// gKeyMapper daemon - remaps G1..G9 on the Logitech G910.
//
// It reads the raw HID reports of the keyboard's vendor interface, looks up the
// configured action and replays it ("key" via uinput, "command" via exec).
//
// Milestones: M0 (shared core), M1 (device bring-up/decoding), M2 (action
// execution), M3 (config watching + lifecycle), M4 (D-Bus GUI channel) and
// M5 (hot-plug, repeat/chord decoding, error reporting to the GUI) are done.

#include <algorithm>
#include <csignal>
#include <cstdint>
#include <cstdio>
#include <string>
#include <vector>

#include "action.h"
#include "config_watch.h"
#include "device_tables.h"
#include "g910_device.h"
#include "ipc_dbus.h"
#include "mapping.h"

namespace {

volatile std::sig_atomic_t g_running = 1;
volatile std::sig_atomic_t g_reload = 0;

void handle_stop(int /*signum*/) {
    g_running = 0;
}

void handle_reload(int /*signum*/) {
    g_reload = 1;
}

// How often the daemon looks for the keyboard while it has none. The loop keeps
// pumping D-Bus and the config watch in between, so the control plane stays
// responsive and GetStatus can report that there is no device.
constexpr gint64 kReopenIntervalUs = 2 * 1000 * 1000;
constexpr int kReopenSleepMs = 200;

} // namespace

int main(int argc, char** argv) {
    std::signal(SIGINT, handle_stop);
    std::signal(SIGTERM, handle_stop);
    std::signal(SIGHUP, handle_reload);
    std::signal(SIGUSR1, handle_reload);
    std::signal(SIGCHLD, SIG_IGN); // auto-reap launched commands

    std::string configPath = gkeymapper::default_config_path();
    if (argc > 1) {
        configPath = argv[1];
    }

    gkeymapper::MappingSet mappings = gkeymapper::parse_mappings("");

    // Reads the config; on failure the previous mappings stay in place, so a
    // transient read error never silently disables every key.
    auto load = [&]() -> bool {
        const bool ok = gkeymapper::load_mappings_file(configPath, mappings);
        std::fprintf(stderr, "gkeymapper-daemon: %s %s\n",
                     ok ? "loaded" : "cannot read", configPath.c_str());
        return ok;
    };
    load();

    // The GUI is the writer; a save is picked up through inotify, SIGHUP/SIGUSR1
    // stay as the fallback for scripts and for systems without inotify.
    gkeymapper::daemon::ConfigWatcher watcher;
    watcher.init(configPath);

    gkeymapper::daemon::ActionRunner actions;
    actions.init();

    // Declared before the IPC service so its status callback can report the
    // device. It is opened only after the name check below: a second instance
    // must not detach the kernel driver from the keyboard the running one uses.
    gkeymapper::daemon::GKeyDevice device;
    const gkeymapper::daemon::DeviceProfile* profile = nullptr;

    // Runs the mapping of G<index+1> (0-based). A real keypress and the D-Bus
    // TestMapping call both go through here, so a test fires exactly the same
    // path. `hold` is set for a real press, where a "keyhold" mapping keeps its
    // keys down until the G key is released; a test always taps. Returns whether
    // there was an action to run.
    auto run_mapping = [&](int index, bool test, bool hold) -> bool {
        if (index < 0 || index >= static_cast<int>(mappings.keys.size())) {
            return false;
        }
        const gkeymapper::Mapping& mapping = mappings.keys[index];
        const bool usable = mapping.type != gkeymapper::ActionType::Disabled &&
                            !mapping.target.empty();
        std::printf("G%d -> %s:%s%s\n", index + 1,
                    gkeymapper::action_type_token(mapping.type), mapping.target.c_str(),
                    test ? " (test)" : "");
        std::fflush(stdout);
        if (usable) {
            if (hold && mapping.type == gkeymapper::ActionType::KeyHold) {
                actions.begin_hold(index, mapping);
            } else {
                actions.run(mapping);
            }
        }
        return usable;
    };

    gkeymapper::daemon::DaemonService service;
    auto reload = [&]() -> bool {
        const bool ok = load();
        service.notify_config_reloaded(ok);
        return ok;
    };
    service.set_reload(reload);
    service.set_device([&]() {
        return profile != nullptr ? std::string(profile->name) : std::string();
    });
    service.set_test([&](int index, std::string& action) {
        if (!run_mapping(index, true, false)) {
            return false;
        }
        const gkeymapper::Mapping& mapping = mappings.keys[index];
        action = std::string(gkeymapper::action_type_token(mapping.type)) + ":" +
                 mapping.target;
        return true;
    });

    switch (service.start(configPath)) {
        case gkeymapper::daemon::StartResult::AlreadyRunning:
            // Two instances would fight over the device and create a second
            // virtual keyboard, so the newcomer gives way.
            std::fprintf(stderr,
                         "gkeymapper-daemon: another instance is already running; "
                         "exiting\n");
            return 0;
        case gkeymapper::daemon::StartResult::NoBus:
        case gkeymapper::daemon::StartResult::Ok:
            break;
    }

