mapreader

function path( tMaps, _yield )
    --Find start
    local function findStart()
        for k, sMap in ipairs( tMaps ) do
            local l = 1
            for line in sMap:gmatch( '[^\r\n]+' ) do
                for i = 1, #line do
                    if line:sub( i, i ):upper() == "X" then
                        return {x = i, y = l, z = k}
                    end
                end
                l = l + 1
            end
        end
    end
    --update removes already used path bits
    local function update( tbl )
        local l = 1
        local newString = {}
        local oldChar
        for line in tMaps[ tbl.z ]:gmatch( '[^\r\n]+' ) do
            if l == tbl.y then
                newString[l] = line:sub( 1, tbl.x - 1 ).." "..line:sub( tbl.x + 1, #line )
                oldChar = line:sub( tbl.x, tbl.x )
            else
                newString[l] = line
            end
            l = l + 1
        end
        return table.concat( newString, "\n" ), oldChar
    end
    --orient function
    local face = "up"
    local function orient( direction )
        if face == "up" and direction == "up" then
            return
        elseif face == "up" and direction == "right" then
            turtle.turnRight()
            face = "right"
        elseif face == "up" and direction == "left" then
            turtle.turnLeft()
            face = "left"
        elseif face == "up" and direction == "down" then
            turtle.turnRight()
            turtle.turnRight()
            face = "down"
        elseif face == "right" and direction == "up" then
            turtle.turnLeft()
            face = "up"
        elseif face == "right" and direction == "right" then
            return
        elseif face == "right" and direction == "left" then
            turtle.turnLeft()
            turtle.turnLeft()
            face = "left"
        elseif face == "right" and direction == "down" then
            turtle.turnRight()
            face = "down"
        elseif face == "left" and direction == "up" then
            turtle.turnRight()
            face = "up"
        elseif face == "left" and direction == "right" then
            turtle.turnRight()
            turtle.turnRight()
            face = "right"
        elseif face == "left" and direction == "left" then
            return
        elseif face == "left" and direction == "down" then
            turtle.turnLeft()
            face = "down"
        elseif face == "down" and direction == "up" then
            turtle.turnLeft()
            turtle.turnLeft()
            face = "up"
        elseif face == "down" and direction == "right" then
            turtle.turnLeft()
            face = "right"
        elseif face == "down" and direction == "left" then
            turtle.turnRight()
            face = "left"
        elseif face == "down" and direction == "down" then
            return
        end
    end
    --Find next position
    local function findNext( tbl )
        local oldChar
        tMaps[ tbl.z ], oldChar = update( tbl )
        local l = 1
        local compare = {
            D = true,
            U = true,
            ["#"] = true,
            d = true,
            u = true,
        }
        --Check current level
        for line in tMaps[ tbl.z ]:gmatch( '[^\r\n]+' ) do
            if l == tbl.y - 1 and compare[ line:sub( tbl.x, tbl.x ) ] then
                --turtle should move "up"
                return function() orient( "up" ) return turtle.forward() end, {x = tbl.x, y = tbl.y - 1, z = tbl.z}
            elseif l == tbl.y and compare[ line:sub( tbl.x - 1, tbl.x - 1 ) ] then
                --turtle should move "left"
                return function() orient( "left" ) return turtle.forward() end, {x = tbl.x - 1, y = tbl.y, z = tbl.z}
            elseif l == tbl.y and compare[ line:sub( tbl.x + 1, tbl.x + 1 ) ] then
                --turtle should move "right"
                return function() orient( "right" ) return turtle.forward() end, {x = tbl.x + 1, y = tbl.y, z = tbl.z}
            elseif l == tbl.y + 1 and compare[ line:sub( tbl.x, tbl.x ) ]then
                --turtle should move "down"
                return function() orient( "down" ) return turtle.forward() end, {x = tbl.x, y = tbl.y + 1, z = tbl.z}
            elseif oldChar:upper() == "U" then
                return function() return turtle.up() end, {x = tbl.x, y = tbl.y, z = tbl.z + 1}
            elseif oldChar:upper() == "D" then
                return function() return turtle.down() end, {x = tbl.x, y = tbl.y, z = tbl.z - 1}
            end
            l = l + 1
        end
    end
    local place = findStart()
    local path = {}
    while place do
        path[#path + 1], place = findNext( place )
    end
    path.x = 1
    path.yield = _yield
    local mt = {
    __call = function()
        if path[ path.x ] and path.yield then
            local success = path[ path.x ]()
            path.x = path.x + 1
            return success
        elseif path[ path.x ] then
            repeat
                path[ path.x ]()
                path.x = path.x + 1
            until not path[ path.x ]
        else
            return false
        end
    end,
    }
    setmetatable( path, mt )
    return path
end