GPS Tower

--Originally by MysticT
--TODO: Implement HTTP Publishing total amount of GPS Requests served

local tLocations = {}
local tKnownLocations = {}
local bDebug = false

local function printUsage()
    local sName = fs.getName(shell.getRunningProgram())
    print("Usage:")
    print(sName, " receive [debug]")
    print(sName, " host id x y z")
    return false
end

--Download config API
local function pastebinGet(code,path)
    local sCode = code
    local sFile = path
    local sPath = shell.resolve( sFile )
    if fs.exists( sPath ) then
        fs.delete(sPath)
    end

    local response = http.get(
        "http://pastebin.com/raw.php?i="..textutils.urlEncode( sCode )
        )

    if response then
        local sResponse = response.readAll()
        response.close()

        local file = fs.open( sPath, "w" )
        file.write( sResponse )
        file.close()
                return true

    else
        return false
    end
end

if not http then
    print( "GPS requires the HTTP API" )
    print( "Set enableAPI_http to 1 in mod_ComputerCraft.cfg" )
    return false
end

if not fs.exists("archiveAPI") then
    fs.makeDir("archiveAPI")
end

fs.delete("archiveAPI/config")
fs.delete("archiveAPI/gbang")

if not fs.exists("archiveAPI/config") then
    if pastebinGet("fkcMT9CE","archiveAPI/config") then
    else
        print("Something went wrong! No response!")
        return false
    end
end

if not fs.exists("archiveAPI/gbang") then
    if pastebinGet("MT2FLYq0","archiveAPI/gbang") then
    else
        print("Something went wrong! No response!")
        return false
    end
end

-- Helper functions

local function clear()
    term.clear()
    term.setCursorPos(1, 1)
end

local function table_size(t)
    local i = 0
    for _,_ in pairs(t) do
        i = i + 1
    end
    return i
end

local function connect()
    for _,s in ipairs(rs.getSides()) do
        if peripheral.isPresent(s) and peripheral.getType(s) == "modem" then
            rednet.open(s)
            return true
        end
    end
    print("No modem attached")
    return false
end

local function _print(...)
    if bDebug then
        print(...)
    end
end

local function vector_equal(v1, v2)
    return v1.x == v2.x and v1.y == v2.y and v1.z == v2.z
end

-- Load/Save functions

local function save()
    _print("Saving locations...")
    local file = fs.open("locations.dat", "w")
    if file then
        for id, loc in pairs(tKnownLocations) do
            file.writeLine(tostring(id)..": "..tostring(loc.x)..", "..tostring(loc.y)..", "..tostring(loc.z))
        end
        file.close()
        _print("Locations saved")
        return true
    end
    _print("Error saving locations")
    return false
end

local function load()
    _print("Loading locations")
    local file = fs.open("locations.dat", "r")
    if file then
        local i = 0
        local sLine = file.readLine()
        while sLine do
            local sId, sX, sY, sZ = string.match(sLine, "(%d+): (%-?%d+), (%-?%d+), (%-?%d+)")
            local id, x, y, z = tonumber(sId), tonumber(sX), tonumber(sY), tonumber(sZ)
            if id and x and y and z then
                tKnownLocations[id] = vector.new(x, y, z)
                i = i + 1
            end
            sLine = file.readLine()
        end
        file.close()
        _print(n, " locations loaded")
        return true, i
    end
    _print("Error loading locations")
    return false
end

-- Location functions

local function trilaterate(A, B, C)
    local a2b = B.position - A.position
    local a2c = C.position - A.position
    if math.abs( a2b:normalize():dot( a2c:normalize() ) ) > 0.999 then
        return nil
    end
    local d = a2b:length()
    local ex = a2b:normalize( )
    local i = ex:dot( a2c )
    local ey = (a2c - (ex * i)):normalize()
    local j = ey:dot( a2c )
    local ez = ex:cross( ey )
    local r1 = A.distance
    local r2 = B.distance
    local r3 = C.distance
    local x = (r1*r1 - r2*r2 + d*d) / (2*d)
    local y = (r1*r1 - r3*r3 - x*x + (x-i)*(x-i) + j*j) / (2*j)
    local result = A.position + (ex * x) + (ey * y)
    local zSquared = r1*r1 - x*x - y*y
    if zSquared > 0 then
        local z = math.sqrt(zSquared)
        local result1 = result + (ez * z)
        local result2 = result - (ez * z)
        local rounded1, rounded2 = result1:round(), result2:round()
        if rounded1.x ~= rounded2.x or rounded1.y ~= rounded2.y or rounded1.z ~= rounded2.z then
            return result1, result2
        else
            return rounded1
        end
    end
    return result:round()
end

local function narrow(p1, p2, fix)
    local dist1 = math.abs((p1 - fix.position):length() - fix.distance)
    local dist2 = math.abs((p2 - fix.position):length() - fix.distance)
    if math.abs(dist1 - dist2) < 0.05 then
        return p1, p2
    elseif dist1 < dist2 then
        return p1:round()
    else
        return p2:round()
    end
end

