sequenceDiagram
    title dlPro Event Sequence


    actor user
    create participant background
    user->>background: user clicks extension icon
    background->>content: spawns content
    content->>background: requests cookies
    note over content:creates area for iframe
    create participant iframe
    content->>iframe: creates iframe
    note over iframe:inits primary UI
    background->>content:sends cookies
    content->>iframe:sends download url and cookies
    create participant worker
    iframe->>worker: spawns worker
    iframe->>worker: sends cookies and dlurl
    note over worker: fetches latest yt-dlp
    create participant pyodide
    worker->>pyodide:inits pyodide and libs
    worker->>pyodide:runs yt-dlp
    create participant yt-dlp
    pyodide->>yt-dlp:inits and patches yt-dlp
    pyodide->>yt-dlp:runs extract_info
    note over yt-dlp:see http request section later
    yt-dlp->>pyodide:returns info
    pyodide->>worker:asks user for selection
    worker->>iframe:forwards request
    iframe->>user:presents UI to user
    user->>iframe:makes format selection
    iframe->>worker:sends user selection
    worker->>pyodide:forwards
    pyodide->>yt-dlp:runs yt-dlp downloader
    note over yt-dlp:these sections aren't necessarily ran in this order, or at all
    critical http_request Group ran whenever yt-dlp makes an http request
        create participant pyodide_http_fork
        yt-dlp->>pyodide_http_fork:monkey patched http request
        alt request contains origin header
            note over pyodide_http_fork: origin header can't be faked, must be sent from origin
            pyodide_http_fork->>worker:proxy_fetch
            worker->>content:forwards
            note over content:normal xmlhttprequest
            note over content:requests from here match page's origin
            content->>worker:request result
            worker->>pyodide_http_fork:forwards
        else request does not contain origin header
            alt browser supports atomics
                note over pyodide_http_fork:stream request for better progress indicator
                create participant streaming_worker
                pyodide_http_fork->>streaming_worker:starts request
                note over streaming_worker:fetch request
                streaming_worker->>pyodide_http_fork:sends progress via atomics
                destroy streaming_worker
                streaming_worker->>pyodide_http_fork:sends success/error code
                
            else browser doesn't support atomics
                note over pyodide_http_fork:normal xmlhttprequest
            end
        end
        destroy pyodide_http_fork
        pyodide_http_fork->>yt-dlp:http result
        
    end
    critical JS_challenge ran when page needs advanced JS-based captcha solving

        yt-dlp->>pyodide:hits registered JSC handler
        pyodide->>worker:sends js
        worker->>iframe:forwards
        create participant sandbox
        iframe->>sandbox:creates sandcritical to run arbitrary js
        iframe->>sandbox:sends JS code (patched npm import calls)
        sandbox->>iframe:sends result

        destroy sandbox
        iframe->>sandbox:removes
        
        iframe->>worker:forwards
        worker->>pyodide:forwards
        pyodide->>yt-dlp:returns result

    end

    critical ffmpeg_ffprobe_call ran when media file needs processing
        yt-dlp->>pyodide:monkey patched popen
        pyodide-->>yt-dlp:hardcoded result for basic ffprobe capabilities
        create participant ffmpegwasm
        pyodide->>ffmpegwasm:spawns ffmpegwasm
        pyodide->>ffmpegwasm:loads libs
        pyodide->>ffmpegwasm:copies or moves files
        pyodide->>ffmpegwasm:execute command
        ffmpegwasm->>pyodide:stdout results
        ffmpegwasm->>pyodide:command completed
        ffmpegwasm->>pyodide:pyodide moves files
        note over ffmpegwasm:ffmpeg worker is kept alive if needed again
        destroy ffmpegwasm
        ffmpegwasm -x ffmpegwasm: destroy
    end

    yt-dlp->>pyodide:postprocessor hook is called
    pyodide->>worker:send_to_user
    pyodide->>worker:worker moves files
    worker->>iframe:copies files
    iframe->>user:copies files
    destroy yt-dlp
    yt-dlp->>pyodide:execution finishes
    destroy pyodide
    
    worker->>pyodide:waits for files to finish sending
    destroy worker
    worker-xworker:
    user->>content:requests dlpro close
    destroy iframe
    content->>iframe:removes iframe

    note over content:execution finishes
    destroy content
    content--xcontent: