#[==[

Originally taken from: https://github.com/Kitware/VTK/blob/8485477f9aa41f3c33094c3beb201e747abf5541/CMake/FindFFMPEG.cmake
License: https://github.com/Kitware/VTK/blob/8485477f9aa41f3c33094c3beb201e747abf5541/Copyright.txt

/*=========================================================================

  Program:   Visualization Toolkit
  Module:    Copyright.txt

Copyright (c) 1993-2015 Ken Martin, Will Schroeder, Bill Lorensen
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

 * Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.

 * Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

 * Neither name of Ken Martin, Will Schroeder, or Bill Lorensen nor the names
   of any contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

=========================================================================*/

=========================================================================
 
Provides the following variables:

  * `FFMPEG_INCLUDE_DIRS`: Include directories necessary to use FFMPEG.
  * `FFMPEG_LIBRARIES`: Libraries necessary to use FFMPEG. Note that this only
    includes libraries for the components requested.
  * `FFMPEG_VERSION`: The version of FFMPEG found.

The following components are supported:

  * `avcodec`
  * `avdevice`
  * `avfilter`
  * `avformat`
  * `avresample`
  * `avutil`
  * `swresample`
  * `swscale`

For each component, the following are provided:

  * `FFMPEG_<component>_FOUND`: Libraries for the component.
  * `FFMPEG_<component>_INCLUDE_DIRS`: Include directories for
    the component.
  * `FFMPEG_<component>_LIBRARIES`: Libraries for the component.
  * `FFMPEG::<component>`: A target to use with `target_link_libraries`.

Note that only components requested with `COMPONENTS` or `OPTIONAL_COMPONENTS`
are guaranteed to set these variables or provide targets.
#]==]

function (_ffmpeg_find component headername)
  find_path("FFMPEG_${component}_INCLUDE_DIR"
    NAMES
      "lib${component}/${headername}"
    PATHS
      "${FFMPEG_ROOT}/include"
      "$ENV{CONDA_PREFIX}/include"
      ~/Library/Frameworks
      /Library/Frameworks
      /usr/local/include
      /usr/include
      /sw/include # Fink
      /opt/local/include # DarwinPorts
      /opt/csw/include # Blastwave
      /opt/include
      /usr/freeware/include
    PATH_SUFFIXES
      ffmpeg
    DOC "FFMPEG's ${component} include directory")
  mark_as_advanced("FFMPEG_${component}_INCLUDE_DIR")

  # On Windows, static FFMPEG is sometimes built as `lib<name>.a`.
  if (WIN32)
    list(APPEND CMAKE_FIND_LIBRARY_SUFFIXES ".a" ".lib")
    list(APPEND CMAKE_FIND_LIBRARY_PREFIXES "" "lib")
  endif ()

  find_library("FFMPEG_${component}_LIBRARY"
    NAMES
      "${component}"
    PATHS
      "${FFMPEG_ROOT}/lib"
      "$ENV{CONDA_PREFIX}/lib"
      ~/Library/Frameworks
      /Library/Frameworks
      /usr/local/lib
      /usr/local/lib64
      /usr/lib
      /usr/lib64
      /sw/lib
      /opt/local/lib
      /opt/csw/lib
      /opt/lib
      /usr/freeware/lib64
      "${FFMPEG_ROOT}/bin"
    DOC "FFMPEG's ${component} library")
  mark_as_advanced("FFMPEG_${component}_LIBRARY")

  if (FFMPEG_${component}_LIBRARY AND FFMPEG_${component}_INCLUDE_DIR)
    set(_deps_found TRUE)
    set(_deps_link)
    foreach (_ffmpeg_dep IN LISTS ARGN)
      if (TARGET "FFMPEG::${_ffmpeg_dep}")
        list(APPEND _deps_link "FFMPEG::${_ffmpeg_dep}")
      else ()
        set(_deps_found FALSE)
      endif ()
    endforeach ()
    if (_deps_found)
      if (NOT TARGET "FFMPEG::${component}")
        add_library("FFMPEG::${component}" UNKNOWN IMPORTED)
        set_target_properties("FFMPEG::${component}" PROPERTIES
          IMPORTED_LOCATION "${FFMPEG_${component}_LIBRARY}"
          INTERFACE_INCLUDE_DIRECTORIES "${FFMPEG_${component}_INCLUDE_DIR}"
          IMPORTED_LINK_INTERFACE_LIBRARIES "${_deps_link}")
      endif ()
      set("FFMPEG_${component}_FOUND" 1
        PARENT_SCOPE)

