/*
 * This file is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Author: Siddharth Bharat Purohit
 */

#include <AP_HAL/AP_HAL.h>

#if HAL_ENABLE_DRONECAN_DRIVERS

#include "AP_DroneCAN_DNA_Server.h"
#include "AP_DroneCAN.h"
#include <StorageManager/StorageManager.h>
#include <AP_Math/AP_Math.h>
#include <GCS_MAVLink/GCS.h>
#include <AP_Logger/AP_Logger.h>
#include <AP_BoardConfig/AP_BoardConfig.h>
#include <stdio.h>
extern const AP_HAL::HAL& hal;

// FORMAT REVISION DREAMS (things to address if the NodeRecord needs to be changed substantially)
// * have DNA server accept only a 16 byte local UID to avoid overhead from variable sized hash
// * have a real empty flag for entries and/or use a CRC which is not zero for an input of all zeros
// * fix FNV-1a hash folding to be to 48 bits (6 bytes) instead of 56

#define NODERECORD_MAGIC 0xAC01
#define NODERECORD_MAGIC_LEN 2 // uint16_t
#define MAX_NODE_ID    125
#define NODERECORD_LOC(node_id) ((node_id * sizeof(NodeRecord)) + NODERECORD_MAGIC_LEN)

#define debug_dronecan(level_debug, fmt, args...) do { AP::can().log_text(level_debug, "DroneCAN", fmt, ##args); } while (0)

// database is currently shared by all DNA servers
AP_DroneCAN_DNA_Server::Database AP_DroneCAN_DNA_Server::db;

// initialize database (storage accessor is always replaced with the one supplied)
void AP_DroneCAN_DNA_Server::Database::init(StorageAccess *storage_)
{
    // storage size must be synced with StorageCANDNA entry in StorageManager.cpp
    static_assert(NODERECORD_LOC(MAX_NODE_ID+1) <= 1024, "DNA storage too small");

    // might be called from multiple threads if multiple servers use the same database
    WITH_SEMAPHORE(sem);

    storage = storage_; // use supplied accessor

    // validate magic number
    uint16_t magic = storage->read_uint16(0);
    if (magic != NODERECORD_MAGIC) {
        reset(); // resetting the database will put the magic back
    }

    // check and note each possible node ID's registration's presence
    for (uint8_t i = 1; i <= MAX_NODE_ID; i++) {
        if (check_registration(i)) {
            node_registered.set(i);
        }
    }
}

// remove all registrations from the database
void AP_DroneCAN_DNA_Server::Database::reset()
{
    WITH_SEMAPHORE(sem);

    NodeRecord record;
    memset(&record, 0, sizeof(record));
    node_registered.clearall();

    // all-zero record means no registration
    // ensure node ID 0 is cleared even if we can't use it so we know the state
    for (uint8_t i = 0; i <= MAX_NODE_ID; i++) {
        write_record(record, i);
    }

    // mark the magic at the start to indicate a valid (and reset) database
    storage->write_uint16(0, NODERECORD_MAGIC);
}

// handle initializing the server with its own node ID and unique ID
void AP_DroneCAN_DNA_Server::Database::init_server(uint8_t node_id, const uint8_t own_unique_id[], uint8_t own_unique_id_len)
{
    WITH_SEMAPHORE(sem);

    // ensure that its node ID and unique ID match in the database
    const uint8_t stored_own_node_id = find_node_id(own_unique_id, own_unique_id_len);
    static bool reset_done;
    if (stored_own_node_id != node_id) { // cannot match if its unique ID was not found
        // we have no record of its unique ID, do a reset
        if (!reset_done) {
            // only reset once per power cycle else we could wipe other servers' registrations
            reset();
            reset_done = true;
        }
        create_registration(node_id, own_unique_id, own_unique_id_len);
    }
}

