cmake_minimum_required(VERSION 3.22)

# -----------------------------
# Safely force Clang
# -----------------------------
if(NOT DEFINED CMAKE_C_COMPILER)
    set(CMAKE_C_COMPILER clang CACHE STRING "C compiler" FORCE)
endif()
if(NOT DEFINED CMAKE_CXX_COMPILER)
    set(CMAKE_CXX_COMPILER clang++ CACHE STRING "C++ compiler" FORCE)
endif()

# -----------------------------
# Project setup
# -----------------------------
project(advent-of-code
    LANGUAGES CXX
    VERSION 2025.12
)

set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type")

# -----------------------------
# Dependencies
# -----------------------------
add_subdirectory(external/fmt)
add_subdirectory(external/spdlog)

set(COMMON_LIBS fmt::fmt spdlog::spdlog)

# -----------------------------
# 1. Collect ALL .cpp files under src/
# -----------------------------
file(GLOB_RECURSE ALL_CPP_FILES
    RELATIVE ${CMAKE_CURRENT_SOURCE_DIR}
    "src/*.cpp"
)

# -----------------------------
# 2. Separate day solution mains from everything else
# -----------------------------
set(DAY_MAIN_PATTERN "^day-[0-9]+-solution\\.cpp$")

set(DAY_MAINS "")
set(COMMON_SOURCES "")

foreach(file ${ALL_CPP_FILES})
    get_filename_component(fname ${file} NAME)
    if(fname MATCHES ${DAY_MAIN_PATTERN})
        list(APPEND DAY_MAINS "${CMAKE_CURRENT_SOURCE_DIR}/${file}")
    else()
        list(APPEND COMMON_SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/${file}")
    endif()
endforeach()

# -----------------------------
# 3. Include directories (all subfolders under src/)
# -----------------------------
file(GLOB_RECURSE SRC_SUBDIRS LIST_DIRECTORIES true "src/*")
set(PROJECT_INCLUDE_DIRS "")
foreach(dir ${SRC_SUBDIRS})
    if(IS_DIRECTORY ${dir})
        list(APPEND PROJECT_INCLUDE_DIRS ${dir})
    endif()
endforeach()

# -----------------------------
# 4. Common code → object library (only if we actually have common files)
# -----------------------------
if(COMMON_SOURCES)
    add_library(common_objects OBJECT ${COMMON_SOURCES})
    target_include_directories(common_objects PRIVATE ${PROJECT_INCLUDE_DIRS})
    target_link_libraries(common_objects PRIVATE ${COMMON_LIBS})
    target_compile_features(common_objects PRIVATE cxx_std_23)
else()
    # Create a dummy interface target so the rest of the script stays simple
    add_library(common_objects INTERFACE)
    message(STATUS "No common source files found – each day will compile independently")
endif()

# -----------------------------
# 5. Build one executable per day solution
# -----------------------------
foreach(MAIN_FILE ${DAY_MAINS})
    get_filename_component(MAIN_NAME ${MAIN_FILE} NAME_WE)      # day-1-solution
    set(EXE_NAME "aoc-${MAIN_NAME}")

    add_executable(${EXE_NAME} ${MAIN_FILE})

    # If we have common_objects as OBJECT library → reuse compiled objects
    # Otherwise it's just an INTERFACE → nothing added
    if(COMMON_SOURCES)
        target_sources(${EXE_NAME} PRIVATE $<TARGET_OBJECTS:common_objects>)
    endif()

    target_include_directories(${EXE_NAME} PRIVATE ${PROJECT_INCLUDE_DIRS})
    target_link_libraries(${EXE_NAME} PRIVATE ${COMMON_LIBS} common_objects)
    target_compile_features(${EXE_NAME} PRIVATE cxx_std_23)

    # Warnings + optimizations
    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang|GNU")
        target_compile_options(${EXE_NAME} PRIVATE
            -Wall -Wextra -Wpedantic -Wconversion -Wshadow -Wformat=2 -Werror=main
        )
    endif()

    target_compile_options(${EXE_NAME} PRIVATE -O3 -march=native)
    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang|GNU")
        target_link_options(${EXE_NAME} PRIVATE -flto=auto)
    endif()
endforeach()

# -----------------------------
# Final summary
# -----------------------------
list(LENGTH DAY_MAINS DAY_COUNT)
message(STATUS "Advent of Code 2025 – Building ${DAY_COUNT} solution(s):")
foreach(MAIN ${DAY_MAINS})
    get_filename_component(NAME ${MAIN} NAME)
    message(STATUS "   • ${NAME} → aoc-${NAME_WE}")
endforeach()

if(NOT DAY_MAINS)
    message(FATAL_ERROR "No files matching 'day-N-solution.cpp' found in src/ – nothing to build!")
endif()