internal COFF_ObjWriter*
coff_obj_writer_alloc(COFF_TimeStamp time_stamp, COFF_MachineType machine_type)
{
  Arena *arena = arena_alloc();
  COFF_ObjWriter *obj_writer = push_array(arena, COFF_ObjWriter, 1);
  obj_writer->arena          = arena;
  obj_writer->time_stamp     = time_stamp;
  obj_writer->machine_type   = machine_type;
  return obj_writer;
}

internal void
coff_obj_writer_release(COFF_ObjWriter **obj_writer)
{
  arena_release((*obj_writer)->arena);
  *obj_writer = 0;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol(COFF_ObjWriter *obj_writer, String8 name, U32 value, COFF_SymbolLocation loc, COFF_SymbolType type, COFF_SymStorageClass storage_class)
{
  COFF_ObjSymbolNode *n = push_array(obj_writer->arena, COFF_ObjSymbolNode, 1);
  SLLQueuePush(obj_writer->symbol_first, obj_writer->symbol_last, n);
  obj_writer->symbol_count += 1;

  COFF_ObjSymbol *s = &n->v;
  s->name           = name;
  s->value          = value;
  s->loc            = loc;
  s->type           = type;
  s->storage_class  = storage_class;
  s->idx            = obj_writer->symbol_count-1;

  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_external(COFF_ObjWriter *obj_writer, String8 name, U32 value, COFF_ObjSection *section)
{
  COFF_SymbolLocation loc = {0};
  loc.type                = COFF_SymbolLocation_Section;
  loc.u.section           = section;
  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, value, loc, (COFF_SymbolType){0}, COFF_SymStorageClass_External);
  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_static(COFF_ObjWriter *obj_writer, String8 name, U32 off, COFF_ObjSection *section)
{
  COFF_SymbolLocation loc = {0};
  loc.type = COFF_SymbolLocation_Section;
  loc.u.section = section;
  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, off, loc, (COFF_SymbolType){0}, COFF_SymStorageClass_Static);
  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_abs(COFF_ObjWriter *obj_writer, String8 name, U32 value, COFF_SymStorageClass storage_class)
{
  COFF_SymbolLocation loc = {0};
  loc.type = COFF_SymbolLocation_Abs;
  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, value, loc, (COFF_SymbolType){0}, storage_class);
  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_undef(COFF_ObjWriter *obj_writer, String8 name)
{
  COFF_SymbolType type = {0};
  COFF_SymbolLocation loc = {0};
  loc.type = COFF_SymbolLocation_Undef;
  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, 0, loc, type, COFF_SymStorageClass_External);
  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_undef_func(COFF_ObjWriter *obj_writer, String8 name)
{
  COFF_SymbolType type = {0};
  type.u.msb = COFF_SymDType_Func;
  COFF_SymbolLocation loc = {0};
  loc.type = COFF_SymbolLocation_Undef;
  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, 0, loc, type, COFF_SymStorageClass_External);
  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_undef_sect(COFF_ObjWriter *obj_writer, String8 name, U32 value)
{
  COFF_SymbolType type = {0};
  COFF_SymbolLocation loc = {0};
  loc.type = COFF_SymbolLocation_Undef;
  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, value, loc, type, COFF_SymStorageClass_Section);
  return s;
}

internal COFF_ObjSymbol *
coff_obj_writer_push_symbol_sect(COFF_ObjWriter *obj_writer, String8 name, COFF_ObjSection *sect)
{
  COFF_SymbolType type = {0};
  COFF_SymbolLocation loc = {0};
  loc.type      = COFF_SymbolLocation_Section;
  loc.u.section = sect;

  // strip align flags
  COFF_SectionFlags expected_flags = sect->flags & ~(COFF_SectionFlag_AlignMask << COFF_SectionFlag_AlignShift); 

  COFF_ObjSymbol *s = coff_obj_writer_push_symbol(obj_writer, name, expected_flags, loc, type, COFF_SymStorageClass_Section);
  return s;
}

internal COFF_ObjSection *
coff_obj_writer_push_section(COFF_ObjWriter *obj_writer, String8 name, COFF_SectionFlags flags, String8 data)
{
  COFF_ObjSectionNode *sect_n = push_array(obj_writer->arena, COFF_ObjSectionNode, 1);
  SLLQueuePush(obj_writer->sect_first, obj_writer->sect_last, sect_n);
  obj_writer->sect_count += 1;

