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June 6, 2020 20:40
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// Example program | |
#include <iostream> | |
#include <string> | |
#include <cmath> | |
#include <algorithm> | |
#include <sstream> | |
using u64 = size_t; | |
enum direction | |
{ | |
invalid, | |
left, | |
right, | |
up, | |
down | |
}; | |
const std::string text = | |
"01234\n" | |
"56789\n" | |
"ab\n" | |
"cdefg\n" | |
"\n" | |
"h\n" | |
"\n" | |
"ijklmnop"; | |
const std::string text_big = | |
" 0 1 2 3 4 \n" | |
" 5 6 7 8 9 \n" | |
" a b \n" | |
" c d e f g \n" | |
" \n" | |
" h \n" | |
" \n" | |
" i j k l m n o p "; | |
void refresh() | |
{ | |
} | |
std::stringstream debug; | |
size_t get_pos(direction dir, size_t caret_position) | |
{ | |
debug.str(""); | |
switch (dir) | |
{ | |
case left: | |
{ | |
if (caret_position) | |
{ | |
caret_position--; | |
} | |
break; | |
} | |
case right: | |
{ | |
if (caret_position < text.length()) | |
{ | |
caret_position++; | |
} | |
break; | |
} | |
case up: | |
{ | |
debug << "caret_position is " << caret_position << "\n"; | |
u64 current_line_start = text.rfind("\n", caret_position - 1); | |
if (current_line_start == std::string::npos) | |
{ | |
// This is the first line, so caret moves to the very beginning | |
caret_position = 0; | |
debug << "current_line_start is 'npos', caret_position set to 0\n"; | |
break; | |
} | |
else | |
{ | |
// current line is not first, caret should ignore found '\n' | |
current_line_start += 1; | |
debug << "current_line_start is " << current_line_start << "\n"; | |
} | |
const u64 caret_pos_in_line = caret_position - current_line_start; | |
debug << "caret_pos_in_line is " << caret_pos_in_line << "\n"; | |
const u64 prev_line_end = current_line_start - 2; // ignore current char and \n before it | |
debug << "prev_line_end is " << prev_line_end << "\n"; | |
u64 prev_line_start = text.rfind("\n", prev_line_end); | |
if (prev_line_start == std::string::npos) | |
{ | |
// if previous line is the first line, there is no '\n' at the beginning | |
prev_line_start = 0; | |
debug << "prev_line_start is 'npos', prev_line_start set to 0\n"; | |
} | |
else | |
{ | |
prev_line_start += 1; | |
debug << "current_line_start is " << current_line_start << "\n"; | |
} | |
const u64 prev_line_length = prev_line_end - prev_line_start + 1; // delta in indexes requires +1 | |
debug << "prev_line_length is " << prev_line_length << "\n"; | |
// TODO : Save caret position to some kind of buffer, so after switching back and forward, caret would be on initial position | |
if (prev_line_length < caret_pos_in_line) | |
{ | |
// Previous line is shorter than current caret position, so caret moves to the very end of the previous line | |
caret_position = prev_line_end + 1; | |
debug << "prev_line_length " << prev_line_length << " is less than caret_pos_in_line " << | |
caret_pos_in_line << ", so caret_position is " << caret_position << "\n"; | |
} | |
else | |
{ | |
// Previous line is longer than current, so caret should offset from prev_line_beginning the exact same distance as in current line | |
caret_position = prev_line_start + caret_pos_in_line; | |
debug << "prev_line_length " << prev_line_length << " is greater than caret_pos_in_line " << | |
caret_pos_in_line << ", so caret_position is set to " << caret_position << "\n"; | |
} | |
break; | |
} | |
case down: | |
{ | |
u64 current_line_end = text.find("\n", caret_position); | |
if (current_line_end == std::string::npos) | |
{ | |
// This is the last line, so caret moves to the very end | |
caret_position = text.length(); | |
debug << "current_line_end is 'npos', caret_position set to " << text.length() << "\n"; | |
break; | |
} | |
else | |
{ | |
// move to the last character of the current line | |
