#define gen(...) pctx->gen.addf(__VA_ARGS__)
#define genln(...) do{gen("\n"); gen_indent(); gen(__VA_ARGS__); }while(0)
global S32 global_indent;
global S32 is_inside_struct;

function void gen_ast(Ast *ast);
function bool gen_expr(Ast_Expr *ast, Ast_Type *type_of_var = 0);

function void
gen_indent(){
  for(S32 i = 0; i < global_indent; i++) gen("  ");
}

global Intern_String last_filename;
global int last_line;
function void
gen_line(Ast *node){
  if(emit_line_directives){
    last_line = node->pos->line+1;
    genln("#line %d", last_line);
    if(node->pos->file != last_filename){
      last_filename = node->pos->file;
      gen(" \"%Q\"", last_filename);
    }
  }
}

function void
gen_last_line(){
  if(emit_line_directives){
    genln("#line %d", last_line);
  }
}

function String
string_scope_name(Allocator *a, Ast_Scope *scope){
  String string = {};
  if(scope->parent_scope) string = string_scope_name(a, scope->parent_scope);
  assert_msg(scope->scope_id != 0, "Scope id is equal to 0 which is invalid, scope didn't initialize id");
  string = string_fmt(a, "%QS%u_", string, scope->scope_id);
  return string;
}

function void
gen_scope_name(Ast_Scope *scope){
  Scratch scratch;
  String string = string_scope_name(scratch, scope);
  gen("%.*s", (int)string.len, string.str);
}

function String
unique_name(Allocator *allocator, Ast *ast){
  Scratch scratch;
  String result = string_scope_name(scratch, ast->parent_scope);
  assert(result.len);
  result = string_fmt(allocator, "%Q%d", result, ast->pos->line);
  return result;
}

function String
string_simple_decl_prefix(Allocator *a, Ast_Type *ast){
  switch(ast->kind){
    case TYPE_POINTER:{
      String string = string_simple_decl_prefix(a, ast->base);
      string = string_fmt(a, "%Q*", string);
      return string;
    }break;
    case TYPE_LAMBDA: return {}; break;
    case TYPE_ENUM:
    case TYPE_ARRAY: {
      return string_simple_decl_prefix(a, ast->base);
    }break;
    case TYPE_SLICE:{
      String string = string_simple_decl_prefix(a, ast->base);
      string = string_fmt(a, "Slice%llu ", ast->type_id);
      return string;
    }break;
    case TYPE_TUPLE:{
      String string = string_fmt(a, "Tuple%llu ", ast->type_id);
      return string;
    }break;
    case TYPE_STRUCT: {
      auto constant = (Ast_Decl *)ast->ast;
      auto name = constant->name;
      String string = string_fmt(a, "%Q ", name);
      String sc = {};
      return string_fmt(a, "%Q%Q", sc, string);
    }break;
    default: {
      String string = string_fmt(a, "%s ", name(ast));
      return string;
    }
  }
  return {};
}

function String
string_simple_decl_postfix(Allocator *a, Ast_Type *ast){
  switch(ast->kind){
    case TYPE_POINTER:
      return string_simple_decl_postfix(a, ast->base);
      break;
    case TYPE_ARRAY:{
      String result = string_simple_decl_postfix(a, ast->arr.base);
      String string = string_fmt(a, "[%d]%Q", ast->arr.size, result);
      return string;
    }break;
    case TYPE_LAMBDA:break;
    case TYPE_SLICE: case TYPE_ENUM: case TYPE_STRUCT:break;
    default:break;
    // default: return string_from_cstring((char *)name(ast));
  }
  return {};
}

function String
string_simple_decl(Allocator *a, Ast_Type *ast, Intern_String name = {}){
  if(ast->kind == TYPE_LAMBDA) {
    String prefix = string_simple_decl_prefix(a, ast->func.ret);
    String string = string_fmt(a, "%Q(*%Q)(", prefix, name);
    For(ast->func.args){
      String prefix_arg = string_simple_decl_prefix(a, it);
      string = string_fmt(a, "%Q%Q", string, prefix_arg);
      if(&it != ast->func.args.end() - 1)
        string = string_fmt(a, "%Q, ", string);
    }
    string = string_fmt(a, "%Q)", string);
    return string;
  }
  else{
    String string = string_simple_decl_prefix(a, ast);
    if(name.len) {
      string = string_fmt(a, "%Q%Q", string, name);
    }
    String postfix = string_simple_decl_postfix(a, ast);
    string = string_fmt(a, "%Q%Q", string, postfix);
    return string;
  }
}