  COFF_ObjSection *sect = &sect_n->v;
  sect->name            = name;
  sect->flags           = flags;

  str8_list_push(obj_writer->arena, &sect->data, data);

  return sect;
}

internal COFF_ObjReloc*
coff_obj_writer_section_push_reloc(COFF_ObjWriter *obj_writer, COFF_ObjSection *sect, U32 apply_off, COFF_ObjSymbol *symbol, COFF_RelocType type)
{
  COFF_ObjRelocNode *reloc_n = push_array(obj_writer->arena, COFF_ObjRelocNode, 1);
  SLLQueuePush(sect->reloc_first, sect->reloc_last, reloc_n);
  sect->reloc_count += 1;

  COFF_ObjReloc *reloc = &reloc_n->v;
  reloc->apply_off     = apply_off;
  reloc->symbol        = symbol;
  reloc->type          = type;

  return reloc;
}

internal int
coff_obj_section_is_before(void *raw_a, void *raw_b)
{
  COFF_ObjSection **a = raw_a;
  COFF_ObjSection **b = raw_b;
  return (*a)->section_number < (*b)->section_number;
}

internal String8
coff_obj_writer_serialize(Arena *arena, COFF_ObjWriter *obj_writer)
{
  Temp scratch = scratch_begin(&arena, 1);

  String8List srl = {0};

  String8List string_table = {0};
  U32 *string_table_size = push_array(scratch.arena, U32, 1);
  *string_table_size = sizeof(*string_table_size);
  str8_list_push(scratch.arena, &string_table, str8_struct(string_table_size));

  //
  // 
  //
  U64               obj_sections_count;
  COFF_ObjSection **obj_sections;
  {
    obj_sections_count = obj_writer->sect_count;
    obj_sections       = push_array(scratch.arena, COFF_ObjSection *, obj_writer->sect_count);
    U64 sect_idx = 0;
    for (COFF_ObjSectionNode *sect_n = obj_writer->sect_first; sect_n != 0; sect_n = sect_n->next, sect_idx += 1) {
      COFF_ObjSection *sect = &sect_n->v;
      sect->section_number = sect_idx+1;
      obj_sections[sect_idx] = sect;

    }
  }
  AssertAlways(obj_sections_count <= max_U16);

  //
  // file header
  //
  COFF_FileHeader *file_header      = push_array(scratch.arena, COFF_FileHeader, 1);
  file_header->machine              = obj_writer->machine_type;
  file_header->section_count        = obj_sections_count;
  file_header->time_stamp           = obj_writer->time_stamp;
  file_header->symbol_table_foff    = 0;
  file_header->symbol_count         = safe_cast_u32(obj_writer->symbol_count);
  file_header->optional_header_size = 0;
  file_header->flags                = 0;
  str8_list_push(scratch.arena, &srl, str8_struct(file_header));

  //
  // section table
  //

  COFF_SectionHeader *sectab = push_array(scratch.arena, COFF_SectionHeader, obj_sections_count);
  str8_list_push(scratch.arena, &srl, str8_array(sectab, obj_sections_count));
  {
    for (U64 sect_idx = 0; sect_idx < obj_sections_count; sect_idx += 1) {
      COFF_ObjSection    *s = obj_sections[sect_idx];
      COFF_SectionHeader *d = &sectab[sect_idx];

      // section name
      String8 sect_name = s->name;
      if (sect_name.size > sizeof(d->name)) {
        U64 sect_name_off = string_table.total_size;
        str8_list_push_cstr(scratch.arena, &string_table, sect_name);

        sect_name = push_str8f(scratch.arena, "/%u", sect_name_off);
        AssertAlways(sect_name.size <= sizeof(d->name));
      }

      // section data
      U64 data_foff = 0;
      U64 data_size = 0;
      if (s->data.total_size > 0) {
        data_foff = srl.total_size;
        data_size = s->data.total_size;
        str8_list_concat_in_place(&srl, &s->data);
      }

