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

#define NUM_KEYWORDS 32
static char *KEYWORDS[NUM_KEYWORDS] = {
    "auto",     "break",  "case",    "char",   "const",    "continue",
    "default",  "do",     "double",  "else",   "enum",     "extern",
    "float",    "for",    "goto",    "if",     "int",      "long",
    "register", "return", "short",   "signed", "sizeof",   "static",
    "struct",   "switch", "typedef", "union",  "unsigned", "void",
    "volatile", "while"};

enum keyword {
  kW_AUTO,
  KW_BREAK,
  KW_CASE,
  KW_CHAR,
  KW_CONST,
  KW_CONTINUE,
  KW_DEFAULT,
  KW_DO,
  KW_DOUBLE,
  KW_ELSE,
  KW_ENUM,
  KW_EXTERN,
  KW_FLOAT,
  KW_FOR,
  KW_GOTO,
  KW_IF,
  KW_INT,
  KW_LONG,
  KW_REGISTER,
  KW_RETURN,
  KW_SHORT,
  KW_SIGNED,
  KW_SIZEOF,
  KW_STATIC,
  KW_STRUCT,
  KW_SWITCH,
  KW_TYPEDEF,
  KW_UNION,
  KW_UNSIGNED,
  KW_VOID,
  KW_VOLATILE,
  KW_WHILE,
};
enum operator{
  OP_ADD,
  OP_SUB,
  OP_MUL,
  OP_DIV,
  OP_MOD,
};
enum token_kind {
  IDENTIFIER,
  KEYWORD,
  CONSTANT,
  OPERATOR,
  END,
};
union token_data {
  char *identifier;
  enum keyword keyword;
  int constant_value;
  enum operator operator;
};
struct token {
  enum token_kind kind;
  union token_data data;
};

struct token *tokenize(char *source) {
  char *end = source + strlen(source);
  char *p = source;
  int num_tokens = 0;
  struct token *tokens;
  while (*p) {
    int remaining = end - p;

    //* comments
    if (remaining >= 2) {
      if (p[0] == '/' && p[1] == '/') {
        p += 2;
        while (*p) {
          if (*p++ == '\n') {
            break;
          }
        }
        continue;
      } else if (p[0] == '/' && p[1] == '*') {
        p += 2;
        char last = '\0';
        while (*p) {
          if (*p == '/' && last == '*') {
            p++;
            break;
          }
          last = *p;
          p++;
        }
        continue;
      }
    }

    //* keyword
    for (int i = 0; i < NUM_KEYWORDS; i++) {
      char *kw = KEYWORDS[i];
      if (remaining >= strlen(kw)) {
        if (strcmp(kw, p) == 0) {
          num_tokens += 1;

          tokens = realloc(tokens, sizeof(struct token) * num_tokens);
          if (!tokens) {
            fprintf(stderr, "realloc failed");
            return NULL;
          }
          struct token *new_token = &tokens[num_tokens - 1];
          new_token->kind = KEYWORD;
          new_token->data.keyword = i;

          p += strlen(kw);
          continue;
        }
      }
    }

    fprintf(stderr, "unknown token\n");
    return NULL;
  }
  return tokens;
}

int main() {}