server.R

shinyServer(function(input, output, session) {
    
    spotify_access_token <- reactive({
        get_spotify_access_token()
    })
    
    artist_info <- reactive({
        req(input$artist_search != '')
        search_spotify(input$artist_search, 'artist', authorization = spotify_access_token()) %>% 
            filter(!duplicated(name))
    })
    
    observeEvent(input$artist_search, {
        choices <- artist_info()$name
        names(choices) <- choices
        update_material_dropdown(session, 'select_artist', value = artist_info()$name[1], choices = choices)
    })
    
    output$select_artist_ui <- renderUI({
        req(nrow(artist_info()) > 0)
        tagList(
            htmlOutput('artist_img'),
            withBusyIndicatorUI(
                actionButton('tracks_go', 'Generate plot', class = 'btn-primary')
            ),
            material_switch('artist_autoplay', 'Play song preview on hover', color = '#1ed760'),
            br(),
            uiOutput('artist_chart_song_ui')
        )
    })
    
    selected_artist <- reactive({
        req(nrow(artist_info()) > 0)
        artist_info() %>% 
            filter(name == input$select_artist) %>% 
            filter(popularity == max(popularity))
    })
    
    observeEvent(input$select_artist, {
        
        req(nrow(artist_info()) > 0)
        
        artist_img <- ifelse(!is.na(selected_artist()$images[[1]]$url[1]), selected_artist()$images[[1]]$url[1], 'https://pbs.twimg.com/profile_images/509949472139669504/IQSh7By1_400x400.jpeg')
        
        output$artist_img <- renderText({
            HTML(str_glue('<img src={artist_img} height="200">'))
        })
        
    })
    
    artist_audio_features <- eventReactive(input$tracks_go, {
        df <- get_artist_audio_features(selected_artist()$name, authorization = spotify_access_token()) %>% 
            mutate(album_img = map_chr(1:nrow(.), function(row) {
                .$album_images[[row]]$url[1]
            }))
        if (nrow(df) == 0) {
            stop("Sorry, couldn't find any tracks for that artist's albums on Spotify.")
        }
        return(df)
    })
    
    output$artist_quadrant_chart <- renderHighchart({
        artist_quadrant_chart(artist_audio_features()) %>% 
            hc_add_event_point(event = 'mouseOver')
    })
    
    output$artist_chart_song_ui <- renderUI({
        
        req(input$artist_quadrant_chart_mouseOver, input$artist_autoplay == TRUE)
        
        artist_track_hover <- input$artist_quadrant_chart_mouseOver
        track_preview_url <- artist_audio_features() %>% filter(
            album_name == artist_track_hover$series,
            valence == artist_track_hover$x,
            energy == artist_track_hover$y
        ) %>% pull(track_preview_url)
        
        if (!is.na(track_preview_url)) {
            tagList(
                tags$audio(id = 'song_preview', src = track_preview_url, type = 'audio/mp3', autoplay = NA, controls = NA),
                tags$script(JS("myAudio=document.getElementById('song_preview'); myAudio.play();"))
            )
        } else {
            h5('No preview for this track on Spotify')
        }
    })
    
    observeEvent(input$tracks_go, {
        output$artist_plot <- renderUI({
            if (input$GetScreenWidth >= 800) {
                withSpinner(highchartOutput('artist_quadrant_chart', width = '820px', height = '800px'), type = 5, color = '#1ed760')
            } else {
                withSpinner(highchartOutput('artist_quadrant_chart'), type = 5, color = '#1ed760')
            }
        })
    })
    
})