/*
    attocc - A minimal C compiler.
    Copyright (C) 2025 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 <sys/cdefs.h>
#include <unistd.h>

#ifdef LINT
#define TEST
#define DEBUG
#endif

#define TRAP kill(getpid(), SIGTRAP);

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,
  TOK_ERROR,
};

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;
  char *error_message;
};

struct token {
  enum token_kind kind;
  union token_data data;
  unsigned long position;
};

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;
}

void *memcpy(void *dest, const void *src, unsigned long size) {
  char *dest_ = (char *)dest;
  char *src_ = (char *)src;
  while (size--)
    *dest_++ = *src_++;
  return dest;
}

// not to specification but this program only needs to check equality
int strncmp(const char *a, const char *b, unsigned long len) {
  while (len--) {
    if (*a != *b)
      return *a - *b;
    a++;
    b++;
  }
  return 0;
}
unsigned long strlen(const char *s) {
  int len = 0;
  while (*s++)
    len++;
  return len;
}
char *strdup(const char *s) {
  int len = strlen(s);
  char *new_s = realloc(NULL, len + 1);
  if (!new_s)
    return NULL;
  memcpy(new_s, s, len + 1);
  return new_s;
}

char *strdup_failsafe(char *s) {
  char *p = strdup(s);
  if (!p) {
    fprintf(stderr, "strdup failed\n");
    exit(2);
  }
  return p;
}

struct error {
  char *message;
  unsigned long position;
};

struct linemap {
  unsigned long *lines;
};

struct linemap linemap_new(char *source) {
  struct linemap lm;
  unsigned long i = 0;
  lm.lines = realloc_failsafe(NULL, sizeof(unsigned long));
  int num_lines = 1;
  lm.lines[0] = 0;
  while (source[i]) {
    if (source[i] == '\n') {
      num_lines += 1;
      lm.lines = realloc_failsafe(lm.lines, num_lines * sizeof(unsigned long));
      lm.lines[num_lines - 1] = i;
    }
    i += 1;
  }
  lm.lines =
      realloc_failsafe(lm.lines, (num_lines + 1) * sizeof(unsigned long));
  lm.lines[num_lines] = 0xffffffff;
  return lm;
}

int linemap_find(struct linemap *lm, unsigned long position) {
  int line = 0;
  while (lm->lines[line] < position)
    line += 1;
  return line;
}

void print_error(struct error error, char *filename, struct linemap *linemap) {
  int line = linemap_find(linemap, error.position);
  int column = error.position - linemap->lines[line];
  if (!error.message)
    error.message = "<no message>";
  printf("error: %s\n", error.message);
  printf("\tin %s:%i:%i\n", filename, line + 1, column + 1);
}

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_iter {
  char *end;
  char *start;
  char *p;
};

struct token_iter token_iter_new(char *source) {
  struct token_iter iter;
  iter.end = source + strlen(source);
  iter.start = source;
  iter.p = source;
  return iter;
}

struct token t_error(char *message) {
  struct token t;
  t.kind = TOK_ERROR;
  t.data.error_message = message;
  return t;
}

struct token token_iter_next(struct token_iter *iter) {
  char *p = iter->p;
  unsigned long remaining = iter->end - p;
  unsigned long position = p - iter->start;

  struct token tok;
  tok.kind = TOK_END;

  while (*p) {
    tok.position = position;

    //* 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 = '\0', d; (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++;
        tok.kind = TOK_SEPERATOR;
        tok.data.seperator = i;
        match = 1;
        break;
      }
    }
    if (match)
      break;

    //* 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) {
          p += strlen(op);
          tok.kind = TOK_OPERATOR;
          tok.data.operator= i;
          match = 1;
          break;
        }
      }
    }
    if (match)
      break;

    //* 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)])) {
          p += strlen(kw);
          tok.kind = TOK_KEYWORD;
          tok.data.keyword = i;
          match = 1;
          break;
        }
      }
    }
    if (match)
      break;

