local TOO_LONG_CALL_THRESHOLD = 0.1

local clock = require 'clock'
local json = require 'json'.new()
json.cfg{ encode_use_tostring = true }

local function ftail(fname, args, start, ...)
    local run = clock.realtime() - start
    if run > TOO_LONG_CALL_THRESHOLD then
        log.info("Function call %s(%s) was too long: %0.2fs", fname, json.encode(args), run)
    end
    return ...
end

local function ftrace(fname, func)
    return function(...)
        local start = clock.realtime()
        return ftail(fname, {...}, start, func(...))
    end
end

local function apply_ftrace(name, namespace)
    for fname, v in pairs(namespace) do
        if type(v) == 'table' then
            apply_ftrace(name .. '.' .. fname, v)
        elseif type(v) == 'function' and v ~= ftrace then
            namespace[fname] = ftrace(name .. '.' .. fname, v)
        end
    end
end

apply_ftrace('app',app)