#include "../pchheader.hpp"
#include "../conf.hpp"
#include "../crypto.hpp"
#include "../p2p/p2p.hpp"
#include "../fbschema/common_helpers.hpp"
#include "../fbschema/ledger_helpers.hpp"
#include "../fbschema/p2pmsg_helpers.hpp"
#include "../hplog.hpp"
#include "ledger_handler.hpp"
#include "cons.hpp"

namespace cons
{

namespace p2pmsg = fbschema::p2pmsg;

/**
 * Create and save ledger from the given proposal message.
 * @param proposal consensus reached Satge 3 proposal.
 * @return tuple of current lcl sequence number and file name of the saved lcl.
 */
const std::tuple<const uint64_t, std::string> save_ledger(const p2p::proposal &proposal)
{
    const size_t pos = proposal.lcl.find("-");
    uint64_t led_seq_no = 0;

    if (pos != std::string::npos)
    {
        led_seq_no = std::stoull(proposal.lcl.substr(0, pos)); //get lcl sequence number.
        led_seq_no++;                                          //current lcl sequence number.
    }
    else
    {
        //lcl records should follow [ledger sequnce numer]-lcl[lcl hex] format.
        LOG_ERR << "Invalid lcl name: " << proposal.lcl << " when saving ledger.";
    }

    //Serialize lcl using flatbuffer ledger schema.
    flatbuffers::FlatBufferBuilder builder(1024);
    const std::string_view ledger_str = fbschema::ledger::create_ledger_from_proposal(builder, proposal, led_seq_no);

    //Get binary hash of the the serialized lcl.
    const std::string lcl = crypto::get_hash(ledger_str);

    //Get hex from binary hash.
    std::string lcl_hash;
    util::bin2hex(lcl_hash,
                  reinterpret_cast<const unsigned char *>(lcl.data()),
                  lcl.size());

    //construct lcl file name.
    //lcl file name should follow [ledger sequnce numer]-lcl[lcl hex] format.
    const std::string seq_no_str = std::to_string(led_seq_no);
    std::string file_name;
    file_name.reserve(lcl_hash.size() + seq_no_str.size() + 1);
    file_name.append(seq_no_str)
        .append("-")
        .append(lcl_hash);

    write_ledger(file_name, ledger_str.data(), ledger_str.size());

    ledger_cache_entry c;
    c.lcl = file_name;
    c.state = proposal.state.to_string_view();
    cons::ctx.ledger_cache.emplace(led_seq_no, std::move(c));

    //Remove old ledgers that exceeds max sequence range.
    if (led_seq_no > MAX_LEDGER_SEQUENCE)
    {
        remove_old_ledgers(led_seq_no - MAX_LEDGER_SEQUENCE);
    }

    return std::make_tuple(led_seq_no, std::move(file_name));
}

/**
 * Remove old ledgers that exceeds max sequence range from file system and ledger history cache.
 * @param led_seq_no minimum sequence number to be in history.
 */
void remove_old_ledgers(const uint64_t led_seq_no)
{
    std::map<uint64_t, ledger_cache_entry>::iterator itr;

    std::string dir_path;

    dir_path.reserve(conf::ctx.hist_dir.size() + 1);
    dir_path.append(conf::ctx.hist_dir)
        .append("/");

    for (itr = cons::ctx.ledger_cache.begin();
         itr != cons::ctx.ledger_cache.lower_bound(led_seq_no + 1);
         itr++)
    {
        const std::string file_name = itr->second.lcl;
        std::string file_path;
        file_path.reserve(dir_path.size() + itr->second.lcl.size() + 4);
        file_path.append(dir_path)
            .append(file_name)
            .append(".lcl");

        if (boost::filesystem::exists(file_path))
            boost::filesystem::remove(file_path);
    }

    if (!cons::ctx.ledger_cache.empty())
        cons::ctx.ledger_cache.erase(cons::ctx.ledger_cache.begin(), cons::ctx.ledger_cache.lower_bound(led_seq_no + 1));
}

/**
 * Write ledger to file system.
 * @param file_name current ledger sequence number.
 * @param ledger_raw raw lcl data.
 * @param ledger_size size of the raw lcl data.
 */
void write_ledger(const std::string &file_name, const char *ledger_raw, size_t ledger_size)
{
    //create file path to save ledger.
    //file name -> [ledger sequnce numer]-[lcl hex]

    std::string path;

    path.reserve(file_name.size() + conf::ctx.hist_dir.size() + 5);
    path.append(conf::ctx.hist_dir)
        .append("/")
        .append(file_name)
        .append(".lcl");

