define(['core/ArrayUtilities'], (array) => {
	'use strict';

	const CM_END = {type: '', suggest: '\n', then: {}};
	const CM_HIDDEN_END = {type: '', then: {}};
	const CM_ERROR = {type: 'error line-error', then: {'': 0}};

	function makeCMCommaBlock(type, suggest, exits = {}) {
		return {type, suggest, then: Object.assign({
			'': 0,
			',': {type: 'operator', suggest: true, then: {
				'': 1,
			}},
		}, exits)};
	}

	const CM_TEXT_TO_END = {type: 'string', then: {'': 0, '\n': CM_END}};
	const CM_AGENT_LIST_TO_END = makeCMCommaBlock('variable', 'Agent', {
		'\n': CM_END,
	});
	const CM_AGENT_LIST_TO_TEXT = makeCMCommaBlock('variable', 'Agent', {
		':': {type: 'operator', suggest: true, then: {'': CM_TEXT_TO_END}},
	});
	const CM_AGENT_TO_OPTTEXT = {type: 'variable', suggest: 'Agent', then: {
		'': 0,
		':': {type: 'operator', suggest: true, then: {
			'': CM_TEXT_TO_END,
			'\n': CM_HIDDEN_END,
		}},
		'\n': CM_END,
	}};

	function makeCMSideNote(side) {
		return {
			type: 'keyword',
			suggest: [side + ' of ', side + ': '],
			then: {
				'of': {type: 'keyword', suggest: true, then: {
					'': CM_AGENT_LIST_TO_TEXT,
				}},
				':': {type: 'operator', suggest: true, then: {
					'': CM_TEXT_TO_END,
				}},
				'': CM_AGENT_LIST_TO_TEXT,
			},
		};
	}

	const CM_CONNECT = {type: 'keyword', suggest: true, then: {
		'+': {type: 'operator', suggest: true, then: {'': CM_AGENT_TO_OPTTEXT}},
		'-': {type: 'operator', suggest: true, then: {'': CM_AGENT_TO_OPTTEXT}},
		'': CM_AGENT_TO_OPTTEXT,
	}};

	const CM_CONNECT_FULL = {type: 'variable', suggest: 'Agent', then: {
		'->': CM_CONNECT,
		'-->': CM_CONNECT,
		'<-': CM_CONNECT,
		'<--': CM_CONNECT,
		'<->': CM_CONNECT,
		'<-->': CM_CONNECT,
		':': {type: 'operator', suggest: true, override: 'Label', then: {}},
		'': 0,
	}};

	const CM_COMMANDS = {type: 'error line-error', then: {
		'title': {type: 'keyword', suggest: true, then: {
			'': CM_TEXT_TO_END,
		}},
		'terminators': {type: 'keyword', suggest: true, then: {
			'none': {type: 'keyword', suggest: true, then: {}},
			'cross': {type: 'keyword', suggest: true, then: {}},
			'box': {type: 'keyword', suggest: true, then: {}},
			'bar': {type: 'keyword', suggest: true, then: {}},
		}},
		'define': {type: 'keyword', suggest: true, then: {
			'': CM_AGENT_LIST_TO_END,
		}},
		'begin': {type: 'keyword', suggest: true, then: {
			'': CM_AGENT_LIST_TO_END,
		}},
		'end': {type: 'keyword', suggest: true, then: {
			'': CM_AGENT_LIST_TO_END,
			'\n': CM_END,
		}},
		'if': {type: 'keyword', suggest: true, then: {
			'': CM_TEXT_TO_END,
			':': {type: 'operator', suggest: true, then: {
				'': CM_TEXT_TO_END,
			}},
			'\n': CM_END,
		}},
		'else': {type: 'keyword', suggest: ['else\n', 'else if: '], then: {
			'if': {type: 'keyword', suggest: 'if: ', then: {
				'': CM_TEXT_TO_END,
				':': {type: 'operator', suggest: true, then: {
					'': CM_TEXT_TO_END,
				}},
			}},
			'\n': CM_END,
		}},
		'repeat': {type: 'keyword', suggest: true, then: {
			'': CM_TEXT_TO_END,
			':': {type: 'operator', suggest: true, then: {
				'': CM_TEXT_TO_END,
			}},
			'\n': CM_END,
		}},
		'note': {type: 'keyword', suggest: true, then: {
			'over': {type: 'keyword', suggest: true, then: {
				'': CM_AGENT_LIST_TO_TEXT,
			}},
			'left': makeCMSideNote('left'),
			'right': makeCMSideNote('right'),
			'between': {type: 'keyword', suggest: true, then: {
				'': CM_AGENT_LIST_TO_TEXT,
			}},
		}},
		'state': {type: 'keyword', suggest: 'state over ', then: {
			'over': {type: 'keyword', suggest: true, then: {
				'': CM_AGENT_LIST_TO_TEXT,
			}},
		}},
		'text': {type: 'keyword', suggest: true, then: {
			'left': makeCMSideNote('left'),
			'right': makeCMSideNote('right'),
		}},
		'simultaneously': {type: 'keyword', suggest: true, then: {
			':': {type: 'operator', suggest: true, then: {}},
			'with': {type: 'keyword', suggest: true, then: {
				'': {type: 'variable', suggest: 'Label', then: {
					'': 0,
					':': {type: 'operator', suggest: true, then: {}},
				}},
			}},
		}},
		'+': {type: 'operator', suggest: true, then: {'': CM_CONNECT_FULL}},
		'-': {type: 'operator', suggest: true, then: {'': CM_CONNECT_FULL}},
		'': CM_CONNECT_FULL,
	}};

