<template>
    <div class="catalog-card" v-if="Object.keys(titles).length > 0">
        <div class="catalog-card-header">
            <div>
                <span
                    ><font-awesome-icon
                        :icon="['fas', 'bars-staggered']"
                        class="catalog-icon"
                /></span>
                <span>目錄</span>
            </div>
            <span class="progress">{{ progress }}</span>
        </div>

        <div class="catalog-content">
            <div
                v-for="title in titles"
                :key="title.id"
                @click="scrollToView(title.scrollTop)"
                :class="[
                    'catalog-item',
                    currentTitle.id == title.id ? 'active' : 'not-active',
                ]"
                :style="{ marginLeft: title.level * 20 + 'px' }"
                v-show="title.isVisible"
                :title="title.rawName"
            >
                {{ title.name }}
            </div>
        </div>
    </div>
</template>

<script>
import { reactive, ref } from "vue";

export default {
    name: "KilaKilaCatalog",
    setup(props) {
        let titles = reactive(getTitles());
        let currentTitle = reactive({});
        let progress = ref(0);

        // 獲取目錄的標(biāo)題
        function getTitles() {
            let titles = [];
            let levels = ["h1", "h2", "h3"];

            let articleElement = document.querySelector(props.container);
            if (!articleElement) {
                return titles;
            }

            let elements = Array.from(articleElement.querySelectorAll("*"));

            // 調(diào)整標(biāo)簽等級
            let tagNames = new Set(
                elements.map((el) => el.tagName.toLowerCase())
            );
            for (let i = levels.length - 1; i >= 0; i--) {
                if (!tagNames.has(levels[i])) {
                    levels.splice(i, 1);
                }
            }

            let serialNumbers = levels.map(() => 0);
            for (let i = 0; i < elements.length; i++) {
                const element = elements[i];
                let tagName = element.tagName.toLowerCase();
                let level = levels.indexOf(tagName);
                if (level == -1) continue;

                let id = tagName + "-" + element.innerText + "-" + i;
                let node = {
                    id,
                    level,
                    parent: null,
                    children: [],
                    rawName: element.innerText,
                    scrollTop: element.offsetTop,
                };

                if (titles.length > 0) {
                    let lastNode = titles.at(-1);

                    // 遇到子標(biāo)題
                    if (lastNode.level < node.level) {
                        node.parent = lastNode;
                        lastNode.children.push(node);
                    }
                    // 遇到上一級標(biāo)題
                    else if (lastNode.level > node.level) {
                        serialNumbers.fill(0, level + 1);
                        let parent = lastNode.parent;
                        while (parent) {
                            if (parent.level < node.level) {
                                parent.children.push(node);
                                node.parent = parent;
                                break;
                            }
                            parent = parent.parent;
                        }
                    }
                    // 遇到平級
                    else if (lastNode.parent) {
                        node.parent = lastNode.parent;
                        lastNode.parent.children.push(node);
                    }
                }

                serialNumbers[level] += 1;
                let serialNumber = serialNumbers.slice(0, level + 1).join(".");

                node.isVisible = node.parent == null;
                node.name = serialNumber + ". " + element.innerText;
                titles.push(node);
            }

            return titles;
        }

        // 監(jiān)聽滾動事件并更新樣式
        window.addEventListener("scroll", function () {
            progress.value =
                parseInt(
                    (window.scrollY / document.documentElement.scrollHeight) *
                        100
                ) + "%";

            let visibleTitles = [];

            for (let i = titles.length - 1; i >= 0; i--) {
                const title = titles[i];
                if (title.scrollTop <= window.scrollY) {
                    if (currentTitle.id === title.id) return;

                    Object.assign(currentTitle, title);

                    // 展開節(jié)點
                    setChildrenVisible(title, true);
                    visibleTitles.push(title);

                    // 展開父節(jié)點
                    let parent = title.parent;
                    while (parent) {
                        setChildrenVisible(parent, true);
                        visibleTitles.push(parent);
                        parent = parent.parent;
                    }

                    // 折疊其余節(jié)點
                    for (const t of titles) {
                        if (!visibleTitles.includes(t)) {
                            setChildrenVisible(t, false);
                        }
                    }

                    return;
                }
            }
        });

        // 設(shè)置子節(jié)點的可見性
        function setChildrenVisible(title, isVisible) {
            for (const child of title.children) {
                child.isVisible = isVisible;
            }
        }

        // 滾動到指定的位置
        function scrollToView(scrollTop) {
            window.scrollTo({ top: scrollTop, behavior: "smooth" });
        }

        return { titles, currentTitle, progress, scrollToView };
    },
    props: {
        container: {
            type: String,
            default: ".post-body .article-content",
        },
    },
};
</script>

<style lang="less" scoped>
.catalog-card {
    background: white;
    border-radius: 8px;
    box-shadow: 0 3px 8px 6px rgba(7, 17, 27, 0.05);
    padding: 20px 24px;
    width: 100%;
    margin-top: 25px;
    box-sizing: border-box;
}

.catalog-card-header {
    text-align: left !important;
    margin-bottom: 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.catalog-icon {
    font-size: 18px;
    margin-right: 10px;
    color: dodgerblue;
}

.catalog-card-header div > span {
    font-size: 17px;
    color: #4c4948;
}

.progress {
    color: #a9a9a9;
    font-style: italic;
    font-size: 140%;
}

.catalog-content {
    max-height: calc(100vh - 120px);
    overflow: auto;
    margin-right: -24px;
    padding-right: 20px;
}

.catalog-item {
    color: #666261;
    margin: 5px 0;
    line-height: 28px;
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    font-size: 14px;
    padding: 2px 6px;
    display: -webkit-box;
    overflow: hidden;
    text-overflow: ellipsis;
    -webkit-line-clamp: 1;
    -webkit-box-orient: vertical;

    &:hover {
        color: #1892ff;
    }
}

.active {
    background-color: #;
    color: white;

    &:hover {
        background-color: #0c82e9;
        color: white;
    }
}
</style>