typedef struct Parser_Error Parser_Error;

struct Parser_Error{
  Parser_Error *next;
  String message;
  Token *token;
};

typedef struct Parser{
  Token_Array tokens;
  Arena *arena;
  
  Parser_Error *first_error;
  Parser_Error *last_error;
}Parser;

function void
parser_push_error(Parser *p, Token *token, char *str, ...){
  String string;
  {
    va_list args1, args2;
    va_start(args1, str);
    va_copy(args2, args1);
    string.len = vsnprintf(0, 0, str, args2);
    va_end(args2);
    
    string.str = arena_push_size(p->arena, string.len + 1);
    vsnprintf((char*)string.str, string.len + 1, str, args1);
    va_end(args1);
  }
  
  // @Note(Krzosa): Print nice error message
  {
    printf("\nError: %s %s:%d\n", string.str, token->file.str, (S32)token->line);
    
    // @Note(Krzosa): Print error line
    {
      int i = 0;
      while(token->line_begin[i]!='\n' && token->line_begin[i]!=0) i++;
      printf("%.*s\n", i, token->line_begin);
      
      // @Note(Krzosa): Print error marker
      int token_i = token->str - token->line_begin;
      for(int i = 0; i < token_i-2; i++) printf(" ");
      printf("^^^^^^\n");
    }
  }
  
  Parser_Error *error = arena_push_struct(p->arena, Parser_Error);
  error->message = string;
  error->next = 0;
  error->token = token;
  SLLQueuePush(p->first_error, p->last_error, error);
  
  __debugbreak();
}

//-----------------------------------------------------------------------------
// Parsing helpers
//-----------------------------------------------------------------------------
function Token *
token_get(Parser *p){
  Token *result = token_array_iter_peek(&p->tokens, 0);
  return result;
}

function Token *
token_peek(Parser *p, S64 i){
  Token *result = token_array_iter_peek(&p->tokens, i);
  return result;
}

function Token *
token_peek_is(Parser *p, Token_Kind kind, S64 i){
  Token *result = token_peek(p, i);
  if(result->kind == kind)
    return result;
  return 0;
}

function Token *
token_peek_is_keyword(Parser *p, Intern_String keyword, S64 i){
  assert(lex_is_keyword(keyword));
  Token *result = token_peek(p, i);
  if(result->kind == TK_Keyword && intern_compare(result->intern_val, keyword))
    return result;
  return 0;
}

function Token *
token_is(Parser *p, Token_Kind kind){
  Token *result = token_get(p);
  if(result->kind == kind)
    return result;
  return 0;
}

function Token *
token_next(Parser *p){
  Token *result = token_array_iter_next(&p->tokens);
  return result;
}

function Token *
token_match(Parser *p, Token_Kind kind){
  Token *token = token_get(p);
  if(token->kind == kind){
    token = token_next(p);
    return token;
  }
  return 0;
}

function Token *
token_match_keyword(Parser *p, Intern_String string){
  Token *token = token_get(p);
  if(token->kind == TK_Keyword){
    if(intern_compare(token->intern_val, string)){
      token = token_next(p);
      return token;
    }
  }
  return 0;
}

function Token *
token_expect(Parser *p, Token_Kind kind){
  Token *token = token_get(p);
  if(token->kind == kind){
    token = token_next(p);
    return token;
  }
  parser_push_error(p, token, "Expected token of kind: %s, got instead token of kind: %s.", token_kind_string[kind], token_kind_string[token->kind]);
  return 0;
}

function Typespec *parse_typespec(Parser *p);
function Expr *parse_expr(Parser *p);
//-----------------------------------------------------------------------------
// Expression parsing
//-----------------------------------------------------------------------------
/*
add = [+-]
mul = [/%*]
compare = == | != | >= | > | <= | <
logical = [&|^] | && | ||
unary = [&*-!~+] | ++ | --

atom_expr = Int 
| Float 
| String 
| Identifier
| 'cast' '(' typespec ',' expr ')'
| 'size_type' '(' typespec ')'
| 'size_expr' '(' expr ')'
| '{' compound_expr '}'
| '(' expr ')' 
| '(' ':' typespec ')' '{' compound_expr '}'
postfix_expr = atom_expr ('[' expr ']' | '.' Identifier | ++ | -- | '(' expr_list ')')*
unary_expr = unary ? unary_expr : atom_expr
mul_expr = atom_expr (mul atom_expr)*
add_expr = mul_expr (add mul_expr)*
logical_expr = add_expr (logical add_expr)*
compare_expr = logical_expr (compare logical_expr)*
ternary_expr = compare_expr ('?' ternary_expr ':' ternary_expr)?
expr = logical_expr

