/*!
 * x-scrollbar 自定义滚动条插件
 * 版本: v3.1.0
 * 作者: 清晨的阳光(QQ:765550360)
 * 许可: MIT
 * https://gitee.com/xujz520/x-scrollbar
 */

import './index.css'

class XScrollbar {
    constructor(dom, options) {
        this.$dom = dom
        if (this.$dom.classList.contains('x-scrollbar')) return
        this.$dom.classList.add('x-scrollbar')

        // 移动端检测
        this.isMobile = window.navigator.userAgent.toLowerCase().indexOf('mobile') != -1

        // 合并配置
        let defaultOptions = {
            // 响应容器和内容大小改变(自动更新滚动条)
            autoUpdate: true,
            // 阻止向上传递滚动事件
            preventDefault: true,
            // 仅水平滚动(拨动鼠标滚轮时将作用于X轴)
            onlyHorizontal: false,
            // 自动隐藏
            autoHide: true,
        }
        let defaultStyle = {
            // 滑块大小
            thumbSize: '5px',
            // 轨道颜色
            trackBackground: '#ddd',
            // 滑块颜色
            thumbBackground: '#5f5f5f',
            // 滑块圆角大小
            thumbRadius: '5px',
        }
        Object.assign(this, defaultOptions, defaultStyle, options)

        // 构造dom
        let scrollLeft = this.$dom.scrollLeft
        let scrollTop = this.$dom.scrollTop
        this.$container = this.html2dom('<div class="x-scrollbar__container"></div>')
        this.$content = this.html2dom('<div class="x-scrollbar__content"></div>')
        this.$trackX = this.html2dom('<div class="x-scrollbar__track-x"></div>')
        this.$trackY = this.html2dom('<div class="x-scrollbar__track-y"></div>')
        this.$thumbX = this.html2dom('<div class="x-scrollbar__thumb-x"></div>')
        this.$thumbY = this.html2dom('<div class="x-scrollbar__thumb-y"></div>')
        this.$trackX.appendChild(this.$thumbX)
        this.$trackY.appendChild(this.$thumbY)
        let childNodes = []
        Array.prototype.forEach.call(this.$dom.childNodes, function (node) {
            childNodes.push(node)
        })
        childNodes.forEach(
            function (node) {
                this.$content.appendChild(node)
            }.bind(this)
        )
        this.$container.appendChild(this.$content)
        this.$dom.appendChild(this.$container)

        // 处理内边距
        let styleObj = getComputedStyle(this.$dom)
        let padding = `${styleObj.paddingTop} ${styleObj.paddingRight} ${styleObj.paddingBottom} ${styleObj.paddingLeft}`
        if (padding != '0px 0px 0px 0px') {
            this.$dom.style.padding = '0px 0px 0px 0px'
            this.$container.style.padding = padding
        }

        // 设置初始值
        this.$container.scrollLeft = scrollLeft
        this.$container.scrollTop = scrollTop

        if (this.preventDefault) {
            this.$container.classList.add('x-scrollbar__container--preventDefault')
        }

        if (this.isMobile) return

        this.$dom.appendChild(this.$trackX)
        this.$dom.appendChild(this.$trackY)
        this.$container.classList.add('x-scrollbar__container--hideScrollbar')
        if (JSON.stringify(defaultStyle) != JSON.stringify(Object.keys(defaultStyle).reduce((obj, k) => ({ ...obj, [k]: this[k] }), {}))) {
            this.style()
        }

        // 自动隐藏
        if (!this.autoHide) this.$dom.classList.add('x-scrollbar-keep')

        // 绑定事件
        this.bindScroll()
        this.bindDrag()
        if (this.onlyHorizontal) {
            this.bindWheel()
        }

        // 响应容器和内容大小改变
        if (this.autoUpdate) {
            // 首次自动触发
            this.resizeObserver()
        } else {
            this.update()
        }
    }

    /**
     * 设置滑块大小
     */
    setThumbSize() {
        // (clientWidth / scrollWidth) = (滑块大小 / clientWidth)
        // 最大滑动距离 = clientWidth - 滑块大小
        // 最大滚动距离 = scrollWidth - clientWidth
        // (滑动距离 / 最大滑动距离) = (滚动距离 / 最大滚动距离)

