/**
 * E-R图绘制方法集
 * 作者：刘广文
 * 邮箱：liugw@imut.edu.cn
 * 版本：20230819
 * 功能：基于canvas实现E-R图的绘制 
 */
var tool = 1;
var current = -1;
var flag=false;
var mouseX= 0;
var mouseY= 0;
var mouseX1= 0;
var mouseY1= 0;
var aryPoint = [];
var aryObject = [];

//加载工具
function loadTools(target){
    target.innerHTML = "<div id=\"entity\" onclick=\"clickTool(this, 1);\" title=\"绘制实体\">实体</div>"
    + "<div id=\"property\" onclick=\"clickTool(this, 2);\" title=\"绘制属性\">属性</div>" 
    + "<div id=\"link1\" onclick=\"clickTool(this, 3);\" title=\"绘制直线\"></div>"
    + "<div id=\"link2\" onclick=\"clickTool(this, 4);\" title=\"绘制折线\"></div>"
    + "<div id=\"relation\" onclick=\"clickTool(this, 5);\" title=\"绘制联系\">联系</div>"
    + "<div id=\"key\" onclick=\"clickTool(this, 6);\" title=\"绘制主键\">主键</div>";
}
//鼠标抬起响应动作
function myMouseUp(e, page){
    flag=false;
    pushTool(tool, mouseX, mouseY, mouseX1, mouseY1, text.value, color.value, bcolor.value, size.value);
    updateTools(cxt);
}
//鼠标移动响应动作
function myMouseMove(e, page){
    mouseX1= e.pageX-page.offsetLeft;
    mouseY1= e.pageY-page.offsetTop;
    if(flag){
        var aryPoint1 = [];
        var i = 0;
        while(i < aryPoint.length){
            aryPoint1.push(aryPoint[i]);
            i ++;
        }
        updateTools(cxt);
        aryPoint = [];
        i = 0;
        while(i < aryPoint1.length){
            aryPoint.push(aryPoint1[i]);
            i ++;
        }
        if (tool == 4){
            var s = aryPoint[aryPoint.length - 1];
            ary = s.split(",");
            var x = parseFloat(ary[0]), y = parseFloat(ary[1]);
            if (Math.abs(x - mouseX1) > 10 || Math.abs(y - mouseY1) > 10)
                aryPoint.push(mouseX1 + "," + mouseY1);
        }
        drawTool(cxt, tool, mouseX, mouseY, mouseX1, mouseY1, color.value, bcolor.value, size.value);
    }
}

//鼠标按下响应动作
function myMouseDown(e, page)
{
    mouseX= e.pageX-page.offsetLeft;
    mouseY= e.pageY-page.offsetTop;
    aryPoint = [];
    aryPoint.push(mouseX + "," + mouseY);
    flag=true;
}
//保存
function save(){
    var ary = [];
    var i = 0;
    while(i <= current){
        ary.push(aryObject[i]);
        i ++;
    }
    aryObject = ary;
    updateButton();
    const fileName = 'erdiagram.txt';
    var str = '';
    i = 0;
    while(i < aryObject.length){
        if (i == 0)
            str = aryObject[i]
        else{
            str += "\r\n"
            str += aryObject[i]
        }
        i ++;
    }
    const content = str
    const blob = new Blob([content], {type: 'application/text'});
    // 构造一个blob对象来处理数据
    // 对于<a>标签，只有 Firefox 和 Chrome（内核） 支持 download 属性
    // IE10以上支持blob但是依然不支持download
    if ('download' in document.createElement('a')) 
    { 
        // 支持a标签download的浏览器
        const link = document.createElement('a') 
        // 创建a标签
        link.download = fileName 
        // a标签添加属性
        link.style.display = 'none'
        link.href = URL.createObjectURL(blob)
        document.body.appendChild(link)
        link.click() 
        // 执行下载
        URL.revokeObjectURL(link.href) 
        // 释放url
        document.body.removeChild(link) 
        // 释放标签
    } else { 
        // 其他浏览器
        navigator.msSaveBlob(blob, fileName)
    }
}
//撤销
function undo(){
    if (current >= 0)
    {
        current --;
        updateTools();
    }
    updateButton();
}
//刷新按钮状态
function updateButton(){
    var undo = document.getElementById("undo");
    var redo = document.getElementById("redo");
    var save = document.getElementById("save");
    if (current >= 0)
    {
        save.disabled = false;
        undo.disabled = false;
    }
    else 
    {
        undo.disabled = true;
        save.disabled = true;
    }
    if (current < aryObject.length - 1)
    {
        redo.disabled = false;
    }
    else {
        redo.disabled = true;
    }
}
//重做
function redo(){
    if (current < aryObject.length - 1)
    {
        current ++;
        updateTools();
    }
    updateButton();
}

