/**
Copyright: Copyright (c) 2017, Joakim Brännström. All rights reserved.
License: MPL-2
Author: Joakim Brännström (joakim.brannstrom@gmx.com)

This Source Code Form is subject to the terms of the Mozilla Public License,
v.2.0. If a copy of the MPL was not distributed with this file, You can obtain
one at http://mozilla.org/MPL/2.0/.
*/
module dextool.plugin.mutate.backend.test_mutant;

import core.thread : Thread;
import core.time : Duration, dur;
import logger = std.experimental.logger;
import std.algorithm : sort, map, splitter, filter;
import std.array : empty, array, appender;
import std.datetime : SysTime, Clock;
import std.exception : collectException;
import std.path : buildPath;
import std.typecons : Nullable, Tuple, Yes;

import blob_model : Blob;
import process : DrainElement;
import sumtype;

import dextool.fsm : Fsm, next, act, get, TypeDataMap;
import dextool.plugin.mutate.backend.database : Database, MutationEntry,
    NextMutationEntry, spinSql, MutantTimeoutCtx, MutationId;
import dextool.plugin.mutate.backend.interface_ : FilesysIO;
import dextool.plugin.mutate.backend.test_mutant.common;
import dextool.plugin.mutate.backend.test_mutant.interface_ : TestCaseReport;
import dextool.plugin.mutate.backend.test_mutant.test_cmd_runner;
import dextool.plugin.mutate.backend.type : Mutation, TestCase;
import dextool.plugin.mutate.config;
import dextool.plugin.mutate.type : TestCaseAnalyzeBuiltin, ShellCommand;
import dextool.set;
import dextool.type : AbsolutePath, ExitStatusType, Path;

@safe:

auto makeTestMutant() {
    return BuildTestMutant();
}

private:

struct BuildTestMutant {
@safe:
nothrow:

    import dextool.plugin.mutate.type : MutationKind;

    private struct InternalData {
        Mutation.Kind[] mut_kinds;
        FilesysIO filesys_io;
        ConfigMutationTest config;
    }

    private InternalData data;

    auto config(ConfigMutationTest c) {
        data.config = c;
        return this;
    }

    auto mutations(MutationKind[] v) {
        import dextool.plugin.mutate.backend.utility : toInternal;

        data.mut_kinds = toInternal(v);
        return this;
    }

    ExitStatusType run(ref Database db, FilesysIO fio) nothrow {
        // trusted because the lifetime of the database is guaranteed to outlive any instances in this scope
        auto db_ref = () @trusted { return &db; }();

        auto driver_data = DriverData(db_ref, fio, data.mut_kinds, new AutoCleanup, data.config);

        try {
            auto test_driver = TestDriver(driver_data);

            while (test_driver.isRunning) {
                test_driver.execute;
            }

            return test_driver.status;
        } catch (Exception e) {
            logger.error(e.msg).collectException;
        }

        return ExitStatusType.Errors;
    }
}

struct DriverData {
    Database* db;
    FilesysIO filesysIO;
    Mutation.Kind[] mutKind;
    AutoCleanup autoCleanup;
    ConfigMutationTest conf;
}

struct MeasureTestDurationResult {
    bool ok;
    Duration runtime;
}

/** Measure the time it takes to run the test command.
 *
 * The runtime is the lowest of three executions. Anything else is assumed to
 * be variations in the system.
 *
 * If the tests fail (exit code isn't 0) any time then they are too unreliable
 * to use for mutation testing.
 *
 * Params:
 *  cmd = test command to measure
 */
MeasureTestDurationResult measureTestCommand(ref TestRunner runner) @safe nothrow {
    import std.algorithm : min;
    import std.datetime.stopwatch : StopWatch, AutoStart;
    import process;

    if (runner.empty) {
        collectException(logger.error("No test command(s) specified (--test-cmd)"));
        return MeasureTestDurationResult(false);
    }

    static struct Rval {
        TestResult result;
        Duration runtime;
    }

    auto runTest() @safe {
        auto sw = StopWatch(AutoStart.yes);
        auto res = runner.run;
        return Rval(res, sw.peek);
    }

    static void print(DrainElement[] data) @trusted {
        import std.stdio : stdout, write;

        foreach (l; data) {
            write(l.byUTF8);
        }
        stdout.flush;
    }

    auto runtime = Duration.max;
    bool failed;
    for (int i; i < 3 && !failed; ++i) {
        try {
            auto res = runTest;
            final switch (res.result.status) with (TestResult) {
            case Status.passed:
                runtime = min(runtime, res.runtime);
                break;
            case Status.failed:
                goto case;
            case Status.timeout:
                goto case;
            case Status.error:
                failed = true;
                print(res.result.output);
                break;
            }
        } catch (Exception e) {
            logger.error(e.msg).collectException;
            failed = true;
        }
    }

    return MeasureTestDurationResult(!failed, runtime);
}

struct TestDriver {
    import std.datetime : SysTime;
    import std.typecons : Unique;
    import dextool.plugin.mutate.backend.database : Schemata, SchemataId, MutationStatusId;
    import dextool.plugin.mutate.backend.test_mutant.source_mutant : MutationTestDriver,
        MutationTestResult;
    import dextool.plugin.mutate.backend.test_mutant.timeout : calculateTimeout, TimeoutFsm;

