%%   The contents of this file are subject to the Mozilla Public License
%%   Version 1.1 (the "License"); you may not use this file except in
%%   compliance with the License. You may obtain a copy of the License at
%%   http://www.mozilla.org/MPL/
%%
%%   Software distributed under the License is distributed on an "AS IS"
%%   basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
%%   License for the specific language governing rights and limitations
%%   under the License.
%%
%%   The Original Code is RabbitMQ Management Plugin.
%%
%%   The Initial Developer of the Original Code is GoPivotal, Inc.
%%   Copyright (c) 2010-2012 GoPivotal, Inc.  All rights reserved.
%%

-module(rabbit_mgmt_stats).

-include_lib("rabbitmq_management_agent/include/rabbit_mgmt_records.hrl").
-include_lib("rabbitmq_management_agent/include/rabbit_mgmt_metrics.hrl").

-export([format_range/6]).

-define(MICRO_TO_MILLI, 1000).

-type maybe_range() :: no_range | #range{}.
-type maybe_slide() :: exometer_slide:slide() | not_found.
-type maybe_slide_fun() :: fun(() -> [maybe_slide()]).

-export_type([maybe_range/0, maybe_slide/0, maybe_slide_fun/0]).


%%----------------------------------------------------------------------------
%% Query-time
%%----------------------------------------------------------------------------

-spec format_range(maybe_range(), exometer_slide:timestamp(), atom(),
                   non_neg_integer(), maybe_slide_fun(), maybe_slide_fun()) ->
    proplists:proplist().
format_range(no_range, Now, Table, Interval, InstantRateFun, _SamplesFun) ->
    format_no_range(Table, Now, Interval, InstantRateFun);
format_range(#range{last = Last, first = First, incr = Incr}, _Now, Table,
             Interval, _InstantRateFun, SamplesFun) ->
    case SamplesFun() of
        [] ->
            [];
        Slides ->
            Empty = empty(Table, 0),
            Slide = exometer_slide:sum(Last, First, Incr, Slides, Empty),
            List = exometer_slide:to_list(Last, First, Slide),
            Length = length(List),
            RangePoint = Last - Interval,
            LastTwo = get_last_two(List, Length),
            {Total, Rate} = calculate_rate(LastTwo, Table, RangePoint),
            {Samples, SampleTotals} = format_samples(List, empty(Table, []),
                                                     Empty),
            format_rate(Table, Total, Rate, Samples, SampleTotals, Length)
    end.

-spec format_no_range(atom(), exometer_slide:timestamp(), non_neg_integer(),
                      maybe_slide_fun()) -> proplists:proplist().
format_no_range(Table, Now, Interval, InstantRateFun) ->
    RangePoint = ((Now div Interval) * Interval) - Interval,
    case calculate_instant_rate(InstantRateFun, Table, RangePoint) of
        {Total, Rate} ->
            format_rate(Table, Total, Rate);
        not_found ->
            []
    end.

-spec calculate_instant_rate(maybe_slide_fun(), atom(), integer()) ->
    not_found | {integer(), number()}.
calculate_instant_rate(Fun, Table, RangePoint) ->
    case Fun() of
        [] ->
            not_found;
        Slides ->
            Slide = exometer_slide:sum(Slides),
            case exometer_slide:last_two(Slide) of
              [] -> {empty(Table, 0), empty(Table, 0.0)};
              [Last | T] ->
                  Total = get_total(Slide, Table),
                  Rate = rate_from_last_increment(Table, Last, T, RangePoint),
                  {Total, Rate}
              end
      end.

calculate_rate([], Table, _RangePoint) ->
    {empty(Table, 0), empty(Table, 0.0)};
calculate_rate([{_, Total} = Last | T], Table, RangePoint) ->
    Rate = rate_from_last_increment(Table, Last, T, RangePoint),
    {Total, Rate}.

get_last_two(List, Length) when Length =< 2 ->
    lists:reverse(List);
get_last_two(List, Length) ->
    lists:reverse(lists:nthtail(Length - 2, List)).

get_total(Slide, Table) ->
    case exometer_slide:last(Slide) of
        undefined -> empty(Table, 0);
        Other -> Other
    end.

format_samples(Samples, ESamples, ETotal) ->
    lists:foldl(fun({TS, Sample}, {SamplesAcc, TotalsAcc}) ->
            append_full_sample(TS, Sample, SamplesAcc, TotalsAcc)
        end, {ESamples, ETotal}, Samples).

