# - Find flex executable and provides a macro to generate custom build rules
#
# The module defines the following variables:
#  FLEX_FOUND - true is flex executable is found
#  FLEX_EXECUTABLE - the path to the flex executable
#  FLEX_VERSION - the version of flex
#  FLEX_LIBRARIES - The flex libraries
#
# If flex is found on the system, the module provides the macro:
#  FLEX_TARGET(Name FlexInput FlexOutput [COMPILE_FLAGS <string>])
# which creates a custom command  to generate the <FlexOutput> file from
# the <FlexInput> file.  If  COMPILE_FLAGS option is specified, the next
# parameter is added to the flex  command line. Name is an alias used to
# get  details of  this custom  command.  Indeed the  macro defines  the
# following variables:
#  FLEX_${Name}_DEFINED - true is the macro ran successfully
#  FLEX_${Name}_OUTPUTS - the source file generated by the custom rule, an
#  alias for FlexOutput
#  FLEX_${Name}_INPUT - the flex source file, an alias for ${FlexInput}
#
# Flex scanners oftenly use tokens  defined by Bison: the code generated
# by Flex  depends of the header  generated by Bison.   This module also
# defines a macro:
#  ADD_FLEX_BISON_DEPENDENCY(FlexTarget BisonTarget)
# which  adds the  required dependency  between a  scanner and  a parser
# where  <FlexTarget>  and <BisonTarget>  are  the  first parameters  of
# respectively FLEX_TARGET and BISON_TARGET macros.
#
#  ====================================================================
#  Example:
#
#   find_package(BISON)
#   find_package(FLEX)
#
#   BISON_TARGET(MyParser parser.y ${CMAKE_CURRENT_BINARY_DIR}/parser.cpp
#   FLEX_TARGET(MyScanner lexer.l  ${CMAKE_CURRENT_BIANRY_DIR}/lexer.cpp)
#   ADD_FLEX_BISON_DEPENDENCY(MyScanner MyParser)
#
#   include_directories(${CMAKE_CURRENT_BINARY_DIR})
#   add_executable(Foo
#      Foo.cc
#      ${BISON_MyParser_OUTPUTS}
#      ${FLEX_MyScanner_OUTPUTS}
#   )
#  ====================================================================

#=============================================================================
# Copyright 2009 Kitware, Inc.
# Copyright 2006 Tristan Carel
#
# Distributed under the OSI-approved BSD License (the "License");
# see accompanying file Copyright.txt for details.
#
# This software is distributed WITHOUT ANY WARRANTY; without even the
# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the License for more information.
#=============================================================================
# (To distributed this file outside of CMake, substitute the full
#  License text for the above reference.)

FIND_PROGRAM(FLEX_EXECUTABLE flex DOC "path to the flex executable")
MARK_AS_ADVANCED(FLEX_EXECUTABLE)

FIND_LIBRARY(FL_LIBRARY NAMES fl
  DOC "path to the fl library")
MARK_AS_ADVANCED(FL_LIBRARY)
SET(FLEX_LIBRARIES ${FL_LIBRARY})

IF(FLEX_EXECUTABLE)

  EXECUTE_PROCESS(COMMAND ${FLEX_EXECUTABLE} --version
    OUTPUT_VARIABLE FLEX_version_output
    ERROR_VARIABLE FLEX_version_error
    RESULT_VARIABLE FLEX_version_result
    OUTPUT_STRIP_TRAILING_WHITESPACE)
  IF(NOT ${FLEX_version_result} EQUAL 0)
    MESSAGE(SEND_ERROR "Command \"${FLEX_EXECUTABLE} --version\" failed with output:\n${FLEX_version_error}")
  ELSE()
    STRING(REGEX REPLACE "^flex (.*)$" "\\1"
      FLEX_VERSION "${FLEX_version_output}")
  ENDIF()

  #============================================================
  # FLEX_TARGET (public macro)
  #============================================================
  #
  MACRO(FLEX_TARGET Name Input Output)
    SET(FLEX_TARGET_usage "FLEX_TARGET(<Name> <Input> <Output> [COMPILE_FLAGS <string>]")
    IF(${ARGC} GREATER 3)
      IF(${ARGC} EQUAL 5)
        IF("${ARGV3}" STREQUAL "COMPILE_FLAGS")
          SET(FLEX_EXECUTABLE_opts  "${ARGV4}")
          SEPARATE_ARGUMENTS(FLEX_EXECUTABLE_opts)
        ELSE()
          MESSAGE(SEND_ERROR ${FLEX_TARGET_usage})
        ENDIF()
      ELSE()
        MESSAGE(SEND_ERROR ${FLEX_TARGET_usage})
      ENDIF()
    ENDIF()

    ADD_CUSTOM_COMMAND(OUTPUT ${Output}
      COMMAND ${FLEX_EXECUTABLE}
      ARGS ${FLEX_EXECUTABLE_opts} -o${Output} ${Input}
      DEPENDS ${Input}
      COMMENT "[FLEX][${Name}] Building scanner with flex ${FLEX_VERSION}"
      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})

    SET(FLEX_${Name}_DEFINED TRUE)
    SET(FLEX_${Name}_OUTPUTS ${Output})
    SET(FLEX_${Name}_INPUT ${Input})
    SET(FLEX_${Name}_COMPILE_FLAGS ${FLEX_EXECUTABLE_opts})
  ENDMACRO(FLEX_TARGET)
  #============================================================


  #============================================================
  # ADD_FLEX_BISON_DEPENDENCY (public macro)
  #============================================================
  #
  MACRO(ADD_FLEX_BISON_DEPENDENCY FlexTarget BisonTarget)

    IF(NOT FLEX_${FlexTarget}_OUTPUTS)
      MESSAGE(SEND_ERROR "Flex target `${FlexTarget}' does not exists.")
    ENDIF()

    IF(NOT BISON_${BisonTarget}_OUTPUT_HEADER)
      MESSAGE(SEND_ERROR "Bison target `${BisonTarget}' does not exists.")
    ENDIF()

    SET_SOURCE_FILES_PROPERTIES(${FLEX_${FlexTarget}_OUTPUTS}
      PROPERTIES OBJECT_DEPENDS ${BISON_${BisonTarget}_OUTPUT_HEADER})
  ENDMACRO(ADD_FLEX_BISON_DEPENDENCY)
  #============================================================

ENDIF(FLEX_EXECUTABLE)

INCLUDE(FindPackageHandleStandardArgs)
FIND_PACKAGE_HANDLE_STANDARD_ARGS(FLEX DEFAULT_MSG FLEX_EXECUTABLE)

# FindFLEX.cmake ends here