    /// Runs the test commands.
    TestRunner runner;

    ///
    TestCaseAnalyzer testCaseAnalyzer;

    static struct Global {
        DriverData data;
        Unique!MutationTestDriver mut_driver;

        TimeoutFsm timeoutFsm;

        /// The time it takes to execute the test suite when no mutant is injected.
        Duration testSuiteRuntime;

        /// the next mutant to test, if there are any.
        MutationEntry nextMutant;

        // when the user manually configure the timeout it means that the
        // timeout algorithm should not be used.
        bool hardcodedTimeout;

        /// Max time to run the mutation testing for.
        SysTime maxRuntime;

        /// Test commands to execute.
        ShellCommand[] testCmds;
    }

    static struct UpdateTimeoutData {
        long lastTimeoutIter;
    }

    static struct None {
    }

    static struct Initialize {
    }

    static struct PullRequest {
    }

    static struct PullRequestData {
        import dextool.plugin.mutate.type : TestConstraint;

        TestConstraint constraint;
        long seed;
    }

    static struct SanityCheck {
        bool sanityCheckFailed;
    }

    static struct AnalyzeTestCmdForTestCase {
        TestCase[] foundTestCases;
    }

    static struct UpdateAndResetAliveMutants {
        TestCase[] foundTestCases;
    }

    static struct ResetOldMutant {
        bool doneTestingOldMutants;
    }

    static struct ResetOldMutantData {
        /// Number of mutants that where reset.
        long resetCount;
        long maxReset;
    }

    static struct CleanupTempDirs {
    }

    static struct CheckMutantsLeft {
        bool allMutantsTested;
    }

    static struct ParseStdin {
    }

    static struct PreCompileSut {
        bool compilationError;
    }

    static struct FindTestCmds {
    }

    static struct ChooseMode {
    }

    static struct MeasureTestSuite {
        bool unreliableTestSuite;
    }

    static struct PreMutationTest {
    }

    static struct MutationTest {
        bool next;
        bool mutationError;
        MutationTestResult result;
    }

    static struct CheckTimeout {
        bool timeoutUnchanged;
    }

    static struct NextSchemata {
        bool hasSchema;
        Schemata schemata;
    }

    static struct PreSchemata {
        Schemata schemata;

        bool error;
    }

    static struct SchemataTest {
        import dextool.plugin.mutate.backend.test_mutant.schemata : MutationTestResult;

        SchemataId id;
        MutationTestResult[] result;
    }

    static struct SchemataTestResult {
        import dextool.plugin.mutate.backend.test_mutant.schemata : MutationTestResult;

        SchemataId id;
        MutationTestResult[] result;
    }

    static struct SchemataRestore {
        bool error;
    }

    static struct SchemataRestoreData {
        static struct Original {
            AbsolutePath path;
            Blob original;
        }

        Original[] original;
    }

    static struct Done {
    }

    static struct Error {
    }

    static struct UpdateTimeout {
    }

    static struct NextPullRequestMutant {
        bool noUnknownMutantsLeft;
    }

    static struct NextPullRequestMutantData {
        import dextool.plugin.mutate.backend.database : MutationStatusId;

        MutationStatusId[] mutants;

        /// If set then stop after this many alive are found.
        Nullable!int maxAlive;
        /// number of alive mutants that has been found.
        int alive;
    }

    static struct NextMutant {
        bool noUnknownMutantsLeft;
    }

    static struct HandleTestResult {
        MutationTestResult result;
    }

    static struct CheckRuntime {
        bool reachedMax;
    }

    static struct SetMaxRuntime {
    }

    alias Fsm = dextool.fsm.Fsm!(None, Initialize, SanityCheck,
            AnalyzeTestCmdForTestCase, UpdateAndResetAliveMutants, ResetOldMutant,
            CleanupTempDirs, CheckMutantsLeft, PreCompileSut, MeasureTestSuite,
            PreMutationTest, NextMutant, MutationTest, HandleTestResult,
            CheckTimeout, Done, Error, UpdateTimeout, CheckRuntime,
            SetMaxRuntime, PullRequest, NextPullRequestMutant, ParseStdin, FindTestCmds, ChooseMode,
            NextSchemata, PreSchemata, SchemataTest, SchemataTestResult, SchemataRestore);
    alias LocalStateDataT = Tuple!(UpdateTimeoutData, NextPullRequestMutantData,
            PullRequestData, ResetOldMutantData, SchemataRestoreData);

