//-----------------------------------------------------------------------------
// AST
//-----------------------------------------------------------------------------
enum Ast_Kind: U32{
  AST_NONE,

  AST_PACKAGE,

  AST_SCOPE,
  AST_VALUE,
  AST_CAST,
  AST_IDENT,
  AST_INDEX,
  AST_UNARY,
  AST_BINARY,
  AST_CALL_ITEM,
  AST_CALL,

  AST_TYPE,
  AST_VAR,
  AST_CONST,
  AST_POINTER,
  AST_ARRAY,
  AST_FOR,
  AST_IF,
  AST_IF_NODE,
  AST_RETURN,
  AST_BLOCK,
  AST_PASS,
  AST_LAMBDA,
  AST_LAMBDA_EXPR,
  AST_LAMBDA_ARG,
  AST_ENUM,
  AST_ENUM_MEMBER,
  AST_STRUCT,
};

typedef U32 Ast_Flag;
enum{
  AST_EXPR = bit_flag(1),
  AST_STMT = bit_flag(2),
  AST_BINDING = bit_flag(3),
  AST_AGGREGATE = bit_flag(4),
  AST_AGGREGATE_CHILD = bit_flag(5),
  AST_ITEM_INCLUDED = bit_flag(6),
  AST_ATOM = bit_flag(7),
  AST_FOREIGN = bit_flag(8),
  AST_DECL = bit_flag(9),
  AST_PACKAGE_LEVEL = bit_flag(10),
};

struct Ast{
  U64 id;
  Token *pos;

  Ast_Kind kind;
  Ast_Scope *parent_scope;
  Ast_Flag flags;
};

struct Ast_Resolved_Type;
struct Ast_Expr:Ast{};

#define VALUE_FIELDS             \
Ast_Resolved_Type *type;         \
union{                           \
  bool               bool_val;   \
  F64                f64_val;    \
  Intern_String      intern_val; \
  BigInt             big_int_val;\
  Ast_Resolved_Type *type_val;   \
};
#define INLINE_VALUE_FIELDS union{Value value; struct{VALUE_FIELDS};}
struct Value{VALUE_FIELDS};
  // BigInt             big_int_val;

struct Ast_Atom: Ast_Expr{
  Ast_Decl *resolved_decl;
  INLINE_VALUE_FIELDS;
};

struct Ast_Call_Item: Ast_Expr{
  Ast_Atom *name; // index | name
  Ast_Expr *item;
};

struct Ast_Call: Ast_Expr{
  Ast_Resolved_Type *type; // @todo: to map
  Ast_Expr *name;
  Array<Ast_Call_Item *> exprs;
};

struct Ast_Unary: Ast_Expr{
  Token_Kind op;
  Ast_Expr *expr;
  Ast_Resolved_Type *type;
  U64 padding[2]; // For folding constants into atoms
};

struct Ast_Cast: Ast_Expr{
  Ast_Expr *expr;
  Ast_Expr *typespec;
  Ast_Resolved_Type *before_type;
  Ast_Resolved_Type *after_type;
};

struct Ast_Index: Ast_Expr{
  Ast_Expr *expr;
  Ast_Expr *index;
  Ast_Resolved_Type *original_type;
};

struct Ast_Binary: Ast_Expr{
  Token_Kind op;
  Ast_Expr *left;
  Ast_Expr *right;

  Ast_Resolved_Type *type;
};

// Problem: We are parsing out of order, in the middle of parsing a function
// we can jump down a different function, we cant therfore use global map.
// Each scope needs to have it's checked locals list. To lookup syms we need to
// look into global scope and to the locals list.
//

struct Ast_Return: Ast{
  Ast_Expr *expr;
};

struct Ast_If_Node: Ast{
  Ast_Expr  *expr ;
  Ast_Scope *scope;
  Ast_Binary*init;
};

struct Ast_If: Ast{
  Array<Ast_If_Node *> ifs;
};

struct Ast_Pass: Ast{};

struct Ast_For: Ast{
  Ast_Expr *init;
  Ast_Expr *cond;
  Ast_Expr *iter;
  Ast_Scope *scope;
};

struct Ast_Lambda : Ast_Expr {
  Array<Ast_Decl *> args;
  Ast_Expr         *ret;
  Ast_Scope        *scope;
  B32               has_var_args;
};

struct Ast_Array: Ast_Expr{
  Ast_Expr *base;
  Ast_Expr *expr;
  Ast_Resolved_Type *type;
};