	function cmCappedToken(token, current) {
		if(Object.keys(current.then).length > 0) {
			return token + ' ';
		} else {
			return token + '\n';
		}
	}

	function cmGetVarSuggestions(state, previous, current) {
		if(
			typeof current.suggest !== 'string' ||
			previous.suggest === current.suggest
		) {
			return null;
		}
		return state['known' + current.suggest];
	}

	function cmGetSuggestions(state, token, previous, current) {
		if(token === '') {
			return cmGetVarSuggestions(state, previous, current);
		} else if(current.suggest === true) {
			return [cmCappedToken(token, current)];
		} else if(Array.isArray(current.suggest)) {
			return current.suggest;
		} else if(current.suggest) {
			return [current.suggest];
		} else {
			return null;
		}
	}

	function cmMakeCompletions(state, path) {
		const comp = [];
		const current = array.last(path);
		Object.keys(current.then).forEach((token) => {
			let next = current.then[token];
			if(typeof next === 'number') {
				next = path[path.length - next - 1];
			}
			array.mergeSets(
				comp,
				cmGetSuggestions(state, token, current, next)
			);
		});
		return comp;
	}

	function updateSuggestion(state, locals, token, {suggest, override}) {
		if(locals.type) {
			if(suggest !== locals.type) {
				if(override) {
					locals.type = override;
				}
				array.mergeSets(
					state['known' + locals.type],
					[locals.value]
				);
				locals.type = '';
			} else {
				locals.value += token + ' ';
			}
		} else if(typeof suggest === 'string' && state['known' + suggest]) {
			locals.type = suggest;
			locals.value = token + ' ';
		}
	}

	function cmCheckToken(state, eol) {
		const suggestions = {
			type: '',
			value: '',
		};
		let current = CM_COMMANDS;
		const path = [current];

		state.line.forEach((token, i) => {
			if(i === state.line.length - 1) {
				state.completions = cmMakeCompletions(state, path);
			}
			const keywordToken = token.q ? '' : token.v;
			const found = current.then[keywordToken] || current.then[''];
			if(typeof found === 'number') {
				path.length -= found;
			} else {
				path.push(found || CM_ERROR);
			}
			current = array.last(path);
			updateSuggestion(state, suggestions, token.v, current);
		});
		if(eol) {
			updateSuggestion(state, suggestions, '', {});
		}
		state.nextCompletions = cmMakeCompletions(state, path);
		state.valid = (
			Boolean(current.then['\n']) ||
			Object.keys(current.then).length === 0
		);
		return current.type;
	}

	function getInitialToken(block) {
		const baseToken = (block.baseToken || {});
		return {
			value: baseToken.v || '',
			quoted: baseToken.q || false,
		};
	}

	return class Mode {
		constructor(tokenDefinitions) {
			this.tokenDefinitions = tokenDefinitions;
			this.lineComment = '#';
		}

		startState() {
			return {
				currentType: -1,
				current: '',
				currentQuoted: false,
				knownAgent: [],
				knownLabel: [],
				beginCompletions: cmMakeCompletions({}, [CM_COMMANDS]),
				completions: [],
				nextCompletions: [],
				valid: true,
				line: [],
				indent: 0,
			};
		}

		_matchPattern(stream, pattern, consume) {
			if(!pattern) {
				return null;
			}
			pattern.lastIndex = 0;
			return stream.match(pattern, consume);
		}

		_tokenBegin(stream, state) {
			while(true) {
				if(stream.eol()) {
					return false;
				}
				for(let i = 0; i < this.tokenDefinitions.length; ++ i) {
					const block = this.tokenDefinitions[i];
					if(this._matchPattern(stream, block.start, true)) {
						state.currentType = i;
						const {value, quoted} = getInitialToken(block);
						state.current = value;
						state.currentQuoted = quoted;
						return true;
					}
				}
				stream.next();
			}
		}

		_tokenCheckEscape(stream, state, block) {
			const match = this._matchPattern(stream, block.escape, true);
			if(match) {
				state.current += block.escapeWith(match);
			}
		}

		_tokenEndFound(stream, state, block) {
			state.currentType = -1;
			if(block.omit) {
				return 'comment';
			}
			state.line.push({v: state.current, q: state.currentQuoted});
			return cmCheckToken(state, stream.eol());
		}

		_tokenEOLFound(stream, state, block) {
			state.current += '\n';
			if(block.omit) {
				return 'comment';
			}
			state.line.push(({v: state.current, q: state.currentQuoted}));
			const type = cmCheckToken(state, false);
			state.line.pop();
			return type;
		}

		_tokenEnd(stream, state) {
			while(true) {
				const block = this.tokenDefinitions[state.currentType];
				this._tokenCheckEscape(stream, state, block);
				if(!block.end || this._matchPattern(stream, block.end, true)) {
					return this._tokenEndFound(stream, state, block);
				}
				if(stream.eol()) {
					return this._tokenEOLFound(stream, state, block);
				}
				state.current += stream.next();
			}
		}

		token(stream, state) {
			state.completions = state.nextCompletions;
			if(stream.sol() && state.currentType === -1) {
				state.line.length = 0;
			}
			let type = '';
			if(state.currentType !== -1 || this._tokenBegin(stream, state)) {
				type = this._tokenEnd(stream, state);
			}
			if(state.currentType === -1 && stream.eol() && !state.valid) {
				return 'line-error ' + type;
			} else {
				return type;
			}
		}

		indent(state) {
			return state.indent;
		}
	};
});