ccore/src/ReadLine.c

#include "core/ReadLine.h"

#include <ctype.h>
#include <errno.h>
#include <stdatomic.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <threads.h>
#include <unistd.h>

#include "ErrorSimulator.h"
#include "core/Logger.h"
#include "core/Queue.h"

#define HISTORY_LENGTH 10
#define CONSOLE_BUFFER_SIZE 256

typedef struct ConsoleLine {
    char data[CONSOLE_BUFFER_SIZE];
    int length;
} ConsoleLine;

static atomic_bool running = true;
static thrd_t readThread = {0};

static struct termios original;
static CoreQueue buffer = {0};
static ConsoleLine currentBuffer = {0};
static int move = 0;
static int cursorMove = 0;
static mtx_t bufferMutex = {0};

static ConsoleLine history[HISTORY_LENGTH];
static int historyOffset = 0;
static int historyIndex = 0;
static int historyLength = 0;

static void getAttributes(struct termios* t) {
    if(tcgetattr(STDIN_FILENO, t)) {
        CORE_LOG_WARNING("cannot get terminal attributes");
    }
}

static void restoreAttributes() {
    if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &original)) {
        CORE_LOG_WARNING("cannot restore terminal attributes: %s",
                         strerror(errno));
    }
}

static char readChar() {
    char c = 0;
    ssize_t bytes = read(STDIN_FILENO, &c, 1);
    return bytes <= 0 ? '\0' : c;
}

static void addChar(char c) {
    if(currentBuffer.length >= CONSOLE_BUFFER_SIZE - 1) {
        return;
    }
    for(int i = 0; i < move; i++) {
        currentBuffer.data[currentBuffer.length - i] =
            currentBuffer.data[currentBuffer.length - i - 1];
    }
    currentBuffer.length++;
    currentBuffer.data[currentBuffer.length - move - 1] = c;
    currentBuffer.data[currentBuffer.length] = '\0';
}

static void print(const char* s) {
    fputs(s, stdout);
}

static void refreshLine(const char* prefix) {
    print(prefix);
    print(currentBuffer.data);
    if(cursorMove > 0) {
        printf("\33[%dD", cursorMove);
    }
    fflush(stdout);
    print("\33[2K\r");
}

static bool clear() {
    move = 0;
    cursorMove = 0;
    currentBuffer.length = 0;
    currentBuffer.data[0] = '\0';
    historyOffset = 0;
    return false;
}

static void addToHistory() {
    if(historyLength < HISTORY_LENGTH) {
        historyLength++;
    }
    history[historyIndex] = currentBuffer;
    historyIndex = (historyIndex + 1) % HISTORY_LENGTH;
}

static void lock() {
    if(mtx_lock(&bufferMutex) != thrd_success || MUTEX_LOCK_FAIL) {
        CORE_LOG_WARNING("could not lock buffer mutex");
    }
}

static void unlock() {
    if(mtx_unlock(&bufferMutex) != thrd_success || MUTEX_UNLOCK_FAIL) {
        CORE_LOG_WARNING("could not unlock buffer mutex");
    }
}

static void addLine() {
    addToHistory();
    lock();
    corePushQueueData(&buffer, &currentBuffer);
    unlock();
    clear();
}

static char isUTF8Part(char c) {
    return ((uint8_t)c & 0xC0) == 0x80;
}

static bool removeChar() {
    int pos = currentBuffer.length - move;
    if(pos > 0) {
        int l = 1;
        while(pos - l >= 0) {
            if(!isUTF8Part(currentBuffer.data[pos - l])) {
                break;
            }
            l++;
        }
        currentBuffer.length -= l;
        for(int i = pos - l; i <= currentBuffer.length; i++) {
            currentBuffer.data[i] = currentBuffer.data[i + l];
        }
    }
    return false;
}

static bool handleControlKey(char c) {
    switch(c) {
        case 3: return clear();
        case 10:
        case 13: return true;
        case 127: return removeChar();
    }
    return false;
}

static void copyHistory() {
    currentBuffer = history[(historyIndex - historyOffset + HISTORY_LENGTH) %
                            HISTORY_LENGTH];
    move = 0;
    cursorMove = 0;
}

static void handleUpArrow() {
    if(historyOffset >= historyLength) {
        return;
    }
    historyOffset++;
    copyHistory();
}

static void handleDownArrow() {
    if(historyOffset <= 1) {
        return;
    }
    historyOffset--;
    copyHistory();
}

static char getMoved() {
    return currentBuffer.data[currentBuffer.length - move];
}

static void handleLeftArrow() {
    if(move < currentBuffer.length) {
        move++;
        while(move < currentBuffer.length && isUTF8Part(getMoved())) {
            move++;
        }
        cursorMove++;
    }
}

static void handleRightArrow() {
    if(move > 0) {
        move--;
        while(move > 0 && isUTF8Part(getMoved())) {
            move--;
        }
        cursorMove--;
    }
}

static void readEscapeSequence() {
    if(readChar() != '[') {
        return;
    }
    switch(readChar()) {
        case 'A': handleUpArrow(); break;
        case 'B': handleDownArrow(); break;
        case 'C': handleRightArrow(); break;
        case 'D': handleLeftArrow(); break;
        case '3':
            if(readChar() == '~' && move > 0) {
                handleRightArrow();
                removeChar();
            }
            break;
    }
}

static void handleChars() {
    while(true) {
        char c = readChar();
        if(c == 0) {
            break;
        } else if(c == 27) {
            readEscapeSequence();
        } else if(iscntrl(c)) {
            if(handleControlKey(c)) {
                addLine();
                return;
            }
        } else {
            addChar(c);
        }
    }
}

static int loop(void* data) {
    (void)data;
    while(running) {
        handleChars();
        refreshLine("wusi> ");
        struct timespec t = {.tv_nsec = 1000000};
        thrd_sleep(&t, nullptr);
    }
    return 0;
}

bool coreStartReadLine(void) {
    // https://viewsourcecode.org/snaptoken/kilo/02.enteringRawMode.html
    getAttributes(&original);
    struct termios raw = original;
    raw.c_iflag &= ~(tcflag_t)(ICRNL | IXON);
    raw.c_lflag &= ~(tcflag_t)(ECHO | ICANON | IEXTEN | ISIG);
    raw.c_cc[VMIN] = 0;
    raw.c_cc[VTIME] = 0;

    if(tcsetattr(STDIN_FILENO, TCSANOW, &raw)) {
        CORE_LOG_WARNING("cannot set terminal attributes");
    }

    coreInitQueue(&buffer, 10, sizeof(ConsoleLine));
    atomic_store(&running, true);
    if(MUTEX_INIT_FAIL || mtx_init(&bufferMutex, mtx_plain) != thrd_success) {
        CORE_LOG_ERROR("cannot init buffer mutex");
        coreStopReadLine();
        return true;
    } else if(THREAD_INIT_FAIL ||
              thrd_create(&readThread, loop, nullptr) != thrd_success) {
        CORE_LOG_ERROR("cannot start read thread");
        coreStopReadLine();
        return true;
    }
    return false;
}

bool coreReadLine(char* buffer_, size_t n) {
    if(buffer.length == 0) {
        return false;
    }
    lock();
    ConsoleLine* line = coreGetQueueIndex(&buffer, 0);
    snprintf(buffer_, n, "%s", line->data);
    corePopQueueData(&buffer);
    unlock();
    return true;
}

void coreStopReadLine() {
    atomic_store(&running, false);
    thrd_join(readThread, nullptr);
    restoreAttributes();
    coreDestroyQueue(&buffer);
    mtx_destroy(&bufferMutex);
}