helper.h

/***
 * helper.h
 *
 * This header file contains all the related fucntion declarations, imports
 * and macros for handing various escape sequences
 *
 * Author: Abhishek Shrivastava <abhishek.shrivastava.ts@gmail.com>
 */

// Header guard  we don't want to deal with multiple import of same type
#ifndef HELPER
#define HELPER

// system header files required go here
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <ctype.h>


// macros for escape sequences go here
#define clrscr              printf("\033c")  //VT100 magic clear screen without scroll
#define gotopos(row,col)    printf("\033[%d;%dH", (row), (col)) // gotopos will always be off by one (counts from 0)

// escape characters for keys
#define ESCAPE              0x001b
#define ENTER               0x000a
#define UP                  0x0105
#define DOWN                0x0106
#define LEFT                0x0107
#define RIGHT               0x0108
#define BACKSPACE           0x7f
#define DELETE              126
#define LF                  10
#define CR                  13

// Color codes
#define RED                 "\x1B[31m"
#define GRN                 "\x1B[32m"
#define YEL                 "\x1B[33m"
#define BLU                 "\x1B[34m"
#define MAG                 "\x1B[35m"
#define CYN                 "\x1B[36m"
#define WHT                 "\x1B[37m"
#define RESET               "\x1B[0m"

#define REDBG               "\x1B[33m\x1B[41m" // escape code for a redbackround 41m

// application defaults
#define NORMAL_MODE         "Normal"
#define INSERT_MODE         "Insert"
#define REPLACE_MODE        "Replace"
#define DEFAULT_FILE_NAME   "[NoName]"
#define DEFAULT_MODE        "Normal"
#define CMD_LEN             80
#define LINE_SIZE           80
#define TAB_LENGTH          4
#define LINE_NUMBERS        0 // set to 1 for line number on, experimental

/*
 * A sequence will contain the metadata about the particular row
 * Reference - https://www.cs.unm.edu/~crowley/papers/sds.pdf
 * And the original Vi editor
 *
 * Linked line approach -
 *  The document is represented as linked list of different sequences.
 *  This is better than using a 2D array for document because line insertions
 *  are pretty easy and termination also, just have to use \0
 *
 * prev         - the previous line
 * sequence_row - the row number at which the sequence is supposed to come
 * len          - the length of sequence
 * max_len      - maximum length posssible of the seq (defined using malloc)
 * data         - a pointer to the stored string;
 * next         - the next line
 *
 * This type is defined here so that we can use sequence* in func decl
 */
typedef struct sequence
{
  struct sequence* prev;
  int seq_row;
  int len;
  int max_len;
  char* data;
  struct sequence* next;
} sequence;



// function declaration 
void getControl(int fd); // to set terminal attributes
void readKey(FILE*); // master method for reading keys
void handleEscapeSequence(void); // handling escape seq
void handle_winresize(int sig); // singal for handling window resizee
void initscr(void); // initalize the editor config
void drawWindow(void); // draw the window 
void setStatusLine(void); // set the status line and go back to your postion
void modify_seq_len(int); // modify the current sequence length 
void modify_cur_pos(int, int, int); // modify the cursor position by some value
void insert(sequence*, int, int, char); // memmove for inserting
int  readFile(char*); // read the files
void readKeyNormal(void); // this method is used to read charactes in normal mode
void replace(void); // replace the text under the cursor
void interpretCommand(void); // to handle the command mode
void exit_safely(void); // to safely exit the editor after freeing the memory
void writeFile(void); // method to write the file to disk
void executeBash(); // execute the bash command input
void updateRowNumber(sequence*, int); // update row numbers 
void gHandler(int); // method to handle gg, G

/*
 * config struct holds all the information related to the current state of
 * editor
 *
 * w_row    - number of rows supported by window, will change with window resize
 * w_col    - number of cols supported by window, will change with window resize
 * cursor_row - the current row coordinate of cursor
 * curosr_col - the current col coordinate of cursor
 * is_mod   - boolean to check whether the data in editor was modified or not
 * mode     - the mode the editor is opetating in
 * filename - the name of file being currently edited
 * openfile - filepointer to the open file
 * act_rows - the number of active rows
 * cmd_buf  - the command buffer, which holds the text displated at bottom
 * first_seq- pointer to the first sequence of doc
 * current_seq- pointer to the sequence with the cursor on it
 * o_term - old terminal props
 * n_term - new terminal props
 */
typedef struct
{
  int w_row;
  int w_col;
  int cursor_row;
  int cursor_col;
  int is_mod;
  char* mode; // 0 is for NORMAL, 1 is for EDIT
  char* filename;
  FILE* openFile;
  int act_rows; // number of active rows must match the number of sequecnes
  char* cmd_buf;
  sequence* first_seq;
  sequence* current_seq;
  int start_line;
  int end_line;
  int actual_row;
  int actual_col;
  struct termios o_term;
  struct termios n_term;
} config;


/* extern variables go here
 * global so we use suffix g_
 * This only tells the other files that this variable exists
 */
extern config g_tavProps;

#endif