/* qmp.c — AF_UNIX QMP client: connect + capability handshake, line-based recv
 * with a poll timeout, and synchronous command execution. */

#include "qmp.h"

#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <poll.h>

#define QMP_TIMEOUT_MS 5000
#define QMP_BUF_SIZE   4096

struct qmp_conn {
    int fd;
};

static int recv_line(int fd, char* buf, size_t cap) {
    size_t n = 0;
    while (n + 1 < cap) {
        struct pollfd pfd = { .fd = fd, .events = POLLIN };
        if (poll(&pfd, 1, QMP_TIMEOUT_MS) <= 0) return -1;
        char c;
        if (read(fd, &c, 1) != 1) return -1;
        buf[n++] = c;
        if (c == '\n') break;
    }
    buf[n] = '\0';
    return (int)n;
}

static int send_all(int fd, const char* s, size_t len) {
    while (len > 0) {
        ssize_t w = write(fd, s, len);
        if (w <= 0) return -1;
        s += w;
        len -= (size_t)w;
    }
    return 0;
}

qmp_conn* qmp_connect(const char* sock_path) {
    int fd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (fd < 0) return NULL;

    struct sockaddr_un addr;
    memset(&addr, 0, sizeof addr);
    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, sock_path, sizeof addr.sun_path - 1);

    if (connect(fd, (struct sockaddr*)&addr, sizeof addr) < 0) {
        close(fd);
        return NULL;
    }

    char buf[QMP_BUF_SIZE];
    if (recv_line(fd, buf, sizeof buf) < 0) {
        close(fd);
        return NULL;
    }

    const char* cap_cmd = "{\"execute\":\"qmp_capabilities\"}\r\n";
    if (send_all(fd, cap_cmd, strlen(cap_cmd)) < 0) {
        close(fd);
        return NULL;
    }

    if (recv_line(fd, buf, sizeof buf) < 0) {
        close(fd);
        return NULL;
    }

    qmp_conn* c = malloc(sizeof *c);
    if (!c) {
        close(fd);
        return NULL;
    }
    c->fd = fd;
    return c;
}

void qmp_disconnect(qmp_conn* c) {
    if (!c) return;
    close(c->fd);
    free(c);
}

int qmp_exec(qmp_conn* c, const char* cmd, char* resp, size_t cap) {
    size_t cmdlen = strlen(cmd);
    if (send_all(c->fd, cmd, cmdlen) < 0) return -1;
    if (send_all(c->fd, "\r\n", 2) < 0) return -1;

    char line[QMP_BUF_SIZE];
    for (;;) {
        if (recv_line(c->fd, line, sizeof line) < 0) return -1;
        if (strstr(line, "\"return\"")) {
            if (resp && cap > 0) {
                strncpy(resp, line, cap - 1);
                resp[cap - 1] = '\0';
            }
            return 0;
        }
        if (strstr(line, "\"error\"")) {
            if (resp && cap > 0) {
                strncpy(resp, line, cap - 1);
                resp[cap - 1] = '\0';
            }
            return -1;
        }
    }
}