// handle processing the node info message. returns true if from a duplicate node
bool AP_DroneCAN_DNA_Server::Database::handle_node_info(uint8_t source_node_id, const uint8_t unique_id[])
{
    WITH_SEMAPHORE(sem);

    if (is_registered(source_node_id)) {
        // this device's node ID is associated with a different unique ID
        if (source_node_id != find_node_id(unique_id, 16)) {
            return true; // so raise as duplicate
        }
    } else {
        // we don't know about this node ID, let's register it
        uint8_t prev_node_id = find_node_id(unique_id, 16); // have we registered this unique ID under a different node ID?
        if (prev_node_id != 0) {
            delete_registration(prev_node_id); // yes, delete old registration
        }
        create_registration(source_node_id, unique_id, 16);
    }
    return false; // not a duplicate
}

// handle the allocation message. returns the allocated node ID, or 0 if allocation failed
uint8_t AP_DroneCAN_DNA_Server::Database::handle_allocation(uint8_t node_id, const uint8_t unique_id[])
{
    WITH_SEMAPHORE(sem);

    uint8_t resp_node_id = find_node_id(unique_id, 16);
    if (resp_node_id == 0) {
        resp_node_id = find_free_node_id(node_id > MAX_NODE_ID ? 0 : node_id);
        if (resp_node_id != 0) {
            create_registration(resp_node_id, unique_id, 16);
        } else {
            GCS_SEND_TEXT(MAV_SEVERITY_ERROR, "UC Node Alloc Failed!");
        }
    }
    return resp_node_id; // will be 0 if not found and not created
}

// search for a free node ID, starting at the preferred ID (which can be 0 if
// none are preferred). returns 0 if none found. based on pseudocode in
// uavcan/protocol/dynamic_node_id/1.Allocation.uavcan
uint8_t AP_DroneCAN_DNA_Server::Database::find_free_node_id(uint8_t preferred)
{
    if (preferred == 0) {
        preferred = MAX_NODE_ID;
    }
    // search for an ID >= preferred
    uint8_t candidate = preferred;
    while (candidate <= MAX_NODE_ID) {
        if (!node_registered.get(candidate)) {
            return candidate;
        }
        candidate++;
    }
    // search for an ID <= preferred
    candidate = preferred;
    while (candidate > 0) {
        if (!node_registered.get(candidate)) {
            return candidate;
        }
        candidate--;
    }
    // no IDs free
    return 0;
}

// retrieve node ID that matches the given unique ID. returns 0 if not found
uint8_t AP_DroneCAN_DNA_Server::Database::find_node_id(const uint8_t unique_id[], uint8_t size)
{
    NodeRecord record, cmp_record;
    compute_uid_hash(cmp_record, unique_id, size);

    for (int i = MAX_NODE_ID; i > 0; i--) {
        if (node_registered.get(i)) {
            read_record(record, i);
            if (memcmp(record.uid_hash, cmp_record.uid_hash, sizeof(NodeRecord::uid_hash)) == 0) {
                return i; // node ID found
            }
        }
    }
    return 0; // not found
}

// fill the given record with the hash of the given unique ID
void AP_DroneCAN_DNA_Server::Database::compute_uid_hash(NodeRecord &record, const uint8_t unique_id[], uint8_t size) const
{
    uint64_t hash = FNV_1_OFFSET_BASIS_64;
    hash_fnv_1a(size, unique_id, &hash);

    // xor-folding per http://www.isthe.com/chongo/tech/comp/fnv/
    hash = (hash>>56) ^ (hash&(((uint64_t)1<<56)-1)); // 56 should be 48 since we use 6 bytes

    // write it to ret
    for (uint8_t i=0; i<6; i++) {
        record.uid_hash[i] = (hash >> (8*i)) & 0xff;
    }
}

// create the registration for the given node ID and set its record's unique ID
void AP_DroneCAN_DNA_Server::Database::create_registration(uint8_t node_id, const uint8_t unique_id[], uint8_t size)
{
    NodeRecord record;
    compute_uid_hash(record, unique_id, size);
    // compute and store CRC of the record's data to validate it
    record.crc = crc_crc8(record.uid_hash, sizeof(record.uid_hash));

    write_record(record, node_id);

    node_registered.set(node_id);
}

// delete the given node ID's registration
void AP_DroneCAN_DNA_Server::Database::delete_registration(uint8_t node_id)
{
    if (node_id > MAX_NODE_ID) {
        return;
    }

    NodeRecord record;

