WIP simulated move

CONCEPT.md

@@ -3,6 +3,7 @@
 ## Progression
 
 - Assemble wooden contraption inside a rectangle of frames
+  - Move items with contraption
   - Rotate a contraption
   - Take a contraption to water
     - Use a shovel to propel a contraption on water

contraption.lua

@@ -102,10 +102,7 @@ end
 function contraption.find(pos)
     -- First check if the node at `pos` is a contraption block.
     for _, c in pairs(active_contraptions) do
-        if c.region:contains(pos) then
+        if c:get_node_data(pos) then return c end
-            local rel_pos = c.region:to_relative(pos)
-            if c.nodes[rel_pos:hash()] then return c end
-        end
     end
     return nil
 end
@@ -127,13 +124,13 @@ contraption.metatable = metatable
 function contraption.create(r)
     r = region.copy(r)
 
-    local nodes = {}
     local num_nodes = 0
-    for pos in r:iter_node_positions() do
+    local node_data = {}
-        local node = minetest.get_node(pos)
+    for abs_pos in r:iter_node_positions() do
+        local node = minetest.get_node(abs_pos)
         if nodecore.match(node, PLANK) then
-            local offset = r:to_relative(pos)
+            local rel_pos = r:to_relative(abs_pos)
-            nodes[offset:hash()] = CONTRAPTION_WOOD
+            node_data[rel_pos:hash()] = { rel_pos = rel_pos, node = CONTRAPTION_WOOD }
             num_nodes = num_nodes + 1
         end
     end
@@ -146,37 +143,33 @@ function contraption.create(r)
 
     -- TODO: Flood fill algorithm to make sure all nodes are connected.
 
+    -- Change nodes from base nodes to their contraption version.
+    for _, data in pairs(node_data) do
+        minetest.set_node(data.pos, data.node)
+    end
+
     id_counter = id_counter + 1
     local result = setmetatable({
         id        = id_counter,
         region    = r,
-        nodes = nodes,
         num_nodes = num_nodes,
+        node_data = node_data,
     }, metatable)
 
-    -- Change nodes from base nodes to their contraption version.
-    for pos_hash, node in pairs(nodes) do
-        local rel_pos = vector.from_hash(pos_hash)
-        local abs_pos = r:to_absolute(rel_pos)
-        minetest.set_node(abs_pos, node)
-    end
-
-    result:on_initialize()
     active_contraptions[result.id] = result
+    result:on_initialize()
     return result
 end
 
 function contraption:on_initialize()
-    local above_nodes = {}
-    for orig_pos_hash, node in pairs(self.nodes) do
-        local orig_pos = vector.from_hash(orig_pos_hash)
-
     -- Calculate the nodes above the contraption that it
     -- could potentially pull along with it as it moves.
-        local above_pos = orig_pos:offset(0, 1, 0)
+    local above_nodes = {}
-        if not self.nodes[above_pos:hash()] then
+    for pos_hash, data in pairs(self.node_data) do
+        local above_pos = data.pos:offset(0, 1, 0)
+        if not self:get_node_data(above_pos) then
             -- Non-contraption block above this one. Move items here along.
-            table_insert(above_nodes, above_pos)
+            above_nodes[pos_hash] = { pos = above_pos }
         end
     end
     self.above_nodes = above_nodes
@@ -190,11 +183,21 @@ function contraption.load_from_string(id, str)
         return nil
     end
 
+    -- TODO: Remove this temporary backward-compatibility.
+    obj.node_data = obj.node_data or obj.nodes
+
+    -- Recover "unnecessary" data.
+    obj.region = region.copy(obj.region)
+    for pos_hash, node in pairs(obj.node_data) do
+        local rel_pos = vector.from_hash(pos_hash)
+        obj.node_data[pos_hash] = { rel_pos = rel_pos, node = node }
+    end
+
     local result = setmetatable({
         id = id,
 
-        region    = region.copy(obj.region),
+        region    = obj.region,
-        nodes     = obj.nodes,
+        node_data = obj.node_data,
         num_nodes = obj.num_nodes,
 
         motion  = obj.motion  and vector.copy(obj.motion ) or nil,
@@ -207,12 +210,16 @@ function contraption.load_from_string(id, str)
 end
 
 function contraption:save_to_string()
+    local node_data = {} -- Clear out unnecessary data.
+    for pos_hash, data in pairs(self.node_data) do
+        node_data[pos_hash] = data.node end
+
     local to_save = {
         version = 1,
 
         region    = self.region,
-        nodes     = self.nodes,
         num_nodes = self.num_nodes,
+        node_data = node_data,
 
         motion  = self.motion,
         partial = self.partial,
@@ -223,25 +230,32 @@ end
 function contraption:destroy()
     active_contraptions[self.id] = nil
 