Compound literals
- (:[23]*Type){}
 - Type{}
- { }

*/
function Expr_Compound_Field *
parse_expr_compound_field(Parser *p){
  Token *token = token_get(p);
  Expr_Compound_Field *result = 0;
  if(token_match(p, TK_OpenBracket)){
    Expr *index = parse_expr(p);
    token_expect(p, TK_CloseBracket);
    token_expect(p, TK_Assign);
    Expr *expr = parse_expr(p);
    result = expr_compound_index(p->arena, token, index, expr);
  }
  else{
    Expr *expr = parse_expr(p);
    if((token = token_match(p, TK_Assign))){
      if(expr->kind != EK_Identifier){
        parser_push_error(p, token, "Failed to parse compound literal, required identifier as left value");
      }
      result = expr_compound_named(p->arena, token, expr->intern_val, parse_expr(p));
      
    }
    else{
      result = expr_compound_default(p->arena, token, expr);
    }
  }
  return result;
}

function Expr *
parse_expr_compound(Parser *p, Typespec *typespec){
  Token *token = token_expect(p, TK_OpenBrace);
  Expr *expr = expr_compound(p->arena, token, typespec);
  while(!token_is(p, TK_CloseBrace)){
    Expr_Compound_Field *field = parse_expr_compound_field(p);
    expr_compound_push(expr, field);
    if(!token_match(p, TK_Comma)){
      break;
    }
  }
  token_expect(p, TK_CloseBrace);
  return expr;
}

function Expr *
parse_expr_atom(Parser *p){
  Expr *result = 0;
  Token *token = token_get(p);
  if(token_match(p, TK_StringLit)){
    result = expr_str(p->arena, token);
  }
  else if(token_match(p, TK_Identifier)){
    if(token_is(p, TK_OpenBrace)){
      Typespec *typespec = typespec_name(p->arena, token, token->intern_val);
      result = parse_expr_compound(p, typespec);
    }
    else{
      result = expr_identifier(p->arena, token);
    }
  }
  else if(token_match(p, TK_Int)){
    result = expr_int(p->arena, token);
  }
  else if(token_is(p, TK_OpenBrace)){
    result = parse_expr_compound(p, 0);
  }
  
  else if(token_match(p, TK_OpenParen)){
    if(token_match(p, TK_Colon)){
      Typespec *typespec = parse_typespec(p);
      token_expect(p, TK_CloseParen);
      result = parse_expr_compound(p, typespec);
    }
    else{
      Expr *expr = parse_expr(p);
      token_expect(p, TK_CloseParen);
      result = expr_paren(p->arena, token, expr);
    }
  }
  else if(token_match_keyword(p, keyword_cast)){
    token_expect(p, TK_OpenParen);
    Typespec *typespec = parse_typespec(p);
    token_expect(p, TK_Comma);
    Expr *expr = parse_expr(p);
    token_expect(p, TK_CloseParen);
    result = expr_cast(p->arena, token, typespec, expr);
  }
  else{
    parser_push_error(p, token, "Failed to parse expression");
  }
  return result;
}

function B32
token_is_postfix(Parser *p){
  Token *token = token_get(p);
  B32 result = token->kind == TK_OpenBracket
    || token->kind == TK_OpenParen
    || token->kind == TK_Dot
    || token->kind == TK_Increment
    || token->kind == TK_Decrement;
  return result;
}

function Expr_Compound_Field *
parse_expr_function_argument(Parser *p){
  Token *token = token_get(p);
  Expr_Compound_Field *result = 0;
  Expr *expr1 = parse_expr(p);
  if(token_match(p, TK_Assign)){
    if(expr1->kind != EK_Identifier){
      parser_push_error(p, token, "Failed to parse named function argument, required identifier as left value");
    }
    Expr *expr2 = parse_expr(p);
    result = expr_compound_named(p->arena, token, expr1->intern_val, expr2);
  }
  else{
    result = expr_compound_default(p->arena, token, expr1);
  }
  return result;
}

