wedding_assign_officiant_effect

wedding_assign_officiant_effect = {
	scope:host = {
		if = {
			limit = {
				scope:host.faith.religious_head ?= {
					NOR = {
						this = scope:activity.special_guest:spouse_1
						this = scope:activity.special_guest:spouse_2
					}
				}
				scope:activity = {
					any_attending_character = {
						this = scope:host.faith.religious_head
					}
				}
			}
			scope:host.faith.religious_head = { save_scope_as = officiant }
		}
		else_if = {
			limit = {
				scope:host != scope:activity.special_guest:spouse_1
			}
			scope:host = { save_scope_as = officiant }
		}
		else_if = {
			limit = {
				scope:host.cp:councillor_court_chaplain ?= {
					NOR = {
						this = scope:activity.special_guest:spouse_1
						this = scope:activity.special_guest:spouse_2
					}
				}
				scope:activity = {
					any_attending_character = {
						this = scope:host.cp:councillor_court_chaplain
					}
				}
			}
			scope:host.cp:councillor_court_chaplain = { save_scope_as = officiant }
		}
		else_if = {
			limit = {
				NOT = { scope:host.rite = { rite_has_doctrine = doctrine_theocracy_lay_clergy } }
			}
			if = {
				limit = {
					NOT = {
						scope:activity = {
							any_attending_character = {
								is_ai = no
							}
						}
					}
					any_pool_character = {
						province = scope:activity.activity_location
						is_physically_able_ai_adult = yes
						faith = scope:host.faith
						can_be_clergy_due_to_gender_trigger = yes
					}
				}
				random_pool_character = {
					province = scope:activity.activity_location
					limit = {
						is_physically_able_ai_adult = yes
						faith = scope:host.faith
						can_be_clergy_due_to_gender_trigger = yes
					}
					save_scope_as = officiant
				}
			}
			else = {
				create_character = {
					template = priest_character_template
					dynasty = none
					location = scope:host.location
					save_scope_as = officiant
				}
			}
		}
	}
	scope:officiant ?= {
		add_character_flag = officiant
		scope:activity = {
			set_variable = {
				name = officiant
				value = scope:officiant
			}
		}
	}
}

As written in game/common/scripted_effects/04_dlc_ep2_wedding_effects.txt.