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);
  }
  
  printf("Error: %s %s:%d\n", string.str, token->file.str, (S32)token->line);
  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();
}


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

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;
}

/*

add = [+-]
mul = [/%*]
compare = == | != | >= | > | <= | <
logical = [&|^] | && | ||

expr_atom = Int 
| Float 
| String 
| Identifier
| 'cast' '(' typespec ',' expr ')'
mul_expr = expr_atom (mul expr_atom)*
add_expr = mul_expr (add mul_expr)*
compare_expr = add_expr (compare add_expr)*
logical_expr = compare_expr (logical compare_expr)*
ternary_expr = logical_expr ('?' ternary_expr ':' ternary_expr)?
expr = logical_expr
*/

function Expr *
parse_expr_atom(Parser *p){
  Token *token = 0;
  if((token = token_match(p, TK_StringLit))){
    Expr *result = expr_str(p->arena, token);
    return result;
  }
  else if((token = token_match(p, TK_Int))){
    Expr *result = expr_int(p->arena, token);
    return result;
  }
  else if((token = token_match_keyword(p, keyword_cast))){
    token_expect(p, TK_OpenParen);
    token_expect(p, TK_Identifier);
    token_expect(p, TK_Comma);
    token_expect(p, TK_Identifier);
    token_expect(p, TK_CloseParen);
    return 0;
  }
  else{
    parser_push_error(p, token_get(p), "Failed to parse expression");
    return 0;
  }
}

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_atom(p);
  while(token_is_mul(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_atom(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_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_add(p);
  while(token_is_compare(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_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_compare(p);
  while(token_is_logical(p)){
    Token *op = token_next(p);
    Expr *right = parse_expr_compare(p);
    left = expr_binary(p->arena, op, left, right);
  }
  return left;
}

function Expr *
parse_expr_ternary(Parser *p){
  Expr *cond = parse_expr_logical(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);
}

function S64
eval_expr(Expr *expr){
  switch(expr->kind){
    case EK_Int: return expr->int_val; 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_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 void
parse_test(){
  Arena *scratch = arena_begin_scratch();
  String test_case = lit("32+52-242*2/424%5-23"
                         " 1<<5>>6<<2 "
                         " 1&&5*3 "
                         " 1&&5||0 "
                         " 1>5>=5==0 "
                         " 1>5 ? 1 : 2 "
                         );
  Parser parser = {
    .tokens = lex_stream(scratch, test_case, lit("expr_test")),
    .arena = scratch,
  };
  Parser *p = &parser;
  
  S64 t = 5;
  S64 test_val[] = {
    (32+52-242*2/424%5-23),
    (((1<<5)>>6)<<2),
    1&&(t*3),
    (1&&t)||0,
    1>t>=t==0,
    1>t ? 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]);
  }
  
  arena_end_scratch();
}