/*
 * Copyright (c) 2019 Clementine Computing LLC.
 *
 * This file is part of PopuFare.
 *
 * PopuFare is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PopuFare 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with PopuFare.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/un.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <poll.h>
#include <time.h>

#include "../common/common_defs.h"
#include "../commhub/commhub.h"
#include "../commhub/client_utils.h"

#include "billdb.h"


//----------GLOBAL STATE VARIABLES

int flush_in_progress = 0;  //This flag is used to tell if there is a flush in progress

time_t   last_sync_attempt = 0;  //Time of the last connection attempt

int   commhub_fd = -1;  //File descriptor of our connection to the comm hub
int  server_fd = -1;    //File descriptor of our connection to the sync server

bill_status real_bill_status = {0};

time_t  last_watermark_warning = 0;  //The time of our last high watermark warning for the driver when space is low

//This function attempts to connect to the bill server...
int connect_to_bill_server()
{
    int fd;
    int retval;
    struct sockaddr_in addr;

    fd = socket(PF_INET, SOCK_STREAM, 0);

    if(fd < 0)
        return -1;

    addr.sin_family = AF_INET;
    addr.sin_port = htons(BILL_SERVER_PORT);
    inet_aton(BILL_SERVER_IP, &addr.sin_addr);

    retval = connect(fd, (struct sockaddr *)&addr, sizeof(addr));

    if(retval < 0)
    {
        close(fd);
        return -2;
    }

  return fd;
}

int handle_watermark_warnings(billdb_context *ctx, int force)
{
    time_t now = time(NULL);
    struct message_record error_message;

    if(!ctx)
        return -1;

    if(ctx->num_free_records < BILLING_CRITICAL_THRESHOLD)  //if we have a critical high watermark condition
    {
        //and we are either allowed to force a message or it is time to deliver the next one
        if(force || ((now - last_watermark_warning) >= BILLING_CRITICAL_FREQUENCY))
        {
            if(commhub_fd >= 0)
            {
                format_log_message(&error_message, LOGLEVEL_ERROR, "LOG CRITICAL: Call Dispatch");
                send_message(commhub_fd, &error_message);
                format_driver_message(&error_message, LOGLEVEL_ERROR, "LOG CRITICAL: Call Dispatch");
                send_message(commhub_fd, &error_message);
                last_watermark_warning = now;
            }
            else
            {
                return -1;
            }
        }
    }
    else if(ctx->num_free_records < BILLING_HIGH_THRESHOLD)  //if we have a high watermark condition
    {
        //and we are either allowed to force a message or it is time to deliver the next one
        if(force || ((now - last_watermark_warning) >= BILLING_HIGH_FREQUENCY))
        {
            if(commhub_fd >= 0)
            {
                format_log_message(&error_message, LOGLEVEL_ERROR, "LOG HALF FULL: Call Dispatch");
                send_message(commhub_fd, &error_message);
                format_driver_message(&error_message, LOGLEVEL_ERROR, "LOG HALF FULL: Call Dispatch");
                send_message(commhub_fd, &error_message);
                last_watermark_warning = now;
            }
            else
            {
                return -1;
            }
        }
    }

    return 0;
}

int send_next_log(int fd, billdb_context *ctx, int next_idx)
{
    char buffer[BILLING_LINE_SIZE + 2] = {0};
    int n, i, ret;

    if(!ctx)
        return 0;

    if(!ctx->bills)
        return 0;

    if(next_idx < 0)
        return 0;

    //Grab the billing log lone
    strncpy(buffer, ctx->bills[next_idx].data, BILLING_LINE_SIZE);
    n = strlen(buffer);

    //if it's zero length, that means that we've struck it from the record
    //already (it was ack'd on this same run through the poll loop).
    if(n == 0)
    {
        return 0;
    }

    //Add a newline
    buffer[n++] = '\n';
    buffer[n] = '\0';

    i = 0;

