package com.benchmark.runner;

import com.benchmark.benchmarks.DataAccessBenchmark;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.results.Result;
import org.openjdk.jmh.results.RunResult;
import org.openjdk.jmh.runner.options.CommandLineOptions;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.options.ChainedOptionsBuilder;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;

import java.lang.management.ManagementFactory;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;

public class BenchmarkMain {

    private static final String README_FILE = "README.md";
    private static final String RESULTS_SECTION_START = "<!-- BENCHMARK_RESULTS_START -->";
    private static final String RESULTS_SECTION_END = "<!-- BENCHMARK_RESULTS_END -->";

    public static void main(String[] args) throws Exception {
        if (isJmhListingOrHelpCommand(args)) {
            org.openjdk.jmh.Main.main(args);
            return;
        }

        CommandLineOptions commandLineOptions = new CommandLineOptions(args);

        ChainedOptionsBuilder builder = new OptionsBuilder()
            .parent(commandLineOptions)
            .jvmArgsPrepend(
                "--enable-native-access=ALL-UNNAMED",
                "--sun-misc-unsafe-memory-access=allow",
                "--add-opens=java.base/java.lang=ALL-UNNAMED",
                "--add-opens=java.base/java.nio=ALL-UNNAMED",
                "--add-opens=java.base/sun.nio.ch=ALL-UNNAMED",
                "--add-exports=java.base/sun.nio.ch=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
                "--add-opens=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
                "--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED",
                "--add-opens=chronicle.map/net.openhft.chronicle.map=chronicle.core",
                "--add-opens=chronicle.map/net.openhft.chronicle.map=ALL-UNNAMED",
                "--add-opens=chronicle.map/net.openhft.chronicle.hash=chronicle.core",
                "--add-opens=chronicle.map/net.openhft.chronicle.hash=ALL-UNNAMED"
            );

        if (args.length == 0) {
            builder.include(DataAccessBenchmark.class.getSimpleName());
        }

        Options opt = builder.build();
        Collection<RunResult> runResults = new Runner(opt).run();
        printSortedSummary(runResults);
        updateReadmeWithLatestResults(runResults);
    }

    private static void printSortedSummary(Collection<RunResult> runResults) {
        if (runResults == null || runResults.isEmpty()) {
            return;
        }

        Map<Mode, List<RunResult>> byMode = new LinkedHashMap<>();
        for (RunResult runResult : runResults) {
            byMode.computeIfAbsent(runResult.getParams().getMode(), m -> new ArrayList<>()).add(runResult);
        }

        System.out.println("\n=== Sorted summary by performance ===");
        for (Map.Entry<Mode, List<RunResult>> entry : byMode.entrySet()) {
            Mode mode = entry.getKey();
            List<RunResult> sorted = new ArrayList<>(entry.getValue());
            boolean lowerIsBetter = mode == Mode.AverageTime || mode == Mode.SampleTime || mode == Mode.SingleShotTime;

            sorted.sort((a, b) -> {
                double scoreA = a.getPrimaryResult().getScore();
                double scoreB = b.getPrimaryResult().getScore();
                return lowerIsBetter ? Double.compare(scoreA, scoreB) : Double.compare(scoreB, scoreA);
            });

            System.out.printf("%n[%s]%n", mode);
            System.out.printf("%-24s %14s %14s %s%n", "fixtureType", "score", "error", "unit");
            for (RunResult runResult : sorted) {
                Result<?> result = runResult.getPrimaryResult();
                String fixtureType = runResult.getParams().getParam("fixtureType");
                System.out.printf(
                    "%-24s %14.3f %14.3f %s%n",
                    fixtureType,
                    result.getScore(),
                    result.getScoreError(),
                    result.getScoreUnit()
                );
            }

            Set<String> presentFixtures = new HashSet<>();
            for (RunResult runResult : sorted) {
                presentFixtures.add(runResult.getParams().getParam("fixtureType"));
            }

            for (String expectedFixture : expectedFixtureTypes()) {
                if (presentFixtures.contains(expectedFixture)) {
                    continue;
                }
                System.out.printf(
                    "%-24s %14s %14s %s%n",
                    expectedFixture,
                    "FAILED",
                    "-",
                    "n/a"
                );
            }
        }
    }

    private static boolean isJmhListingOrHelpCommand(String[] args) {
        for (String arg : args) {
            if ("-l".equals(arg) || "-lp".equals(arg) || "-lprof".equals(arg)
                || "-h".equals(arg) || "--help".equals(arg)) {
                return true;
            }
        }
        return false;
    }

    private static void updateReadmeWithLatestResults(Collection<RunResult> runResults) {
        if (runResults == null || runResults.isEmpty()) {
            return;
        }

        Path readmePath = Paths.get(README_FILE);
        if (!Files.exists(readmePath)) {
            return;
        }

        String sectionContent = buildReadmeResultsSection(runResults);

        try {
            String readme = Files.readString(readmePath, StandardCharsets.UTF_8);
            int start = readme.indexOf(RESULTS_SECTION_START);
            int end = readme.indexOf(RESULTS_SECTION_END);