    // all-zero record means no registration
    memset(&record, 0, sizeof(record));
    write_record(record, node_id);
    node_registered.clear(node_id);
}

// return true if the given node ID has a registration
bool AP_DroneCAN_DNA_Server::Database::check_registration(uint8_t node_id)
{
    NodeRecord record;
    read_record(record, node_id);

    uint8_t empty_uid[sizeof(NodeRecord::uid_hash)] {};
    uint8_t crc = crc_crc8(record.uid_hash, sizeof(record.uid_hash));
    if (crc == record.crc && memcmp(&record.uid_hash[0], &empty_uid[0], sizeof(empty_uid)) != 0) {
        return true; // CRC matches and UID hash is not all zero
    }
    return false;
}

// read the given node ID's registration's record
void AP_DroneCAN_DNA_Server::Database::read_record(NodeRecord &record, uint8_t node_id)
{
    if (node_id > MAX_NODE_ID) {
        return;
    }

    storage->read_block(&record, NODERECORD_LOC(node_id), sizeof(NodeRecord));
}

// write the given node ID's registration's record
void AP_DroneCAN_DNA_Server::Database::write_record(const NodeRecord &record, uint8_t node_id)
{
    if (node_id > MAX_NODE_ID) {
        return;
    }

    storage->write_block(NODERECORD_LOC(node_id), &record, sizeof(NodeRecord));
}


AP_DroneCAN_DNA_Server::AP_DroneCAN_DNA_Server(AP_DroneCAN &ap_dronecan, CanardInterface &canard_iface, uint8_t driver_index) :
    _ap_dronecan(ap_dronecan),
    _canard_iface(canard_iface),
    storage(StorageManager::StorageCANDNA),
    allocation_sub(allocation_cb, driver_index),
    node_status_sub(node_status_cb, driver_index),
    node_info_client(_canard_iface, node_info_cb) {}

/* Initialises Publishers for respective UAVCAN Instance
Also resets the Server Record in case there is a mismatch
between specified node id and unique id against the existing
Server Record. */
bool AP_DroneCAN_DNA_Server::init(uint8_t own_unique_id[], uint8_t own_unique_id_len, uint8_t node_id)
{
    //Read the details from AP_DroneCAN
    server_state = HEALTHY;

    db.init(&storage); // initialize the database with our accessor

    if (_ap_dronecan.check_and_reset_option(AP_DroneCAN::Options::DNA_CLEAR_DATABASE)) {
        GCS_SEND_TEXT(MAV_SEVERITY_INFO, "UC DNA database reset");
        db.reset();
    }

    db.init_server(node_id, own_unique_id, own_unique_id_len);

    /* Also add to seen node id this is to verify
    if any duplicates are on the bus carrying our Node ID */
    node_seen.set(node_id);
    node_verified.set(node_id);
    node_healthy.set(node_id);
    self_node_id = node_id;
    return true;
}

/* Run through the list of seen node ids for verification no more
than once per 5 second. We continually verify the nodes in our 
seen list, So that we can raise issue if there are duplicates
on the bus. */
void AP_DroneCAN_DNA_Server::verify_nodes()
{
    uint32_t now = AP_HAL::millis();
    if ((now - last_verification_request) < 5000) {
        return;
    }

#if HAL_LOGGING_ENABLED
    uint8_t log_count = AP::logger().get_log_start_count();
    if (log_count != last_logging_count) {
        last_logging_count = log_count;
        node_logged.clearall();
    }
#endif

    //Check if we got acknowledgement from previous request
    //except for requests using our own node_id
    if (curr_verifying_node == self_node_id) {
        nodeInfo_resp_rcvd = true;
    }

    if (!nodeInfo_resp_rcvd) {
        /* Also notify GCS about this
        Reason for this could be either the node was disconnected
        Or a node with conflicting ID appeared and is sending response
        at the same time. */
        node_verified.clear(curr_verifying_node);
    }

    last_verification_request = now;
    //Find the next registered Node ID to be verified.
    for (uint8_t i = 0; i <= MAX_NODE_ID; i++) {
        curr_verifying_node = (curr_verifying_node + 1) % (MAX_NODE_ID + 1);
        if ((curr_verifying_node == self_node_id) || (curr_verifying_node == 0)) {
            continue;
        }
        if (node_seen.get(curr_verifying_node)) {
            break;
        }
    }
    if (db.is_registered(curr_verifying_node)) {
        uavcan_protocol_GetNodeInfoRequest request;
        node_info_client.request(curr_verifying_node, request);
        nodeInfo_resp_rcvd = false;
    }
}