    private {
        Fsm fsm;
        Global global;
        TypeDataMap!(LocalStateDataT, UpdateTimeout, NextPullRequestMutant,
                PullRequest, ResetOldMutant, SchemataRestore) local;
        bool isRunning_ = true;
    }

    this(DriverData data) {
        this.global = Global(data);
        this.global.timeoutFsm = TimeoutFsm(data.mutKind);
        this.global.hardcodedTimeout = !global.data.conf.mutationTesterRuntime.isNull;
        local.get!PullRequest.constraint = global.data.conf.constraint;
        local.get!PullRequest.seed = global.data.conf.pullRequestSeed;
        local.get!NextPullRequestMutant.maxAlive = global.data.conf.maxAlive;
        local.get!ResetOldMutant.maxReset = global.data.conf.oldMutantsNr;
        this.global.testCmds = global.data.conf.mutationTester;

        this.runner = TestRunner.make(global.data.conf.testPoolSize);
        // using an unreasonable timeout to make it possible to analyze for
        // test cases and measure the test suite.
        this.runner.timeout = 999.dur!"hours";
        this.runner.put(data.conf.mutationTester);

        // TODO: allow a user, as is for test_cmd, to specify an array of
        // external analyzers.
        this.testCaseAnalyzer = TestCaseAnalyzer(global.data.conf.mutationTestCaseBuiltin,
                global.data.conf.mutationTestCaseAnalyze, global.data.autoCleanup);
    }

    static void execute_(ref TestDriver self) @trusted {
        // see test_mutant/basis.md and figures/test_mutant_fsm.pu for a
        // graphical view of the state machine.

        self.fsm.next!((None a) => fsm(Initialize.init),
                (Initialize a) => fsm(SanityCheck.init), (SanityCheck a) {
            if (a.sanityCheckFailed)
                return fsm(Error.init);
            if (self.global.data.conf.unifiedDiffFromStdin)
                return fsm(ParseStdin.init);
            return fsm(PreCompileSut.init);
        }, (ParseStdin a) => fsm(PreCompileSut.init), (AnalyzeTestCmdForTestCase a) => fsm(
                UpdateAndResetAliveMutants(a.foundTestCases)),
                (UpdateAndResetAliveMutants a) => fsm(CheckMutantsLeft.init), (ResetOldMutant a) {
            if (a.doneTestingOldMutants)
                return fsm(Done.init);
            return fsm(UpdateTimeout.init);
        }, (CleanupTempDirs a) {
            if (self.local.get!PullRequest.constraint.empty)
                return fsm(NextSchemata.init);
            return fsm(NextPullRequestMutant.init);
        }, (CheckMutantsLeft a) {
            if (a.allMutantsTested
                && self.global.data.conf.onOldMutants == ConfigMutationTest.OldMutant.nothing)
                return fsm(Done.init);
            return fsm(MeasureTestSuite.init);
        }, (PreCompileSut a) {
            if (a.compilationError)
                return fsm(Error.init);
            if (self.global.data.conf.testCommandDir.empty)
                return fsm(ChooseMode.init);
            return fsm(FindTestCmds.init);
        }, (FindTestCmds a) { return fsm(ChooseMode.init); }, (ChooseMode a) {
            if (!self.local.get!PullRequest.constraint.empty)
                return fsm(PullRequest.init);
            if (!self.global.data.conf.mutationTestCaseAnalyze.empty
                || !self.global.data.conf.mutationTestCaseBuiltin.empty)
                return fsm(AnalyzeTestCmdForTestCase.init);
            return fsm(CheckMutantsLeft.init);
        }, (PullRequest a) => fsm(CheckMutantsLeft.init), (MeasureTestSuite a) {
            if (a.unreliableTestSuite)
                return fsm(Error.init);
            return fsm(SetMaxRuntime.init);
        }, (SetMaxRuntime a) => fsm(UpdateTimeout.init), (NextPullRequestMutant a) {
            if (a.noUnknownMutantsLeft)
                return fsm(Done.init);
            return fsm(PreMutationTest.init);
        }, (NextSchemata a) {
            if (a.hasSchema)
                return fsm(PreSchemata(a.schemata));
            return fsm(NextMutant.init);
        }, (PreSchemata a) {
            if (a.error)
                return fsm(Error.init);
            return fsm(SchemataTest(a.schemata.id));
        }, (SchemataTest a) { return fsm(SchemataTestResult(a.id, a.result)); },
                (SchemataTestResult a) => fsm(SchemataRestore.init), (SchemataRestore a) {
            if (a.error)
                return fsm(Error.init);
            return fsm(CheckRuntime.init);
        }, (NextMutant a) {
            if (a.noUnknownMutantsLeft)
                return fsm(CheckTimeout.init);
            return fsm(PreMutationTest.init);
        }, (PreMutationTest a) => fsm(MutationTest.init),
                (UpdateTimeout a) => fsm(CleanupTempDirs.init), (MutationTest a) {
            if (a.next)
                return fsm(HandleTestResult(a.result));
            else if (a.mutationError)
                return fsm(Error.init);
            return fsm(a);
        }, (HandleTestResult a) => fsm(CheckRuntime.init), (CheckRuntime a) {
            if (a.reachedMax)
                return fsm(Done.init);
            return fsm(UpdateTimeout.init);
        }, (CheckTimeout a) {
            if (a.timeoutUnchanged)
                return fsm(ResetOldMutant.init);
            return fsm(UpdateTimeout.init);
        }, (Done a) => fsm(a), (Error a) => fsm(a),);

