import { IDataObject, INodeExecutionData } from 'n8n-workflow';
import { difference, get, intersection, isEmpty, isEqual, omit, set, union } from 'lodash';

type PairToMatch = {
	field1: string;
	field2: string;
};

type EntryMatches = {
	entry: INodeExecutionData;
	matches: INodeExecutionData[];
};

function compareItems(
	item1: INodeExecutionData,
	item2: INodeExecutionData,
	fieldsToMatch: PairToMatch[],
	resolve: string,
	skipFields: string[],
) {
	const keys = {} as IDataObject;
	fieldsToMatch.forEach((field) => {
		keys[field.field1] = item1.json[field.field1];
	});

	const keys1 = Object.keys(item1.json);
	const keys2 = Object.keys(item2.json);
	const intersectionKeys = intersection(keys1, keys2);

	const same = intersectionKeys.reduce((acc, key) => {
		if (isEqual(item1.json[key], item2.json[key])) {
			acc[key] = item1.json[key];
		}
		return acc;
	}, {} as IDataObject);

	const sameKeys = Object.keys(same);
	const allUniqueKeys = union(keys1, keys2);
	const differentKeys = difference(allUniqueKeys, sameKeys);

	const different: IDataObject = {};
	const skipped: IDataObject = {};

	differentKeys.forEach((key) => {
		switch (resolve) {
			case 'preferInput1':
				different[key] = item1.json[key] || null;
				break;
			case 'preferInput2':
				different[key] = item2.json[key] || null;
				break;
			default:
				const input1 = item1.json[key] || null;
				const input2 = item2.json[key] || null;
				if (skipFields.includes(key)) {
					skipped[key] = { input1, input2 };
				} else {
					different[key] = { input1, input2 };
				}
		}
	});

	return {
		json: { keys, same, different, ...(!isEmpty(skipped) && { skipped }) },
	} as INodeExecutionData;
}

function combineItems(
	item1: INodeExecutionData,
	item2: INodeExecutionData,
	prefer: string,
	except: string,
	disableDotNotation: boolean,
) {
	let exceptFields: string[];
	const [entry, match] = prefer === 'input1' ? [item1, item2] : [item2, item1];

	if (except && Array.isArray(except) && except.length) {
		exceptFields = except;
	} else {
		exceptFields = except ? except.split(',').map((field) => field.trim()) : [];
	}

	exceptFields.forEach((field) => {
		entry.json[field] = match.json[field];
		if (disableDotNotation) {
			entry.json[field] = match.json[field];
		} else {
			const value = get(match.json, field) || null;
			set(entry, `json.${field}`, value);
		}
	});

	return entry;
}

function findAllMatches(
	data: INodeExecutionData[],
	lookup: IDataObject,
	disableDotNotation: boolean,
) {
	return data.reduce((acc, entry2, i) => {
		if (entry2 === undefined) return acc;

		for (const key of Object.keys(lookup)) {
			const excpectedValue = lookup[key];
			let entry2FieldValue;

			if (disableDotNotation) {
				entry2FieldValue = entry2.json[key];
			} else {
				entry2FieldValue = get(entry2.json, key);
			}

			if (!isEqual(excpectedValue, entry2FieldValue)) {
				return acc;
			}
		}

		return acc.concat({
			entry: entry2,
			index: i,
		});
	}, [] as IDataObject[]);
}

function findFirstMatch(
	data: INodeExecutionData[],
	lookup: IDataObject,
	disableDotNotation: boolean,
) {
	const index = data.findIndex((entry2) => {
		if (entry2 === undefined) return false;

		for (const key of Object.keys(lookup)) {
			const excpectedValue = lookup[key];
			let entry2FieldValue;

			if (disableDotNotation) {
				entry2FieldValue = entry2.json[key];
			} else {
				entry2FieldValue = get(entry2.json, key);
			}

			if (!isEqual(excpectedValue, entry2FieldValue)) {
				return false;
			}
		}

		return true;
	});
	if (index === -1) return [];

	return [{ entry: data[index], index }];
}

export function findMatches(
	input1: INodeExecutionData[],
	input2: INodeExecutionData[],
	fieldsToMatch: PairToMatch[],
	options: IDataObject,
) {
	const data1 = [...input1];
	const data2 = [...input2];

