How to understand the following crop! function excerpted from the OpenStreetMapX package?

General Usage
1

Hi, I was reading the following function excerpted from OpenStreetMapX package and got a bit confused. Could anyone please let me know how to understand the following function, especially

new_node = OpenStreetMapX.boundary_point(nodes[way.nodes[i-1]], nodes[way.nodes[i]],bounds)
                        new_id = OpenStreetMapX.add_new_node!(nodes, new_node)
                        way.nodes[i-1] = new_id

The following is the function.

function crop!(nodes::Dict, bounds::OpenStreetMapX.Bounds, way::OpenStreetMapX.Way)
    valid = falses(length(way.nodes)+2)
    n = 1
    while n <= length(way.nodes)
        if !haskey(nodes, way.nodes[n])
            splice!(way.nodes, n)
            splice!(valid, n+1)
        else
            valid[n+1] = OpenStreetMapX.inbounds(nodes[way.nodes[n]], bounds)
            n += 1
        end
    end
    if sum(valid) == 0
        return true
    elseif sum(valid) < (length(valid)-2)
		leave = trues(length(way.nodes))
        for i in 2:(length(valid)-1)
            if !valid[i]
                if valid[i-1] != valid[i]
                    if !OpenStreetMapX.onbounds(nodes[way.nodes[i-2]], bounds)
                        new_node = OpenStreetMapX.boundary_point(nodes[way.nodes[i-2]], nodes[way.nodes[i-1]],bounds)
                        new_id = OpenStreetMapX.add_new_node!(nodes, new_node)
                        way.nodes[i-1] = new_id
                    else
						leave[i-1] = false
                    end
                elseif valid[i] != valid[i+1]
                    if !OpenStreetMapX.onbounds(nodes[way.nodes[i]], bounds)
                        new_node = OpenStreetMapX.boundary_point(nodes[way.nodes[i-1]], nodes[way.nodes[i]],bounds)
                        new_id = OpenStreetMapX.add_new_node!(nodes, new_node)
                        way.nodes[i-1] = new_id
                    else
                        leave[i-1] = false
                    end
                else
                    leave[i-1] = false
                end
            end
        end
		way.nodes = way.nodes[leave]
        return false
    else
        return false
    end
end