Implement+test postsFilter

I think it's much cleaner to have just the filter object in the store
and to implement convenience methods to safely update the filter object.

webapp/store/postsFilter.js

@@ -0,0 +1,50 @@
+import get from 'lodash/get'
+import update from 'lodash/update'
+import xor from 'lodash/xor'
+import isEmpty from 'lodash/isEmpty'
+import clone from 'lodash/clone'
+
+export const state = () => {
+  return {
+    filter: {},
+  }
+}
+
+export const mutations = {
+  TOGGLE_FILTER_BY_FOLLOWED(state, currentUserId) {
+    const filter = clone(state.filter)
+    const id = get(filter, 'author.followedBy_some.id')
+    if (id) {
+      delete filter.author
+      state.filter = filter
+    } else {
+      state.filter = {
+        ...filter,
+        author: { followedBy_some: { id: currentUserId } },
+      }
+    }
+  },
+  RESET_CATEGORIES(state) {
+    const filter = clone(state.filter)
+    delete filter.categories_some
+    state.filter = filter
+  },
+  TOGGLE_CATEGORY(state, categoryId) {
+    const filter = clone(state.filter)
+    update(filter, 'categories_some.id_in', categoryIds => xor(categoryIds, [categoryId]))
+    if (isEmpty(get(filter, 'categories_some.id_in'))) delete filter.categories_some
+    state.filter = filter
+  },
+}
+
+export const getters = {
+  postsFilter(state) {
+    return state.filter
+  },
+  filteredCategoryIds(state) {
+    return get(state.filter, 'categories_some.id_in') || []
+  },
+  filteredByUsersFollowed(state) {
+    return !!get(state.filter, 'author.followedBy_some.id')
+  },
+}

webapp/store/postsFilter.spec.js

@@ -0,0 +1,126 @@
+import { getters, mutations } from './postsFilter.js'
+
+let state
+let testAction
+
+describe('getters', () => {
+  describe('filteredCategoryIds', () => {
+    it('returns category ids if filter is set', () => {
+      state = { filter: { categories_some: { id_in: [24] } } }
+      expect(getters.filteredCategoryIds(state)).toEqual([24])
+    })
+
+    it('returns empty array if filter is not set', () => {
+      state = { filter: { author: { followedBy_some: { id: 7 } } } }
+      expect(getters.filteredCategoryIds(state)).toEqual([])
+    })
+  })
+
+  describe('postsFilter', () => {
+    it('returns filter', () => {
+      state = { filter: { author: { followedBy_some: { id: 7 } } } }
+      expect(getters.postsFilter(state)).toEqual({ author: { followedBy_some: { id: 7 } } })
+    })
+  })
+
+  describe('filteredByUsersFollowed', () => {
+    it('returns true if filter is set', () => {
+      state = { filter: { author: { followedBy_some: { id: 7 } } } }
+      expect(getters.filteredByUsersFollowed(state)).toBe(true)
+    })
+
+    it('returns false if filter is not set', () => {
+      state = { filter: { categories_some: { id_in: [23] } } }
+      expect(getters.filteredByUsersFollowed(state)).toBe(false)
+    })
+  })
+})
+
+describe('mutations', () => {
+  describe('RESET_CATEGORIES', () => {
+    beforeEach(() => {
+      testAction = categoryId => {
+        mutations.RESET_CATEGORIES(state, categoryId)
+        return getters.postsFilter(state)
+      }
+    })
+    it('resets the categories filter', () => {
+      state = {
+        filter: {
+          author: { followedBy_some: { id: 7 } },
+          categories_some: { id_in: [23] },
+        },
+      }
+      expect(testAction(23)).toEqual({ author: { followedBy_some: { id: 7 } } })
+    })
+  })
+
+  describe('TOGGLE_CATEGORY', () => {
+    beforeEach(() => {
+      testAction = categoryId => {
+        mutations.TOGGLE_CATEGORY(state, categoryId)
+        return getters.postsFilter(state)
+      }
+    })
+
+    it('creates category filter if empty', () => {
+      state = { filter: {} }
+      expect(testAction(23)).toEqual({ categories_some: { id_in: [23] } })
+    })
+
+    it('adds category id not present', () => {
+      state = { filter: { categories_some: { id_in: [24] } } }
+      expect(testAction(23)).toEqual({ categories_some: { id_in: [24, 23] } })
+    })
+
+    it('removes category id if present', () => {
+      state = { filter: { categories_some: { id_in: [23, 24] } } }
+      const result = testAction(23)
+      expect(result).toEqual({ categories_some: { id_in: [24] } })
+    })
+
+    it('removes category filter if empty', () => {
+      state = { filter: { categories_some: { id_in: [23] } } }
+      expect(testAction(23)).toEqual({})
+    })
+
+    it('does not get in the way of other filters', () => {
+      state = {
+        filter: {
+          author: { followedBy_some: { id: 7 } },
+          categories_some: { id_in: [23] },
+        },
+      }
+      expect(testAction(23)).toEqual({ author: { followedBy_some: { id: 7 } } })
+    })
+  })
+
+  describe('TOGGLE_FILTER_BY_FOLLOWED', () => {
+    beforeEach(() => {
+      testAction = userId => {
+        mutations.TOGGLE_FILTER_BY_FOLLOWED(state, userId)
+        return getters.postsFilter(state)
+      }
+    })
+
+    describe('given empty filter', () => {
+      beforeEach(() => {
+        state = { filter: {} }
+      })
+
+      it('attaches the id of the current user to the filter object', () => {
+        expect(testAction(4711)).toEqual({ author: { followedBy_some: { id: 4711 } } })
+      })
+    })
+
+    describe('already filtered', () => {
+      beforeEach(() => {
+        state = { filter: { author: { followedBy_some: { id: 4711 } } } }
+      })
+
+      it('remove the id of the current user from the filter object', () => {
+        expect(testAction(4711)).toEqual({})
+      })
+    })
+  })
+})