Swear Oath of True Friendship

is_available = culture ?= {
	has_cultural_parameter = may_propose_best_friendship
}
trigger_if = {
	limit = {
		is_ai = yes
	}
	is_imprisoned = no
}
is_shown = scope:actor = {
	has_relation_friend = scope:recipient
}

As written in game/common/character_interactions/03_fp2_interactions.txt.

scope:actor = {
	is_available_adult = yes
}
scope:recipient = {
	is_available_adult = yes
}
custom_tooltip = {
	text = propose_best_friendship_interaction.tt.already_best_friends
	scope:actor = {
		NOT = {
			has_relation_best_friend = scope:recipient
		}
	}
}
trigger_if = {
	limit = {
		NOT = {
			scope:actor = {
				has_relation_best_friend = scope:recipient
			}
		}
	}
	custom_tooltip = {
		text = propose_best_friendship_interaction.tt.actor_has_best_friend
		scope:actor = {
			num_of_relation_best_friend = 0
		}
	}
}
trigger_if = {
	limit = {
		NOT = {
			scope:recipient = {
				has_relation_best_friend = scope:actor
			}
		}
	}
	custom_tooltip = {
		text = propose_best_friendship_interaction.tt.recipient_has_best_friend
		scope:recipient = {
			num_of_relation_best_friend = 0
		}
	}
}

As written in game/common/character_interactions/03_fp2_interactions.txt.

on_accept = scope:actor = {
	send_interface_toast = {
		type = event_toast_effect_good
		title = propose_best_friendship_interaction.accept.actor.tt
		left_icon = scope:recipient
		show_as_tooltip = {
			set_relation_best_friend = scope:recipient
		}
		reverse_add_opinion = {
			target = scope:recipient
			modifier = friendliness_opinion
			opinion = 50
		}
		if = {
			limit = {
				NOT = {
					has_hook_of_type = {
						target = scope:recipient
						type = ritual_best_friend_hook
					}
				}
				can_add_hook = {
					target = scope:recipient
					type = ritual_best_friend_hook
				}
			}
			add_hook = {
				type = ritual_best_friend_hook
				target = scope:recipient
			}
		}
	}
}
scope:recipient = {
	send_interface_toast = {
		type = event_toast_effect_neutral
		title = propose_best_friendship_interaction.accept.recipient.tt
		left_icon = scope:actor
		show_as_tooltip = {
			set_relation_best_friend = scope:actor
		}
		reverse_add_opinion = {
			target = scope:actor
			modifier = friendliness_opinion
			opinion = 50
		}
		if = {
			limit = {
				NOT = {
					has_hook_of_type = {
						target = scope:actor
						type = ritual_best_friend_hook
					}
				}
				can_add_hook = {
					target = scope:actor
					type = ritual_best_friend_hook
				}
			}
			add_hook = {
				type = ritual_best_friend_hook
				target = scope:actor
			}
		}
	}
}
hidden_effect = {
	scope:actor = {
		if = {
			limit = {
				NOT = {
					has_relation_best_friend = scope:recipient
				}
			}
			set_relation_best_friend = {
				reason = best_friend_sworn
				copy_reason = friend
				target = scope:recipient
			}
		}
	}
}
add_clan_unity_interaction_effect = {
	CHARACTER = scope:actor
	TARGET = scope:recipient
	VALUE = minor_unity_gain
	DESC = clan_unity_oath_of_true_friendship.desc
	REVERSE_NON_HOUSE_TARGET = no
}
on_decline = scope:actor = {
	send_interface_toast = {
		type = event_toast_effect_bad
		title = propose_best_friendship_interaction.decline.actor.tt
		left_icon = scope:recipient
		add_stress = medium_stress_gain
	}
}
scope:recipient = {
	send_interface_toast = {
		type = event_toast_effect_neutral
		title = propose_best_friendship_interaction.decline.recipient.tt
		left_icon = scope:actor
		scope:actor = {
			add_opinion = {
				target = scope:recipient
				modifier = hurt_opinion
				opinion = -50
			}
		}
	}
}
hidden_effect = {
	scope:recipient = {
		if = {
			limit = {
				NOT = {
					has_relation_potential_rival = scope:actor
				}
			}
			set_relation_potential_rival = scope:actor
		}
	}
}
add_clan_unity_interaction_effect = {
	CHARACTER = scope:actor
	TARGET = scope:recipient
	VALUE = minor_unity_loss
	DESC = clan_unity_declined_true_friendship.desc
	REVERSE_NON_HOUSE_TARGET = no
}

As written in game/common/character_interactions/03_fp2_interactions.txt.