"use strict";

/**
 * Various components for drawing diagrams on an HTML5 canvas.
 *
 * @author n1474335 [n1474335@gmail.com]
 * @copyright Crown Copyright 2016
 * @license Apache-2.0
 *
 * @constant
 * @namespace
 */
var CanvasComponents = module.exports = {

    drawLine: function(ctx, startX, startY, endX, endY) {
        ctx.beginPath();
        ctx.moveTo(startX, startY);
        ctx.lineTo(endX, endY);
        ctx.closePath();
        ctx.stroke();
    },

    drawBarChart: function(canvas, scores, xAxisLabel, yAxisLabel, numXLabels, numYLabels, fontSize) {
        fontSize = fontSize || 15;
        if (!numXLabels || numXLabels > Math.round(canvas.width / 50)) {
            numXLabels = Math.round(canvas.width / 50);
        }
        if (!numYLabels || numYLabels > Math.round(canvas.width / 50)) {
            numYLabels = Math.round(canvas.height / 50);
        }

        // Graph properties
        var ctx = canvas.getContext("2d"),
            leftPadding = canvas.width * 0.08,
            rightPadding = canvas.width * 0.03,
            topPadding = canvas.height * 0.08,
            bottomPadding = canvas.height * 0.15,
            graphHeight = canvas.height - topPadding - bottomPadding,
            graphWidth = canvas.width - leftPadding - rightPadding,
            base = topPadding + graphHeight,
            ceil = topPadding;

        ctx.font = fontSize + "px Arial";

        // Draw axis
        ctx.lineWidth = "1.0";
        ctx.strokeStyle = "#444";
        CanvasComponents.drawLine(ctx, leftPadding, base, graphWidth + leftPadding, base); // x
        CanvasComponents.drawLine(ctx, leftPadding, base, leftPadding, ceil); // y

        // Bar properties
        var barPadding = graphWidth * 0.003,
            barWidth = (graphWidth - (barPadding * scores.length)) / scores.length,
            currX = leftPadding + barPadding,
            max = Math.max.apply(Math, scores);

        // Draw bars
        ctx.fillStyle = "green";
        for (var i = 0; i < scores.length; i++) {
            var h = scores[i] / max * graphHeight;
            ctx.fillRect(currX, base - h, barWidth, h);
            currX += barWidth + barPadding;
        }

        // Mark x axis
        ctx.fillStyle = "black";
        ctx.textAlign = "center";
        currX = leftPadding + barPadding;
        if (numXLabels >= scores.length) {
            // Mark every score
            for (i = 0; i <= scores.length; i++) {
                ctx.fillText(i, currX, base + (bottomPadding * 0.3));
                currX += barWidth + barPadding;
            }
        } else {
            // Mark some scores
            for (i = 0; i <= numXLabels; i++) {
                var val = Math.ceil((scores.length / numXLabels) * i);
                currX = (graphWidth / numXLabels) * i + leftPadding;
                ctx.fillText(val, currX, base + (bottomPadding * 0.3));
            }
        }

        // Mark y axis
        ctx.textAlign = "right";
        var currY;
        if (numYLabels >= max) {
            // Mark every increment
            for (i = 0; i <= max; i++) {
                currY = base - (i / max * graphHeight) + fontSize / 3;
                ctx.fillText(i, leftPadding * 0.8, currY);
            }
        } else {
            // Mark some increments
            for (i = 0; i <= numYLabels; i++) {
                val = Math.ceil((max / numYLabels) * i);
                currY = base - (val / max * graphHeight) + fontSize / 3;
                ctx.fillText(val, leftPadding * 0.8, currY);
            }
        }

        // Label x axis
        if (xAxisLabel) {
            ctx.textAlign = "center";
            ctx.fillText(xAxisLabel, graphWidth / 2 + leftPadding, base + bottomPadding * 0.8);
        }

        // Label y axis
        if (yAxisLabel) {
            ctx.save();
            var x = leftPadding * 0.3,
                y = graphHeight / 2 + topPadding;
            ctx.translate(x, y);
            ctx.rotate(-Math.PI / 2);
            ctx.textAlign = "center";
            ctx.fillText(yAxisLabel, 0, 0);
            ctx.restore();
        }
    },

    drawScaleBar: function(canvas, score, max, markings) {
        // Bar properties
        var ctx = canvas.getContext("2d"),
            leftPadding = canvas.width * 0.01,
            rightPadding = canvas.width * 0.01,
            topPadding = canvas.height * 0.1,
            bottomPadding = canvas.height * 0.3,
            barHeight = canvas.height - topPadding - bottomPadding,
            barWidth = canvas.width - leftPadding - rightPadding;

        // Scale properties
        var proportion = score / max;

        // Draw bar outline
        ctx.strokeRect(leftPadding, topPadding, barWidth, barHeight);

        // Shade in up to proportion
        var grad = ctx.createLinearGradient(leftPadding, 0, barWidth + leftPadding, 0);
        grad.addColorStop(0, "green");
        grad.addColorStop(0.5, "gold");
        grad.addColorStop(1, "red");
        ctx.fillStyle = grad;
        ctx.fillRect(leftPadding, topPadding, barWidth * proportion, barHeight);

        // Add markings
        var x0, y0, x1, y1;
        ctx.fillStyle = "black";
        ctx.textAlign = "center";
        ctx.font = "13px Arial";
        for (var i = 0; i < markings.length; i++) {
            // Draw min line down
            x0 = barWidth / max * markings[i].min + leftPadding;
            y0 = topPadding + barHeight + (bottomPadding * 0.1);
            x1 = x0;
            y1 = topPadding + barHeight + (bottomPadding * 0.3);
            CanvasComponents.drawLine(ctx, x0, y0, x1, y1);

            // Draw max line down
            x0 = barWidth / max * markings[i].max + leftPadding;
            x1 = x0;
            CanvasComponents.drawLine(ctx, x0, y0, x1, y1);

            // Join min and max lines
            x0 = barWidth / max * markings[i].min + leftPadding;
            y0 = topPadding + barHeight + (bottomPadding * 0.3);
            x1 = barWidth / max * markings[i].max + leftPadding;
            y1 = y0;
            CanvasComponents.drawLine(ctx, x0, y0, x1, y1);

            // Add label
            if (markings[i].max >= max * 0.9) {
                ctx.textAlign = "right";
                x0 = x1;
            } else if (markings[i].max <= max * 0.1) {
                ctx.textAlign = "left";
            } else {
                x0 = x0 + (x1 - x0) / 2;
            }
            y0 = topPadding + barHeight + (bottomPadding * 0.8);
            ctx.fillText(markings[i].label, x0, y0);
        }
    },

};