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

typedef enum {
  TOKEN_IDENTIFIER,
  TOKEN_KEYWORD_TYPE,
  TOKEN_KEYWORD_FN,
  TOKEN_KEYWORD_LET,
  TOKEN_KEYWORD_CONST,
  TOKEN_KEYWORD_IF,
  TOKEN_KEYWORD_ELSE,
  TOKEN_KEYWORD_WHILE,
  TOKEN_KEYWORD_FOR,
  TOKEN_KEYWORD_RETURN,
  TOKEN_KEYWORD_USE,
  TOKEN_OPERATOR_IS
} TokenType;

typedef struct {
  const char *keyword;
  TokenType token;
} Keyword;

Keyword keywords[] = {
  {"type",   TOKEN_KEYWORD_TYPE},
  {"fn",     TOKEN_KEYWORD_FN},
  {"let",    TOKEN_KEYWORD_LET},
  {"const",  TOKEN_KEYWORD_CONST},
  {"if",     TOKEN_KEYWORD_IF},
  {"else",   TOKEN_KEYWORD_ELSE},
  {"while",  TOKEN_KEYWORD_WHILE},
  {"for",    TOKEN_KEYWORD_FOR},
  {"return", TOKEN_KEYWORD_RETURN},
  {"use",    TOKEN_KEYWORD_USE},
  {"is",     TOKEN_OPERATOR_IS},
};

void emit_keyword_header(FILE *out) {
  fprintf(out, "#ifndef KEYWORDS_H\n");
  fprintf(out, "#define KEYWORDS_H\n\n");
  fprintf(out, "#include \"lexer.h\"\n\n");

  fprintf(out, "static TokenType check_keyword(int start, int length, const char *rest, TokenType type) {\n");
  fprintf(out, "  if ((lexer.current - lexer.start) == start + length &&\n");
  fprintf(out, "      memcmp(lexer.start + start, rest, length) == 0) return type;\n");
  fprintf(out, "  return TOKEN_IDENTIFIER;\n");
  fprintf(out, "}\n\n");

  fprintf(out, "static TokenType identifier_type(void) {\n");
  fprintf(out, "  switch (lexer.start[0]) {\n");

  for (char ch = 'a'; ch <= 'z'; ++ch) {
    int printed = 0;
    for (int i = 0; i < sizeof(keywords) / sizeof(Keyword); ++i) {
      const char *kw = keywords[i].keyword;
      if (kw[0] == ch) {
        if (!printed) {
          fprintf(out, "    case '%c':\n", ch);
          printed = 1;
        }

        int len = (int)strlen(kw);
        fprintf(out, "      return check_keyword(%d, %d, \"%s\", %s);\n",
                1, len - 1, kw + 1,
                (keywords[i].token == TOKEN_IDENTIFIER ? "TOKEN_IDENTIFIER" :
                 keywords[i].token == TOKEN_OPERATOR_IS ? "TOKEN_OPERATOR_IS" :
                 keywords[i].token == TOKEN_KEYWORD_RETURN ? "TOKEN_KEYWORD_RETURN" :
                 keywords[i].token == TOKEN_KEYWORD_WHILE ? "TOKEN_KEYWORD_WHILE" :
                 keywords[i].token == TOKEN_KEYWORD_CONST ? "TOKEN_KEYWORD_CONST" :
                 keywords[i].token == TOKEN_KEYWORD_TYPE ? "TOKEN_KEYWORD_TYPE" :
                 keywords[i].token == TOKEN_KEYWORD_FN ? "TOKEN_KEYWORD_FN" :
                 keywords[i].token == TOKEN_KEYWORD_IF ? "TOKEN_KEYWORD_IF" :
                 keywords[i].token == TOKEN_KEYWORD_FOR ? "TOKEN_KEYWORD_FOR" :
                 keywords[i].token == TOKEN_KEYWORD_LET ? "TOKEN_KEYWORD_LET" :
                 keywords[i].token == TOKEN_KEYWORD_ELSE ? "TOKEN_KEYWORD_ELSE" :
                 keywords[i].token == TOKEN_KEYWORD_USE ? "TOKEN_KEYWORD_USE" : "TOKEN_IDENTIFIER"));
      }
    }
  }

  fprintf(out, "  }\n  return TOKEN_IDENTIFIER;\n");
  fprintf(out, "}\n\n");

  fprintf(out, "#endif // KEYWORDS_H\n");
}

int main(void) {
  emit_keyword_header(stdout);
  return 0;
}