%% connection_stats_coarse_conn_stats, channel_stats_fine_stats,
%% vhost_stats_fine_stats, channel_exchange_stats_fine_stats,
%% queue_msg_stats, vhost_msg_stats
append_full_sample(TS, {V1, V2, V3}, {S1, S2, S3}, {T1, T2, T3}) ->
    {{append_sample(V1, TS, S1), append_sample(V2, TS, S2), append_sample(V3, TS, S3)},
     {V1 + T1, V2 + T2, V3 + T3}};
%% channel_queue_stats_deliver_stats, queue_stats_deliver_stats,
%% vhost_stats_deliver_stats, channel_stats_deliver_stats
append_full_sample(TS, {V1, V2, V3, V4, V5, V6, V7},
           {S1, S2, S3, S4, S5, S6, S7},
           {T1, T2, T3, T4, T5, T6, T7}) ->
    {{append_sample(V1, TS, S1), append_sample(V2, TS, S2),
      append_sample(V3, TS, S3), append_sample(V4, TS, S4),
      append_sample(V5, TS, S5), append_sample(V6, TS, S6),
      append_sample(V7, TS, S7)},
     {V1 + T1, V2 + T2, V3 + T3, V4 + T4, V5 + T5, V6 + T6, V7 + T7}};
%% channel_process_stats, queue_stats_publish, queue_exchange_stats_publish,
%% exchange_stats_publish_out, exchange_stats_publish_in, queue_process_stats
append_full_sample(TS, {V1}, {S1}, {T1}) ->
    {{append_sample(V1, TS, S1)}, {V1 + T1}};
%% node_coarse_stats
append_full_sample(TS, {V1, V2, V3, V4, V5, V6, V7, V8},
           {S1, S2, S3, S4, S5, S6, S7, S8},
           {T1, T2, T3, T4, T5, T6, T7, T8}) ->
    {{append_sample(V1, TS, S1), append_sample(V2, TS, S2),
      append_sample(V3, TS, S3), append_sample(V4, TS, S4),
      append_sample(V5, TS, S5), append_sample(V6, TS, S6),
      append_sample(V7, TS, S7), append_sample(V8, TS, S8)},
     {V1 + T1, V2 + T2, V3 + T3, V4 + T4, V5 + T5, V6 + T6, V7 + T7, V8 + T8}};
%% node_persister_stats
append_full_sample(TS,
           {V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12, V13, V14,
            V15, V16, V17, V18, V19, V20},
           {S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14,
            S15, S16, S17, S18, S19, S20},
           {T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14,
            T15, T16, T17, T18, T19, T20}
          ) ->
    {{append_sample(V1, TS, S1), append_sample(V2, TS, S2),
      append_sample(V3, TS, S3), append_sample(V4, TS, S4),
      append_sample(V5, TS, S5), append_sample(V6, TS, S6),
      append_sample(V7, TS, S7), append_sample(V8, TS, S8),
      append_sample(V9, TS, S9), append_sample(V10, TS, S10),
      append_sample(V11, TS, S11), append_sample(V12, TS, S12),
      append_sample(V13, TS, S13), append_sample(V14, TS, S14),
      append_sample(V15, TS, S15), append_sample(V16, TS, S16),
      append_sample(V17, TS, S17), append_sample(V18, TS, S18),
      append_sample(V19, TS, S19), append_sample(V20, TS, S20)},
     {V1 + T1, V2 + T2, V3 + T3, V4 + T4, V5 + T5, V6 + T6, V7 + T7, V8 + T8,
      V9 + T9, V10 + T10, V11 + T11, V12 + T12, V13 + T13, V14 + T14, V15 + T15,
      V16 + T16, V17 + T17, V18 + T18, V19 + T19, V20 + T20}};
%% node_node_coarse_stats, vhost_stats_coarse_connection_stats, queue_msg_rates,
%% vhost_msg_rates
append_full_sample(TS, {V1, V2}, {S1, S2}, {T1, T2}) ->
    {{append_sample(V1, TS, S1), append_sample(V2, TS, S2)}, {V1 + T1, V2 + T2}}.