function Expr *
parse_expr_postfix(Parser *p){
  Expr *left = parse_expr_atom(p);
  while(token_is_postfix(p)){
    Token *token = 0;
    if((token = token_match(p, TK_OpenBracket))){
      Expr *size = parse_expr(p);
      token_expect(p, TK_CloseBracket);
      left = expr_index(p->arena, token, left, size);
    }
    else if((token = token_match(p, TK_OpenParen))){
      left = expr_call(p->arena, token, left);
      if(!token_is(p, TK_CloseParen)){
        do {
          Expr_Compound_Field *field = parse_expr_function_argument(p);
          expr_call_push(left, field);
        } while(token_match(p, TK_Comma));
      }
      token_expect(p, TK_CloseParen);
    }
    else if(token_match(p, TK_Dot)){
      token = token_expect(p, TK_Identifier);
      left = expr_field(p->arena, token, left);
    }
    else{
      token = token_next(p);
      assert(token->kind == TK_Increment || token->kind == TK_Decrement);
      left = expr_postfix_unary(p->arena, token, left);
    }
  }
  return left;
}

function B32
token_is_unary(Parser *p){
  Token *token = token_get(p);
  B32 result = token->kind == TK_Add 
    || token->kind == TK_Increment
    || token->kind == TK_Decrement
    || token->kind == TK_Sub
    || token->kind == TK_Mul
    || token->kind == TK_BitAnd
    || token->kind == TK_Neg
    || token->kind == TK_Not;
  return result;
}

function Expr *
parse_expr_unary(Parser *p){
  if(token_is_unary(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_unary(p);
    Expr *result = expr_unary(p->arena, op, right);
    return result;
  }
  else{
    return parse_expr_postfix(p);
  }
}

function B32
token_is_mul(Parser *p){
  Token *token = token_get(p);
  B32 result = token->kind >= TK_FirstMul && token->kind <= TK_LastMul;
  return result;
}

function Expr *
parse_expr_mul(Parser *p){
  Expr *left = parse_expr_unary(p);
  while(token_is_mul(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_unary(p);
    left = expr_binary(p->arena, op, left, right);
  }
  return left;
}

function B32
token_is_add(Parser *p){
  Token *token = token_get(p);
  B32 result = token->kind >= TK_FirstAdd && token->kind <= TK_LastAdd;
  return result;
}

function Expr *
parse_expr_add(Parser *p){
  Expr *left = parse_expr_mul(p);
  while(token_is_add(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_mul(p);
    left = expr_binary(p->arena, op, left, right);
  }
  return left;
}

function B32
token_is_logical(Parser *p){
  Token *token = token_get(p);
  B32 result = token->kind >= TK_FirstLogical && token->kind <= TK_LastLogical;
  return result;
}

function Expr *
parse_expr_logical(Parser *p){
  Expr *left = parse_expr_add(p);
  while(token_is_logical(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_add(p);
    left = expr_binary(p->arena, op, left, right);
  }
  return left;
}

function B32
token_is_compare(Parser *p){
  Token *token = token_get(p);
  B32 result = token->kind >= TK_FirstCompare && token->kind <= TK_LastCompare;
  return result;
}

function Expr *
parse_expr_compare(Parser *p){
  Expr *left = parse_expr_logical(p);
  while(token_is_compare(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_logical(p);
    left = expr_binary(p->arena, op, left, right);
  }
  return left;
}

function Expr *
parse_expr_ternary(Parser *p){
  Expr *cond = parse_expr_compare(p);
  Token *token = 0;
  if((token = token_match(p, TK_Question))){
    Expr *on_true = parse_expr_ternary(p);
    token_expect(p, TK_Colon);
    Expr *on_false = parse_expr_ternary(p);
    Expr *result = expr_ternary(p->arena, token, cond, on_true, on_false);
    return result;
  }
  return cond;
}

function Expr *
parse_expr(Parser *p){
  return parse_expr_ternary(p);
}

//-----------------------------------------------------------------------------
// Type specifier parsing
//-----------------------------------------------------------------------------
/*
 base_type = NAME 
| '(' type_list? ')' type?

type = ('*' | '[' expr ']')* base_type

Examples: 
[32]*U32 - Array of 32 pointers to U32
**CustomDataType - Pointer to pointer of CustomDataType
(*U32, S64) **S64 - Function pointer 
(CoolType: optional, S32) - Implicit void return value