    //send it!
    while(i < n)
    {
        ret = send(fd, buffer + i, n - i, 0);

        if( ret <= 0 )
            return -1;

        i += ret;
    }

    //And mark it as sent now, so that we will only revisit it once the timer has run out...
    ctx->last_tx[next_idx] = time(NULL);

    return 1;
}

int handle_bill_reply(char *line, billdb_context *ctx)
{

    char buffer[LINE_BUFFER_SIZE];

    int input_idx = 0;
    int eol = 0;
    int retval;

    //Extract the first tab-delimited field from the input line...
    input_idx += get_field(buffer, line + input_idx, sizeof(buffer), &eol);

    //If that field is blank, then we ignore this line
    if( buffer[0] == '\0' )
    {
        return 0;
    }

    if( !strcasecmp(buffer, "ACK") )
    {
        if( eol )
        {
//            printf("ACK: Premature end of line!\n");
            return -1;
        }

        //Get the next field (this should be a checksum...)
        input_idx += get_field(buffer, line + input_idx, sizeof(buffer), &eol);

        real_bill_status.last_ack_time = time(NULL);  //update ack time

        retval = clear_billing_entry(ctx, buffer);  //clear the billing entry

        real_bill_status.unsynced_messages = NUM_BILLING_ENTRIES - ctx->num_free_records;  //update buffer count

        return retval;
    }
    else if( !strcasecmp(buffer, "DUP") )
    {
        if( eol )
        {
//            printf("DUP: Premature end of line!\n");
            return -1;
        }

        //Get the next field (this should be a checksum...)
        input_idx += get_field(buffer, line + input_idx, sizeof(buffer), &eol);

        real_bill_status.last_ack_time = time(NULL);  //update ack time

        retval = clear_billing_entry(ctx, buffer);  //clear the billing entry

        real_bill_status.unsynced_messages = NUM_BILLING_ENTRIES - ctx->num_free_records;  //update buffer count

        return retval;
    }
    else if( !strcasecmp(buffer, "IGN") )
    {
        if( eol )
        {
//            printf("IGN: Premature end of line!\n");
            return -1;
        }

        //Get the next field (this should be a checksum...)
        input_idx += get_field(buffer, line + input_idx, sizeof(buffer), &eol);

        real_bill_status.last_ack_time = time(NULL);  //update ack time

        retval = clear_billing_entry(ctx, buffer);  //clear the billing entry

        real_bill_status.unsynced_messages = NUM_BILLING_ENTRIES - ctx->num_free_records;  //update buffer count

        return retval;
    }
    else
    {
        fprintf(stderr, "Unknown command \"%s\"\n", buffer);
    }

    return 0;
}

void maintain_ipc_hub_connect(char *progname)
{
    struct message_record outgoing_msg;

    if(commhub_fd < 0)  //if we have no connection to the communication hub
    {
        commhub_fd = connect_to_message_server(progname);  //try and get one

//        printf("commhub_fd = %d\n", commhub_fd);

        if(commhub_fd >= 0)  //if it worked
        {
            //Subscribe to the basics
            subscribe_to_default_messages(commhub_fd);

            //Subscribe to the command mailboxes we act on
            prepare_message(&outgoing_msg, MAILBOX_SUBSCRIBE, MAILBOX_BILLING_LOG, strlen(MAILBOX_BILLING_LOG));
            send_message(commhub_fd,&outgoing_msg);

            prepare_message(&outgoing_msg, MAILBOX_SUBSCRIBE, MAILBOX_PADDLE_ACK, strlen(MAILBOX_PADDLE_ACK));
            send_message(commhub_fd,&outgoing_msg);

            //Request updated status information...
            prepare_message(&outgoing_msg, MAILBOX_STATUS_REQUEST, "", 0);
            send_message(commhub_fd,&outgoing_msg);
        }
    }

}

int send_bill_update(int force)
{
    struct message_record outgoing_msg;

    //if EITHER the force flag is set, OR our record differs from the last one on file from the IPC hub...
    if( force || memcmp(&bill_stat, &real_bill_status, sizeof(real_bill_status)) )
    {
        if(commhub_fd >= 0)
        {
            //prepare and send it
            prepare_message(&outgoing_msg, MAILBOX_BILL_STATUS, &real_bill_status, sizeof(real_bill_status));
            send_message(commhub_fd,&outgoing_msg);
        }

        return 1;
    }

    return 0;
}

message_callback_return handle_billing_log_message(struct message_record *msg, void *param)
{
    billdb_context *ctx = (billdb_context *)param;
    int retval = 0;
    int ignore = 0;