format_rate(connection_stats_coarse_conn_stats, {TR, TS, TRe}, {RR, RS, RRe}) ->
    [
     {send_oct, TS},
     {send_oct_details, [{rate, RS}]},
     {recv_oct, TR},
     {recv_oct_details, [{rate, RR}]},
     {reductions, TRe},
     {reductions_details, [{rate, RRe}]}
    ];
format_rate(vhost_stats_coarse_conn_stats, {TR, TS}, {RR, RS}) ->
    [
     {send_oct, TS},
     {send_oct_details, [{rate, RS}]},
     {recv_oct, TR},
     {recv_oct_details, [{rate, RR}]}
    ];
format_rate(Type, {TR, TW}, {RR, RW}) when Type =:= vhost_msg_rates;
                       Type =:= queue_msg_rates ->
    [
     {disk_reads, TR},
     {disk_reads_details, [{rate, RR}]},
     {disk_writes, TW},
     {disk_writes_details, [{rate, RW}]}
    ];
format_rate(Type, {TP, TC, TRe}, {RP, RC, RRe})
  when Type =:= channel_stats_fine_stats;
       Type =:= vhost_stats_fine_stats;
       Type =:= channel_exchange_stats_fine_stats ->
    [
     {publish, TP},
     {publish_details, [{rate, RP}]},
     {confirm, TC},
     {confirm_details, [{rate, RC}]},
     {return_unroutable, TRe},
     {return_unroutable_details, [{rate, RRe}]}
    ];
format_rate(Type, {TG, TGN, TD, TDN, TR, TA, TDG},
        {RG, RGN, RD, RDN, RR, RA, RDG})
  when Type =:= channel_queue_stats_deliver_stats;
       Type =:= channel_stats_deliver_stats;
       Type =:= vhost_stats_deliver_stats;
       Type =:= queue_stats_deliver_stats ->
    [
     {get, TG},
     {get_details, [{rate, RG}]},
     {get_no_ack, TGN},
     {get_no_ack_details, [{rate, RGN}]},
     {deliver, TD},
     {deliver_details, [{rate, RD}]},
     {deliver_no_ack, TDN},
     {deliver_no_ack_details, [{rate, RDN}]},
     {redeliver, TR},
     {redeliver_details, [{rate, RR}]},
     {ack, TA},
     {ack_details, [{rate, RA}]},
     {deliver_get, TDG},
     {deliver_get_details, [{rate, RDG}]}
    ];
format_rate(Type, {TR}, {RR}) when Type =:= channel_process_stats;
                   Type =:= queue_process_stats ->
    [
     {reductions, TR},
     {reductions_details, [{rate, RR}]}
    ];
format_rate(exchange_stats_publish_out, {TP}, {RP}) ->
    [
     {publish_out, TP},
     {publish_out_details, [{rate, RP}]}
    ];
format_rate(exchange_stats_publish_in, {TP}, {RP}) ->
    [
     {publish_in, TP},
     {publish_in_details, [{rate, RP}]}
    ];
format_rate(Type, {TP}, {RP}) when Type =:= queue_stats_publish;
                   Type =:= queue_exchange_stats_publish ->
    [
     {publish, TP},
     {publish_details, [{rate, RP}]}
    ];
format_rate(Type, {TR, TU, TM}, {RR, RU, RM}) when Type =:= queue_msg_stats;
                           Type =:= vhost_msg_stats ->
    [
     {messages_ready, TR},
     {messages_ready_details, [{rate, RR}]},
     {messages_unacknowledged, TU},
     {messages_unacknowledged_details, [{rate, RU}]},
     {messages, TM},
     {messages_details, [{rate, RM}]}
    ];
format_rate(node_coarse_stats, {TF, TS, TM, TD, TP, TGC, TGCW, TCS},
            {RF, RS, RM, RD, RP, RGC, RGCW, RCS}) ->
    [
     {mem_used, TM},
     {mem_used_details, [{rate, RM}]},
     {fd_used, TF},
     {fd_used_details, [{rate, RF}]},
     {sockets_used, TS},
     {sockets_used_details, [{rate, RS}]},
