import BaseModel, { ModelType } from '../BaseModel';
import { RevisionEntity } from '../services/database/types';
import BaseItem from './BaseItem';
const DiffMatchPatch = require('diff-match-patch');
const ArrayUtils = require('../ArrayUtils.js');
import JoplinError from '../JoplinError';
const { sprintf } = require('sprintf-js');

const dmp = new DiffMatchPatch();

export interface ObjectPatch {
	new: Record<string, any>;
	deleted: string[];
}

export default class Revision extends BaseItem {
	static tableName() {
		return 'revisions';
	}

	static modelType() {
		return BaseModel.TYPE_REVISION;
	}

	public static createTextPatchLegacy(oldText: string, newText: string): string {
		return dmp.patch_toText(dmp.patch_make(oldText, newText));
	}

	public static createTextPatch(oldText: string, newText: string): string {
		// Note that, once parsed, the resulting object will not exactly be like
		// a dmp patch object. This is because the library overrides the
		// toString() prototype function of the dmp patch object, and uses it in
		// certain functions. For example, in patch_toText(). It means that when
		// calling patch_toText() with an object that has been JSON-stringified
		// and JSON-parsed, it will not work.
		//
		// This is mostly fine for our purpose. It's only a problem in
		// Revision.patchStats() because it was based on parsing the GNU diff
		// as returned by patch_toText().
		return JSON.stringify(dmp.patch_make(oldText, newText));
	}

	public static applyTextPatchLegacy(text: string, patch: string): string {
		patch = dmp.patch_fromText(patch);
		const result = dmp.patch_apply(patch, text);
		if (!result || !result.length) throw new Error('Could not apply patch');
		return result[0];
	}

	private static isLegacyPatch(patch: string): boolean {
		return patch && patch.indexOf('@@') === 0;
	}

	private static isNewPatch(patch: string): boolean {
		if (!patch) return true;
		return patch.indexOf('[{') === 0 || patch === '[]';
	}

	public static applyTextPatch(text: string, patch: string): string {
		if (this.isLegacyPatch(patch)) {
			return this.applyTextPatchLegacy(text, patch);
		} else {
			// An empty patch should be '[]', but legacy data may be just "".
			// However an empty string would make JSON.parse fail so we set it
			// to '[]'.
			const result = dmp.patch_apply(this.parsePatch(patch), text);
			if (!result || !result.length) throw new Error('Could not apply patch');
			return result[0];
		}
	}

	public static isEmptyRevision(rev: RevisionEntity): boolean {
		if (this.isLegacyPatch(rev.title_diff) && rev.title_diff) return false;
		if (this.isLegacyPatch(rev.body_diff) && rev.body_diff) return false;

		if (this.isNewPatch(rev.title_diff) && rev.title_diff && rev.title_diff !== '[]') return false;
		if (this.isNewPatch(rev.body_diff) && rev.body_diff && rev.body_diff !== '[]') return false;

		const md = rev.metadata_diff ? JSON.parse(rev.metadata_diff) : {};
		if (md.new && Object.keys(md.new).length) return false;
		if (md.deleted && Object.keys(md.deleted).length) return false;

		return true;
	}

	public static createObjectPatch(oldObject: any, newObject: any) {
		if (!oldObject) oldObject = {};

		const output: ObjectPatch = {
			new: {},
			deleted: [],
		};

		for (const k in newObject) {
			if (!newObject.hasOwnProperty(k)) continue;
			if (oldObject[k] === newObject[k]) continue;
			output.new[k] = newObject[k];
		}

		for (const k in oldObject) {
			if (!oldObject.hasOwnProperty(k)) continue;
			if (!(k in newObject)) output.deleted.push(k);
		}

		return JSON.stringify(output);
	}

	// We need to sanitise the object patch because it seems some are broken and
	// may contain new lines: https://github.com/laurent22/joplin/issues/6209
	private static sanitizeObjectPatch(patch: string): string {
		return patch.replace(/[\n\r]/g, '');
	}

	public static applyObjectPatch(object: any, patch: string) {
		const parsedPatch: ObjectPatch = JSON.parse(this.sanitizeObjectPatch(patch));
		const output = Object.assign({}, object);

		for (const k in parsedPatch.new) {
			output[k] = parsedPatch.new[k];
		}

		for (let i = 0; i < parsedPatch.deleted.length; i++) {
			delete output[parsedPatch.deleted[i]];
		}