    //     If this is a diagnostic log message, the first character will be a priority
    // code, otherwise for a billing log message it will be numeric.
    char priority = ((char *)msg->payload)[0];  

    switch(priority)
    {
        case LOGLEVEL_DEBUG:  //if this is a diagnostic message with a priority of LOGLEVEL_DEBUG
                                //and there are fewer than REJECT_DIAG_DEBUG_THRESHOLD free buffer slots

            if(ctx->num_free_records < REJECT_DIAG_DEBUG_THRESHOLD)
            {
                ignore = 1;  //then for safety, ignore this message
            }
            else
            {
                ignore = 0;  //otherwise, if we have plenty of space, store it
            }
            break;

        case LOGLEVEL_WARN:  //if this is a diagnostic message with a priority of LOGLEVEL_WARN
                                //and there are fewer than REJECT_DIAG_WARN_THRESHOLD free buffer slots

            if(ctx->num_free_records < REJECT_DIAG_WARN_THRESHOLD)
            {
                ignore = 1;  //then for safety, ignore this message
            }
            else
            {
                ignore = 0;  //otherwise, if we have plenty of space, store it
            }
            break;

        case LOGLEVEL_ERROR:  //if this is a diagnostic message with a priority of LOGLEVEL_ERROR
                                //and there are fewer than REJECT_DIAG_ERROR_THRESHOLD free buffer slots

            if(ctx->num_free_records < REJECT_DIAG_ERROR_THRESHOLD)
            {
                ignore = 1;  //then for safety, ignore this message
            }
            else
            {
                ignore = 0;  //otherwise, if we have plenty of space, store it
            }
            break;

        default:    //If this message does not start with a known diagnostic priority code, it is a billing message
            ignore = 0;    //and therefore can never be ignored.
            break;
    }


    if(ignore)  //If we've decided to ignore the message
    {
        //     This means we are ignoring a message.  This should only happen when buffer space
        // is scarce and the message is a diagnostic log message whith a priority that does not
        // justify potentially missing a billing entry later.
    }
    else  //Otherwise, we want to process it as normal.
    {
        retval = add_billing_entry(ctx, (char *)msg->payload);  //Attempt to add the message to the billing log

        switch(retval)            //Test to see if that worked
        {
            case FAIL_FULL:          //if the add failed
            case FAIL_MEM:
                if(commhub_fd >= 0)        //and we can talk to the commhub
                {
                    struct message_record error_message;

                    format_driver_message(&error_message, LOGLEVEL_ERROR, "LOG FULL: Call Dispatch");  //notify the driver
                    send_message(commhub_fd, &error_message);
                }
                break;

            default:            //Otherwise, if the add succeded
                real_bill_status.unsynced_messages = NUM_BILLING_ENTRIES - ctx->num_free_records;       //update buffer count
                break;
        }

        send_bill_update(0);          //In either case, sent a status update if needed.
    }

    return MESSAGE_HANDLED_CONT;
}

message_callback_return handle_status_request_message(struct message_record *msg, void *param)
{
    billdb_context *ctx = (billdb_context *)param;

    real_bill_status.unsynced_messages = NUM_BILLING_ENTRIES - ctx->num_free_records;       //update buffer count

    //force a billing log status update if one is requested by a newly subscribing module
    send_bill_update(1);
    return MESSAGE_HANDLED_CONT;
}

int paddle_ack_flag = 0;  //a variable to track if a paddle selection success has occurred (a driver has logged in)