/*
How does current declaration order resolver works:
* First we put all the global declarations into the global scope (when parsing) all unresolved
  * All the types are declared INCOMPLETE and RESOLVED
* We descent the tree by resolving each of the named declarations, we resolve by their name
  When we start resolving we set RESOLVING flag and when we complete RESOLVED flag
  and put into ordered list
* When we meet a symbol (named declaration) while descending the tree,
  we resolve that symbol instead before resolving current declaration.
* When we meet a declaration that requires size of a type - field access, var assignment,
  we need to call "complete_type", it sets COMPLETING flag.
  This call resolves all the dependencies of that type,
  sets size of type and marks it as COMPLETE and puts into ordered list.
  If it detects COMPLETING while
  resolving, we got a circular dependency. That might happen when we have
  that struct without pointer inside itself.

*/

enum Ast_Decl_State{
  DECL_NOT_RESOLVED,
  DECL_RESOLVED,
  DECL_RESOLVING,
};

struct Ast_Decl;
struct Ast_Scope: Ast{
  Array<Ast_Decl *> decls;
  Array<Ast      *> stmts;
};

struct Ast_Decl: Ast{
  Ast_Decl_State state;
  // Kind: AST_STRUCT implied AST_DECL (should flag AST_CONST AST_DECL)
  Intern_String name;

  Ast_Scope *scope;
  Ast_Expr *typespec;
  union{
    Ast_Expr *expr;
    Ast_Lambda *lambda;
  };

  INLINE_VALUE_FIELDS;
};

struct Ast_File{
  String filename;
  String filecontent;

  Intern_String name;
  Array<Ast_Decl *> decls;
};

struct Ast_Package : Ast_Scope{
  Intern_String name;
};

//-----------------------------------------------------------------------------
// AST Constructors beginning with expressions
//-----------------------------------------------------------------------------
#define AST_NEW(T,ikind,ipos,iflags)                                   \
  Ast_##T *result = exp_alloc_type(pctx->perm, Ast_##T, AF_ZeroMemory);\
  result->flags   = iflags;                                            \
  result->kind    = AST_##ikind;                                       \
  result->parent_scope = pctx->currently_parsed_scope;                 \
  result->pos     = ipos;                                              \
  result->id      = ++pctx->unique_ids

function Ast_Atom *
ast_str(Token *pos, Intern_String string){
  AST_NEW(Atom, VALUE, pos, AST_EXPR | AST_ATOM);
  result->type = untyped_string;
  result->intern_val = string;
  return result;
}

function Ast_Atom *
ast_ident(Token *pos, Intern_String string){
  AST_NEW(Atom, IDENT, pos, AST_EXPR | AST_ATOM);
  result->intern_val = string;
  return result;
}

function Ast_Atom *
ast_bool(Token *pos, B32 bool_val){
  AST_NEW(Atom, VALUE, pos, AST_EXPR | AST_ATOM);
  result->bool_val = bool_val;
  result->type     = untyped_bool;
  return result;
}

function Ast_Atom *
ast_float(Token *pos, F64 value){
  AST_NEW(Atom, VALUE, pos, AST_EXPR | AST_ATOM);
  result->type = untyped_float;
  result->f64_val = value;
  return result;
}

function Ast_Atom *
ast_int(Token *pos, BigInt val){
  AST_NEW(Atom, VALUE, pos, AST_EXPR | AST_ATOM);
  result->type = untyped_int;
  result->big_int_val = bigint_copy(pctx->perm, &val);
  return result;
}

