//
// Basic Fl_String class for the Fast Light Tool Kit (FLTK).
//
// Copyright 2021-2023 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     https://www.fltk.org/COPYING.php
//
// Please see the following page on how to report bugs and issues:
//
//     https://www.fltk.org/bugs.php
//

#include <FL/Fl_String.H>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>


/** \file src/Fl_String.cxx
 Basic Fl_String class for FLTK.
 */


/*
 If buffer_ is NULL, c_str() and buffer() will point here.
 */
const char Fl_String::NUL = 0;

/**
 Indicate a maximum value or error.
 This value is generally used as end of string indicator or as the error
 indicator by the functions that return a string index.
 */
const int Fl_String::npos = INT_MAX;

/**
 Initialise the class instance.
 */
void Fl_String::init_() {
  buffer_ = NULL;
  size_ = 0;
  capacity_ = 0;
}

/**
 Grow the buffer to a capacity of at least n bytes.

 This method will always grow the buffer size, or keep it as is, but never
 shrink it. Use shrink_to_fit() to shrink the buffer as much as possible.

 \param[in] n number of bytes needed, not counting the trailing NUL
 */
void Fl_String::grow_(int n) {
  if (n <= capacity_)
    return;
  int alloc_size_ = n + 1; // trailing NUL
  // round n up so we can grow in chunks
  if (alloc_size_ <= 24) { // allocate at least 24 bytes
    alloc_size_ = 24;
  } else if (alloc_size_ < 1024 + 8) {
    alloc_size_ = ((alloc_size_+128-8) & ~127) + 8; // allocate in 128 byte chunks
  } else {
    alloc_size_ = ((alloc_size_+2048-8) & ~2047) + 8; // allocate in 2k chunks
    // adding 8 keeps the buffer 64-bit aligned while generating a space for
    // the trailing NUL without jumping to the next chunk size for common
    // allocations like 1024 or 2048 (FL_PATH_MAX).
  }
  // allocate now
  char *new_buffer = (char*)::malloc(alloc_size_);
  if (buffer_ && (size_ > 0)) {
    memcpy(new_buffer, buffer_, size_);
    ::free(buffer_);
  }
  if (size_ >= 0)
    new_buffer[size_] = 0; // trailing NUL
  buffer_ = new_buffer;
  capacity_ = alloc_size_-1;  // trailing NUL
}

/**
 Shrink the buffer to n bytes, or size, if size > n.

 Shrink the buffer as much as possible. If \p n is 0 and the string is empty,
 the buffer will be released.

 \param[in] n shrink buffer to n bytes, not counting the trailing NUL
 */
void Fl_String::shrink_(int n) {
  if (n < size_)
    n = size_;
  if (n == capacity_)
    return;
  if (n == 0) {
    if (buffer_)
      ::free(buffer_);
    buffer_ = NULL;
  } else {
    buffer_ = (char*)::realloc(buffer_, n+1); // NUL
    buffer_[size_] = 0; // trailing NUL
  }
  capacity_ = n;
}

/**
 Remove \p n_del bytes at \p at and insert \p n_ins bytes from \p src.

 String will remain NUL terminated. Data in \p ins may contain NULs.

 \param[in] at    remove and insert bytes at this index
 \param[in] n_del number of bytes to remove
 \param[in] ins   insert bytes from here, can be NULL if \p n_ins is also 0
 \param[in] n_ins number of bytes to insert
 \return self
 */
Fl_String &Fl_String::replace_(int at, int n_del, const char *ins, int n_ins) {
  if (at > size_) at = size_;
  if (n_del > size_ - at) n_del = size_ - at;
  int diff = n_ins - n_del, new_size = size_ + diff;
  if (diff) {
    int src = at + n_del, dst = at + n_ins, n = size_ - src;
    grow_(new_size);
    if (n > 0) ::memmove(buffer_+dst, buffer_+src, n);
  }
  if (n_ins > 0) {
    ::memmove(buffer_+at, ins, n_ins);
  }
  size_ = new_size;
  buffer_[size_] = 0;
  return *this;
}