        // 容器大小
        this.clientWidth = this.$container.clientWidth
        this.clientHeight = this.$container.clientHeight
        // 内容大小
        this.scrollWidth = this.$container.scrollWidth
        this.scrollHeight = this.$container.scrollHeight
        //是否存在滚动条
        this.hasXScrollbar = this.scrollWidth > this.clientWidth
        this.hasYScrollbar = this.scrollHeight > this.clientHeight
        //滑块大小
        this.thumbXWidth = Math.max((this.clientWidth / this.scrollWidth) * this.clientWidth, 30)
        this.thumbYHeight = Math.max((this.clientHeight / this.scrollHeight) * this.clientHeight, 30)
        //最大滑动距离
        this.thumbXMaxLeft = this.clientWidth - this.thumbXWidth
        this.thumbYMaxTop = this.clientHeight - this.thumbYHeight
        //最大滚动距离
        this.maxScrollLeft = this.scrollWidth - this.clientWidth
        this.maxScrollTop = this.scrollHeight - this.clientHeight

        this.$trackX.style.display = this.hasXScrollbar ? 'block' : 'none'
        this.$trackY.style.display = this.hasYScrollbar ? 'block' : 'none'
        this.$thumbX.style.width = this.thumbXWidth + 'px'
        this.$thumbY.style.height = this.thumbYHeight + 'px'
    }

    /**
     * 拖动事件
     */
    bindDrag() {
        // 上一次的拖动位置
        let screenX = null
        let screenY = null

        this.$thumbX.addEventListener('mousedown', e => {
            this.$trackX.classList.add('x-scrollbar__track--draging')
            this.thumbXActive = true
            screenX = e.screenX
        })

        this.$thumbY.addEventListener('mousedown', e => {
            this.$trackY.classList.add('x-scrollbar__track--draging')
            this.thumbYActive = true
            screenY = e.screenY
        })

        document.addEventListener('mouseup', e => {
            this.$trackX.classList.remove('x-scrollbar__track--draging')
            this.$trackY.classList.remove('x-scrollbar__track--draging')
            this.thumbXActive = false
            this.thumbYActive = false
        })

        document.addEventListener('mousemove', e => {
            if (!(this.thumbXActive || this.thumbYActive)) return
            e.preventDefault()

            requestAnimationFrame(() => {
                if (this.thumbXActive) {
                    let offset = e.screenX - screenX
                    screenX = e.screenX
                    let left = Math.max(Math.min(parseFloat(this.$thumbX.style.left || 0) + offset, this.thumbXMaxLeft), 0)
                    this.$thumbX.style.left = left + 'px'
                    this.$container.scrollLeft = (left / this.thumbXMaxLeft) * this.maxScrollLeft
                } else {
                    let offset = e.screenY - screenY
                    screenY = e.screenY
                    let top = Math.max(Math.min(parseFloat(this.$thumbY.style.top || 0) + offset, this.thumbYMaxTop), 0)
                    this.$thumbY.style.top = top + 'px'
                    this.$container.scrollTop = (top / this.thumbYMaxTop) * this.maxScrollTop
                }
            })
        })
    }

    /**
     * 仅水平滚动(拨动鼠标滚轮时将作用于X轴)
     */
    bindWheel() {
        let easeout = (start, end) => {
            if (Math.abs(end - start) <= 1) return end
            return start + (end - start) / 4
        }

        this.$container.addEventListener('wheel', e => {
            // 仅响应 y 滚动 => 作用于 x
            if (!this.hasXScrollbar) return
            if (e.deltaY && !e.shiftKey) {
                // 结束值
                this.scrollLeft = Math.max(Math.min((this.scrollLeft || this.$container.scrollLeft) + (e.deltaY > 0 ? 100 : -100), this.maxScrollLeft), 0)
                this.left = (this.scrollLeft / this.maxScrollLeft) * this.thumbXMaxLeft

                // 阻止向上传递 || !(终点)
                if (this.preventDefault || !(this.scrollLeft == 0 || this.scrollLeft == this.maxScrollLeft)) {
                    e.preventDefault()
                    e.stopPropagation()
                }

                if (this.reqId) return

                // 起始值
                let scrollLeft = this.$container.scrollLeft
                let left = parseFloat(this.$thumbX.style.left || 0)

                let animate = () => {
                    scrollLeft = easeout(scrollLeft, this.scrollLeft)
                    left = easeout(left, this.left)
                    this.$container.scrollLeft = scrollLeft
                    this.$thumbX.style.left = left + 'px'
                    this.innerScroll = true
                    if (scrollLeft != this.scrollLeft) {
                        this.reqId = requestAnimationFrame(animate)
                    } else {
                        this.reqId = null
                        this.scrollLeft = null
                        requestAnimationFrame(() => (this.innerScroll = false))
                    }
                }
                animate()
            }
        })
    }

