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

// @todo: Gen complicated decl
//array 10 ( pointer (pointer array 5 int a))
// int (*(*(a[5])))[10]
//
// 1 Get to the bottom
// 2 Add variable name
// 3 Going backwards add arrays and pointers in parens
// 4 Add type name on the left side

function void
gen_simple_decl_prefix(Ast_Resolved_Type *ast){
  switch(ast->kind){
    case TYPE_POINTER: gen_simple_decl_prefix(ast->base); gen("*"); break;
    case TYPE_ARRAY: gen_simple_decl_prefix(ast->base); break;
    case TYPE_LAMBDA:break;
    case TYPE_ENUM:
    case TYPE_STRUCT: {
      auto constant = (Ast_Decl *)ast->ast;
      auto name = constant->name;
      gen("%s ", name.str);
    }break;
    default: gen("%s ", name(ast));
  }
}

function void
gen_simple_decl_postfix(Ast_Resolved_Type *ast){
  switch(ast->kind){
    case TYPE_POINTER: gen_simple_decl_postfix(ast->base); break;
    case TYPE_ARRAY:
      gen("[");
      if(ast->arr.size != ARRAY_SIZE_INFERRED)
        gen("%d", (int)ast->arr.size);
      gen("]");
      gen_simple_decl_postfix(ast->arr.base); break;
    case TYPE_LAMBDA:break;
    case TYPE_ENUM: case TYPE_STRUCT:break;
    default: name(ast);
  }
}

function void
gen_simple_decl(Ast_Resolved_Type *ast, Intern_String name){
  if(ast->kind == TYPE_LAMBDA) {
    gen_simple_decl_prefix(ast->func.ret);
    gen("(*%s)(", name.str);
    For(ast->func.args){
      gen_simple_decl_prefix(it);
      if(&it != ast->func.args.end() - 1) gen(", ");
    }
    gen(")");
  }
  else{
    gen_simple_decl_prefix(ast);
    if(name.len) {
      gen("%s", name.str);
    }
    gen_simple_decl_postfix(ast);
  }
}

function void
gen_value(Value a){
  switch(a.type->kind){
    CASE_INT: {
      Scratch scratch;
      const char *string = bigint_to_error_string(scratch, &a.big_int_val, 10);
      gen("%s", string);
    }break;
    CASE_STRING: gen("LIT(\"%s\")", a.intern_val.str); break;
    CASE_BOOL: a.bool_val ? gen("true"):gen("false"); break;
    CASE_FLOAT: gen("%f", a.f64_val); break;
    invalid_default_case;
  }
}

function void
gen_expr(Ast_Expr *ast){
  switch(ast->kind){
    CASE(IDENT, Atom){
      gen("%s", node->intern_val.str);
      BREAK();
    }

    CASE(VALUE, Atom){
      gen_value(node->value);
      BREAK();
    }

    // CASE(INDEX, Index){
    //   Sym *sym = resolved_get(node);
    //   if(is_array(sym->type)){
    //     gen("(");
    //     gen("(");

    //     gen("(");
    //     gen_simple_decl(sym->type->arr.base, {});
    //     gen("*)");
    //     gen_expr(node->expr);
    //     gen(".data)");


    //     gen("[");
    //     gen_expr(node->index);
    //     gen("]");
    //     gen(")");
    //   } else{
    //     gen("(");
    //     gen_expr(node->expr);
    //     gen("[");
    //     gen_expr(node->index);
    //     gen("]");
    //     gen(")");
    //   }
    //   BREAK();
    // }

    CASE(BINARY, Binary){
      // if(node->op == TK_Dot){
      //   Sym *sym = resolved_get(node->left);
      //   gen_expr(node->left);
      //   if(sym->type->kind == TYPE_POINTER) gen("->");
      //   else gen(".");
      //   gen_expr(node->right);
      // }
      // else if(node->op == TK_ColonAssign){

      //   Sym *sym = resolved_get(node);
      //   Ast_Atom *atom = (Ast_Atom *)node->left;
      //   assert(is_atom(atom));
      //   gen_simple_decl(sym->type, atom->intern_val);
      //   if(node->right){
      //     gen(" = ");
      //     gen_expr(node->right);
      //   }
      // }
      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(CAST, Cast){
      gen("(");
      gen("(");
      gen_simple_decl(node->after_type, {});
      gen(")");
      gen_expr(node->expr);
      gen(")");
      BREAK();
    }

