then return end
    local started_at = os.time();
    task:run(started_at);
    task.last = started_at;
    task:save(started_at);
end

local task_runner = async.runner(run_task);
scheduled = module:add_timer(1, function()
    module:log("info", "Running periodic tasks");
    local delay = 3600;
    for host in pairs(active_hosts) do
        module:log("debug", "Running periodic tasks for host %s", host);
        for _, task in ipairs(module:context(host):get_host_items("task")) do
            task_runner:run(task);
        end
    end
    module:log("debug", "Wait %ds", delay);
    return delay
end);

module:add_item("shell-command", {
    section = "cron",
    section_desc = "View and manage recurring tasks",
    name = "tasks",
    desc = "View registered tasks",
    args = {},
    handler = function(self, filter_host)
        local format_table = require("prosody.util.human.io").table;
        local it = require("util.iterators");
        local row = format_table({
            {title = "Host", width = "2p"}, {title = "Task", width = "3p"},
            {title = "Desc", width = "3p"}, {title = "When", width = "1p"},
            {title = "Last run", width = "20"}
        }, self.session.width);
        local print = self.session.print;
        print(row());
        for host in it.sorted_pairs(filter_host and {[filter_host] = true} or
                                        active_hosts) do
            for _, task in ipairs(module:context(host):get_host_items("task")) do
                print(row({
                    host, task.id, task.name, task.when,
                    task.last and os.date("%Y-%m-%d %R:%S", task.last) or
                        "never"
                }));
            end
        end
    end
});