     {proc_used, TP},
     {proc_used_details, [{rate, RP}]},
     {disk_free, TD},
     {disk_free_details, [{rate, RD}]},
     {gc_num, TGC},
     {gc_num_details, [{rate, RGC}]},
     {gc_bytes_reclaimed, TGCW},
     {gc_bytes_reclaimed_details, [{rate, RGCW}]},
     {context_switches, TCS},
     {context_switches_details, [{rate, RCS}]}
    ];
format_rate(node_persister_stats,
            {TIR, TIB, TIA, TIWC, TIWB, TIWAT, TIS, TISAT, TISC,
             TISEAT, TIRC, TMRTC, TMDTC, TMSRC, TMSWC, TQIJWC, TQIWC, TQIRC,
             TIO, TIOAT},
            {RIR, RIB, RIA, RIWC, RIWB, RIWAT, RIS, RISAT, RISC,
             RISEAT, RIRC, RMRTC, RMDTC, RMSRC, RMSWC, RQIJWC, RQIWC, RQIRC,
             RIO, RIOAT}) ->
    %% Calculates average times for read/write/sync/seek from the
    %% accumulated time and count
    %% io_<op>_avg_time is the average operation time for the life of the node
    %% io_<op>_avg_time_details/rate is the average operation time during the
    %% last time unit calculated (thus similar to an instant rate)
    [
     {io_read_count, TIR},
     {io_read_count_details, [{rate, RIR}]},
     {io_read_bytes, TIB},
     {io_read_bytes_details, [{rate, RIB}]},
     {io_read_avg_time, avg_time(TIA, TIR)},
     {io_read_avg_time_details, [{rate, avg_time(RIA, RIR)}]},
     {io_write_count, TIWC},
     {io_write_count_details, [{rate, RIWC}]},
     {io_write_bytes, TIWB},
     {io_write_bytes_details, [{rate, RIWB}]},
     {io_write_avg_time, avg_time(TIWAT, TIWC)},
     {io_write_avg_time_details, [{rate, avg_time(RIWAT, RIWC)}]},
     {io_sync_count, TIS},
     {io_sync_count_details, [{rate, RIS}]},
     {io_sync_avg_time, avg_time(TISAT, TIS)},
     {io_sync_avg_time_details, [{rate, avg_time(RISAT, RIS)}]},
     {io_seek_count, TISC},
     {io_seek_count_details, [{rate, RISC}]},
     {io_seek_avg_time, avg_time(TISEAT, TISC)},
     {io_seek_avg_time_details, [{rate, avg_time(RISEAT, RISC)}]},
     {io_reopen_count, TIRC},
     {io_reopen_count_details, [{rate, RIRC}]},
     {mnesia_ram_tx_count, TMRTC},
     {mnesia_ram_tx_count_details, [{rate, RMRTC}]},
     {mnesia_disk_tx_count, TMDTC},
     {mnesia_disk_tx_count_details, [{rate, RMDTC}]},
     {msg_store_read_count, TMSRC},
     {msg_store_read_count_details, [{rate, RMSRC}]},
     {msg_store_write_count, TMSWC},
     {msg_store_write_count_details, [{rate, RMSWC}]},
     {queue_index_journal_write_count, TQIJWC},
     {queue_index_journal_write_count_details, [{rate, RQIJWC}]},
     {queue_index_write_count, TQIWC},
     {queue_index_write_count_details, [{rate, RQIWC}]},
     {queue_index_read_count, TQIRC},
     {queue_index_read_count_details, [{rate, RQIRC}]},
     {io_file_handle_open_attempt_count, TIO},
     {io_file_handle_open_attempt_count_details, [{rate, RIO}]},
     {io_file_handle_open_attempt_avg_time, avg_time(TIOAT, TIO)},
     {io_file_handle_open_attempt_avg_time_details, [{rate, avg_time(RIOAT, RIO)}]}
    ];
format_rate(node_node_coarse_stats, {TS, TR}, {RS, RR}) ->
    [
     {send_bytes, TS},
     {send_bytes_details, [{rate, RS}]},
     {recv_bytes, TR},
     {recv_bytes_details, [{rate, RR}]}
    ].