*/
function Typespec *
parse_typespec_function(Parser *p, Token *token){
  Typespec *result = typespec_function(p->arena, token, 0);
  if(!token_is(p, TK_CloseParen)) 
    for(;;) {
    
    // Optional name
    Token *name = 0;
    if((token = token_is(p, TK_Identifier))){
      if(token_peek_is(p, TK_Colon, 1)){
        token_next(p);
        token_next(p);
        name = token;
      }
    }
    
    // Parse type
    Typespec *arg = parse_typespec(p);
    if(name) 
      arg = typespec_named_argument(p->arena, name, arg, name->intern_val);
    typespec_function_push(result, arg);
    
    if(!token_match(p, TK_Comma)){
      break;
    }
  }
  token_expect(p, TK_CloseParen);
  if(token_is(p, TK_Identifier) 
     || token_is(p, TK_OpenParen)
     || token_is(p, TK_Mul)
     || token_is(p, TK_OpenBracket))
    result->func.ret = parse_typespec(p);
  else
    result->func.ret = typespec_name(p->arena, token_get(p), intern_void);
  
  return result;
}

// [10]*int - Array of 10 pointers to ints
function Typespec *
parse_typespec_recurse(Parser *p){
  Token *token = token_get(p);
  if(token_match(p, TK_Mul)){
    Typespec *result = parse_typespec_recurse(p);
    result = typespec_pointer(p->arena, token, result);
    return result;
  }
  else if(token_match(p, TK_OpenBracket)){
    Expr *expr = parse_expr(p);
    token_expect(p, TK_CloseBracket);
    Typespec *result = parse_typespec_recurse(p);
    result = typespec_array(p->arena, token, result, expr);
    return result;
  }
  else if(token_match(p, TK_OpenParen)){
    Typespec *result = parse_typespec_function(p, token);
    return result;
  }
  else if(token_match(p, TK_Identifier)){
    Typespec *result = typespec_name(p->arena, token, token->intern_val);
    return result;
  }
  else{
    parser_push_error(p, token, "Failed to parse type, unexpected token");
    return 0;
  }
}

function Typespec *
parse_typespec(Parser *p){
  Typespec *result = parse_typespec_recurse(p);
  return result;
}

//-----------------------------------------------------------------------------
// Parsing decls
//-----------------------------------------------------------------------------
/*
name::(param:U32)*U32{}
name::struct{}
name::union{}
name::enum{}

name::typedef = name2;
name::const   = 4254;

// Thing::struct{
//   var1, var2: U32;
//   union {
//     thing: *S64;
  //   }
//   named: union {
//     data: [24]U32;
//   }
// }
*/
function void 
parse_note_list(Parser *p, Note *parent) {
  if(token_match(p, TK_OpenParen)) {
    if(token_match(p, TK_CloseParen)){
      return;
    }
    do {
      Token *name = token_expect(p, TK_Identifier);
      Note *current = note_push_new(p->arena, parent, name, name->intern_val, 0);
      parse_note_list(p, current);
      if(token_match(p, TK_Assign)) {
        current->expr = parse_expr(p);
      }
    } while(token_match(p, TK_Comma));
    token_expect(p, TK_CloseParen);
  }
}

function void 
parse__notes(Parser *p, Note *result) {
  while(token_match(p, TK_At)) {
    Token *name = token_expect(p, TK_Identifier);
    Note *current = note_push_new(p->arena, result, name, name->intern_val, 0);
    parse_note_list(p, current);
    if(token_match(p, TK_Assign)) {
      current->expr = parse_expr(p);
    }
    token_match(p, TK_Semicolon);
  }
}

function Note
parse_notes(Parser *p){
  Note result = {0};
  parse__notes(p, &result);
  return result;
}

function Expr *
parse_assign_expr(Parser *p){
  if(token_match(p, TK_Assign))
    return parse_expr(p);
  return 0;
}

function Typespec *
parse_optional_type(Parser *p, Intern_String type){
  Typespec *result = 0;
  if(token_match(p, TK_Colon)){
    result = parse_typespec(p);
  }
  else{
    result = typespec_name(p->arena, token_get(p), type);
  }
  return result;
}