    // Opens the keyboard and tells the GUI. Returns false when there is none,
    // which is not an error: the session can start before the keyboard is
    // plugged, and a lost or re-plugged keyboard must not cost the bus name —
    // the GUI would see the daemon as gone and D-Bus activation would start a
    // second one for nothing.
    bool missingReported = false;
    auto open_device = [&](bool quiet) -> bool {
        if (!device.open(quiet)) {
            return false;
        }
        device.disable_binding();
        profile = device.profile();
        service.notify_device_changed(true, profile != nullptr ? profile->name : "");
        missingReported = false;
        return true;
    };

    uint8_t buffer[64];
    uint32_t pressed = 0;   // G keys reported as pressed by the previous report
    gint64 next_open = 0;   // earliest time to look for the keyboard again
    while (g_running) {
        // Control plane first (bounded by the read timeout below), then the
        // keyboard. The loop wakes up at least every read timeout, which also
        // bounds how long a config change takes to be applied.
        service.pump();
        watcher.poll_events();
        if (g_reload || watcher.take_change()) {
            g_reload = 0;
            reload();
        }

        if (!device.is_open()) {
            const gint64 now = g_get_monotonic_time();
            if (now >= next_open) {
                next_open = now + kReopenIntervalUs;
                // The first attempt of an absence explains itself, the retries
                // stay quiet: one line per unplug instead of one per retry.
                if (open_device(missingReported)) {
                    continue; // read from it right away
                }
                if (!missingReported) {
                    missingReported = true;
                    std::fprintf(stderr,
                                 "gkeymapper-daemon: no usable keyboard, will keep "
                                 "looking\n");
                }
            }
            // Sleep briefly instead of the 500 ms read timeout, so a keyboard
            // that appears is picked up sooner and the loop still services the
            // control plane.
            g_usleep(kReopenSleepMs * 1000);
            continue;
        }

        int n = device.read_report(buffer, sizeof(buffer), 500);
        if (n == 0) {
            continue; // no report within the timeout
        }
        if (n < 0) {
            // Lost the keyboard (unplugged, or the kernel took the interface
            // back). Report it and keep looking; the daemon stays up.
            std::fprintf(stderr, "gkeymapper-daemon: read error (%d), device lost\n", n);
            // A held key would stay down forever without its release report.
            actions.release_held();
            service.notify_device_changed(false, profile != nullptr ? profile->name : "");
            device.close();
            profile = nullptr;
            pressed = 0;
            next_open = 0;
            continue;
        }

        if (profile == nullptr) {
            continue;
        }
        uint32_t state = 0;
        if (gkeymapper::daemon::decode_gkey_state(*profile, buffer, n, state)) {
            // Only a *change* of a bit acts: a held key repeats its report, and a
            // chord arrives as one report with several bits set, so every key of
            // it fires exactly once. The falling edge matters for "keyhold",
            // which lets its keys go when the G key comes up.
            const size_t count =
                std::min(mappings.keys.size(), static_cast<size_t>(gkeymapper::kNumKeys));
            for (size_t i = 0; i < count; ++i) {
                const uint32_t bit = 1u << i;
                const bool down = (state & bit) != 0;
                const bool was_down = (pressed & bit) != 0;
                if (down == was_down) {
                    continue;
                }
                if (!down) {
                    // No-op unless this G key holds a "keyhold" mapping.
                    actions.end_hold(static_cast<int>(i));
                    continue;
                }
                const gkeymapper::Mapping& mapping = mappings.keys[i];
                const std::string action =
                    std::string(gkeymapper::action_type_token(mapping.type)) + ":" +
                    mapping.target;
                run_mapping(static_cast<int>(i), false, true);
                service.notify_key_pressed(static_cast<int>(i), action);
            }
            pressed = state;
            continue;
        }

        // Media keys (mute / volume / play) are forwarded unchanged: they are
        // reported only on the interface the daemon holds, so without this they
        // would do nothing at all while it runs (see README). Replaying every
        // report the keyboard sends keeps the behaviour identical to a keyboard
        // the kernel drives itself — including its release report, which carries
        // no bit and is therefore dropped below.
        uint32_t media = 0;
        if (!gkeymapper::daemon::decode_media_key(*profile, buffer, n, media) ||
            media == 0) {
            continue; // memory key, LED or command acknowledgement, or a release
        }
        for (const gkeymapper::daemon::MediaKey& key : profile->mediaKeys) {
            if ((media & key.bit) == 0) {
                continue;
            }
            std::printf("media -> %s\n", key.name);
            std::fflush(stdout);
            actions.tap_key(key.key);
        }
    }

    // Shutting down: a "keyhold" key that is still down belongs to the session,
    // not to the daemon, so let it go before the virtual keyboard disappears.
    actions.release_held();
    service.notify_device_changed(false, profile != nullptr ? profile->name : "");
    service.pump();
    device.close();
    return 0;
}