//
// Code editor widget for the Fast Light Tool Kit (FLTK).
// Syntax highlighting rewritten by erco@seriss.com 09/15/20.
//
// Copyright 1998-2024 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 necessary headers...
//

#include "CodeEditor.h"

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

// ---- CodeEditor implementation

/**
 Lookup table for all supported styles.
 Every table entry describes a rendering style for the corresponding text.
 */
Fl_Text_Display::Style_Table_Entry CodeEditor::styletable[] = {   // Style table
                  { FL_FOREGROUND_COLOR, FL_COURIER,        11 }, // A - Plain
                  { FL_DARK_GREEN,       FL_COURIER_ITALIC, 11 }, // B - Line comments
                  { FL_DARK_GREEN,       FL_COURIER_ITALIC, 11 }, // C - Block comments
                  { FL_BLUE,             FL_COURIER,        11 }, // D - Strings
                  { FL_DARK_RED,         FL_COURIER,        11 }, // E - Directives
                  { FL_DARK_RED,         FL_COURIER_BOLD,   11 }, // F - Types
                  { FL_BLUE,             FL_COURIER_BOLD,   11 }, // G - Keywords
                  { 220, /* med cyan */  FL_COURIER,        11 }  // H - Single quote chars
                };

/**
 Parse text and produce style data.
 \param[in] in_tbuff text buffer to parse
 \param[inout] in_sbuff style buffer we modify
 \param[in] in_len byte length to parse
 \param[in] in_style starting style letter
 */
void CodeEditor::style_parse(const char *in_tbuff,         // text buffer to parse
                             char       *in_sbuff,         // style buffer we modify
                             int         in_len,           // byte length to parse
                             char        in_style) {       // starting style letter
  // Style letters:
  //
  // 'A' - Plain
  // 'B' - Line comments  // ..
  // 'C' - Block comments /*..*/
  // 'D' - Strings        "xxx"
  // 'E' - Directives     #define, #include..
  // 'F' - Types          void, char..
  // 'G' - Keywords       if, while..
  // 'H' - Chars          'x'

  StyleParse sp;
  sp.tbuff  = in_tbuff;
  sp.sbuff  = in_sbuff;
  sp.len    = in_len;
  sp.style  = in_style;
  sp.lwhite = 1;        // 1:while parsing over leading white and first char past, 0:past white
  sp.col    = 0;
  sp.last   = 0;

  // Loop through the code, updating style buffer
  char c;
  while ( sp.len > 0 ) {
    c = sp.tbuff[0];  // current char
    if ( sp.style == 'C' ) {                              // Started in middle of comment block?
      if ( !sp.parse_block_comment() ) break;
    } else if ( strncmp(sp.tbuff, "/*", 2)==0 ) {         // C style comment block?
      if ( !sp.parse_block_comment() ) break;
    } else if ( c == '\\' ) {                             // Backslash escape char?
      if ( !sp.parse_escape() ) break;
    } else if ( strncmp(sp.tbuff, "//", 2)==0 ) {         // Line comment?
      if ( !sp.parse_line_comment() ) break;
    } else if ( c == '"' ) {                              // Start of double quoted string?
      if ( !sp.parse_quoted_string('"', 'D') ) break;
    } else if ( c == '\'' ) {                             // Start of single quoted string?
      if ( !sp.parse_quoted_string('\'', 'H') ) break;
    } else if ( c == '#' && sp.lwhite ) {                 // Start of '#' directive?
      if ( !sp.parse_directive() ) break;
    } else if ( !sp.last && (islower(c) || c == '_') ) {  // Possible C/C++ keyword?
      if ( !sp.parse_keyword() ) break;
    } else {                                              // All other chars?
      if ( !sp.parse_all_else() ) break;
    }
  }
}

/**
 Update unfinished styles.
 */
void CodeEditor::style_unfinished_cb(int, void*) {
}

/**
 Update the style buffer.
 \param[in] pos insert position in text
 \param[in] nInserted number of bytes inserted
 \param[in] nDeleted number of bytes deleted
 \param[in] cbArg pointer back to the code editor
 */
void CodeEditor::style_update(int pos, int nInserted, int nDeleted,
                              int /*nRestyled*/, const char * /*deletedText*/,
                              void *cbArg) {
  CodeEditor *editor = (CodeEditor*)cbArg;
  char       *style,                         // Style data
             *text;                          // Text data


  // If this is just a selection change, just unselect the style buffer...
  if (nInserted == 0 && nDeleted == 0) {
    editor->mStyleBuffer->unselect();
    return;
  }

  // Track changes in the text buffer...
  if (nInserted > 0) {
    // Insert characters into the style buffer...
    style = new char[nInserted + 1];
    memset(style, 'A', nInserted);
    style[nInserted] = '\0';

    editor->mStyleBuffer->replace(pos, pos + nDeleted, style);
    delete[] style;
  } else {
    // Just delete characters in the style buffer...
    editor->mStyleBuffer->remove(pos, pos + nDeleted);
  }

  // Select the area that was just updated to avoid unnecessary
  // callbacks...
  editor->mStyleBuffer->select(pos, pos + nInserted - nDeleted);

