/* eslint max-lines: ["error", { "max": 300 }] */
import { keymap } from '@codemirror/view';
import { undo, redo, indentMore, indentLess, deleteLine } from '@codemirror/commands';
import { EditorSelection, ChangeSet } from '@codemirror/state';
import { Prec } from '@codemirror/state';
import * as prettier from 'prettier/standalone';
import * as postcssPlugin from 'prettier/plugins/postcss';

export async function formatCSS(view) {
	try {
		const { from, to, empty } = view.state.selection.main;
		const fullDoc = view.state.doc.toString();
		const selection = view.state.doc.sliceString(from, to);
		const code = empty ? fullDoc : selection;

		let formatted = await prettier.format(code, {
			parser  : 'css',
			plugins : [postcssPlugin],

			// formatting options
			tabWidth       : 2,
			useTabs        : false,
			printWidth     : 100,
			singleQuote    : false,
			trailingComma  : 'all',
			bracketSpacing : true,
			endOfLine      : 'lf'
		});

		//format manually single declaration rules to span one line.
		//Prettier can't do it by default, this is crude but it works
		formatted = formatted.replace(
			/([^{]+)\{\s*\n\s*([^;\n]+:[^;\n]+;)\s*\n\s*\}(\s*)/g,
			(_, selector, decl, whitespace)=>`${selector} { ${decl.trim()} }${whitespace}`
		);
		if(formatted === code) return true;

		const dom = view.dom;
		dom.classList.add('cm-flash');

		setTimeout(()=>{
			dom.classList.remove('cm-flash');

			view.dispatch({
				changes : {
					from   : empty ? 0 : from,
					to     : empty ? view.state.doc.length : to,
					insert : formatted
				}
			});

		}, 500);
	} catch (err) {
		console.error('Error formatting css: ', err);
	}
	return true;
}

const forEachSelection = (view, fn)=>{
	view.dispatch(view.state.changeByRange((range)=>fn(view.state, range)));
	return true;
};

const insertTab = (view)=>{
	// If any selection spans multiple lines, delegates to CodeMirror's indentMore
	// Otherwise inserts two spaces at each cursor/selection
	const shouldIndent = view.state.selection.ranges.some((range)=>view.state.doc.lineAt(range.from).number !==
		view.state.doc.lineAt(range.to).number
	);

	if(shouldIndent) return indentMore(view);

	return forEachSelection(view, (state, range)=>{
		const { from, to } = range;
		return {
			changes : { from, to, insert: '  ' },
			range   : EditorSelection.cursor(from + 2)
		};
	});
	// Insert two spaces, not a tab char!
};

const wrapSelection = (prefix, suffix)=>(view)=>forEachSelection(view, (state, range)=>{
	const { from, to } = range;
	const selected = state.doc.sliceString(from, to);

	const noSelection = from === to;
	if(noSelection) {
		const insert = prefix + suffix;

		return {
			changes : { from, to, insert },
			range   : EditorSelection.cursor(from + prefix.length)
		};
	}

	const hasWrapper = selected.startsWith(prefix) && selected.endsWith(suffix);
	if(hasWrapper) {
		return {
			changes : [
				{ from: to - suffix.length, to, insert: '' },
				{ from,	to: from + prefix.length, insert: '' }
			],
			range : EditorSelection.range(from, to - prefix.length - suffix.length)
		};
	}

	return {
		changes : { from, to, insert: prefix + selected + suffix },
		range   : EditorSelection.range(from, to + prefix.length + suffix.length)
	};
});

const makeNbsp = (view)=>forEachSelection(view, (state, range)=>{
	const { from, to } = range;

	const prev2 = from >= 2 ? state.doc.sliceString(from - 2, from)	: '';
	const insert = (prev2 === ':>' || prev2 === '>>') ? '>' : ':>';

	return {
		changes : { from, to, insert },
		range   : EditorSelection.cursor(from + insert.length)
	};
});

const makeSpace = (view)=>forEachSelection(view, (state, range)=>{
	const { from, to } = range;
	const selected = state.doc.sliceString(from, to);

	let insert = '{{width:10% }}';
	const match = selected.match(/^{{width:(\d+)% }}$/);
	if(match) {
		const percent = Math.min(parseInt(match[1], 10) + 10, 100);
		insert = `{{width:${percent}% }}`;
	}
	return {
		changes : { from, to, insert },
		range   : EditorSelection.range(from, from + insert.length)
	};
});

const removeSpace = (view)=>forEachSelection(view, (state, range)=>{
	const { from, to } = range;
	const selected = state.doc.sliceString(from, to);
	const match = selected.match(/^{{width:(\d+)% }}$/);
	if(match) {
		const percent = parseInt(match[1], 10) - 10;
		const insert = percent > 0 ? `{{width:${percent}% }}` : '';
		return { changes: { from, to, insert: insert } };
	}
});

const makeLink = (view)=>forEachSelection(view, (state, range)=>{
	const { from, to } = range;
	const selected = state.doc.sliceString(from, to).trim();

