/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { AutorunObserver } from 'vs/base/common/observableInternal/autorun';
import { IObservable, ObservableValue, TransactionImpl } from 'vs/base/common/observableInternal/base';
import { Derived } from 'vs/base/common/observableInternal/derived';
import { FromEventObservable } from 'vs/base/common/observableInternal/utils';

let globalObservableLogger: IObservableLogger | undefined;

export function setLogger(logger: IObservableLogger): void {
	globalObservableLogger = logger;
}

export function getLogger(): IObservableLogger | undefined {
	return globalObservableLogger;
}

interface IChangeInformation {
	oldValue: unknown;
	newValue: unknown;
	change: unknown;
	didChange: boolean;
	hadValue: boolean;
}

export interface IObservableLogger {
	handleObservableChanged(observable: ObservableValue<any, any>, info: IChangeInformation): void;
	handleFromEventObservableTriggered(observable: FromEventObservable<any, any>, info: IChangeInformation): void;

	handleAutorunCreated(autorun: AutorunObserver): void;
	handleAutorunTriggered(autorun: AutorunObserver): void;
	handleAutorunFinished(autorun: AutorunObserver): void;

	handleDerivedCreated(observable: Derived<any>): void;
	handleDerivedRecomputed(observable: Derived<any>, info: IChangeInformation): void;

	handleBeginTransaction(transaction: TransactionImpl): void;
	handleEndTransaction(): void;
}

export class ConsoleObservableLogger implements IObservableLogger {
	private indentation = 0;

	private textToConsoleArgs(text: ConsoleText): unknown[] {
		return consoleTextToArgs([
			normalText(repeat('|  ', this.indentation)),
			text,
		]);
	}

	private formatInfo(info: IChangeInformation): ConsoleText[] {
		if (!info.hadValue) {
			return [
				normalText(` `),
				styled(formatValue(info.newValue, 60), {
					color: 'green',
				}),
				normalText(` (initial)`),
			];
		}
		return info.didChange
			? [
				normalText(` `),
				styled(formatValue(info.oldValue, 70), {
					color: 'red',
					strikeThrough: true,
				}),
				normalText(` `),
				styled(formatValue(info.newValue, 60), {
					color: 'green',
				}),
			]
			: [normalText(` (unchanged)`)];
	}

	handleObservableChanged(observable: IObservable<unknown, unknown>, info: IChangeInformation): void {
		console.log(...this.textToConsoleArgs([
			formatKind('observable value changed'),
			styled(observable.debugName, { color: 'BlueViolet' }),
			...this.formatInfo(info),
		]));
	}

	private readonly changedObservablesSets = new WeakMap<object, Set<IObservable<any, any>>>();

	formatChanges(changes: Set<IObservable<any, any>>): ConsoleText | undefined {
		if (changes.size === 0) {
			return undefined;
		}
		return styled(
			' (changed deps: ' +
			[...changes].map((o) => o.debugName).join(', ') +
			')',
			{ color: 'gray' }
		);
	}

	handleDerivedCreated(derived: Derived<unknown>): void {
		const existingHandleChange = derived.handleChange;
		this.changedObservablesSets.set(derived, new Set());
		derived.handleChange = (observable, change) => {
			this.changedObservablesSets.get(derived)!.add(observable);
			return existingHandleChange.apply(derived, [observable, change]);
		};
	}

	handleDerivedRecomputed(derived: Derived<unknown>, info: IChangeInformation): void {
		const changedObservables = this.changedObservablesSets.get(derived)!;
		console.log(...this.textToConsoleArgs([
			formatKind('derived recomputed'),
			styled(derived.debugName, { color: 'BlueViolet' }),
			...this.formatInfo(info),
			this.formatChanges(changedObservables),
			{ data: [{ fn: derived._debugNameData.referenceFn ?? derived._computeFn }] }
		]));
		changedObservables.clear();
	}

	handleFromEventObservableTriggered(observable: FromEventObservable<any, any>, info: IChangeInformation): void {
		console.log(...this.textToConsoleArgs([
			formatKind('observable from event triggered'),
			styled(observable.debugName, { color: 'BlueViolet' }),
			...this.formatInfo(info),
			{ data: [{ fn: observable._getValue }] }
		]));
	}

	handleAutorunCreated(autorun: AutorunObserver): void {
		const existingHandleChange = autorun.handleChange;
		this.changedObservablesSets.set(autorun, new Set());
		autorun.handleChange = (observable, change) => {
			this.changedObservablesSets.get(autorun)!.add(observable);
			return existingHandleChange.apply(autorun, [observable, change]);
		};
	}