            String updated;
            if (start >= 0 && end > start) {
                int contentStart = start + RESULTS_SECTION_START.length();
                updated = readme.substring(0, contentStart)
                    + "\n\n"
                    + sectionContent
                    + "\n\n"
                    + readme.substring(end);
            } else {
                updated = readme
                    + "\n\n## Benchmark Results (auto-updated)\n\n"
                    + "This section is managed by the benchmark runner."
                    + " Running `java -jar target/benchmarks.jar` refreshes the snapshot below.\n\n"
                    + RESULTS_SECTION_START
                    + "\n\n"
                    + sectionContent
                    + "\n\n"
                    + RESULTS_SECTION_END
                    + "\n";
            }

            Files.writeString(readmePath, updated, StandardCharsets.UTF_8);
            System.out.println("\nUpdated README benchmark snapshot.");
        } catch (IOException e) {
            System.err.println("Failed to update README benchmark snapshot: " + e.getMessage());
        }
    }

    private static String buildReadmeResultsSection(Collection<RunResult> runResults) {
        StringBuilder sb = new StringBuilder();
        ZonedDateTime now = ZonedDateTime.now();

        sb.append("Last updated: ")
            .append(now.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME))
            .append("\n\n");

        sb.append("### System info\n\n");
        sb.append("- OS: `")
            .append(System.getProperty("os.name"))
            .append(" ")
            .append(System.getProperty("os.version"))
            .append("`")
            .append(" (")
            .append(System.getProperty("os.arch"))
            .append(")\n");
        sb.append("- Java: `")
            .append(System.getProperty("java.version"))
            .append("` (vendor: `")
            .append(System.getProperty("java.vendor"))
            .append("`)\n");
        sb.append("- JVM: `")
            .append(System.getProperty("java.vm.name"))
            .append("` `")
            .append(System.getProperty("java.vm.version"))
            .append("`\n");

        String cpuModel = detectCpuModel();
        if (cpuModel != null && !cpuModel.isBlank()) {
            sb.append("- CPU model: `")
                .append(cpuModel)
                .append("`\n");
        }

        String ramModel = detectRamModel();
        if (ramModel != null && !ramModel.isBlank()) {
            sb.append("- RAM model: `")
                .append(ramModel)
                .append("`\n");
        }

        long totalPhysicalMemoryBytes = detectTotalPhysicalMemoryBytes();
        if (totalPhysicalMemoryBytes > 0) {
            sb.append("- Total physical memory: `")
                .append(totalPhysicalMemoryBytes / (1024 * 1024))
                .append(" MB`\n");
        }

        sb.append("- Available processors: `")
            .append(Runtime.getRuntime().availableProcessors())
            .append("`\n");
        sb.append("- Max heap: `")
            .append(Runtime.getRuntime().maxMemory() / (1024 * 1024))
            .append(" MB`\n\n");

        RunResult first = runResults.iterator().next();
        sb.append("### Run context\n\n");
        sb.append("- Benchmark: `")
            .append(first.getParams().getBenchmark())
            .append("`\n");
        sb.append("- Thread count: `")
            .append(first.getParams().getThreads())
            .append("`\n");
        sb.append("- Fixtures in this snapshot: `")
            .append(runResults.size())
            .append("`\n\n");

        Map<Mode, List<RunResult>> byMode = new LinkedHashMap<>();
        for (RunResult runResult : runResults) {
            byMode.computeIfAbsent(runResult.getParams().getMode(), m -> new ArrayList<>()).add(runResult);
        }

        sb.append("### Results\n\n");
        for (Map.Entry<Mode, List<RunResult>> entry : byMode.entrySet()) {
            Mode mode = entry.getKey();
            List<RunResult> sorted = new ArrayList<>(entry.getValue());
            boolean lowerIsBetter = mode == Mode.AverageTime || mode == Mode.SampleTime || mode == Mode.SingleShotTime;

            sorted.sort((a, b) -> {
                double scoreA = a.getPrimaryResult().getScore();
                double scoreB = b.getPrimaryResult().getScore();
                return lowerIsBetter ? Double.compare(scoreA, scoreB) : Double.compare(scoreB, scoreA);
            });

            sb.append("#### ").append(mode).append("\n\n");
            sb.append("| Rank | Fixture | Score | Error | Unit |\n");
            sb.append("|---:|---|---:|---:|---|\n");

            int rank = 1;
            for (RunResult runResult : sorted) {
                Result<?> result = runResult.getPrimaryResult();
                String fixtureType = runResult.getParams().getParam("fixtureType");

                sb.append("| ")
                    .append(rank++)
                    .append(" | `")
                    .append(fixtureType)
                    .append("` | ")
                    .append(formatDouble(result.getScore()))
                    .append(" | ")
                    .append(formatDouble(result.getScoreError()))
                    .append(" | `")
                    .append(result.getScoreUnit())
                    .append("` |\n");
            }