function void
gen_simple_decl(Ast_Type *ast, Intern_String name = {}){
  Scratch scratch;
  String string = string_simple_decl(scratch, ast, name);
  gen("%.*s", (int)string.len, string.str);
}

function String
gen_string_simple_decl(Allocator *a, Ast_Type *ast, String name){
  Scratch scratch;
  String string = string_simple_decl(scratch, ast, pctx->intern(name));
  String result = string_copy(a, string);
  return result;
}

function String
get_type_postfix(Ast_Type *type){
  switch(type->kind) {
    case TYPE_F32: return "f"_s; break;
    case TYPE_U64: return "ULL"_s; break;
    case TYPE_S64: return "LL"_s;  break;
    case TYPE_F64:case TYPE_S8:case TYPE_S16:
    case TYPE_S32:case TYPE_U8:case TYPE_U16:
    case TYPE_INT:case TYPE_U32:case TYPE_CHAR:
      return ""_s;
      break;
    invalid_default_case;
  }
  assert(!"Unhandled case or error");
  return ""_s;
}

function B32
gen_value(Token *pos, Value a){
  if(is_untyped(a.type)) compiler_error(pos, "Internal compiler error: Untyped got propagated to the codegen stage");

  B32 result = true;
  Ast_Type *type = a.type;
  if(is_enum(a.type)){
    type = a.type->base;
  }

  switch(type->kind){
    CASE_INT: {
      Scratch scratch;
      String postfix = get_type_postfix(type);
      const char *string = bigint_to_error_string(scratch, &a.big_int_val, 10);
      gen("%s%Q", string, postfix);
    }break;
    case TYPE_POINTER:{
      if(a.type == type_pointer_to_char){
        gen("\"%Q\"", a.intern_val);
      }
      else{
        U64 pointer_value = bigint_as_unsigned(&a.big_int_val);
        gen("0x%llx", pointer_value);
      }
    }break;
    case TYPE_STRING:
      gen("(String){(U8 *)\"%Q\", %d}", a.intern_val, a.intern_val.len);
    break;
    CASE_BOOL: {
      a.bool_val ? gen("true"):gen("false");
    }break;
    CASE_FLOAT: {
      String postfix = get_type_postfix(type);
      gen("%f%Q", a.f64_val, postfix);
    }break;
    case TYPE_TYPE: {
      gen("%d", a.type_val->type_id);
    }break;
    default: result = false;
  }
  return result;
}

function void
gen_stmt_scope(Ast_Scope *scope, B32 switch_case_gen_break = 0){
  gen("{");
  global_indent++;
  For(scope->stmts) {
    gen_line(it);
    genln("");
    gen_ast(it);
  }
  if(switch_case_gen_break == 1) genln("break;");
  global_indent--;
  gen_last_line();
  genln("}");
}

enum {
  ALWAYS_EMIT_VALUE = 0,
  DONT_EMIT_VALUE = 1,
};

function void
gen_var(Ast_Decl *decl, B32 emit_value, B32 scope_names){
  if(is_flag_set(decl->flags, AST_FOREIGN)) gen("extern ");
  gen_simple_decl(decl->type, decl->name);
  if(is_flag_set(decl->flags, AST_FOREIGN)) return;

  if(emit_value == DONT_EMIT_VALUE){
    return;
  }

  if(decl->expr){
    gen(" = ");
    gen_expr(decl->expr, decl->type);
  } else { // Default zero
    if(is_numeric(decl->type)){
      gen(" = 0");
    } else {
      gen(" = {}");
    }
  }
}

function void
gen_lambda(Intern_String name, Ast_Lambda *lambda, B32 generate_block = true){
  gen_simple_decl(lambda->resolved_type->func.ret, name);
  gen("(");
  For(lambda->args){
    gen_var(it, DONT_EMIT_VALUE, true);
    if(&it != (lambda->args.end() - 1))
      gen(", ");
  }
  gen(")");