        self.fsm.act!(self);
    }

nothrow:
    void execute() {
        try {
            execute_(this);
        } catch (Exception e) {
            logger.warning(e.msg).collectException;
        }
    }

    bool isRunning() {
        return isRunning_;
    }

    ExitStatusType status() {
        if (fsm.isState!Done)
            return ExitStatusType.Ok;
        return ExitStatusType.Errors;
    }

    void opCall(None data) {
    }

    void opCall(Initialize data) {
    }

    void opCall(Done data) {
        global.data.autoCleanup.cleanup;
        logger.info("Done!").collectException;
        isRunning_ = false;
    }

    void opCall(Error data) {
        global.data.autoCleanup.cleanup;
        isRunning_ = false;
    }

    void opCall(ref SanityCheck data) {
        // #SPC-sanity_check_db_vs_filesys
        import colorlog : color, Color;
        import dextool.plugin.mutate.backend.utility : checksum, Checksum;

        logger.info("Checking that the file(s) on the filesystem match the database")
            .collectException;

        auto failed = appender!(string[])();
        foreach (file; spinSql!(() { return global.data.db.getFiles; })) {
            auto db_checksum = spinSql!(() {
                return global.data.db.getFileChecksum(file);
            });

            try {
                auto abs_f = AbsolutePath(file, global.data.filesysIO.getOutputDir);
                auto f_checksum = checksum(global.data.filesysIO.makeInput(abs_f).content[]);
                if (db_checksum != f_checksum) {
                    failed.put(abs_f);
                }
            } catch (Exception e) {
                // assume it is a problem reading the file or something like that.
                failed.put(file);
                logger.warningf("%s: %s", file, e.msg).collectException;
            }
        }

        data.sanityCheckFailed = failed.data.length != 0;

        if (data.sanityCheckFailed) {
            logger.error("Detected that file(s) has changed since last analyze where done")
                .collectException;
            logger.error("Either restore the file(s) or rerun the analyze").collectException;
            foreach (f; failed.data) {
                logger.info(f).collectException;
            }
        } else {
            logger.info("Ok".color(Color.green)).collectException;
        }
    }

    void opCall(ParseStdin data) {
        import dextool.plugin.mutate.backend.diff_parser : diffFromStdin;
        import dextool.plugin.mutate.type : Line;

        try {
            auto constraint = local.get!PullRequest.constraint;
            foreach (pkv; diffFromStdin.toRange(global.data.filesysIO.getOutputDir)) {
                constraint.value[pkv.key] ~= pkv.value.toRange.map!(a => Line(a)).array;
            }
            local.get!PullRequest.constraint = constraint;
        } catch (Exception e) {
            logger.warning(e.msg).collectException;
        }
    }

    void opCall(ref AnalyzeTestCmdForTestCase data) {
        import std.datetime.stopwatch : StopWatch;
        import dextool.plugin.mutate.backend.type : TestCase;

        TestCase[] found;
        try {
            auto res = runTester(runner);
            auto analyze = testCaseAnalyzer.analyze(res.output, Yes.allFound);

            analyze.match!((TestCaseAnalyzer.Success a) { found = a.found; },
                    (TestCaseAnalyzer.Unstable a) {
                logger.warningf("Unstable test cases found: [%-(%s, %)]", a.unstable);
                found = a.found;
            }, (TestCaseAnalyzer.Failed a) {
                logger.warning("The parser that analyze the output for test case(s) failed");
            });
        } catch (Exception e) {
            logger.warning(e.msg).collectException;
        }

        warnIfConflictingTestCaseIdentifiers(found);
        data.foundTestCases = found;
    }

    void opCall(UpdateAndResetAliveMutants data) {
        import std.traits : EnumMembers;