format_rate(connection_stats_coarse_conn_stats, {TR, TS, TRe}, {RR, RS, RRe},
        {SR, SS, SRe}, {STR, STS, STRe}, Length) ->
    [
     {send_oct, TS},
     {send_oct_details, [{rate, RS},
             {samples, SS}] ++ average(SS, STS, Length)},
     {recv_oct, TR},
     {recv_oct_details, [{rate, RR},
             {samples, SR}] ++ average(SR, STR, Length)},
     {reductions, TRe},
     {reductions_details, [{rate, RRe},
               {samples, SRe}] ++ average(SRe, STRe, Length)}
    ];
format_rate(vhost_stats_coarse_conn_stats, {TR, TS}, {RR, RS}, {SR, SS},
        {STR, STS}, Length) ->
    [
     {send_oct, TS},
     {send_oct_details, [{rate, RS},
             {samples, SS}] ++ average(SS, STS, Length)},
     {recv_oct, TR},
     {recv_oct_details, [{rate, RR},
             {samples, SR}] ++ average(SR, STR, Length)}
    ];
format_rate(Type, {TR, TW}, {RR, RW}, {SR, SW}, {STR, STW}, Length)
  when Type =:= vhost_msg_rates;
       Type =:= queue_msg_rates ->
    [
     {disk_reads, TR},
     {disk_reads_details, [{rate, RR},
               {samples, SR}] ++ average(SR, STR, Length)},
     {disk_writes, TW},
     {disk_writes_details, [{rate, RW},
                {samples, SW}] ++ average(SW, STW, Length)}
    ];
format_rate(Type, {TP, TC, TRe}, {RP, RC, RRe},
        {SP, SC, SRe}, {STP, STC, STRe}, Length)
  when Type =:= channel_stats_fine_stats;
       Type =:= vhost_stats_fine_stats;
       Type =:= channel_exchange_stats_fine_stats ->
    [
     {publish, TP},
     {publish_details, [{rate, RP},
            {samples, SP}] ++ average(SP, STP, Length)},
     {confirm, TC},
     {confirm_details, [{rate, RC},
            {samples, SC}] ++ average(SC, STC, Length)},
     {return_unroutable, TRe},
     {return_unroutable_details, [{rate, RRe},
                  {samples, SRe}] ++ average(SRe, STRe, Length)}
    ];
format_rate(Type, {TG, TGN, TD, TDN, TR, TA, TDG}, {RG, RGN, RD, RDN, RR, RA, RDG},
        {SG, SGN, SD, SDN, SR, SA, SDG}, {STG, STGN, STD, STDN, STR, STA, STDG},
        Length)
  when Type =:= channel_queue_stats_deliver_stats;
       Type =:= channel_stats_deliver_stats;
       Type =:= vhost_stats_deliver_stats;
       Type =:= queue_stats_deliver_stats ->
    [
     {get, TG},
     {get_details, [{rate, RG},
            {samples, SG}] ++ average(SG, STG, Length)},
     {get_no_ack, TGN},
     {get_no_ack_details, [{rate, RGN},
               {samples, SGN}] ++ average(SGN, STGN, Length)},
     {deliver, TD},
     {deliver_details, [{rate, RD},
            {samples, SD}] ++ average(SD, STD, Length)},
     {deliver_no_ack, TDN},
     {deliver_no_ack_details, [{rate, RDN},
                   {samples, SDN}] ++ average(SDN, STDN, Length)},
     {redeliver, TR},
     {redeliver_details, [{rate, RR},
              {samples, SR}] ++ average(SR, STR, Length)},
     {ack, TA},
     {ack_details, [{rate, RA},
            {samples, SA}] ++ average(SA, STA, Length)},
     {deliver_get, TDG},
     {deliver_get_details, [{rate, RDG},
                {samples, SDG}] ++ average(SDG, STDG, Length)}
    ];
format_rate(Type, {TR}, {RR}, {SR}, {STR}, Length)
  when Type =:= channel_process_stats;
       Type =:= queue_process_stats ->
    [
     {reductions, TR},
     {reductions_details, [{rate, RR},
               {samples, SR}] ++ average(SR, STR, Length)}
    ];
format_rate(exchange_stats_publish_out, {TP}, {RP}, {SP}, {STP}, Length) ->
    [
     {publish_out, TP},