function Decl *
parse_enum(Parser *p, Token *name){
  Typespec *typespec = parse_optional_type(p, intern_int);
  Decl *result = decl_enum(p->arena, name, name->intern_val, typespec);
  token_expect(p, TK_OpenBrace);
  do {
    Note notes = parse_notes(p);
    Token *val = token_expect(p, TK_Identifier);
    Expr *expr = parse_assign_expr(p);
    decl_enum_push(p->arena, result, val, val->intern_val, expr, &notes);
    if(!token_match(p, TK_Comma)){
      break;
    }
  }while(!token_is(p, TK_CloseBrace));
  token_expect(p, TK_CloseBrace);
  return result;
}

function void
parse_var_decl(Parser *p, Decl *parent, Token *name, Note *notes){
  Token *name_stack[64];
  S64 name_stack_len = 0;
  name_stack[name_stack_len++] = name;
  while(token_match(p, TK_Comma))
    name_stack[name_stack_len++] = token_expect(p, TK_Identifier);
  token_expect(p, TK_Colon);
  Typespec *typespec = parse_typespec(p);
  token_expect(p, TK_Semicolon);
  for(S64 i = 0; i < name_stack_len; i++){
    Decl *decl = decl_variable(p->arena, name_stack[i], name_stack[i]->intern_val, typespec, 0);
    decl_pass_notes(decl, notes);
    decl_struct_push(parent, decl);
  }
}

function Decl *
parse_struct(Parser *p, Token *name, Decl_Kind struct_kind){
  Intern_String intern_name = name ? name->intern_val : (Intern_String){0};
  Token *token = name ? name : token_get(p);
  Decl *result = decl_struct(p->arena, struct_kind, token, intern_name);
  token_expect(p, TK_OpenBrace);
  do {
    Note notes = parse_notes(p);
    Token *token = token_get(p);
    if(token_match_keyword(p, keyword_union)){
      Decl *decl = parse_struct(p, 0, DECL_SubUnion);
      decl_pass_notes(decl, &notes);
      decl_struct_push(result, decl);
    }
    else if(token_match_keyword(p, keyword_struct)){
      Decl *decl = parse_struct(p, 0, DECL_SubStruct);
      decl_pass_notes(decl, &notes);
      decl_struct_push(result, decl);
    }
    else if(token_match(p, TK_Identifier)){
      if(token_is(p, TK_Colon)){
        if(token_peek_is_keyword(p, keyword_union, 1)){
          token_next(p); token_next(p);
          Decl *decl = parse_struct(p, token, DECL_SubUnion);
          decl_pass_notes(decl, &notes);
          decl_struct_push(result, decl);
        }
        else if(token_peek_is_keyword(p, keyword_struct, 1)){
          token_next(p); token_next(p);
          Decl *decl = parse_struct(p, token, DECL_SubStruct);
          decl_pass_notes(decl, &notes);
          decl_struct_push(result, decl);
        }
        else{
          parse_var_decl(p, result, token, &notes);
        }
      }
      else{
        parse_var_decl(p, result, token, &notes);
      }
    }
    else{
      parser_push_error(p, token, "Failed to parse struct, unexpected token of kind '%s'", token_kind_string[token->kind]);
    }
  } while(!token_match(p, TK_CloseBrace));
  return result;
}

function Decl *
parse_typedef(Parser *p, Token *name){
  token_expect(p, TK_Assign);
  Typespec *typespec = parse_typespec(p);
  token_expect(p, TK_Semicolon);
  Decl *result = decl_typedef(p->arena, name, name->intern_val, typespec);
  return result;
}

function Decl *
parse_const(Parser *p, Token *name){
  Typespec *typespec = 0;
  if(token_match(p, TK_Colon))
    typespec = parse_typespec(p);
  token_expect(p, TK_Assign);
  Expr *expr = parse_expr(p);
  token_expect(p, TK_Semicolon);
  Decl *result = decl_const(p->arena, name, name->intern_val, expr, typespec);
  return result;
}

function Decl *
parse_function(Parser *p, Token *name){
  Decl *result = decl_function(p->arena, name, name->intern_val, 0);
  if(!token_is(p, TK_CloseParen)){
    do{
      name = token_expect(p, TK_Identifier);
      token_expect(p, TK_Colon);
      Typespec *typespec = parse_typespec(p);
      decl_func_push(p->arena, result, name, name->intern_val, typespec);
    } while(token_match(p, TK_Comma));
  }
  token_expect(p, TK_CloseParen);
  result->func_decl.ret = parse_optional_type(p, intern_void);
  token_expect(p, TK_Semicolon);
  return result;
}

