"use strict";

const peg = require( "pegjs" );

const Runner = {

    run( benchmarks, runCount, options, callbacks ) {

        // Queue

        const Q = {

            functions: [],

            add( f ) {

                this.functions.push( f );

            },

            run() {

                if ( this.functions.length > 0 ) {

                    this.functions.shift()();

                    // We can't use |arguments.callee| here because |this| would get
                    // messed-up in that case.
                    setTimeout( () => {

                        Q.run();

                    }, 0 );

                }

            },

        };

        // The benchmark itself is factored out into several functions (some of them
        // generated), which are enqueued and run one by one using |setTimeout|. We
        // do this for two reasons:
        //
        //   1. To avoid bowser mechanism for interrupting long-running scripts to
        //      kick-in (or at least to not kick-in that often).
        //
        //   2. To ensure progressive rendering of results in the browser (some
        //      browsers do not render at all when running JavaScript code).
        //
        // The enqueued functions share state, which is all stored in the properties
        // of the |state| object.

        const state = {};

        function initialize() {

            callbacks.start();

            state.totalInputSize = 0;
            state.totalParseTime = 0;

        }

        function benchmarkInitializer( benchmark ) {

            return () => {

                callbacks.benchmarkStart( benchmark );

                state.parser = peg.generate(
                    callbacks.readFile( "examples/" + benchmark.id + ".pegjs" ),
                    options
                );
                state.benchmarkInputSize = 0;
                state.benchmarkParseTime = 0;

            };

        }

        function testRunner( benchmark, test ) {

            return () => {

                callbacks.testStart( benchmark, test );

                const input = callbacks.readFile( "tools/benchmark/" + benchmark.id + "/" + test.file );

                let parseTime = 0;
                for ( let i = 0; i < runCount; i++ ) {

                    const t = ( new Date() ).getTime();
                    state.parser.parse( input );
                    parseTime += ( new Date() ).getTime() - t;

                }
                const averageParseTime = parseTime / runCount;

                callbacks.testFinish( benchmark, test, input.length, averageParseTime );

                state.benchmarkInputSize += input.length;
                state.benchmarkParseTime += averageParseTime;

            };

        }

        function benchmarkFinalizer( benchmark ) {

            return () => {

                callbacks.benchmarkFinish(
                    benchmark,
                    state.benchmarkInputSize,
                    state.benchmarkParseTime
                );

                state.totalInputSize += state.benchmarkInputSize;
                state.totalParseTime += state.benchmarkParseTime;

            };

        }

        function finalize() {

            callbacks.finish( state.totalInputSize, state.totalParseTime );

        }

        // Main

        Q.add( initialize );
        benchmarks.forEach( benchmark => {

            Q.add( benchmarkInitializer( benchmark ) );
            benchmark.tests.forEach( test => {

                Q.add( testRunner( benchmark, test ) );

            } );
            Q.add( benchmarkFinalizer( benchmark ) );

        } );
        Q.add( finalize );

        Q.run();

    },

};

module.exports = Runner;