  if(generate_block && lambda->scope){
    gen_stmt_scope(lambda->scope);
  }
  else gen(";");
}

function bool
gen_expr(Ast_Expr *ast, Ast_Type *type_of_var){
  switch(ast->kind){
    CASE(IDENT, Atom){
      if(node->resolved_decl->kind == AST_MODULE_NAMESPACE || node->resolved_decl->kind == AST_FILE_NAMESPACE)
        return false;

      if(type_of_var && is_slice(type_of_var) && is_array(node->resolved_decl->type)){
        gen("{%d, ", (int)node->resolved_decl->type->arr.size);
        gen("%Q}", node->intern_val);
      }

      else if(type_of_var && !is_any(ast->resolved_type) && is_any(type_of_var)){
        gen("(Any){&");
        gen_expr(ast);
        gen(", %d}", ast->resolved_type->type_id);
      }

      else if(node->resolved_decl->kind == AST_LAMBDA){
        gen("%Q", node->resolved_decl->unique_name);
      }

      else {
        gen("%Q", node->intern_val);
      }


      BREAK();
    }

    CASE(VALUE, Atom){
      if(is_any(type_of_var)){
        gen("(Any){&");
        gen("("); gen_simple_decl(node->type); gen("){"); gen_value(node->pos, node->value); gen("}");
        gen(", %d}", node->type->type_id);
        return true;
      }

      B32 written = gen_value(node->pos, node->value);
      if(!written) {
        gen("%Q", node->value.intern_val);
      }
      BREAK();
    }

    CASE(ARRAY, Array){
      gen("%d", node->resolved_type->type_id);
      BREAK();
    }

    CASE(INDEX, Index){
      gen("(");
      gen_expr(node->expr);
      if(node->index_original_type == type_string){
        gen(".str");
      }
      else if(is_slice(node->index_original_type)){
        gen(".data");
      }
      gen("[");
      gen_expr(node->index);
      gen("]");
      gen(")");
      BREAK();
    }

    CASE(LAMBDA_EXPR, Lambda){
      gen_lambda({}, node);
      BREAK();
    }

    CASE(BINARY, Binary){
      if(node->op == TK_Dot){
        if(gen_expr(node->left)){
          if(node->dot_access_step_resolution && node->dot_access_step_resolution->kind == TYPE_POINTER) gen("->");
          else gen(".");
        }
        gen_expr(node->right);
        return true;
      }
      else if(node->op == TK_Arrow){
        gen("(");
        gen("(");
        gen_simple_decl(node->resolved_type);
        gen(")");
        gen_expr(node->left);
        gen(")");
        return true;
      }

      if(!token_is_assign(node->op)) gen("(");
      gen_expr(node->left);
      gen("%s", name(node->op));
      gen_expr(node->right);
      if(!token_is_assign(node->op)) gen(")");

      BREAK();
    }

    CASE(UNARY, Unary){
      gen("(");
      if(node->op != TK_PostIncrement && node->op != TK_PostDecrement) gen("%s", name(node->op));
      gen_expr(node->expr);
    if(node->op == TK_PostIncrement || node->op == TK_PostDecrement) gen("%s", name(node->op));
      gen(")");
      BREAK();
    }

    CASE(VAR, Decl){
      gen_ast(node);
      BREAK();
    }

    CASE(LENGTH_OF, Call){
      Ast_Expr *expr = unpack_ast_call_expr_for_builtin(node);
      gen_expr(expr);
      if(is_pointer(expr->resolved_type))
        gen("->len");
      else gen(".len");
      BREAK();
    }

    CASE(CALL, Call){
      gen("%Q(", node->resolved_decl->unique_name);
      For(node->exprs){
        gen_expr(it->item, it->resolved_type);
        if(!node->exprs.is_last(&it)) gen(", ");
      }
      gen(")");
      BREAK();
    }

    CASE(COMPOUND, Call){
      gen("(");
      gen_simple_decl(node->resolved_type);
      gen(")");
      gen("{");

      if(is_slice(node->resolved_type)) {
        gen(".len = %d, ", node->exprs.len);
        gen(".data = (");
        gen_simple_decl(node->resolved_type->base);
        gen("[]");
        gen(")");
        gen("{");
      }