function B32
parse_decl(Parser *p, Decl *parent){
  Token *name = 0;
  Decl *result = 0;
  Note note = parse_notes(p);
  if((name = token_match(p, TK_Identifier))){
    if(token_match(p, TK_DoubleColon)){
      Token *token = 0;
      if((token = token_match_keyword(p, keyword_enum))){
        result = parse_enum(p, name);
      }
      else if((token = token_match_keyword(p, keyword_union))){
        result = parse_struct(p, name, DECL_Union);
      }
      else if((token = token_match_keyword(p, keyword_struct))){
        result = parse_struct(p, name, DECL_Struct);
      }
      else if((token = token_match_keyword(p, keyword_typedef))){
        result = parse_typedef(p, name);
      }
      else if((token = token_match_keyword(p, keyword_const))){
        result = parse_const(p, name);
      }
      else if((token = token_match(p, TK_OpenParen))){
        result = parse_function(p, name);
      }
      else{
        token = token_get(p);
        parser_push_error(p, token, "Expected a declaration keyword. Got instead: %s", token_kind_string[token->kind]);
      }
    }
    else{
      Token *token = token_get(p);
      parser_push_error(p, token, "Expected a declaration which starts with token '::' got instead"
                        "token '%s'", token_kind_string[token->kind]);
    }
  }
  
  if(result){
    decl_pass_notes(result, &note);
    decl_list_push(parent, result);
    return true;
  }
  return false;
}

function Decl
parse_decls(Parser *p){
  Decl decl_list = {.kind=DECL_List};
  while(!token_is(p, TK_End)){
    B32 success = parse_decl(p, &decl_list);
    if(!success){
      parser_push_error(p, token_get(p), "Failed to parse decls, unexpected token!");
    }
  }
  return decl_list;
}

//-----------------------------------------------------------------------------
// Statement parsing
//-----------------------------------------------------------------------------
/*
stmt_list = '{' stmt* '}'
stmt = 
| stmt_list
 | 'return' expr ';'
 | 'if' expr stmt_list
 | 'for' simple_stmt_list ';' expr ';' simple_stmt_list stmt_list
| 'for' expr stmt_list
| expr assign? ';'
//| 'while' expr stmt_or_stmt_list

*/

function Stmt *
parse_stmt(Parser *p){
  Note notes = parse_notes(p);
  Stmt *result = 0;
  if(token_match_keyword(p, keyword_if)){
    
  }
  else if(token_match_keyword(p, keyword_for)){
    
  }
  else if(token_match_keyword(p, keyword_while)){
    
  }
  else if(token_match_keyword(p, keyword_return)){
    
  }
  else if(token_match(p, TK_OpenBrace)){
    // Scope
  }
  else{
    // Expr
  }
  return result;
}

//-----------------------------------------------------------------------------
// Test code
//-----------------------------------------------------------------------------
function S64
eval_expr(Expr *expr){
  switch(expr->kind){
    case EK_Int: return expr->int_val; break;
    case EK_Unary:{
      S64 left = eval_expr(expr->unary.expr);
      switch(expr->unary.op){
        case TK_Not: return !left; break;
        case TK_Neg: return ~left; break;
        case TK_Sub: return -left; break;
        case TK_Add: return +left; break;
        default: invalid_codepath;
      }
    } break;
    case EK_Ternary:{
      S64 cond = eval_expr(expr->ternary.cond);
      if(cond) return eval_expr(expr->ternary.on_true);
      else return eval_expr(expr->ternary.on_false);
    } break;
    case EK_Paren: return eval_expr(expr->paren.expr); break;
    case EK_Binary: {
      S64 left = eval_expr(expr->binary.left);
      S64 right = eval_expr(expr->binary.right);
      switch(expr->binary.op){
        case TK_Add: return left + right; break;
        case TK_Sub: return left - right; break;
        case TK_Mul: return left * right; break;
        case TK_Div: return left / right; break;
        case TK_Mod: return left % right; break;
        case TK_Equals: return left == right; break;
        case TK_NotEquals: return left != right; break;
        case TK_GreaterThenOrEqual: return left >= right; break;
        case TK_LesserThenOrEqual: return left <= right; break;
        case TK_GreaterThen: return left > right; break;
        case TK_LesserThen: return left < right; break;
        case TK_BitAnd: return left & right; break;
        case TK_BitOr: return left | right; break;
        case TK_BitXor: return left ^ right; break;
        case TK_And: return left && right; break;
        case TK_Or: return left || right; break;
        case TK_LeftShift: return left << right; break;
        case TK_RightShift: return left >> right; break;
        default: invalid_codepath;
      }
    } break;
    default: invalid_codepath;
  }
  return 0;
}

