#ifndef OATPP_AUTHKIT_REPO_AUDIT_LOG_REPOSITORY_HPP
#define OATPP_AUTHKIT_REPO_AUDIT_LOG_REPOSITORY_HPP

// Cross-cutting audit-trail decorator (authkit#11). Emits an `AuditEvent`
// through a consumer-supplied `IAuditSink` on every audited operation.
// Composes naturally with `ScopeGuardRepository` and `TemporalRepository`
// — all three accept an `ActorContext` accessor and stack via the same
// `Repository<T>` interface.

#include "oatpp-authkit/repo/Repository.hpp"
#include "oatpp-authkit/repo/IAuditSink.hpp"
#include "oatpp-authkit/repo/ActorContext.hpp"
#include "oatpp-authkit/repo/TemporalFieldTraits.hpp"
#include "oatpp-authkit/repo/SchemaContract.hpp"

#include "oatpp/core/Types.hpp"

#include <chrono>
#include <cstdint>
#include <exception>
#include <functional>
#include <memory>
#include <set>
#include <string>
#include <utility>

namespace oatpp_authkit::repo {

/**
 * @brief Decorator that audits every mutation flowing through a repository.
 *
 * @section semantics Per-method behaviour
 *
 * - `save(dto)`: if `entity_id` is null, the inner is about to allocate
 *   one — operation is `Create`. If `entity_id` is non-null, the decorator
 *   performs a one-shot `findByEntityId` on the inner *before* delegating;
 *   a hit means `Update`, a miss means `Create` (caller-supplied id, no
 *   row yet). Inner is then called; on success a single event is recorded.
 * - `softDelete(id)`: delegated first; on success a single `Delete` event
 *   is recorded.
 * - `findByEntityId(id)`: delegated first; if `AuditOp::Read` is in the
 *   enabled set, a single `Read` event is recorded with the entity id of
 *   the row that came back (or the requested id on miss — both are
 *   useful for compliance traces).
 * - `list()`: passed through unchanged. Lists are scans; emitting one
 *   event per row is noisy and emitting a single event with no entity id
 *   is half-information. Out of scope for this decorator.
 *
 * @section robustness Sink failures
 *
 * `IAuditSink::record` is called inside a `try/catch`. By default the
 * exception is swallowed — audit logging is best-effort and must not
 * break the user's write path. Pass `sinkErrorHandler(...)` (or supply
 * the optional last constructor arg) to override; the handler returns
 * `true` to rethrow, `false` to swallow.
 *
 * `entityId` for `save` events is read through
 * `TemporalFieldTraits<TDto>::entityId`, so the decorator works for any
 * DTO that registered the trait via `OATPP_AUTHKIT_REGISTER_TEMPORAL`.
 */
template <typename TDto>
class AuditLogRepository : public Repository<TDto> {
public:
    using ActorAccess     = std::function<ActorContext()>;
    using Clock           = std::function<std::int64_t()>;
    using SinkErrorHandler = std::function<bool(const std::exception&)>;

    /// Declarative schema contribution (authkit#14, D-replace).
    /// AuditLog touches no entity-table columns; it owns one sidecar
    /// `audit_log` table fixed across consumers.
    inline static constexpr ColumnSpec kAuditLogColumns[] = {
        {"id",            "INTEGER PRIMARY KEY AUTOINCREMENT"},
        {"actor_user_id", "TEXT"},
        {"entity_type",   "TEXT NOT NULL"},
        {"entity_id",     "TEXT NOT NULL"},
        {"op",            "TEXT NOT NULL"},
        {"timestamp_ms",  "INTEGER NOT NULL"},
    };
    inline static constexpr SidecarTableSpec kSidecars[] = {
        {"audit_log", kAuditLogColumns,
         sizeof(kAuditLogColumns) / sizeof(kAuditLogColumns[0])},
    };
    inline static constexpr DecoratorSchema kSchema = {
        "AuditLogRepository",
        nullptr, 0,
        nullptr, 0,
        kSidecars, sizeof(kSidecars) / sizeof(kSidecars[0]),
    };