     {publish_out_details, [{rate, RP},
                {samples, SP}] ++ average(SP, STP, Length)}
    ];
format_rate(exchange_stats_publish_in, {TP}, {RP}, {SP}, {STP}, Length) ->
    [
     {publish_in, TP},
     {publish_in_details, [{rate, RP},
               {samples, SP}] ++ average(SP, STP, Length)}
    ];
format_rate(Type, {TP}, {RP}, {SP}, {STP}, Length)
  when Type =:= queue_stats_publish;
       Type =:= queue_exchange_stats_publish ->
    [
     {publish, TP},
     {publish_details, [{rate, RP},
                {samples, SP}] ++ average(SP, STP, Length)}
    ];
format_rate(Type, {TR, TU, TM}, {RR, RU, RM}, {SR, SU, SM}, {STR, STU, STM},
        Length) when Type =:= queue_msg_stats;
             Type =:= vhost_msg_stats ->
    [
     {messages_ready, TR},
     {messages_ready_details, [{rate, RR},
            {samples, SR}] ++ average(SR, STR, Length)},
     {messages_unacknowledged, TU},
     {messages_unacknowledged_details, [{rate, RU},
                    {samples, SU}] ++ average(SU, STU, Length)},
     {messages, TM},
     {messages_details, [{rate, RM},
             {samples, SM}] ++ average(SM, STM, Length)}
    ];
format_rate(node_coarse_stats, {TF, TS, TM, TD, TP, TGC, TGCW, TCS},
            {RF, RS, RM, RD, RP, RGC, RGCW, RCS},
        {SF, SS, SM, SD, SP, SGC, SGCW, SCS},
        {STF, STS, STM, STD, STP, STGC, STGCW, STCS}, Length) ->
    [
     {mem_used, TM},
     {mem_used_details, [{rate, RM},
             {samples, SM}] ++ average(SM, STM, Length)},
     {fd_used, TF},
     {fd_used_details, [{rate, RF},
            {samples, SF}] ++ average(SF, STF, Length)},
     {sockets_used, TS},
     {sockets_used_details, [{rate, RS},
                 {samples, SS}] ++ average(SS, STS, Length)},
     {proc_used, TP},
     {proc_used_details, [{rate, RP},
              {samples, SP}] ++ average(SP, STP, Length)},
     {disk_free, TD},
     {disk_free_details, [{rate, RD},
              {samples, SD}] ++ average(SD, STD, Length)},
     {gc_num, TGC},
     {gc_num_details, [{rate, RGC},
               {samples, SGC}] ++ average(SGC, STGC, Length)},
     {gc_bytes_reclaimed, TGCW},
     {gc_bytes_reclaimed_details, [{rate, RGCW},
                   {samples, SGCW}] ++ average(SGCW, STGCW, Length)},
     {context_switches, TCS},
     {context_switches_details, [{rate, RCS},
                 {samples, SCS}] ++ average(SCS, STCS, Length)}
    ];
format_rate(node_persister_stats,
            {TIR, TIB, TIA, TIWC, TIWB, TIWAT, TIS, TISAT, TISC,
             TISEAT, TIRC, TMRTC, TMDTC, TMSRC, TMSWC, TQIJWC, TQIWC, TQIRC,
             TIO, TIOAT},
            {RIR, RIB, _RIA, RIWC, RIWB, _RIWAT, RIS, _RISAT, RISC,
             _RISEAT, RIRC, RMRTC, RMDTC, RMSRC, RMSWC, RQIJWC, RQIWC, RQIRC,
             RIO, _RIOAT},
        {SIR, SIB, SIA, SIWC, SIWB, SIWAT, SIS, SISAT, SISC,
             SISEAT, SIRC, SMRTC, SMDTC, SMSRC, SMSWC, SQIJWC, SQIWC, SQIRC,
             SIO, SIOAT},
        {STIR, STIB, _STIA, STIWC, STIWB, _STIWAT, STIS, _STISAT, STISC,
             _STISEAT, STIRC, STMRTC, STMDTC, STMSRC, STMSWC, STQIJWC, STQIWC, STQIRC,
             STIO, _STIOAT}, Length) ->
    %% Calculates average times for read/write/sync/seek from the
    %% accumulated time and count
    %% io_<op>_avg_time is the average operation time for the life of the node
    %% io_<op>_avg_time_details/rate is the average operation time during the
    %% last time unit calculated (thus similar to an instant rate)