      For(node->exprs){
        if(is_struct(node->resolved_type))
          gen(".%Q = ", it->resolved_name);
        else if(is_array(node->resolved_type))
          gen("[%d] = ", (int)it->resolved_index);
        gen_expr(it->item, it->resolved_type);

        if(!node->exprs.is_last(&it)) gen(", ");
      }

      if(is_slice(node->resolved_type)) gen("}");
      gen("}");
      BREAK();
    }

    invalid_default_case;
  }
  return true;
}

function void
gen_ast(Ast *ast){
  switch(ast->kind){

    CASE(RUNTIME_ASSERT, Builtin){
      if(node->assert_message.len == 0) gen("assert");
      else                              gen("assert_msg");
      gen("(");
      gen_expr(node->expr);
      if(node->assert_message.len){
        gen(", \"%Q\"", node->assert_message);
      }
      gen(");");
      BREAK();
    }

    CASE(RETURN, Return){
      if(is_tuple(node->resolved_type)) {
        Scratch scratch;
        Intern_String var_name = pctx->intern(unique_name(scratch, node));
        gen_simple_decl(node->resolved_type, var_name);
        gen(";");

        int i = 0;
        For(node->expr){
          genln("memcpy(&%Q.m%d, ", var_name, i);
          if(!is_array(it->resolved_type)) gen("&");
          gen("(");
          gen_expr(it);
          gen(")");
          gen(", sizeof(%Q.m%d));", var_name, i++);
        }

        genln("return %Q;", var_name);
        return;
      }

      assert(node->expr.len <= 1);
      gen("return ");
      For(node->expr) gen_expr(it);
      gen(";");
      BREAK();
    }

    CASE(VAR, Decl){
      gen_var(node, is_inside_struct ? DONT_EMIT_VALUE : ALWAYS_EMIT_VALUE, true);
      if(!is_flag_set(ast->flags, AST_EXPR)) gen(";");
      BREAK();
    }

    CASE(IF, If){
      For(node->ifs){
        gen_line(node);
        genln("");
        if(it->init) {
          gen_expr(it->init);
          gen(";");
          genln("");
        }
        if(node->ifs.is_first(&it)){
          gen("if(");
          gen_expr(it->expr);
          gen(")");
          gen_stmt_scope(it->scope);
        }
        else{
          genln("else");
          if(it->expr){
            gen(" if(");
            gen_expr(it->expr);
            gen(")");
          }
          gen_stmt_scope(it->scope);
        }
      }
      BREAK();
    }


    CASE(BREAK, Break){
      unused(node);
      gen("break;");
      BREAK();
    }


    CASE(PASS, Pass){
      unused(node);
      gen("//pass");
      BREAK();
    }

    CASE(BINARY,Binary){
      gen_expr(node);
      gen(";");
      BREAK();
    }

    CASE(FOR, For){

      // Array iter
      if(node->is_array_traversal){
        gen("for(S64 _i%d = 0; _i%d < ", node->pos->line, node->pos->line);
        if(is_array(node->cond->resolved_type)){
          gen("_buff_cap(");
          gen_expr(node->cond);
          gen(")");
        } else{
          assert(is_slice(node->cond->resolved_type));
          gen_expr(node->cond);
          gen(".len");
        }


        gen("; _i%d+=1)", node->pos->line);
        gen("{");
        global_indent++;
        genln("");
        gen_simple_decl(node->array_traversal_var->type, node->array_traversal_var->name);
        gen(" = ");
        gen_expr(node->cond);
        if(node->is_also_slice_traversal) gen(".data");
        gen(" + _i%d;", node->pos->line);
        For(node->scope->stmts) {
          gen_line(it);
          genln("");
          gen_ast(it);
        }
        global_indent--;
        gen_last_line();
        genln("}");
      }

      // Normal for loop
      else{
        gen("for(");
        if(node->init) gen_expr(node->init);
        gen(";");
        if(node->cond) gen_expr(node->cond);
        gen(";");
        if(node->iter) gen_expr(node->iter);
        gen(")");
        gen_stmt_scope(node->scope);
      }

      BREAK();
    }

    CASE(LAMBDA, Decl){
      gen_line(node);
      genln("");

      if(is_flag_set(node->expr->flags, AST_FOREIGN)){
        gen("/*foreign*/");
      }
      gen_lambda(node->unique_name, node->lambda);
      BREAK();
    }

