  Reusing code is a common practice in software development: It helps
developers speedup the implementation task while also reducing the chances of
introducing bugs, given the assumption that the reused code has been tested,
possibly in production. Despite these benefits, opportunities for reuse are not
always in plain sight and, thus, developers may miss them. We present our
preliminary steps in building RETIWA, a recommender able to automatically
identify custom implementations in a given project that are good candidates to
be replaced by open source APIs. RETIWA relies on a ``knowledge base''
consisting of real examples of custom implementation-to-API replacements. In
this work, we present the mining strategy we tailored to automatically and
reliably extract replacements of custom implementations with APIs from open
source projects. This is the first step towards building the envisioned
recommender.

Software Engineering