editor.cpp

#include <iostream>
#include <termios.h>
#include <unistd.h>
#include <cstdio>
#include <fstream>
#include <vector>
#include <string>
#include <cstring>
#include <sys/ioctl.h>

#define CTRL_KEY(k) ((k) & 0x1f)

struct EditorConfig {
    int cx, cy;
    int rows, cols;
    int rowoff;
    std::string filename;
    std::vector<std::string> lines;
    std::string last_query;  // last search term
    int match_line = -1;     // line where match was found (-1 = no match)
    int match_col = -1;      // column where match starts
};
EditorConfig E;

class Terminal {
public:
    Terminal() {
    tcgetattr(STDIN_FILENO, &orig_termios);
    struct termios raw = orig_termios;
    raw.c_lflag &= ~(ECHO | ICANON | ISIG);
    raw.c_iflag &= ~(IXON);  // disable Ctrl-S/Ctrl-Q flow control
    tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw);
    }
    ~Terminal() {
        tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios);
    }
private:
    struct termios orig_termios;
};

void search() {
    std::string query;
    while (true) {
        char c;
        read(STDIN_FILENO, &c, 1);
        if (c == 27) return;           // Escape = cancel
        else if (c == 10) break;       // Enter = search
        else if (c == 127) {           // Backspace
            if (!query.empty()) query.pop_back();
        } else {
            query += c;                // add character
        }
    }
    // search through lines
    for (int i = 0; i < (int)E.lines.size(); i++) {
        size_t pos = E.lines[i].find(query);
        if (pos != std::string::npos) {
            E.cy = i;
            E.cx = pos;
            E.match_line = i;
            E.match_col = pos;
            E.last_query = query;
            break;
        }
    }
}

void drawStatusBar() {
    write(STDOUT_FILENO, "\x1b[7m", 4);  // inverted colors on
    
    char status[80];
    int len = snprintf(status, sizeof(status), " %s | %d lines | L%d C%d",
        E.filename.empty() ? "[No Name]" : E.filename.c_str(),
        (int)E.lines.size(),
        E.cy + 1,
        E.cx + 1);
    
    if (len > E.cols) len = E.cols;
    write(STDOUT_FILENO, status, len);
    
    // pad the rest of the line with spaces so the bar spans full width
    for (int i = len; i < E.cols; i++)
        write(STDOUT_FILENO, " ", 1);
    
    write(STDOUT_FILENO, "\x1b[m", 3);   // inverted colors off
    write(STDOUT_FILENO, "\r\n", 2);
}

void saveFile() {
    if (E.filename.empty()) return;
    std::ofstream file(E.filename);
    for (int i = 0; i < (int)E.lines.size(); i++) {
        file << E.lines[i] << "\n";
    }
}

void loadFile(const char* filename) {
    E.filename = filename;
    std::ifstream file(filename);
    std::string line;
    while (std::getline(file, line)) {
        E.lines.push_back(line);
    }
}

void initEditor() {
    struct winsize ws;
    ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws);
    E.rows = ws.ws_row - 1;
    E.cols = ws.ws_col;
    E.cx = 0;
    E.cy = 0;
    E.rowoff = 0;
}

void scroll() {
    if (E.cy < E.rowoff)
        E.rowoff = E.cy;
    if (E.cy >= E.rowoff + E.rows)
        E.rowoff = E.cy - E.rows + 1;
}

void drawRows() {
    for (int i = 0; i < E.rows; i++) {
        int filerow = i + E.rowoff;
        if (filerow < (int)E.lines.size()) {
            int len = (int)E.lines[filerow].size();
        if (len > E.cols) len = E.cols;
    
        if (filerow == E.match_line && E.match_col < len) {
            // write before match
            int before = E.match_col;
            write(STDOUT_FILENO, E.lines[filerow].c_str(), before);
        
            // write match highlighted
            write(STDOUT_FILENO, "\x1b[7m", 4);
            int mlen = E.last_query.size();
            if ((size_t)(E.match_col + mlen) > (size_t)len) mlen = len - E.match_col;
            write(STDOUT_FILENO, E.lines[filerow].c_str() + E.match_col, mlen);
            write(STDOUT_FILENO, "\x1b[m", 3);
        
            // write after match
            write(STDOUT_FILENO, E.lines[filerow].c_str() + E.match_col + mlen, 
            len - E.match_col - mlen);
        } else {
        write(STDOUT_FILENO, E.lines[filerow].c_str(), len);
        }
        }
        else {
            write(STDOUT_FILENO, "~", 1);
        }
        write(STDOUT_FILENO, "\r\n", 2);
    }
}

void refreshScreen() {
    scroll();
    write(STDOUT_FILENO, "\x1b[2J", 4);
    write(STDOUT_FILENO, "\x1b[1;1H", 6);  // explicit row 1, col 1
    drawRows();
    drawStatusBar();
    char buf[32];
    snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cy - E.rowoff) +1, E.cx + 1);
    write(STDOUT_FILENO, buf, strlen(buf));
}

void readInput() {
    while (true) {
        refreshScreen();
        char c;
        read(STDIN_FILENO, &c, 1);

        if (c == CTRL_KEY('q')) {
            write(STDOUT_FILENO, "\x1b[2J", 4);
            write(STDOUT_FILENO, "\x1b[H", 3);
            break;
        }
        else if (c == CTRL_KEY('s')) {
            saveFile();
        }
        else if (c == CTRL_KEY('f')) {
           search();
        }
        else if (c == '\x1b') {
            char seq[2];
            read(STDIN_FILENO, &seq[0], 1);
            read(STDIN_FILENO, &seq[1], 1);
            if (seq[0] == '[') {
                switch (seq[1]) {
                    case 'A': // up
                        if (E.cy > 0) E.cy--;
                        if (E.cx > (int)E.lines[E.cy].size())
                            E.cx = E.lines[E.cy].size();
                        break;
                    case 'B': // down
                        if (E.cy < (int)E.lines.size() - 1) E.cy++;
                        if (E.cx > (int)E.lines[E.cy].size())
                            E.cx = E.lines[E.cy].size();
                        break;
                    case 'C': // right
                        if (E.cx < (int)E.lines[E.cy].size()) E.cx++;
                        break;
                    case 'D': // left
                        if (E.cx > 0) E.cx--;
                        break;
                }
            }
        }
        else if (c == 10 || c == '\r') {
            std::string rest = E.lines[E.cy].substr(E.cx);
            E.lines[E.cy] = E.lines[E.cy].substr(0, E.cx);
            E.lines.insert(E.lines.begin() + E.cy + 1, rest);
            E.cy++;
            E.cx = 0;
        }
        else if (c == 127) {
            if (E.cx > 0) {
                E.lines[E.cy].erase(E.cx - 1, 1);
                E.cx--;
            }
        }
        else if (c >= 32 && c < 127) {
            E.lines[E.cy].insert(E.cx, 1, c);
            E.cx++;
        }
    }
}

int main(int argc, char* argv[]) {
    Terminal term;
    initEditor();
    if (argc >= 2) loadFile(argv[1]);
    if (E.lines.empty()) E.lines.push_back("");  // always have at least one line
    readInput();
    return 0;
}