	const disableDotNotation = (options.disableDotNotation as boolean) || false;
	const multipleMatches = (options.multipleMatches as string) || 'first';
	const skipFields = ((options.skipFields as string) || '').split(',').map((field) => field.trim());

	const filteredData = {
		matched: [] as EntryMatches[],
		unmatched1: [] as INodeExecutionData[],
		unmatched2: [] as INodeExecutionData[],
	};

	const matchedInInput2 = new Set<number>();

	matchesLoop: for (const entry of data1) {
		const lookup: IDataObject = {};

		fieldsToMatch.forEach((matchCase) => {
			let valueToCompare;
			if (disableDotNotation) {
				valueToCompare = entry.json[matchCase.field1 as string];
			} else {
				valueToCompare = get(entry.json, matchCase.field1 as string);
			}
			lookup[matchCase.field2 as string] = valueToCompare;
		});

		for (const fieldValue of Object.values(lookup)) {
			if (fieldValue === undefined) {
				filteredData.unmatched1.push(entry);
				continue matchesLoop;
			}
		}

		const foundedMatches =
			multipleMatches === 'all'
				? findAllMatches(data2, lookup, disableDotNotation)
				: findFirstMatch(data2, lookup, disableDotNotation);

		const matches = foundedMatches.map((match) => match.entry) as INodeExecutionData[];
		foundedMatches.map((match) => matchedInInput2.add(match.index as number));

		if (matches.length) {
			filteredData.matched.push({ entry, matches });
		} else {
			filteredData.unmatched1.push(entry);
		}
	}

	data2.forEach((entry, i) => {
		if (!matchedInInput2.has(i)) {
			filteredData.unmatched2.push(entry);
		}
	});

	const same: INodeExecutionData[] = [];
	const different: INodeExecutionData[] = [];

	filteredData.matched.forEach((entryMatches) => {
		let entryCopy: INodeExecutionData | undefined;

		entryMatches.matches.forEach((match) => {
			let entryFromInput1 = entryMatches.entry.json;
			let entryFromInput2 = match.json;

			if (skipFields.length) {
				entryFromInput1 = omit(entryFromInput1, skipFields);
				entryFromInput2 = omit(entryFromInput2, skipFields);
			}
			if (isEqual(entryFromInput1, entryFromInput2)) {
				if (!entryCopy) entryCopy = match;
			} else {
				switch (options.resolve) {
					case 'preferInput1':
						different.push(entryMatches.entry);
						break;
					case 'preferInput2':
						different.push(match);
						break;
					case 'mix':
						different.push(
							combineItems(
								entryMatches.entry,
								match,
								options.preferWhenMix as string,
								options.exceptWhenMix as string,
								disableDotNotation,
							),
						);
						break;
					default:
						different.push(
							compareItems(
								entryMatches.entry,
								match,
								fieldsToMatch,
								options.resolve as string,
								skipFields,
							),
						);
				}
			}
		});
		if (!isEmpty(entryCopy)) {
			same.push(entryCopy);
		}
	});

	return [filteredData.unmatched1, same, different, filteredData.unmatched2];
}

export function checkMatchFieldsInput(data: IDataObject[]) {
	if (data.length === 1 && data[0].field1 === '' && data[0].field2 === '') {
		throw new Error(
			'You need to define at least one pair of fields in "Fields to Match" to match on',
		);
	}
	for (const [index, pair] of data.entries()) {
		if (pair.field1 === '' || pair.field2 === '') {
			throw new Error(
				`You need to define both fields in "Fields to Match" for pair ${index + 1},
				 field 1 = '${pair.field1}'
				 field 2 = '${pair.field2}'`,
			);
		}
	}
	return data as PairToMatch[];
}

export function checkInput(
	input: INodeExecutionData[],
	fields: string[],
	disableDotNotation: boolean,
	inputLabel: string,
) {
	if (input.some((item) => isEmpty(item.json))) {
		input = input.filter((item) => !isEmpty(item.json));
	}
	if (input.length === 0) {
		return input;
	}
	for (const field of fields) {
		const isPresent = (input || []).some((entry) => {
			if (disableDotNotation) {
				return entry.json.hasOwnProperty(field);
			}
			return get(entry.json, field, undefined) !== undefined;
		});
		if (!isPresent) {
			throw new Error(`Field '${field}' is not present in any of items in '${inputLabel}'`);
		}
	}
	return input;
}