redef class CCompilationUnit
	# Compile as `_ffi` files which contains the implementation of extern methods
	fun write_as_impl(mmodule: MModule, compdir: String)
	do
		var base_name = "{mmodule.c_name}._ffi"

		var h_file = "{base_name}.h"
		var guard = "{mmodule.c_name.to_upper}_NIT_H"
		write_header_to_file(mmodule, "{compdir}/{h_file}", ["<stdint.h>"], guard)

		var c_file = "{base_name}.c"
		write_body_to_file(mmodule, "{compdir}/{c_file}", ["<stdlib.h>", "<stdio.h>", "<stdint.h>", "\"{h_file}\""])

		files.add( "{compdir}/{c_file}" )
	end

	# Write the header part to `file` including all `includes` using the `guard`
	fun write_header_to_file(mmodule: MModule, file: String, includes: Array[String], guard: String)
	do
		var stream = new FileWriter.open( file )

		# header comments
		var module_info = "/*\n\tExtern implementation of Nit module {mmodule.name}\n*/\n"

		stream.write( module_info )

		stream.write( "#ifndef {guard}\n" )
		stream.write( "#define {guard}\n\n" )

		for incl in includes do stream.write( "#include {incl}\n" )

		compile_header_core( stream )

		# header file guard close
		stream.write( "#endif\n" )
		stream.close
	end

	# Write the body part to `file` including all `includes`
	fun write_body_to_file(mmodule: MModule, file: String, includes: Array[String])
	do
		var stream = new FileWriter.open(file)

		var module_info = "/*\n\tExtern implementation of Nit module {mmodule.name}\n*/\n"

		stream.write( module_info )
		for incl in includes do stream.write( "#include {incl}\n" )

		compile_body_core( stream )

		stream.close
	end
end

redef class CCompilationUnit
	# Similar to `add_local_function` but not `static`
	#
	# Used when the signature contains a visibility attribute.
	private fun add_non_static_local_function(c_function: CFunction)
	do
		body_decl.add c_function.signature
		body_decl.add ";\n"

		body_impl.add "\n"
		body_impl.add c_function.to_writer
	end
end

redef class CCompilationUnit
	# Compile a `_nitni` files, used to implement nitni features for the compiler
	fun write_as_nitni(mmodule: MModule, compdir: String)
	do
		var base_name = "{mmodule.c_name}._nitni"

		var h_file = "{base_name}.h"
		write_header_to_file( mmodule, "{compdir}/{h_file}", new Array[String],
			"{mmodule.c_name.to_s.to_upper}_NITG_NITNI_H")

		var c_file = "{base_name}.c"
		write_body_to_file( mmodule, "{compdir}/{c_file}", ["\"{h_file}\""] )

		files.add( "{compdir}/{c_file}" )
	end
end

redef class CCompilationUnit
	# Write this compilation unit as the API of a foreign code library
	private fun write_as_foreign_lib_api(mmodule: MModule, compdir: String)
	do
		# The FFI expects the support header to end with `._nitni.h`
		var base_name = mmodule.c_name + "._nitni"
		var guard = mmodule.c_name.to_s.to_upper + "_API_H"
		var header_comment = """
/*
	Public API to foreign code of the Nit module {{{mmodule.name}}}
*/
"""

		# Header file
		var h_file = base_name+".h"
		var stream = new FileWriter.open(compdir/h_file)
		stream.write header_comment
		stream.write """
#ifndef {{{guard}}}
#define {{{guard}}}
"""
		compile_header_core stream
		stream.write """

#endif
"""
		stream.close

		# Body file
		var c_file = base_name+".c"
		stream = new FileWriter.open(compdir/c_file)
		stream.write header_comment
		stream.write """
#include "{{{h_file}}}"
"""
		compile_body_core stream
		stream.close

		# Only the C files needs compiling
		files.add compdir / c_file
	end
end