// ---- Assignment ----------------------------------------------------- MARK: -

/**
 Allocate an empty string.
 */
Fl_String::Fl_String() {
  init_();
}

/**
 Copy constructor.
 \param[in] str copy from another Fl_String
 */
Fl_String::Fl_String(const Fl_String &str) {
  init_();
  assign(str);
}

/**
 Constructor from a C-style string.
 \param[in] cstr a NUL terminated C-style string
 */
Fl_String::Fl_String(const char *cstr) {
  init_();
  assign(cstr);
}

/**
 Constructor from data of \p size bytes.
 \param[in] str   a block of data that may contain NUL characters
 \param[in] size  number of bytes to copy
 */
Fl_String::Fl_String(const char *str, int size) {
  init_();
  assign(str, size);
}

/**
 Destructor.
 */
Fl_String::~Fl_String() {
  if (buffer_)
    ::free(buffer_);
}

/**
 Copy assignment operator
 \param[in] str copy from another Fl_String
 \return self
 */
Fl_String &Fl_String::operator=(const Fl_String &str) {
  return assign(str);
}

/**
 Assign a C-style string.
 \param[in] cstr a NUL terminated C-style string
 \return self
 */
Fl_String &Fl_String::operator=(const char *cstr) {
  return assign(cstr);
}

/**
 Copy another string.
 \param[in] str copy from another Fl_String
 \return self
 */
Fl_String &Fl_String::assign(const Fl_String &str) {
  if (&str == this) return *this;
  return assign(str.data(), str.size());
}

/**
 Assign a C-style string.
 \param[in] cstr a NUL terminated C-style string
 \return self
 */
Fl_String &Fl_String::assign(const char *cstr) {
  if (cstr && *cstr) {
    int len = (int)::strlen(cstr);
    return assign(cstr, len);
  } else {
    resize(0);
  }
  return *this;
}

/**
 Assign a data block of \p size bytes.
 \param[in] str a block of data that may contain NUL characters
 \param[in] size number of bytes to copy
 \return self
 */
Fl_String &Fl_String::assign(const char *str, int size) {
  if (size > 0) {
    grow_(size);
    memcpy(buffer_, str, size);
    buffer_[size] = 0;
    size_ = size;
  } else {
    resize(0);
  }
  return *this;
}

// ---- Element Access ------------------------------------------------- MARK: -

/**
 Returns the character at specified bounds checked location.
 \param[in] n index of character
 \return character at that index, or NUL if out of bounds
 */
char Fl_String::at(int n) const {
  if ((n < 0) || (n >= size_))
    return 0;
  return operator[](n);
}

/**
 Returns the character at specified location.
 \param[in] n index of character
 \return character at that index
 */
char Fl_String::operator[](int n) const {
  if (buffer_)
    return buffer_[n];
  else
    return 0;
}

/**
 Returns a reference to the character at specified location.
 \param[in] n index of character
 \return reference to that character, so it can be used as lvalue
 */
char &Fl_String::operator[](int n) {
  if (!buffer_)
    reserve(1);
  return buffer_[n];
}

/**
 Return a pointer to the NUL terminated string.
 \return reference to non-mutable string
 */
const char *Fl_String::data() const {
  if (buffer_)
    return buffer_;
  else
    return &NUL;
}

/**
 Return a pointer to the writable NUL terminated string.
 \return reference to mutable string
 */
char *Fl_String::data() {
  if (!buffer_)
    reserve(1);
  return buffer_;
}

/**
 Return a pointer to the NUL terminated string.