    CASE(STRUCT, Decl){
      gen("struct ");
      gen("%Q{", node->name);
      global_indent++;
      is_inside_struct++;
      For(node->scope->decls){
        genln("");
        gen_ast(it);
      }

      is_inside_struct--;
      global_indent--;
      genln("};");
      BREAK();
    }

    CASE(TYPE, Decl){
      gen("// Type %Q = ", node->name);
      gen_simple_decl(node->type_val);
      BREAK();
    }

    CASE(ENUM, Decl){
      gen("/*enum %Q{", node->name);
      // @todo add typespec
      global_indent++;
      For(node->scope->decls){
        genln("%Q", it->name);
        gen(" = ");
        gen_value(it->pos, it->value);
        gen(",");
      }
      global_indent--;
      genln("};*/");
      BREAK();
    }

    CASE(CONST, Decl){
      switch(node->type->kind){
        CASE_FLOAT:{
          gen("// F64 %Q = ", node->name);
          // gen_value(node->pos, node->value);
        } break;
        CASE_INT:{
          gen("// constant int %Q = ", node->name);
          // gen_value(node->pos, node->value);
        }break;
        CASE_STRING:{
          assert(is_pointer(node->type) ? node->type == type_pointer_to_char : 1);
          gen("// const String %Q = ", node->name);
          // gen_value(node->pos, node->value);
        }break;
        CASE_BOOL:{
          gen("// const Bool %Q = ", node->name);
          // gen_value(node->pos, node->value);
        }break;
        case TYPE_LAMBDA:{
          gen("// ");
          gen_lambda(node->unique_name, node->lambda);
        } break;
        invalid_default_case;
      }

      BREAK();
    }

    CASE(SWITCH, Switch){
      gen("switch(");
      gen_expr(node->value);
      gen("){");
      global_indent++;

      For(node->cases){
        For_Named(it->labels, label){
          gen_line(it);
          genln("");
          gen("case ");
          gen_expr(label);
          gen(":");
        }

        gen_stmt_scope(it->scope, it->fallthrough ? false : true);
      }

      if(node->default_scope){
        genln("default: ");
        gen_stmt_scope(node->default_scope);
      }

      global_indent--;
      gen_last_line();
      genln("}");

      BREAK();
    }

    CASE(VAR_UNPACK, Var_Unpack){
      For(node->vars)
        gen_ast(it);

      Scratch scratch;
      Intern_String var_name = pctx->intern(unique_name(scratch, node));
      gen_simple_decl(node->resolved_type, var_name);
      gen(" = ");
      gen_expr(node->expr);
      gen(";");

      int i = 0;
      For(node->vars){
        gen("memcpy((void *)&%Q, (void *)&%Q.m%d, sizeof(%Q));", it->name, var_name, i++, it->name);
      }
      BREAK();
    }

    case AST_CONSTANT_ASSERT:
    case AST_MODULE_NAMESPACE:
    CASE(FILE_NAMESPACE, File_Namespace){unused(node); BREAK();}

    default: {
      assert(is_flag_set(ast->flags, AST_EXPR));
      gen_expr((Ast_Expr *)ast);
      gen(";");
    }
  }
}

function String
compile_to_c_code(){
  generating_time_begin = os_time();

  gen(R"==(
#include <stdint.h>
#include <math.h>
#include <string.h>
typedef int8_t   S8;
typedef int16_t  S16;
typedef int32_t  S32;
typedef int64_t  S64;
typedef uint8_t  U8;
typedef uint16_t U16;
typedef uint32_t U32;
typedef uint64_t U64;
typedef S8       B8;
typedef S16      B16;
typedef S32      B32;
typedef S64      B64;
typedef U64      SizeU;
typedef S64      SizeS;
typedef float    F32;
typedef double   F64;
typedef S32      Bool;
typedef S64      Type;
#define true 1
#define false 0
#define assert(x) do{if(!(x))__debugbreak();}while(0)
#define assert_msg(x,...) assert(x)
#define _buff_cap(x) (sizeof(x)/sizeof((x)[0]))
typedef struct String{
  U8 *str;
  S64 len;
}String;
)==");

