Has anybody developed their own analysis tool / how to get price data

I am contemplating developing a desktop app for myself to perform chart analysis. I wondered whether anybody has done something similar. I want to find the easiest and best source of free price data (just open/close/high/low).

At the moment I’ve developed some complex scripts in Tradingview but the problem with those is that I have to look at each company’s chart to see the analysis/indicators and signals.

Basically I want to create a stock screener that can analyse the price data for all companies on a watchlist that I give it and create buy/sell signals. I don’t want to automate trades so not looking to connect it to a trading bot.

One option would be if there is a site where you can create your own complex screener if it has access to all of the price data.

My scripts aren’t based on standard indicators so I can’t just run a standard indicator against a set of companies.

Any suggestions either for a platform that allows you to create something to analyse price data for multiple companies or a source of price data via an easy to use api/interface.

If anybody has done anything similar and can share the code with me that would be even better (I don’t need the code for the analysis bit just the part that gets and processes the price data).