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

import { Disposable, ExtensionContext, NotebookCellKind, NotebookDocument, NotebookDocumentChangeEvent, NotebookEdit, workspace, WorkspaceEdit, type NotebookCell, type NotebookDocumentWillSaveEvent } from 'vscode';
import { getCellMetadata, getVSCodeCellLanguageId, removeVSCodeCellLanguageId, setVSCodeCellLanguageId, sortObjectPropertiesRecursively, getNotebookMetadata } from './serializers';
import { CellMetadata } from './common';
import type * as nbformat from '@jupyterlab/nbformat';
import { generateUuid } from './helper';

const noop = () => {
	//
};

/**
 * Code here is used to ensure the Notebook Model is in sync the ipynb JSON file.
 * E.g. assume you add a new cell, this new cell will not have any metadata at all.
 * However when we save the ipynb, the metadata will be an empty object `{}`.
 * Now thats completely different from the metadata os being `empty/undefined` in the model.
 * As a result, when looking at things like diff view or accessing metadata, we'll see differences.
*
* This code ensures that the model is in sync with the ipynb file.
*/
export const pendingNotebookCellModelUpdates = new WeakMap<NotebookDocument, Set<Thenable<void>>>();
export function activate(context: ExtensionContext) {
	workspace.onDidChangeNotebookDocument(onDidChangeNotebookCells, undefined, context.subscriptions);
	workspace.onWillSaveNotebookDocument(waitForPendingModelUpdates, undefined, context.subscriptions);
}

type NotebookDocumentChangeEventEx = Omit<NotebookDocumentChangeEvent, 'metadata'>;
let mergedEvents: NotebookDocumentChangeEventEx | undefined;
let timer: NodeJS.Timeout;

function triggerDebouncedNotebookDocumentChangeEvent() {
	if (timer) {
		clearTimeout(timer);
	}
	if (!mergedEvents) {
		return;
	}
	const args = mergedEvents;
	mergedEvents = undefined;
	onDidChangeNotebookCells(args);
}

export function debounceOnDidChangeNotebookDocument() {
	const disposable = workspace.onDidChangeNotebookDocument(e => {
		if (!isSupportedNotebook(e.notebook)) {
			return;
		}
		if (!mergedEvents) {
			mergedEvents = e;
		} else if (mergedEvents.notebook === e.notebook) {
			// Same notebook, we can merge the updates.
			mergedEvents = {
				cellChanges: e.cellChanges.concat(mergedEvents.cellChanges),
				contentChanges: e.contentChanges.concat(mergedEvents.contentChanges),
				notebook: e.notebook
			};
		} else {
			// Different notebooks, we cannot merge the updates.
			// Hence we need to process the previous notebook and start a new timer for the new notebook.
			triggerDebouncedNotebookDocumentChangeEvent();
			// Start a new timer for the new notebook.
			mergedEvents = e;
		}
		if (timer) {
			clearTimeout(timer);
		}
		timer = setTimeout(triggerDebouncedNotebookDocumentChangeEvent, 200);
	});


	return Disposable.from(disposable, new Disposable(() => {
		clearTimeout(timer);
	}));
}

function isSupportedNotebook(notebook: NotebookDocument) {
	return notebook.notebookType === 'jupyter-notebook';
}

function waitForPendingModelUpdates(e: NotebookDocumentWillSaveEvent) {
	if (!isSupportedNotebook(e.notebook)) {
		return;
	}

	triggerDebouncedNotebookDocumentChangeEvent();
	const promises = pendingNotebookCellModelUpdates.get(e.notebook);
	if (!promises) {
		return;
	}
	e.waitUntil(Promise.all(promises));
}

function cleanup(notebook: NotebookDocument, promise: PromiseLike<void>) {
	const pendingUpdates = pendingNotebookCellModelUpdates.get(notebook);
	if (pendingUpdates) {
		pendingUpdates.delete(promise);
		if (!pendingUpdates.size) {
			pendingNotebookCellModelUpdates.delete(notebook);
		}
	}
}
function trackAndUpdateCellMetadata(notebook: NotebookDocument, updates: { cell: NotebookCell; metadata: CellMetadata & { vscode?: { languageId: string } } }[]) {
	const pendingUpdates = pendingNotebookCellModelUpdates.get(notebook) ?? new Set<Thenable<void>>();
	pendingNotebookCellModelUpdates.set(notebook, pendingUpdates);
	const edit = new WorkspaceEdit();
	updates.forEach(({ cell, metadata }) => {
		const newMetadata = { ...cell.metadata, ...metadata };
		if (!metadata.execution_count && newMetadata.execution_count) {
			newMetadata.execution_count = null;
		}
		if (!metadata.attachments && newMetadata.attachments) {
			delete newMetadata.attachments;
		}
		edit.set(cell.notebook.uri, [NotebookEdit.updateCellMetadata(cell.index, sortObjectPropertiesRecursively(newMetadata))]);
	});
	const promise = workspace.applyEdit(edit).then(noop, noop);
	pendingUpdates.add(promise);
	const clean = () => cleanup(notebook, promise);
	promise.then(clean, clean);
}

const pendingCellUpdates = new WeakSet<NotebookCell>();
function onDidChangeNotebookCells(e: NotebookDocumentChangeEventEx) {
	if (!isSupportedNotebook(e.notebook)) {
		return;
	}

	const notebook = e.notebook;
	const notebookMetadata = getNotebookMetadata(e.notebook);