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

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

    invalid_default_case;
  }
}

function void
gen_line(Ast *node){
  if(emit_line_directives)
    genln("#line %d", node->pos->line+1);
}

function void
gen_stmt_scope(Ast_Scope *scope){
  gen("{");
  global_indent++;
  For(scope->stmts) {
    gen_line(it);
    genln("");
    gen_ast(it);
  }
  global_indent--;
  genln("}");
}

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

function void
gen_var(Intern_String name, Ast_Resolved_Type *type, Ast_Expr *expr, B32 emit_value){
  gen_simple_decl(type, name);

  if(emit_value == DONT_EMIT_VALUE){
    return;
  }

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

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

    CASE(RETURN, Return){
      gen("return");
      if(node->expr){
        gen(" ");
        gen_expr(node->expr);
      }
      gen(";");
      BREAK();
    }

    CASE(VAR, Decl){
      gen_var(node->name, node->type, node->expr, is_inside_struct ? DONT_EMIT_VALUE : ALWAYS_EMIT_VALUE);
      gen(";");
      BREAK();
    }

    CASE(IF, If){
      For(node->ifs){
        if(it->init) gen_expr(it->init);
        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(PASS, Pass){
      unused(node);
      gen("//pass");
      BREAK();
    }

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

    CASE(FOR, For){
      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){
      if(node->kind == AST_LAMBDA){
        if(is_flag_set(node->flags, AST_FOREIGN)){
          return;
        }
        Ast_Lambda *lambda = node->lambda;
        Ast_Resolved_Type *ret = node->type->func.ret;
        gen_simple_decl(ret, node->name);
        gen("(");
        For(lambda->args){
          gen_var(it->name, it->type, 0, DONT_EMIT_VALUE);
          if(&it != (lambda->args.end() - 1)) gen(", ");
        }
        gen(")");

        if(lambda->scope) {
          gen_stmt_scope(lambda->scope);
        }
        else gen(";");
      }
      else{
        gen_simple_decl(node->type, node->name);
        gen(" = ");
        gen_expr((Ast_Expr *)node->expr);
        gen(";");
      }
      BREAK();
    }

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

      is_inside_struct--;
      global_indent--;
      genln("}%s;", node->name.str);
      BREAK();
    }

    CASE(CONST, Decl){
      switch(node->type->kind){
        CASE_FLOAT:{
          gen("// F64 %s = ", node->name.str);
          gen_value(node->value);
        } break;
        CASE_INT:{
          gen("// constant int %s = ", node->name.str);
          gen_value(node->value);
        }break;
        CASE_STRING:{
          gen("// const String %s = ", node->name.str);
          gen_value(node->value);
        }break;
        CASE_BOOL:{
          gen("// const Bool %s = ", node->name.str);
          gen_value(node->value);
        }break;

        case TYPE_LAMBDA:{

        }break;

        case TYPE_TYPE:{
        }break;
        //   if(sym->type_val->kind == TYPE_STRUCT){
        //     Ast_Struct *agg = (Ast_Struct *)sym->type_val->ast;
        //     if(node->value->kind == AST_STRUCT){
        //       gen("typedef struct %s{", node->name.str);
        //       global_indent++;
        //       is_inside_struct++;
        //       For(agg->members){
        //         genln("");
        //         gen_ast(it);
        //       }

        //       For(agg->const_members){
        //         genln("");
        //         gen_ast(it);
        //       }
        //       is_inside_struct--;
        //       global_indent--;
        //       genln("}%s;", node->name.str);
        //     }
        //     else{
        //       // Type alias
        //     }
        //   }
        //   else if(sym->type_val->kind == TYPE_ENUM){
        //     Ast_Enum *enu = (Ast_Enum *)sym->type_val->ast;
        //     assert(enu->kind == AST_ENUM);
        //     if(node->value->kind == AST_ENUM){
        //       gen("/*enum %s{", node->name.str);
        //       // @todo add typespec
        //       global_indent++;
        //       For(enu->members){
        //         genln("%s", it->name.str);
        //         gen(" = ");
        //         Sym *value_sym = resolved_get(it);
        //         gen("%d", bigint_as_signed(&value_sym->big_int_val));
        //         gen(",");
        //       }
        //       global_indent--;
        //       genln("};*/");
        //     }
        //     else{
        //       // Type alias
        //     }
        //   }
        //   else{
        //     gen("// typedef ");
        //     gen_simple_decl(sym->type_val, node->name);
        //     gen(";");
        //   }
        // }break;
        default: compiler_error(node->pos, "C_Codegen: Unhandled type %s of constant expression", docname(node->type));
      }

