kv_parser

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

struct Config {
  bool  show_welcome;
  bool  kill_yourself;
  char* last_message;
};

char *get_key(const char **buf) {
  char *key = (char*)malloc(sizeof(char) * 12 + 1);
  if (key == NULL) {
    printf("Failed to allocate buffer for key\n");
    return NULL;
  }

  unsigned int key_size = 0;
  unsigned int key_cap = 12;

  while (**buf != '\0' && **buf != '\n' && **buf != '=') {
    if (**buf == ' ' || **buf == '\t') {
      *buf = *buf + 1;
      continue;
    }

    if (key_size >= key_cap) {
      key_cap *= 2;
      key = realloc(key, sizeof(char) * key_cap + 1);
      if (key == NULL) {
        printf("Failed to reallocate buffer for key\n");
        return NULL;
      }
    }

    key[key_size] = **buf;
    key_size++;
    *buf = *buf + 1;
  }
  key[key_size] = '\0';
  return key;
}

char *get_val(const char **buf) {
  char *key = (char*)malloc(sizeof(char) * 12 + 1);
  if (key == NULL) {
    printf("Failed to allocate buffer for key\n");
    return NULL;
  }

  // eat whitespaces till we reach a valid character
  while (**buf != '\0' && (**buf == ' '  || **buf == '\t')) {
    *buf = *buf + 1;
  }

  bool is_string = **buf == '"' ? true : false;
  if (is_string) *buf = *buf + 1;

  unsigned int key_size = 0;
  unsigned int key_cap = 12;

  while (**buf != '\0') {
    if (is_string && **buf == '"') {
      *buf = *buf + 1;
      break;
    } else if (**buf == '\n' || **buf == '=') {
      break;
    } else if (!is_string && (**buf == ' ' || **buf == '\t')) {
      *buf = *buf + 1;
      continue;
    }

    if (key_size >= key_cap) {
      key_cap *= 2;
      key = realloc(key, sizeof(char) * key_cap + 1);
      if (key == NULL) {
        printf("Failed to reallocate buffer for key\n");
        return NULL;
      }
    }

    key[key_size] = **buf;
    key_size++;
    *buf = *buf + 1;
  }
  key[key_size] = '\0';
  return key;
}

int parse_input(const char *buf, struct Config* cfg) {
  while (*buf != '\0') {
    char *key = get_key(&buf);
    if (key == NULL) return 1;
    buf++;

    char *val = get_val(&buf);
    if (val == NULL) return 1;
    buf++;

    if (strcmp(key, "show_welcome") == 0) {
      if (strcmp(val, "true") == 0) {
        cfg->show_welcome = true;
      } else if (strcmp(val, "false") != 0) {
        printf("WARNING: wrong type of value for `show_welcome`, defaulting to `false`\n");
      }

      free(key);
      free(val);
    } else if (strcmp(key, "kill_yourself") == 0) {
      if (strcmp(val, "true") == 0) {
        cfg->kill_yourself = true;
      } else if (strcmp(val, "false") != 0) {
        printf("WARNING: wrong type of value for `kill_yourself`, defaulting to `false`\n");
      }

      free(key);
      free(val);
    } else if (strcmp(key, "last_message") == 0) {
      free(cfg->last_message);
      cfg->last_message = val;

      free(key);
    } else {
      printf("WARNING: unknown key '%s'\n", key);
      free(key);
      free(val);
    }
  }
  return 0;
}

int main(int argc, const char** argv) {
  if (argc < 2) {
    printf("Usage: %s [FILE]\n", argv[0]);
    return 0;
  };

  FILE *fp = fopen(argv[1], "r");
  if (fp == NULL) {
    printf("Failed to open file: %s\n", argv[1]);
    return 1;
  }

  fseek(fp, 0L, SEEK_END);
  unsigned int sz = ftell(fp);
  rewind(fp);

  char *buf = (char*)malloc(sizeof(char) * sz + 1);
  if (!buf) {
    printf("Failed to create buffer\n");
    return 1;
  }

  fread(buf, sz, sizeof(char), fp);
  buf[sz] = '\0';

  fflush(fp);
  fclose(fp);

  struct Config *cfg = (struct Config*)malloc(sizeof(struct Config));
  cfg->show_welcome = false;
  cfg->kill_yourself = false;
  cfg->last_message = (char*)malloc(sizeof(char));
  cfg->last_message[0] = '\0';

  int ret = parse_input(buf, cfg);

  printf("Config {\n"
         "\tshow_welcome: %s,\n"
         "\tkill_yourself: %s,\n"
         "\tlast_message: \"%s\"\n"
         "}\n",
         cfg->show_welcome ? "true" : "false",
         cfg->kill_yourself ? "true" : "false",
         cfg->last_message
  );

  free(buf);
  free(cfg->last_message);
  free(cfg);

  return ret;
}