#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>

#define _GNU_SOURCE

#include <err.h>
#include <errno.h>
#include <dirent.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <spawn.h>

#ifdef DEBUG
#define debug_printf(args...) fprintf(stderr, ## args)
#else
#define debug_printf(args...)
#endif

#if defined(__APPLE__)
#define st_mtim	st_mtimespec
#endif

static int spawn_shell_pipe(char *const argv[], pid_t *pid, int outfd)
{
	int pipefd[2];
	posix_spawn_file_actions_t factions;

	if (pipe(pipefd) < 0) {
		warn("pipe");
		return -1;
	}

	if (posix_spawn_file_actions_init(&factions) < 0) {
		warn("posix_spawn_file_actions_init");
		goto err1;
	}

	if (outfd >=0 && posix_spawn_file_actions_adddup2(&factions, outfd, STDOUT_FILENO) < 0) {
		warn("posix_spawn_file_actions_adddup2");
		goto err2;
	}

	if (posix_spawn_file_actions_adddup2(&factions, pipefd[0], 0) < 0) {
		warn("posix_spawn_file_actions_adddup2");
		goto err2;
	}

	if (posix_spawn(pid, argv[0], &factions, NULL, argv, NULL) < 0) {
		warn("%s", argv[0]);
		goto err2;
	}

	close(pipefd[0]);
	return pipefd[1];

err2:
	posix_spawn_file_actions_destroy(&factions);
err1:
	close(pipefd[0]);
	close(pipefd[1]);
	return -1;
}

static int read_apkbuild(int shellfd, size_t size, const char *name)
{
#define ECHO_SEPARATOR	"echo \"-\"\n"
#define ECHO_STR(var)	"[ -n \"$" #var "\" ] && echo \" " #var ": $" #var "\"\n"
#define ECHO_LIST(var)	"[ -n \"$" #var "\" ] && echo ' " #var ":' && " \
			"for i in $" #var "; do\n" \
			"\techo \"  - \\\"$i\\\"\"\n" \
			"done\n"

	char *fmtbuf =
		"unset pkgname"
			" pkgver"
			" pkgrel"
			" arch"
			" options"
			" depends"
			" makedepends"
			" checkdepends"
			" subpackages"
			" source"
			" license"
			" url"
			"\n"
		"cd %s\n"
		"aports_cache_pwd=\"$PWD\"\n"

		". ./APKBUILD >/dev/null\n"

		"if [ \"$PWD\" != \"$aports_cache_pwd\" ]; then\n"
		"	echo \"%s: PWD changed\" >&2\n"
		"	exit 1\n"
		"fi\n"

		ECHO_SEPARATOR
		ECHO_STR(pkgname)
		ECHO_STR(pkgver)
		ECHO_LIST(arch)
		ECHO_LIST(options)
		ECHO_LIST(depends)
		ECHO_LIST(makedepends)
		ECHO_LIST(checkdepends)
		ECHO_LIST(subpackages)
		ECHO_LIST(linuguas)
		ECHO_LIST(source)
		ECHO_STR(url)
		ECHO_STR(license)
		"cd ..\n\n";
	char buf[strlen(fmtbuf) + 512];
	size_t bufsize = snprintf(buf, sizeof(buf), fmtbuf, name, name);
	ssize_t r, offs=0;

	while (1) {
		r = write(shellfd, &buf[offs], bufsize - offs);
		if (r < 0) {
			warn("write to shell pipe");
			return -1;
		}

		offs += r;
		if (r == 0 || offs == bufsize)
			break;
	}

	return 0;
}

static int is_newer(struct timespec a, struct timespec b)
{
	return (a.tv_sec == b.tv_sec) ?  a.tv_nsec > b.tv_nsec : a.tv_sec > b.tv_sec;
}

static int cache_refresh_or_check(int dirfd, const char *cachefile, int shellfd)
{
	struct stat cache;
	DIR *dir;
	struct dirent *ent;
	int r = 0;
	int dirfd2 = dup(dirfd);

	if (shellfd == -1 && fstatat(dirfd, cachefile, &cache, 0) == -1)
		return 1;

	dir = fdopendir(dirfd2);
	if (dir == NULL)
		return -1;
	
	while(1) {
		char buf[PATH_MAX];
		struct stat apkbuild;

		errno = 0;
		ent = readdir(dir);
		if (ent == NULL) {
			if (errno != 0) {
				warn("readdir");
				closedir(dir);
				return -1;
			}
			break;
		}

		if (ent->d_name[0] == '.')
			continue;

		snprintf(buf, sizeof(buf), "%s/APKBUILD", ent->d_name);

		if (fstatat(dirfd, buf, &apkbuild, 0) == -1) {
			warn("%s", buf);
			continue;
		}

		if (shellfd != -1) {
			read_apkbuild(shellfd, apkbuild.st_size, ent->d_name);
			continue;
		}

		if (is_newer(apkbuild.st_mtim, cache.st_mtim)) {
			debug_printf("modified: %s\n", buf);
			r = 1;
			break;
		}
	}

	closedir(dir);
	return r;
}

int aports_cache_check(int dirfd, const char *cachefile)
{
	return cache_refresh_or_check(dirfd, cachefile, -1);
}

int aports_cache_refresh(int dirfd, const char *cachefile, char *const shell_argv[])
{
	pid_t shell_pid;
	int shellfd, outfd = -1;
	int status;

	if (cachefile) {
		outfd = open(cachefile, O_WRONLY | O_CREAT, 0660);
		if (outfd < 0) {
			warn("%s", cachefile);
			return -1;
		}
	}

	shellfd = spawn_shell_pipe(shell_argv, &shell_pid, outfd);
	debug_printf("shell pid: %d\n", shell_pid);

	if (outfd >= 0)
		close(outfd);

	cache_refresh_or_check(dirfd, cachefile, shellfd);
	write(shellfd, "exit 0\n", 7);

	if (waitpid(shell_pid, &status, 0) < 0) {
		warn("waitpid");
		return -1;
	}

	return WIFEXITED(status) ? WEXITSTATUS(status) : -1;
}