people/actions/tunnel.lua

local dbg
if moddebug then dbg=moddebug.dbg("people") else dbg={v1=function() end,v2=function() end,v3=function() end} end

local function rotate(rel, dir)
    if dir.z < 0 then
        return {x=-rel.x, y=rel.y, z=-rel.z}
    elseif dir.z > 0 then
        return {x=rel.x, y=rel.y, z=rel.z}
    elseif dir.x > 0 then
        return {x=rel.z, y=rel.y, z=-rel.x}
    else
        return {x=-rel.z, y=rel.y, z=rel.x}
    end
end

people.actions.tunnel = function(state)

    if type(state.action.distance) ~= "number" then
        dbg.v1(state.ent.name.." has invalid distance for tunnel action")
        return true, false
    end
    if type(state.action.dir) ~= "table" then
        dbg.v1(state.ent.name.." has invalid dir for tunnel action")
        return true, false
    end
    if state.action.dir.y ~= 0 then
        dbg.v1(state.ent.name.." has invalid y component of dir for tunnel action")
        return true, false
    end
    if math.abs(state.action.dir.x) + math.abs(state.action.dir.z) ~= 1 then
        dbg.v1(state.ent.name.." has invalid x/z components of dir for tunnel action")
        return true, false
    end

    -- On starting, keep the original position and distance. This will allow
    -- us to break off and resume if, for example, we run out of materials or
    -- room to carry the spoils.
    if not state.action.startpos then
        state.action.startpos = vector.round(state.pos)
        state.action.startdist = state.action.distance
    end

    if(state.action.distance <= 0) then
        dbg.v1(state.ent.name.." completed tunnelling")
        return true, true
    end

    -- digpos will be the base centre of the new cross-sectional area
    -- we're going to dig.
    local digpos = vector.add(vector.round(state.pos), state.action.dir)

    -- Tweak (hack) because if we're laying steps, we're standing on them as
    -- we go down. This sucks, and even more so because we might want to
    -- skip the steps until another time if we don't have the materials
    if state.action.dir.y == -1 and state.action.steps and state.action.distance ~= state.action.startdist then
        digpos.y = digpos.y - 1
    end

    local relxaxis
    if state.action.dir.x == 0 then
        relxaxis = "x"
    else
        relxaxis = "z"
    end

    local height = 2
    if state.action.dir.y ~= 0 then
        if state.action.steps then
            height = 4
        else
            height = 3
        end
    end

    -- Make it so we dig from top to bottom when tunnelling downwards, and
    -- bottom to top otherwise.
    local yfrom, yto, ydir
    if state.action.dir.y < 0 then
        yfrom = height
        yto = 0
        ydir = -1
    else
        yfrom = 0
        yto = height
        ydir = 1
    end

    -- "Special" positions are those where supports and lighting are placed
    local special_sup = (state.action.startdist - state.action.distance + 2) % 8 == 7
    local special_light = (state.action.startdist - state.action.distance) % 4 == 3

    -- TODO - the following is all a bit ineffecient, because we look at the
    --        whole cross-section every time through. We could keep track of
    --        where we've got to during a run and skip some.

    for y = yfrom, yto, ydir do
        for x = -1, 1 do
            local thisoff = {x=0, y=y, z=0}
            thisoff[relxaxis] = x
            local thispos = vector.add(digpos, thisoff)
            local dignode = minetest.get_node(thispos)

            -- Steps at the bottom row if needed.
            if y == 0 and state.action.steps and state.action.dir.y ~= 0 then

                if dignode.name == "air" then
                    state.action = {"place", pos=thispos, item=state.action.steps, successaction=state.action,
                            param2=minetest.dir_to_facedir({x=-state.action.dir.x,y=0,z=-state.action.dir.z}, false)}
                    return false
                elseif dignode.name ~= state.action.steps then
                    state.action = {"dig", pos=thispos, successaction=state.action}
                    return false
                end

            elseif y == 2 and x ~= 0 and state.action.lighting and special_light then

                -- We don't actually place lighting (e.g. torches) here,
                -- because we do walls later and that would disturb them.
                -- But we need to make sure we don't remove existing ones.
                if dignode.name ~= "air" and
                            dignode.name ~= state.action.lighting then
                    state.action = {"dig", pos=thispos, successaction=state.action}
                    return false
                end