        // the test cases before anything has potentially changed.
        auto old_tcs = spinSql!(() {
            Set!string old_tcs;
            foreach (tc; global.data.db.getDetectedTestCases) {
                old_tcs.add(tc.name);
            }
            return old_tcs;
        });

        void transaction() @safe {
            final switch (global.data.conf.onRemovedTestCases) with (
                ConfigMutationTest.RemovedTestCases) {
            case doNothing:
                global.data.db.addDetectedTestCases(data.foundTestCases);
                break;
            case remove:
                foreach (id; global.data.db.setDetectedTestCases(data.foundTestCases)) {
                    global.data.db.updateMutationStatus(id, Mutation.Status.unknown);
                }
                break;
            }
        }

        auto found_tcs = spinSql!(() @trusted {
            auto tr = global.data.db.transaction;
            transaction();

            Set!string found_tcs;
            foreach (tc; global.data.db.getDetectedTestCases) {
                found_tcs.add(tc.name);
            }

            tr.commit;
            return found_tcs;
        });

        printDroppedTestCases(old_tcs, found_tcs);

        if (hasNewTestCases(old_tcs, found_tcs)
                && global.data.conf.onNewTestCases == ConfigMutationTest.NewTestCases.resetAlive) {
            logger.info("Resetting alive mutants").collectException;
            // there is no use in trying to limit the mutants to reset to those
            // that are part of "this" execution because new test cases can
            // only mean one thing: re-test all alive mutants.
            spinSql!(() {
                global.data.db.resetMutant([EnumMembers!(Mutation.Kind)],
                    Mutation.Status.alive, Mutation.Status.unknown);
            });
        }
    }

    void opCall(ref ResetOldMutant data) {
        import dextool.plugin.mutate.backend.database.type;

        if (global.data.conf.onOldMutants == ConfigMutationTest.OldMutant.nothing) {
            data.doneTestingOldMutants = true;
            return;
        }
        if (Clock.currTime > global.maxRuntime) {
            data.doneTestingOldMutants = true;
            return;
        }
        if (local.get!ResetOldMutant.resetCount >= local.get!ResetOldMutant.maxReset) {
            data.doneTestingOldMutants = true;
            return;
        }

        local.get!ResetOldMutant.resetCount++;

        logger.infof("Resetting an old mutant (%s/%s)", local.get!ResetOldMutant.resetCount,
                local.get!ResetOldMutant.maxReset).collectException;
        auto oldest = spinSql!(() {
            return global.data.db.getOldestMutants(global.data.mutKind, 1);
        });

        foreach (const old; oldest) {
            logger.info("Last updated ", old.updated).collectException;
            spinSql!(() {
                global.data.db.updateMutationStatus(old.id, Mutation.Status.unknown);
            });
        }
    }

    void opCall(CleanupTempDirs data) {
        global.data.autoCleanup.cleanup;
    }

    void opCall(ref CheckMutantsLeft data) {
        spinSql!(() { global.timeoutFsm.execute(*global.data.db); });

        data.allMutantsTested = global.timeoutFsm.output.done;

        if (global.timeoutFsm.output.done) {
            logger.info("All mutants are tested").collectException;
        }
    }

    void opCall(ref PreCompileSut data) {
        import std.stdio : write;
        import colorlog : color, Color;
        import process;

        logger.info("Checking the build command").collectException;
        try {
            auto output = appender!(DrainElement[])();
            auto p = pipeProcess(global.data.conf.mutationCompile.value).sandbox.drain(output,
                    999.dur!"hours").scopeKill;
            if (p.wait == 0) {
                logger.info("Ok".color(Color.green));
                return;
            }

            logger.error("Build commman failed");
            foreach (l; output.data) {
                write(l.byUTF8);
            }
        } catch (Exception e) {
            // unable to for example execute the compiler
            logger.error(e.msg).collectException;
        }

        data.compilationError = true;
    }

    void opCall(FindTestCmds data) {
        auto cmds = appender!(ShellCommand[])();
        foreach (root; global.data.conf.testCommandDir) {
            try {
                cmds.put(findExecutables(root.AbsolutePath)
                        .map!(a => ShellCommand([a] ~ global.data.conf.testCommandDirFlag)));
            } catch (Exception e) {
                logger.warning(e.msg).collectException;
            }
        }

        if (!cmds.data.empty) {
            this.runner.put(cmds.data);
            this.global.testCmds ~= cmds.data;
            logger.infof("Found test commands in %s:",
                    global.data.conf.testCommandDir).collectException;
            foreach (c; cmds.data) {
                logger.info(c).collectException;
            }
        }
    }

    void opCall(ChooseMode data) {
    }

    void opCall(PullRequest data) {
        import std.array : appender;
        import std.random : randomCover, Mt19937_64;
        import dextool.plugin.mutate.backend.database : MutationStatusId;
        import dextool.plugin.mutate.backend.type : SourceLoc;
        import dextool.set;

