-- Dropper Controller
-- Watches a dropper peripheral and pulses redstone until it's empty.

local DROPPER_SIDE  = "back"     -- side where the dropper peripheral is
local REDSTONE_SIDE = "back"     -- side facing dropper (for redstone output)
local PULSE_TIME    = 0.3        -- redstone pulse duration in seconds
local POLL_INTERVAL = 0.5        -- how often to check the dropper

-------------------------------------------------
-- Load config from file if present
-------------------------------------------------

local _baseDir = fs.getDir(shell.getRunningProgram())

-- Persistent config path: survives Opus package updates
local _PERSIST_DIR = "usr/config/inventory-manager"
local function _configPath(rel)
    if fs.isDir(_PERSIST_DIR) or fs.isDir("packages/inventory-manager") then
        if not fs.isDir(_PERSIST_DIR) then fs.makeDir(_PERSIST_DIR) end
        return fs.combine(_PERSIST_DIR, rel)
    end
    return fs.combine(_baseDir, rel)
end

local CONFIG_FILE = _configPath(".dropper_config")

if fs.exists(CONFIG_FILE) then
    local f = fs.open(CONFIG_FILE, "r")
    local raw = f.readAll()
    f.close()
    local ok, cfg = pcall(textutils.unserialiseJSON, raw)
    if ok and cfg then
        if cfg.dropperSide  then DROPPER_SIDE  = cfg.dropperSide  end
        if cfg.redstoneSide then REDSTONE_SIDE = cfg.redstoneSide end
        if cfg.pulseTime    then PULSE_TIME    = cfg.pulseTime    end
        if cfg.pollInterval then POLL_INTERVAL = cfg.pollInterval end
    end
end

-------------------------------------------------
-- Helpers
-------------------------------------------------

-- Send a redstone pulse to trigger the dropper
local function pulseRedstone()
    redstone.setOutput(REDSTONE_SIDE, true)
    sleep(PULSE_TIME)
    redstone.setOutput(REDSTONE_SIDE, false)
end

-- Check if the dropper has any items
local function dropperHasItems()
    local dropper = peripheral.wrap(DROPPER_SIDE)
    if not dropper then return false end
    local contents = dropper.list()
    if not contents then return false end
    return next(contents) ~= nil
end

-------------------------------------------------
-- Main
-------------------------------------------------

print("=================================")
print("  Dropper Controller (ID " .. os.getComputerID() .. ")")
print("=================================")
print("")
print("Redstone side: " .. REDSTONE_SIDE)
print("Watching dropper for items...")
print("")

while true do
    if dropperHasItems() then
        print("[DISPENSE] Items detected, firing dropper...")

        -- Keep pulsing until the dropper is empty
        while dropperHasItems() do
            pulseRedstone()
            sleep(0.1)
        end

        print("[OK] Dropper empty.")
    end

    sleep(POLL_INTERVAL)
end