import { Node, Plugin } from 'tiptap'
import { Decoration, DecorationSet } from 'prosemirror-view'
import { toggleBlockType, setBlockType, textblockTypeInputRule } from 'tiptap-commands'
import { findBlockNodes } from 'prosemirror-utils'
import low from 'lowlight/lib/core'

function getDecorations(doc) {
	const decorations = []

	const blocks = findBlockNodes(doc)
		.filter(item => item.node.type.name === 'code_block')

	const flatten = list => list.reduce(
		(a, b) => a.concat(Array.isArray(b) ? flatten(b) : b), [],
		)

	function parseNodes(nodes, className = []) {
		return nodes.map(node => {

			const classes = [
				...className,
				...node.properties ? node.properties.className : [],
			]

			if (node.children) {
				return parseNodes(node.children, classes)
			}

			return {
				text: node.value,
				classes,
			}
		})
	}

	blocks.forEach(block => {
		let startPos = block.pos + 1
		const nodes = low.highlightAuto(block.node.textContent).value

		flatten(parseNodes(nodes))
			.map(node => {
				const from = startPos
				const to = from + node.text.length

				startPos = to

				return {
					...node,
					from,
					to,
				}
			})
			.forEach(node => {
				const decoration = Decoration.inline(node.from, node.to, {
					class: node.classes.join(' '),
				})
				decorations.push(decoration)
			})
	})

	return DecorationSet.create(doc, decorations)
}

export default class CodeBlockHighlight extends Node {

	constructor(options = {}) {
		super(options)
		try {
			Object.entries(this.options.languages).forEach(([name, mapping]) => {
				low.registerLanguage(name, mapping)
			})
		} catch (err) {
			throw new Error('Invalid syntax highlight definitions: define at least one highlight.js language mapping')
		}
	}

	get defaultOptions() {
		return {
			languages: {},
		}
	}

	get name() {
		return 'code_block'
	}

	get schema() {
		return {
			content: 'text*',
			marks: '',
			group: 'block',
			code: true,
			defining: true,
			draggable: false,
			parseDOM: [
				{ tag: 'pre', preserveWhitespace: 'full' },
			],
			toDOM: () => ['pre', ['code', 0]],
		}
	}

	commands({ type, schema }) {
		return () => toggleBlockType(type, schema.nodes.paragraph)
	}

	keys({ type }) {
		return {
			'Shift-Ctrl-\\': setBlockType(type),
		}
	}

	inputRules({ type }) {
		return [
			textblockTypeInputRule(/^```$/, type),
		]
	}

	get plugins() {
		return [
			new Plugin({
				state: {
					init(_, { doc }) {
						return getDecorations(doc)
					},
					apply(tr, set) {
						// TODO: find way to cache decorations
						// see: https://discuss.prosemirror.net/t/how-to-update-multiple-inline-decorations-on-node-change/1493
						if (tr.docChanged) {
							return getDecorations(tr.doc)
						}
						return set.map(tr.mapping, tr.doc)
					},
				},
				props: {
					decorations(state) {
						return this.getState(state)
					},
				},
			}),
		]
	}

}