// Tests for logos_host_core.h — the host-side veneer over liblogos'
// logos_core_* C API.
//
// The C API is `extern "C"`, so this translation unit DEFINES it itself. That
// is the whole reason these tests can be meaningful without a running core:
// the interesting behaviour of the veneer is what it does with the memory
// liblogos hands back, and a stub lets us assert that directly — including the
// `delete[]`-not-`free()` rule, which is the single most-copied piece of
// knowledge across the host repos and the one a real core cannot check for us.
//
// The stubs allocate EXACTLY as liblogos does (`new char*[]` for the array,
// `new char[]` for each element and for single-string returns). If the veneer
// ever switched to free()/delete, this suite would fail under ASan rather than
// silently corrupting the heap in production.

#include "logos_host_core.h"

#include <gtest/gtest.h>

#include <cstring>
#include <string>
#include <vector>

namespace {

// ── stub state, reset per test ───────────────────────────────────────────────
struct CoreStub {
    int  initCalls = 0;
    int  startCalls = 0;
    int  cleanupCalls = 0;
    std::vector<std::string> modulesDirs;
    std::string persistenceBasePath;
    std::string accessPolicy;
    bool accessPolicySet = false;
    std::vector<std::pair<std::string, std::string>> transports;
    // Records the ORDER in which the C API was touched, so the ordering
    // contract ("all config strictly before start") can be asserted rather
    // than assumed.
    std::vector<std::string> callOrder;

    std::vector<std::string> known{"alpha", "beta", "gamma"};
    std::vector<std::string> loaded{"alpha"};
    // The REAL contract process-stats emits (src/process_stats.cpp:157-161).
    // This previously stubbed {"cpu":..,"memory":..}, keys nothing produces, so
    // it validated the parser's bug instead of the producer's format.
    std::string statsJson =
        R"([{"name":"alpha","cpu_percent":12.5,"cpu_time_seconds":3.5,"memory_mb":4096.0}])";
    bool tokenPresent = true;
    int  lastLoadWithDeps = -1;
    int  lastUnloadWithDependents = -1;
    bool loadSucceeds = true;
};

CoreStub* g = nullptr;

char* dupC(const std::string& s)
{
    char* r = new char[s.size() + 1];   // matches liblogos (logos_core.cpp:85)
    std::memcpy(r, s.c_str(), s.size() + 1);
    return r;
}

char** dupCArray(const std::vector<std::string>& xs)
{
    char** a = new char*[xs.size() + 1]; // matches toNullTerminatedArray
    for (std::size_t i = 0; i < xs.size(); ++i) a[i] = dupC(xs[i]);
    a[xs.size()] = nullptr;
    return a;
}

class HostCoreTest : public ::testing::Test {
protected:
    void SetUp() override { stub = CoreStub{}; g = &stub; }
    void TearDown() override { g = nullptr; }
    CoreStub stub;
};

} // namespace

extern "C" {
void logos_core_init(int, char**)                 { ++g->initCalls;    g->callOrder.push_back("init"); }
void logos_core_start()                           { ++g->startCalls;   g->callOrder.push_back("start"); }
void logos_core_cleanup()                         { ++g->cleanupCalls; g->callOrder.push_back("cleanup"); }
void logos_core_add_modules_dir(const char* d)    { g->modulesDirs.emplace_back(d); g->callOrder.push_back("add_dir"); }
void logos_core_set_persistence_base_path(const char* p) { g->persistenceBasePath = p; g->callOrder.push_back("persistence"); }
void logos_core_set_access_policy(const char* p)  { g->accessPolicySet = true; g->accessPolicy = p ? p : ""; g->callOrder.push_back("policy"); }
void logos_core_set_module_transports(const char* m, const char* j) { g->transports.emplace_back(m, j); g->callOrder.push_back("transports"); }
void logos_core_refresh_modules()                 { g->callOrder.push_back("refresh"); }

char** logos_core_get_known_modules()             { return dupCArray(g->known); }
char** logos_core_get_loaded_modules()            { return dupCArray(g->loaded); }
char** logos_core_get_module_dependencies(const char*, bool r) { return dupCArray(r ? std::vector<std::string>{"d1","d2"} : std::vector<std::string>{"d1"}); }
char** logos_core_get_module_dependents(const char*, bool)     { return dupCArray({}); }

int logos_core_load_module(const char*, bool withDeps)     { g->lastLoadWithDeps = withDeps ? 1 : 0; return g->loadSucceeds ? 1 : 0; }
int logos_core_unload_module(const char*, bool withDepdts) { g->lastUnloadWithDependents = withDepdts ? 1 : 0; return 1; }

char* logos_core_get_modules_info()               { return dupC("[]"); }
char* logos_core_process_module(const char*)      { return dupC("processed"); }
char* logos_core_get_token(const char*)           { return g->tokenPresent ? dupC("tok-123") : nullptr; }
char* logos_core_get_module_stats()               { return g->statsJson.empty() ? nullptr : dupC(g->statsJson); }
}

namespace {

using logos::host::LogosCore;

LogosCore::Config emptyConfig() { return LogosCore::Config{}; }

// ── lifecycle ────────────────────────────────────────────────────────────────

TEST_F(HostCoreTest, ConstructionInitialisesAndDestructionCleansUpExactlyOnce)
{
    {
        LogosCore core(0, nullptr, emptyConfig());
        EXPECT_EQ(stub.initCalls, 1);
        EXPECT_EQ(stub.cleanupCalls, 0);
    }
    EXPECT_EQ(stub.cleanupCalls, 1);
}

TEST_F(HostCoreTest, EveryPreStartSettingIsAppliedBeforeStart)
{
    LogosCore::Config cfg;
    cfg.modulesDirs = {"/one", "/two"};
    cfg.persistenceBasePath = "/persist";
    cfg.accessPolicyJson = std::string(R"({"mode":"enforce"})");
    cfg.moduleTransports = {{"mod_a", "[]"}};