    [
     {io_read_count, TIR},
     {io_read_count_details, [{rate, RIR},
                  {samples, SIR}] ++ average(SIR, STIR, Length)},
     {io_read_bytes, TIB},
     {io_read_bytes_details, [{rate, RIB},
                 {samples, SIB}] ++ average(SIB, STIB, Length)},
     {io_read_avg_time, avg_time(TIA, TIR)},
     {io_read_avg_time_details, [{samples, unit_samples(SIA, SIR)}] ++
          avg_time_details(avg_time(TIA, TIR))},
     {io_write_count, TIWC},
     {io_write_count_details, [{rate, RIWC},
                   {samples, SIWC}] ++ average(SIWC, STIWC, Length)},
     {io_write_bytes, TIWB},
     {io_write_bytes_details, [{rate, RIWB},
                   {samples, SIWB}] ++ average(SIWB, STIWB, Length)},
     {io_write_avg_time, avg_time(TIWAT, TIWC)},
     {io_write_avg_time_details, [{samples, unit_samples(SIWAT, SIWC)}] ++
          avg_time_details(avg_time(TIWAT, TIWC))},
     {io_sync_count, TIS},
     {io_sync_count_details, [{rate, RIS},
                  {samples, SIS}] ++ average(SIS, STIS, Length)},
     {io_sync_avg_time, avg_time(TISAT, TIS)},
     {io_sync_avg_time_details, [{samples, unit_samples(SISAT, SIS)}] ++
          avg_time_details(avg_time(TISAT, TIS))},
     {io_seek_count, TISC},
     {io_seek_count_details, [{rate, RISC},
                  {samples, SISC}] ++ average(SISC, STISC, Length)},
     {io_seek_avg_time, avg_time(TISEAT, TISC)},
     {io_seek_avg_time_details, [{samples, unit_samples(SISEAT, SISC)}] ++
          avg_time_details(avg_time(TISEAT, TISC))},
     {io_reopen_count, TIRC},
     {io_reopen_count_details, [{rate, RIRC},
                {samples, SIRC}] ++ average(SIRC, STIRC, Length)},
     {mnesia_ram_tx_count, TMRTC},
     {mnesia_ram_tx_count_details, [{rate, RMRTC},
                    {samples, SMRTC}] ++ average(SMRTC, STMRTC, Length)},
     {mnesia_disk_tx_count, TMDTC},
     {mnesia_disk_tx_count_details, [{rate, RMDTC},
                     {samples, SMDTC}] ++ average(SMDTC, STMDTC, Length)},
     {msg_store_read_count, TMSRC},
     {msg_store_read_count_details, [{rate, RMSRC},
                     {samples, SMSRC}] ++ average(SMSRC, STMSRC, Length)},
     {msg_store_write_count, TMSWC},
     {msg_store_write_count_details, [{rate, RMSWC},
                      {samples, SMSWC}] ++ average(SMSWC, STMSWC, Length)},
     {queue_index_journal_write_count, TQIJWC},
     {queue_index_journal_write_count_details, [{rate, RQIJWC},
                        {samples, SQIJWC}] ++ average(SQIJWC, STQIJWC, Length)},
     {queue_index_write_count, TQIWC},
     {queue_index_write_count_details, [{rate, RQIWC},
                    {samples, SQIWC}] ++ average(SQIWC, STQIWC, Length)},
     {queue_index_read_count, TQIRC},
     {queue_index_read_count_details, [{rate, RQIRC},
                       {samples, SQIRC}] ++ average(SQIRC, STQIRC, Length)},
     {io_file_handle_open_attempt_count, TIO},
     {io_file_handle_open_attempt_count_details, [{rate, RIO},
                          {samples, SIO}] ++ average(SIO, STIO, Length)},
     {io_file_handle_open_attempt_avg_time, avg_time(TIOAT, TIO)},
     {io_file_handle_open_attempt_avg_time_details,
      [{samples, unit_samples(SIOAT, SIO)}] ++ avg_time_details(avg_time(TIOAT, TIO))}
    ];
format_rate(node_node_coarse_stats, {TS, TR}, {RS, RR}, {SS, SR}, {STS, STR}, Length) ->
    [
     {send_bytes, TS},
     {send_bytes_details, [{rate, RS},
               {samples, SS}] ++ average(SS, STS, Length)},
     {recv_bytes, TR},
     {recv_bytes_details, [{rate, RR},
               {samples, SR}] ++ average(SR, STR, Length)}
    ].

