davidrinnan · August 24, 2021 11:28 · Aug 24, 2021
diff --git a/videowall b/videowall
@@ -0,0 +1,77 @@
+/*
+    A video wall, in Idol they call it Sverigeväggen. A collage of random 
+    viewers who are represented by a low resolution live video. 
+
+    The video audience exists in segments in the current group.
+    There are a maximum of 16 video participants in each segment 
+    Usually we display 48 participants on a video wall which is randomly
+    produced from the available channels, hence the default 3 for numberOfViews. 
+
+    We only fetch segments that have active participants in them. We do not consider
+    empty channels a burden. 
+
+    Task:
+    Since people sometimes leave a channel this creates blanks (ie a channel 
+    may after a while only have 5 participants left). 
+    As part of the process of getting random channels we would also like to 
+    move participants to fill up empty spots. 
+    The worst experience is the display of close to empty groups since this creates 
+    lots of visual gaps in a 48 piece grid, giving the experience there are few participants. 
+
+    Assume there is a function this.moveParticipant(fromChannel, toChannel, pid). 
+    Such a move will happen asynchronously and will take approx 10 seconds. 
+    If a person joins a segment which is currently displayed, the person will pop
+    in nicely in the grid, so dont worry about that. Do however avoid the transfer 
+    of participants FROM currently displayed groups. 
+
+
+    There could be anything from 0 to 100's of channels in a group 
+
+    The getRandomChannels function is usually executed every 60-360 seconds. 
+
+
+
+    What we expect:
+    You can solve the task by explaining the thinking behind it, by pseudo code or actual code. 
+    The important thing is to explain the thinking part. What potential pitfalls do you see and 
+    how do you address them? 
+
+    New participants are always connected to the largest channel with available slots, so they do not need to be considered. 
+    If no slots are available in existing groups, a new group is created. 
+
+*/
+
+
+getRandomChannels (emeetingId, group, numberOfViews = 3, cb) {
+
+    if (!this.channels[group]) {
+        cb && cb('err', null);
+        return;
+    }
+
+    let channels = [];
+
+
+    const segments = Object.keys(this.channels[group]);
+    const availableSegments = segments.filter(segment => {
+        const channel = this.channels[group][segment].channel;
+        return this.inChannel[channel] && Object.keys(this.inChannel[channel]).length
+    });
+
+    let getNbrChannels = numberOfViews;
+
+    while (availableSegments.length && getNbrChannels > 0) {
+        const groupSegment = availableSegments.splice(Math.floor(availableSegments.length * Math.random() | 0), 1)[0];
+
+        channels.push(this.channels[group][groupSegment].channel);
+        --getNbrChannels;
+    } 
+
+    const randomChannels = {
+        emeetingId,
+        channels,
+    };
+
+    cb && cb(null, randomChannels);
+
+}
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