/* date = May 7th 2023 9:01 pm */

#ifndef VN_STRING_H
#define VN_STRING_H

inline b32 IsWhitespace(char C)
{
  b32 Result = ((C == ' ') ||
                (C == '\n') ||
                (C == '\t') ||
                (C == '\r'));
  return(Result);
}

inline s64 StringLength(char *String)
{
  s64 Result = 0;
  while(*String++)
  {
    ++Result;
  }
  return(Result);
}

inline u64 HashString(string String)
{
  u64 Result = 5731;
  for(s64 Index = 0;
      Index < String.Count;
      ++Index)
  {
    Result += String.Data[Index];
    Result ^= Result << 13;
    Result ^= Result >> 7;
    Result ^= Result << 17;
  }
  
  return(Result);
}

inline string MakeStringFromCString(char *Data)
{
  string Result = {StringLength(Data), (u8 *)Data};
  return(Result);
}

inline b32 AreEqual(string A, string B)
{
  b32 Result = false;
  if(A.Count == B.Count)
  {
    Result = true;
    
    for(s64 Index = 0;
        Index < A.Count;
        ++Index)
    {
      if(A.Data[Index] != B.Data[Index])
      {
        Result = false;
        break;
      }
    }
  }
  
  return(Result);
}

inline s64 FirstIndexOf(string String, char Char)
{
  s64 Result = -1;
  for(s64 Index = 0;
      Index < String.Count;
      ++Index)
  {
    if(String.Data[Index] == Char)
    {
      Result = Index;
      break;
    }
  }
  return(Result);
}

inline s64 LastIndexOf(string String, char Char)
{
  s64 Result = -1;
  for(s64 Index = String.Count-1;
      Index >= 0;
      --Index)
  {
    if(String.Data[Index] == Char)
    {
      Result = Index;
      break;
    }
  }
  return(Result);
}

inline s64 LastIndexOf(string String, string Substring)
{
  s64 Result = -1;
  if(String.Count >= Substring.Count)
  {
    for(s64 Index = String.Count-Substring.Count;
        Index >= 0;
        --Index)
    {
      string ToCheck = MakeString((char *)String.Data + Index, Substring.Count);
      if(AreEqual(ToCheck, Substring))
      {
        Result = Index;
        break;
      }
    }
  }
  return(Result);
}

static s64 UTF8FromCodepoint(u8 *Out, u32 Codepoint)
{
  s64 Length = 0;
  if(Codepoint <= 0x7F)
  {
    Out[0] = (u8)Codepoint;
    Length = 1;
  }
  else if(Codepoint <= 0x7FF)
  {
    Out[0] = (0x3 << 6) | ((Codepoint >> 6) & 0x1F);
    Out[1] = 0x80       | ( Codepoint       & 0x3F);
    Length = 2;
  }
  else if(Codepoint <= 0xFFFF)
  {
    Out[0] = (0x7 << 5) | ((Codepoint >> 12) & 0x0F);
    Out[1] = 0x80       | ((Codepoint >> 6) & 0x3F);
    Out[2] = 0x80       | ( Codepoint       & 0x3F);
    Length = 3;
  }
  else if(Codepoint <= 0x10FFFF)
  {
    Out[0] = (0xF << 4) | ((Codepoint >> 12) & 0x07);
    Out[1] = 0x80       | ((Codepoint >> 12) & 0x3F);
    Out[2] = 0x80       | ((Codepoint >> 6)  & 0x3F);
    Out[3] = 0x80       | ( Codepoint        & 0x3F);
    Length = 4;
  }
  else
  {
    Out[0] = '?';
    Length = 1;
  }
  
  return(Length);
}

inline s64 GetCodepointSize(u32 Codepoint)
{
  s64 Result = 0;
  if(Codepoint <= 0x7F)
  {
    Result = 1;
  }
  else if(Codepoint <= 0x7FF)
  {
    Result = 2;
  }
  else if(Codepoint <= 0xFFFF)
  {
    Result = 3;
  }
  else if(Codepoint <= 0x10FFFF)
  {
    Result = 4;
  }
  else
  {
    Result = 1;
  }
  return(Result);
}

// sixten(TODO): Remove this forward decl.
inline string PushCString(struct memory_arena *Arena, char *CString);

inline string StringFromCodepoint(struct memory_arena *Arena, u32 Codepoint)
{
  char Buffer[5] = {};
  UTF8FromCodepoint((u8 *)Buffer, Codepoint);
  
  string Result = PushCString(Arena, Buffer);
  return(Result);
}

struct utf8_iterator
{
  string Data;
  s64 Index;
  
  u32 Codepoint;
};

inline void Advance(utf8_iterator *Iter)
{
  u8 *At = Iter->Data.Data + Iter->Index;
  
  if(Iter->Index < Iter->Data.Count)
  {
    if((At[0] & 0x80) == 0x00)
    {
      Iter->Codepoint = (At[0] & 0x7F);
      Iter->Index += 1;
    }
    else if((At[0] & 0xE0) == 0xC0)
    {
      Iter->Codepoint = ((At[0] & 0x1F) << 6)|(At[1] & 0x3F);
      Iter->Index += 2;
    }
    else if((At[0] & 0xF0) == 0xE0)
    {
      Iter->Codepoint = ((At[0] & 0x0F) << 12)|((At[1] & 0x3F) << 6)|(At[2] & 0x3F);
      Iter->Index += 3;
    }
    else if((Iter->Data.Data[Iter->Index] & 0xF8) == 0xF0)
    {
      Iter->Codepoint = ((At[0] & 0x0F) << 18)|((At[1] & 0x3F) << 12)|((At[2] & 0x3F) << 6)|(At[3] & 0x3F);
      Iter->Index += 4;
    }
  }
  else
  {
    Iter->Codepoint = 0;
  }
}

inline utf8_iterator IterateUTF8String(string String)
{
  utf8_iterator Iter = {};
  Iter.Data = String;
  Advance(&Iter);
  
  return(Iter);
}

#endif //VN_STRING_H