feat: Thunderstore mods pagination (#122)

* feat: add basic pagination

* refactor: put paginator inside filters container

* fix: limit filter container width

* refactor: filters container is now responsive

* fix: add missing type to pagination listener parameter

* fix: don't display entire mods list while filtering mods

* refactor: filteredMods is now a computed value

* refactor: store mods per page value on UI store

* feat: user can change modsPerPage count in settings

* fix: limit mods count (min=5, max=100)

* feat: add control on pages value

When leaving settings vue, we check if the pages value is a number and is
included in the interval [5-100].
If that's not the case, we reset it to 20.

* feat: retrieve and save pages value in persistent store

* fix: don't load an empty value from persistent store on boot

* fix: cast modsPerPage to string to check if it's empty

* refactor: remove search debounce

* Update src-vue/src/plugins/store.ts

* style: add trailing comma

* fix: mention impact on TS mods only

* refactor: remove limitations on modsPerPage

* style: explicitly cast mods_per_page to number

* feat: disable pagination with modsPerPage === 0

* feat: add pagination under thunderstore mod cards

* fix: adjust bottom pagination padding

* feat: clicking bottom pagination scrolls to page top

* fix: use same containers for both paginations

* feat: do not display pagination if mods fit on one page

* style: trailing spaces

* style: trailing spaces

* feat: add a button to reset modsPerPage

* feat: add explanation text about disabling pagination

2 files changed, 154 insertions, 52 deletions

diff --git a/src-vue/src/views/SettingsView.vue b/src-vue/src/views/SettingsView.vue
index ff87c394..1c03fe4f 100644
--- a/src-vue/src/views/SettingsView.vue
+++ b/src-vue/src/views/SettingsView.vue
@@ -14,6 +14,24 @@
                         <el-button icon="Folder" @click="updateGamePath"/>
                     </template>
                 </el-input>
+
+                <!-- Thunderstore mods per page configuration -->
+                <div class="fc_parameter__panel">
+                    <h3>Number of Thunderstore mods per page</h3>
+                    <h6>
+                        This has an impact on display performances when browsing Thunderstore mods.<br>
+                        Set this value to 0 to disable pagination.
+                    </h6>
+                    <el-input 
+                        v-model="modsPerPage" 
+                        type="number"
+                    >
+                        <template #append>
+                            <el-button @click="modsPerPage = 20">Reset to default</el-button>
+                        </template>
+                    </el-input>
+                </div>
+
                 <h3>About:</h3>
                 <div class="fc_northstar__version" @click="activateDeveloperMode">
                     FlightCore Version: {{ flightcoreVersion === '' ? 'Unknown version' : `${flightcoreVersion}` }}
@@ -64,6 +82,15 @@ export default defineComponent({
                     this.$store.commit('toggleReleaseCandidate');
                 }
             }
+        },
+        modsPerPage: {
+            get(): number {
+                return this.$store.state.mods_per_page;
+            },
+            set(value: number) {
+                this.$store.state.mods_per_page = value;
+                persistentStore.set('thunderstore-mods-per-page', { value });
+            }
         }
     },
     methods: {
@@ -86,6 +113,12 @@ export default defineComponent({
     },
     mounted() {
         document.querySelector('input')!.disabled = true;
+    },
+    unmounted() {
+        if (('' + this.modsPerPage) === '') {
+            console.warn('Incorrect value for modsPerPage, resetting it to 20.');
+            this.modsPerPage = 20;
+        }
     }
 });
 </script>
@@ -110,4 +143,19 @@ h3:first-of-type {
 .el-switch {
     margin-left: 50px;
 }
+
+
+/* Parameter panel styles */
+.fc_parameter__panel {
+    margin: 30px 0;
+}
+
+.fc_parameter__panel h3 {
+    margin-bottom: 5px;
+}
+
+.fc_parameter__panel h6 {
+    margin-top: 0;
+    margin-bottom: 12px;
+}
 </style>
diff --git a/src-vue/src/views/ThunderstoreModsView.vue b/src-vue/src/views/ThunderstoreModsView.vue
index 5b74bd1c..5733d30b 100644
--- a/src-vue/src/views/ThunderstoreModsView.vue
+++ b/src-vue/src/views/ThunderstoreModsView.vue
@@ -3,7 +3,7 @@
         <div v-if="mods.length === 0" class="fc__changelog__container">
             <el-progress :show-text="false" :percentage="50" :indeterminate="true" />
         </div>
-        <el-scrollbar v-else class="container">
+        <el-scrollbar v-else class="container" ref="scrollbar">
             <div class="card-container">
                 <!-- Search filters -->
                 <div class="filter_container">
@@ -12,6 +12,16 @@
                     <div v-if="userIsTyping" class="modMessage search">
                         Searching mods...
                     </div>
+
+                    <!-- Pagination -->
+                    <el-pagination
+                        v-if="shouldDisplayPagination"
+                        :currentPage="currentPageIndex + 1"
+                        layout="prev, pager, next"
+                        :page-size="modsPerPage"
+                        :total="modsList.length"
+                        @current-change="(e: number) => currentPageIndex = e - 1"
+                    />
                 </div>
 