//选择工具
function clickTool(o, tag){
    tool = tag;
    for(var i = 0; i < tools.children.length; i ++){
        tools.children[i].style.border = '1px solid black';
    }
    o.style.border = '2px solid red';
    text.hidden = true;
    text.value = "";
    if (tag == 1 || tag == 2 || tag == 5 || tag == 6)
    {
        text.hidden = false;
        text.value = "名称";
    }
    if (tag == 2)
    {
        text.hidden = false;
        text.value = "名称";
    }
    if (tag == 3 || tag == 4){
        text.hidden = false;
        text.value = "";
    }
}

//绘制所有工具
function updateTools(context){
    canvas.width = canvas.width;
    var i = 0;
    while (i <= current){
        var ary = aryObject[i].split('|');
        var type = parseInt(ary[0]);
        var ary1 = ary[1].split(',');
        var x1 = parseFloat(ary1[0]);
        var y1 = parseFloat (ary1[1]);
        var x2 = parseFloat(ary1[2]);
        var y2 = parseFloat(ary1[3]);
        var size = parseFloat(ary[5]);
        var color = ary[3];
        var bcolor = ary[4];
        if(type == 4){
            x2 = parseFloat(ary1[ary1.length - 2]);
            y2 = parseFloat(ary1[ary1.length - 1]);
            aryPoint = [];
            var j = 0;
            while(j < ary1.length){
                var x = parseFloat(ary1[j]), y = parseFloat(ary1[j + 1]);
                aryPoint.push(x + "," + y);
                j += 2;
            }
        }
        drawTool(cxt, type, x1, y1, x2, y2, color, bcolor, size);
        drawText(cxt, type, x1, y1, x2, y2, ary[2], color);
        i ++;
    }
}
//保存当前的绘制
function pushTool(type, x1, y1, x2, y2, text, color, bcolor, size){
    var ary = [];
    var i = 0;
    while(i <= current){
        ary.push(aryObject[i]);
        i ++;
    }
    aryObject = ary;
    var s = type + '|' + x1 + ',' + y1 + ',' + x2 + ',' + y2 + '|' + text + '|' + color + '|' + bcolor + '|' + size;
    if(type == 4){
        s = type + '|';
        i = 0;
        while(i < aryPoint.length){
            if (i > 0)
                s += ","; 
            s += aryPoint[i];
            i ++;
        }
        s = s + '|' + text + '|' + color + '|' + bcolor + '|' + size;
    }
    aryObject.push(s);
    current ++;
    updateButton();
}
//绘制文本
function drawText(context, type, x1, y1, x2, y2, text, color){
    if (text == "" || context == null || type < 1) return;
    switch(type){
        case 1:
        case 2:
        case 5:
        case 6:{     
            //绘制开始框
            //计算宽高
            var l = x1, t = y1;
            var w = x2 - x1, h = y2 - y1;
            if (w < 0)
            {
                l = x2;
                w = x1 - x2;
            }               
            if (h < 0){
                t = y2;
                h = y1 - y2;
            }
            context.font = "10pt SimSun";
            var w1 = getFontWidth(context, text);
            var h1 = getFontHeight(context, text);
            context.fillStyle = color;
            context.fillText(text, l + (w - w1) / 2, t + h1 / 4 + h / 2);
            if (type == 6)
            {
                cxt.moveTo(l + (w - w1) / 2, t + h1 / 4 + h / 2);
                cxt.lineTo(l + (w + w1) / 2, t + h1 / 4 + h / 2);
                cxt.stroke();
            }
            break;
        }  
        case 3:{     
            //绘制箭头
            //计算文字大小                
            context.font = "10pt SimSun";
            var w = getFontWidth(context, text);
            var h = getFontHeight(context, text);
            //获得输出坐标
            var x = (x2 + x1) / 2;
            var y = (y2 + y1) / 2;                
            context.fillStyle = color;
            context.fillText(text, x, y);
            break;
        } 
        case 4:{     
            //绘制箭头
            //计算文字大小                
            context.font = "10pt SimSun";
            var w = getFontWidth(context, text);
            var h = getFontHeight(context, text);
            //获得输出坐标
            var px1 = x1, py1 = y1;
            var i = 1;
            var pp = 0;
            while(i < aryPoint.length)
            {
                var ary = aryPoint[i].split(',');
                var px = parseFloat(ary[0]), py = parseFloat(ary[1]);
                var pp1 = 2;
                if (Math.abs(px - px1) > Math.abs(py - py1)) pp1 = 1;
                if (pp != 0 && pp1 != pp) break;
                pp = pp1;
                px1 = px;
                py1 = py;
                i ++;
            }
            var x = (px1 + x1) / 2;
            var y = (py1 + y1) / 2;                
            context.fillStyle = color;
            context.fillText(text, x, y);
            break;
        } 
    }
    
