cmake_minimum_required(VERSION 3.21)
project(kpnpp VERSION 0.1.0 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

option(KPN_BUILD_TESTS    "Build tests"                              ON)
option(KPN_BUILD_PYTHON   "Build Python bindings (requires nanobind)" ON)
option(KPN_BUILD_EXAMPLES "Build examples"                            ON)
option(KPN_WEB_DEBUG      "Enable web debug UI (cpp-httplib)"         OFF)

# Sanitizer build. Empty = off. Accepts "thread", "address", "undefined",
# or a combination like "address,undefined". Applied to all kpn targets via
# the kpn_sanitizer_flags() helper below.
#
# The lock-free SPSC Channel<T> (include/kpn/channel.hpp) has hand-reasoned
# acquire/release ordering; -DKPN_SANITIZER=thread + the channel stress test
# (tests/test_channel_stress.cpp) is the dynamic half of verifying it. The
# static half is the CDSChecker model-check harness (see verify/).
set(KPN_SANITIZER "" CACHE STRING
    "Build with sanitizer: thread | address | undefined | <combo> (empty = off)")

# Translate KPN_SANITIZER into compile/link flags. No-op when empty.
function(kpn_sanitizer_flags out_var)
    if(KPN_SANITIZER)
        set(${out_var}
            -fsanitize=${KPN_SANITIZER}
            -fno-omit-frame-pointer
            -g
            PARENT_SCOPE)
    else()
        set(${out_var} "" PARENT_SCOPE)
    endif()
endfunction()

# ── Core library (header-only) ────────────────────────────────────────────────
add_library(kpn INTERFACE)
target_include_directories(kpn INTERFACE
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
    $<INSTALL_INTERFACE:include>
)
target_compile_features(kpn INTERFACE cxx_std_20)

# Threads required by node/channel implementation
find_package(Threads REQUIRED)
target_link_libraries(kpn INTERFACE Threads::Threads)

# ── Web debug UI (optional) ───────────────────────────────────────────────────
if(KPN_WEB_DEBUG)
    include(FetchContent)
    FetchContent_Declare(
        cpp-httplib
        GIT_REPOSITORY https://github.com/yhirose/cpp-httplib.git
        GIT_TAG        v0.18.0
    )
    FetchContent_MakeAvailable(cpp-httplib)
    # httplib made available but NOT forced onto kpn interface — targets opt in
    # by defining KPN_WEB_DEBUG=1 and linking httplib::httplib themselves.
    # This prevents tests and other examples from pulling in the HTTP server.
endif()

# Convenience function for targets that want web debug
function(kpn_target_enable_web_debug target)
    target_compile_definitions(${target} PRIVATE KPN_WEB_DEBUG=1)
    target_link_libraries(${target} PRIVATE httplib::httplib)
endfunction()

# ── Tests ─────────────────────────────────────────────────────────────────────
if(KPN_BUILD_TESTS)
    enable_testing()
    add_subdirectory(tests)
endif()

# ── Benchmarks ────────────────────────────────────────────────────────────────
option(KPN_BUILD_BENCHMARKS "Build benchmarks" OFF)
if(KPN_BUILD_BENCHMARKS)
    add_subdirectory(benchmarks)
endif()

# ── Python bindings ───────────────────────────────────────────────────────────
if(KPN_BUILD_PYTHON)
    find_package(Python 3.8 COMPONENTS Interpreter Development.Module REQUIRED)
    find_package(nanobind CONFIG QUIET)
    if(NOT nanobind_FOUND)
        # Fall back to FetchContent if nanobind not installed system-wide
        include(FetchContent)
        FetchContent_Declare(
            nanobind
            GIT_REPOSITORY https://github.com/wjakob/nanobind.git
            GIT_TAG        v2.12.0
        )
        FetchContent_MakeAvailable(nanobind)
    endif()
    add_subdirectory(python)
endif()

# ── Examples ──────────────────────────────────────────────────────────────────
if(KPN_BUILD_EXAMPLES)
    add_subdirectory(examples)
endif()

# ── Docs (README generation) ──────────────────────────────────────────────────
find_package(Python3 QUIET COMPONENTS Interpreter)
if(Python3_FOUND)
    add_custom_target(docs
        COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/scripts/render_readme.py
        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
        COMMENT "Rendering README.md from README.md.in"
        VERBATIM
    )
endif()