func checkToolsAvailability(cfg *config.Config, finder toolsFinder) (version.Number, error) {
currentVersion, ok := cfg.AgentVersion()
if !ok || currentVersion == version.Zero {
return version.Zero, nil
}
env, err := newEnvirons(cfg)
if err != nil {
return version.Zero, errors.Annotatef(err, "cannot make environ")
}
// finder receives major and minor as parameters as it uses them to filter versions and
// only return patches for the passed major.minor (from major.minor.patch).
// We'll try the released stream first, then fall back to the current configured stream
// if no released tools are found.
vers, err := finder(env, currentVersion.Major, currentVersion.Minor, tools.ReleasedStream, coretools.Filter{})
preferredStream := tools.PreferredStream(¤tVersion, cfg.Development(), cfg.AgentStream())
if preferredStream != tools.ReleasedStream && errors.Cause(err) == coretools.ErrNoMatches {
vers, err = finder(env, currentVersion.Major, currentVersion.Minor, preferredStream, coretools.Filter{})
}
if err != nil {
return version.Zero, errors.Annotatef(err, "cannot find available tools")
}
// Newest also returns a list of the items in this list matching with the
// newest version.
newest, _ := vers.Newest()
return newest, nil
}