[WIP] optimize filtering masjid using geofencing

[adsau59]

Motivation

Currently all masjids are fetched and shown in order of distances which isn't scalable when alot of masjids are added down the line

to solve this issue, we can filter out the list of masjids from the backend so that client doesn't have to do any calculation and simply can render the masjids directly

this can be achieved by following steps

1. client sends request to get masjid using its own geo location
2. using the coordinates server checks for a pre filtered list of masjid form a nearby location
3. if it doesn't exist, it filters using better yet the area being displayed in the map
4. then it returns the list, using which client can sort and calculate exact distance on their own

Design

• if the user is way too zoomed out, we do nothing
• if the user zooms out alot, we just show the cluster location
• if they are zoomed in, we filter through the closest cluster, and filter out masjids using simple distance check using the incircle radius as the threshold
• then we return out the result
• then we search again when the map is moved again

Implementation

• We maintain clusters of masjids for areas,
• when a new masjid is added, its added to a cluster, if no suitable cluster is found, it creates a new one (using radius and thresholds)
• if a masjid is added, cluster location is recalculated as its center would have changed
• we create two functions for the client to request
  • find clusters in a region
  • find masjids in a region of a cluster
• to create both the filters we will need a function to find if a point is inside a rect
• once we have the function, we just need to filter out the things
• maybe cache to save more time for future requests which are very close by

Breakdown

• [x] #45
• [x] create logic to get callback only when region stops moving
• [ ] create function to filter masjids
  • [ ] create table for clusters(center_location,radius,masjids)
  • [ ] create function to add a masjid
    • [ ] research some clustering algorthm
    • [ ] find nearest cluster to masjid (use max threshold distance, radius?)
    • [ ] if not found create a new cluster
    • [ ] calculate new cluster (center) with the new masjid in it
  • [ ] filtering using rect
    • [ ] create a generic function to: find if a point is inside a rect
    • [ ] fetch all cluster in an area
    • [ ] fetch all masjid in an area from a cluster
  • [ ] integrate the function to show the pins
• [ ] integrate the function to show the pins

[adsau59]

laptop had issues for sometime, just completed the project setup... will continue with the task now

[adsau59]

• what happens if the user zooms out alot? doesn't make sense to return all the masjids
  • one solution is to not show anything if they zoom to much out
  • what should be threshold for the region delta then?
• how should we filter the masjids?
  • most straight forward way to do is, point inside polygon: https://stackoverflow.com/a/2752753
  • an optimized way we can do is, make the map view a square, then calculate the radius of the incircle, and simply compare radius for each of the masjids
  • Do we do this for every masjid? or do we filter out the masjids before hand somehow?
    • for this we will need to maintain clusters of masjid in cache, and first test which cluster is the nearest
    • we can even use this cluster when the user zooms out of the map
• Final Plan:
  • We maintain clusters of masjids for areas,
  • if the user zooms out alot, we just show the cluster location
  • if they are zoomed in, we filter through the closest cluster, and filter out masjids using simple distance check using the incircle radius as the threshold
  • then we return out the result
  • then we search again when the map is moved again

[adsau59]

create logic to get callback only when region stops moving

there was already a callback onRegionChangeComplete which does that

[adsau59]

there are two ways to do it

• through supabase tables
• through edge functions

will try through tables first