avg_time_details(Avg) ->
    %% Rates don't make sense here, populate it with the average.
    [{rate, Avg}, {avg_rate, Avg}, {avg, Avg}].

average(_Samples, _Total, Length) when Length =< 1->
    [];
average(Samples, Total, Length) ->
    [{sample, S2}, {timestamp, T2}] = hd(Samples),
    [{sample, S1}, {timestamp, T1}] = lists:last(Samples),
    [{avg_rate, (S2 - S1) * 1000 / (T2 - T1)},
     {avg, Total / Length}].

rate_from_last_increment(Table, {TS, _} = Last, T, RangePoint) ->
    case TS - RangePoint of % [0]
        D when D >= 0 ->
            case rate_from_last_increment(Last, T) of
                unknown ->
                    empty(Table, 0.0);
                Rate ->
                    Rate
            end;
        _ ->
            empty(Table, 0.0)
    end.

%% [0] Only display the rate if it's live - i.e. ((the end of the
%% range) - interval) corresponds to the last data point we have
rate_from_last_increment(_Total, []) ->
    unknown;
rate_from_last_increment(Total, [H | _T]) ->
    rate_from_difference(Total, H).

rate_from_difference({TS0, {A0, A1, A2}}, {TS1, {B0, B1, B2}}) ->
    Interval = TS0 - TS1,
    {rate(A0, B0, Interval), rate(A1, B1, Interval), rate(A2, B2, Interval)};
rate_from_difference({TS0, {A0, A1}}, {TS1, {B0, B1}}) ->
    Interval = TS0 - TS1,
    {rate(A0, B0, Interval), rate(A1, B1, Interval)};
rate_from_difference({TS0, {A0, A1, A2, A3, A4, A5, A6}},
             {TS1, {B0, B1, B2, B3, B4, B5, B6}}) ->
    Interval = TS0 - TS1,
    {rate(A0, B0, Interval), rate(A1, B1, Interval), rate(A2, B2, Interval),
     rate(A3, B3, Interval), rate(A4, B4, Interval), rate(A5, B5, Interval),
     rate(A6, B6, Interval)};
rate_from_difference({TS0, {A0, A1, A2, A3, A4, A5, A6, A7}},
             {TS1, {B0, B1, B2, B3, B4, B5, B6, B7}}) ->
    Interval = TS0 - TS1,
    {rate(A0, B0, Interval), rate(A1, B1, Interval), rate(A2, B2, Interval),
     rate(A3, B3, Interval), rate(A4, B4, Interval), rate(A5, B5, Interval),
     rate(A6, B6, Interval), rate(A7, B7, Interval)};
rate_from_difference({TS0, {A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13,
                A14, A15, A16, A17, A18, A19}},
             {TS1, {B0, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13,
                B14, B15, B16, B17, B18, B19}}) ->
    Interval = TS0 - TS1,
    {rate(A0, B0, Interval), rate(A1, B1, Interval), rate(A2, B2, Interval),
     rate(A3, B3, Interval), rate(A4, B4, Interval), rate(A5, B5, Interval),
     rate(A6, B6, Interval), rate(A7, B7, Interval), rate(A8, B8, Interval),
     rate(A9, B9, Interval), rate(A10, B10, Interval), rate(A11, B11, Interval),
     rate(A12, B12, Interval), rate(A13, B13, Interval), rate(A14, B14, Interval),
     rate(A15, B15, Interval), rate(A16, B16, Interval), rate(A17, B17, Interval),
     rate(A18, B18, Interval), rate(A19, B19, Interval)};
rate_from_difference({TS0, {A0}}, {TS1, {B0}}) ->
    Interval = TS0 - TS1,
    {rate(A0, B0, Interval)}.

rate(V1, V2, Interval) when is_number(V1), is_number(V2) ->
    (V1 - V2) * 1000 / Interval;
rate(_, _, _) ->
    0.

append_sample(S, TS, List) ->
    [[{sample, S}, {timestamp, TS}] | List].

%%----------------------------------------------------------------------------
%% Match specs to select from the ETS tables
%%----------------------------------------------------------------------------

avg_time(_Total, Count) when Count == 0;
                 Count == 0.0 ->
    0.0;
avg_time(Total, Count) ->
    (Total / Count) / ?MICRO_TO_MILLI.

unit_samples(Total, Count) ->
    lists:zipwith(fun(T, C) ->
                          TS = proplists:get_value(timestamp, T),
                          Sample = avg_time(proplists:get_value(sample, T),
                                            proplists:get_value(sample, C)),
                          [{sample, Sample}, {timestamp, TS}]
                  end, Total, Count).

empty(Table, Def) ->
    rabbit_mgmt_data:empty(Table, Def).