    //* 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--;
      tok.kind = TOK_CONSTANT;
      tok.data.constant_kind = CONST_INT;
      tok.data.constant_int_value = value;
      break;
    }

    //* 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';

      tok.kind = TOK_CONSTANT;
      tok.data.constant_kind = CONST_STR;
      tok.data.constant_str_value = str;
      break;
    }

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

      tok.kind = TOK_CONSTANT;
      tok.data.constant_kind = CONST_CHAR;
      tok.data.constant_char_value = chr;
      break;
    }

    //* identifier
    if (is_ident(p[0]) && !is_numeric(p[0])) {
      char *ident_start = p;
      for (char c; (c = *p++) && is_ident(c);)
        ;
      p--;
      int ident_len = p - ident_start;
      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';

      tok.kind = TOK_IDENTIFIER;
      tok.data.identifier = ident_str;
      break;
    }

    return t_error("unknown token");
  }

  iter->p = p;
  return tok;
}

void token_free(struct token tok) {
  switch (tok.kind) {
  case TOK_IDENTIFIER:
    free(tok.data.identifier);
    break;
  case TOK_CONSTANT:
    switch (tok.data.constant_kind) {
    case CONST_STR:
      free(tok.data.constant_str_value);
      break;
    default:
      break;
    }
  default:
    break;
  }
}

#ifdef DEBUG
void token_print(struct token tok) {
  printf("%4lu ", tok.position);
  switch (tok.kind) {
  case TOK_IDENTIFIER:
    printf("TOK_IDENTIFIER:%s", tok.data.identifier);
    break;
  case TOK_KEYWORD:
    printf("TOK_KEYWORD:%s", KEYWORD_NAMES[tok.data.keyword]);
    break;
  case TOK_CONSTANT:
    switch (tok.data.constant_kind) {
    case CONST_INT:
      printf("TOK_CONSTANT:CONST_INT:%i", tok.data.constant_int_value);
      break;
    case CONST_STR:
      printf("TOK_CONSTANT:CONST_STR:%s", tok.data.constant_str_value);
      break;
    case CONST_CHAR:
      printf("TOK_CONSTANT:CONST_CHAR:%c", tok.data.constant_char_value);
      break;
    }
    break;
  case TOK_OPERATOR:
      printf("TOK_OPERATOR:%s", OPERATOR_NAMES[tok.data.operator] );
      break;
  case TOK_SEPERATOR:
    printf("TOK_SEPERATOR:%s", SEPERATOR_NAMES[tok.data.seperator]);
    break;
  case TOK_ERROR:
    printf("TOK_ERROR:%s", tok.data.error_message);
    break;
  case TOK_END:
    printf("TOK_END");
    break;
  }
  printf("\n");
}
#endif

int token_step(struct token_iter *iter, struct token *a) {
  token_free(*a);
  *a = token_iter_next(iter);
  return a->kind == TOK_END || a->kind == TOK_ERROR;
}

enum type_kind {
  TY_PRIMITIVE,
  TY_ENUM,
  TY_STRUCT,
  TY_UNION,
};

struct struct_decl {};
struct union_decl {};

struct type {
  enum type_kind kind;
  int index;
};

struct constant {
  char *name;
  struct type type;
  int value;
};

struct global_context {
  int num_constants;
  struct constant *constants;
  int num_enums;
  char **enums;
};

int enum_decl(struct global_context *gcx, struct token_iter *iter,
              struct token *a, char *name) {

  gcx->enums =
      realloc_failsafe(gcx->enums, sizeof(char *) * (gcx->num_enums + 1));
  int enum_index = gcx->num_enums;
  gcx->enums[enum_index] = name;
  gcx->num_enums += 1;

  int value = 0;
  while (1) {
    if (a->kind == TOK_IDENTIFIER) {
      char *variant_name = strdup_failsafe(a->data.identifier);

      if (token_step(iter, a))
        return 1;