        Set!MutationStatusId mut_ids;

        foreach (kv; local.get!PullRequest.constraint.value.byKeyValue) {
            const file_id = spinSql!(() => global.data.db.getFileId(kv.key));
            if (file_id.isNull) {
                logger.infof("The file %s do not exist in the database. Skipping...",
                        kv.key).collectException;
                continue;
            }

            foreach (l; kv.value) {
                auto mutants = spinSql!(() {
                    return global.data.db.getMutationsOnLine(global.data.mutKind,
                        file_id.get, SourceLoc(l.value, 0));
                });

                const pre_cnt = mut_ids.length;
                foreach (v; mutants)
                    mut_ids.add(v);

                logger.infof(mut_ids.length - pre_cnt > 0, "Found %s mutant(s) to test (%s:%s)",
                        mut_ids.length - pre_cnt, kv.key, l.value).collectException;
            }
        }

        logger.infof(!mut_ids.empty, "Found %s mutants in the diff",
                mut_ids.length).collectException;

        const seed = local.get!PullRequest.seed;
        logger.infof("Using random seed %s when choosing the mutants to test",
                seed).collectException;
        auto rng = Mt19937_64(seed);
        local.get!NextPullRequestMutant.mutants = mut_ids.toArray.sort.randomCover(rng).array;
        logger.trace("Test sequence ", local.get!NextPullRequestMutant.mutants).collectException;

        if (mut_ids.empty) {
            logger.warning("None of the locations specified with -L exists").collectException;
            logger.info("Available files are:").collectException;
            foreach (f; spinSql!(() => global.data.db.getFiles))
                logger.info(f).collectException;
        }
    }

    void opCall(ref MeasureTestSuite data) {
        if (!global.data.conf.mutationTesterRuntime.isNull) {
            global.testSuiteRuntime = global.data.conf.mutationTesterRuntime.get;
            return;
        }

        logger.info("Measuring the runtime of the test command: ",
                global.testCmds).collectException;

        const tester = () {
            try {
                // need to measure the test suite single threaded to get the "worst"
                // test case execution time because if multiple instances are running
                // on the same computer the available CPU resources are variable. This
                // reduces the number of mutants marked as timeout. Further
                // improvements in the future could be to check the loadavg and let it
                // affect the number of threads.
                runner.poolSize = 1;
                scope (exit)
                    runner.poolSize = global.data.conf.testPoolSize;
                return measureTestCommand(runner);
            } catch (Exception e) {
                logger.error(e.msg).collectException;
                return MeasureTestDurationResult(false);
            }
        }();

        if (tester.ok) {
            // The sampling of the test suite become too unreliable when the timeout is <1s.
            // This is a quick and dirty fix.
            // A proper fix requires an update of the sampler in runTester.
            auto t = tester.runtime < 1.dur!"seconds" ? 1.dur!"seconds" : tester.runtime;
            logger.info("Test command runtime: ", t).collectException;
            global.testSuiteRuntime = t;
        } else {
            data.unreliableTestSuite = true;
            logger.error("The test command is unreliable. It must return exit status '0' when no mutants are injected")
                .collectException;
        }
    }

    void opCall(PreMutationTest) {
        auto factory(DriverData d, MutationEntry mutp, TestRunner* runner) @safe nothrow {
            import std.typecons : Unique;
            import dextool.plugin.mutate.backend.test_mutant.interface_ : GatherTestCase;

            try {
                auto global = MutationTestDriver.Global(d.filesysIO, d.db, mutp, runner);
                return Unique!MutationTestDriver(new MutationTestDriver(global,
                        MutationTestDriver.TestMutantData(!(d.conf.mutationTestCaseAnalyze.empty
                        && d.conf.mutationTestCaseBuiltin.empty), d.conf.mutationCompile,),
                        MutationTestDriver.TestCaseAnalyzeData(&testCaseAnalyzer)));
            } catch (Exception e) {
                logger.error(e.msg).collectException;
            }
            assert(0, "should not happen");
        }

        runner.timeout = calculateTimeout(global.timeoutFsm.output.iter, global.testSuiteRuntime);
        global.mut_driver = factory(global.data, global.nextMutant, () @trusted {
            return &runner;
        }());
    }

    void opCall(ref MutationTest data) {
        if (global.mut_driver.isRunning) {
            global.mut_driver.execute();
        } else if (global.mut_driver.stopBecauseError) {
            data.mutationError = true;
        } else {
            data.result = global.mut_driver.result;
            data.next = true;
        }
    }