		return output;
	}

	// Turn a new-style patch into an approximation of a GNU diff format.
	// Approximation, because the only goal is to put "+" or "-" before each
	// line, so that it can be processed by patchStats().
	private static newPatchToDiffFormat(patch: string): string {
		const changeList: string[] = [];
		const patchArray = this.parsePatch(patch);
		for (const patchItem of patchArray) {
			for (const d of patchItem.diffs) {
				if (d[0] !== 0) changeList.push(d[0] < 0 ? `-${d[1].replace(/[\n\r]/g, ' ')}` : `+${d[1].trim().replace(/[\n\r]/g, ' ')}`);
			}
		}
		return changeList.join('\n');
	}

	public static patchStats(patch: string) {
		if (typeof patch === 'object') throw new Error('Not implemented');

		if (this.isNewPatch(patch)) {
			try {
				patch = this.newPatchToDiffFormat(patch);
			} catch (error) {
				// Normally it should work but if it doesn't we don't want it to
				// crash the app since it's just presentational. But log an
				// error so that it can eventually be fixed.
				console.error('Could not generate diff:', error, patch);
				return { added: 0, removed: 0 };
			}
		}

		const countChars = (diffLine: string) => {
			return unescape(diffLine).length - 1;
		};

		const lines = patch.split('\n');
		let added = 0;
		let removed = 0;

		for (const line of lines) {
			if (line.indexOf('-') === 0) {
				removed += countChars(line);
				continue;
			}

			if (line.indexOf('+') === 0) {
				added += countChars(line);
				continue;
			}
		}

		return {
			added: added,
			removed: removed,
		};
	}

	static revisionPatchStatsText(rev: RevisionEntity) {
		const titleStats = this.patchStats(rev.title_diff);
		const bodyStats = this.patchStats(rev.body_diff);
		const total = {
			added: titleStats.added + bodyStats.added,
			removed: titleStats.removed + bodyStats.removed,
		};

		const output = [];
		if (total.removed) output.push(`-${total.removed}`);
		output.push(`+${total.added}`);
		return output.join(', ');
	}

	static async countRevisions(itemType: ModelType, itemId: string) {
		const r = await this.db().selectOne('SELECT count(*) as total FROM revisions WHERE item_type = ? AND item_id = ?', [itemType, itemId]);

		return r ? r.total : 0;
	}

	static latestRevision(itemType: ModelType, itemId: string) {
		return this.modelSelectOne('SELECT * FROM revisions WHERE item_type = ? AND item_id = ? ORDER BY item_updated_time DESC LIMIT 1', [itemType, itemId]);
	}

	static allByType(itemType: ModelType, itemId: string) {
		return this.modelSelectAll('SELECT * FROM revisions WHERE item_type = ? AND item_id = ? ORDER BY item_updated_time ASC', [itemType, itemId]);
	}

	static async itemsWithRevisions(itemType: ModelType, itemIds: string[]) {
		if (!itemIds.length) return [];
		const rows = await this.db().selectAll(`SELECT distinct item_id FROM revisions WHERE item_type = ? AND item_id IN ("${itemIds.join('","')}")`, [itemType]);

		return rows.map((r: RevisionEntity) => r.item_id);
	}

	static async itemsWithNoRevisions(itemType: ModelType, itemIds: string[]) {
		const withRevs = await this.itemsWithRevisions(itemType, itemIds);
		const output = [];
		for (let i = 0; i < itemIds.length; i++) {
			if (withRevs.indexOf(itemIds[i]) < 0) output.push(itemIds[i]);
		}
		return ArrayUtils.unique(output);
	}

	static moveRevisionToTop(revision: RevisionEntity, revs: RevisionEntity[]) {
		let targetIndex = -1;
		for (let i = revs.length - 1; i >= 0; i--) {
			const rev = revs[i];
			if (rev.id === revision.id) {
				targetIndex = i;
				break;
			}
		}

		if (targetIndex < 0) throw new Error(`Could not find revision: ${revision.id}`);

		if (targetIndex !== revs.length - 1) {
			revs = revs.slice();
			const toTop = revs[targetIndex];
			revs.splice(targetIndex, 1);
			revs.push(toTop);
		}

		return revs;
	}

	// Note: revs must be sorted by update_time ASC (as returned by allByType)
	public static async mergeDiffs(revision: RevisionEntity, revs: RevisionEntity[] = null) {
		if (!('encryption_applied' in revision) || !!revision.encryption_applied) throw new JoplinError('Target revision is encrypted', 'revision_encrypted');

		if (!revs) {
			revs = await this.modelSelectAll('SELECT * FROM revisions WHERE item_type = ? AND item_id = ? AND item_updated_time <= ? ORDER BY item_updated_time ASC', [revision.item_type, revision.item_id, revision.item_updated_time]);
		} else {
			revs = revs.slice();
		}

