@startuml

skinparam dpi 150

start

: add start edge to queue;

repeat
    if (queue has next edge?) then (yes)
        : take next edge from queue;
    else (no)
        :return empty path;
        stop;
    endif

    if (is end edge?) then (yes)
        : build path from parent map;
        if (path validates?) then (yes)
            :return validated path;
            stop;
        else (no)
        endif
    else (no)
    endif

    if (edge visited?) then (yes)
    else (no)
        : mark edge visited;

        switch (edge type?)
            case ( certificate edge )
                : search certificate issuers in store;
                if (has issuers?) then (yes)
                    :add issuers to queue;
                    :map issuers edges to parent edge;
                    if (certificate has aia?) then (yes)
                        :add aia url edges to queue;
                        :map url edges to parent edge;
                    else (no)
                    endif
                else (no)
                    if (certificate has aia?) then (yes)
                        :add aia url edges to queue;
                        :map url edges to parent edge;
                    else (no)
                        : add end edge to queue;
                    endif
                endif
            case ( url edge )
                : download certificates with url;
                :map new certificate edges to parent edge;
                if (certificates are issuer?) then (yes)
                    :add issuers to queue;
                else (no)
                    : add end edge to queue;
                endif
            case ( end edge )
        endswitch


    endif
repeat while




@enduml