function Ast_Atom *
ast_int(Token *pos, U64 value){
  return ast_int(pos, bigint_u64(value));
}

function Ast_Expr *
ast_expr_binary(Ast_Expr *left, Ast_Expr *right, Token *op){
  AST_NEW(Binary, BINARY, op, AST_EXPR);
  result->op    = op->kind;
  result->left  = left;
  result->right = right;
  return result;
}

function Ast_Call *
ast_call(Token *pos, Ast_Expr *name, Array<Ast_Call_Item *> exprs){
  AST_NEW(Call, CALL, pos, AST_EXPR);
  result->name = name;
  result->exprs = exprs.tight_copy(pctx->perm);
  return result;
}

function Ast_Call_Item *
ast_call_item(Token *pos, Ast_Atom *name, Ast_Expr *item){
  AST_NEW(Call_Item, CALL_ITEM, pos, AST_EXPR);
  result->name  = name;
  result->item  = item;
  return result;
}

function Ast_Expr *
ast_expr_cast(Token *pos, Ast_Expr *expr, Ast_Expr *typespec){
  AST_NEW(Cast, CAST, pos, AST_EXPR);
  result->flags = AST_EXPR;
  result->expr     = expr;
  result->typespec = typespec;
  return result;
}

function Ast_Expr *
ast_expr_unary(Token *pos, Token_Kind op, Ast_Expr *expr){
  AST_NEW(Unary, UNARY, pos, AST_EXPR);
  result->flags = AST_EXPR;
  result->expr = expr;
  result->op   = op;
  return result;
}

function Ast_Expr *
ast_expr_index(Token *pos, Ast_Expr *expr, Ast_Expr *index){
  AST_NEW(Index, INDEX, pos, AST_EXPR);
  result->flags = AST_EXPR;
  result->expr = expr;
  result->index = index;
  return result;
}

function Ast_Lambda *
ast_lambda(Token *pos, Array<Ast_Decl *> params, B32 has_var_args, Ast_Expr *ret, Ast_Scope *scope){
  AST_NEW(Lambda, LAMBDA_EXPR, pos, AST_EXPR);
  result->flags = AST_EXPR;
  result->args  = params.tight_copy(pctx->perm);
  result->scope = scope;
  result->ret   = ret;
  result->has_var_args = has_var_args;
  if(!ret) result->ret = ast_ident(result->pos, intern_void);

  return result;
}

function Ast_If *
ast_if(Token *pos, Array<Ast_If_Node *> ifs){
  AST_NEW(If, IF, pos, AST_STMT);
  result->ifs = ifs.tight_copy(pctx->perm);
  return result;
}

function Ast_For *
ast_for(Token *pos, Ast_Expr *init, Ast_Expr *cond, Ast_Expr *iter, Ast_Scope *scope){
  AST_NEW(For, FOR, pos, AST_STMT);
  result->init = init;
  result->cond = cond;
  result->iter = iter;
  result->scope = scope;
  return result;
}

function Ast_Pass *
ast_pass(Token *pos){
  AST_NEW(Pass, PASS, pos, AST_STMT);
  return result;
}

function Ast_Return *
ast_return(Token *pos, Ast_Expr *expr){
  AST_NEW(Return, RETURN, pos, AST_STMT);
  if(expr){
    assert(is_flag_set(expr->flags, AST_EXPR));
    result->expr = expr;
  }
  return result;
}

function Ast_If_Node *
ast_if_node(Token *pos, Ast_Expr *init, Ast_Expr *expr, Ast_Scope *scope){
  AST_NEW(If_Node, IF_NODE, pos, AST_STMT);
  result->scope    = scope;
  result->expr     = expr;
  result->init     = (Ast_Binary *)init;
  if(result->init) {
    assert(init->kind == AST_VAR);
  }
  return result;
}

function Ast_Array *
ast_array(Token *pos, Ast_Expr *expr){
  AST_NEW(Array, ARRAY, pos, AST_EXPR);
  result->expr = expr;
  return result;
}