    AuditLogRepository(std::shared_ptr<Repository<TDto>>   inner,
                       std::shared_ptr<IAuditSink>         sink,
                       ActorAccess                         currentActor,
                       std::string                         entityType,
                       std::set<AuditOp>                   enabledOps =
                           {AuditOp::Create, AuditOp::Update, AuditOp::Delete},
                       Clock                               clock = {},
                       SinkErrorHandler                    onSinkError = {})
        : m_inner(std::move(inner))
        , m_sink(std::move(sink))
        , m_currentActor(std::move(currentActor))
        , m_entityType(std::move(entityType))
        , m_enabledOps(std::move(enabledOps))
        , m_clock(clock ? std::move(clock) : defaultClock())
        , m_onSinkError(std::move(onSinkError))
    {}

    oatpp::Object<TDto> findByEntityId(const oatpp::String& entityId) override {
        auto row = m_inner->findByEntityId(entityId);
        if (m_enabledOps.count(AuditOp::Read)) {
            // On miss, fall back to the requested id — still useful for
            // compliance. On hit, prefer the id stored on the row.
            std::string id = entityId ? std::string(*entityId) : std::string();
            if (row) {
                auto& rowId = TemporalFieldTraits<TDto>::entityId(row);
                if (rowId) id = std::string(*rowId);
            }
            emit(AuditOp::Read, id);
        }
        return row;
    }

    oatpp::Vector<oatpp::Object<TDto>> list() override {
        return m_inner->list();   // intentionally unaudited — see header doc
    }

    void save(const oatpp::Object<TDto>& dto) override {
        const AuditOp op = classifySave(dto);
        m_inner->save(dto);
        if (m_enabledOps.count(op)) {
            std::string id;
            auto& field = TemporalFieldTraits<TDto>::entityId(dto);
            if (field) id = std::string(*field);
            emit(op, id);
        }
    }

    void softDelete(const oatpp::String& entityId) override {
        m_inner->softDelete(entityId);
        if (m_enabledOps.count(AuditOp::Delete)) {
            emit(AuditOp::Delete, entityId ? std::string(*entityId) : std::string());
        }
    }

private:
    AuditOp classifySave(const oatpp::Object<TDto>& dto) {
        auto& id = TemporalFieldTraits<TDto>::entityId(dto);
        if (!id) return AuditOp::Create;       // inner will allocate the id
        // Caller-supplied id: distinguish Create-with-id vs Update.
        return m_inner->findByEntityId(id) ? AuditOp::Update : AuditOp::Create;
    }

    void emit(AuditOp op, std::string entityId) {
        AuditEvent ev;
        ev.entityType   = m_entityType;
        ev.entityId     = std::move(entityId);
        ev.op           = op;
        ev.timestampMs  = m_clock();
        try {
            ev.actorUserId = m_currentActor().userId;
        } catch (...) {
            // Actor accessor failure shouldn't break the write path either.
            ev.actorUserId.clear();
        }
        try {
            m_sink->record(ev);
        } catch (const std::exception& e) {
            if (m_onSinkError && m_onSinkError(e)) throw;
            // else: swallow — audit logging is best-effort.
        } catch (...) {
            // Non-std::exception — always swallow; the handler signature
            // takes std::exception&, so we cannot route it.
        }
    }

    static Clock defaultClock() {
        return [] {
            using namespace std::chrono;
            return duration_cast<milliseconds>(
                       system_clock::now().time_since_epoch()).count();
        };
    }

    std::shared_ptr<Repository<TDto>>  m_inner;
    std::shared_ptr<IAuditSink>        m_sink;
    ActorAccess                        m_currentActor;
    std::string                        m_entityType;
    std::set<AuditOp>                  m_enabledOps;
    Clock                              m_clock;
    SinkErrorHandler                   m_onSinkError;
};

} // namespace oatpp_authkit::repo

#endif