                 <!-- Message displayed if no mod matched searched words -->
@@ -21,16 +31,32 @@
                 </div>
 
                 <!-- Mod cards -->
-                <thunderstore-mod-card v-for="mod of modsList" v-bind:key="mod.name" :mod="mod" />
+                <thunderstore-mod-card v-for="mod of currentPageMods" v-bind:key="mod.name" :mod="mod" />
+            </div>
+
+            <!-- Bottom pagination -->
+            <div class="card-container">
+                <div class="filter_container">
+                    <el-pagination
+                        class="fc_bottom__pagination"
+                        v-if="shouldDisplayPagination"
+                        :currentPage="currentPageIndex + 1"
+                        layout="prev, pager, next"
+                        :page-size="modsPerPage"
+                        :total="modsList.length"
+                        @current-change="onBottomPaginationChange"
+                    />
+                </div>
             </div>
         </el-scrollbar>
     </div>
 </template>
 
 <script lang="ts">
-import { defineComponent } from 'vue';
+import { defineComponent, ref } from 'vue';
 import { ThunderstoreMod } from "../utils/thunderstore/ThunderstoreMod";
 import ThunderstoreModCard from "../components/ThunderstoreModCard.vue";
+import { ElScrollbar, ScrollbarInstance } from "element-plus";
 
