! Estimate wind power 

!========= main program =============
program windpowermain

! declare variables
  implicit none							!enforce strong typing
  real :: power = 0.0					!power (W) outout from turbine
  integer, parameter :: maxlines = 120  !max sounding lines that can be captured
  real, dimension(maxlines) :: zmsl		!array of heights MSL (m)
  real, dimension(maxlines) :: speed	!array of wind speed (knots)
  character (len=100), dimension(maxlines) :: sounding	  !holds the whole sounding
  
!set up
  call welcome
  call getturbinespecs
  call getsounding

!compute wind power
  call findpower

!save results
  call saveresults
  write(*,*) "power = ", power			!display result
  
end program windpowermain




!=======================================
subroutine welcome
  implicit none							!enforce strong typing
  write(*,*)
  write(*,*) "Welcome to Wind Power"
end subroutine welcome


!=======================================
subroutine getturbinespecs
  implicit none							!enforce strong typing
  real :: zhub = 80.0			!hub height of turbine (m) AGL
  real :: r = 30.0				!radius of turbine blade (m)
  
  write(*,*)
  write(*,*) "getturbinespecs: Get specifications of the wind turbine."
  write(*,"(a)", advance="no") "   Enter hub height (m) AGL: "
  read(*,*) zhub
  write(*,"(a)", advance="no") "   Enter turbine radius (m): "
  read(*,*) r
  
  do while ( r .ge. zhub )	!give user multiple chances to enter correct radius
    write(*,*) "    ERROR: turbine radius must be less than the hub height AGL."
    write(*,"(a)", advance="no") "   Enter turbine radius (m): "
    read(*,*) r
  enddo
  
  write(*,*) "  OK: hub height (m) AGL = ",zhub,"   and radius (m) = ",r
  
end subroutine getturbinespecs


!=======================================
subroutine getsounding
  implicit none							!enforce strong typing
  character (len=50) :: filename  	!holds name of sounding file
  character (len=100) :: line		!one line in the sounding file
  integer :: ero					!error flag for opening a file
  integer :: err					!error flag for reading a file
  integer :: i						!dummy counter variable

!Get the file name from user  
  write(*,*)
  write(*,*) "getsounding:  Get the file holding the input sounding"
  write(*,"(a)",advance="no") "   Enter the name of the sounding file: "
  read(*,*) filename
  write(*,*) "    OK: Sounding file name is: ",filename

!Open the file  
  open(1, file=filename, status="old", action="read", iostat=ero)	!open file holding the sounding
!   write(*,*) "    Error flag = ", ero				!display the file-opening error flag (0 = no error)
	if (ero .ne. 0) then			!can't open the file
	  write(*,*) "  Sorry.  Can't find the file: ", filename
	  write(*,*) "    Don't forget to add a suffix .txt if needed."
	  stop "Bye."
	else							!successfully opened the file
	  write(*,*) "  Good.  Successfully opened file: ", filename
	  write(*,*)
	endif

!Make first pass thru file, and echo contents to screen
  write(*,*) "======================================="
  do								!read all lines in the file
    read(1,"(a)", iostat=err) line	!try to read a line
    if ( err .ne. 0  )  exit		!couldn't read the line, perhaps because reached end of file
    write(*,"(a)") line				!successfully read the line, so echo on screen
  enddo
  write(*,*) "======================================="
  write(*,*)

!Make second pass thru file, to read the data
  rewind(1)							!reset file to the beginning
  
  write(*,*)
  write(*,*) "  Skipping past the 5 header lines."
  do i = 1,5						!skip the first 5 header lines in the file
    read(1,"(a)", iostat=err) line	!try to read a line
    if ( err .ne. 0  )  stop "Bye.  Unable to read past the header lines."
    write(*,"(a)") line				!successfully read the line, so echo on screen
  enddo
  
  close(1)							!close the sounding file
    
end subroutine getsounding


!=======================================
subroutine findpower
  implicit none							!enforce strong typing
  write(*,*)
  write(*,*) "findpower:  Calculate the wind power."
end subroutine findpower


!=======================================
subroutine saveresults
  implicit none							!enforce strong typing
  write(*,*)
  write(*,*) "saveresults:  Write to disk and screen the wind power potential"
  write(*,*)
end subroutine saveresults


!======end