/* Handles Node Status Message, adds to the Seen Node list
Also starts the Service call for Node Info to complete the
Verification process. */
void AP_DroneCAN_DNA_Server::handleNodeStatus(const CanardRxTransfer& transfer, const uavcan_protocol_NodeStatus& msg)
{
    if (transfer.source_node_id > MAX_NODE_ID || transfer.source_node_id == 0) {
        return;
    }
    if ((msg.health != UAVCAN_PROTOCOL_NODESTATUS_HEALTH_OK ||
        msg.mode != UAVCAN_PROTOCOL_NODESTATUS_MODE_OPERATIONAL) &&
        !_ap_dronecan.option_is_set(AP_DroneCAN::Options::DNA_IGNORE_UNHEALTHY_NODE)) {
        //if node is not healthy or operational, clear resp health mask, and set fault_node_id
        fault_node_id = transfer.source_node_id;
        server_state = NODE_STATUS_UNHEALTHY;
        node_healthy.clear(transfer.source_node_id);
    } else {
        node_healthy.set(transfer.source_node_id);
        if (node_healthy == node_verified) {
            server_state = HEALTHY;
        }
    }
    if (!node_verified.get(transfer.source_node_id)) {
        //immediately begin verification of the node_id
        uavcan_protocol_GetNodeInfoRequest request;
        node_info_client.request(transfer.source_node_id, request);
    }
    //Add node to seen list if not seen before
    node_seen.set(transfer.source_node_id);
}

/* Node Info message handler
Handle responses from GetNodeInfo Request. We verify the node info
against our records. Marks Verification mask if already recorded,
Or register if the node id is available and not recorded for the
received Unique ID */
void AP_DroneCAN_DNA_Server::handleNodeInfo(const CanardRxTransfer& transfer, const uavcan_protocol_GetNodeInfoResponse& rsp)
{
    if (transfer.source_node_id > MAX_NODE_ID || transfer.source_node_id == 0) {
        return;
    }
    /*
      if we haven't logged this node then log it now
     */
#if HAL_LOGGING_ENABLED
    if (!node_logged.get(transfer.source_node_id) && AP::logger().logging_started()) {
        node_logged.set(transfer.source_node_id);
        uint64_t uid[2];
        memcpy(uid, rsp.hardware_version.unique_id, sizeof(rsp.hardware_version.unique_id));
        // @LoggerMessage: CAND
        // @Description: Info from GetNodeInfo request
        // @Field: TimeUS: Time since system startup
        // @Field: Driver: Driver index
        // @Field: NodeId: Node ID
        // @Field: UID1: Hardware ID, part 1
        // @Field: UID2: Hardware ID, part 2
        // @Field: Name: Name string
        // @Field: Major: major revision id
        // @Field: Minor: minor revision id
        // @Field: Version: AP_Periph git hash
        AP::logger().Write("CAND", "TimeUS,Driver,NodeId,UID1,UID2,Name,Major,Minor,Version",
                           "s-#------", "F--------", "QBBQQZBBI",
                           AP_HAL::micros64(),
                           _ap_dronecan.get_driver_index(),
                           transfer.source_node_id,
                           uid[0], uid[1],
                           rsp.name.data,
                           rsp.software_version.major,
                           rsp.software_version.minor,
                           rsp.software_version.vcs_commit);
    }
#endif

    bool duplicate = db.handle_node_info(transfer.source_node_id, rsp.hardware_version.unique_id);
    if (duplicate) {
        if (!_ap_dronecan.option_is_set(AP_DroneCAN::Options::DNA_IGNORE_DUPLICATE_NODE)) {
            /* This is a device with node_id already registered
            for another device */
            server_state = DUPLICATE_NODES;
            fault_node_id = transfer.source_node_id;
            memcpy(fault_node_name, rsp.name.data, sizeof(fault_node_name));
        }
    } else {
        //Verify as well
        node_verified.set(transfer.source_node_id);
        if (transfer.source_node_id == curr_verifying_node) {
            nodeInfo_resp_rcvd = true;
        }
    }
}

