#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "util/map.h"
#include "util/versie.h"

static void usage(FILE *f) {
  fprintf(f,
      "Gebruik: tak [-hV] <bestand...>\n"
      "\n"
      "Schakel bestanden aaneen naar standaard uitvoer omgekeerd.\n"
      "\n"
      "  -h    Toon deze hulptekst\n"
      "  -V    Toon versienummer\n");
}

// Returns pointer to argument array containing the file names
static char** parse_options(int argc, char **argv) {
  int opt;
  while ((opt = getopt(argc, argv, "hV")) != -1) {
    switch (opt) {
      case 'h':
        usage(stdout);
        exit(0);

      case 'V':
        drukkedoos_print_versie(stdout, "tak");
        exit(0);

      case '?':
        usage(stderr);
        exit(1);
    }
  }

  return argv + optind;
}

struct state {
  char *buf;
  size_t sz;
};

static void process(struct state state) {
  char *lstart, *lend;
  lend = &state.buf[state.sz - 1];

  while (lend > state.buf) {
    if (*lend == '\n') {
      lend--;
    }

    lstart = lend;
    while (*lstart != '\n' && lstart != state.buf) {
      lstart--;
    }
    if (lstart != state.buf) {
      lstart++;
    }

    fwrite(lstart, 1, lend - lstart + 2, stdout);

    lend = lstart-1;
  }
}

#define CHECK_OOM(ptr) \
  if (ptr == NULL) { \
    fprintf(stderr, "tak: geheugen is op"); \
    /* I think I should free the original memory here, but whatever */ \
    return NULL; \
  }

static char *read_stream(FILE *stream, size_t *sz) {
  *sz = 0;
  size_t cap = 4096;
  char *res = malloc(cap);
  CHECK_OOM(res);

  while (!feof(stream)) {
    if (cap-*sz == 0) {
      cap *= 2;
      res = realloc(res, cap);
      CHECK_OOM(res);
    }

    const size_t amount = cap-*sz;
    const size_t n = fread(res+*sz, 1, amount, stream);
    *sz += n;

    if (n != amount && !feof(stream)) {
      fprintf(stderr, "tak: fout tijdens lezen van standaard invoer.\n");
      free(res);
      return NULL;
    }
  }

  return res;
}

int handleStream(FILE *stream) {
  size_t sz = 0;
  char *data = read_stream(stream, &sz);
  if (data == NULL) {
    return 1;
  }

  struct state state = { .buf = data, .sz = sz };
  process(state);

  free(data);
  return 0;
}

int handleFile(char *fname) {
  struct map *map = open_map(fname);
  if (map == NULL) {
    return 1;
  }

  struct state state = { .buf = map->addr, .sz = map->sb.st_size };
  process(state);

  close_map(map);

  return 0;
}

int entry_tak(int argc, char **argv) {
  char **args = parse_options(argc, argv);

  if (*args == NULL) {
    handleStream(stdin);
    return 0;
  }

  while (*args != NULL) {
    if (!strcmp(*args, "-")) {
      handleStream(stdin);
      goto next;
    }

    if (!handleFile(*args)) {
      goto next;
    }

    FILE *stream = fopen(*args, "rb");
    if (handleStream(stream)) {
      return 1;
    }
    fclose(stream);

next:
    args++;
  }

  return 0;
}