#!/usr/bin/env v

import os
import rand
import strings

/*
	This is a C bindings generator for netio module.

	This script uses the C preprocessor (`cc`) to extract macros using programs
	from `cincludes` and generates a V module file with constants.

	The C defines (`#define`) are parsed and used to generate a temporary
	V program (`vprogram`), which generates the final V module file.

	The goal is for the final V module file to contain only the values of C
	constants, rather than calling C code directly.
*/

const cincludes = {
	'Linux':   '
		|#include <netinet/in.h>
		|#include <sys/socket.h>
		|#include <netdb.h>'
	'FreeBSD': '
		|#include <netinet/in.h>
		|#include <sys/socket.h>
		|#include <netdb.h>'
}

const typemap = {
	'SocketType':   ['SOCK_']
	'SocketLevel':  ['SOL_', 'IPPROTO_']
	'SocketOption': ['SO_', 'IP_', 'IPV6_']
	'AddrFamily':   ['AF_']
	'AddrInfoFlag': ['AI_']
	'NameInfoFlag': ['NI_']
	'MsgFlag':      ['MSG_']
}

const vprogram = r'module main

%includes

fn main() {
	// Generate the final .v file
	println("module netio\n")
	println("/*")
	println("\tThis file is generated by make.vsh, DO NOT EDIT.")
	println("*/\n")
	for k, v in cdefs {
		println("pub const ${k} = ${v.vtype}(${v.value})")
	}
}

struct CDef {
	vtype string
	value isize
}
'

const cc = 'cc'
const cflags = os.getenv('CFLAGS')

fn main() {
	cprogram :=
		cincludes[os.uname().sysname] or { panic('platform is not yet supported') }.strip_margin().trim_space()
	cc_cmd := "echo '${cprogram}' | ${cc} -x c - -E -dM ${cflags} | sort -k 2 -V"
	cc_out := os.execute_or_panic(cc_cmd)
	mut buf := strings.new_builder(1024)
	buf.writeln(vprogram.replace('%includes', cprogram))
	buf.writeln('const cdefs = {')
	for line in cc_out.output.split_into_lines() {
		for vtype, cdef_prefixes in typemap {
			for cdef_prefix in cdef_prefixes {
				if line.starts_with('#define ${cdef_prefix}') {
					cconst_name := line.fields()[1]
					if cconst_name.contains('(') {
						continue // skip non-constant macros
					}
					buf.writeln("'${cconst_name.to_lower_ascii()}': CDef{'${vtype}', C.${cconst_name}}")
				}
			}
		}
	}
	buf.write_byte(`}`)
	vfile_path := os.join_path_single(os.temp_dir(), rand.string(10) + '.c.v')
	os.write_file(vfile_path, buf.str())!
	os.execute_or_panic('v -Wfatal-errors -W -N ${vfile_path}')
	os.execute_or_panic('v fmt -w ${vfile_path}')
	v_out := os.execute_or_panic('${vfile_path.replace('.c.v', '')}')
	print(v_out.output)
	flush_stdout()
	os.rm(vfile_path)!
}