/* Handle the allocation message from the devices supporting
dynamic node allocation. */
void AP_DroneCAN_DNA_Server::handleAllocation(const CanardRxTransfer& transfer, const uavcan_protocol_dynamic_node_id_Allocation& msg)
{
    if (transfer.source_node_id != 0) {
        //Ignore Allocation messages that are not DNA requests
        return;
    }
    uint32_t now = AP_HAL::millis();

    if (rcvd_unique_id_offset == 0 ||
        (now - last_alloc_msg_ms) > 500) {
        if (msg.first_part_of_unique_id) {
            rcvd_unique_id_offset = 0;
            memset(rcvd_unique_id, 0, sizeof(rcvd_unique_id));
        } else {
            //we are only accepting first part
            return;
        }
    } else if (msg.first_part_of_unique_id) {
        // we are only accepting follow up messages
        return;
    }

    if (rcvd_unique_id_offset) {
        debug_dronecan(AP_CANManager::LOG_DEBUG, "TIME: %ld  -- Accepting Followup part! %u\n",
                     (long int)AP_HAL::millis(),
                     unsigned((now - last_alloc_msg_ms)));
    } else {
        debug_dronecan(AP_CANManager::LOG_DEBUG, "TIME: %ld  -- Accepting First part! %u\n",
                     (long int)AP_HAL::millis(),
                     unsigned((now - last_alloc_msg_ms)));
    }

    last_alloc_msg_ms = now;
    if ((rcvd_unique_id_offset + msg.unique_id.len) > 16) {
        //This request is malformed, Reset!
        rcvd_unique_id_offset = 0;
        memset(rcvd_unique_id, 0, sizeof(rcvd_unique_id));
        return;
    }

    //copy over the unique_id
    for (uint8_t i=rcvd_unique_id_offset; i<(rcvd_unique_id_offset + msg.unique_id.len); i++) {
        rcvd_unique_id[i] = msg.unique_id.data[i - rcvd_unique_id_offset];
    }
    rcvd_unique_id_offset += msg.unique_id.len;

    //send follow up message
    uavcan_protocol_dynamic_node_id_Allocation rsp {};

    /* Respond with the message containing the received unique ID so far
    or with node id if we successfully allocated one. */
    memcpy(rsp.unique_id.data, rcvd_unique_id, rcvd_unique_id_offset);
    rsp.unique_id.len = rcvd_unique_id_offset;

    if (rcvd_unique_id_offset == 16) {
        //We have received the full Unique ID, time to do allocation
        rsp.node_id = db.handle_allocation(msg.node_id, (const uint8_t*)rcvd_unique_id);
        //reset states as well        
        rcvd_unique_id_offset = 0;
        memset(rcvd_unique_id, 0, sizeof(rcvd_unique_id));
    }

    allocation_pub.broadcast(rsp, false); // never publish allocation message with CAN FD
}

//report the server state, along with failure message if any
bool AP_DroneCAN_DNA_Server::prearm_check(char* fail_msg, uint8_t fail_msg_len) const
{
    switch (server_state) {
    case HEALTHY:
        return true;
    case DUPLICATE_NODES: {
        if (_ap_dronecan.option_is_set(AP_DroneCAN::Options::DNA_IGNORE_DUPLICATE_NODE)) {
            // ignore error
            return true;
        }
        snprintf(fail_msg, fail_msg_len, "Duplicate Node %s../%d!", fault_node_name, fault_node_id);
        return false;
    }
    case NODE_STATUS_UNHEALTHY: {
        if (_ap_dronecan.option_is_set(AP_DroneCAN::Options::DNA_IGNORE_UNHEALTHY_NODE)) {
            // ignore error
            return true;
        }
        snprintf(fail_msg, fail_msg_len, "Node %d unhealthy!", fault_node_id);
        return false;
    }
    }
    // should never get; compiler should enforce all server_states are covered
    return false;
}

#endif //HAL_NUM_CAN_IFACES