//this callback catches paddle selection acknowledge messages on the MAILBOX_PADDLE_ACK mailing list and
//test to see if they report success, if so it sets the above flag so that we have the opportunity to warn a
//newly logged in driver about a high-water-mark condition.
message_callback_return handle_paddle_ack(struct message_record *msg, void *param)
{
    set_paddle_req *payload = (set_paddle_req *)msg->payload;

    if(payload)
    {
        paddle_ack_flag = (payload->request == payload->result);
    }

    return MESSAGE_HANDLED_CONT;
}

int main(int argc, char **argv)
{
    struct pollfd fds[2];
    int nfds = 0;
    int poll_return = 0;
    int read_return = 0;

    int next_sync_idx = -1;

    int i;

    struct message_record incoming_msg;
    struct message_record outgoing_msg;

    char input_line[LINE_BUFFER_SIZE] = {0};
    int input_idx = 0;
    int checked_idx = 0;

    billdb_context ctx = {0};


    //------------------

    configure_signal_handlers(argv[0]);
    maintain_ipc_hub_connect(argv[0]);
    register_system_status_callbacks();

    //register our module-specific callback
    register_dispatch_callback(MAILBOX_BILLING_LOG, CALLBACK_USER(1), handle_billing_log_message, &ctx);
    register_dispatch_callback(MAILBOX_STATUS_REQUEST, CALLBACK_USER(2), handle_status_request_message, &ctx);
    register_dispatch_callback(MAILBOX_PADDLE_ACK, CALLBACK_USER(3), handle_paddle_ack, NULL);

    read_return = attach_to_billdb(&ctx);

    if( read_return < 0 )
    {
        fprintf(stdout, "Database is missing or corrupt.  Attempting to format new database.\n");
        read_return = format_new_billdb();

        if( read_return < 0 )
        {
            fprintf(stderr, "Database cannot be created.  Aborting!\n");
            return -1;
        }
        else
        {
            read_return = attach_to_billdb(&ctx);

            if( read_return < 0 )
            {
                fprintf(stderr, "New database is ALSO missing or corrupt.  Aborting.\n");
                return -1;
            }
        }
    }

    while( exit_request_status == EXIT_REQUEST_NONE )
    {
        time_t now = time(NULL);

        RESET_WATCHDOG();

        //DEBUG
        printf("[%lli] billdb: heartbeat\n", get_usec_time());
        //DEBUG

        maintain_ipc_hub_connect(argv[0]);

        if(server_fd < 0)  //If we don't have a connection to the sync server...
        {
            if( (now - last_sync_attempt) > DEFAULT_CONNECT_RETRY )  //See if it is time to try again
            {
                if( tunnel_is_up() )          //and if the tunnel thinks it is up
                {
                     server_fd = connect_to_bill_server();    //if so, try again...

//                     printf("server_fd = %d\n", server_fd);

                     if(server_fd >= 0)  //if it worked
                     {
                         input_idx = 0;  //reset our buffer index
                         last_sync_attempt = 0;
                     }
                     else
                     {
                         last_sync_attempt = now;
                     }
                }
            }
        }

        //Every time through the loop check and see if we need to warn the driver of a high water mark condition
        //in the billing log (running out of space, and our warning frequency timer is up).  If a driver has just
        //freshly logged in, we send a warning and reset our frequency timers.
        handle_watermark_warnings(&ctx, paddle_ack_flag);
        paddle_ack_flag = 0;

        nfds=0;

        //If we have a connection to the billing server
        if(server_fd >= 0)
        {
            //tell poll that we care about it
            fds[nfds].fd = server_fd;
            fds[nfds].events = POLLIN;

            //See if the database thinks we have anything that we need to try and sync right now...
            next_sync_idx = next_pending_entry(&ctx);

            if(next_sync_idx >= 0)  //If so, ask poll() to unblock us when there is room in the pipe to the server.
            {
                fds[nfds].events |= POLLOUT;
            }

            //and advance the counter of active file descriptors
            nfds++;
        }

        if(commhub_fd >= 0)
        {
            fds[nfds].fd = commhub_fd;
            fds[nfds].events = POLLIN;

            nfds++;
        }

        if(nfds > 0)
        {
            poll_return = poll(fds, nfds, POLL_TIMEOUT);
        }
        else
        {
            usleep(POLL_TIMEOUT * 1000);
            poll_return = 0;
        }

        if(poll_return <= 0)
        {
            continue;
        }

        //DEBUG
        printf("## cp.nfd %i\n", (int)nfds);

        for(i=0; i < nfds; i++)
        {
            if( fds[i].fd == server_fd )
            {

                if(fds[i].revents & POLLIN)
                {

                    read_return = recv(fds[i].fd, input_line + input_idx, sizeof(input_line) - input_idx, 0);

