#include "cache.h"
#include "trace2/tr2_dst.h"

/*
 * If a Trace2 target cannot be opened for writing, we should issue a
 * warning to stderr, but this is very annoying if the target is a pipe
 * or socket and beyond the user's control -- especially since every
 * git command (and sub-command) will print the message.  So we silently
 * eat these warnings and just discard the trace data.
 *
 * Enable the following environment variable to see these warnings.
 */
#define TR2_ENVVAR_DST_DEBUG "GIT_TR2_DST_DEBUG"

static int tr2_dst_want_warning(void)
{
        static int tr2env_dst_debug = -1;

        if (tr2env_dst_debug == -1) {
                const char *env_value = getenv(TR2_ENVVAR_DST_DEBUG);
                if (!env_value || !*env_value)
                        tr2env_dst_debug = 0;
                else
                        tr2env_dst_debug = atoi(env_value) > 0;
        }

        return tr2env_dst_debug;
}

void tr2_dst_trace_disable(struct tr2_dst *dst)
{
        if (dst->need_close)
                close(dst->fd);
        dst->fd = 0;
        dst->initialized = 1;
        dst->need_close = 0;
}

static int tr2_dst_try_path(struct tr2_dst *dst, const char *tgt_value)
{
        int fd = open(tgt_value, O_WRONLY | O_APPEND | O_CREAT, 0666);
        if (fd == -1) {
                if (tr2_dst_want_warning())
                        warning("trace2: could not open '%s' for '%s' tracing: %s",
                                tgt_value, dst->env_var_name, strerror(errno));

                tr2_dst_trace_disable(dst);
                return 0;
        }

        dst->fd = fd;
        dst->need_close = 1;
        dst->initialized = 1;

        return dst->fd;
}

#ifndef NO_UNIX_SOCKETS
#define PREFIX_AF_UNIX "af_unix:"
#define PREFIX_AF_UNIX_STREAM "af_unix:stream:"
#define PREFIX_AF_UNIX_DGRAM "af_unix:dgram:"

static int tr2_dst_try_uds_connect(const char *path, int sock_type, int *out_fd)
{
        int fd;
        struct sockaddr_un sa;

        fd = socket(AF_UNIX, sock_type, 0);
        if (fd == -1)
                return errno;

        sa.sun_family = AF_UNIX;
        strlcpy(sa.sun_path, path, sizeof(sa.sun_path));

        if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
                int e = errno;
                close(fd);
                return e;
        }

        *out_fd = fd;
        return 0;
}

#define TR2_DST_UDS_TRY_STREAM (1 << 0)
#define TR2_DST_UDS_TRY_DGRAM  (1 << 1)

static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
                                          const char *tgt_value)
{
        unsigned int uds_try = 0;
        int fd;
        int e;
        const char *path = NULL;

        /*
         * Allow "af_unix:[<type>:]<absolute_path>"
         *
         * Trace2 always writes complete individual messages (without
         * chunking), so we can talk to either DGRAM or STREAM type sockets.
         *
         * Allow the user to explicitly request the socket type.
         *
         * If they omit the socket type, try one and then the other.
         */

        if (skip_prefix(tgt_value, PREFIX_AF_UNIX_STREAM, &path))
                uds_try |= TR2_DST_UDS_TRY_STREAM;

        else if (skip_prefix(tgt_value, PREFIX_AF_UNIX_DGRAM, &path))
                uds_try |= TR2_DST_UDS_TRY_DGRAM;

        else if (skip_prefix(tgt_value, PREFIX_AF_UNIX, &path))
                uds_try |= TR2_DST_UDS_TRY_STREAM | TR2_DST_UDS_TRY_DGRAM;

        if (!path || !*path) {
                if (tr2_dst_want_warning())
                        warning("trace2: invalid AF_UNIX value '%s' for '%s' tracing",
                                tgt_value, dst->env_var_name);