      if (a->kind == TOK_OPERATOR && a->data.operator== OP_ASSIGN) {
        if (token_step(iter, a))
          return 1;
        if (a->kind == TOK_CONSTANT && a->data.constant_kind == CONST_INT) {
          value = a->data.constant_int_value;
        } else {
          fprintf(stderr, "expected int const after enum assign\n");
          return 1;
        }
      } else if (a->kind == TOK_SEPERATOR && a->data.seperator == SEP_COMMA) {
        if (token_step(iter, a))
          return 1;
        continue;
      } else {
        fprintf(stderr, "expected assign or comma after enum ident\n");
        return 1;
      }

      struct constant con;
      con.type.kind = TY_ENUM;
      con.type.index = enum_index;
      con.value = value;
      con.name = variant_name;

      gcx->constants = realloc_failsafe(
          gcx->constants, sizeof(struct constant) * (gcx->num_constants + 1));
      gcx->constants[gcx->num_constants] = con;
      gcx->num_constants += 1;

      value += 1;
    } else if (a->kind == TOK_SEPERATOR && a->data.seperator == SEP_RCURLY) {
      if (token_step(iter, a))
        return 1;
      return 0;
    } else {
      fprintf(stderr, "expected enum ident or rcurly\n");
      return 1;
    }
  }
}

#ifdef DEBUG
void gcx_print(struct global_context *gcx) {
  printf("Constants:\n");
  for (int i = 0; i < gcx->num_constants; i++) {
    printf("\t%s = %i\n", gcx->constants[i].name, gcx->constants[i].value);
  }
}
#endif

int toplevel(struct token_iter *iter) {
  struct token a = token_iter_next(iter);
  struct global_context gcx;

  char *type_name = NULL;

  gcx.num_constants = 0;
  gcx.constants = NULL;
  gcx.num_enums = 0;
  gcx.enums = NULL;

  if (a.kind == TOK_KEYWORD) {
    switch (a.data.keyword) {
    case KW_ENUM:
      if (token_step(iter, &a))
        return 1;
      if (a.kind == TOK_IDENTIFIER) {
        type_name = strdup_failsafe(a.data.identifier);
        if (token_step(iter, &a))
          return 1;
      }
      if (a.kind == TOK_SEPERATOR && a.data.seperator == SEP_LCURLY) {
        if (token_step(iter, &a))
          return 1;
        if (enum_decl(&gcx, iter, &a, type_name))
          return 1;
      }
      break;
    default:
      printf("unhandled keyword: ");
      token_print(a);
      return 1;
    }
  }

#ifdef DEBUG
  gcx_print(&gcx);
#endif
  return 0;
}

#ifdef TEST
char test_clean = 1;
void assert(char cond, char *label) {
  if (!cond) {
    fprintf(stderr, "FAIL %s\n", label);
    test_clean = 0;
  }
}
void assert_eq(int a, int b, char *label) {
  if (a != b) {
    fprintf(stderr, "FAIL %s (%i == %i)\n", label, a, b);
    test_clean = 0;
  }
}
void test() {
  printf("sizeof(struct token) = %li\n", sizeof(struct token));
  printf("sizeof(struct token_iter) = %li\n", sizeof(struct token_iter));
  assert_eq(strlen("sizeof"), 6, "strlen 1");
  assert_eq(strlen(""), 0, "strlen 2");
  assert_eq(strlen("a"), 1, "strlen 3");
  assert(is_alpha('a'), "alpha 1");
  assert(is_alpha('z'), "alpha 2");
  assert(is_alpha('k'), "alpha 3");
  // TODO test tokenize
}
#endif

int main(int argc, char **argv) {
#ifdef TEST
  test();
  return test_clean ? 0 : 1;
#endif

  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 output");
    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 linemap linemap;
  struct token_iter iter;
  struct token tok;

  linemap = linemap_new(source);
  iter = token_iter_new(source);
  if (toplevel(&iter))
    fprintf(stderr, "compilation failed\n");

  //   while (1) {
  //     tok = token_iter_next(&iter);
  // #ifdef DEBUG
  //     token_print(tok);
  // #endif
  //     if (tok.kind == TOK_END)
  //       break;
  //     token_free(tok);
  //   };

  return 0;
}