            elseif y == height and state.action.support_top and special_sup then

                if dignode.name == "air" then
                    state.action = {"place", pos=thispos, item=state.action.support_top, successaction=state.action}
                    return false
                elseif dignode.name ~= state.action.support_top then
                    state.action = {"dig", pos=thispos, successaction=state.action}
                    return false
                end

            elseif x ~= 0 and state.action.support_side and special_sup then

                if dignode.name == "air" then
                    local param2
                    if state.action.support_side_facein then
                        local facevec = rotate({x=-x, y=0, z=0},
                            state.action.dir)
                        if facevec.x > 0 then
                            param2 = 4 * 4
                        elseif facevec.x < 0 then
                            param2 = 4 * 3
                        elseif facevec.z > 0 then
                            param2 = 4 * 2
                        else
                            param2 = 4 * 1
                        end
                    end
                    state.action = {"place", pos=thispos,
                        item=state.action.support_side,
                        successaction=state.action,
                        param2=param2}
                    return false
                elseif dignode.name ~= state.action.support_side then
                    state.action = {"dig", pos=thispos, successaction=state.action}
                    return false
                end

            else

                if dignode.name ~= "air" then
                    state.action = {"dig", pos=thispos, successaction=state.action}
                    return false
                end

            end

        end
    end

    if state.action.floor and state.action.dir.y == 0 then
        for x = -1, 1 do
            local thisoff = {x=0, y=-1, z=0}
            thisoff[relxaxis] = x
            local thispos = vector.add(digpos, thisoff)
            local dignode = minetest.get_node(thispos)
            if dignode.name == "air" then
                state.action = {"place", pos=thispos, item=state.action.floor, successaction=state.action}
                return false
            elseif dignode.name ~= state.action.floor then
                state.action = {"dig", pos=thispos, successaction=state.action}
                return false
            end
        end

    end

    local wall = state.action.wall
    if special_sup and state.action.support_wall then
        wall = state.action.support_wall
    end

    if wall then
        for y = 0, height + 1 do
            local thisoff = {x=0, y=y, z=0}
            for x = -2, 2, 4 do
                thisoff[relxaxis] = x
                local thispos = vector.add(digpos, thisoff)
                local dignode = minetest.get_node(thispos)
                if dignode.name == "air" then
                    state.action = {"place", pos=thispos, item=wall, successaction=state.action}
                    return false
                elseif dignode.name ~= wall then
                    state.action = {"dig", pos=thispos, successaction=state.action}
                    return false
                end
            end
        end
    end

    if state.action.lighting and special_light then
        local thisoff = {x=0, y=2, z=0}
        for x = -1, 1, 2 do
            thisoff[relxaxis] = x
            local thispos = vector.add(digpos, thisoff)
            local dignode = minetest.get_node(thispos)
            if dignode.name ~= state.action.lighting then
                local againstdir = {x=0, y=0, z=0}
                againstdir[relxaxis] = x
                state.action = {"place", pos=thispos, item=state.action.lighting, successaction=state.action,
                    againstdir=againstdir}
                return false
            end
        end

    end

    local ceiling = state.action.ceiling
    if special_sup and state.action.support_ceiling then
        ceiling = state.action.support_ceiling
    end

    if ceiling then
        -- We need to place the ceiling nodes against something - we use
        -- the walls.
        local againstdir = {x=0, y=0, z=0}
        againstdir[relxaxis] = -1
        for x = -1, 1 do
            local thisoff = {x=0, y=height+1, z=0}
            thisoff[relxaxis] = x
            local thispos = vector.add(digpos, thisoff)
            local dignode = minetest.get_node(thispos)
            if dignode.name == "air" then
                state.action = {"place", pos=thispos, item=ceiling, successaction=state.action,
                    againstdir=againstdir}
                return false
            elseif dignode.name ~= ceiling then
                state.action = {"dig", pos=thispos, successaction=state.action}
                return false
            end
        end
    end

    -- We've cleared the cross-section at the next position, so we can move
    -- forward a step...
    state.action.distance = state.action.distance - 1
    state.action = {"go", pos=digpos, successaction=state.action}

    return false

end