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

const int NUM_KEYWORDS = 32;
static char *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"};

static char *SEPERATORS = "()[]{};,:";

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 seperator {
  SEP_LPAREN,
  SEP_RPAREN,
  SEP_LSQUARE,
  SEP_RSQUARE,
  SEP_LCURLY,
  SEP_RCURLY,
  SEP_SEMICOLON,
  SEP_COMMA,
  SEP_DOT,
  SEP_COLOR,
};

enum token_kind {
  TOK_IDENTIFIER,
  TOK_KEYWORD,
  TOK_CONSTANT,
  TOK_SEPERATOR,
  TOK_OPERATOR,
  TOK_END,
};

union token_data {
  char *identifier;
  enum keyword keyword;
  int constant_value;
  enum seperator seperator;
  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 = NULL;
  while (*p) {
    int remaining = end - p;
    // printf("tok %c\n", p[0]);

    //* whitespace
    if (p[0] == ' ' || p[0] == '\t' || p[0] == '\n') {
      p++;
      continue;
    }

    //* seperators
    for (int i = 0; SEPERATORS[i]; i++) {
      if (p[0] == SEPERATORS[i]) {
        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 = TOK_SEPERATOR;
        new_token->data.seperator = i;
      }
    }

    //* operators

    //* 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;
      } else if (p[0] == '#') {
        p += 1;
        char c;
        while ((c = *p++) && c != '\n')
          ;
        continue;
      }
    }

    //* keyword
    char match = 0;
    for (int i = 0; i < NUM_KEYWORDS; i++) {
      char *kw = KEYWORDS[i];
      if (remaining >= strlen(kw)) {
        if (strncmp(kw, p, strlen(kw)) == 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 = TOK_KEYWORD;
          new_token->data.keyword = i;

          // printf("kw match %i %li\n", i, strlen(kw));
          p += strlen(kw);
          match = 1;
          break;
        }
      }
    }
    if (match) {
      continue;
    }

    fprintf(stderr, "unknown token at %li\n", p - source);
    printf("%s", p);
    return NULL;
  }

  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 = TOK_END;

  return tokens;
}

void debug_tokens(struct token *tokens) {
  for (int i = 0; tokens[i].kind != TOK_END; i++) {
    switch (tokens[i].kind) {
    case TOK_IDENTIFIER:
      printf("TOK_IDENTIFIER, ");
      break;
    case TOK_KEYWORD:
      printf("TOK_KEYWORD, ");
      break;
    case TOK_CONSTANT:
      printf("TOK_CONSTANT, ");
      break;
    case TOK_OPERATOR:
      printf("TOK_OPERATOR, ");
      break;
    case TOK_SEPERATOR:
      printf("TOK_SEPERATOR, ");
      break;
    case TOK_END:
      break;
    }
  }
  printf("TOK_END\n");
}

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';

  struct token *tokens = tokenize(source);
  if (!tokens)
    return 1;
  debug_tokens(tokens);
  free(tokens);

  return 0;
}