-    for pos_hash, node in pairs(self.nodes) do
+    for _, data in pairs(self.node_data) do
-        local rel_pos = vector.from_hash(pos_hash)
+        local def = minetest.registered_nodes[data.node.name]
-        local abs_pos = self.region:to_absolute(rel_pos)
+        minetest.set_node(data.pos, def.drop_in_place)
-        local def = minetest.registered_nodes[node.name]
-        minetest.set_node(abs_pos, def.drop_in_place)
     end
 end
 
+function contraption:get_node_data(pos, is_relative)
+    if not is_relative then pos = self.region:to_relative(pos) end
+    return self.node_data[pos:hash()]
+end
+
 function contraption:push(pusher, dir)
+    local can_move  = not not self:simulate_move(dir)
+    local has_moved = not not self:move(dir)
+    minetest.chat_send_all("can_move=" .. tostring(can_move) .. " :: has_moved=" .. tostring(has_moved))
+
     -- See if the same player has already pushed this contraption recently.
     -- If so, do not apply the full amount of motion from the push.
-    local pusher_name = pusher.get_player_name and pusher:get_player_name() or ""
+    -- local pusher_name = pusher.get_player_name and pusher:get_player_name() or ""
-    self.recent_pusher = self.recent_pusher or {}
+    -- self.recent_pusher = self.recent_pusher or {}
-    local delay = self.recent_pusher[pusher_name]
+    -- local delay = self.recent_pusher[pusher_name]
-    if delay then dir = dir * (1 - math.min(1, delay)) end
+    -- if delay then dir = dir * (1 - math.min(1, delay)) end
-    self.recent_pusher[pusher_name] = 1.0 -- seconds
+    -- self.recent_pusher[pusher_name] = 1.0 -- seconds
 
-    self.motion = self.motion or vector.zero()
+    -- self.motion = self.motion or vector.zero()
-    self.motion = self.motion + dir
+    -- self.motion = self.motion + dir
 end
 
 function contraption:update(delta_time)
@@ -325,6 +339,252 @@ function contraption:update(delta_time)
     end
 end
 
