【Lua实战】状态机模式：NPC 行为的三态切换

---NPC 状态机：三态切换
local STATES = {
    patrol = {
        enter = function(npc)
            npc.speed = npc.patrolSpeed
        end,
        update = function(npc)
            if npc:seeEnemy() then
                return 'alert'
            end
        end,
    },
    alert = {
        enter = function(npc)
            npc.speed = npc.alertSpeed
            npc.sayRange = 10
        end,
        update = function(npc)
            if not npc:seeEnemy() then
                return 'patrol'
            end
            if npc:distToEnemy() < 5 then
                return 'chase'
            end
        end,
    },
    chase = {
        enter = function(npc)
            npc.speed = npc.chaseSpeed
        end,
        update = function(npc)
            if not npc:seeEnemy() then
                return 'patrol'
            end
        end,
    },
}

function StateMachine.tick(npc)
    local st = STATES[npc.state]
    if not st then return end
    local next_ = st.update(npc)
    if next_ and next_ ~= npc.state then
        if st.exit then st.exit(npc) end
        npc.state = next_
        if STATES[next_].enter then
            STATES[next_].enter(npc)
        end
    end
end

---四态扩展：增加返回出生点状态
STATES.goHome = {
    enter = function(npc)
        npc.speed = npc.patrolSpeed * 1.5
        npc.path = Path.find(npc, npc.homeX, npc.homeY)
    end,
    update = function(npc)
        if npc.x == npc.homeX and npc.y == npc.homeY then
            return 'patrol'
        end
    end,
}