function locate(id)
    local tFixes = {}
    local p1, p2
    for _,t in pairs(tLocations[id]) do
        table.insert(tFixes, { ["position"] = vector.new(t.x, t.y, t.z), ["distance"] = t.d })
    end
    local i = 3
    while (p1 == nil or p2 ~= nil) and i <= #tFixes do
        if not p1 then
            p1, p2 = trilaterate(tFixes[1], tFixes[2], tFixes[i])
        else
            p1, p2 = narrow(p1, p2, tFixes[i])
        end
        i = i + 1
    end
    if p1 and p2 then
        _print("Ambiguous position")
        _print("Could be "..p1.x..","..p1.y..","..p1.z.." or "..p2.x..","..p2.y..","..p2.z)
    elseif p1 then
        if not tKnownLocations[id] or not vector_equal(tKnownLocations[id], p1) then
            print("Location added:")
            print(id, ": ", p1)
            tKnownLocations[id] = p1
            save()
        end
    else
        _print("Couldn't determine location for ", id)
    end
end

local function addLocation(id, t)
    if not tLocations[t.id] then
        tLocations[t.id] = {}
    end
    local tLoc = {}
    tLoc.x = t.x
    tLoc.y = t.y
    tLoc.z = t.z
    tLoc.d = t.d
    tLocations[t.id][id] = tLoc
    if table_size(tLocations[t.id]) >= 3 then
        _print("Trying to locate #", t.id)
        locate(t.id)
    end
end

-- Event handlers

local function handle_message(id, msg)
    local st = string.match(msg, "<LOCATION> (.+)")
    if st then
        local t = textutils.unserialize(st)
        if t and type(t) == "table" then
            _print("Location received from ", id, ":")
            _print(t.id, ": ", "(", t.x, ", ", t.y, ", ", t.z, ", ", t.d, ")")
            addLocation(id, t)
        end
    end
end

local function handle_char(c)
    c = string.lower(c)
    if c == "l" then
        print("Locations:")
        for id, loc in pairs(tKnownLocations) do
            print(id, ": ", loc)
        end
    elseif c == "c" then
        clear()
    end
end

-- Start program

local function host()
    print("Stuff")
    os.loadAPI("archiveAPI/config")
    config.load("configs","config")
    local nMasterID = tonumber(config.readVal("mId"))
    local tLoc = {}
    tLoc.x = tonumber(config.readVal("x"))
    tLoc.y = tonumber(config.readVal("y"))
    tLoc.z = tonumber(config.readVal("z"))
    config.save()
    os.unloadAPI("archiveAPI/config")
    if not nMasterID or not tLoc.x or not tLoc.y or not tLoc.z then
        print("If not")
        printUsage()
        return false
    end
    clear()
    if not connect() then
        print("No modem attached")
        return false
    end
    print("==================================================")
    print("Powered by G&K Industries. Contact representative, gknova61 if any issues.")
    print("==================================================")
    print( "Position is "..tLoc.x..","..tLoc.y..","..tLoc.z )
    print( "Serving GPS requests" )
    local x1,y1 = term.getCursorPos()
    print("0 GPS Requests served")
    term.setCursorPos(x1,y1)
    local nServed = 0
    --print("Waiting for messages...")
    while true do
        local id, msg, dist = rednet.receive()
        --print("Message received from ", id, " at ", dist, " meters.")
        if msg == "PING" then
            rednet.send(id,textutils.serialize({tLoc.x,tLoc.y,tLoc.z}))
            nServed = nServed + 1
            if nServed > 1 then
                local x,y = term.getCursorPos()
                term.setCursorPos(1,y-1)
            end
            print(nServed.." GPS Requests served")
        end
        tLoc.id = id
        tLoc.d = dist
        rednet.send(nMasterID, "<LOCATION> "..textutils.serialize(tLoc))
    end
end
local tArgs = {...}
local sAction = tArgs[1]
if sAction == "host" and not fs.exists("configs/config") then
    if #tArgs < 5 then
        print("Check 2")
        printUsage()
        return false
    end
    local mId = tArgs[2]
    local x = tArgs[3]
    local y = tArgs[4]
    local z = tArgs[5]
    os.loadAPI("archiveAPI/config")
    config.load("configs","config")
    config.writeVal("mId",mId)
    config.writeVal("x",x)
    config.writeVal("y",y)
    config.writeVal("z",z)
    config.save()
    os.unloadAPI("archiveAPI/config")
    host()
elseif sAction == "host" and fs.exists("configs/config") then
    host()
end
if sAction == "receive" then
    if #tArgs > 1 then
        if string.lower(tArgs[2]) == "debug" then
            bDebug = true
        else
            print("Chekc 3")
            printUsage()
            return
        end
    end
    clear()
    if not connect() then
        return
    end
    local ok, n = load()
    if ok then
        print("Loaded ", n, " locations")
    end
    print("Press l to list located computers")
    print("Press c to clear the screen")
    while true do
        local evt, arg1, arg2 = os.pullEvent()
        if evt == "rednet_message" then
            handle_message(arg1, arg2)
        elseif evt == "char" then
            handle_char(arg1)
        end
    end
end
if sAction ~= "host" or sAction ~= "receive" then
    if fs.exists("configs/config") then
        host()
    end
end