 \return reference to non-mutable string

 \note same as Fl_String::data() const
 */
const char *Fl_String::c_str() const {
  return data();
}

// ---- Capacity ------------------------------------------------------- MARK: -

/**
 Checks if the string is empty.
 \return true if string contains no data
 */
bool Fl_String::empty() const {
  return (size_ == 0);
}

/**
 Returns the number of bytes in the string.
 \return number of bytes in string, not counting trailing NUL
 */
int Fl_String::size() const {
  return size_;
}

/**
 Reserve n bytes for storage.
 If n is less or equal than size, the capacity is set to size.
 \param[in] n requested minimum size, not counting trailing NUL
 */
void Fl_String::reserve(int n) {
  grow_(n);
}

/**
 Return the number of chars that are allocated for storage.
 \return string capacity, not counting trailing NUL
 */
int Fl_String::capacity() const {
  return capacity_;
}

/**
 Shrink the capacity to fit the current size.
 */
void Fl_String::shrink_to_fit() {
  shrink_(size_);
}

// ---- Operations ----------------------------------------------------- MARK: -

/**
 Set an empty string.
 */
void Fl_String::clear() {
  resize(0);
}

/**
 Insert a C-style string or data.
 \param[in] at    insert at this index
 \param[in] src   copy bytes from here
 \param[in] n_ins optional number of bytes to copy - if not set, copy C-style string
 \return self
 */
Fl_String &Fl_String::insert(int at, const char *src, int n_ins) {
  if (n_ins == npos) n_ins = src ? (int)::strlen(src) : 0;
  return replace_(at, 0, src, n_ins);
}

/**
 Insert another string.
 \param[in] at    insert at this index
 \param[in] src   copy string from here
 \return self
 */
Fl_String &Fl_String::insert(int at, const Fl_String &src) {
  return replace_(at, 0, src.buffer_, src.size_);
}

/**
 Erase some bytes within a string.
 \param[in] at    erase at this index
 \param[in] n_del number of bytes to erase
 \return self
 */
Fl_String &Fl_String::erase(int at, int n_del) {
  return replace_(at, n_del, NULL, 0);
}

/**
 Append a single character.
 \param[in] c append this byte
 */
void Fl_String::push_back(char c) {
  replace_(size_, 0, &c, 1);
}

/**
 Remove the last character.
 */
void Fl_String::pop_back() {
  replace_(size_-1, 1, NULL, 0);
}

/**
 Append a C-style string or data.
 \param[in] src   copy bytes from here
 \param[in] n_ins optional number of bytes to copy - if not set, copy C-style string
 \return self
 */
Fl_String &Fl_String::append(const char *src, int n_ins) {
  if (n_ins == npos) n_ins = src ? (int)::strlen(src) : 0;
  return replace_(size_, 0, src, n_ins);
}

/**
 Append another string.
 \param[in] src   copy string from here
 \return self
 */
Fl_String &Fl_String::append(const Fl_String &src) {
  return replace_(size_, 0, src.buffer_, src.size_);
}

/**
 Append a single byte.
 \param[in] c single byte character
 \return self
 */
Fl_String &Fl_String::append(char c) {
  push_back(c);
  return *this;
}

/**
 Append a C-style string or data.
 \param[in] src   copy C-style string from here
 \return self
 */
Fl_String &Fl_String::operator+=(const char *src) {
  return append(src);
}

/**
 Append another string.
 \param[in] src   copy string from here
 \return self
 */
Fl_String &Fl_String::operator+=(const Fl_String &src) {
  return append(src);
}

/**
 Append a single byte.
 \param[in] c single byte character
 \return self
 */
Fl_String &Fl_String::operator+=(char c) {
  return append(c);
}

/**
 Find a string inside this string.
 \param[in] needle    find this string
 \param[in] start_pos start looking at this position
 \return the offset of the text inside this string, if it was found
 \return Fl_String::npos if the needle was not found
 */
int Fl_String::find(const Fl_String &needle, int start_pos) const {
  if ((start_pos < 0) || (start_pos >= size_)) return npos;
  const char *haystack = data() + start_pos;
  const char *found = strstr(haystack, needle.c_str());
  if (!found) return npos;
  return (int)(found - data());
}

/**
 Replace part of the string with a C-style string or data.
 \param[in] at    erase and insert at this index
 \param[in] n_del number of bytes to erase
 \param[in] src   copy bytes from here
 \param[in] n_ins optional number of bytes to copy - if not set, copy C-style string
 \return self
 */
Fl_String &Fl_String::replace(int at, int n_del, const char *src, int n_ins) {
  if (n_ins == npos) n_ins = src ? (int)::strlen(src) : 0;
  return replace_(at, n_del, src, n_ins);
}

