//Input Method Functions and Variables
//#include "imtable.h"
#define IM_BUFFER_LEN 32
#define IM_PREVIEW 1
#define IM_PREVIEW_ENTRIES 6
#define IM_PREVIEW_WIDTH (IM_TABLE_ENTRY_WIDTH+2)*IM_PREVIEW_ENTRIES
#define IM_ON_INDICATOR "CN"
#define IM_ON_INDICATOR_LEN 2
#define IM_OFF_INDICATOR "EN"
#define IM_OFF_INDICATOR_LEN 2
#define IM_INDICATOR_WIDTH 2
#include "boshiamy.h"

#define ENTER_KEY 0x0D
#define BACKSPACE_KEY 0x7F
//setting it to the actual escape character interferes with arrow keys and
//whatnot
//#define ESCAPE_KEY 0x1B
#define ESCAPE_KEY '`'
//Vertical Tab Ctrl+K
#define TOGGLE_KEY 0x0B
#define IM_KEY_RANGE_LEN 5

//Array of Input method key ranges(inclusive) seperate from the above
char im_key_ranges[IM_KEY_RANGE_LEN][2] = {
	{'a','z'},
	{'0','9'},
	{' ',' '},
	{',',','},
	{'.','.'},
};
int is_im_key(char input) {
	for (int i = 0; i < IM_KEY_RANGE_LEN; i++) {
		if (input >= im_key_ranges[i][0] && input <= im_key_ranges[i][1]) {
			return 1;
		}
	}
	return 0;
}
char im_buffer[IM_BUFFER_LEN+1];
char im_buffer_pos = 0;
int im_on = 1;
//clears the im buffer
void clear_im_buffer() {
	im_buffer[0] = 0;
	im_buffer_pos = 0;
}
//recursive search, returns -1 on failure
//searches from [start, end), 
//can limit itself to n bytes, if n=0, use IM_TABLE_ENTRY_LEN
int im_search(char * input, int start, int end, int n) {
	if (n == 0) {
		n = IM_TABLE_ENTRY_LEN;
	}
	// 0 width search
	if (end <= start) {
		return -1;
	}
	//test for middle, works even for 1 width middle=start
	int middle = start + (end-start)/2;
	//printf("testing:%s\n",im_table[middle][0]);
	int test = strncmp(im_table[middle][0], input, n);
	if (test == 0) {
		return middle;
	}
	//special case for width 1,2 region
	if ((end - start) == 1) {
		if (test == 0) {
			return start;
		} else {
			return -1;
		}
	}
	if (test == 0) {
		return 0;
	} else {
		if (test > 0) {
			return im_search(input,start,middle,n);
		} else {
			return im_search(input,middle,end,n);
		}
	}
	
}
//update_im_state is fed input characters 1 at a time, and gives 0 to
//IM_BUFFER_LEN output characters. 
//returns output len
int update_im_state(char input, char * output) {
	if (input == TOGGLE_KEY) {
		im_on = !im_on;
		//clears the im buffer if its toggling off
		if (!im_on) {
			clear_im_buffer();
		}
		//do not passthrough the toggle
		return 0;
	}
	//just passthrough if the im is off
	if (!im_on) {
		output[0] = input;
		output[1] = 0;
		return 1;
	}
	if ( is_im_key(input) ) {
		//check if there's enough room in the im buffer
		if ( (im_buffer_pos < IM_BUFFER_LEN) && (im_buffer_pos < IM_TABLE_ENTRY_LEN) ){
			im_buffer[im_buffer_pos] = input;
			im_buffer_pos++;
			im_buffer[im_buffer_pos] = 0;
		} else {
			//passthrough
			output[0] = input;
			output[1] = 0;
			return 1;
		}
		//if there's a match return it
		int im_entry = im_search(im_buffer, 0, IM_TABLE_LEN, 0);
		if (im_entry != -1) {
			//clear the buffer
			clear_im_buffer();
			strncpy(output, im_table[im_entry][1], IM_TABLE_ENTRY_LEN);
			return strlen(im_table[im_entry][1]);
		} else {
			return 0;
		}
	} else {
		//these only do something if there's something in the buffer, otherwise
		//passthrough
		if (im_buffer_pos > 0) {
			switch (input) {
				//escape, cancels
				case ESCAPE_KEY:
					clear_im_buffer();
					return 0;
				break;
				//enter, enters the buffer instead of sending it
				//to im
				case ENTER_KEY:
					strncpy(output, im_buffer, IM_BUFFER_LEN);
					int tmp = im_buffer_pos;
					clear_im_buffer();
					return tmp;
				break;
				//backspace
				case BACKSPACE_KEY:
					if (im_buffer_pos > 0) {
						im_buffer_pos--;
						im_buffer[im_buffer_pos] = 0;
					}
					return 0;
				break;
			}
		}
	}
	//default behavior of passthrough
	output[0] = input;
	output[1] = 0;
	return 1;
	
