import defaults from '../core/core.defaults';
import Element from '../core/core.element';
import layouts from '../core/core.layouts';
import {isArray, valueOrDefault, mergeIf} from '../helpers/helpers.core';
import {toPadding, _parseFont} from '../helpers/helpers.options';

defaults.set('title', {
	align: 'center',
	display: false,
	fontStyle: 'bold',
	fullWidth: true,
	padding: 10,
	position: 'top',
	text: '',
	weight: 2000         // by default greater than legend (1000) to be above
});

export class Title extends Element {
	constructor(config) {
		super();

		Object.assign(this, config);

		this.chart = config.chart;
		this.options = config.options;
		this.ctx = config.ctx;
		this._margins = undefined;
		this._padding = undefined;
		this.legendHitBoxes = []; // Contains hit boxes for each dataset (in dataset order)
		this.top = undefined;
		this.bottom = undefined;
		this.left = undefined;
		this.right = undefined;
		this.width = undefined;
		this.height = undefined;
		this.maxWidth = undefined;
		this.maxHeight = undefined;
		this.position = undefined;
		this.weight = undefined;
		this.fullWidth = undefined;
	}

	// These methods are ordered by lifecycle. Utilities then follow.


	beforeUpdate() {}

	update(maxWidth, maxHeight, margins) {
		const me = this;

		// Update Lifecycle - Probably don't want to ever extend or overwrite this function ;)
		me.beforeUpdate();

		// Absorb the master measurements
		me.maxWidth = maxWidth;
		me.maxHeight = maxHeight;
		me._margins = margins;

		// Dimensions
		me.beforeSetDimensions();
		me.setDimensions();
		me.afterSetDimensions();
		// Labels
		me.beforeBuildLabels();
		me.buildLabels();
		me.afterBuildLabels();

		// Fit
		me.beforeFit();
		me.fit();
		me.afterFit();
		//
		me.afterUpdate();

	}

	afterUpdate() {}


	beforeSetDimensions() {}

	setDimensions() {
		const me = this;
		// Set the unconstrained dimension before label rotation
		if (me.isHorizontal()) {
			// Reset position before calculating rotation
			me.width = me.maxWidth;
			me.left = 0;
			me.right = me.width;
		} else {
			me.height = me.maxHeight;

			// Reset position before calculating rotation
			me.top = 0;
			me.bottom = me.height;
		}
	}

	afterSetDimensions() {}

	beforeBuildLabels() {}

	buildLabels() {}

	afterBuildLabels() {}

	beforeFit() {}

	fit() {
		const me = this;
		const opts = me.options;
		const minSize = {};
		const isHorizontal = me.isHorizontal();

		if (!opts.display) {
			me.width = minSize.width = me.height = minSize.height = 0;
			return;
		}

		const lineCount = isArray(opts.text) ? opts.text.length : 1;
		me._padding = toPadding(opts.padding);
		const textSize = lineCount * _parseFont(opts).lineHeight + me._padding.height;
		me.width = minSize.width = isHorizontal ? me.maxWidth : textSize;
		me.height = minSize.height = isHorizontal ? textSize : me.maxHeight;
	}

	afterFit() {}

	// Shared Methods
	isHorizontal() {
		const pos = this.options.position;
		return pos === 'top' || pos === 'bottom';
	}

	// Actually draw the title block on the canvas
	draw() {
		const me = this;
		const ctx = me.ctx;
		const opts = me.options;

		if (!opts.display) {
			return;
		}

		const fontOpts = _parseFont(opts);
		const lineHeight = fontOpts.lineHeight;
		const offset = lineHeight / 2 + me._padding.top;
		let rotation = 0;
		const top = me.top;
		const left = me.left;
		const bottom = me.bottom;
		const right = me.right;
		let maxWidth, titleX, titleY;
		let align;

		// Horizontal
		if (me.isHorizontal()) {
			switch (opts.align) {
			case 'start':
				titleX = left;
				align = 'left';
				break;
			case 'end':
				titleX = right;
				align = 'right';
				break;
			default:
				titleX = left + ((right - left) / 2);
				align = 'center';
				break;
			}

			titleY = top + offset;
			maxWidth = right - left;
		} else {
			titleX = opts.position === 'left' ? left + offset : right - offset;

			switch (opts.align) {
			case 'start':
				titleY = opts.position === 'left' ? bottom : top;
				align = 'left';
				break;
			case 'end':
				titleY = opts.position === 'left' ? top : bottom;
				align = 'right';
				break;
			default:
				titleY = top + ((bottom - top) / 2);
				align = 'center';
				break;
			}
			maxWidth = bottom - top;
			rotation = Math.PI * (opts.position === 'left' ? -0.5 : 0.5);
		}

		ctx.save();

		ctx.fillStyle = valueOrDefault(opts.fontColor, defaults.fontColor); // render in correct colour
		ctx.font = fontOpts.string;

		ctx.translate(titleX, titleY);
		ctx.rotate(rotation);
		ctx.textAlign = align;
		ctx.textBaseline = 'middle';

		const text = opts.text;
		if (isArray(text)) {
			let y = 0;
			for (let i = 0; i < text.length; ++i) {
				ctx.fillText(text[i], 0, y, maxWidth);
				y += lineHeight;
			}
		} else {
			ctx.fillText(text, 0, 0, maxWidth);
		}

		ctx.restore();
	}
}

function createNewTitleBlockAndAttach(chart, titleOpts) {
	const title = new Title({
		ctx: chart.ctx,
		options: titleOpts,
		chart
	});

	layouts.configure(chart, title, titleOpts);
	layouts.addBox(chart, title);
	chart.titleBlock = title;
}

export default {
	id: 'title',

	/**
	 * Backward compatibility: since 2.1.5, the title is registered as a plugin, making
	 * Chart.Title obsolete. To avoid a breaking change, we export the Title as part of
	 * the plugin, which one will be re-exposed in the chart.js file.
	 * https://github.com/chartjs/Chart.js/pull/2640
	 * @private
	 */
	_element: Title,

	beforeInit(chart) {
		const titleOpts = chart.options.title;

		if (titleOpts) {
			createNewTitleBlockAndAttach(chart, titleOpts);
		}
	},

	beforeUpdate(chart) {
		const titleOpts = chart.options.title;
		const titleBlock = chart.titleBlock;

		if (titleOpts) {
			mergeIf(titleOpts, defaults.title);

			if (titleBlock) {
				layouts.configure(chart, titleBlock, titleOpts);
				titleBlock.options = titleOpts;
			} else {
				createNewTitleBlockAndAttach(chart, titleOpts);
			}
		} else if (titleBlock) {
			layouts.removeBox(chart, titleBlock);
			delete chart.titleBlock;
		}
	}
};