/*
    attocc - A minimal C compiler.
    Copyright (C) 2024 metamuffin

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
#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 = "()[]{};,:";

const int NUM_OPERATORS = 36;
static char *OPERATORS[] = {
    "sizeof", "<<", ">>", "+=", "-=", "*=", "/=", "%=", "<<=",
    ">>=",    "&=", "|=", "^=", "++", "--", "==", "!=", "<=",
    ">=",     "||", "&&", "+",  "-",  "*",  "/",  "%",  "<",
    ">",      "~",  "&",  "|",  "^",  "!",  "=",  ".",  "?",
};

#ifdef DEBUG
static char *OPERATOR_NAMES[] = {
    "OP_SIZEOF",
    "OP_SHIFT_LEFT",
    "OP_SHIFT_RIGHT",
    "OP_ADD_ASSIGN",
    "OP_SUB_ASSIGN",
    "OP_MUL_ASSIGN",
    "OP_DIV_ASSIGN",
    "OP_MOD_ASSIGN",
    "OP_SHIFT_LEFT_ASSIGN",
    "OP_SHIFT_RIGHT_ASSIGN",
    "OP_BITWISE_AND_ASSIGN",
    "OP_BITWISE_OR_ASSIGN",
    "OP_BITWISE_XOR_ASSIGN",
    "OP_INCREMENT",
    "OP_DECREMENT",
    "OP_EQUAL",
    "OP_NOT_EQUAL",
    "OP_LESS_EQUAL",
    "OP_GREATER_EQUAL",
    "OP_LOGICAL_OR",
    "OP_LOGICAL_AND",
    "OP_ADD",
    "OP_SUB",
    "OP_MUL_OR_POINTER",
    "OP_DIV",
    "OP_MOD",
    "OP_LESS",
    "OP_GREATER",
    "OP_BITWISE_NOT",
    "OP_BITWISE_AND_OR_REF",
    "OP_BITWISE_OR",
    "OP_BITWISE_XOR",
    "OP_LOGICAL_NOT",
    "OP_ASSIGN",
    "OP_MEMBER_ACCESS",
    "OP_TERNARY",
};
static char *KEYWORD_NAMES[] = {
    "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",
};
static char *SEPERATOR_NAMES[] = {
    "SEP_LPAREN", "SEP_RPAREN",    "SEP_LSQUARE", "SEP_RSQUARE", "SEP_LCURLY",
    "SEP_RCURLY", "SEP_SEMICOLON", "SEP_COMMA",   "SEP_DOT",     "SEP_COLOR",
};
#endif

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_SIZEOF,     // len=6
  OP_SHIFT_LEFT, // len=2
  OP_SHIFT_RIGHT,
  OP_ADD_ASSIGN,
  OP_SUB_ASSIGN,
  OP_MUL_ASSIGN,
  OP_DIV_ASSIGN,
  OP_MOD_ASSIGN,
  OP_SHIFT_LEFT_ASSIGN,
  OP_SHIFT_RIGHT_ASSIGN,
  OP_BITWISE_AND_ASSIGN,
  OP_BITWISE_OR_ASSIGN,
  OP_BITWISE_XOR_ASSIGN,
  OP_INCREMENT,
  OP_DECREMENT,
  OP_EQUAL,
  OP_NOT_EQUAL,
  OP_LESS_EQUAL,
  OP_GREATER_EQUAL,
  OP_LOGICAL_OR,
  OP_LOGICAL_AND,
  OP_ADD, // len=1
  OP_SUB,
  OP_MUL_OR_POINTER,
  OP_DIV,
  OP_MOD,
  OP_LESS,
  OP_GREATER,
  OP_BITWISE_NOT,
  OP_BITWISE_AND_OR_REF,
  OP_BITWISE_OR,
  OP_BITWISE_XOR,
  OP_LOGICAL_NOT,
  OP_ASSIGN,
  OP_MEMBER_ACCESS,
  OP_TERNARY,
};

