In　this　paper,　we　extend　the　classical　Melnikov　method　for　smooth　systems　to　a　class　of　planar　hybrid　piecewise-smooth　system　subjected　to　a　time-periodic　perturbation.　In　this　class,　we　suppose　there　exists　a　switching　manifold　with　a　more　general　form　such　that　the　plane　is　divided　into　two　zones,　and　the　dynamics　in　each　zone　is　governed　by　a　smooth　system.　Furthermore,　we　assume　that　the　unperturbed　system　is　a　general　planar　piecewise-smooth　system　with　non-zero　trace　and　possesses　a　piecewise-smooth　homoclinic　orbit　transversally　crossing　the　switching　manifold.　We　also　define　a　reset　map　to　describe　the　instantaneous　impact　rule　on　the　switching　manifold　when　a　trajectory　arrives　at　the　switching　manifold.　Through　a　series　of　geometrical　analysis　and　perturbation　techniques,　we　obtain　a　Melnikov-type　function　to　measure　the　separation　of　the　unstable　manifold　and　stable　manifold　under　the　effect　of　the　time-periodic　perturbations　and　the　reset　map.　Finally,　we　use　the　presented　Melnikov　function　to　study　global　bifurcations　and　chaotic　dynamics　for　a　concrete　planar　piecewise-linear　oscillator.