/**
 Replace part of the string with another string.
 \param[in] at    erase and insert at this index
 \param[in] n_del number of bytes to erase
 \param[in] src   copy string from here
 \return self
 */
Fl_String &Fl_String::replace(int at, int n_del, const Fl_String &src) {
  return replace_(at, n_del, src.buffer_, src.size_);
}

/**
 Return a substring from a string.
 \param[in] pos   copy string from here - if omitted, copy from start
 \param[in] n     number of bytes - if omitted, copy all bytes
 \return a new string
 */
Fl_String Fl_String::substr(int pos, int n) const {
  if (n > size_) n = size_;
  int first = pos, last = pos + n;
  if ((first < 0) || (first > size_) || (last <= first))
    return Fl_String();
  if (last > size_) last = size_;
  return Fl_String(buffer_+first, last-first);
}

/**
 Resizes the string to n characters.

 If \p n is less than the current size, the string will be cropped. If \p n
 is more than the current size, the new space will be filled with
 NUL characters.

 \param[in] n   new size of string
 */
void Fl_String::resize(int n) {
  if (n == size_)
    return;
  if (n < size_) {
    size_ = n;
    if (buffer_) buffer_[size_] = 0;
  } else {
    grow_(n);
    if (buffer_) ::memset(buffer_+size_, 0, n-size_+1);
  }
  size_ = n;
}

// --- Non Standard ---------------------------------------------------- MARK: -

/**
 Returns the number of bytes until the first NUL byte.
 \return number of bytes in C-style string
 */
int Fl_String::strlen() const {
  if (!buffer_) return 0;
  return (int)::strlen(buffer_);
}

/**
  Write some details about the string to stdout.

  Nothing at all is written if \p info is NULL, otherwise the short info
  string and details are written to stdout.

  The \p info string should not be longer than 20 characters to align the
  debug output of several strings.

  \param[in]  info  short info string or NULL
*/
void Fl_String::debug(const char *info) const {
  if (info) {
    printf("Fl_String '%-20s': %p, value = %p (%d/%d):\n%s\n",
           info, this, buffer_, size_, capacity_, buffer_ ? buffer_ : "<NULL>");
  }
}

/**
  Write some details about the string to stdout, followed by a hex dump of
  the string.

  The first part is the same as written by Fl_String::debug(). The following
  part is a hexadecimal dump of all bytes of the string. Embedded \p nul bytes
  are possible and will be dumped as well.

  \param[in]  info  short info string or NULL

  \see Fl_String::debug(const char *info) const
*/
void Fl_String::hexdump(const char *info) const {
  debug(info);
  if (size_ == 0)
    return;
  for (int i = 0; i < size_; i++) {
    if ((i & 15) == 0) {
      if (i > 0)
        printf("\n");
      printf("  [%04x %4d] ", i, i);  // position
    } else if ((i & 3) == 0) {        // separator after 4 bytes
      printf(" ");
    }
    printf(" %02x", (unsigned char)buffer_[i]);
  }
  printf("\n");
}

// ---- Non-member functions ------------------------------------------- MARK: -

/**
 Concatenate two strings.
 \param[in] lhs first string
 \param[in] rhs second string
 \return self
 */
Fl_String operator+(const Fl_String &lhs, const Fl_String &rhs) {
  Fl_String ret = lhs;
  return ret += rhs;
}

/**
 Concatenate two strings.
 \param[in] lhs first string
 \param[in] rhs second C-style string
 \return self
 */
Fl_String operator+(const Fl_String &lhs, const char *rhs) {
  Fl_String ret = lhs;
  return ret += rhs;
}

/**
 Compare two strings.
 \param[in] lhs first string
 \param[in] rhs second string
 \return true if strings are the same size and have the same content
 */
bool operator==(const Fl_String &lhs, const Fl_String &rhs) {
  if (lhs.size() == rhs.size()) {
    int sz = lhs.size();
    if (sz == 0) return true;
    if (memcmp(lhs.data(), rhs.data(), sz) == 0) return true;
  }
  return false;
}