 export default defineComponent({
     name: "ThunderstoreModsView",
@@ -42,68 +68,69 @@ export default defineComponent({
         mods(): ThunderstoreMod[] {
             return this.$store.state.thunderstoreMods;
         },
+        filteredMods(): ThunderstoreMod[] {
+            if (this.searchValue.length === 0) {
+                return this.mods;
+            }
+
+            return this.mods.filter((mod: ThunderstoreMod) => {
+                return mod.name.toLowerCase().includes(this.searchValue)
+                    || mod.owner.toLowerCase().includes(this.searchValue)
+                    || mod.versions[0].description.toLowerCase().includes(this.searchValue);
+            });
+        },
         modsList(): ThunderstoreMod[] {
-            return this.input.length === 0 || this.userIsTyping ? this.mods : this.filteredMods;
+            return this.input.length !== 0 || this.userIsTyping ? this.filteredMods : this.mods;
+        },
+        modsPerPage(): number {
+            return parseInt(this.$store.state.mods_per_page);
+        },
+        currentPageMods(): ThunderstoreMod[] {
+            // User might want to display all mods on one page.
+            const perPageValue = this.modsPerPage != 0 ? this.modsPerPage : this.modsList.length;
+
+            const startIndex = this.currentPageIndex * perPageValue;
+            const endIndexCandidate = startIndex + perPageValue;
+            const endIndex =  endIndexCandidate > this.modsList.length ? this.modsList.length : endIndexCandidate;
+            return this.modsList.slice(startIndex, endIndex);
+        },
+        shouldDisplayPagination(): boolean {
+            return this.modsPerPage != 0 && this.modsList.length > this.modsPerPage;
         }
     },
     data() {
         return {
+            // This is the model for the search input.
             input: '',
-            filteredMods: [] as ThunderstoreMod[],
+            // This is the treated value of search input
+            searchValue: '',
+
             modsBeingInstalled: [] as string[],
             userIsTyping: false,
-            debouncedSearch: this.debounce((i: string) => this.filterMods(i))
+
+            currentPageIndex: 0
         };
     },
     methods: {
         /**
-         * This is a debounced version of the filterMods method, that calls
-         * filterMods when user has stopped typing in the search bar (i.e.
-         * waits 300ms).
-         * It allows not to trigger filtering method (which is costly) each
-         * time user inputs a character.
-         */
-        onFilterTextChange (searchString: string) {
-            this.debouncedSearch(searchString);
-        },
-
-        /**
          * This method is called each time search input is modified, and
-         * filters mods matching the input string.
+         * triggered filtered mods recomputing by updating the `searchValue`
+         * variable.
          *
          * This converts research string and all researched fields to
          * lower case, to match mods regardless of font case.
          */
-        filterMods(value: string) {
-            if (value === '') {
-                this.filteredMods = [];
-                return;
-            }
-
-            const searchValue = value.toLowerCase();
-
-            this.filteredMods = this.mods.filter((mod: ThunderstoreMod) => {
-                return mod.name.toLowerCase().includes(searchValue)
-                    || mod.owner.toLowerCase().includes(searchValue)
-                    || mod.versions[0].description.toLowerCase().includes(searchValue);
-            });
+         onFilterTextChange(value: string) {
+            this.currentPageIndex = 0;
+            this.searchValue = value.toLowerCase();
         },
 
         /**
-         * This debounces a method, i.e. it prevents input method from being called
-         * multiple times in a short period of time.
-         * Stolen from https://www.freecodecamp.org/news/javascript-debounce-example/
+         * This updates current pagination and scrolls view to the top.
          */
-        debounce (func: Function, timeout = 200) {
-            let timer: any;
-            return (...args: any) => {
-                this.userIsTyping = true;
-                clearTimeout(timer);
-                timer = setTimeout(() => {
-                    this.userIsTyping = false;
-                    func.apply(this, args);
-                }, timeout);
-            };
+        onBottomPaginationChange(index: number) {
+            this.currentPageIndex = index - 1;
+            (this.$refs.scrollbar as ScrollbarInstance).scrollTo({ top: 0, behavior: 'smooth' });
         }
     }
 });
@@ -119,14 +146,6 @@ export default defineComponent({
     user-select: none !important;
 }
 
-.filter_container {
-    margin: 5px;
-}
-
-.el-input {
-    max-width: 300px;
-}
-
 .search {
     display: inline-block;
     margin: 0 0 0 10px !important;
@@ -141,6 +160,11 @@ export default defineComponent({
     margin: 0 auto;
 }
 
+.fc_bottom__pagination {
+    padding-bottom: 20px !important;
+    padding-right: 10px;
+}
+
 /* Card container dynamic size */
 @media (max-width: 1000px) {
     .card-container {
@@ -152,6 +176,11 @@ export default defineComponent({
     .card-container {
         width: 574px;
     }
+
+    .el-pagination {
+        float: none;
+        margin-top: 5px;
+    }
 }
 
 @media (max-width: 624px) {
@@ -160,10 +189,35 @@ export default defineComponent({
     }
 }
 
+.filter_container {
+    margin-bottom: 10px;
+}
+
+.el-input {
+    max-width: 200px;
+}
+
+@media (min-width: 812px) {
+    .filter_container {
+        margin: 5px auto;
+        padding: 0 5px;
+        max-width: 1000px;
+    }
+
+    .el-pagination {
+        float: right;
+        margin: 0;
+    }
+}
+
 @media (min-width: 1000px) {
     .card-container {
         width: 940px;
     }
+
+    .el-input {
+        max-width: 300px;
+    }
 }
 
 @media (min-width: 1188px) {