function Ast_Scope *
begin_decl_scope(Allocator *scratch, Token *pos){
  AST_NEW(Scope, SCOPE, pos, AST_DECL);
  result->decls = {scratch};
  pctx->currently_parsed_scope = result;
  return result;
}

function void
finalize_decl_scope(Ast_Scope *scope){
  scope->decls = scope->decls.tight_copy(pctx->perm);
  pctx->currently_parsed_scope = scope->parent_scope;
}

function Ast_Scope *
begin_stmt_scope(Allocator *scratch, Token *pos){
  AST_NEW(Scope, SCOPE, pos, AST_STMT);
  result->stmts = {scratch};
  result->decls = {pctx->heap};
  pctx->currently_parsed_scope = result;
  return result;
}

function void
finalize_stmt_scope(Ast_Scope *scope){
  scope->stmts = scope->stmts.tight_copy(pctx->perm);
  pctx->currently_parsed_scope = scope->parent_scope;
}

function Ast_Decl *
ast_struct(Token *pos, Ast_Scope *scope){
  AST_NEW(Decl, STRUCT, pos, AST_DECL | AST_AGGREGATE);
  result->scope = scope;
  return result;
}

function Ast_Decl *
ast_enum(Token *pos, Ast_Expr *typespec, Ast_Scope *scope){
  AST_NEW(Decl, ENUM, pos, AST_DECL | AST_AGGREGATE);
  result->scope = scope;
  result->typespec = typespec;
  return result;
}

function Ast_Decl *
ast_var(Token *pos, Ast_Expr *typespec, Intern_String name, Ast_Expr *expr){
  AST_NEW(Decl, VAR, pos, AST_DECL);
  result->name = name;
  result->typespec = typespec;
  result->expr     = expr;
  return result;
}

function Ast_Decl *
ast_const(Token *pos, Intern_String name, Value value){
  AST_NEW(Decl, CONST, pos, AST_DECL);
  result->value = value;
  result->name = name;
  return result;
}

function Ast_Decl *
ast_const(Token *pos, Intern_String name, Ast_Expr *expr){
  AST_NEW(Decl, CONST, pos, AST_DECL);
  result->expr = expr;
  result->name = name;
  return result;
}

function Ast_Decl *
ast_type(Token *pos, Intern_String name, Ast_Resolved_Type *type){
  AST_NEW(Decl, TYPE, pos, AST_DECL);
  result->type = type_type;
  result->type_val = type;
  result->name = name;
  return result;
}

function Ast_Package *
ast_package(Token *pos, Allocator *allocator, Intern_String name){
  AST_NEW(Package, PACKAGE, pos, 0);
  result->kind = AST_PACKAGE;
  result->decls = {allocator};
  result->name = name;
  return result;
}

//-----------------------------------------------------------------------------
// Value
//-----------------------------------------------------------------------------
function Value
value_bool(B32 v){
  Value value;
  value.bool_val = v;
  value.type = untyped_bool;
  return value;
}

function Value
value_int(BigInt b){
  Value value;
  value.big_int_val = b;
  value.type = untyped_int;
  return value;
}

function Value
value_int(S64 s64){
  Value value;
  value.type = untyped_int;
  bigint_init_signed(&value.big_int_val, s64);
  return value;
}

function Value
value_float(F64 b){
  Value value;
  value.f64_val = b;
  value.type = untyped_float;
  return value;
}

function Value
value_float(BigInt a){
  Value value;
  value.f64_val = bigint_as_float(&a);
  value.type = untyped_float;
  return value;
}

function B32
is_ident(Ast *ast){
  B32 result = ast->kind == AST_IDENT;
  return result;
}

function B32
is_binary(Ast *ast){
  B32 result = ast->kind == AST_BINARY;
  return result;
}

function B32
is_atom(Ast *ast){
  B32 result = is_flag_set(ast->flags, AST_ATOM);
  return result;
}