		// Handle rare case where two revisions have been created at exactly the same millisecond
		// Also handle even rarer case where a rev and its parent have been created at the
		// same milliseconds. All code below expects target revision to be on top.
		revs = this.moveRevisionToTop(revision, revs);

		const output = {
			title: '',
			body: '',
			metadata: {},
		};

		// Build up the list of revisions that are parents of the target revision.
		const revIndexes = [revs.length - 1];
		let parentId = revision.parent_id;
		for (let i = revs.length - 2; i >= 0; i--) {
			const rev = revs[i];
			if (rev.id !== parentId) continue;
			parentId = rev.parent_id;
			revIndexes.push(i);
		}
		revIndexes.reverse();

		for (const revIndex of revIndexes) {
			const rev = revs[revIndex];
			if (rev.encryption_applied) throw new JoplinError(sprintf('Revision "%s" is encrypted', rev.id), 'revision_encrypted');
			output.title = this.applyTextPatch(output.title, rev.title_diff);
			output.body = this.applyTextPatch(output.body, rev.body_diff);
			try {
				output.metadata = this.applyObjectPatch(output.metadata, rev.metadata_diff);
			} catch (error) {
				error.message = `Revision ${rev.id}: Could not apply patch: ${error.message}: ${rev.metadata_diff}`;
				throw error;
			}
		}

		return output;
	}

	static async deleteOldRevisions(ttl: number) {
		// When deleting old revisions, we need to make sure that the oldest surviving revision
		// is a "merged" one (as opposed to a diff from a now deleted revision). So every time
		// we deleted a revision, we need to find if there's a corresponding surviving revision
		// and modify that revision into a "merged" one.

		const cutOffDate = Date.now() - ttl;
		const revisions = await this.modelSelectAll('SELECT * FROM revisions WHERE item_updated_time < ? ORDER BY item_updated_time DESC', [cutOffDate]);
		const doneItems: Record<string, boolean> = {};

		for (const rev of revisions) {
			const doneKey = `${rev.item_type}_${rev.item_id}`;
			if (doneItems[doneKey]) continue;

			const keptRev = await this.modelSelectOne('SELECT * FROM revisions WHERE item_updated_time >= ? AND item_type = ? AND item_id = ? ORDER BY item_updated_time ASC LIMIT 1', [cutOffDate, rev.item_type, rev.item_id]);

			try {
				const deleteQueryCondition = 'item_updated_time < ? AND item_id = ?';
				const deleteQueryParams = [cutOffDate, rev.item_id];
				const deleteQuery = { sql: `DELETE FROM revisions WHERE ${deleteQueryCondition}`, params: deleteQueryParams };

				if (!keptRev) {
					const hasEncrypted = await this.modelSelectOne(`SELECT * FROM revisions WHERE encryption_applied = 1 AND ${deleteQueryCondition}`, deleteQueryParams);
					if (hasEncrypted) throw new JoplinError('One of the revision to be deleted is encrypted', 'revision_encrypted');
					await this.db().transactionExecBatch([deleteQuery]);
				} else {
					// Note: we don't need to check for encrypted rev here because
					// mergeDiff will already throw the revision_encrypted exception
					// if a rev is encrypted.
					const merged = await this.mergeDiffs(keptRev);

					const queries = [deleteQuery, { sql: 'UPDATE revisions SET title_diff = ?, body_diff = ?, metadata_diff = ? WHERE id = ?', params: [this.createTextPatch('', merged.title), this.createTextPatch('', merged.body), this.createObjectPatch({}, merged.metadata), keptRev.id] }];

					await this.db().transactionExecBatch(queries);
				}
			} catch (error) {
				if (error.code === 'revision_encrypted') {
					this.logger().info(`Aborted deletion of old revisions for item "${rev.item_id}" (rev "${rev.id}") because one of the revisions is still encrypted`, error);
				} else {
					throw error;
				}
			}

			doneItems[doneKey] = true;
		}
	}

	static async revisionExists(itemType: ModelType, itemId: string, updatedTime: number) {
		const existingRev = await Revision.latestRevision(itemType, itemId);
		return existingRev && existingRev.item_updated_time === updatedTime;
	}

	private static parsePatch(patch: any): any[] {
		return patch ? JSON.parse(patch) : [];
	}

}