-- Program to gather excess from farms and compost it

local CHECKS = {}
CHECKS["minecraft:kelp"] = 8 * 64

local SOURCES =
{ ""
}

local COMPOST_INPUT = ""
local COMPOST_OUTPUT = ""
local STORAGE = ""

local SLEEP_TIME = 40

function tally_up (src)
    local counts = {}
    for _, item in pairs(peripheral.call(src, "list")) do
        if counts[item.name] == nil then counts[item.name] = 0 end
        counts[item.name] = counts[item.name] + item.count
    end
    return counts
end

function compare_counts (count1, count2)
    local diffs = {}
    for item, count in pairs(count1) do
        if count2[item] ~= nil then
            diffs[item] = count - count2[item]
        end
    end
    return diffs
end

function compost (src, item_name, amount)
    if amount < 1 then return end
    local amount_moved = 0
    -- 1. scan through inventory until {item} is found
    for slot, item in pairs(peripheral.call(src, "list")) do
        if item.name == item_name then
            -- 2. move up to {amount} to compost, recording amount moved
            amount_moved = peripheral.call(
                COMPOST_INPUT, "pullItems", src, slot, amount
            )
            break
        end
    end
    -- 3. call again recursively
    return compost(src, item_name, amount - amount_moved)
end

function move_all (src, dest)
    for slot, item in pairs(peripheral.call(src, "list")) do
        peripheral.call(src, "pushItems", dest, slot)
    end
end

while true do
    if STORAGE ~= "" then move_all(COMPOST_OUTPUT, STORAGE) end
    for _, source in ipairs(SOURCES) do
        local totals = tally_up(source)
        local diffs = compare_counts(totals, CHECKS)
        for item, diff in pairs(diffs) do
            if diff > 0 then
                compost(source, item, diff)
            end
        end
    end
    os.sleep(SLEEP_TIME)
end