#!/usr/bin/lua
-- this tries to create the same metrics as: https://github.com/SuperQ/chrony_exporter
--

local chrony_sources_cmd = 'chronyc -n -c sources'
local chrony_tracking_cmd = 'chronyc -n -c tracking'

local source_states = {}
source_states['*'] = "sync"
source_states['?'] = "unreach"
source_states['x'] = "falseticker"
source_states['~'] = "jittery"
source_states['+'] = "candidate"
source_states['-'] = "outlier"

local source_modes = {}
source_modes['^'] = "client"
source_modes['='] = "peer"
source_modes['#'] = "reference clock"


function get_cmdoutput(cmd)
    local chronyc_out, err = io.popen(cmd)
    if err ~= nil then return nil, err end

    local lines = {}
    for line in chronyc_out:lines() do
        if line == "506 Cannot talk to daemon" then
            return nil, "line"
        end
        table.insert(lines, line)
    end
    return lines
end

function comma_split(s)
    local elements = {}
    for element in s:gmatch("([^,]*)") do
        if element ~= "" then table.insert(elements, element) end
    end
    return elements
end

local function scrape()
    local chrony_tracking = get_cmdoutput(chrony_tracking_cmd)
    local chrony_sources = get_cmdoutput(chrony_sources_cmd)

    local metric_up = metric("chrony_up", "gauge")
    if chrony_tracking == nil or chrony_sources == nil then
        metric_up(nil, 0)
        return
    end
    metric_up(nil, 1)

    for _, line in ipairs(chrony_tracking) do
        local items = comma_split(line)
        metric("chrony_tracking_info", "gauge", { tracking_address = items[2], tracking_refid = items[1]}, 1)
        metric("chrony_tracking_last_offset_seconds", "gauge", nil, tonumber(items[6]))
        metric("chrony_tracking_reference_timestamp_seconds", "gauge", nil, tonumber(items[4]))
        metric("chrony_tracking_rms_offset_seconds", "gauge", nil, tonumber(items[7]))
        metric("chrony_tracking_root_delay_seconds", "gauge", nil, tonumber(items[11]))
        metric("chrony_tracking_root_dispersion_seconds", "gauge", nil, tonumber(items[12]))
        metric("chrony_tracking_stratum", "gauge", nil, tonumber(items[3]))
        metric("chrony_tracking_system_time_seconds", "gauge", nil, tonumber(items[5]))
    end

    local metric_sources_ls_age = metric("chrony_sources_last_sample_age_seconds", "gauge")
    for _, line in ipairs(chrony_sources) do
        local items = comma_split(line)
        metric_sources_ls_age({ source_address = items[3] }, tonumber(items[7]))
    end
    local metric_sources_ls_error = metric("chrony_sources_last_sample_error_margin_seconds", "gauge")
    for _, line in ipairs(chrony_sources) do
        local items = comma_split(line)
        metric_sources_ls_error({ source_address = items[3] }, tonumber(items[10]))
    end
    local metric_sources_ls_offset = metric("chrony_sources_last_sample_offset_seconds", "gauge")
    for _, line in ipairs(chrony_sources) do
        local items = comma_split(line)
        metric_sources_ls_offset({ source_address = items[3] }, tonumber(items[8]))
    end
    local metric_sources_polling_int = metric("chrony_sources_polling_interval_seconds", "gauge")
    for _, line in ipairs(chrony_sources) do
        local items = comma_split(line)
        metric_sources_polling_int({ source_address = items[3] }, 2^tonumber(items[5]))
    end
    local metric_sources_info = metric("chrony_sources_state_info", "gauge")
    for _, line in ipairs(chrony_sources) do
        local items = comma_split(line)
        metric_sources_info({ source_address = items[3], source_mode = source_modes[items[1]], source_state = source_states[items[2]] }, 1)
    end
    local metric_sources_stratum = metric("chrony_sources_stratum", "gauge")
    for _, line in ipairs(chrony_sources) do
        local items = comma_split(line)
        metric_sources_stratum({ source_address = items[3] }, tonumber(items[4]))
    end
end

return { scrape = scrape }