GitFOSS

require "./vga.cr"

lib KernelShim
  # External assembly ISR for timer
  fun timer_isr_common : Void
  fun outb(port : UInt16, value: UInt8) : Void
end

# Timer module - System timer
module Timer
  TIMER_FREQ = 1000_u32
  
  @@tick_count : UInt64 = 0
  class_property tick_count

  def self.init : Nil
    # PIT channel 0, mode 3 (square wave), lobyte/hibyte access
    KernelShim.outb(0x43, 0x36)
    # Frequency: 1193182 Hz / divisor = desired frequency (e.g., 100 Hz)
    divisor = 11931 # 1193182 / 100 ≈ 11931
    KernelShim.outb(0x40, divisor & 0xFF)
    KernelShim.outb(0x40, (divisor >> 8) & 0xFF)
    
    # Set up PIT or HPET here (placeholder)
    VGA.puts("Timer initialized!\n")
  end
  
  def self.irq_handler(data : UInt8)
    @@tick_count += 1
    # Could print a dot or update something; for now just increment.
  end
end