    //write ledger to file system
    std::ofstream ofs(std::move(path));
    ofs.write(ledger_raw, ledger_size);
    ofs.close();
}

/**
 * Delete ledger from file system.
 * @param file_name name of ledger to be deleted.
 */
void remove_ledger(const std::string &file_name)
{
    std::string file_path;
    file_path.reserve(conf::ctx.hist_dir.size() + file_name.size() + 5);
    file_path.append(conf::ctx.hist_dir)
        .append("/")
        .append(file_name)
        .append(".lcl");
    boost::filesystem::remove(file_path);
}

/**
 * Retrieve lcl(last closed ledger) information from ledger history.
 * @return A ledger_history struct representing the lcl.
 */
const ledger_history load_ledger()
{
    ledger_history ldg_hist;
    //Get all records at lcl history direcory and find the last closed ledger.
    size_t latest_pos = 0;
    for (const auto &entry : boost::filesystem::directory_iterator(conf::ctx.hist_dir))
    {
        const boost::filesystem::path file_path = entry.path();
        const std::string file_name = file_path.stem().string();

        if (boost::filesystem::is_directory(file_path))
        {
            LOG_ERR << "Found directory " << file_name << " in " << conf::ctx.hist_dir << ". There should be no folders in this directory";
        }
        else if (file_path.extension() != ".lcl")
        {
            LOG_ERR << "Found invalid file extension: " << file_path.extension() << " for lcl file " << file_name << " in " << conf::ctx.hist_dir;
        }
        else
        {
            const size_t pos = file_name.find("-");
            uint64_t seq_no = 0;

            if (pos != std::string::npos)
            {
                seq_no = std::stoull(file_name.substr(0, pos));

                std::ifstream file(file_path.string(), std::ios::binary | std::ios::ate);
                std::streamsize size = file.tellg();
                file.seekg(0, std::ios::beg);

                std::vector<char> buffer(size);
                if (file.read(buffer.data(), size))
                {
                    const uint8_t *ledger_buf_ptr = reinterpret_cast<const uint8_t *>(buffer.data());
                    const fbschema::ledger::Ledger *ledger = fbschema::ledger::GetLedger(ledger_buf_ptr);
                    ledger_cache_entry c;
                    c.lcl = file_name;
                    c.state = fbschema::flatbuff_bytes_to_sv(ledger->state());

                    ldg_hist.cache.emplace(seq_no, std::move(c)); //lcl_cache -> [seq_no-hash]
                }
            }
            else
            {
                //lcl records should follow [ledger sequnce numer]-lcl[lcl hex] format.
                LOG_ERR << "Invalid lcl file name: " << file_name << " in " << conf::ctx.hist_dir;
            }
        }
    }

    //check if there is a saved lcl file -> if no send genesis lcl.
    if (ldg_hist.cache.empty())
    {
        ldg_hist.led_seq_no = 0;
        ldg_hist.lcl = GENESIS_LEDGER;
    }
    else
    {
        ldg_hist.led_seq_no = ldg_hist.cache.rbegin()->first;
        ldg_hist.lcl = ldg_hist.cache.rbegin()->second.lcl;

        //Remove old ledgers that exceeds max sequence range.
        if (ldg_hist.led_seq_no > MAX_LEDGER_SEQUENCE)
        {
            remove_old_ledgers(ldg_hist.led_seq_no - MAX_LEDGER_SEQUENCE);
        }
    }

    return ldg_hist;
}

/**
 * Create and send ledger history request to random node from unl list.
 * @param minimum_lcl hash of the minimum lcl from which node need lcl history.
 * @param required_lcl hash of the required lcl.
 */
void send_ledger_history_request(const std::string &minimum_lcl, const std::string &required_lcl)
{
    p2p::history_request hr;
    hr.required_lcl = required_lcl;
    hr.minimum_lcl = minimum_lcl;
    
    flatbuffers::FlatBufferBuilder fbuf(1024);
    p2pmsg::create_msg_from_history_request(fbuf, hr);
    p2p::send_message_to_random_peer(fbuf);

    ctx.last_requested_lcl = required_lcl;