                tr2_dst_trace_disable(dst);
                return 0;
        }

        if (!is_absolute_path(path) ||
            strlen(path) >= sizeof(((struct sockaddr_un *)0)->sun_path)) {
                if (tr2_dst_want_warning())
                        warning("trace2: invalid AF_UNIX path '%s' for '%s' tracing",
                                path, dst->env_var_name);

                tr2_dst_trace_disable(dst);
                return 0;
        }

        if (uds_try & TR2_DST_UDS_TRY_STREAM) {
                e = tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd);
                if (!e)
                        goto connected;
                if (e != EPROTOTYPE)
                        goto error;
        }
        if (uds_try & TR2_DST_UDS_TRY_DGRAM) {
                e = tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd);
                if (!e)
                        goto connected;
        }

error:
        if (tr2_dst_want_warning())
                warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
                        path, dst->env_var_name, strerror(e));

        tr2_dst_trace_disable(dst);
        return 0;

connected:
        dst->fd = fd;
        dst->need_close = 1;
        dst->initialized = 1;

        return dst->fd;
}
#endif

static void tr2_dst_malformed_warning(struct tr2_dst *dst,
                                      const char *tgt_value)
{
        struct strbuf buf = STRBUF_INIT;

        strbuf_addf(&buf, "trace2: unknown value for '%s': '%s'",
                    dst->env_var_name, tgt_value);
        warning("%s", buf.buf);

        strbuf_release(&buf);
}

int tr2_dst_get_trace_fd(struct tr2_dst *dst)
{
        const char *tgt_value;

        /* don't open twice */
        if (dst->initialized)
                return dst->fd;

        dst->initialized = 1;

        tgt_value = getenv(dst->env_var_name);

        if (!tgt_value || !strcmp(tgt_value, "") || !strcmp(tgt_value, "0") ||
            !strcasecmp(tgt_value, "false")) {
                dst->fd = 0;
                return dst->fd;
        }

        if (!strcmp(tgt_value, "1") || !strcasecmp(tgt_value, "true")) {
                dst->fd = STDERR_FILENO;
                return dst->fd;
        }

        if (strlen(tgt_value) == 1 && isdigit(*tgt_value)) {
                dst->fd = atoi(tgt_value);
                return dst->fd;
        }

        if (is_absolute_path(tgt_value))
                return tr2_dst_try_path(dst, tgt_value);

#ifndef NO_UNIX_SOCKETS
        if (starts_with(tgt_value, PREFIX_AF_UNIX))
                return tr2_dst_try_unix_domain_socket(dst, tgt_value);
#endif

        /* Always warn about malformed values. */
        tr2_dst_malformed_warning(dst, tgt_value);
        tr2_dst_trace_disable(dst);
        return 0;
}

int tr2_dst_trace_want(struct tr2_dst *dst)
{
        return !!tr2_dst_get_trace_fd(dst);
}

void tr2_dst_write_line(struct tr2_dst *dst, struct strbuf *buf_line)
{
        int fd = tr2_dst_get_trace_fd(dst);

        strbuf_complete_line(buf_line); /* ensure final NL on buffer */

        /*
         * We do not use write_in_full() because we do not want
         * a short-write to try again.  We are using O_APPEND mode
         * files and the kernel handles the atomic seek+write. If
         * another thread or git process is concurrently writing to
         * this fd or file, our remainder-write may not be contiguous
         * with our initial write of this message.  And that will
         * confuse readers.  So just don't bother.
         *
         * It is assumed that TRACE2 messages are short enough that
         * the system can write them in 1 attempt and we won't see
         * a short-write.
         *
         * If we get an IO error, just close the trace dst.
         */
        if (write(fd, buf_line->buf, buf_line->len) >= 0)
                return;

        if (tr2_dst_want_warning())
                warning("unable to write trace to '%s': %s", dst->env_var_name,
                        strerror(errno));
        tr2_dst_trace_disable(dst);
}