-- Created by Jef Roosens
--
-- This module contains functions which ease fuel management in a turtle


-- local turtle = require('turtle')
local module  = {}
module.logger = require("jlib.log").Logger:new{level = -1}


-- Refuel the turtle using the given slot; tries to optimize refuel speed by
-- calculating needed refuel count
--
-- @param slot slot to refuel from
-- @param goal refuel goal to reach
-- @return wether the refuel was enough
function module.refuel_from(slot, goal)
    -- First, we get the current level
    local start = turtle.getFuelLevel()

    -- If we've already reached the goal, just return true
    if start >= goal then return true end

    -- Select the slot and refuel once
    turtle.select(slot)
    turtle.refuel(1)

    -- Get the difference
    local level = turtle.getFuelLevel()
    local diff = level - start

    -- If the diff is 0 the slot is empty or can't refuel, so return false
    if diff == 0 then return false end

    -- Calculate needed refuels
    local needed = math.ceil((goal - level) / diff)

    -- Do the refuel
    turtle.refuel(needed)

    -- Return wether or not we reached the goal
    return turtle.getFuelLevel() >= goal

end


-- Check if the turtle has enough fuel; takes a table of preferred items
--
-- @param goal fuel goal to reach
-- @param preferred table containing names of preferred items
-- @return wether or not the fuel level was reached
function module.check(goal, preferred)
    -- Convert table to set for faster lookup
    local set = {}

    if preferred then
        for _, v in ipairs(preferred) do
            set[v] = true
        end
    end

    -- Turtle needs to be able to get down at all times
    local i, done = 1, turtle.getFuelLevel() >= goal

    -- Instantly quit if it's already good
    -- This check is mostly useful voor the logging aspect
    if done then
        module.logger:info("No refuel needed.")
        return true
    end

    -- Store all non-preferred options
    local options = {}

    -- Iterate over all 16 slots, or stop earlier if possible
    while not done and i <= 16 do
        local data = turtle.getItemDetail(i)

        if data and set[data.name] then
            done = module.refuel_from(i, goal)

        else
            table.insert(options, i)

        end

        i = i + 1
    end

    -- Exit if goal has been reached
    if done then
        module.logger:info("Refueled using preferred.")

        return true
    end

    -- Process non-preferred options
    for _, j in pairs(options) do
        done = module.refuel_from(j, goal)

        if done then
            module.logger:info("Refueled using non-preferred.")

            return true
        end
    end

    module.logger:warning(
        "Refuel failed. Missing: " .. goal - turtle.getFuelLevel())

    return false
end


return module