Lua视线判定：两点连线的逐格行进

flowchart TD
A[起点入列] --> B[向目标推进一格]
B --> C{这一格是墙}
C -- 是 --> D[判挡 记下挡格]
C -- 否 --> E{到目标了吗}
E -- 否 --> B
E -- 是 --> F[判通]

 fx-losray

-- @file LineOfSight.lua
-- 视线判定 —— 两点连线的逐格行进

local LineOfSight = {}

local CONST = {
    MAX_STEPS     = 64,

    COLOR_CLEAR   = "#3fb950",
    COLOR_BLOCK   = "#f85149",

    AUTOINC_BASE  = 1142000,
}

local _isWall     = nil
local _autoInc    = 0

local function GenID(prefix)
    _autoInc = _autoInc + 1
    return string.format("%s_%d", prefix or "LOS",
        CONST.AUTOINC_BASE + _autoInc)
end

local function ShowTip(msg)
    if msg and msg ~= "" then SL:ShowSystemTips(msg) end
end

function LineOfSight.BindWall(func)
    _isWall = func
end

function LineOfSight.BuildPath(x0, y0, x1, y1)
    local dx = math.abs(x1 - x0)
    local dy = math.abs(y1 - y0)
    local sx = x0 < x1 and 1 or -1
    local sy = y0 < y1 and 1 or -1
    local err = dx - dy
    local path = {}
    local cx, cy = x0, y0
    while true do
        path[#path + 1] = { cx, cy }
        if cx == x1 and cy == y1 then break end
        local e2 = 2 * err
        if e2 > -dy then
            err = err - dy
            cx = cx + sx
        end
        if e2 < dx then
            err = err + dx
            cy = cy + sy
        end
    end
    return path
end

-- 视线主入口：走廊逐格查墙，撞墙记序号
function LineOfSight.Check(x0, y0, x1, y1)
    if not _isWall then
        ShowTip("先挂墙表再查视线")
        return false, 0
    end
    local path = LineOfSight.BuildPath(x0, y0, x1, y1)
    for i, pos in ipairs(path) do
        if i > 1 and i < #path then
            if _isWall(pos[1], pos[2]) then
                return false, i
            end
        end
        if i > CONST.MAX_STEPS then break end
    end
    return true, #path
end

function LineOfSight.Cast()
    local myID = SL:GetValue("USER_ID")
    local myX = SL:GetValue("ACTOR_GRID_X", myID)
    local myY = SL:GetValue("ACTOR_GRID_Y", myID)
    local tid = SL:GetValue("MARK_TARGET_ID")
    local tX = SL:GetValue("ACTOR_GRID_X", tid)
    local tY = SL:GetValue("ACTOR_GRID_Y", tid)
    if not myX or not tX then return end
    local ok, at = LineOfSight.Check(myX, myY, tX, tY)
    if ok then
        ShowTip("视线畅通——" .. at .. "格直达")
    else
        ShowTip("视线被挡——第" .. at .. "格是墙")
    end
end

SL:ScheduleOnce(function()
    LineOfSight.BindWall(function(c, r)
        return SL:IsBlockCell(c, r)
    end)
    SL:BindDebugButton("查视线", function()
        LineOfSight.Cast()
    end)
    ShowTip("技能已加载: 视线判定 (调试按钮触发)")
end, 1.0)

function LineOfSight.Unload()
    _isWall = nil
end

return LineOfSight