    void opCall(ref CheckTimeout data) {
        data.timeoutUnchanged = global.hardcodedTimeout || global.timeoutFsm.output.done;
    }

    void opCall(UpdateTimeout) {
        spinSql!(() { global.timeoutFsm.execute(*global.data.db); });

        const lastIter = local.get!UpdateTimeout.lastTimeoutIter;

        if (lastIter != global.timeoutFsm.output.iter) {
            logger.infof("Changed the timeout from %s to %s (iteration %s)",
                    calculateTimeout(lastIter, global.testSuiteRuntime),
                    calculateTimeout(global.timeoutFsm.output.iter, global.testSuiteRuntime),
                    global.timeoutFsm.output.iter).collectException;
            local.get!UpdateTimeout.lastTimeoutIter = global.timeoutFsm.output.iter;
        }
    }

    void opCall(ref NextPullRequestMutant data) {
        global.nextMutant = MutationEntry.init;
        data.noUnknownMutantsLeft = true;

        while (!local.get!NextPullRequestMutant.mutants.empty) {
            const id = local.get!NextPullRequestMutant.mutants[$ - 1];
            const status = spinSql!(() => global.data.db.getMutationStatus(id));

            if (status.isNull)
                continue;

            if (status.get == Mutation.Status.alive) {
                local.get!NextPullRequestMutant.alive++;
            }

            if (status.get != Mutation.Status.unknown) {
                local.get!NextPullRequestMutant.mutants
                    = local.get!NextPullRequestMutant.mutants[0 .. $ - 1];
                continue;
            }

            const info = spinSql!(() => global.data.db.getMutantsInfo(global.data.mutKind, [
                        id
                    ]));
            if (info.empty)
                continue;

            global.nextMutant = spinSql!(() => global.data.db.getMutation(info[0].id));
            data.noUnknownMutantsLeft = false;
            break;
        }

        if (!local.get!NextPullRequestMutant.maxAlive.isNull) {
            const alive = local.get!NextPullRequestMutant.alive;
            const maxAlive = local.get!NextPullRequestMutant.maxAlive.get;
            logger.infof(alive > 0, "Found %s/%s alive mutants", alive, maxAlive).collectException;
            if (alive >= maxAlive) {
                data.noUnknownMutantsLeft = true;
            }
        }
    }

    void opCall(ref NextMutant data) {
        global.nextMutant = MutationEntry.init;

        auto next = spinSql!(() {
            return global.data.db.nextMutation(global.data.mutKind);
        });

        data.noUnknownMutantsLeft = next.st == NextMutationEntry.Status.done;

        if (!next.entry.isNull) {
            global.nextMutant = next.entry.get;
        }
    }

    void opCall(HandleTestResult data) {
        void statusUpdate(MutationTestResult.StatusUpdate result) {
            import dextool.plugin.mutate.backend.test_mutant.timeout : updateMutantStatus;

            const cnt_action = () {
                if (result.status == Mutation.Status.alive)
                    return Database.CntAction.incr;
                return Database.CntAction.reset;
            }();

            auto statusId = spinSql!(() {
                return global.data.db.getMutationStatusId(result.id);
            });
            if (statusId.isNull)
                return;

            spinSql!(() @trusted {
                auto t = global.data.db.transaction;
                updateMutantStatus(*global.data.db, statusId.get,
                    result.status, global.timeoutFsm.output.iter);
                global.data.db.updateMutation(statusId.get, cnt_action);
                global.data.db.updateMutation(statusId.get, result.testTime);
                global.data.db.updateMutationTestCases(statusId.get, result.testCases);
                t.commit;
            });

            logger.infof("%s %s (%s)", result.id, result.status, result.testTime).collectException;
            logger.infof(!result.testCases.empty, `%s killed by [%-(%s, %)]`,
                    result.id, result.testCases.sort.map!"a.name").collectException;
        }

        data.result.value.match!((MutationTestResult.NoResult a) {},
                (MutationTestResult.StatusUpdate a) => statusUpdate(a));
    }

    void opCall(SetMaxRuntime) {
        global.maxRuntime = Clock.currTime + global.data.conf.maxRuntime;
    }

    void opCall(ref CheckRuntime data) {
        data.reachedMax = Clock.currTime > global.maxRuntime;
        if (data.reachedMax) {
            logger.infof("Max runtime of %s reached at %s",
                    global.data.conf.maxRuntime, global.maxRuntime).collectException;
        }
    }

    void opCall(ref NextSchemata data) {
        auto schema = spinSql!(() { return global.data.db.nextSchemata; });

        data.hasSchema = !schema.isNull;
        if (!schema.isNull) {
            data.schemata = schema.get;
            logger.info("Running schemata ", data.schemata.id).collectException;
        }
    }

    void opCall(ref PreSchemata data) {
        import std.format : format;
        import dextool.plugin.mutate.backend.database.type : SchemataFragment;

