#include <fcntl.h>
#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/wait.h>

struct file {
	struct file *next;
	char *name;
	char *newname;
};

int main(int argc, char *argv[]) {
	char *dirname = ".";
	if (argc > 1) {
		if (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--help") == 0) {
			printf("Usage: %s [-h] [directory]\n", argv[0]);
			exit(0);
		}
		dirname = argv[1];
	}
	DIR *dir = opendir(dirname);
	if (!dir) {
		perror("opendir");
		exit(1);
	}
	int fd = dirfd(dir);
	fchdir(fd);
	struct file *begin = NULL;
	struct file **cur = &begin;
	while (1) {
		errno = 0;
		struct dirent *entry = readdir(dir);
		if (!entry) {
			if (errno != 0) {
				perror("readdir");
				exit(1);
			}
			break;
		}

		if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
			continue;

		*cur = malloc(sizeof(struct file));
		if (!*cur) {
			perror("malloc");
			exit(1);
		}
		(*cur)->name = strdup(entry->d_name);
		(*cur)->newname = NULL;
		cur = &(*cur)->next;
	}

	if (!begin) {
		exit(0);
	}

	char template[] = "/tmp/vidir-c.XXXXXX";
	if (!mkstemp(template)) {
		perror("mkstemp");
		exit(1);
	}

	FILE *tempfile = fopen(template, "w+");
	if (!tempfile) {
		perror("fopen");
		exit(1);
	}

	int i = 1;
	for (struct file *file = begin; file; file = file->next) {
		fprintf(tempfile, "%d %s\n", i, file->name);
		i ++;
	}
	fflush(tempfile);

	pid_t pid = fork();
	if (pid == -1) {
		perror("fork");
		exit(1);
	}
	if (pid == 0) {
		char *editor = getenv("EDITOR");
		if (!editor)
			editor = "nano";

		execlp(editor, editor, template, (char *) NULL);

		perror("execlp");
		exit(1);
	}

	wait(NULL);

	fseek(tempfile, 0, SEEK_SET);

	ssize_t nread;
	char *line = NULL;
	size_t n;
	while ((nread = getline(&line, &n, tempfile)) != -1) {
		line[nread - 1] = '\0';

		char *endptr = NULL;
		long num = strtol(line, &endptr, 10);

		if (line == endptr)
			continue;

		if (*endptr != ' ')
			continue;

		char *filename = endptr + 1;

		struct file *file = begin;
		int i = 1;
		while (file && i ++ < num)
			file = file->next;

		if (!file)
			continue;

		file->newname = strdup(filename);
	}

	for (struct file *file = begin; file; file = file->next) {
		if (!file->newname) {
			printf("Delete: %s\n", file->name);
			remove(file->name);
			continue;
		}
		if (strcmp(file->name, file->newname) != 0) {
			printf("Rename: %s to %s\n", file->name, file->newname);
			rename(file->name, file->newname);
			continue;
		}
	}

	unlink(template);
	exit(0);
}