      BREAK();
    }

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

#if 0
function String
compile_string(String filecontent, String filename = "default_name"_s){
  F64 total_time = os_time();
  Scratch scratch(thread_ctx.scratch);
  OS_Heap heap = win32_os_heap_create(false, mib(4), 0);

  Parse_Ctx ctx = {};
  parse_init(&ctx, scratch, &heap);

  F64 tokenize_begin = os_time();
  lex_restream(&ctx, filecontent, filename);
  F64 tokenize_end = os_time();

  F64 parse_begin = os_time();
  Ast_Package *result = parse_file();
  sym_insert_builtins();
  pctx->resolving_package = result;
  F64 parse_end = os_time();

  gen(R"==(
#include <stdint.h>
#include <stdio.h>
#include <math.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 struct Slice{
  S64 len;
  void *data;
}Slice;

typedef struct String{
  U8 *str;
  S64 len;
}String;
#define LIT(x) (String){.str=(U8 *)x, .len=sizeof(x)-1}

void entry();
int main(){
  entry();
}
  )==");

  F64 resolve_begin = os_time();
  resolve_package(result);
  F64 resolve_end = os_time();

  F64 codegen_begin = os_time();
  gen_ast(result);
  F64 codegen_end = os_time();

  exp_destroy(&heap);

  F64 flattening_begin = os_time();
  String string_result = string_flatten(scratch, &pctx->gen);
  F64 flattening_end = os_time();

  printf("\n//-------------------------------");
  printf("\n// Tokenization: %f", tokenize_end - tokenize_begin);
  printf("\n// Parsing     : %f", parse_end    - parse_begin);
  printf("\n// Resolving   : %f", resolve_end  - resolve_begin);
  printf("\n// Codegen     : %f", codegen_end  - codegen_begin);
  printf("\n// Flattening  : %f", flattening_end - flattening_begin);
  printf("\n// Total       : %f", flattening_end - total_time);
  printf("\n//-------------------------------");

  return string_result;
}

function String
compile_file(String filename){
  Scratch scratch;
  String filecontent = os_read_file(scratch, filename);
  assert(filecontent.len);
  String result = compile_string(filecontent, filename);
  return result;
}
#endif


function String
compile_files(Array<String> filename){
  Scratch scratch(thread_ctx.scratch);
  Array<Ast_File> files = {scratch};

  For(filename){
    String filecontent = os_read_file(scratch, it);
    assert(filecontent.len);
    files.add(ast_file(it, filecontent));
  }

  F64 total_time = os_time();
  OS_Heap heap = win32_os_heap_create(false, mib(16), 0);

  Parse_Ctx ctx = {};
  parse_init(&ctx, scratch, &heap);

  F64 parse_begin = os_time();
  Array<Ast_Package> packages = {&heap};
  For(files){
    parse_file(&it);

    Ast_Package *package = find_package(it.name, &packages);
    if(package){
      package->decls.add(it.decls);
    } else {
      Ast_Package p = ast_package(&heap, it.name, it.decls);
      insert_builtin_types_into_package(&p);
      packages.add(p);
    }

  }
  F64 parse_end = os_time();

  For(packages){
    resolve_package(&it);
  }

  For(pctx->ordered_decls){
    genln("");
    gen_ast(it);
  }

  exp_destroy(&heap);


  F64 flattening_begin = os_time();
  String string_result = string_flatten(scratch, &pctx->gen);
  F64 flattening_end = os_time();

  printf("\n//-------------------------------");
  printf("\n// Parse       : %f", parse_end      - parse_begin);
  printf("\n// Flattening  : %f", flattening_end - flattening_begin);
  printf("\n// Total       : %f", flattening_end - total_time);
  printf("\n//-------------------------------");

  return string_result;
}