                    //If the socket has closed politely (0), or had an error other than EINTR...
                    if( (read_return == 0) || ((read_return < 0) && (errno != EINTR)) )
                    {

                      //DEBUG
                      printf("## bang\n");

                        close(server_fd);
                        server_fd = -1;

            usleep(POLL_TIMEOUT * 1000);

                        break;
                    }
                    else
                    {
                        //this test is required otherwise an EINTR case would be treated as -1 bytes read, and bad stuff would happen...
                        if(read_return > 0)
                        {
                            input_idx += read_return;

                            do
                            {
                                //Advance until we either hit the end of the buffer, or we hit a line-terminator
                                while(checked_idx < input_idx)
                                {
                                    if( (input_line[checked_idx] == '\r') || (input_line[checked_idx] == '\n') )
                                    {
                                        break;
                                    }
                                    else
                                    {
                                        checked_idx++;
                                    }
                                }

                                //If we didn't hit the end of the input...
                                if(checked_idx != input_idx)
                                {
                                    int j,k;

                                    //Null terminate the line we got as a string...
                                    input_line[checked_idx] = '\0';

                                    //Do something useful with the string input_buffer...

                                    if( handle_bill_reply(input_line, &ctx) < 0 )
                                    {
//                                        printf("Command Failed: \"%s\"\n", input_line);
                                    }
                                    else
                                    {
                                        //If the server has ack'd a billing entry, that means that we may need up update the pass
                                        //associated with that billing entry...
                                        prepare_message(&outgoing_msg, MAILBOX_UPDATE_PASSES, "", 0);
                                        send_message(commhub_fd, &outgoing_msg);

                                        //Update our pass time status...
                                        send_bill_update(0);
                                    }

                                    //Now that we've done that, we can bump the rest of characters to the beginning of the next line...
                                    k = input_idx - (checked_idx + 1);

                                    for(j=0; j < k; j++)
                                    {
                                        input_line[j] = input_line[j + checked_idx + 1];
                                    }

                                    input_idx = j;
                                    checked_idx = 0;
                                }

                                //If we have hit an overflow condition such that our buffer is full and no newline has been received
                                if(input_idx == sizeof(input_line))
                                {
                                    close(server_fd);
                                    server_fd = -1;
                                    break;
                                }

                            } while(checked_idx < input_idx);
                        }
                    }
                }
                else if(fds[i].revents & (POLLERR | POLLHUP | POLLNVAL)) //If we've lost connection, break this loop and poll all over again
                {
                    close(server_fd);
                    server_fd = -1;
                    break;
                }


                if(fds[i].revents & POLLOUT)
                {
                    //send more logs here
                    send_next_log(server_fd, &ctx, next_sync_idx);
                    real_bill_status.last_sync_time = time(NULL);
                    send_bill_update(0);
                }

            }
            else if( fds[i].fd == commhub_fd )
            {  
                //If we've lost connection, break this loop and poll all over again
                if(fds[i].revents & (POLLERR | POLLHUP | POLLNVAL))  
                {
                    close(commhub_fd);
                    commhub_fd = -1;
                    break;
                }

                if(fds[i].revents & POLLIN)
                {
//                    printf("Trying to read from hub...\n");
                    read_return = get_message(commhub_fd, &incoming_msg);

                    if( read_return < 0 )
                    {
                        close(commhub_fd);
                        commhub_fd = -1;
                        break;
                    }

                    process_message(&incoming_msg);

                }

            }
        }
    }

    printf("Detatching from Bill Database\n");
    detach_from_billdb(&ctx);

    printf("Closing connections\n");
    if(server_fd >= 0)
    {
        close(server_fd);
        server_fd = -1;
    }

    if(commhub_fd >= 0)
    {
        close(commhub_fd);
        server_fd = -1;
    }

    printf("Goodbye.\n");


    return 0;
}