	// If the selection is already a Markdown link, unwrap it
	const existingLink = /^\[(.*)\]\((.*)\)$/.exec(selected);
	if(existingLink) {
		const [, text, url] = existingLink;
		const insert = `${text} ${url}`;
		return {
			changes : { from, to, insert },
			range   : EditorSelection.range(
				from,
				from + insert.length
			),
		};
	}

	// If the selection is a URL, use its domain as the link text.
	const isUrl =
			/^(https?:\/\/|www\.)\S+$/i.test(selected) ||
			/^[a-z0-9-]+(\.[a-z0-9-]+)+([/?#]\S*)?$/i.test(selected);
	if(isUrl) {
		const domain = selected
				.replace(/^https?:\/\//i, '')
				.replace(/^www\./i, '')
				.split(/[/?#]/)[0];

		const name = domain.split('.')[0];
		const insert = `[${name}](${selected})`;
		return {
			changes : { from, to, insert },
			range   : EditorSelection.range(from, from + insert.length),
		};
	}

	// If the selection is just text, use it as alt text and set url as placeholder
	const insert = `[${selected || 'alt text'}](url)`;
	return {
		changes : { from, to, insert },
		range   : EditorSelection.range(from, from + insert.length),
	};
});

const addPrefixAtLineStart = (prefix)=>(view)=>forEachSelection(view, (state, selectionRange)=>{
	const { from, to } = selectionRange;

	const startLine = state.doc.lineAt(from);
	const endLine = state.doc.lineAt(to);
	const selectedLines = [];

	for (let lineNumber = startLine.number; lineNumber <= endLine.number; lineNumber++) { selectedLines.push(state.doc.line(lineNumber)); }

	const allLinesHavePrefix = selectedLines.every((line)=>line.text.startsWith(prefix));

	const changes = selectedLines.map((line)=>{
		const shouldRemovePrefix = allLinesHavePrefix && line.text.startsWith(prefix);

		return {
			from : line.from,
			to   : shouldRemovePrefix
				? line.from + prefix.length
				: line.from,
			insert : shouldRemovePrefix ? '' : prefix,
		};
	});
	const changeSet = ChangeSet.of(changes, state.doc.length);

	return {
		changes,
		range : EditorSelection.range(
			changeSet.mapPos(from, -1),
			changeSet.mapPos(to, 1)
		),
	};
});

const newBreak = (type)=>(view)=>forEachSelection(view, (state, range)=>{
	const { from, to } = range;
	const insert = `\n\\${type}\n\n`;
	return {
		changes : { from, to, insert },
		range   : EditorSelection.cursor(from + insert.length)
	};
});

export const generalKeymap = Prec.high(keymap.of([
	{ key: 'Tab', run: insertTab },
	{ key: 'Shift-Tab', run: indentLess },
	{ key: 'Mod-z', run: undo }, //it may be unnecessary
	{ key: 'Mod-Shift-z', run: redo },
	{ key: 'Mod-y', run: redo }, //user asked, so double keybind
	{ key: 'Mod-d', run: deleteLine }, //annoyingly overrides "selectNextOccurrence" because users asked
]));

export const cssKeymap = Prec.highest(keymap.of([
	{ key: 'Mod-Shift-f', run: formatCSS },
  	{ key: 'Alt-Shift-f', run: formatCSS },
]));

export const markdownKeymap = Prec.highest(keymap.of([
	{ key: 'Mod-b',           run: wrapSelection('**', '**') },    // makeBold
	{ key: 'Mod-i',           run: wrapSelection('*', '*') },      // makeItalic
	{ key: 'Mod-u',           run: wrapSelection('<u>', '</u>') }, // makeUnderline
	{ key: 'Shift-Mod-=',     run: wrapSelection('^', '^') },      // makeSuper
	{ key: 'Mod-=',           run: wrapSelection('^^', '^^') },    // makeSub
	{ key: 'Mod-.',           run: makeNbsp },
	{ key: 'Shift-Mod-.',     run: makeSpace },
	{ key: 'Shift-Mod-,',     run: removeSpace },
	{ key: 'Mod-m',           run: wrapSelection('{{', '}}') },
	{ key: 'Shift-Mod-m',     run: wrapSelection('{{\n', '\n}}') },
	{ key: 'Mod-/',           run: wrapSelection('<!-- ', ' -->') },
	{ key: 'Mod-Shift-k',     run: makeLink },
	{ key: 'Mod-Shift-u',     run: addPrefixAtLineStart('- ') },
	{ key: 'Mod-Shift-o',     run: addPrefixAtLineStart('1. ') },
	{ key: 'Shift-Mod-1',     run: addPrefixAtLineStart('# ') },
	{ key: 'Shift-Mod-2',     run: addPrefixAtLineStart('## ') },
	{ key: 'Shift-Mod-3',     run: addPrefixAtLineStart('### ') },
	{ key: 'Shift-Mod-4',     run: addPrefixAtLineStart('#### ') },
	{ key: 'Shift-Mod-5',     run: addPrefixAtLineStart('##### ') },
	{ key: 'Shift-Mod-6',     run: addPrefixAtLineStart('###### ') },
	{ key: 'Mod-Enter',       run: newBreak('page') },
	{ key: 'Shift-Mod-Enter', run: newBreak('column') },
]));