    LOG_DBG << "Ledger history request sent. Required lcl:" << required_lcl.substr(0, 15);
}

/**
 * Check requested lcl is in node's lcl history cache.
 * @param hr lcl history request information.
 * @return true if requested lcl is in lcl history cache.
 */
bool check_required_lcl_availability(const p2p::history_request &hr)
{
    size_t pos = hr.required_lcl.find("-");
    uint64_t req_seq_no = 0;

    //get sequence number of required lcl
    if (pos != std::string::npos)
    {
        req_seq_no = std::stoull(hr.required_lcl.substr(0, pos)); //get required lcl sequence number
    }

    if (req_seq_no > 0)
    {
        const auto itr = cons::ctx.ledger_cache.find(req_seq_no);
        if (itr == cons::ctx.ledger_cache.end())
        {
            LOG_DBG << "Required lcl peer asked for is not in our lcl cache.";
            //either this node is also not in consesnsus ledger or other node requesting a lcl that is older than node's current
            // minimum lcl sequence becuase of maximum ledger history range.
            return false;
        }
        else if (itr->second.lcl != hr.required_lcl)
        {
            LOG_DBG << "Required lcl peer asked for is not in our lcl cache.";
            //either this node or requesting node is in a fork condition.
            return false;
        }
    }
    else
    {
        return false; //Very rare case: node asking for the genisis lcl.
    }
    return true;
}

/**
 * Retrieve lcl(last closed ledger) information from ledger history.
 * @param hr lcl history request information.
 * @return A ledger history response containing requested ledger details.
 */
const p2p::history_response retrieve_ledger_history(const p2p::history_request &hr)
{
    p2p::history_response history_response;
    size_t pos = hr.minimum_lcl.find("-");
    uint64_t min_seq_no = 0;
    std::string min_lcl_hash;

    //get sequence number of minimum lcl required
    if (pos != std::string::npos)
    {
        min_seq_no = std::stoull(hr.minimum_lcl.substr(0, pos)); //get required lcl sequence number
    }

    const auto itr = cons::ctx.ledger_cache.find(min_seq_no);
    if (itr != cons::ctx.ledger_cache.end()) //requested minimum lcl is not in our lcl history cache
    {
        min_seq_no = itr->first;
        //check whether minimum lcl node ask for is same as this node's.
        //eventhough sequence number are same, lcl hash can be changed if one of node is in a fork condition.
        if (hr.minimum_lcl != itr->second.lcl)
        {
            LOG_DBG << "Invalid minimum ledger. Recieved min hash: " << min_lcl_hash << " Node hash: " << itr->second.lcl;
            history_response.error = p2p::LEDGER_RESPONSE_ERROR::INVALID_MIN_LEDGER;
            return history_response;
        }
    }
    else if (min_seq_no > cons::ctx.ledger_cache.rbegin()->first) //Recieved minimum lcl sequence is ahead of node's lcl sequence.
    {
        LOG_DBG << "Invalid minimum ledger. Recieved minimum sequence number is ahead of node current lcl sequence. hash: " << min_lcl_hash;
        history_response.error = p2p::LEDGER_RESPONSE_ERROR::INVALID_MIN_LEDGER;
        return history_response;
    }
    else
    {
        LOG_DBG << "Minimum lcl peer asked for is not in our lcl cache. Therefore sending from node minimum lcl";
        min_seq_no = cons::ctx.ledger_cache.begin()->first;
    }

    //LOG_DBG << "history request min seq: " << std::to_string(min_seq_no);

    //copy current history cache.
    std::map<uint64_t, ledger_cache_entry> led_cache = cons::ctx.ledger_cache;

    //filter out cache and get raw files here.
    led_cache.erase(
        led_cache.begin(),
        led_cache.lower_bound(min_seq_no));

    //Get raw content of lcls that going to be send.
    for (auto &[seq_no, cache] : led_cache)
    {
        p2p::history_ledger ledger;
        ledger.lcl = cache.lcl;
        ledger.state = cache.state;

        std::string path;

        path.reserve(conf::ctx.hist_dir.size() + cache.lcl.size() + 5);
        path.append(conf::ctx.hist_dir)
            .append("/")
            .append(cache.lcl)
            .append(".lcl");