  // Generate struct forward decls
  For(pctx->ordered_decls){
    if(it->kind == AST_STRUCT){
      genln("typedef struct %Q %Q;", it->name, it->name);
    }
  }

  // Generate slice and tuple types
  For(pctx->all_types){
    Scratch scratch;
    Ast_Type *type = it;

    if(type->kind == TYPE_SLICE){
      genln("typedef struct Slice%llu{", type->type_id);
      global_indent++;
        genln("S64 len;");
        genln("");
        gen_simple_decl(type_pointer(type->base), pctx->intern("data"_s));
        gen(";");
      global_indent--;
      genln("} Slice%llu;", type->type_id);
    }

    else if(type->kind == TYPE_TUPLE){
      genln("typedef struct Tuple%llu{", type->type_id);
      global_indent++;
      For(type->agg.members){
        genln("");
        // @todo remove intern from gen
        Intern_String name = pctx->intern(string_fmt(scratch, "m%llu", type->agg.members.get_index(&it)));
        gen_simple_decl(it.type, name);
        gen(";");
      }
      global_indent--;
      genln("} Tuple%llu;", type->type_id);
    }
  }

  Intern_String intern_main = pctx->intern("main"_s);
  Intern_String intern_win_main = pctx->intern("WinMain"_s);

  Ast_Decl *main = 0;
  Ast_Decl *win_main = 0;

  // Generate lambda forward decls
  For(pctx->ordered_decls){
    if(it->kind == AST_LAMBDA){
      if(it->name == intern_main){
        main = it;
        it->unique_name = it->name;
      }

      if(it->name == intern_win_main){
        win_main = it;
        it->unique_name = it->name;
      }

      genln("");
      gen_lambda(it->unique_name, it->lambda, false);
    }
  }

  if(!main && !win_main){
    compiler_error(0, "Entry point is not defined! Try main or WinMain");
  }

  // Generate language.kl
  for(S32 i = 0; i < pctx->base_language_ordered_decl_len; i++){
    Ast_Decl *it = pctx->ordered_decls[i];
    genln("");
    gen_ast(it);
  }

  // Generate type info
  genln("S64 type_infos_len = %d;", pctx->all_types.len);
  genln("Type_Info *type_infos = (Type_Info[]){");
  global_indent++;
  For(pctx->all_types){
    genln("{/*%Q*/.kind = %d, .size = %d, .align = %d, .is_unsigned = %s, .type = %d, ", typestring(it),
      (S32)it->kind, (S32)it->size, (S32)it->align, it->is_unsigned ? "true" : "false", it->type_id);
    switch(it->kind){
      case TYPE_POINTER:
      case TYPE_SLICE: {
        gen(".base_type = %d", it->base->type_id);
      } break;
      case TYPE_ARRAY: {
        gen(".base_type = %d, ", it->base->type_id);
        gen(".array_size = %d", it->arr.size);
      }break;
      case TYPE_LAMBDA: {
        gen(".lambda_return = %d, ", it->func.ret->type_id);
        gen(".lambda_argument_count = %d, ", it->func.args.len);
        gen(".lambda_arguments = (Type_Info[%d]){", it->func.args.len);
        For_Named(it->func.args, arg){
          gen("{.type = %d}, ", arg->type_id);
        }
        gen("}");
      } break;
      case TYPE_STRUCT:{
        gen(".struct_member_count = %d, ", it->agg.members.len);
        gen(".struct_members = (Type_Info_Struct_Member[]){");
        For_Named(it->agg.members, m){
          gen("{.name = (String){(U8 *)\"%Q\", %d}, .type = %d, .offset = %d}, ", m.name, m.name.len, m.type->type_id, m.offset);

        }
        gen("}");
      }break;
      default: {}
      // invalid_default_case;
    }
    gen("},");
  }
  global_indent--;
  gen("};");

  // Generate actual code
  for(S32 i = pctx->base_language_ordered_decl_len; i < pctx->ordered_decls.len; i++){
    Ast_Decl *it = pctx->ordered_decls[i];
    genln("");
    gen_ast(it);
  }

  String string_result = string_flatten(pctx->perm, &pctx->gen);
  generating_time_end = os_time();
  return string_result;
}