digraph install {
    node [shape="rectangle"];

    subgraph cluster_install_commmand {
        label = "";
        color = "none";

        command_install [label="Command: install", shape="oval", style="filled", fillcolor="lightblue"];
        decision_parse_version [label="Version format?", shape="diamond"];
        version [label = "Version"];

        installed_list [label="Installed list", shape="hexagon"];
        decision_already_installed [label="Already\ninstalled?", shape="diamond"];
        decision_force_install [label="Force\ninstall?", shape="diamond"];

        decision_write_version_file [label="Write .python-version?", shape="diamond"];
        write_version_file [label="Write .python-version file"];

        exit [label="Exit", style="filled", fillcolor="lightsalmon"];

        subgraph cluster_versions {
            color = "none";
            label = "";
            version_latest [label="\"latest\""];
            version_exact [label="\"=3.7.3\""];
            version_tilde [label="\"~3.7\""];
        }

        subgraph cluster_available_cache {
            label = "Available Versions Cache";
            shape = "rectangle";
            color = "black";
            style = "filled";
            fillcolor = "lightgrey";
            decision_cache_available_versions [label="Which versions\nare available?", shape="diamond"];
            cache_query [label="Query cache"];
            decision_cache_up_to_date [label="Up to date?", shape="diamond"];
            cache_update [label="Update cache"];
            cache_find_compatible [label="Found compatible\nversion?", shape="diamond"];
        }

        subgraph cluster_install {
            label = "Installation";
            shape = "rectangle";
            color = "black";
            style = "filled";
            fillcolor = "lightgrey";
            decision_already_downloaded [label="Already\ndownloaded?", shape="diamond"];
            download [label="Download"];
            decision_valid_checksum [label="Valid\nchecksum/signature?", shape="diamond"];
            decision_already_extracted [label="Already\nextracted?", shape="diamond"];
            extract [label="Extract"];
            configure_make_make_install [label="configure\nmake\nmake install"];
        }

        subgraph cluster_extras_install {
            label = "Extras Installation";
            shape = "rectangle";
            color = "black";
            style = "filled";
            fillcolor = "lightgrey";
            decision_install_extras [label="Install\nextras?", shape="diamond"];
            decision_extras_from_file [label="Install extras\nfrom file?", shape="diamond"];
            extras_from_file [label="Install extras\nfrom file"];
            extras_from_default [label="Install extras\nfrom default file"];
        }
    }

    // ========================================================
    // Transitions

    command_install -> decision_parse_version;

    decision_parse_version -> version_latest;
    decision_parse_version -> version_exact;
    decision_parse_version -> version_tilde;

    cache_query -> decision_cache_up_to_date;
    decision_cache_up_to_date -> cache_find_compatible [label="Yes"];
    decision_cache_up_to_date -> cache_update [label="No"];
    cache_update -> cache_query;

    version_tilde -> decision_cache_available_versions;
    version_latest -> decision_cache_available_versions;
    version_exact -> decision_cache_available_versions;
    decision_cache_available_versions -> cache_query;

    cache_find_compatible -> version [label="Yes"];
    cache_find_compatible -> exit [label="No"];

    version -> decision_already_installed;

    installed_list  -> decision_already_installed;

    decision_already_installed -> decision_force_install [label="Yes"];
    decision_already_installed -> decision_already_downloaded [label="No"];
    decision_force_install -> decision_already_downloaded [label="Yes"];
    decision_force_install -> decision_install_extras [label="No"];

    decision_already_downloaded -> download [label="No"];
    decision_already_downloaded -> decision_valid_checksum [label="Yes"];

    download -> decision_valid_checksum;
    decision_valid_checksum -> decision_already_extracted [label="Yes"];
    decision_valid_checksum -> exit [label="No"];

    decision_already_extracted -> configure_make_make_install [label="Yes"];
    decision_already_extracted -> extract [label="No"];

    extract -> configure_make_make_install;

    configure_make_make_install -> decision_install_extras;
    decision_install_extras -> decision_extras_from_file [label="Yes"];
    decision_install_extras -> decision_write_version_file [label="No"];

    decision_extras_from_file -> extras_from_file;
    decision_extras_from_file -> extras_from_default;
    extras_from_file -> decision_write_version_file;
    extras_from_default -> decision_write_version_file;

    decision_write_version_file -> write_version_file [label="Yes"];
    decision_write_version_file -> exit [label="No"];

    write_version_file -> exit;
}