OCDroneOS

local chat = part "chat"
local nav = part "nav"
local prefix = "$d "

-- A bunch of colors for the rotory areas in different situations
local idleCol = 0x00FF00
local movingCol = 0x0000FF
local problemCol = 0xFF0000
local transferCol = 0xFFFF00
local calculatingCol = 0x00FFFF

-- ROUTING TABLE
-- Format: {["waypointName"] = {"placeWaypointIsReachableFrom"}}
local routing = {
    ["GTech Tree"] = {"Home Base", "Tree On Mountain"},
    ["Tree On Mountain"] = {"GTech Tree", "Gaia"},
    ["Gaia"] = {"Tree On Mountain", "Desert 01"},
    ["Desert 01"] = {"Gaia", "Link2006"},
    ["Link2006"] = {"Desert 01", "Mushroom 01"},
    ["Wojbie Incorporated"] = {"Home Base"},
    ["Home Base"] = {"Wojbie Incorporated", "GTech Tree", "RandomMountainBit"},
    ["TerraInc"] = {"RandomMountainBit"},
    ["RandomMountainBit"] = {"TerraInc", "Home Base", "Dank Lords HQ"},
    ["Dank Lords HQ"] = {"RandomMountainBit"},
    ["Mushroom 01"] = {"Link2006", "Mushroom 02"},
    ["Mushroom 02"] = {"Mushroom 01", "Admins"},
    ["Admins"] = {"Mushroom 02"}
}

chat.setName(drone.name())
status(drone.name())

function setCol(col)
    drone.setLightColor(col)
end

-- Gets the drone's power level as a float between 0 and 1
function getPower()
    return computer.energy() / computer.maxEnergy()
end

-- Slightly safer movement between two reasonably far points
function go(rx, ry, rz)
    drone.move(0, 100, 0)
    sleep(3)
    drone.move(rx, ry, rz)
    drone.move(0, -100, 0)
end

-- Gets position of a nearby named waypoint
function getWaypoint(name)
    local waypoints = nav.findWaypoints(128)
    waypoints.n = nil -- This seems to turn up in the returned value. I don't really know why it exists.

    for _, point in pairs(waypoints) do
        if point.label == name then
            return point.position[1], point.position[2], point.position[3]
        end
    end
end

-- Checks whether a waypoint is near enough to be located, and existent
function waypointExists(name)
    local result = getWaypoint(name)

    if result then
        return true
    else
        return false
    end
end

-- Goes to a waypoint within navigation range
function moveToSimple(name)
    local x, y, z = getWaypoint(name)
    chat.say("Going to relative coords " .. x .. ", " .. y .. ", " .. z .. " (waypoint " .. name .. ")")
    setCol(movingCol)
    go(x, y, z)

    while drone.getVelocity() > 0.001 do
            sleep(0.5)
    end
end

-- Reverses a table - does not do it in-place
function reverse(tab)
    local ret = {}
    for k, v in pairs(tab) do
        ret[#tab - k + 1] = v
    end

    return ret
end

-- from https://www.redblobgames.com/pathfinding/a-star/introduction.html
-- Gets a route from from to to using the routing table as a graph to search
function getRoute(from, to)
    -- places to search next
    local frontier = {from}
    -- where each place was reached from
    local cameFrom = {[from] = nil}

    while #frontier > 0 do
        local current = table.remove(frontier, 1)
        for _, nextLoc in pairs(routing[current]) do
            if not cameFrom[nextLoc] then -- check if nextLoc has an entry in cameFrom
                table.insert(frontier, nextLoc)
                cameFrom[nextLoc] = current
            end
        end
    end

    -- Extrapolate from reversed path available in cameFrom
    local current = to
    local path = {}

    while current ~= from do
        table.insert(path, current)
        current = cameFrom[current]
    end

    return reverse(path)
end

function moveTo(from, to)
    if waypointExists(to) then
        moveToSimple(to)
    else
        setCol(calculatingCol)
        for _, waypoint in pairs(getRoute(from, to)) do
            moveToSimple(waypoint)
        end
    end
end

function chatListen()
    while true do
        local type, _, user, msg = computer.pullSignal()

        if type == "chat_message" then
            return user, msg
        end
    end
end

chat.say("Navigation range is " .. tostring(nav.getRange()) .. ".")

while true do
    setCol(idleCol)

    if getPower() < 0.2 then
        setCol(problemCol)
        chat.say "Please return me to gollark. I am stranded and on low power."
        status "POWER LOW"
        sleep(100)
    end

    local usr, msg = chatListen()

    if string.sub(msg, 1, #prefix) == prefix then
        local loc = string.sub(msg, #prefix + 1)
        chat.say('"' .. loc .. '"')

        setCol(transferCol)

        for i = 1, 4 do
            drone.select(i)
            drone.suck(0, 64)
            sleep(1)
        end

        moveTo("Home Base", loc)

        setCol(transferCol)

        for i = 1, 4 do
            drone.select(i)
            drone.drop(0)
        end

        chat.say("Enjoy your things!")

        moveTo(loc, "Home Base")
    end
end