// vidir.c - rewrite of Joey Hess's vidir in C
// usage: ./vidir [--verbose] [dir|file|-]

#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <libgen.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#define MAX_FILES 10000

typedef struct {
  int id;
  char *path;
} Item;

static int verbose = 0;
static Item items[MAX_FILES];
static int n_items = 0;
static int error_flag = 0;

void die(const char *msg) {
  perror(msg);
  exit(1);
}

void add_item(const char *path) {
  if (n_items >= MAX_FILES) {
    fprintf(stderr, "too many files\n");
    exit(1);
  }
  items[n_items].id = n_items + 1;
  items[n_items].path = strdup(path);
  n_items++;
}

void read_dir(const char *dirname) {
  DIR *dir = opendir(dirname);
  if (!dir) {
    fprintf(stderr, "cannot read %s: %s\n", dirname, strerror(errno));
    exit(1);
  }
  struct dirent *ent;
  while ((ent = readdir(dir))) {
    if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
      continue;
    char path[PATH_MAX];
    snprintf(path, sizeof(path), "%s/%s", dirname, ent->d_name);
    add_item(path);
  }
  closedir(dir);
}

int rm_path(const char *p) {
  struct stat st;
  if (lstat(p, &st) != 0)
    return -1;
  if (S_ISDIR(st.st_mode))
    return rmdir(p);
  else
    return unlink(p);
}

int main(int argc, char *argv[]) {
  char tmpname[] = "/tmp/vidirXXXXXX";
  int fd;
  FILE *tmp;
  char line[PATH_MAX + 64];
  char *editor;
  char buf[PATH_MAX + 64];

  // parse args
  for (int i = 1; i < argc; i++) {
    if (!strcmp(argv[i], "--verbose") || !strcmp(argv[i], "-v")) {
      verbose = 1;
    } else if (!strcmp(argv[i], "-")) {
      // read stdin list
      while (fgets(line, sizeof(line), stdin)) {
        line[strcspn(line, "\r\n")] = 0;
        if (*line)
          add_item(line);
      }
    } else {
      struct stat st;
      if (stat(argv[i], &st) == 0 && S_ISDIR(st.st_mode))
        read_dir(argv[i]);
      else
        add_item(argv[i]);
    }
  }
  if (n_items == 0)
    read_dir(".");

  // write numbered list
  fd = mkstemp(tmpname);
  if (fd < 0)
    die("mkstemp");
  tmp = fdopen(fd, "w");
  if (!tmp)
    die("fdopen");
  int digits = snprintf(NULL, 0, "%d", n_items);
  for (int i = 0; i < n_items; i++)
    fprintf(tmp, "%0*d\t%s\n", digits, items[i].id, items[i].path);
  fclose(tmp);

  // pick editor
  editor = getenv("VISUAL");
  if (!editor)
    editor = getenv("EDITOR");
  if (!editor)
    editor = "vi";

  snprintf(buf, sizeof(buf), "%s %s", editor, tmpname);
  int ret = system(buf);
  if (ret != 0) {
    fprintf(stderr, "editor exited nonzero, aborting\n");
    unlink(tmpname);
    exit(1);
  }

  // re-read edited list
  tmp = fopen(tmpname, "r");
  if (!tmp)
    die("fopen tmp");

  char newname[PATH_MAX];
  while (fgets(line, sizeof(line), tmp)) {
    line[strcspn(line, "\r\n")] = 0;
    if (strlen(line) == 0)
      continue;
    int num;
    if (sscanf(line, "%d%[^\n]", &num, newname) < 1)
      continue;
    char *p = newname;
    while (isspace((unsigned char)*p))
      p++;
    if (num <= 0 || num > n_items)
      continue;
    char *old = items[num - 1].path;
    if (*p == '\0') {
      // deleted line -> remove file
      if (rm_path(old) != 0) {
        fprintf(stderr, "failed to remove %s: %s\n", old, strerror(errno));
        error_flag = 1;
      } else if (verbose) {
        printf("removed '%s'\n", old);
      }
    } else if (strcmp(p, old) != 0) {
      // rename
      char dirbuf[PATH_MAX];
      strlcpy(dirbuf, p, sizeof(dirbuf));
      char *d = dirname(dirbuf);
      mkdir(d, 0777);
      if (access(p, F_OK) == 0) {
        char tmpname[PATH_MAX + 16]; // allow space for suffixes
        int suffix = 0;
        snprintf(tmpname, sizeof(tmpname), "%s~", p);
        while (access(tmpname, F_OK) == 0) {
          suffix++;
          snprintf(tmpname, sizeof(tmpname), "%s~%d", p, suffix);
        }
        if (rename(p, tmpname) != 0) {
          fprintf(stderr, "failed to rename '%s' -> '%s': %s\n", p, tmpname,
                  strerror(errno));
          error_flag = 1;
        } else if (verbose) {
          printf("renamed '%s' -> '%s'\n", p, tmpname);
        }
        // update internal mapping so future renames see the new tmp location
        for (int j = 0; j < n_items; j++) {
          if (strcmp(items[j].path, p) == 0) {
            free(items[j].path);
            items[j].path = strdup(tmpname);
          }
        }
      }

      // now perform the intended rename
      if (rename(old, p) != 0) {
        fprintf(stderr, "failed to rename %s -> %s: %s\n", old, p,
                strerror(errno));
        error_flag = 1;
      } else if (verbose) {
        printf("renamed '%s' -> '%s'\n", old, p);
      }
      free(items[num - 1].path);
      items[num - 1].path = strdup(p);
    }
  }
  fclose(tmp);
  unlink(tmpname);
  return error_flag;
}