function Parser
parser_make(Arena *arena){
  Parser result = {
    .tokens = lex_make_token_array(arena),
    .arena = arena,
  };
  return result;
}

function void
parser_restream(Parser *p, String stream, String file){
  lex_restream(&p->tokens, stream, file);
}

function Parser
parser_make_stream(Arena *arena, String stream, String file){
  Parser parser = parser_make(arena);
  lex_restream(&parser.tokens, stream, file);
  return parser;
}

function void
parser_add_stream(Parser *p, String string, String file){
  lex_add_stream(&p->tokens, string, file);
}

function void
parse_test_expr(){
  Arena *scratch = arena_begin_scratch();
  String test_case = lit("32+52-242*2/424%5-23"
                         " 1<<5>>6<<2 "
                         " 5*(4/3)*(2+5) "
                         " 0&1 == 1&0 "
                         " 1&&5*3 "
                         " 1&&5||0 "
                         " 1>5>=5==0 "
                         " 1>5 ? 1 : 2 "
                         " !!!!!1 "
                         " ~~1 + -!2 "
                         " 1 + ++Thing[12]++ + ++Thing[12].expr +" 
                         );
  Parser parser = parser_make_stream(scratch, test_case, lit("Big_Expr"));
  Parser *p = &parser;
  
  S64 t = 5;
  S64 test_val[] = {
    (32+52-242*2/424%5-23),
    (((1<<5)>>6)<<2),
    5*(4/3)*(2+5),
    (0&1) == (1&0),
    1&&(t*3),
    (1&&t)||0,
    1>t>=t==0,
    1>t ? 1 : 2,
    !!!!!1,
    ~~1 + -!2,
  };
  for(int i = 0; i < buff_cap(test_val); i++){
    Expr *expr = parse_expr(p);
    S64 val = eval_expr(expr);
    assert(val == test_val[i]);
  }
  
  String exprs[] = {
    lit("cast([12](thing: U32, qwe: *U32) [32]Result, (123+234))"),
    lit("cast((thing: U32, qwe: *U32), (123+234))"),
    lit("(:(U32,U32)){Thing=10}"),
    lit("--Not_Thing[156](Thing) + test_func(asd=func1, af=func2, gg=func3)"),
    lit("(:[23]*Type){Thing=10}"),
    lit("cast(**Data,{Thing=10})"),
    lit("(:[64]S64){1,2,3,4,5}"),
    lit("Data_Type{1,2,3,4,5}"),
  };
  for(SizeU i = 0; i < buff_cap(exprs); i++){
    parser_restream(p, exprs[i], lit("Test_Exprs"));
    Expr *expr = parse_expr(p);
    expr_print(expr);
    printf("\n");
  }
  
  arena_end_scratch();
}

function void
parse_test_decls(){
  Arena *scratch = arena_begin_scratch();
  Parser p = parser_make(scratch);
  
  String decls[] = {
    lit("Thing::enum: U64{ Thing_1 = 1<<1, Thing_2 = 2 }"),
    lit("Struct::struct{ thing, thing2: *S64; struct { thing:U32; thing2: [64]Vec2; }  inner: struct {i:U32;} }"),
  };
  for(SizeU i = 0; i < buff_cap(decls); i++){
    parser_restream(&p, decls[i], lit("Decl_Test"));
    Decl decl = parse_decls(&p);
    assert(decl.list_decl.first);
    decl_print(decl.list_decl.first);
  }
  arena_end_scratch();
}

function void
parse_test_from_file(){
  const String FILENAME = lit("test.cc");
  Arena *scratch = arena_begin_scratch();
  String file = os_read_file(scratch, FILENAME);
  Parser p = parser_make_stream(scratch, file, FILENAME);
  Decl d = parse_decls(&p);
  decl_print(&d);
  arena_end_scratch();
}

function void
parse_test(){
  parse_test_expr();
  parse_test_decls();
  parse_test_from_file();
}