add feature that scans chat for coords and allows navigating to it

Scan chat messages for coordinates and store N most recent.
Formspecs allows choosing one of the messages later and setting coords
to ones which were mentioned.

init.lua

@@ -274,24 +274,31 @@ local function coords_from_string(str)
     end
 end
 
+local _format_recent_dropbox -- defined later
 
 local function show_basic_dialog(itemstack, player)
     local meta = itemstack:get_meta()
-    -- set focus to "close" button to preven accidental edting
+    -- set focus to "close" button to prevent accidental edting
-    local formspec_head = "formspec_version[4]size[14,3]set_focus[close;]"
+    local formspec_head = "formspec_version[4]size[14,4]set_focus[close;]"
     local coords = coords_to_string(get_compass_meta_pos(meta))
     local field_coords = ("field[0.5,0.6;4,0.8;coords;Coordinates;%s]"):format(minetest.formspec_escape(coords))
     local label = get_compass_meta_label(meta) or "destination"
     local field_destination = ("field[4.5,0.6;7,0.8;label;Label;%s]"):format(minetest.formspec_escape(label))
     local color = ("%06X"):format(get_compass_meta_color(meta))
     local field_color = ("field[11.5,0.6;2.0,0.8;color;Color;%s]"):format(minetest.formspec_escape(color))
-    minetest.show_formspec(player:get_player_name(), "waypoint_compass:basic",
+    local dropdown_recent = ("dropdown[2.0,1.7;11.5,0.5;recent;%s;1,false]"):format(_format_recent_dropbox())
-                           formspec_head ..
+    local formspec = {
-                           field_coords ..
+        formspec_head,
-                           field_destination ..
+        field_coords,
-                           field_color ..
+        field_destination,
-                           "button_exit[3,1.7;3,0.8;save;save]" ..
+        field_color,
-                           "button_exit[8,1.7;3,0.8;close;close]")
+        "button_exit[0.5,1.7;1.5,0.5;set_recent;copy:]",
+        dropdown_recent,
+        "button_exit[3,2.7;3,0.8;save;save]",
+        "button_exit[8,2.7;3,0.8;close;close]"}
+    minetest.show_formspec(player:get_player_name(),
+                           "waypoint_compass:basic",
+                           table.concat(formspec, ""))
     local player_name = player:get_player_name()
     compass_dialog_context[player_name] = itemstack
 end
@@ -332,7 +339,7 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
     if formname ~= "waypoint_compass:basic" then
         return
     end
-    if fields.save or (fields.key_enter_field and fields.quit) then
+    if fields.save or fields.set_recent or (fields.key_enter_field and fields.quit) then
         local compass_item = compass_dialog_context[player:get_player_name()]
         if not compass_item then
             -- should not happen normally
@@ -351,6 +358,15 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
         end
         
         local coords = coords_from_string(fields.coords)
+        local label = fields.label
+
+        -- player pressed "copy" button, ignore the "coordinates field"
+        if fields.set_recent then
+            local coord_string = fields.recent:match("%S+") or ""
+            coords = coords_from_string(coord_string)
+            label = fields.recent:match("(%S+ |[^>]+)>") or ""
+        end
+
         if coords then
             set_compass_meta_pos(meta, coords)
         elseif fields.coords == "" then
@@ -359,7 +375,6 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
             -- TODO reset label too? or keep it to be safe?
         end
 
-        local label = fields.label
         set_compass_meta_label(meta, label)
 
         -- Prevent overwriting random item if user switched before
@@ -488,3 +503,57 @@ function waypoint_compass.make_compass(pos,owner_name, label, color)
 	return make_compass(pos,owner_name, label, color)
 end
 
+--------------------------------------------------------------------------------
+-- TODO move chat scanner into separate file, make enabling optional
+
+-- TODO API to add/rm "sticky" coordinates (that won't be pushed out of the list)?
+local last_coords_log = {}
+local last_coords_log_limit = 10 -- how many to keep
+
+local function add_coords_log(pos, playername, message)
+    table.insert(last_coords_log, 1, {pos=pos, playername=playername, message=message})
+    last_coords_log[last_coords_log_limit] = nil
+end
+
+
+-- Trying to mach any three integer numbers separated at least by
+-- spaces or punctuation.
+--local FUZZY_COORD_PATTERN = ".-(%d+)%D?[%s.,:;]%D?(%d+)%D?[%s.,:;]%D?(%d+)"
+local FUZZY_COORD_PATTERN = ".-(%d+)[^.%d]?[%s,:;]%D?(%d+)[^.%d]?[%s,:;]%D?(%d+)"
+
+
+-- "usafe" means it may throw errors, use pcall()
+local function fuzzy_parse_coords_unsafe(str)
+    -- find any 3 numbers in a string separated by punctuarion/spaces
+    local x,y,z = str:match(FUZZY_COORD_PATTERN)
+    x = clamp(tonumber(x), -32000, 32000)
+    y = clamp(tonumber(y), -32000, 32000)
+    z = clamp(tonumber(z), -32000, 32000)
+    return {x=x,y=y,z=z}
+end
+
+
+_format_recent_dropbox = function()
+    local out = {}
+    for k,v in ipairs(last_coords_log) do
+        local item = string.format("%d,%d,%d | %s> %s",
+                                   v.pos.x, v.pos.y, v.pos.z,
+                                   v.playername,
+                                   v.message:sub(1,50))
+        table.insert(out, minetest.formspec_escape(item))
+    end
+    return table.concat(out,",")
+end
+
+
+local function scan_chat_for_coords(name, message)
+    local success, coords = pcall(fuzzy_parse_coords_unsafe, message)
+    if success then
+        add_coords_log(coords, name, message)
+    end
+    return nil -- do not handle messages, just check them
+end
+
+
+minetest.register_on_chat_message(scan_chat_for_coords)
+