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_END,
  TOK_IDENTIFIER,
  TOK_KEYWORD,
  TOK_CONSTANT,
  TOK_SEPERATOR,
  TOK_OPERATOR,
};

enum constant_kind {
  CONST_INT,
  CONST_STR,
  CONST_CHAR,
};

union token_data {
  char *identifier;
  enum keyword keyword;
  struct {
    enum constant_kind constant_kind;
    union {
      int constant_int_value;
      char constant_char_value;
      char *constant_str_value;
    };
  };
  enum seperator seperator;
  enum operator operator;
};

struct token {
  enum token_kind kind;
  union token_data data;
};

char is_numeric(char c) { return c >= '0' && c <= '9'; }
char is_octal(char c) { return c >= '0' && c <= '7'; }
char is_hexadecial(char c) {
  return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') ||
         (c >= 'a' && c <= 'f');
}
char is_alpha(char c) {
  return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}
char is_alphanumeric(char c) { return is_alpha(c) || is_numeric(c); }
char is_ident(char c) { return is_alphanumeric(c) || c == '_'; }

char map_escape(char c) {
  switch (c) {
  case 'n':
    return '\n';
  case 't':
    return '\t';
  case 'b':
    return '\b';
  case 'r':
    return '\r';
  case '\'':
    return '\'';
  case '"':
    return '"';
  case '0':
    return '\0';
  default:
    return '\0';
  }
}

void *realloc_failsafe(void *old, unsigned long size) {
  void *p = realloc(old, size);
  if (!p) {
    fprintf(stderr, "malloc failed for size %lu\n", size);
    exit(2);
  }
  return p;
}
char *strdup_failsafe(char *s) {
  char *p = strdup(s);
  if (!p) {
    fprintf(stderr, "strdup failed\n");
    exit(2);
  }
  return p;
}

struct token *token_push(struct token **tokens, unsigned long *num_tokens) {
  *num_tokens += 1;
  *tokens = realloc_failsafe(*tokens, sizeof(struct token) * *num_tokens);
  return &(*tokens)[*num_tokens - 1];
}

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

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

    //* comments
    if (remaining >= 2) {
      if (p[0] == '/' && p[1] == '/') {
        p += 2;
        for (char c; (c = *p++) && c != '\n';)
          ;
        continue;
      } else if (p[0] == '/' && p[1] == '*') {
        p += 2;
        for (char c, d = '\0'; (d = c, c = *p++) && !(c == '/' && d == '*');)
          ;
        continue;
      } else if (p[0] == '#') {
        p += 1;
        for (char c; (c = *p++) && c != '\n';)
          ;
        continue;
      }
    }

    //* seperators
    char match = 0;
    for (int i = 0; SEPERATORS[i]; i++) {
      if (p[0] == SEPERATORS[i]) {
        p++;
        struct token *new_token = token_push(&tokens, &num_tokens);
        if (!new_token)
          return NULL;
        new_token->kind = TOK_SEPERATOR;
        new_token->data.seperator = i;
        match = 1;
        break;
      }
    }
    if (match)
      continue;

    //* operators
    match = 0;
    for (int i = 0; i < NUM_OPERATORS; i++) {
      char *op = OPERATORS[i];
      if (remaining >= strlen(op)) {
        if (strncmp(op, p, strlen(op)) == 0) {
          struct token *new_token = token_push(&tokens, &num_tokens);
          if (!new_token)
            return NULL;
          new_token->kind = TOK_OPERATOR;
          new_token->data.operator= i;

          p += strlen(op);
          match = 1;
          break;
        }
      }
    }
    if (match)
      continue;

    //* keyword
    match = 0;
    for (int i = 0; i < NUM_KEYWORDS; i++) {
      char *kw = KEYWORDS[i];
      if (remaining >= strlen(kw) + 1) {
        if (strncmp(kw, p, strlen(kw)) == 0 && !is_ident(p[strlen(kw)])) {
          struct token *new_token = token_push(&tokens, &num_tokens);
          if (!new_token)
            return NULL;
          new_token->kind = TOK_KEYWORD;
          new_token->data.keyword = i;

          p += strlen(kw);
          match = 1;
          break;
        }
      }
    }
    if (match)
      continue;

    //* number constant
    if (is_numeric(p[0])) {
      int value = 0;
      if (remaining >= 2 && p[1] == 'x') {
        p += 2;
        for (char c; (c = *p++) && is_hexadecial(c);) {
          value *= 0x10;
          value += c <= '9' ? c - '0' : 10 + (c <= 'F' ? c - 'A' : c - 'a');
        }
      } else if (p[0] == '0') {
        p += 1;
        for (char c; (c = *p++) && is_octal(c);) {
          value *= 010;
          value += c - '0';
        }
      } else {
        for (char c; (c = *p++) && is_numeric(c);) {
          value *= 10;
          value += c - '0';
        }
      }
      p--;

      struct token *new_token = token_push(&tokens, &num_tokens);
      if (!new_token)
        return NULL;
      new_token->kind = TOK_CONSTANT;
      new_token->data.constant_kind = CONST_INT;
      new_token->data.constant_int_value = value;
      continue;
    }