      set(version_header_path "${FFMPEG_${component}_INCLUDE_DIR}/lib${component}/version.h")
      if (EXISTS "${version_header_path}")
        string(TOUPPER "${component}" component_upper)
        file(STRINGS "${version_header_path}" version
          REGEX "#define  *LIB${component_upper}_VERSION_(MAJOR|MINOR|MICRO) ")
        string(REGEX REPLACE ".*_MAJOR *\([0-9]*\).*" "\\1" major "${version}")
        string(REGEX REPLACE ".*_MINOR *\([0-9]*\).*" "\\1" minor "${version}")
        string(REGEX REPLACE ".*_MICRO *\([0-9]*\).*" "\\1" micro "${version}")
        if (NOT major STREQUAL "" AND
            NOT minor STREQUAL "" AND
            NOT micro STREQUAL "")
          set("FFMPEG_${component}_VERSION" "${major}.${minor}.${micro}"
            PARENT_SCOPE)
        endif ()
      endif ()
    else ()
      set("FFMPEG_${component}_FOUND" 0
        PARENT_SCOPE)
      set(what)
      if (NOT FFMPEG_${component}_LIBRARY)
        set(what "library")
      endif ()
      if (NOT FFMPEG_${component}_INCLUDE_DIR)
        if (what)
          string(APPEND what " or headers")
        else ()
          set(what "headers")
        endif ()
      endif ()
      set("FFMPEG_${component}_NOT_FOUND_MESSAGE"
        "Could not find the ${what} for ${component}."
        PARENT_SCOPE)
    endif ()
  endif ()
endfunction ()

_ffmpeg_find(avutil     avutil.h)
_ffmpeg_find(avresample avresample.h
  avutil)
_ffmpeg_find(swresample swresample.h
  avutil)
_ffmpeg_find(swscale    swscale.h
  avutil)
_ffmpeg_find(avcodec    avcodec.h
  avutil)
_ffmpeg_find(avformat   avformat.h
  avcodec avutil)
_ffmpeg_find(avfilter   avfilter.h
  avutil)
_ffmpeg_find(avdevice   avdevice.h
  avformat avutil)

if (TARGET FFMPEG::avutil)
  set(_ffmpeg_version_header_path "${FFMPEG_avutil_INCLUDE_DIR}/libavutil/ffversion.h")
  if (EXISTS "${_ffmpeg_version_header_path}")
    file(STRINGS "${_ffmpeg_version_header_path}" _ffmpeg_version
      REGEX "FFMPEG_VERSION")
    string(REGEX REPLACE ".*\"n?\(.*\)\"" "\\1" FFMPEG_VERSION "${_ffmpeg_version}")
    unset(_ffmpeg_version)
  else ()
    set(FFMPEG_VERSION FFMPEG_VERSION-NOTFOUND)
  endif ()
  unset(_ffmpeg_version_header_path)
endif ()

set(FFMPEG_INCLUDE_DIRS)
set(FFMPEG_LIBRARIES)
set(_ffmpeg_required_vars)
foreach (_ffmpeg_component IN LISTS FFMPEG_FIND_COMPONENTS)
  if (TARGET "FFMPEG::${_ffmpeg_component}")
    set(FFMPEG_${_ffmpeg_component}_INCLUDE_DIRS
      "${FFMPEG_${_ffmpeg_component}_INCLUDE_DIR}")
    set(FFMPEG_${_ffmpeg_component}_LIBRARIES
      "${FFMPEG_${_ffmpeg_component}_LIBRARY}")
    list(APPEND FFMPEG_INCLUDE_DIRS
      "${FFMPEG_${_ffmpeg_component}_INCLUDE_DIRS}")
    list(APPEND FFMPEG_LIBRARIES
      "${FFMPEG_${_ffmpeg_component}_LIBRARIES}")
    if (FFMEG_FIND_REQUIRED_${_ffmpeg_component})
      list(APPEND _ffmpeg_required_vars
        "FFMPEG_${_ffmpeg_required_vars}_INCLUDE_DIRS"
        "FFMPEG_${_ffmpeg_required_vars}_LIBRARIES")
    endif ()
  endif ()
endforeach ()
unset(_ffmpeg_component)

if (FFMPEG_INCLUDE_DIRS)
  list(REMOVE_DUPLICATES FFMPEG_INCLUDE_DIRS)
endif ()

include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(FFMPEG
  REQUIRED_VARS FFMPEG_INCLUDE_DIRS FFMPEG_LIBRARIES ${_ffmpeg_required_vars}
  VERSION_VAR FFMPEG_VERSION
  HANDLE_COMPONENTS)
unset(_ffmpeg_required_vars)