        //read lcl file
        std::ifstream file(path, std::ios::binary | std::ios::ate);
        std::streamsize size = file.tellg();
        file.seekg(0, std::ios::beg);

        std::vector<char> buffer(size);
        if (file.read(buffer.data(), size))
        {
            ledger.raw_ledger = reinterpret_cast<std::vector<uint8_t> &>(buffer);
            history_response.hist_ledgers.emplace(seq_no, ledger);
        }
    }

    return history_response;
}

/**
 * Handle recieved ledger history response.
 * @param hr lcl history request information.
 * @return peer outbound message object with ledger history response.
 */
void handle_ledger_history_response(const p2p::history_response &hr)
{
    //check response object contains
    if (ctx.last_requested_lcl.empty())
    {
        LOG_DBG << "Peer sent us a history response but we never asked for one!";
        return;
    }

    if (hr.error == p2p::LEDGER_RESPONSE_ERROR::INVALID_MIN_LEDGER)
    {
        // This means we are in a fork ledger.Remove/rollback current ledger.
        // Basically in the long run we'll rolback one by one untill we catch up to valid minimum ledger .
        remove_ledger(ctx.lcl);
        cons::ctx.ledger_cache.erase(ctx.ledger_cache.rbegin()->first);
        LOG_DBG << "Invalid min ledger. Removed last ledger.";
    }
    else
    {
        //check whether recieved lcl history contains the current lcl node required.
        bool have_requested_lcl = false;
        for (auto &[seq_no, ledger] : hr.hist_ledgers)
        {
            if (ctx.last_requested_lcl == ledger.lcl)
            {
                have_requested_lcl = true;
                break;
            }
        }

        if (!have_requested_lcl)
        {
            LOG_DBG << "Peer sent us a history response but not containing the lcl we asked for! " << hr.hist_ledgers.size();
            return;
        }

        //Check integrity of recieved lcl list.
        //By checking recieved lcl hashes matches lcl content by applying hashing for each raw content.
        for (auto &[seq_no, ledger] : hr.hist_ledgers)
        {
            const size_t pos = ledger.lcl.find("-");
            std::string rec_lcl_hash = ledger.lcl.substr((pos + 1), (ledger.lcl.size() - 1));

            //Get binary hash of the the serialized lcl.
            const std::string lcl = crypto::get_hash(&ledger.raw_ledger[0], ledger.raw_ledger.size());

            //Get hex from binary hash
            std::string lcl_hash;

            util::bin2hex(lcl_hash,
                          reinterpret_cast<const unsigned char *>(lcl.data()),
                          lcl.size());

            //LOG_DBG << "passed lcl: " << ledger.lcl << " gen lcl: " << lcl_hash;

            //recieved lcl hash and hash generated from recieved lcl content doesn't match -> abandon applying it
            if (lcl_hash != rec_lcl_hash)
            {
                LOG_WARN << "peer sent us a history response we asked for but the ledger data does not match the ledger hashes";
                //todo: we should penalize peer who send this?
                return;
            }
        }
    }

    //Execution to here means the history data sent checks out
    //Save recieved lcl in file system and update lcl history cache
    for (auto &[seq_no, ledger] : hr.hist_ledgers)
    {
        auto prev_dup_itr = cons::ctx.ledger_cache.find(seq_no);
        if (prev_dup_itr != cons::ctx.ledger_cache.end())
        {
            remove_ledger(prev_dup_itr->second.lcl);
            cons::ctx.ledger_cache.erase(prev_dup_itr);
        }
        write_ledger(ledger.lcl, reinterpret_cast<const char *>(&ledger.raw_ledger[0]), ledger.raw_ledger.size());
        ledger_cache_entry l;
        l.lcl = ledger.lcl;
        l.state = ledger.state;
        cons::ctx.ledger_cache.emplace(seq_no, std::move(l));
    }

    ctx.last_requested_lcl = "";

    if (cons::ctx.ledger_cache.empty())
    {
        cons::ctx.led_seq_no = 0;
        cons::ctx.lcl = GENESIS_LEDGER;
    }
    else
    {
        const auto latest_lcl_itr = cons::ctx.ledger_cache.rbegin();
        cons::ctx.lcl = latest_lcl_itr->second.lcl;
        cons::ctx.led_seq_no = latest_lcl_itr->first;
    }

    LOG_INFO << "lcl sync complete. New lcl:" << cons::ctx.lcl.substr(0, 15);
}

} // namespace cons