  // Reparse whole buffer, don't get cute. Maybe optimize range later
  int len = editor->buffer()->length();
  text  = editor->mBuffer->text_range(0, len);
  style = editor->mStyleBuffer->text_range(0, len);

  style_parse(text, style, editor->mBuffer->length(), 'A');

  editor->mStyleBuffer->replace(0, len, style);
  editor->redisplay_range(0, len);
  editor->redraw();

  free(text);
  free(style);
}

/**
 Find the right indentation depth after pressing the Enter key.
 \param[in] e pointer back to the code editor
 */
int CodeEditor::auto_indent(int, CodeEditor* e) {
  if (e->buffer()->selected()) {
    e->insert_position(e->buffer()->primary_selection()->start());
    e->buffer()->remove_selection();
  }

  int pos = e->insert_position();
  int start = e->line_start(pos);
  char *text = e->buffer()->text_range(start, pos);
  char *ptr;

  for (ptr = text; isspace(*ptr); ptr ++) {/*empty*/}
  *ptr = '\0';
  if (*text) {
    // use only a single 'insert' call to avoid redraw issues
    size_t n = strlen(text);
    char *b = (char*)malloc(n+2);
    *b = '\n';
    strcpy(b+1, text);
    e->insert(b);
    free(b);
  } else {
    e->insert("\n");
  }
  e->show_insert_position();
  e->set_changed();
  if (e->when()&FL_WHEN_CHANGED) e->do_callback(FL_REASON_CHANGED);

  free(text);

  return 1;
}

/**
 Create a CodeEditor widget.
 \param[in] X, Y, W, H position and size of the widget
 \param[in] L optional label
 */
CodeEditor::CodeEditor(int X, int Y, int W, int H, const char *L) :
  Fl_Text_Editor(X, Y, W, H, L) {
  buffer(new Fl_Text_Buffer);

  char *style = new char[mBuffer->length() + 1];
  char *text = mBuffer->text();

  memset(style, 'A', mBuffer->length());
  style[mBuffer->length()] = '\0';

  highlight_data(new Fl_Text_Buffer(mBuffer->length()), styletable,
                 sizeof(styletable) / sizeof(styletable[0]),
                 'A', style_unfinished_cb, this);

  style_parse(text, style, mBuffer->length(), 'A');

  mStyleBuffer->text(style);
  delete[] style;
  free(text);

  mBuffer->add_modify_callback(style_update, this);
  add_key_binding(FL_Enter, FL_TEXT_EDITOR_ANY_STATE,
                  (Fl_Text_Editor::Key_Func)auto_indent);
}

/**
 Destroy a CodeEditor widget.
 */
CodeEditor::~CodeEditor() {
  Fl_Text_Buffer *buf = mStyleBuffer;
  mStyleBuffer = 0;
  delete buf;

  buf = mBuffer;
  buffer(0);
  delete buf;
}

/**
 Attempt to make the fluid code editor widget honor textsize setting.
 This works by updating the fontsizes in the style table.
 \param[in] s the new general height of the text font
 */
void CodeEditor::textsize(Fl_Fontsize s) {
  Fl_Text_Editor::textsize(s); // call base class method
  // now attempt to update our styletable to honor the new size...
  int entries = sizeof(styletable) / sizeof(styletable[0]);
  for(int iter = 0; iter < entries; iter++) {
    styletable[iter].size = s;
  }
} // textsize

// ---- CodeViewer implementation

/**
 Create a CodeViewer widget.
 \param[in] X, Y, W, H position and size of the widget
 \param[in] L optional label
 */
CodeViewer::CodeViewer(int X, int Y, int W, int H, const char *L)
: CodeEditor(X, Y, W, H, L)
{
  default_key_function(kf_ignore);
  remove_all_key_bindings(&key_bindings);
  cursor_style(CARET_CURSOR);
}

/**
 Tricking Fl_Text_Display into using bearable colors for this specific task.
 */
void CodeViewer::draw()
{
  Fl_Color c = Fl::get_color(FL_SELECTION_COLOR);
  Fl::set_color(FL_SELECTION_COLOR, fl_color_average(FL_BACKGROUND_COLOR, FL_FOREGROUND_COLOR, 0.9f));
  CodeEditor::draw();
  Fl::set_color(FL_SELECTION_COLOR, c);
}

// ---- TextViewer implementation

/**
 Create a TextViewer widget.
 \param[in] X, Y, W, H position and size of the widget
 \param[in] L optional label
 */
TextViewer::TextViewer(int X, int Y, int W, int H, const char *L)
: Fl_Text_Display(X, Y, W, H, L)
{
  buffer(new Fl_Text_Buffer);
}

/**
 Avoid memory leaks.
 */
TextViewer::~TextViewer() {
  Fl_Text_Buffer *buf = mBuffer;
  buffer(0);
  delete buf;
}

/**
 Tricking Fl_Text_Display into using bearable colors for this specific task.
 */
void TextViewer::draw()
{
  Fl_Color c = Fl::get_color(FL_SELECTION_COLOR);
  Fl::set_color(FL_SELECTION_COLOR, fl_color_average(FL_BACKGROUND_COLOR, FL_FOREGROUND_COLOR, 0.9f));
  Fl_Text_Display::draw();
  Fl::set_color(FL_SELECTION_COLOR, c);
}