src/logger.f90: allow changing output unit and colors

src/logger.f90

@@ -10,6 +10,8 @@
 ! The format of the log is: [time] [module:procedure] [level] <message>
 module logger
 
+  use, intrinsic :: iso_fortran_env, only : error_unit
+
   implicit none
 
   ! Log levels
@@ -23,19 +25,27 @@ module logger
 
   ! ANSI escape sequences for colors
   type ansi_colors
-    character(8) :: red    = achar(27) // '[1;31m'
+    character(8) :: red, green, yellow, white, blue, reset
-    character(8) :: green  = achar(27) // '[0;32m'
-    character(8) :: yellow = achar(27) // '[1;33m'
-    character(8) :: white  = achar(27) // '[1;39m'
-    character(8) :: blue   = achar(27) // '[0;34m'
-    character(8) :: reset  = achar(27) // '[0m'
   end type
 
+  type(ansi_colors), parameter :: monochrome = &
+    ansi_colors(red='', green='', yellow='', white='', blue='', reset='')
+
+  type(ansi_colors), parameter :: base16 =      &
+    ansi_colors(red    = achar(27) // '[1;31m', &
+                green  = achar(27) // '[0;32m', &
+                yellow = achar(27) // '[1;33m', &
+                white  = achar(27) // '[1;39m', &
+                blue   = achar(27) // '[0;34m', &
+                reset  = achar(27) // '[0m')
+
+  ! Logger state
   integer(kind(log_level)), save :: current_level = WARNING
-  type(ansi_colors), parameter   :: colors = ansi_colors()
+  integer(kind(log_level)), save :: current_unit  = error_unit
+  type(ansi_colors),        save :: colorscheme   = base16
 
   private
-  public log_message, set_log_level
+  public log_message, set_logger
   public log_error, log_warning, log_info, log_debug
   public log_level, ERROR, WARNING, INFO, DEBUG
 
@@ -48,8 +58,6 @@ contains
     !   mod:    module emitting the message
     !   proc:   procedure emitting the message
 
-    use, intrinsic :: iso_fortran_env, only : error_unit
-
     ! subroutine argument
     character(*),             intent(in) :: msg
     integer(kind(log_level)), intent(in) :: level
@@ -65,7 +73,7 @@ contains
     ! execution time in μs (eg. [0571258])
     call cpu_time(now)
     write (time, '("[",i0.7,"]")') int(now * 1e6)
-    time = trim(colors%blue) // trim(time) // trim(colors%reset)
+    time = trim(colorscheme%blue) // trim(time) // trim(colorscheme%reset)
 
     ! id of the emitter (eg. [program:main])
     id = mod
@@ -74,9 +82,9 @@ contains
     ! kind of message (eg. [warning])
     kind = trim(level_color(level)) // &
            trim(level_name(level))  // &
-           trim(colors%reset)
+           trim(colorscheme%reset)
 
-    write (error_unit, '(a, 2(x,"[",a,"]"), x,a)') &
+    write (current_unit, '(a, 2(x,"[",a,"]"), x,a)') &
       trim(time), trim(id), trim(kind), trim(msg)
 
   end subroutine log_message
@@ -117,21 +125,39 @@ contains
   end subroutine log_debug
 
 
-  subroutine set_log_level(level)
+  subroutine set_logger(level, unit, colored)
-    ! Set the current logging level
+    ! Set the current logging level, log file unit
+    ! and whether to use colored output.
     !
     ! Only messages with a lower level than the current
     ! one will be actually logged.
+    !
+    ! The logger defaults are warning level, output to stderr
+    ! and colors only if the output unit is a terminal.
 
     ! subroutine arguments
-    integer(kind(log_level)), intent(in) :: level
+    integer(kind(log_level)), intent(in), optional :: level
+    integer,                  intent(in), optional :: unit
+    logical,                  intent(in), optional :: colored
     character(25) :: msg
 
+    if (present(unit)) then
+      current_unit = unit
+    end if
+
+    if (present(colored)) then
+      colorscheme = base16
+    else
+      colorscheme = merge(base16, monochrome, isatty(current_unit))
+    end if
+
+    if (present(level)) then
       current_level = level
       msg = 'changed level to ' // trim(level_name(level))
       call log_debug(msg, mod='logger', proc='set_log_level')
+    end if
 
-  end subroutine set_log_level
+  end subroutine set_logger
 
 
   pure function level_color(level) result(escape)
@@ -143,13 +169,13 @@ contains
 
     select case (level)
       case (ERROR)
-        escape = colors%red
+        escape = colorscheme%red
       case (WARNING)
-        escape = colors%yellow
+        escape = colorscheme%yellow
       case (INFO)
-        escape = colors%green
+        escape = colorscheme%green
       case (DEBUG)
-        escape = colors%white
+        escape = colorscheme%white
     end select
 
   end function level_color

src/main.f90

@@ -1,6 +1,6 @@
 program main
   use const_and_precisions, only : wp_
-  use logger,               only : INFO, ERROR, WARNING, set_log_level, log_message
+  use logger,               only : INFO, ERROR, WARNING, set_logger, log_message
   use utils,                only : dirname
   use types,                only : contour
   use gray_cli,             only : cli_options, parse_cli_options, &
@@ -35,7 +35,7 @@ program main
 
   ! Initialise logging
   if (opts%quiet) opts%verbose = ERROR
-  call set_log_level(opts%verbose)
+  call set_logger(level=opts%verbose)
 
   ! Load the parameters from file and move to its directory
   ! (all other filepaths are assumed relative to it)