+function contraption:simulate_move(offset)
+    local success = true
+    local affected = {
+        -- [pos_hash] = {
+        --   type    = "fixed"   -- Part of the contraption, must move.
+        --          or "dragged" -- Dragged on top, may or may not move.
+        --          or "pushed"  -- Pushed in front, must move.
+        --          or "replace" -- Replaced by another node.
+        --          or "blocks"  -- Blocks movement of the contraption.
+        --   rel_pos = vector
+        --   abs_pos = vector
+        --   node    = node
+        --   meta    = true or nil
+        --   target  = <affected>
+        --   success = bool or nil when not calculated yet
+        -- }
+    }
+
+    for pos_hash, data in pairs(self.node_data) do
+        local abs_pos = self.region:to_absolute(data.rel_pos);
+        affected[pos_hash] = {
+            type    = "fixed",
+            rel_pos = data.rel_pos,
+            abs_pos = abs_pos,
+            node    = data.node,
+        }
+    end
+
+    for pos_hash, data in pairs(self.above_nodes) do
+        local abs_pos = self.region:to_absolute(data.rel_pos);
+        local node = minetest.get_node(data.abs_pos)
+        if contraption.is_pushable(node) then
+            affected[pos_hash] = {
+                type    = "dragged",
+                rel_pos = data.rel_pos,
+                abs_pos = abs_pos,
+                node    = node,
+                meta    = true,
+            }
+        end
+    end
+
+    -- Collect additional relevant nodes.
+    local newly_affected = {}
+    local function check_target(data)
+        local offset_rel_pos  = data.rel_pos + offset
+        local offset_abs_pos  = data.abs_pos + offset
+        local offset_pos_hash = offset_rel_pos:hash()
+
+        local target = affected[offset_pos_hash]
+        if target then
+            -- If the node ahead is "fixed" (part of the contraption),
+            -- then it has to be able to move for the whole to move.
+            -- We can consider this node to be able to move forward.
+            data.target = target
+            if target.type == "fixed" then
+                data.success = true
+            end
+        else
+            target = { rel_pos = offset_rel_pos, abs_pos = offset_abs_pos,
+                       node = minetest.get_node(offset_abs_pos) }
+            newly_affected[offset_pos_hash] = target
+            data.target = target
+
+            if data.type == "fixed" and contraption.is_pushable(target.node) then
+                target.type = "pushed"
+                target.meta = true
+                check_target(target)
+
+            -- Target node can be replaced, so do so.
+            elseif nodecore.buildable_to(target.node) then
+                target.type = "replace"
+                data.success = true
+
+            -- Target node blocks movement.
+            else
+                target.type = "blocks"
+                data.success = false
+                success = false
+            end
+        end
+    end
+    for _, data in pairs(affected) do check_target(data) end
+    for pos_hash, data in newly_affected do affected[pos_hash] = data
+
+
+    for _, data in pairs(affected) do
+        local offset_rel_pos  = data.rel_pos + offset
+        local offset_abs_pos  = data.abs.pos + offset
+        local offset_pos_hash = offset_rel_pos:hash()
+
+        data.target = affected[offset_pos_hash]
+
+        if data.target then
+            if data.target.type == "fixed" then
+                data.success = true
+            else
+                -- TODO: Need to check of the node in front can move.
+                --       Probably gonna add a set of nodes to check.
+            end
+        else
+            data.target = { rel_pos = offset_rel_pos, abs_pos = offset_abs_pos,
+                            node = minetest.get_node(offset_abs_pos) }
+            newly_affected[offset_pos_hash] = data.target
+
+            if data.type == "fixed" then
+                if contraption.is_pushable(data.target.node) then
+                    data.target.type = "pushed"
+
+                    offset_rel_pos  = offset_rel_pos + offset
+                    offset_abs_pos  = offset_abs_pos + offset
+                    offset_pos_hash = offset_rel_pos:hash()
+
+                    data.target.target = affected[offset_pos_hash]
+
+                    if data.target.target then
+                        if data.target.type == "fixed" then
+                            data.success = true
+                        end
+                    else
+                        data.target.target = { rel_pos = offset_rel_pos, abs_pos = offset_abs_pos,
+                                               node = minetest.get_node(offset_abs_pos) }
+                        newly_affected[offset_pos_hash] = data.target.target
+
+                        if nodecore.buildable_to(data.target.node) then
+                            data.target.type = "replace"
+                            data.success = true
+                        else
+                            data.target.type = "blocks"
+                            data.success = false
+                            success = false
+                        end
+                    end
+                end
+            end
+
+            if data.success == nil then
+
+            end
+        end
+    end
+
+    local function try_move(pos_hash, rel_pos, data, can_push)
+        local offset_rel_pos  = rel_pos  + offset
+        local offset_abs_pos  = data.pos + offset
+        local offset_pos_hash = offset_rel_pos:hash()
+        local offset_data
+
+        local result_entry = result[offset_pos_hash]
+        if result_entry then
+            -- `result` already has an entry at the offset position.
+            -- This means that node has already been checked and can move.
+            offset_data = result_entry.from
+
+        else
+            offset_data = { pos = offset_abs_pos }
+
+            local contraption_node = self.nodes[offset_pos_hash]
+            if contraption_node then
+                -- There's a contraption at the offset position.
+                -- If the whole can move, this node will be able to as well.
+                offset_data.node = contraption_node
+
+            else
+                local pushable_data = to_push[offset_pos_hash]
+                if pushable_data then
+                    -- Node is pushable and was going to be pushed anyway.
+
+                    -- TODO: Get rid of this nonsense.
+                    -- Node has already been processed by another pushable node.
+                    if pushable_data.can_move ~= nil then return pushable_data.can_move end
+
+                    offset_data = pushable_data
+                    local success = try_move(offset_pos_hash, offset_rel_pos, offset_data, false)
+                    if to_push_iterating then pushable_data.can_move = success
+                                        else to_push[offset_pos_hash] = nil end
+                    if not success then return false end
+
+                else
+                    offset_data.node = minetest.get_node(offset_abs_pos)
+
+                    if can_push and contraption.is_pushable(offset_data.node) then
+                        -- There's a pushable node in the way, so try to push it.
+                        -- Only one up to one node can be pushed this way.
+                        offset_data.meta = true -- Grab meta data for the pushed node later.
+                        if not try_move(offset_pos_hash, offset_rel_pos, offset_data, false) then return false end
+
+                    elseif nodecore.buildable_to(offset_data.node) then
+                        -- Offset node can be replaced by this one.
+
+                    else
+                        -- Bumped into something.
+                        return false
+                    end
+                end
+            end
+        end
+
+        -- Successfully moved, add to result.
+        result[pos_hash] = { from = data, to = offset_data }
+        return true
+    end
+
+    -- Attempt to move nodes that are part of the contraption.
+    -- If any of them can't be moved, the contraption can't move.
+    for pos_hash, node in pairs(self.nodes) do
+        local rel_pos = vector.from_hash(pos_hash)
+        local abs_pos = self.region:to_absolute(rel_pos)
+        local data = { pos = abs_pos, node = node }
+        if not try_move(pos_hash, rel_pos, data, true) then return nil end
+    end
+
+    -- `to_push` contains "lose" nodes that are not directly
+    -- moved by the contraption, and may or may not be pushed.
+    to_push_iterating = true
+    for pos_hash, pushable_data in pairs(to_push) do
+        if result[pos_hash] then
+            local rel_pos = vector.from_hash(pos_hash)
+            local data = { pos = pushable_data.abs_pos, node = pushable_data.node, meta = true }
+            pushable_data.can_move = try_move(pos_hash, rel_pos, data, false)
+        end
+    end
+
+    -- Fill in the meta for each entry where requested.
+    -- It's not needed until we know the contraption can move.
+    for _, data in pairs(result) do
+        if data.meta == true then
+            data.meta = minetest.get_meta(data.pos):to_table()
+        end
+    end
+
+    return result
+end
+
+function contraption.update_world(moved_nodes)
+    local to_set = {} -- Nodes to set because they have changed.
+
+    for pos_hash, data in pairs(moved_nodes) do
+        to_set[pos_hash] = { node = AIR }
+    end
+
+    for _, data in pairs(moved_nodes) do
+
+    end
+end
+
 function contraption:move(offset)
     -- Hash table of absolute positions before moved to nodes that have been moved by the
     -- contraption, either because they're part of it, or have been pushed as a result.
@@ -340,23 +600,13 @@ function contraption:move(offset)
 
