// <nowiki>

/*
A user script that alerts you with a yellow banner at the top of a User Talk page if more than 3% of recent user talk diffs are self-deletions, with exceptions for some edit summary keywords such as "archiving".

Useful for detecting if a WP:PERM applicant is whitewashing their User Talk page by removing warnings without archiving them.
*/

class ErasedSectionsDetector {
	constructor( mw, $ ) {
		this.mw = mw;
		this.$ = $;
	}

	async execute() {
		if ( !this.shouldRunOnThisPage() ) {
			return;
		}
		const title = this.mw.config.get( 'wgPageName' ).replace( /_/g, ' ' );
		this.revisions = await this.getRevisions( title );
		const totalRevisionCount = this.revisions.length;
		this.addDiffsToRevisions();
		this.filterForRevisionsByThisEditorOnly();
		this.filterForContentRemoval();
		this.filterOutReasonableEditSummaries();
		this.expandBlankEditSummaries();
		const negativeDiffCount = this.revisions.length;
		const deletionPercent = negativeDiffCount / totalRevisionCount;
		if ( deletionPercent > 0.03 ) {
			this.addHtml( negativeDiffCount, totalRevisionCount );
			this.listenForShowDiffsClick();
		}
	}

	/**
	 * Add a message to blank edit summaries. This is so the hyperlink can be clicked.
	 */
	expandBlankEditSummaries() {
		this.revisions = this.revisions.map( function ( revision ) {
			if ( revision.comment === '' ) {
				revision.comment = '[no edit summary]';
			}
			return revision;
		} );
	}

	listenForShowDiffsClick() {
		this.$( '#ErasedSectionsDetector-SeeDiffs' ).on( 'click', function () {
			this.$( '#ErasedSectionsDetector-Diffs' ).toggle();
		}.bind( this ) );
	}

	addHtml( negativeDiffCount, totalRevisionCount ) {
		let html = `
			<div class="ErasedSectionsDetector">
				<div style="background-color: yellow">
					<span style="font-weight:bold">Warning:</span> This user has removed content from this page (probably without archiving it) in ${ negativeDiffCount } of the last ${ totalRevisionCount } revisions. <a id="ErasedSectionsDetector-SeeDiffs">Click here</a> to see diffs.
				</div>
				
				<div id="ErasedSectionsDetector-Diffs" style="border: 1px solid black; font-size: 80%; display: none;">
					<ul>
		`;

		for ( const revision of this.revisions ) {
			html += `
						<li>
							<a href="w/index.php?title=${ encodeURIComponent( this.mw.config.get( 'wgPageName' ) ) }&diff=prev&oldid=${ revision.revid }">
								${ revision.comment }
							</a>
						</li>
			`;
		}

		html += `
					</ul>
				</div>
			</div>
		`;

		this.$( '#contentSub2' ).after( html );
	}

	filterForContentRemoval() {
		this.revisions = this.revisions.filter( ( revision ) => revision.diff < 0 );
	}

	filterForRevisionsByThisEditorOnly() {
		const thisEditor = this.mw.config.get( 'wgTitle' );
		this.revisions = this.revisions.filter( ( revision ) => revision.user === thisEditor );
	}

	filterOutReasonableEditSummaries() {
		const keywordsToIgnore = [
			'arch', // arch, archive, archiving, OneClickArchiver
			'bot mes', // mesg, message
			'mass mes',
			'newsletter'
		];
		for ( let keyword of keywordsToIgnore ) {
			this.revisions = this.revisions.filter( function ( revision ) {
				keyword = keyword.toLowerCase();
				const editSummary = revision.comment.toLowerCase();
				return !editSummary.includes( keyword );
			} );
		}
	}

	/**
	 * Given the Action API output of query revisions as a JavaScript object, add to this object a field called "diff" that is the difference +/- in size of that diff compared to the next oldest diff.
	 */
	addDiffsToRevisions() {
		const len = this.revisions.length;
		let lastRevisionSize = this.revisions[ len - 1 ].size;
		// need to store the OLDER revision's size in a buffer to compute a diff, so iterate BACKWARDS
		for ( let i = ( len - 2 ); i >= 0; i-- ) {
			const thisRevisionSize = this.revisions[ i ].size;
			this.revisions[ i ].diff = thisRevisionSize - lastRevisionSize;
			lastRevisionSize = thisRevisionSize;
		}
	}

	async getRevisions( title ) {
		const api = new this.mw.Api();
		const response = await api.get( {
			action: 'query',
			format: 'json',
			prop: 'revisions',
			titles: title,
			formatversion: '2',
			rvprop: 'comment|size|user|ids',
			rvslots: '',
			rvlimit: '500', // get 500 revisions
			rvdir: 'older' // get newest revisions (enumerate towards older entries)
		} );
		return response.query.pages[ 0 ].revisions;
	}

	shouldRunOnThisPage() {
		const isViewing = this.mw.config.get( 'wgAction' ) === 'view';
		if ( !isViewing ) {
			return false;
		}

		const isDiff = this.mw.config.get( 'wgDiffNewId' );
		if ( isDiff ) {
			return false;
		}

		const isDeletedPage = !this.mw.config.get( 'wgCurRevisionId' );
		if ( isDeletedPage ) {
			return false;
		}

		const namespace = this.mw.config.get( 'wgNamespaceNumber' );
		const isUserTalkNamespace = [ 3 ].includes( namespace );
		if ( !isUserTalkNamespace ) {
			return false;
		}

		const isSubPage = this.mw.config.get( 'wgPageName' ).includes( '/' );
		if ( isSubPage ) {
			return;
		}

		return true;
	}
}

$( async function () {
	await mw.loader.using( [ 'mediawiki.api' ], async () => {
		await ( new ErasedSectionsDetector( mw, $ ) ).execute();
	} );
} );

// </nowiki>