    //* string constant
    if (p[0] == '"') {
      p++;
      char *str = NULL;
      int str_len = 0;
      for (char c; (c = *p++) && c != '"';) {
        // TODO escape
        str_len++;
        str = realloc_failsafe(str, str_len);
        str[str_len - 1] = c;
      }
      // null termination
      str_len++;
      str = realloc_failsafe(str, str_len);
      str[str_len - 1] = '\0';

      struct token *new_token = token_push(&tokens, &num_tokens);
      new_token->kind = TOK_CONSTANT;
      new_token->data.constant_kind = CONST_STR;
      new_token->data.constant_str_value = str;
      continue;
    }

    //* char constant
    if (p[0] == '\'') {
      if (!*p++)
        return NULL;
      char chr = p[0];
      if (p[0] == '\\') {
        if (!*p++)
          return NULL;
        chr = map_escape(p[0]);
      }
      if (!*p++)
        return NULL;
      if (*p++ != '\'')
        return fprintf(stderr, "expected '\n"), NULL;

      struct token *new_token = token_push(&tokens, &num_tokens);
      new_token->kind = TOK_CONSTANT;
      new_token->data.constant_kind = CONST_CHAR;
      new_token->data.constant_char_value = chr;
      continue;
    }

    //* identifier
    if (is_ident(p[0]) && !is_numeric(p[0])) {
      char *ident_start = p;
      for (char c; (c = *p++) && is_ident(c);)
        ;
      int ident_len = p - ident_start - 1;
      char *ident_str = realloc_failsafe(NULL, ident_len + 1);
      for (int i = 0; i < ident_len; i++)
        ident_str[i] = ident_start[i];
      ident_str[ident_len] = '\0';

      struct token *new_token = token_push(&tokens, &num_tokens);
      new_token->kind = TOK_IDENTIFIER;
      new_token->data.identifier = ident_str;

      continue;
    }

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

  struct token *new_token = token_push(&tokens, &num_tokens);
  new_token->kind = TOK_END;

  return tokens;
}

void free_tokens(struct token *tokens) {
  for (int i = 0; tokens[i].kind != TOK_END; i++) {
    switch (tokens[i].kind) {
    case TOK_IDENTIFIER:
      free(tokens[i].data.identifier);
      break;
    case TOK_CONSTANT:
      switch (tokens[i].data.constant_kind) {
      case CONST_STR:
        free(tokens[i].data.constant_str_value);
        break;
      default:
        break;
      }
    default:
      break;
    }
  }
  free(tokens);
}

#ifdef DEBUG
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:%s, ", tokens[i].data.identifier);
      break;
    case TOK_KEYWORD:
      printf("TOK_KEYWORD:%s, ", KEYWORD_NAMES[tokens[i].data.keyword]);
      break;
    case TOK_CONSTANT:
      switch (tokens[i].data.constant_kind) {
      case CONST_INT:
        printf("TOK_CONSTANT:CONST_INT:%i, ",
               tokens[i].data.constant_int_value);
        break;
      case CONST_STR:
        printf("TOK_CONSTANT:CONST_STR:%s, ",
               tokens[i].data.constant_str_value);
        break;
      case CONST_CHAR:
        printf("TOK_CONSTANT:CONST_CHAR:%c, ",
               tokens[i].data.constant_char_value);
        break;
      }
      break;
    case TOK_OPERATOR:
      printf("TOK_OPERATOR:%s, ", OPERATOR_NAMES[tokens[i].data.operator] );
      break;
    case TOK_SEPERATOR:
      printf("TOK_SEPERATOR:%s, ", SEPERATOR_NAMES[tokens[i].data.seperator]);
      break;
    case TOK_END:
      break;
    }
    printf("\n");
  }
  printf("TOK_END\n");
}
#endif

struct node {
  enum node_kind {
    NO_BINOP,
    NO_UNOP,
    NO_MEMBER_ACCESS,
    NO_STRUCT,
    NO_UNION,
    NO_ENUM,
    NO_FUNCTION,
  } kind;
  union node_data {
    struct node_data_binop {
      struct node *lhs;
      struct node *rhs;
    } binop;
    struct node_data_enum {
      char *name;
      char is_decl;
      unsigned long num_members;
      struct enum_member {
        int value;
        char *name;
      } *members;
    } enum_;
  } data;
};

char parse_enum_decl(struct token *tokens, struct node **node);