}
//绘制当前工具
function drawTool(context, type, x1, y1, x2, y2, color, bcolor, size){
    if (context == null || type < 1) return;
    switch(type){
        case 1:{     
            //绘制实体
            //计算宽高
            var l = x1, t = y1;
            var w = x2 - x1, h = y2 - y1;
            if (w < 0)
            {
                l = x2;
                w = x1 - x2;
            }               
            if (h < 0){
                t = y2;
                h = y1 - y2;
            }
            context.strokeStyle = color;
            context.lineWidth = size;
            context.beginPath();
            context.moveTo(l, t);
            context.lineTo(l + w, t);
            context.lineTo(l + w, t + h);
            context.lineTo(l, t + h);
            context.lineTo(l, t);
            context.closePath();
            context.fillStyle = bcolor;
            context.fill();
            context.stroke();
            break;
        } 
        case 3:{     
            //绘制直线
            context.strokeStyle = color;
            context.lineWidth = size;
            context.moveTo(x1, y1);
            context.lineTo(x2, y2);
            context.stroke();
            break;
        }             
        case 4:{     
            //绘制折线
            if (aryPoint.length < 3)
                break;
            var ary = aryPoint[aryPoint.length - 2].split(',');
            var px1 = parseFloat(ary[0]), py1 = parseFloat(ary[1]);
            ary = aryPoint[aryPoint.length - 1].split(',');
            var px2 = parseFloat(ary[0]), py2 = parseFloat(ary[1]);
            if (Math.abs(px2 - px1) > Math.abs(py2 - py1))
                py1 = py2;
            else px1 = px2;
            context.strokeStyle = color;
            context.lineWidth = size;
            context.moveTo(px2, py2);
            context.lineTo(px1, py1);
            var i = aryPoint.length - 3;
            while(i >= 0){
                ary = aryPoint[i].split(',');
                px2 = parseFloat(ary[0]), py2 = parseFloat(ary[1]);
                if (Math.abs(px2 - px1) > Math.abs(py2 - py1))
                    py2 = py1;
                else px2 = px1;
                context.moveTo(px1, py1);
                context.lineTo(px2, py2);
                px1 = px2;
                py1 = py2;
                i --;
            }
            context.stroke();
            break;
        } 
        case 5:{     
            //绘制联系
            //计算宽高
            var l = x1, t = y1;
            var w = x2 - x1, h = y2 - y1;
            if (w < 0)
            {
                l = x2;
                w = x1 - x2;
            }               
            if (h < 0){
                t = y2;
                h = y1 - y2;
            }
            context.strokeStyle = color;
            context.lineWidth = size;
            context.beginPath();
            context.moveTo(l, t + h / 2);
            context.lineTo(l + w / 2, t);
            context.lineTo(l + w, t + h / 2);
            context.lineTo(l + w / 2, t + h);
            context.lineTo(l, t + h / 2);
            context.closePath();
            context.fillStyle = bcolor;
            context.fill();
            context.stroke();
            break;
        } 
        case 2:
        case 6:{     
            //绘制属性
            //计算宽高
            var l = x1, t = y1;
            var w = x2 - x1, h = y2 - y1;
            if (w < 0)
            {
                l = x2;
                w = x1 - x2;
            }               
            if (h < 0){
                t = y2;
                h = y1 - y2;
            }
            context.strokeStyle = color;
            context.lineWidth = size;
            var r = w * 0.4;
            if (h < w)
                r = h * 0.4;
            context.beginPath();
            context.moveTo(l + r, t);
            context.arcTo(l + w, t, l + w, t + h, r);
            context.arcTo(l + w, t + h, l, t + h, r);
            context.arcTo(l, t + h, l, t, r);
            context.arcTo(l, t, l + w, t, r);
            context.closePath();
            context.fillStyle = bcolor;
            context.fill();
            context.stroke();
            break;
        } 
    }
}

//计算当前字体下的文本宽度
function getFontWidth(context, txt) {
    const metrics = context.measureText(txt);
    const actual = Math.abs(metrics.actualBoundingBoxLeft ?? 0) + Math.abs(metrics.actualBoundingBoxRight ?? 0);
    const width = Math.max(metrics.width, actual);
    return width;
}
//计算当前字体下的文本高度
function getFontHeight(context, txt) {
    const metrics = context.measureText(txt);
    const fontHeight = metrics.fontBoundingBoxAscent + metrics.fontBoundingBoxDescent;
    //所有字在这个字体下的高度
    //const actualHeight = metrics.actualBoundingBoxAscent + metrics.actualBoundingBoxDescent;
    return fontHeight;
}
//自动调整字体大小
function updateFont(context, w, h, text, size){
    context.font = size + "pt SimSun";
    w1 = getFontWidth(context, text) * 2;
    h1 = getFontHeight(context, text) * 2;
    var s = size;
    while (w1 > w || h1 > h){
        s = s - 1;
        context.font = s + "pt SimSun";
        w1 = getFontWidth(context, text) * 2;
        h1 = getFontHeight(context, text) * 2;
    }
    return s;
}