bl_info = {
    "name": "Drop to Floor / Plane",
    "author": "D3rp1na",
    "version": (0, 1),
    "blender": (3, 0, 0),
    "location": "View3D > Object > Drop to Floor  (also in Object Context Menu)",
    "description": "Drops selected objects down onto Z=0, a custom height, or the nearest surface below via raycast",
    "category": "Object",
}

import bpy
import bmesh
from mathutils import Vector


def get_world_bbox_corners(obj):
    """Return the 8 bounding box corners of obj in world space."""
    return [obj.matrix_world @ Vector(c) for c in obj.bound_box]


def lowest_world_z(obj):
    """Lowest Z value of the object's bounding box in world space."""
    return min(c.z for c in get_world_bbox_corners(obj))


def lowest_point_xy(obj):
    """The (x, y) location of the bounding-box corner with the lowest Z,
    used as the raycast origin so we hit whatever is directly under the object."""
    corners = get_world_bbox_corners(obj)
    lowest = min(corners, key=lambda c: c.z)
    return lowest.x, lowest.y


class OBJECT_OT_drop_to_floor(bpy.types.Operator):
    """Drop selected objects down to Z=0, a custom height, or the surface below them"""
    bl_idname = "object.drop_to_floor"
    bl_label = "Drop to Floor"
    bl_options = {'REGISTER', 'UNDO'}

    mode: bpy.props.EnumProperty(
        name="Mode",
        items=[
            ('ZERO', "Floor (Z = 0)", "Drop objects so their lowest point touches Z=0"),
            ('CUSTOM', "Custom Height", "Drop objects so their lowest point touches a chosen Z height"),
            ('RAYCAST', "Raycast (nearest surface)", "Cast a ray straight down and land on whatever geometry is hit; falls back to the custom height if nothing is hit"),
        ],
        default='ZERO',
    )

    custom_z: bpy.props.FloatProperty(
        name="Target Z",
        description="Z height to drop onto (used for Custom mode, and as the raycast fallback)",
        default=0.0,
    )

    use_bbox_center_xy: bpy.props.BoolProperty(
        name="Raycast from bbox center (XY)",
        description="If enabled, raycast straight down from the object's horizontal bbox center instead of from directly under its lowest point",
        default=False,
    )

    def execute(self, context):
        selected = [o for o in context.selected_objects if o.type in {'MESH', 'CURVE', 'EMPTY', 'SURFACE', 'FONT'}]
        if not selected:
            self.report({'WARNING'}, "No valid objects selected")
            return {'CANCELLED'}

        depsgraph = context.evaluated_depsgraph_get()

        for obj in selected:
            current_low = lowest_world_z(obj)
            target_z = self.custom_z

            if self.mode == 'ZERO':
                target_z = 0.0

            elif self.mode == 'CUSTOM':
                target_z = self.custom_z

            elif self.mode == 'RAYCAST':
                if self.use_bbox_center_xy:
                    # average of all 8 corners' x/y
                    corners = get_world_bbox_corners(obj)
                    x = sum(c.x for c in corners) / 8.0
                    y = sum(c.y for c in corners) / 8.0
                else:
                    x, y = lowest_point_xy(obj)

                ray_origin = Vector((x, y, current_low + 10000.0))
                ray_direction = Vector((0, 0, -1))

                result, location, normal, index, hit_obj, matrix = context.scene.ray_cast(
                    depsgraph, ray_origin, ray_direction
                )

                if result and hit_obj != obj:
                    target_z = location.z
                else:
                    target_z = self.custom_z  # fallback if nothing hit

            delta_z = target_z - current_low
            obj.location.z += delta_z

        return {'FINISHED'}


def menu_func(self, context):
    self.layout.operator(OBJECT_OT_drop_to_floor.bl_idname, icon='TRIA_DOWN_BAR')


def register():
    bpy.utils.register_class(OBJECT_OT_drop_to_floor)
    bpy.types.VIEW3D_MT_object.append(menu_func)
    bpy.types.VIEW3D_MT_object_context_menu.append(menu_func)


def unregister():
    bpy.types.VIEW3D_MT_object.remove(menu_func)
    bpy.types.VIEW3D_MT_object_context_menu.remove(menu_func)
    bpy.utils.unregister_class(OBJECT_OT_drop_to_floor)


if __name__ == "__main__":
    register()