#include "doctest/doctest.h"
#include "fgc/FileLogSink.h"

#include <algorithm>
#include <filesystem>
#include <fstream>
#include <string>
#include <vector>

#include <unistd.h>

using namespace fgc;
namespace fs = std::filesystem;

namespace {

// A scratch directory per test case, removed on the way out even if a REQUIRE
// aborts the body.
struct TempDir {
    fs::path path;
    explicit TempDir(const char* tag) {
        path = fs::temp_directory_path() /
               ("fgc-log-test-" + std::string(tag) + "-" + std::to_string(::getpid()));
        fs::remove_all(path);
        fs::create_directories(path);
    }
    ~TempDir() {
        std::error_code ec;
        fs::remove_all(path, ec);
    }
};

FileLogPolicy policyIn(const TempDir& d, long long max_bytes, int keep) {
    FileLogPolicy p;
    p.dir        = d.path.string();
    p.max_bytes  = max_bytes;
    p.keep_files = keep;
    return p;
}

std::string read(const std::string& path) {
    std::ifstream in(path, std::ios::binary);
    return {std::istreambuf_iterator<char>(in), std::istreambuf_iterator<char>()};
}

// Every <prefix>_*.log in the directory, oldest first.
std::vector<std::string> filesOldestFirst(const TempDir& d) {
    std::vector<std::string> out;
    for (const auto& e : fs::directory_iterator(d.path))
        if (e.path().extension() == ".log") out.push_back(e.path().filename().string());
    std::sort(out.begin(), out.end());
    return out;
}

}  // namespace

TEST_CASE("a line lands in the file, dated, under a self-describing header") {
    TempDir d("basic");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 0, 0), "=== header ==="));
    s.write(LogLevel::Info, LogCat::None, "12:00:00.000 [INFO ] hello");
    s.close();

    const std::string text = read((d.path / filesOldestFirst(d).front()).string());
    CHECK(text.find("=== header ===") != std::string::npos);
    CHECK(text.find("[INFO ] hello") != std::string::npos);
    // Logger's own stamp carries no date, so the sink prepends one - otherwise a
    // file spanning midnight is ambiguous. Check the shape, not just a dash.
    const auto at = text.find("12:00:00.000");
    REQUIRE(at != std::string::npos);
    REQUIRE(at >= 11);
    const std::string date = text.substr(at - 11, 11);
    CHECK(date.size() == 11);
    CHECK(date[4] == '-');
    CHECK(date[7] == '-');
    CHECK(date[10] == ' ');
}

TEST_CASE("rotation fires at the boundary, and never splits a line") {
    TempDir d("rotate");
    FileLogSink s;
    // Header empty so the budget is entirely lines.
    REQUIRE(s.open(policyIn(d, 200, 0), ""));

    // Each written record is "YYYY-MM-DD " (11) + line + "\n".
    const std::string line(50, 'x');
    for (int i = 0; i < 10; ++i) s.write(LogLevel::Info, LogCat::None, line);
    s.close();

    const auto files = filesOldestFirst(d);
    REQUIRE(files.size() > 1);
    for (const auto& f : files) {
        const std::string text = read((d.path / f).string());
        CHECK(text.size() <= 200);
        // A record is only ever whole: the file ends on a newline and contains
        // no truncated 50-char run.
        CHECK(text.back() == '\n');
    }
}

TEST_CASE("segment names sort chronologically") {
    // The bug this guards: with an unpadded suffix the FIRST segment is
    // "<base>.log" and later ones "<base>.1.log". Lexicographically 'l' > '1',
    // so the oldest file sorted as the newest and pruning deleted the wrong end.
    TempDir d("sort");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 120, 0), ""));
    for (int i = 0; i < 6; ++i) s.write(LogLevel::Info, LogCat::None, std::string(40, 'a' + i));
    s.close();

    auto files = filesOldestFirst(d);
    REQUIRE(files.size() >= 3);
    // Written in order a.., b.., c..; sorted by name, the contents must follow.
    const std::string first  = read((d.path / files.front()).string());
    const std::string second = read((d.path / files[1]).string());
    CHECK(first.find(std::string(40, 'a')) != std::string::npos);
    CHECK(second.find(std::string(40, 'a')) == std::string::npos);