	handleAutorunTriggered(autorun: AutorunObserver): void {
		const changedObservables = this.changedObservablesSets.get(autorun)!;
		console.log(...this.textToConsoleArgs([
			formatKind('autorun'),
			styled(autorun.debugName, { color: 'BlueViolet' }),
			this.formatChanges(changedObservables),
			{ data: [{ fn: autorun._debugNameData.referenceFn ?? autorun._runFn }] }
		]));
		changedObservables.clear();
		this.indentation++;
	}

	handleAutorunFinished(autorun: AutorunObserver): void {
		this.indentation--;
	}

	handleBeginTransaction(transaction: TransactionImpl): void {
		let transactionName = transaction.getDebugName();
		if (transactionName === undefined) {
			transactionName = '';
		}
		console.log(...this.textToConsoleArgs([
			formatKind('transaction'),
			styled(transactionName, { color: 'BlueViolet' }),
			{ data: [{ fn: transaction._fn }] }
		]));
		this.indentation++;
	}

	handleEndTransaction(): void {
		this.indentation--;
	}
}

type ConsoleText =
	| (ConsoleText | undefined)[]
	| { text: string; style: string; data?: unknown[] }
	| { data: unknown[] };

function consoleTextToArgs(text: ConsoleText): unknown[] {
	const styles = new Array<any>();
	const data: unknown[] = [];
	let firstArg = '';

	function process(t: ConsoleText): void {
		if ('length' in t) {
			for (const item of t) {
				if (item) {
					process(item);
				}
			}
		} else if ('text' in t) {
			firstArg += `%c${t.text}`;
			styles.push(t.style);
			if (t.data) {
				data.push(...t.data);
			}
		} else if ('data' in t) {
			data.push(...t.data);
		}
	}

	process(text);

	const result = [firstArg, ...styles];
	result.push(...data);
	return result;
}

function normalText(text: string): ConsoleText {
	return styled(text, { color: 'black' });
}

function formatKind(kind: string): ConsoleText {
	return styled(padStr(`${kind}: `, 10), { color: 'black', bold: true });
}

function styled(
	text: string,
	options: { color: string; strikeThrough?: boolean; bold?: boolean } = {
		color: 'black',
	}
): ConsoleText {
	function objToCss(styleObj: Record<string, string>): string {
		return Object.entries(styleObj).reduce(
			(styleString, [propName, propValue]) => {
				return `${styleString}${propName}:${propValue};`;
			},
			''
		);
	}

	const style: Record<string, string> = {
		color: options.color,
	};
	if (options.strikeThrough) {
		style['text-decoration'] = 'line-through';
	}
	if (options.bold) {
		style['font-weight'] = 'bold';
	}

	return {
		text,
		style: objToCss(style),
	};
}

function formatValue(value: unknown, availableLen: number): string {
	switch (typeof value) {
		case 'number':
			return '' + value;
		case 'string':
			if (value.length + 2 <= availableLen) {
				return `"${value}"`;
			}
			return `"${value.substr(0, availableLen - 7)}"+...`;

		case 'boolean':
			return value ? 'true' : 'false';
		case 'undefined':
			return 'undefined';
		case 'object':
			if (value === null) {
				return 'null';
			}
			if (Array.isArray(value)) {
				return formatArray(value, availableLen);
			}
			return formatObject(value, availableLen);
		case 'symbol':
			return value.toString();
		case 'function':
			return `[[Function${value.name ? ' ' + value.name : ''}]]`;
		default:
			return '' + value;
	}
}

function formatArray(value: unknown[], availableLen: number): string {
	let result = '[ ';
	let first = true;
	for (const val of value) {
		if (!first) {
			result += ', ';
		}
		if (result.length - 5 > availableLen) {
			result += '...';
			break;
		}
		first = false;
		result += `${formatValue(val, availableLen - result.length)}`;
	}
	result += ' ]';
	return result;
}

function formatObject(value: object, availableLen: number): string {
	let result = '{ ';
	let first = true;
	for (const [key, val] of Object.entries(value)) {
		if (!first) {
			result += ', ';
		}
		if (result.length - 5 > availableLen) {
			result += '...';
			break;
		}
		first = false;
		result += `${key}: ${formatValue(val, availableLen - result.length)}`;
	}
	result += ' }';
	return result;
}

function repeat(str: string, count: number): string {
	let result = '';
	for (let i = 1; i <= count; i++) {
		result += str;
	}
	return result;
}

function padStr(str: string, length: number): string {
	while (str.length < length) {
		str += ' ';
	}
	return str;
}