--[[
    stuff to help with the review mechanics
]]

--[[
    manipulates `Prompt` `prompt` in-place as it should be
    when reviewed at timestamp `revtime` with review success `revsucc`
]]
local function update(prompt, revtime, revsucc)
    if revsucc then
        local ad = revtime - prompt.time
        prompt.delay = 2 * ad + math.max(40000 - 0.5 * ad, 0)
        prompt.succ = prompt.succ + 1
    else
        prompt.delay = 30
        prompt.fail = prompt.fail + 1
    end
    prompt.time = revtime
end

--[[
    checks (returns boolean) if `Prompt` `prompt` should be reviewed now
]]
local function should(prompt)
    return os.time() - prompt.time >= prompt.delay
end

return { update = update, should = should }