~こと請け合い => I guarantee ... N1
Happens next
合う => do something together N3
[合「あ」]う => To do A together/mutually N4
Secondary Verb
場合(は) => in the event of; in the case that ~ N4
~ににあわず (に似合わず ) => ~Different from N1
Evaluate
つもりだ => I thought I~; I believe I~; was planning to~; was intending to ~ N4
かな(あ) => I wonder; should I? N3
つもりだった => I thought I~; I believe I~; was planning to~; was intending to ~ N3
でしょう => perhaps, I assume, I believe N4
Speculation
~ものやら      => I wonder...; unsure; I don’t know ~ N1
...のだった => If only I...., then I would... (Regret) N2
Regret
~ものを      => But, Although, If only, I wish I had N1