/*
 * genlib.c: generate unified LispLibrary.h for the various uLisp
 * platforms I work on.
 */

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/stat.h>


#define MAX_FILENAME 256
#define MAX_STRFTIME 32
#define BUFFER_SIZE 4096


const char	lisp_output[] = "LispLibrary.h";


/*
 * Determines whether a directory exists.
 */
int
path_exists(const char *path)
{
	struct stat	   st;
	int		   rv;

	rv = stat(path, &st);
	if (rv == -1) {
		return 0;
	}

	if (st.st_mode & S_IFDIR) {
		return 1;
	}
	else if (st.st_mode & S_IFREG) {
		return 1;
	}

	return 1;
}


/*
 * Unlike some other functions, it is an error to call copy_library if the path
 * doesn't exist. Other functions (such as copy_platform_library) will validate
 * the file exists first and skip it if it doesn't.
 */
static int
copy_library(const char *filename, int source_fd)
{

	char	buffer[BUFFER_SIZE];
	ssize_t	bytes_read = 0;
	ssize_t	bytes_written = 0;
	int	fd = -1;

	fd = open(filename, O_RDONLY);
	if (fd == -1) {
		return -1;
	}

	while ((bytes_read = read(fd, buffer, sizeof(buffer))) > 0) {
		bytes_written = write(source_fd, buffer, bytes_read);
		if (bytes_written != bytes_read) {
			close(fd);
			return -1;
		}
	}

	if (bytes_read == -1) {
		close(fd);
		return -1;
	}

	close(fd);
	return 0;
}


static int
copy_platform_library(const char *platform, int dest_fd) {
	char	filename[MAX_FILENAME];

	if (!platform || !*platform) {
		errno = EINVAL;
		return -1;
	}

	printf("[+] attempting to load %s-specific library...\n",
	    platform);

	if (snprintf(filename, sizeof(filename), "%s.lsp", platform) >=
	    (int)sizeof(filename)) {
		errno = ENAMETOOLONG;
		return -1;
	}

	if (!path_exists(filename)) {
		printf("\t[+] %s-specific library not found; skipping.\n",
		    platform);
		return 0;
	}

	dprintf(dest_fd, "(when (eq (platform) :%s)", platform);

	if (copy_library(filename, dest_fd) != 0) {
		perror("[!] copying failed");
		return -1;
	}

	dprintf(dest_fd, ")\n");

	return 0;
}


static void
write_preamble(int dest_fd)
{
	char		timestamp[MAX_STRFTIME+1];
	struct tm	tm;
	time_t		now = time(NULL);

	localtime_r(&now, &tm);

	dprintf(dest_fd,
	    "/*\n"
	    " * LispLibrary.h - builtin library of additional uLisp functions\n"
	    " *\n"
	    " * NOTE:\n"
	    " * this file was automatically generated on %s\n"
	    " *\n"
	    " * Changes will not be persisted across builds or platforms.\n"
	    " */\n\n"
	    "const char LispLibrary[] PROGMEM = R\"lisplibrary(\n\n",
	    timestamp);
}


static void
write_epilogue(int dest_fd)
{
	dprintf(dest_fd, "\n)lisplibrary\";\n");
}


static void
usage(int status)
{
	FILE	*output = stdout;

	if (status != 0) {
		output = stderr;
	}

	fprintf(output, "Usage: genlib [-h]\n"
	    ""
	    "Generates a unified LispLibrary.h for the various platforms.\n");
	exit(status);
}


int
main(int argc, const char *argv[])
{
	int	fd = -1;
	int	ch;

	while ((ch = getopt(argc, (char **)argv, "h")) != -1) {
		switch (ch) {
		case 'h':
			usage(0);
			break;
		default:
			usage(1);
		}
	}

	argc -= optind;
	argv += optind;

	fd = open(lisp_output, O_WRONLY|O_CREAT, 0644);
	if (fd == -1) {
		perror("[!] failed to open library for write");
		exit(1);
	}

	write_preamble(fd);
	if (copy_library("library.lsp", fd) != 0) {
		fprintf(stderr, "[!] failed to generate %s.\n", lisp_output);
		exit(1);
	}

	if (copy_platform_library("picocalc", fd) != 0) {
		fprintf(stderr, "[!] failed to generate the picocalc component.\n");
		exit(1);
	}

	if (copy_platform_library("t-deck", fd) != 0) {
		fprintf(stderr, "[!] failed to generate the picocalc component.\n");
		exit(1);
	}

	if (copy_platform_library("teensy", fd) != 0) {
		fprintf(stderr, "[!] failed to generate the picocalc component.\n");
		exit(1);
	}

	write_epilogue(fd);

	close(fd);
}