}
//prints im preview, assumes im_disp already moved it to the proper location
void im_preview(int fd, int trows, int tcols) {
	//searches for any im entries that match the im buffer, up to the
	//im_buffer length, because it's branching search it's not guaranteed to
	//be the first entry in the table that matches
	int first_entry = im_search(im_buffer, 0, IM_TABLE_LEN, im_buffer_pos);
	if (first_entry == -1) {
		return;
	}
	//keeps iterating until it finds the first entry in the table that
	//matches
	for (int i = first_entry; i>0 && i < IM_TABLE_LEN && (!strncmp(im_table[i][0],im_buffer,im_buffer_pos)); i--) {
		first_entry = i;
	}
	//preview buffer, each utf8 char could be up to 4 bytes, each new entry
	//catted on could be IM_TABLE_ENTRY_LEN*2 before next detection in loop,
	//so that + 1 margin for null byte
	char preview_buffer[IM_PREVIEW_ENTRIES*IM_TABLE_ENTRY_LEN*2+1] = "";
	//tracks how many entries we've added to the buffer so far
	int k = 0;
	for (int j = first_entry; j> 0 && j < IM_TABLE_LEN && (!strncmp(im_table[j][0],im_buffer,im_buffer_pos)); j++) {
		if (k >= IM_PREVIEW_ENTRIES) {
			break;
		}
		//even if the string is the same as im_buffer_pos, it will point
		//to a null pointer, which is treated as empty
		strncat(preview_buffer,&(im_table[j][0][im_buffer_pos]),1);
		strncat(preview_buffer,":",1);
		//assuming that each output is only 2 characters wide display
		strncat(preview_buffer,im_table[j][1], IM_TABLE_ENTRY_LEN);
		k++;
	}
	//writes the preview
	write(fd,preview_buffer,strlen(preview_buffer));
}
//Displays the IM on the bottom line, input is the number of actual physical
//rows and columns on the terminal descibed by fd
void disp_im(int fd, int trows, int tcols) {
	//generates the position escape sequence for the bottom left corner
	//2 spaces for the im indicator, 2 for buffer brackets,  +1 for automargin
	int im_col = tcols - IM_TABLE_ENTRY_LEN - IM_INDICATOR_WIDTH - 2  - 1;
	if (IM_PREVIEW) {
		im_col = im_col - IM_PREVIEW_WIDTH;
	}
	char pos_str[32] = "";
	int l = snprintf(pos_str, 32, "\033[%d;%df", trows, im_col);

	write(fd,"\0337",2); //saves previous cursor position
	write(fd, pos_str,l);
	write(fd,"\033[7m",4); //invert video

	//overwrite what was there previously, this works out to leaving 1 space
	//at the end for automargin b/c you need (tcols-im_col)+1 spaces, but
	//want -1 space so it doesn't write to the last character position
	write(fd,"                                                                  ",
		tcols-im_col);

	write(fd, pos_str,l);
	//im mode indicator
	if (im_on) {
		write(fd,IM_ON_INDICATOR,IM_ON_INDICATOR_LEN);
	} else {
		write(fd,IM_OFF_INDICATOR,IM_OFF_INDICATOR_LEN);
	}
	write(fd,"[",1);
	//actual buffer
	write(fd,im_buffer,im_buffer_pos);
	write(fd,"]",1);
	//if preview is set do that
	if (IM_PREVIEW) {
		im_preview(fd, trows, tcols);
	}
	//restore cursor pos and attrbutes
	write(fd,"\033[0m",4);
	write(fd,"\0338",2);
}