    // And the sink's own newest-first view must be the exact reverse.
    auto newest = FileLogSink::existingFiles(policyIn(d, 120, 0));
    REQUIRE(newest.size() == files.size());
    CHECK(fs::path(newest.front()).filename().string() == files.back());
}

TEST_CASE("retention keeps the newest N and deletes the oldest") {
    TempDir d("prune");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 120, 3), ""));
    for (int i = 0; i < 20; ++i) s.write(LogLevel::Info, LogCat::None, std::string(40, 'q'));
    s.close();

    auto files = filesOldestFirst(d);
    CHECK(files.size() == 3);
    // The survivors must be the LAST three segments, not the first three.
    CHECK(files.back().find(".log") != std::string::npos);
    auto newest = FileLogSink::existingFiles(policyIn(d, 120, 3));
    CHECK(newest.size() == 3);
}

TEST_CASE("a max_bytes smaller than the header does not rotate forever") {
    // Without the "at least one line in this file" guard, the header alone
    // exceeds the cap, so every write rotates and the whole retention set is
    // consumed in a loop - unbounded file churn from one misconfigured key.
    TempDir d("tinycap");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 10, 0), "=== a header much longer than ten bytes ==="));
    for (int i = 0; i < 5; ++i) s.write(LogLevel::Info, LogCat::None, "some line");
    s.close();

    // Five writes, each in its own file because the cap is tiny - but exactly
    // five, not hundreds.
    CHECK(filesOldestFirst(d).size() <= 6);
}

TEST_CASE("a single line longer than max_bytes still lands, whole, and terminates") {
    TempDir d("oversize");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 50, 0), ""));
    const std::string huge(500, 'z');
    s.write(LogLevel::Info, LogCat::None, "first");
    s.write(LogLevel::Info, LogCat::None, huge);
    s.close();

    bool found = false;
    for (const auto& f : filesOldestFirst(d))
        if (read((d.path / f).string()).find(huge) != std::string::npos) found = true;
    CHECK(found);
}

TEST_CASE("the header is re-emitted after each rotation") {
    TempDir d("hdr");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 160, 0), "=== HDR ==="));
    for (int i = 0; i < 8; ++i) s.write(LogLevel::Info, LogCat::None, std::string(40, 'h'));
    s.close();

    const auto files = filesOldestFirst(d);
    REQUIRE(files.size() > 1);
    for (const auto& f : files)
        CHECK(read((d.path / f).string()).rfind("=== HDR ===", 0) == 0);
}

TEST_CASE("an unopenable path fails cleanly and writes become no-ops") {
    // The sink runs inside Logger's lock and must never throw or log; a failure
    // has to be latched and reported by polling instead.
    TempDir d("fail");
    const fs::path blocker = d.path / "blocked";
    { std::ofstream(blocker) << "not a directory"; }

    FileLogPolicy p = policyIn(d, 0, 0);
    p.dir           = (blocker / "sub").string();   // parent is a regular file

    FileLogSink s;
    CHECK_FALSE(s.open(p, "hdr"));
    CHECK(s.failed());
    CHECK_FALSE(s.lastError().empty());
    CHECK_NOTHROW(s.write(LogLevel::Error, LogCat::None, "after failure"));
    CHECK_FALSE(s.isOpen());
}

TEST_CASE("the prefix cannot be confused with the self-test reports") {
    // Application::latestPriorTestReport() scans this same directory for
    // test_*.log and takes the lexicographically greatest. Our files must not
    // appear in that scan.
    TempDir d("prefix");
    FileLogSink s;
    REQUIRE(s.open(policyIn(d, 0, 0), ""));
    s.write(LogLevel::Info, LogCat::None, "x");
    s.close();

    for (const auto& f : filesOldestFirst(d)) {
        CHECK(f.rfind("fgc_", 0) == 0);
        CHECK(f.rfind("test_", 0) != 0);
    }
}