【框架设计】任务链状态机框架：主线任务阶段推进与回档容错

local CHAIN = {
    [1] = { type = "kill",  target = "鸡",   num = 10 },
    [2] = { type = "talk",  npc = "屠夫" },
    [3] = { type = "item",  item = "沃玛号角", num = 1 },
}
local REWARD = { [1] = "金币|5000", [2] = "金创药|5", [3] = "金币|50000" }
function CHAIN_STATE(actor)
    local step = tonumber(getplayvar(actor, 2, "MAIN_STEP") or "1")
    return step
end

function chainAdvance(actor)
    local player = class(actor)
    local step = CHAIN_STATE(actor)
    local def = CHAIN[step]
    if def == nil then return end
    if def.type == "kill" then
        local cnt = tonumber(getplayvar(actor, 2, "MAIN_CNT") or "0") + 1
        setplayvar(actor, "HUMAN", "MAIN_CNT", cnt, 1)
        if cnt < def.num then return end
    end
    setplayvar(actor, "HUMAN", "MAIN_STEP", step + 1, 1)
    setplayvar(actor, "HUMAN", "MAIN_CNT", 0, 1)
    sendmail(actor, 0, "主线任务奖励", "阶段" .. step .. "完成", REWARD[step])
end