COMPUTERCRAFT 3D MAZE SOLVER

--[[
    COMPUTERCRAFT 3D MAZE SOLVER
    BY 0099
    FOR KONLAB'S COMPETITION
]]

-- directions:
-- 1. north
-- 2. east
-- 3. south
-- 4. west
-- 5. up
-- 6. down

local opp = {
    [1] = 3,
    [2] = 4,
    [3] = 1,
    [4] = 2,
    [5] = 6,
    [6] = 5,
}

local right = {
    [1] = 2,
    [2] = 3,
    [3] = 4,
    [4] = 1,
}

local left = {
    [1] = 4,
    [2] = 1,
    [3] = 2,
    [4] = 3,
}

function seqGen()
    local f
    f = function(n, l)
        for i=1,n,1 do
            if l == 1 then
                coroutine.yield(tostring(i))
            else
                local c = coroutine.create(f)
                while true do
                    local status, a = coroutine.resume(c, n, l-1)
                    if status == false then
                        error("Coroutine error (1) : "..a)
                    end
                    if a == "end" then
                        break
                    end
                    coroutine.yield(tostring(i)..","..a)
                end
            end
        end
        return "end"
    end
    local f2 = function()
        for i=1,1000000,1 do
            local c = coroutine.create(f)
            while true do
                local status, a = coroutine.resume(c, i, i)
                if status == false then
                    error("Coroutine error (2) : "..a)
                end
                if a == "end" then
                    break
                end
                coroutine.yield(a)
            end
        end
        return "end"
    end
    local c = coroutine.create(f2)
    local f3 = function()
        while true do
            local status, a = coroutine.resume(c)
            if status == false then
                error("Coroutine error (3) : "..a)
            end
            if a == "end" then
                error("This maze is impossible. I give up.")
            end
            local t = loadstring("return {"..a.."}")()
            for i=1,#t,1 do
                coroutine.yield(t[i])
            end
        end
    end
    local c2 = coroutine.create(f3)
    local f4 = function()
        local status, a = coroutine.resume(c2)
        if status == false then
            error("Coroutine error (4) : "..a)
        end
        return a
    end
    return f4
end

function scan()
    local dirs = {}
    local dirs2 = {}
    local n = 0
    if map[gx] and map[gx][gy] and map[gx][gy][gz] then
        return unpack(map[gx][gy][gz])
    end
    for i=1,4,1 do
        if turtle.detect() == false then
            dirs[dir] = true
            table.insert(dirs2, dir)
            n = n + 1
        end
        turtle.turnRight()
        dir = right[dir]
    end
    if turtle.detectUp() == false then
        dirs[5] = true
        table.insert(dirs2, 5)
        n = n+1
    end
    if turtle.detectDown() == false then
        dirs[6] = true
        table.insert(dirs2, 6)
        n = n+1
    end
    if not map[gx] then
        map[gx] = {}
    end
    if not map[gx][gy] then
        map[gx][gy] = {}
    end
    map[gx][gy][gz] = {dirs, dirs2, n}
    return dirs, dirs2, n
end

function goTo(d)
    print("Going to "..tostring(d))
    if d == 5 then
        turtle.up()
        gy = gy+1
    elseif d == 6 then
        turtle.down()
        gy = gy-1
    else
        if d == right[dir] then
            turtle.turnRight()
        elseif d == left[dir] then
            turtle.turnLeft()
        elseif d == opp[dir] then
            turtle.turnRight()
            turtle.turnRight()
        end
        turtle.forward()
        dir = d
        if dir == 1 then
            gz = gz-1
        elseif dir == 2 then
            gx = gx+1
        elseif dir == 3 then
            gz = gz+1
        elseif dir == 4 then
            gx = gx-1
        end
    end
    cameFrom = opp[d]
end

function main()
    local gen = seqGen()
    dir = 1
    gx, gy, gz = 0, 0, 0
    map = {}
    while true do
        print(string.format("x=%d, y=%d, z=%d", gx, gy, gz))
        if turtle.getFuelLevel() == 0 then
            turtle.refuel()
        end
        local dirs, dirs2, n = scan()
        print(tostring(n).." directions detected")
        print(unpack(dirs2))
        if n == 1 then
            for i in pairs(dirs) do
                goTo(i)
            end
        elseif n == 2 then
            for i in pairs(dirs) do
                if i ~= cameFrom then
                    goTo(i)
                    break
                end
            end
        else
            local d = gen()
            print("Sequence: "..tostring(d))
            local j
            for i, d2 in pairs(dirs2) do
                if d2 == cameFrom or cameFrom == nil then
                    j = i
                    break
                end
            end
            print("Old dir: "..tostring(dirs2[j]))
            j = (j-1+d)%n+1
            print("New dir: "..tostring(dirs2[j]))
            goTo(dirs2[j])
        end
    end
end

main()