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();
}

//-----------------------------------------------------------------------------
// Parsing helpers
//-----------------------------------------------------------------------------
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;
}

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

atom_expr = Int 
| Float 
| String 
| Identifier
| 'cast' '(' typespec ',' expr ')'
| 'size_type' '(' typespec ')'
| 'size_expr' '(' 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
*/
function Expr *parse_expr(Parser *p);

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_Identifier))){
    Expr *result = expr_identifier(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(p, TK_OpenParen))){
    Expr *expr = parse_expr(p);
    token_expect(p, TK_CloseParen);
    Expr *result = expr_paren(p->arena, token, expr);
    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_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_compound(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_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);
}

//-----------------------------------------------------------------------------
// Test code
//-----------------------------------------------------------------------------
function void expr_print(Expr *expr);
function void
token_print(Token *token){
  printf("%.*s", (S32)token->len, token->str);
}

function void
expr_compound_print(Expr_Compound_Field *field){
  switch(field->kind){
    case COMPOUND_Default: {
      expr_print(field->init);
    }break;
    case COMPOUND_Named: {
      printf("[%s] = ", field->name.s.str);
      expr_print(field->init);
    }break;
    case COMPOUND_Index: {
      printf("[");
      expr_print(field->index);
      printf("] = ");
      expr_print(field->init);
    }break;
    default: invalid_codepath;
  }
}

function void
expr_print(Expr *expr){
  switch(expr->kind) {
    case EK_Int:case EK_String:case EK_Identifier: {
      token_print(expr->token);
    } break;
    
    case EK_SizeExpr:{
      printf("size_expr(");
      expr_print(expr->size_expr.expr);
      printf(")");
    }break;
    
    case EK_Compound:{
      // typespec_print(p);
      printf("{");
      for(Expr_Compound_Field *n = expr->compound.first; n; n=n->next){
        expr_compound_print(n);
        if(n!=expr->compound.last) printf(",");
      }
      printf("}");
    } break;
    
    case EK_SizeType:{
      printf("size_type(");
      printf(")");
    }break;
    
    case EK_Paren:{
      printf("(");
      expr_print(expr->paren.expr);
      printf(")");
    } break;
    
    case EK_Field:{
      expr_print(expr->field.expr);
      printf(".%s", expr->field.name.s.str);
    } break;
    
    case EK_Binary:{
      printf("(");
      expr_print(expr->binary.left);
      token_print(expr->token);
      expr_print(expr->binary.right);
      printf(")");
    } break;
    
    case EK_PostfixUnary:{
      printf("(");
      expr_print(expr->unary.expr);
      token_print(expr->token);
      printf(")");
    } break;
    
    case EK_Unary:{
      printf("(");
      token_print(expr->token);
      expr_print(expr->unary.expr);
      printf(")");
    } break;
    
    case EK_Ternary:{
      printf("(");
      expr_print(expr->ternary.cond);
      printf("?");
      expr_print(expr->ternary.on_true);
      printf(":");
      expr_print(expr->ternary.on_false);
      printf(")");
    } break;
    
    case EK_Cast:{
      printf("(");
      printf("(");
      //print_typespec(expr->cast.type);
      printf(")");
      expr_print(expr->cast.expr);
      printf(")");
    } break;
    
    case EK_Index:{
      expr_print(expr->index.atom);
      printf("[");
      expr_print(expr->index.index);
      printf("]");
    }break;
    
    case EK_Call:{
      expr_print(expr->call.atom);
      printf("(");
      for(Expr_Compound_Field *n = expr->call.first; n; n=n->next){
        expr_compound_print(n);
        if(n!=expr->call.last) printf(",");
      }
      printf(")");
    }break;
    default: {invalid_codepath;} break;
  }
}


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 void
parse_test(){
  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 + --Not_Thing[156](Thing) + test_func(asd=func1, af=func2, gg=func3)"
                         );
  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),
    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]);
  }
  
  Expr *expr = parse_expr(p);
  expr_print(expr);
  
  arena_end_scratch();
}