@startuml

activate mkdwarfs #lightgreen

== Startup Phase ==

mkdwarfs -> script ** : create
return
mkdwarfs -> categorizer_manager ** : create
return
mkdwarfs -> filesystem_writer ** : create
return
mkdwarfs -> segmenter_factory ** : create
return
mkdwarfs -> entry_factory ** : create
return
mkdwarfs -> os_access ** : create
return
mkdwarfs -> scanner ** : create
return
mkdwarfs -> scanner ++ #lightgreen : ""scan()""

scanner -> inode_manager ** : create
scanner -> file_scanner ** : create

== Scanning Phase ==

loop until all files found

    scanner -> os_access ++ #lightgreen : ""opendir()""
    return return dir_reader

    scanner -> entry_factory ++ #lightgreen : ""create()""
    entry_factory -> os_access ++ #lightgreen : ""symlink_info()""
    return
    return return new entry

    alt if ""has_filter()""
        scanner -> script ++ #lightgreen : ""filter()""
        return
    else if ""has_transform()""
        scanner -> script ++ #lightgreen : ""transform()""
        return
    end

    alt if regular file
        scanner -> os_access ++ #lightgreen : ""access(R_OK)""
        return
        alt if file accessible
            scanner -> file_scanner ++ #lightgreen : ""scan()""
            file_scanner --> scanner
        else
            scanner -> scanner ++ #lightgreen : Replace with empty file
            return
        end
    else
        scanner -> entry_factory ++ #lightgreen : ""scan()""
        return
    end

end

scanner -> scanner : Remove empty directories
scanner -> scanner : Assign dir/link inodes
note left
Directories and symbolic
links have been scanned
and are assigned inodes
while file are still scanning.
end note

file_scanner -> os_access ++ #lightgreen : ""map_file()""
return

file_scanner -> entry_factory ++ #lightgreen : ""scan()""
return

file_scanner -> file_scanner : Deduplicate
note right
Both hard links and "regular"
duplicates are handled here.
end note

file_scanner -> inode_manager ++ #lightgreen : ""create_inode()""
return

file_scanner -> inode_manager ++ #lightgreen : ""scan_background()""
inode_manager --> file_scanner

par
    opt
        inode_manager -> inode_manager : Similarity Hashing
    end

    opt
        inode_manager -> categorizer_manager ++ #lightgreen : ""job()""
        return
    end
end

return

scanner -> file_scanner : ""wait()""
return

scanner -> file_scanner ++ #lightgreen : ""finalize()""
return

scanner -> scanner ++ #lightgreen : Build inode tables
return

scanner -> scanner ++ #lightgreen : Build symlink tables
return

== Segmentation/Blockifying Phase ==

scanner -> block_manager ** : create

scanner -> filesystem_writer ++ #lightgreen : ""configure()""
return

loop over all categories

    opt
        scanner -> categorizer_manager ++ #lightgreen : ""category_metadata()""
        return
    end

    scanner -> filesystem_writer ++ #lightgreen : ""get_compression_constraints()""
    return

    par

        scanner -> inode_manager ++ #lightgreen : ""ordered_span()""
        return list of ordered inodes

        scanner -> segmenter_factory ++ #lightgreen : ""create()""

            segmenter_factory -> segmenter ** : create

        return segmenter for this category

        loop over all inodes

            scanner -> os_access ++ #lightgreen : ""map_file()""
            return

            loop over all inode fragments

                scanner -> segmenter ++ #lightgreen : ""add_chunkable()""

                    loop until fragment is segmented

                        segmenter -> filesystem_writer ++ #lightgreen : ""write_block()""
                        return
                        par
                            filesystem_writer -> block_manager ++ #lightgreen : ""set_written_block()""
                            return
                            filesystem_writer -> filesystem_writer ++ #lightgreen : Compress block
                            return
                            filesystem_writer -> filesystem_writer ++ #lightgreen : Write block to output image
                            return
                        end

                    end

                return

            end

        end

        scanner -> segmenter ++ #lightgreen : ""finish()""
        return

        scanner -> filesystem_writer ++ #lightgreen : ""finish_category()""
        return

        destroy segmenter

    end

end

scanner -> scanner ++ #lightgreen : Build chunk table
return

scanner -> block_manager ++ #lightgreen : ""map_logical_blocks()""
return

scanner -> scanner ++ #lightgreen : Build directory table
return

scanner -> scanner ++ #lightgreen : Build shared files table
return

scanner -> filesystem_writer ++ #lightgreen : ""write_metadata_v2_schema()""
return

scanner -> filesystem_writer ++ #lightgreen : ""write_metadata_v2()""
return

scanner -> filesystem_writer ++ #lightgreen : ""flush()""
return

== Shutdown Phase ==

destroy file_scanner
destroy inode_manager
destroy block_manager

return

destroy scanner
destroy os_access
destroy entry_factory
destroy segmenter_factory
destroy filesystem_writer
destroy categorizer_manager
destroy script

@enduml