     -- Assume that every node this contraption occupies needs to be cleared.
     -- We'll remove entries from `to_clear` when we know a node is moved there.
-    for pos_hash in pairs(self.nodes) do to_clear[pos_hash] = AIR end
+    for pos_hash in pairs(self.node_data) do to_clear[pos_hash] = AIR end
-
-    for _, rel_pos in ipairs(self.above_nodes) do
-        local abs_pos = self.region:to_absolute(rel_pos)
-        local node = minetest.get_node(abs_pos)
-        if contraption.is_pushable(node) then
-            to_push[rel_pos:hash()] = {
-                node = node,
-                meta = minetest.get_meta(abs_pos):to_table()
-            }
-        end
-    end
 
     -- TODO: Redo this loop to work similar to the `to_push` loop below.
-    for old_rel_pos_hash, node in pairs(self.nodes) do
+    for _, data in pairs(self.node_data) do
-        local old_rel_pos = vector.from_hash(old_rel_pos_hash)
+        local node        = data.node
-        local old_abs_pos = self.region:to_absolute(old_rel_pos)
+        local old_abs_pos = data.pos
+        local old_rel_pos = self.region:to_relative(old_abs_pos)
 
         local new_abs_pos = old_abs_pos + offset
         local new_rel_pos = old_rel_pos + offset
@@ -365,10 +615,10 @@ function contraption:move(offset)
         -- Node is being moved to this position, no need to clear here.
         to_clear[new_rel_pos_hash] = nil
 
-        local self_overlap = self.nodes[new_rel_pos_hash]
+        local self_overlap = self.node_data[new_rel_pos_hash]
         if self_overlap then
             moved_nodes[old_abs_pos:hash()] = { node = node }
-            if not nodecore.match(node, self_overlap) then
+            if not nodecore.match(node, self_overlap.node) then
                 table_insert(to_set, { pos = new_abs_pos, node = node })
             end
         else
@@ -394,7 +644,7 @@ function contraption:move(offset)
                         table_insert(to_set, nodecore.underride({ pos = new_abs_pos }, new_node))
                         to_push[new_rel_pos_hash] = nil
                         new_node = pushable
-                    elseif self.nodes[new_rel_pos_hash] then
+                    elseif self.node_data[new_rel_pos_hash] then
                         -- The next node is part of the contraption.
                         -- If it can move, this pushable node can move.
                         moved_nodes[old_abs_pos:hash()] = new_node
@@ -436,7 +686,7 @@ function contraption:move(offset)
 
         local forward_abs_pos = self.region:to_absolute(forward_rel_pos)
 
-        if self.nodes[forward_rel_pos] then
+        if self.node_data[forward_rel_pos] then
             -- Do not clear this node by the contraption moving.
             to_clear[forward_rel_pos] = nil
         else