    /**
     * 滚动事件 => 修正滑块位置
     */
    bindScroll() {
        this.$container.addEventListener('scroll', () => {
            if (this.thumbXActive || this.thumbYActive || this.innerScroll) return
            if (this.hasXScrollbar) {
                this.$thumbX.style.left = (this.$container.scrollLeft / this.maxScrollLeft) * this.thumbXMaxLeft + 'px'
            }
            if (this.hasYScrollbar) {
                this.$thumbY.style.top = (this.$container.scrollTop / this.maxScrollTop) * this.thumbYMaxTop + 'px'
            }
        })
    }

    /**
     * 观察容器大小
     */
    resizeObserver() {
        this.$resizeObserver = new ResizeObserver(entries => {
            let contentRect = entries[0].contentRect
            if (!(contentRect.width || contentRect.height)) return
            this.update()
        })
        this.$resizeObserver.observe(this.$container)
        this.$resizeObserver.observe(this.$content)
    }

    /**
     * 使用滚动值修正滑块
     * 在 容器大小 或 内容大小 发生改变时调用
     */
    update() {
        this.setThumbSize()
        if (this.hasXScrollbar) {
            this.$thumbX.style.left = (this.$container.scrollLeft / this.maxScrollLeft) * this.thumbXMaxLeft + 'px'
        }
        if (this.hasYScrollbar) {
            this.$thumbY.style.top = (this.$container.scrollTop / this.maxScrollTop) * this.thumbYMaxTop + 'px'
        }
    }

    /**
     * html字符串 转 dom对象
     * @param {*} html
     * @returns
     */
    html2dom(html) {
        let element = document.createElement('div')
        element.innerHTML = html
        let children = element.children
        if (children.length <= 1) {
            return children[0]
        } else {
            return children
        }
    }

    /**
     * 生成自定义样式
     */
    style() {
        let content = `
  /* 轨道 */
  .x-scrollbar__track-x {
    height: ${parseInt(this.thumbSize) * 2 + 4}px;
  }
  
  .x-scrollbar__track-y {
    width: ${parseInt(this.thumbSize) * 2 + 4}px;
  }
  
  /* 滑块 */
  .x-scrollbar__track-x > .x-scrollbar__thumb-x,
  .x-scrollbar__track-y > .x-scrollbar__thumb-y {
    background: ${this.thumbBackground};
    border-radius: ${parseInt(this.thumbRadius || 0) != 5 ? parseInt(this.thumbRadius || 0) : parseInt(this.thumbSize)}px;
  }
  
  .x-scrollbar__track-x > .x-scrollbar__thumb-x {
    height: ${parseInt(this.thumbSize)}px;
  }
  
  .x-scrollbar__track-y > .x-scrollbar__thumb-y {
    width: ${parseInt(this.thumbSize)}px;
  }
  
  /* 激活后大小 */
  .x-scrollbar__track-x:hover > .x-scrollbar__thumb-x,
  .x-scrollbar__track--draging > .x-scrollbar__thumb-x {
    height: ${parseInt(this.thumbSize) * 2}px;
  }
  
  .x-scrollbar__track-y:hover > .x-scrollbar__thumb-y,
  .x-scrollbar__track--draging > .x-scrollbar__thumb-y {
    width: ${parseInt(this.thumbSize) * 2}px;
  }
  
  /* 鼠标移入轨道 || 拖动过程中 => 显示轨道 & 高亮滑块 */
  .x-scrollbar__track-x:hover,
  .x-scrollbar__track-y:hover,
  .x-scrollbar__track-x.x-scrollbar__track--draging,
  .x-scrollbar__track-y.x-scrollbar__track--draging {
    background: ${this.trackBackground || 'transparent'};
  }`

        this.key = 'x-scrollbar-' + Math.abs(((1 + Math.random()) * Date.now()) | 0).toString(16)
        this.$dom.setAttribute(this.key, '')
        let style = this.html2dom(`<style ${this.key}></style>`)
        content = content.replaceAll('\n.x-scrollbar', `\n[${this.key}] > .x-scrollbar`)
        content = content.replaceAll(';', ' !important;')
        style.innerHTML = content
        document.querySelector('head').appendChild(style)
    }
}

export default XScrollbar