            Set<String> presentFixtures = new HashSet<>();
            for (RunResult runResult : sorted) {
                presentFixtures.add(runResult.getParams().getParam("fixtureType"));
            }

            for (String expectedFixture : expectedFixtureTypes()) {
                if (presentFixtures.contains(expectedFixture)) {
                    continue;
                }
                sb.append("| - | `")
                    .append(expectedFixture)
                    .append("` | FAILED | - | `n/a` |\n");
            }
            sb.append("\n");
        }

        return sb.toString().trim();
    }

    private static List<String> expectedFixtureTypes() {
        try {
            java.lang.reflect.Field fixtureField = DataAccessBenchmark.class.getDeclaredField("fixtureType");
            Param param = fixtureField.getAnnotation(Param.class);
            if (param == null || param.value() == null || param.value().length == 0) {
                return List.of();
            }
            return Arrays.asList(param.value());
        } catch (NoSuchFieldException e) {
            return List.of();
        }
    }

    private static String formatDouble(double value) {
        if (Double.isNaN(value)) {
            return "NaN";
        }
        if (Double.isInfinite(value)) {
            return value > 0 ? "+Inf" : "-Inf";
        }
        return String.format(Locale.US, "%.3f", value);
    }

    private static String detectCpuModel() {
        String modelFromProperty = System.getProperty("cpu.model");
        if (modelFromProperty != null && !modelFromProperty.isBlank()) {
            return modelFromProperty.trim();
        }

        Path cpuInfo = Paths.get("/proc/cpuinfo");
        if (Files.exists(cpuInfo)) {
            try {
                for (String line : Files.readAllLines(cpuInfo, StandardCharsets.UTF_8)) {
                    if (line.startsWith("model name")) {
                        int idx = line.indexOf(':');
                        if (idx >= 0 && idx + 1 < line.length()) {
                            String value = line.substring(idx + 1).trim();
                            if (!value.isBlank()) {
                                return value;
                            }
                        }
                    }
                }
            } catch (IOException ignored) {
                // Best effort only.
            }
        }

        return null;
    }

    private static String detectRamModel() {
        String modelFromProperty = System.getProperty("ram.model");
        if (modelFromProperty != null && !modelFromProperty.isBlank()) {
            return modelFromProperty.trim();
        }

        String modelFromEnv = System.getenv("RAM_MODEL");
        if (modelFromEnv != null && !modelFromEnv.isBlank()) {
            return modelFromEnv.trim();
        }

        String osName = System.getProperty("os.name", "").toLowerCase(Locale.ROOT);
        if (osName.contains("linux")) {
            String fromDmidecode = runLinuxCommandForSingleLine(
                "bash", "-lc",
                "if command -v dmidecode >/dev/null 2>&1; then "
                    + "dmidecode -t memory 2>/dev/null | "
                    + "awk -F: '/^[[:space:]]*Part Number:/{gsub(/^[ \\t]+|[ \\t]+$/, \"\", $2); "
                    + "if($2!=\"\" && $2!=\"Not Specified\") {print $2; exit}}'; "
                    + "fi"
            );
            if (fromDmidecode != null && !fromDmidecode.isBlank()) {
                return fromDmidecode;
            }

            String fromLshw = runLinuxCommandForSingleLine(
                "bash", "-lc",
                "if command -v lshw >/dev/null 2>&1; then "
                    + "lshw -class memory 2>/dev/null | "
                    + "awk -F: '/^[[:space:]]*product:/{gsub(/^[ \\t]+|[ \\t]+$/, \"\", $2); "
                    + "if($2!=\"\" && $2!=\"[empty]\") {print $2; exit}}'; "
                    + "fi"
            );
            if (fromLshw != null && !fromLshw.isBlank()) {
                return fromLshw;
            }
        }

        return null;
    }

    private static String runLinuxCommandForSingleLine(String... command) {
        Process process = null;
        try {
            process = new ProcessBuilder(command)
                .redirectErrorStream(true)
                .start();

            boolean finished = process.waitFor(3, TimeUnit.SECONDS);
            if (!finished) {
                process.destroyForcibly();
                return null;
            }

            String output = new String(process.getInputStream().readAllBytes(), StandardCharsets.UTF_8).trim();
            if (output.isBlank()) {
                return null;
            }

            int newlineIdx = output.indexOf('\n');
            String firstLine = newlineIdx >= 0 ? output.substring(0, newlineIdx).trim() : output;
            return firstLine.isBlank() ? null : firstLine;
        } catch (Exception ignored) {
            return null;
        } finally {
            if (process != null) {
                process.destroy();
            }
        }
    }

    private static long detectTotalPhysicalMemoryBytes() {
        try {
            java.lang.management.OperatingSystemMXBean osBean = ManagementFactory.getOperatingSystemMXBean();
            if (osBean instanceof com.sun.management.OperatingSystemMXBean sunOsBean) {
                return sunOsBean.getTotalMemorySize();
            }
        } catch (Throwable ignored) {
            // Best effort only.
        }
        return -1;
    }
}