#include "git-compat-util.h"

#include "hex.h"

#include "strbuf.h"

#include "trace2/tr2_tbuf.h"

#include "trace2/tr2_sid.h"

#define TR2_ENVVAR_PARENT_SID "GIT_TRACE2_PARENT_SID"

static struct strbuf tr2sid_buf = STRBUF_INIT;

static int tr2sid_nr_git_parents;

/*

 * Compute the final component of the SID representing the current process.

 * This should uniquely identify the process and be a valid filename (to

 * allow writing trace2 data to per-process files).  It should also be fixed

 * length for possible use as a database key.

 *

 * "<yyyymmdd>T<hhmmss>.<fraction>Z-<host>-<process>"

 *

 * where <host> is a 9 character string:

 *    "H<first_8_chars_of_sha1_of_hostname>"

 *    "Localhost" when no hostname.

 *

 * where <process> is a 9 character string containing the least significant

 * 32 bits in the process-id.

 *    "P<pid>"

 * (This is an abribrary choice.  On most systems pid_t is a 32 bit value,

 * so limit doesn't matter.  On larger systems, a truncated value is fine

 * for our purposes here.)

 */

static void tr2_sid_append_my_sid_component(void)

{

  const struct git_hash_algo *algo = &hash_algos[GIT_HASH_SHA1];

  struct tr2_tbuf tb_now;

  git_hash_ctx ctx;

  pid_t pid = getpid();

  unsigned char hash[GIT_MAX_RAWSZ + 1];

  char hex[GIT_MAX_HEXSZ + 1];

  char hostname[HOST_NAME_MAX + 1];

  tr2_tbuf_utc_datetime(&tb_now);

  strbuf_addstr(&tr2sid_buf, tb_now.buf);

  strbuf_addch(&tr2sid_buf, '-');

  if (xgethostname(hostname, sizeof(hostname)))

    strbuf_add(&tr2sid_buf, "Localhost", 9);

  else {

    algo->init_fn(&ctx);

    algo->update_fn(&ctx, hostname, strlen(hostname));

    algo->final_fn(hash, &ctx);

    hash_to_hex_algop_r(hex, hash, algo);

    strbuf_addch(&tr2sid_buf, 'H');

    strbuf_add(&tr2sid_buf, hex, 8);

  }

  strbuf_addf(&tr2sid_buf, "-P%08"PRIx32, (uint32_t)pid);

}

/*

 * Compute a "unique" session id (SID) for the current process.  This allows

 * all events from this process to have a single label (much like a PID).

 *

 * Export this into our environment so that all child processes inherit it.

 *

 * If we were started by another git instance, use our parent's SID as a

 * prefix.  (This lets us track parent/child relationships even if there

 * is an intermediate shell process.)

 *

 * Additionally, count the number of nested git processes.

 */

static void tr2_sid_compute(void)

{

  const char *parent_sid;

  if (tr2sid_buf.len)

    return;

  parent_sid = getenv(TR2_ENVVAR_PARENT_SID);

  if (parent_sid && *parent_sid) {

    const char *p;

    for (p = parent_sid; *p; p++)

      if (*p == '/')

        tr2sid_nr_git_parents++;

    strbuf_addstr(&tr2sid_buf, parent_sid);

    strbuf_addch(&tr2sid_buf, '/');

    tr2sid_nr_git_parents++;

  }

  tr2_sid_append_my_sid_component();

  setenv(TR2_ENVVAR_PARENT_SID, tr2sid_buf.buf, 1);

}

const char *tr2_sid_get(void)

{

  if (!tr2sid_buf.len)

    tr2_sid_compute();

  return tr2sid_buf.buf;

}

int tr2_sid_depth(void)

{

  if (!tr2sid_buf.len)

    tr2_sid_compute();

  return tr2sid_nr_git_parents;

}

void tr2_sid_release(void)

{

  strbuf_release(&tr2sid_buf);

}