      // section relocs
      U64 relocs_foff = 0;
      if (s->reloc_count) {
        AssertAlways(s->reloc_count <= max_U16);
        COFF_Reloc *relocs    = push_array(scratch.arena, COFF_Reloc, s->reloc_count);
        U64         reloc_idx = 0;
        for (COFF_ObjRelocNode *reloc_n = s->reloc_first; reloc_n != 0; reloc_n = reloc_n->next, reloc_idx += 1) {
          COFF_ObjReloc *rs = &reloc_n->v;
          COFF_Reloc    *rd = &relocs[reloc_idx];
          rd->apply_off = rs->apply_off;
          rd->isymbol   = rs->symbol->idx;
          rd->type      = rs->type;
        }
        relocs_foff = srl.total_size;
        str8_list_push(scratch.arena, &srl, str8_array(relocs, s->reloc_count));
      }

      // section header
      MemoryCopyStr8(d->name, sect_name);
      MemoryZeroTyped(d->name + sect_name.size, sizeof(d->name) - sect_name.size);
      d->vsize       = 0;
      d->voff        = 0;
      d->fsize       = data_size;
      d->foff        = data_foff;
      d->relocs_foff = relocs_foff;
      d->lines_foff  = 0;
      d->reloc_count = safe_cast_u32(s->reloc_count);
      d->line_count  = 0;
      d->flags       = s->flags;
    }
  }

  //
  // symbol table
  //
  if (obj_writer->symbol_count) {
    file_header->symbol_table_foff = srl.total_size;
    COFF_Symbol16 *symtab = push_array(scratch.arena, COFF_Symbol16, obj_writer->symbol_count);
    str8_list_push(scratch.arena, &srl, str8_array(symtab, obj_writer->symbol_count));
    {
      U64 symbol_idx = 0;
      for (COFF_ObjSymbolNode *symbol_n = obj_writer->symbol_first; symbol_n != 0; symbol_n = symbol_n->next) {
        COFF_ObjSymbol *s = &symbol_n->v;
        COFF_Symbol16  *d = &symtab[symbol_idx];

        COFF_SymbolName name = {0};
        // long name
        if (s->name.size > sizeof(name.short_name)) {
          U64 string_table_offset = string_table.total_size;
          str8_list_push_cstr(scratch.arena, &string_table, s->name);
          
          name.long_name.zeroes = 0;
          name.long_name.string_table_offset = safe_cast_u32(string_table_offset);
        }
        // short name
        else {
          MemoryCopyStr8(name.short_name, s->name);
          MemoryZeroTyped(name.short_name + s->name.size, sizeof(name.short_name) - s->name.size);
        }

        // symbol header
        AssertAlways(s->aux_symbols.node_count <= max_U8);
        d->name             = name;
        d->value            = s->value;
        switch (s->loc.type) {
        case COFF_SymbolLocation_Null: break;
        case COFF_SymbolLocation_Section: d->section_number = safe_cast_u16(s->loc.u.section->section_number); break;
        case COFF_SymbolLocation_Abs:     d->section_number = COFF_Symbol_AbsSection16;         break;
        case COFF_SymbolLocation_Undef:   d->section_number = COFF_Symbol_UndefinedSection;     break;
        }
        d->type             = s->type;
        d->storage_class    = s->storage_class;
        d->aux_symbol_count = (U8)s->aux_symbols.node_count;

        // aux symbols
        symbol_idx += 1;
        for (String8Node *aux_n = s->aux_symbols.first; aux_n != 0; aux_n = aux_n->next, symbol_idx += 1) {
          AssertAlways(aux_n->string.size <= sizeof(COFF_Symbol16));
          COFF_Symbol16 *a = &symtab[symbol_idx];
          MemoryZeroStruct(a);
          MemoryCopyStr8(a, aux_n->string);
        }
      }
    }
  }

  //
  // string table
  //
  *string_table_size = safe_cast_u32(string_table.total_size);
  str8_list_concat_in_place(&srl, &string_table);

  //
  // join
  //
  String8 obj = str8_list_join(arena, &srl, 0);

  scratch_end(scratch);
  return obj;
}