        Blob makeSchemata(Blob original, SchemataFragment[] fragments) {
            import blob_model;

            Edit[] edits;
            foreach (a; fragments) {
                edits ~= new Edit(Interval(a.offset.begin, a.offset.end), a.text);
            }
            auto m = merge(original, edits);
            return change(new Blob(original.uri, original.content), m.edits);
        }

        SchemataFragment[] fragments(Path p) {
            return data.schemata.fragments.filter!(a => a.file == p).array;
        }

        SchemataRestoreData.Original[] orgs;
        try {
            auto files = data.schemata.fragments.map!(a => a.file).toSet;
            foreach (f; files.toRange) {
                const absf = AbsolutePath(f, global.data.filesysIO.getOutputDir);

                orgs ~= SchemataRestoreData.Original(absf, global.data.filesysIO.makeInput(absf));

                // writing the schemata.
                auto s = makeSchemata(orgs[$ - 1].original, fragments(f));
                global.data.filesysIO.makeOutput(absf).write(s);

                if (global.data.conf.logSchemata) {
                    global.data.filesysIO.makeOutput(AbsolutePath(format!"%s.schema%s"(absf,
                            data.schemata.id).Path)).write(s);
                }
            }
        } catch (Exception e) {
            logger.warning(e.msg).collectException;
            data.error = true;
        }
        local.get!SchemataRestore.original = orgs;
    }

    void opCall(ref SchemataTest data) {
        import dextool.plugin.mutate.backend.test_mutant.schemata;

        bool successCompile;
        compile(global.data.conf.mutationCompile).match!((Mutation.Status a) {}, (bool success) {
            successCompile = success;
        },);

        if (!successCompile) {
            logger.infof("Schemata %s failed to compile", data.id).collectException;
            return;
        }

        auto mutants = spinSql!(() {
            return global.data.db.getSchemataMutants(data.id);
        });

        try {
            auto driver = SchemataTestDriver(global.data.filesysIO, &runner,
                    global.data.db, &testCaseAnalyzer, mutants);
            while (driver.isRunning) {
                driver.execute;
            }
        } catch (Exception e) {
            logger.info(e.msg).collectException;
            logger.warning("Failed executing schemata ", data.id).collectException;
        }
    }

    void opCall(SchemataTestResult data) {
        foreach (m; data.result) {
            spinSql!(() {
                global.data.db.updateMutation(m.id, m.status, m.testTime);
            });
            spinSql!(() {
                global.data.db.updateMutationTestCases(m.id, m.testCases);
            });
        }

        spinSql!(() { global.data.db.finishSchemata(data.id); });
    }

    void opCall(ref SchemataRestore data) {
        foreach (o; local.get!SchemataRestore.original) {
            try {
                global.data.filesysIO.makeOutput(o.path).write(o.original.content);
            } catch (Exception e) {
                logger.error(e.msg).collectException;
                data.error = true;
            }
        }
    }
}

private:

/** Compare the old test cases with those that have been found this run.
 *
 * TODO: the side effect that this function print to the console is NOT good.
 */
bool hasNewTestCases(ref Set!string old_tcs, ref Set!string found_tcs) @safe nothrow {
    bool rval;

    auto new_tcs = found_tcs.setDifference(old_tcs);
    foreach (tc; new_tcs.toRange) {
        logger.info(!rval, "Found new test case(s):").collectException;
        logger.infof("%s", tc).collectException;
        rval = true;
    }

    return rval;
}

/** Compare old and new test cases to print those that have been removed.
 */
void printDroppedTestCases(ref Set!string old_tcs, ref Set!string changed_tcs) @safe nothrow {
    auto diff = old_tcs.setDifference(changed_tcs);
    auto removed = diff.toArray;

    logger.info(removed.length != 0, "Detected test cases that has been removed:").collectException;
    foreach (tc; removed) {
        logger.infof("%s", tc).collectException;
    }
}

/// Returns: true if all tests cases have unique identifiers
void warnIfConflictingTestCaseIdentifiers(TestCase[] found_tcs) @safe nothrow {
    Set!TestCase checked;
    bool conflict;

    foreach (tc; found_tcs) {
        if (checked.contains(tc)) {
            logger.info(!conflict,
                    "Found test cases that do not have global, unique identifiers")
                .collectException;
            logger.info(!conflict,
                    "This make the report of test cases that has killed zero mutants unreliable")
                .collectException;
            logger.info("%s", tc).collectException;
            conflict = true;
        }
    }
}