	// use the preferred language from document metadata or the first cell language as the notebook preferred cell language
	const preferredCellLanguage = notebookMetadata.metadata?.language_info?.name;
	const updates: { cell: NotebookCell; metadata: CellMetadata & { vscode?: { languageId: string } } }[] = [];
	// When we change the language of a cell,
	// Ensure the metadata in the notebook cell has been updated as well,
	// Else model will be out of sync with ipynb https://github.com/microsoft/vscode/issues/207968#issuecomment-2002858596
	e.cellChanges.forEach(e => {
		if (!preferredCellLanguage || e.cell.kind !== NotebookCellKind.Code) {
			return;
		}
		const currentMetadata = e.metadata ? getCellMetadata({ metadata: e.metadata }) : getCellMetadata({ cell: e.cell });
		const languageIdInMetadata = getVSCodeCellLanguageId(currentMetadata);
		const metadata: CellMetadata = JSON.parse(JSON.stringify(currentMetadata));
		metadata.metadata = metadata.metadata || {};
		let metadataUpdated = false;
		if (e.executionSummary?.executionOrder && typeof e.executionSummary.success === 'boolean' && currentMetadata.execution_count !== e.executionSummary?.executionOrder) {
			metadata.execution_count = e.executionSummary.executionOrder;
			metadataUpdated = true;
		} else if (!e.executionSummary && !e.metadata && e.outputs?.length === 0 && currentMetadata.execution_count) {
			// Clear all (user hit clear all).
			// NOTE: At this point we're updating the `execution_count` in metadata to `null`.
			// Thus this is a change in metadata, which we will need to update in the model.
			metadata.execution_count = null;
			metadataUpdated = true;
			// Note: We will get another event for this, see below for the check.
			// track the fact that we're expecting an update for this cell.
			pendingCellUpdates.add(e.cell);
		} else if ((!e.executionSummary || (!e.executionSummary?.executionOrder && !e.executionSummary?.success && !e.executionSummary?.timing))
			&& !e.metadata && !e.outputs && currentMetadata.execution_count && pendingCellUpdates.has(e.cell)) {
			// This is a result of the cell being cleared (i.e. we perfomed an update request and this is now the update event).
			metadata.execution_count = null;
			metadataUpdated = true;
			pendingCellUpdates.delete(e.cell);
		} else if (!e.executionSummary?.executionOrder && !e.executionSummary?.success && !e.executionSummary?.timing
			&& !e.metadata && !e.outputs && currentMetadata.execution_count && !pendingCellUpdates.has(e.cell)) {
			// This is a result of the cell without outupts but has execution count being cleared
			// Create two cells, one that produces output and one that doesn't. Run both and then clear the output or all cells.
			// This condition will be satisfied for first cell without outputs.
			metadata.execution_count = null;
			metadataUpdated = true;
		}

		if (e.document?.languageId && e.document?.languageId !== preferredCellLanguage && e.document?.languageId !== languageIdInMetadata) {
			setVSCodeCellLanguageId(metadata, e.document.languageId);
			metadataUpdated = true;
		} else if (e.document?.languageId && e.document.languageId === preferredCellLanguage && languageIdInMetadata) {
			removeVSCodeCellLanguageId(metadata);
			metadataUpdated = true;
		} else if (e.document?.languageId && e.document.languageId === preferredCellLanguage && e.document.languageId === languageIdInMetadata) {
			removeVSCodeCellLanguageId(metadata);
			metadataUpdated = true;
		}

		if (metadataUpdated) {
			updates.push({ cell: e.cell, metadata });
		}
	});

	// Ensure all new cells in notebooks with nbformat >= 4.5 have an id.
	// Details of the spec can be found here https://jupyter.org/enhancement-proposals/62-cell-id/cell-id.html#
	e.contentChanges.forEach(change => {
		change.addedCells.forEach(cell => {
			// When ever a cell is added, always update the metadata
			// as metadata is always an empty `{}` in ipynb JSON file
			const cellMetadata = getCellMetadata({ cell });

			// Avoid updating the metadata if it's not required.
			if (cellMetadata.metadata) {
				if (!isCellIdRequired(notebookMetadata)) {
					return;
				}
				if (isCellIdRequired(notebookMetadata) && cellMetadata?.id) {
					return;
				}
			}

			// Don't edit the metadata directly, always get a clone (prevents accidental singletons and directly editing the objects).
			const metadata: CellMetadata = { ...JSON.parse(JSON.stringify(cellMetadata || {})) };
			metadata.metadata = metadata.metadata || {};

			if (isCellIdRequired(notebookMetadata) && !cellMetadata?.id) {
				metadata.id = generateCellId(e.notebook);
			}
			updates.push({ cell, metadata });
		});
	});

	if (updates.length) {
		trackAndUpdateCellMetadata(notebook, updates);
	}
}


/**
 * Cell ids are required in notebooks only in notebooks with nbformat >= 4.5
 */
function isCellIdRequired(metadata: Pick<Partial<nbformat.INotebookContent>, 'nbformat' | 'nbformat_minor'>) {
	if ((metadata.nbformat || 0) >= 5) {
		return true;
	}
	if ((metadata.nbformat || 0) === 4 && (metadata.nbformat_minor || 0) >= 5) {
		return true;
	}
	return false;
}

function generateCellId(notebook: NotebookDocument) {
	while (true) {
		// Details of the id can be found here https://jupyter.org/enhancement-proposals/62-cell-id/cell-id.html#adding-an-id-field,
		// & here https://jupyter.org/enhancement-proposals/62-cell-id/cell-id.html#updating-older-formats
		const id = generateUuid().replace(/-/g, '').substring(0, 8);
		let duplicate = false;
		for (let index = 0; index < notebook.cellCount; index++) {
			const cell = notebook.cellAt(index);
			const existingId = getCellMetadata({ cell })?.id;
			if (!existingId) {
				continue;
			}
			if (existingId === id) {
				duplicate = true;
				break;
			}
		}
		if (!duplicate) {
			return id;
		}
	}
}