char parse_type(struct token *tokens, struct node **node) {
  if (parse_enum_decl(tokens, node))
    return 1;
  if (*node)
    return 0;

  return 0;
}

char parse_enum_decl(struct token *tokens, struct node **node) {
  int p = 0;
  printf("1\n");

  if (tokens[p].kind != TOK_KEYWORD || tokens[p].data.keyword != KW_ENUM)
    return 0;
  p++;

  printf("2\n");

  char *ident = NULL;
  if (tokens[p].kind == TOK_IDENTIFIER) {
    ident = tokens[p].data.identifier;
    p++;
  }
  printf("3 %i %i\n", tokens[p].kind, tokens[p].data.seperator);

  char is_decl = 0;
  struct enum_member *members = NULL;
  unsigned long num_members = 0;

  if (tokens[p].kind == TOK_SEPERATOR &&
      tokens[p].data.seperator == SEP_LCURLY) {
    p++;
    is_decl = 1;
    printf("4\n");

    int value = 0;

    while (1) {
      if (tokens[p].kind == TOK_SEPERATOR &&
          tokens[p].data.seperator == SEP_RCURLY)
        break;

      if (tokens[p].kind == TOK_END)
        return 1;

      if (tokens[p].kind != TOK_IDENTIFIER)
        return 1;

      char *m_ident = tokens[p].data.identifier;

      if (tokens[p].kind == TOK_OPERATOR &&
          tokens[p].data.operator== OP_ASSIGN) {
        p++;

        if (tokens[p].kind == TOK_END)
          return 1;

        if (tokens[p].kind != TOK_CONSTANT ||
            tokens[p].data.constant_kind != CONST_INT)
          return 1;

        value = tokens[p].data.constant_int_value;
        p++;
      }

      num_members++;
      members =
          realloc_failsafe(NULL, sizeof(struct enum_member) * num_members);
      struct enum_member *new_member = &members[num_members - 1];
      new_member->value = value++;
      new_member->name = strdup_failsafe(m_ident);

      p++;
    }
  } else if (tokens[p].kind == TOK_SEPERATOR &&
             tokens[p].data.seperator == SEP_SEMICOLON) {

  } else {
    printf("expected members or semicolon\n");
    return 1;
  }

  *node = realloc_failsafe(NULL, sizeof(struct node));
  (**node).kind = NO_ENUM;
  (**node).data.enum_.is_decl = is_decl;
  (**node).data.enum_.name = strdup_failsafe(ident);
  (**node).data.enum_.num_members = num_members;
  (**node).data.enum_.members = members;

  return 0;
}

char parse(struct token *tokens, struct node **node) {
  return parse_type(tokens, node);
}

#ifdef DEBUG
void debug_node(struct node *node) {
  switch (node->kind) {
  case NO_ENUM:
    printf("NO_ENUM\n");
    printf("  name=%s\n", node->data.enum_.name);
    printf("  is_decl=%i\n", node->data.enum_.is_decl);
    if (node->data.enum_.is_decl) {
      printf("  num_members=%li\n", node->data.enum_.num_members);
      printf("  members\n");
      for (int i = 0; i < node->data.enum_.num_members; i++) {
        printf("    %s=%i\n", node->data.enum_.members[i].name,
               node->data.enum_.members[i].value);
      }
    }
    break;
  case NO_BINOP:
    printf("NO_BINOP\n");
    printf("  lhs: ");
    debug_node(node->data.binop.lhs);
    printf("\n");
    printf("  rhs: ");
    debug_node(node->data.binop.rhs);
    printf("\n");
    break;
  case NO_MEMBER_ACCESS:
    printf("NO_MEMBER_ACCESS\n");
    break;
  case NO_FUNCTION:
    printf("NO_FUNCTION\n");
    break;
  case NO_STRUCT:
    printf("NO_STRUCT\n");
    break;
  case NO_UNION:
    printf("NO_UNION\n");
    break;
  case NO_UNOP:
    printf("NO_UNOP\n");
    break;
  default:
    break;
  }
}
#endif

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_failsafe(source, source_len + 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;

#ifdef DEBUG
  debug_tokens(tokens);
#endif

  struct node *nodes = NULL;
  if (parse(tokens, &nodes)) {
    printf("parse failed\n");
    return 1;
  }
  if (!nodes) {
    printf("parse failed");
    return 1;
  }

#ifdef DEBUG
  debug_node(nodes);
#endif

  free_tokens(tokens);

  return 0;
}