@   coalesce(bgcolor, brbgcolor),
    @   event.type
    @  FROM event JOIN blob 
    @ WHERE blob.rid=event.objid
  ;
  return zBaseSql;
}

/*
** Generate a submenu element with a single parameter change.
*/
static void timeline_submenu(
  HQuery *pUrl,            /* Base URL */
  const char *zMenuName,   /* Submenu name */
  const char *zParam,      /* Parameter value to add or change */
  const char *zValue,      /* Value of the new parameter */
  const char *zRemove      /* Parameter to omit */
){
  style_submenu_element(zMenuName, zMenuName, "%s",
                        url_render(pUrl, zParam, zValue, zRemove, 0));
}

/*
** WEBPAGE: timeline
**
** Query parameters:
**
**    a=TIMESTAMP    after this date
**    b=TIMESTAMP    before this date.
**    n=COUNT        number of events in output
**    p=RID          artifact RID and up to COUNT parents and ancestors
**    d=RID          artifact RID and up to COUNT descendants
**    u=USER         only if belonging to this user
**    y=TYPE         'ci', 'w', 't'
**
** p= and d= can appear individually or together.  If either p= or d=
** appear, then u=, y=, a=, and b= are ignored.
**
** If a= and b= appear, only a= is used.  If neither appear, the most
** recent events are choosen.
**
** If n= is missing, the default count is 20.
*/
void page_timeline(void){
  Stmt q;                            /* Query used to generate the timeline */
  Blob sql;                          /* text of SQL used to generate timeline */
  Blob desc;                         /* Description of the timeline */
  int nEntry = atoi(PD("n","20"));   /* Max number of entries on timeline */
  int p_rid = atoi(PD("p","0"));     /* artifact p and its parents */
  int d_rid = atoi(PD("d","0"));     /* artifact d and its descendants */
  const char *zUser = P("u");        /* All entries by this user if not NULL */
  const char *zType = PD("y","all"); /* Type of events.  All if NULL */
  const char *zAfter = P("a");       /* Events after this time */
  const char *zBefore = P("b");      /* Events before this time */
  HQuery url;                        /* URL for various branch links */

  /* To view the timeline, must have permission to read project data.
  */
  login_check_credentials();
  if( !g.okRead ){ login_needed(); return; }

  style_header("Timeline");

                   g.zBaseURL, zUuid, zUuid);
    }else{
      blob_appendf(&desc, " of [%.10s]", zUuid);
    }
    db_prepare(&q, "SELECT * FROM timeline ORDER BY timestamp DESC");
  }else{
    int n;

    const char *zEType = "event";
    char *zDate;
    char *zNEntry = mprintf("%d", nEntry);
    url_initialize(&url, "timeline");
    url_add_parameter(&url, "n", zNEntry);
    if( zType[0]!='a' ){
      blob_appendf(&sql, " AND event.type=%Q", zType);
      url_add_parameter(&url, "y", zType);
      if( zType[0]=='c' ){
        zEType = "checkin";
      }else if( zType[0]=='w' ){
        zEType = "wiki edit";
      }else if( zType[0]=='t' ){
        zEType = "ticket change";
      }
    }
    if( zUser ){
      blob_appendf(&sql, " AND event.user=%Q", zUser);
      url_add_parameter(&url, "u", zUser);
    }
    if( zAfter ){
      while( isspace(zAfter[0]) ){ zAfter++; }
      if( zAfter[0] ){
        blob_appendf(&sql, 
           " AND event.mtime>=(SELECT julianday(%Q, 'utc'))"
           " ORDER BY event.mtime ASC", zAfter);
        url_add_parameter(&url, "a", zAfter);
        zBefore = 0;
      }else{
        zAfter = 0;
      }
    }else if( zBefore ){
      while( isspace(zBefore[0]) ){ zBefore++; }
      if( zBefore[0] ){
        blob_appendf(&sql, 
           " AND event.mtime<=(SELECT julianday(%Q, 'utc'))"
           " ORDER BY event.mtime DESC", zBefore);
        url_add_parameter(&url, "b", zBefore);
       }else{
        zBefore = 0;
      }
    }else{
      blob_appendf(&sql, " ORDER BY event.mtime DESC");
    }
    blob_appendf(&sql, " LIMIT %d", nEntry);
    db_multi_exec("%s", blob_str(&sql));

    n = db_int(0, "SELECT count(*) FROM timeline");
    if( n<nEntry && zAfter ){
      cgi_redirect(url_render(&url, "a", 0, "b", 0));
    }
    if( zAfter==0 && zBefore==0 ){
      blob_appendf(&desc, "%d most recent %ss", n, zEType);
    }else{
      blob_appendf(&desc, "%d %ss", n, zEType);
    }
    if( zUser ){
      blob_appendf(&desc, " by user %h", zUser);
    }
    if( zAfter ){
      blob_appendf(&desc, " occurring on or after %h.<br>", zAfter);
    }else if( zBefore ){
      blob_appendf(&desc, " occurring on or before %h.<br>", zBefore);
    }
    if( g.okHistory ){
      if( zAfter || n==nEntry ){
        zDate = db_text(0, "SELECT min(timestamp) FROM timeline");
        timeline_submenu(&url, "Older", "b", zDate, "a");
        free(zDate);
      }
      if( zBefore || (zAfter && n==nEntry) ){
        zDate = db_text(0, "SELECT max(timestamp) FROM timeline");
        timeline_submenu(&url, "Newer", "a", zDate, "b");
        free(zDate);
      }else{
        if( zType[0]!='a' ){
          timeline_submenu(&url, "All Types", "y", "all", 0);
        }
        if( zType[0]!='w' ){
          timeline_submenu(&url, "Wiki Only", "y", "w", 0);
        }
        if( zType[0]!='c' ){
          timeline_submenu(&url, "Checkins Only", "y", "ci", 0);
        }
        if( zType[0]!='t' ){
          timeline_submenu(&url, "Tickets Only", "y", "t", 0);
        }
      }
      if( nEntry>20 ){
        timeline_submenu(&url, "20 Events", "n", "20", 0);
      }
      if( nEntry<200 ){
        timeline_submenu(&url, "200 Events", "n", "200", 0);
      }
    }
  }
  blob_zero(&sql);
  db_prepare(&q, "SELECT * FROM timeline ORDER BY timestamp DESC");
  @ <h2>%b(&desc)</h2>
  blob_reset(&desc);