current_line_end -= 1; | |
debug << "current_line_end is " << current_line_end << "\n"; | |
} | |
u64 current_line_start = text.rfind("\n", current_line_end); | |
if (current_line_start == std::string::npos) | |
{ | |
// if current line is the first one - there is no '\n' before it, so line starts from index 0 | |
current_line_start = 0; | |
debug << "current_line_start is 'npos', caret_position set to 0\n"; | |
} | |
else | |
{ | |
// if line is not first, than '\n' was found and caret should ignore \n | |
current_line_start += 1; | |
debug << "current_line_start is " << current_line_start << "\n"; | |
} | |
const u64 caret_pos_in_line = caret_position - current_line_start; | |
debug << "caret_pos_in_line is " << caret_pos_in_line << "\n"; | |
const u64 next_line_start = current_line_end + 2; // ignore last char and \n | |
debug << "next_line_start is " << next_line_start << "\n"; | |
u64 next_line_end = text.find("\n", next_line_start); | |
if (next_line_end == std::string::npos) | |
{ | |
// if next line is the last line, there is no '\n' at the end, so we check 'find' result | |
next_line_end = text.length() - 1; | |
debug << "next_line_end is 'npos', next_line_end set to " << next_line_end << "\n"; | |
} | |
else | |
{ | |
next_line_end -= 1; // move to the last char in the line | |
debug << "next_line_end is " << next_line_end << "\n"; | |
} | |
const u64 next_line_length = next_line_end - next_line_start + 1; | |
debug << "next_line_length is " << next_line_length << "\n"; | |
// TODO : Save caret position to some kind of buffer, so after switching back and forward, caret would be on initial position | |
if (next_line_length < caret_pos_in_line) | |
{ | |
// Next line is shorter than current caret position, so caret moves to the very end of the next line | |
caret_position = next_line_end + 1; | |
debug << "next_line_length " << next_line_length << " is less than caret_pos_in_line " << | |
caret_pos_in_line << ", so caret_position is " << caret_position << "\n"; | |
} | |
else | |
{ | |
// Next line is longer than current, so caret should offset from next_line_start the exact same distance as in current line | |
caret_position = next_line_start + caret_pos_in_line; | |
debug << "next_line_length " << next_line_length << " is greater than caret_pos_in_line " << | |
caret_pos_in_line << ", so caret_position is set to " << caret_position << "\n"; | |
} | |
break; | |
} | |
} | |
return caret_position; | |
} | |
void print_state(size_t pos) | |
{ | |
static const size_t size = text.size(); | |
const auto cursor = std::min(pos * 2, text_big.size()); | |
auto textboard = text_big; | |
textboard[cursor] = '|'; | |
system("cls"); | |
std::cout << debug.str() << "\n"; | |
std::cout << "New pos = " << pos << " = "; | |
if (pos > size) std::cout << "out of bounds"; | |
else if (pos == size) std::cout << "end"; | |
else if (pos < size && text.at(pos) == '\n') std::cout << "newline"; | |
else std::cout << text.at(pos); | |
std::cout << "\n\n\n"; | |
std::cout << textboard; | |
std::cout << "\n\n\n"; | |
std::cout << "Enter Direction (wasd): "; | |
}; | |
direction get_dir(const std::string& key) | |
{ | |
if (key == "w") return direction::up; | |
if (key == "a") return direction::left; | |
if (key == "s") return direction::down; | |
if (key == "d") return direction::right; | |
return direction::invalid; | |
}; | |
int main() | |
{ | |
size_t pos = 0; | |
while (true) | |
{ | |
print_state(pos); | |
// Get new input from console | |
std::string cmd; | |
getline(std::cin, cmd); | |
// Convert input to direction | |
const auto dir = get_dir(cmd); | |
if (dir == direction::invalid) | |
continue; | |
// Get new position | |
pos = get_pos(dir, pos); | |
} | |
} |
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