personae/app/mutations/characters/useDeleteCharacter.js

// noinspection JSIgnoredPromiseFromCall

export const useDeleteCharacter = defineMutation(() => {
  const queryCache = useQueryCache()

  // noinspection JSUnusedLocalSymbols
  const { mutate, ...mutation } = useMutation({
    onMutate({ id, optimisticUpdates }) {
      if (optimisticUpdates) {
        // save the current character list, and options
        const oldCharacterList = queryCache.getQueryData(characterListQuery.key)

        // find the index of the deleted character
        const characterIndex = _findIndex(oldCharacterList, { id })

        let oldOptions, oldCharacter, newCharacterList

        if (characterIndex >= 0) {
          // save the options and character
          oldOptions = queryCache.getQueryData(characterOptionsQuery.key)
          oldCharacter = oldCharacterList[characterIndex]

          // create a copy of the current character list without the deleted character
          const newCharacterList = _reject(oldCharacterList || [], { id })

          // calculate new character options
          const newOptions = getCharacterOptions(newCharacterList)

          // update caches
          queryCache.setQueryData(characterListQuery.key, newCharacterList)
          queryCache.setQueryData(characterOptionsQuery.key, newOptions)

          // cancel (without refreshing) queries depending on the character
          queryCache.cancelQueries({ key: characterListQuery.key })
          queryCache.cancelQueries({ key: characterByIdQuery(id).key })
        }

        // pass the id and the old and new character lists to the other hooks
        return { oldCharacter, oldCharacterList, newCharacterList, oldOptions }
      }
    },

    mutation: ({ id, optimisticUpdates = true }) => useEmit("character:delete", id),

    onSettled(_data, _error, { id }) {
      // invalidate the queries to refetch the new data
      queryCache.invalidateQueries({ key: characterListQuery.key })
      queryCache.invalidateQueries({ key: characterByIdQuery(id).key })
    },

    onError(error, { id, optimisticUpdates }, { oldCharacter, oldCharacterList, oldOptions, newCharacterList }) {
      // before applying the rollback, check if the values in the cache are the same
      //    in case the cache was updated by another mutation or query
      if (optimisticUpdates && newCharacterList === queryCache.getQueryData(characterListQuery.key)) {
        queryCache.setQueryData(characterListQuery.key, oldCharacterList)
        queryCache.setQueryData(characterOptionsQuery.key, oldOptions)
        queryCache.setQueryData(characterByIdQuery(id).key, oldCharacter)
      }

      // handle the error
      console.error("[useDeleteCharacter] [onError]", error)
    },

    onSuccess() {}
  })

  return {
    ...mutation,
    deleteCharacter: (id) => mutate({ id, optimisticUpdates: true }),
    deleteCharacterFromEvent: (id) => mutate({ id, optimisticUpdates: false })
  }
})