import chalk from "chalk";
import fs from "node:fs";
import { promisify } from "node:util";
import zlib from "node:zlib";
import { exec as nodeExec } from "node:child_process";
import isCleanWorkingDir from "./lib/isCleanWorkingDir.js";

const gzip = promisify( zlib.gzip );
const exec = promisify( nodeExec );

async function getBranchName() {
	const { stdout } = await exec( "git rev-parse --abbrev-ref HEAD" );
	return stdout.trim();
}

async function getCache( loc ) {
	try {
		const contents = await fs.promises.readFile( loc, "utf8" );
		return JSON.parse( contents );
	} catch ( err ) {
		return {};
	}
}

function saveCache( loc, cache ) {
	return fs.promises.writeFile( loc, JSON.stringify( cache ) );
}

function compareSizes( existing, current, padLength ) {
	if ( typeof current !== "number" ) {
		return chalk.grey( `${existing}`.padStart( padLength ) );
	}
	const delta = current - existing;
	if ( delta > 0 ) {
		return chalk.red( `+${delta}`.padStart( padLength ) );
	}
	return chalk.green( `${delta}`.padStart( padLength ) );
}

export async function compareSize( { cache = ".sizecache.json", files } = {} ) {
	if ( !files || !files.length ) {
		throw new Error( "No files specified" );
	}

	const branch = await getBranchName();
	const sizeCache = await getCache( cache );

	let rawPadLength = 0;
	let gzPadLength = 0;
	const results = await Promise.all(
		files.map( async function( filename ) {

			let contents = await fs.promises.readFile( filename, "utf8" );

			// Remove the banner for size comparisons.
			// The version string can vary widely by short SHA.
			contents = contents.replace( /\/\*\! jQuery[^\n]+/, "" );

			const size = Buffer.byteLength( contents, "utf8" );
			const gzippedSize = ( await gzip( contents ) ).length;

			// Add one to give space for the `+` or `-` in the comparison
			rawPadLength = Math.max( rawPadLength, size.toString().length + 1 );
			gzPadLength = Math.max( gzPadLength, gzippedSize.toString().length + 1 );

			return { filename, raw: size, gz: gzippedSize };
		} )
	);

	const header = "raw".padStart( rawPadLength ) +
		"gz".padStart( gzPadLength + 1 ) +
		" Filename";

	const sizes = results.map( function( result ) {
		const rawSize = result.raw.toString().padStart( rawPadLength );
		const gzSize = result.gz.toString().padStart( gzPadLength );
		return `${rawSize} ${gzSize} ${result.filename}`;
	} );

	const comparisons = Object.keys( sizeCache ).map( function( branch ) {
		const branchSizes = Object.keys( sizeCache[ branch ] ).map( function( filename ) {
			const branchResult = sizeCache[ branch ][ filename ];
			const compareResult = results.find( function( result ) {
				return result.filename === filename;
			} ) || {};

			const compareRaw = compareSizes( branchResult.raw, compareResult.raw, rawPadLength );
			const compareGz = compareSizes( branchResult.gz, compareResult.gz, gzPadLength );
			return `${compareRaw} ${compareGz} ${filename}`;
		} );

		return [
			"", // New line before each branch
			chalk.bold( branch ),
			header,
			...branchSizes
		].join( "\n" );
	} );

	const output = [
		"", // Opening new line
		chalk.bold( "Sizes" ),
		header,
		...sizes,
		...comparisons,
		"" // Closing new line
	].join( "\n" );

	console.log( output );

	// Only save cache for the current branch
	// if the working directory is clean.
	if ( await isCleanWorkingDir() ) {
		sizeCache[ branch ] = {};
		results.forEach( function( result ) {
			sizeCache[ branch ][ result.filename ] = {
				raw: result.raw,
				gz: result.gz
			};
		} );

		await saveCache( cache, sizeCache );

		console.log( `Saved cache for ${branch}.` );
	}

	return results;
}