    LogosCore core(0, nullptr, std::move(cfg));
    core.start();

    EXPECT_EQ(stub.modulesDirs, (std::vector<std::string>{"/one", "/two"}));
    EXPECT_EQ(stub.persistenceBasePath, "/persist");
    EXPECT_TRUE(stub.accessPolicySet);
    ASSERT_EQ(stub.transports.size(), 1u);
    EXPECT_EQ(stub.transports[0].first, "mod_a");

    // The ordering contract, asserted rather than trusted: "start" must be the
    // LAST thing, with every configuration call ahead of it. This is the
    // constraint logos_core.h states only in comments.
    const auto startAt = std::find(stub.callOrder.begin(), stub.callOrder.end(), "start");
    ASSERT_NE(startAt, stub.callOrder.end());
    EXPECT_EQ(startAt + 1, stub.callOrder.end())
        << "something was configured after start()";
    EXPECT_EQ(stub.callOrder.front(), "init");
}

TEST_F(HostCoreTest, AbsentOptionalSettingsAreNotPushedAtAll)
{
    // nullopt policy must install NO policy — distinct from an empty one,
    // because liblogos treats "no policy" as unrestricted.
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_FALSE(stub.accessPolicySet);
    EXPECT_TRUE(stub.modulesDirs.empty());
    EXPECT_TRUE(stub.persistenceBasePath.empty());
}

TEST_F(HostCoreTest, EmptyAccessPolicyStringIsStillInstalled)
{
    LogosCore::Config cfg;
    cfg.accessPolicyJson = std::string("");
    LogosCore core(0, nullptr, std::move(cfg));
    EXPECT_TRUE(stub.accessPolicySet) << "an explicitly empty policy is a choice, not an absence";
}

// ── ownership: the char**/char* draining ────────────────────────────────────

TEST_F(HostCoreTest, StringArraysAreDrainedIntoOwningVectors)
{
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_EQ(core.knownModules(), (std::vector<std::string>{"alpha", "beta", "gamma"}));
    EXPECT_EQ(core.loadedModules(), (std::vector<std::string>{"alpha"}));
}

TEST_F(HostCoreTest, EmptyArrayDrainsToEmptyVectorRatherThanCrashing)
{
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_TRUE(core.dependents("alpha").empty());
}

TEST_F(HostCoreTest, RecursiveFlagReachesTheCApi)
{
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_EQ(core.dependencies("alpha", /*recursive=*/false).size(), 1u);
    EXPECT_EQ(core.dependencies("alpha", /*recursive=*/true).size(), 2u);
}

TEST_F(HostCoreTest, NullCStringBecomesNulloptNotEmptyString)
{
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_EQ(core.token("core").value(), "tok-123");

    stub.tokenPresent = false;
    EXPECT_FALSE(core.token("core").has_value())
        << "a NULL return means absent, and must not be flattened to \"\"";
}

// ── load/unload defaults ────────────────────────────────────────────────────

TEST_F(HostCoreTest, LoadDefaultsToResolvingDependenciesAndUnloadDoesNotCascade)
{
    LogosCore core(0, nullptr, emptyConfig());

    EXPECT_TRUE(core.loadModule("alpha"));
    EXPECT_EQ(stub.lastLoadWithDeps, 1) << "a host almost always wants the dependency graph";

    EXPECT_TRUE(core.unloadModule("alpha"));
    EXPECT_EQ(stub.lastUnloadWithDependents, 0)
        << "cascading unload must be opt-in; it breaks live dependents";

    core.unloadModule("alpha", /*withDependents=*/true);
    EXPECT_EQ(stub.lastUnloadWithDependents, 1);
}

TEST_F(HostCoreTest, LoadFailureIsReportedAsFalse)
{
    stub.loadSucceeds = false;
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_FALSE(core.loadModule("alpha"))
        << "logos_core_load_module returns int; only ==1 is success";
}

// ── stats: the blob parse ───────────────────────────────────────────────────

TEST_F(HostCoreTest, StatsAreIndexedOutOfTheSingleBlob)
{
    LogosCore core(0, nullptr, emptyConfig());
    const auto s = core.stats("alpha");
    ASSERT_TRUE(s.has_value());
    EXPECT_EQ(s->name, "alpha");
    EXPECT_DOUBLE_EQ(s->cpuPercent, 12.5);
    EXPECT_DOUBLE_EQ(s->memoryMb, 4096.0);
    EXPECT_DOUBLE_EQ(s->cpuTimeSeconds, 3.5);
    EXPECT_EQ(s->raw["name"], "alpha") << "the raw entry stays reachable";
}

TEST_F(HostCoreTest, StatsForAnUnloadedModuleIsNullopt)
{
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_FALSE(core.stats("not-loaded").has_value());
}

TEST_F(HostCoreTest, MalformedStatsJsonYieldsEmptyRatherThanThrowing)
{
    // A host polls this on a timer; a parse failure must not take the process
    // down. nlohmann is invoked with allow_exceptions=false for this reason.
    stub.statsJson = "{not json";
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_TRUE(core.allStats().empty());
    EXPECT_FALSE(core.stats("alpha").has_value());
}

TEST_F(HostCoreTest, NullStatsYieldsEmpty)
{
    stub.statsJson.clear();   // stub returns nullptr
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_TRUE(core.allStats().empty());
}

TEST_F(HostCoreTest, NonArrayStatsIsRejected)
{
    stub.statsJson = R"({"name":"alpha"})";   // object, not array
    LogosCore core(0, nullptr, emptyConfig());
    EXPECT_TRUE(core.allStats().empty());
}

} // namespace