Am thinking phone is trash

This is not a One X, just HTC One. Purchased through AT&T several years ago. Battery is sealed into phone. It was dead, I plugged it in to a wall charger, & left it off. Hours later, phone would only give me a black (blank) screen when turned on, and never went off until I held down the power button. I've tried the "bright light in the upper left (and right) corners without any change. Holding volume and power buttons down, I get the HTC logo screen for about 3 or 4 seconds, then blank screen again. I have to hold down volume and power to turn it off. I've also had the DOS screen up, chose "recovery" and "factory reset", and neither would do anything. Like my title says...I'm thinking it's trash.