Natur Enemy Castbar - Classic
Classic Era, Hardcore, SoD, TBC Anniversary & Classic MoP - not for retail client.

Introduction
Natur Enemy Castbar is a PvP addon designed around the idea and original addon by Naturfreund.

Select a friendly or hostile target, get mid cast timers, cooldowns, beneficial buffs and more - Timers contain the spell, duration, target or focus information.
Diminish Return tracking, when fighting a player Crowd Controls are limited to 10 second duration and if re-applied in a 18 second window it reduces by half, thereore the 1st cast is 10 seconds, 2nd is 5 seconds, third is 2.5 seconds and 4th the player is immune - once 20 seconds has elapsed you can re-apply the crowd control.
Stealth Class Detection, this will flash the border with a sound if a stealthed hostile player is nearby, giving their name, class and detected spell - muted in neautral cities.
Announce your crowd control application, when it expires or when someone breaks it.
Killing blow sounds for PvP, or questing if you turn it on.
Batman style popup when your hostile target is immune to Crowd Controls or attempts to cast a heal that you can interrupt.
Heal Warning, get warned when your hostile target or focus casts a healing spell that you can interrupt.
fully customisable timer groups, i.e. size, font, texture, position and grow direction - supports LibSharedMedia-3.0 for more customisation.

Diminish Returns
First Application: Full PvP duration (often shorter than PvE tooltip—e.g., Polymorph lasts ~10s vs. 60s).
Second Application (if within the window): 50% duration.
Third Application: 75% reduction (25% duration).
Fourth+ Applications: Immune to that DR category until reset.
A new CC must hit within 15 seconds of the previous effect's END (not cast time). Early breaks (e.g., damage on Polymorph) still start the timer from when it would have ended.

Commands
/natur or /naturcastbar to bring up the options screen, or /natur togglemm to turn the minimap icon on or off.

Repo

https://github.com/Softrix/Natur-Enemy-Castbar

Notes
This has been written from the ground up since so much has changed through the years with the many different game clients and backend API engine changes. If you spot any issues, have feedback or have a great idea for the addon then please join my discord at: https://discord.gg/R6EkZ94TKK and share it there.. id really love to hear from you.