#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.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;
        char c;
        while ((c = *p++) && c != '\n')
          ;
        continue;
      } else if (p[0] == '/' && p[1] == '*') {
        p += 2;
        char c, d;
        while ((d = c, c = *p++) && c == '/' && d == '*')
          ;
        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\n");
            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(int argc, char **argv) {
  if (argc < 3) {
    fprintf(stderr, "USAGE:\n\tattocc <input> <output>\n");
    return 1;
  }
  char *input = argv[1];
  char *output = argv[2];

  int input_fd = open(input, O_RDONLY | O_CLOEXEC);
  if (input_fd < 0) {
    perror("cannot open input");
    return 1;
  }

  int output_fd = open(output, O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, 0640);
  if (output_fd < 0) {
    perror("cannot open input");
    return 1;
  }

  int source_len = 0;
  char *source = NULL;
  int size;
  char buffer[4096];

  while ((size = read(input_fd, &buffer, 4096))) {
    if (size < 0) {
      perror("cannot read source");
      return 1;
    }

    source_len += size;
    source = realloc(source, source_len + 1);
    if (!source) {
      fprintf(stderr, "malloc failed\n");
      return 1;
    }

    for (int i = 0; i < size; i++) {
      source[source_len - size + i] = buffer[i];
    }
  }
  source[source_len] = '\0';

  printf("%s", source);

  return 0;
}