# Keeps include/plot/plot.hpp honest against the plan's Global Constraints:
# every public header under include/plot/ must be included by the umbrella, and
# every <plot/...> the umbrella names must be a file that actually exists.
#
# "Public" is everything the recursive glob finds except the macro-gated
# */detail/ instrumentation, which is documented as not part of the surface and
# deliberately stays out of the umbrella.
#
# Runs twice: tests/CMakeLists.txt includes it at configure time (so a header
# added without its umbrella line stops the configure rather than the run), and
# ctest runs it again as `plot_umbrella_covers_public_headers` via `cmake -P`.
# Both read the same file so a header the build sees is a header this checks --
# there is no hand-maintained list to fall out of date.
#
# Inputs (set by the including scope, or passed with -D in script mode):
#   PLOT_INCLUDE_DIR  the installed-header root, e.g. <source>/include
#   PLOT_UMBRELLA     the umbrella header, e.g. <PLOT_INCLUDE_DIR>/plot/plot.hpp

if(NOT DEFINED PLOT_INCLUDE_DIR)
  message(FATAL_ERROR "plot: PLOT_INCLUDE_DIR is not set")
endif()
if(NOT DEFINED PLOT_UMBRELLA)
  set(PLOT_UMBRELLA "${PLOT_INCLUDE_DIR}/plot/plot.hpp")
endif()

file(GLOB_RECURSE plot_umbrella_headers
  RELATIVE "${PLOT_INCLUDE_DIR}"
  "${PLOT_INCLUDE_DIR}/plot/*.hpp")
list(SORT plot_umbrella_headers)
file(READ "${PLOT_UMBRELLA}" plot_umbrella_text)

# The umbrella is a public header too, but it cannot include itself.
file(RELATIVE_PATH plot_umbrella_relative "${PLOT_INCLUDE_DIR}" "${PLOT_UMBRELLA}")

# Every other public header is named by the umbrella.
set(plot_umbrella_missing "")
foreach(header IN LISTS plot_umbrella_headers)
  if(header MATCHES "/detail/" OR header STREQUAL plot_umbrella_relative)
    continue()
  endif()
  string(FIND "${plot_umbrella_text}" "#include <${header}>" plot_umbrella_pos)
  if(plot_umbrella_pos EQUAL -1)
    list(APPEND plot_umbrella_missing "${header}")
  endif()
endforeach()

if(plot_umbrella_missing)
  string(REPLACE ";" "\n  " plot_umbrella_missing_text "${plot_umbrella_missing}")
  message(FATAL_ERROR
    "plot: ${PLOT_UMBRELLA} does not include every public header under "
    "include/plot/ -- missing:\n  ${plot_umbrella_missing_text}\n"
    "Add each as `#include <plot/...>`, or move it under a */detail/ directory "
    "if it is implementation-only and not part of the public surface.")
endif()

# And every header the umbrella names is a file that exists (a rename or a
# deleted header cannot leave a dangling include behind).
string(REGEX MATCHALL "#include <plot/[^>]+>" plot_umbrella_includes "${plot_umbrella_text}")
set(plot_umbrella_dangling "")
foreach(plot_umbrella_include IN LISTS plot_umbrella_includes)
  string(REGEX REPLACE "#include <([^>]+)>" "\\1" plot_umbrella_header "${plot_umbrella_include}")
  if(NOT EXISTS "${PLOT_INCLUDE_DIR}/${plot_umbrella_header}")
    list(APPEND plot_umbrella_dangling "${plot_umbrella_header}")
  endif()
endforeach()

if(plot_umbrella_dangling)
  string(REPLACE ";" "\n  " plot_umbrella_dangling_text "${plot_umbrella_dangling}")
  message(FATAL_ERROR
    "plot: ${PLOT_UMBRELLA} includes headers that do not exist under "
    "include/plot/:\n  ${plot_umbrella_dangling_text}")
endif()

list(LENGTH plot_umbrella_headers plot_umbrella_header_count)
message(STATUS
  "plot: umbrella covers every public header (${plot_umbrella_header_count} headers globbed)")