minetest-envelopes/init.lua

local f = string.format

local has_canonical_name = minetest.get_modpath("canonical_name")

minetest.register_craftitem("envelopes:envelope_blank", {
    description = "Blank Envelope",
    inventory_image = "envelopes_envelope_blank.png",
    on_use = function(itemstack, user, pointed_thing)
        minetest.show_formspec(user:get_player_name(), "envelopes:input",
            "size[5.5,5.5]" ..
            "field[2,0.5;3.5,1;addressee;Addressee;]" ..
            "label[0,0;Write a letter]" ..
            "textarea[0.5,1.5;5,3;text;Text;]" ..
            "field[3,4.8;2.5,1;attn;Attn. (Optional);]" ..
            "button_exit[0.25,4.5;2,1;exit;Seal]")
        return itemstack
    end
})

minetest.register_craftitem("envelopes:envelope_sealed", {
    description = "Sealed Envelope",
    inventory_image = "envelopes_envelope_sealed.png",
    stack_max = 1,
    groups = {not_in_creative_inventory = 1},
    on_use = function(itemstack, user, pointed_thing)
        local user_name = user:get_player_name()
        local meta = itemstack:get_meta()
        local addressee = meta:get_string("receiver")

        if has_canonical_name then
            addressee = canonical_name.get(addressee)
        end

        if user_name == addressee then
            local open_env = ItemStack("envelopes:envelope_opened")
            local open_meta = open_env:get_meta()
            open_meta:set_string("sender", meta:get_string("sender"))
            open_meta:set_string("receiver", meta:get_string("receiver"))
            open_meta:set_string("text", meta:get_string("text"))
            local desc = ("Opened Envelope\nTo: " .. meta:get_string("receiver") .. "\nFrom: "
                .. meta:get_string("sender"))
            open_meta:set_string("description", desc)
            if meta:get_string("attn") ~= "" then
                open_meta:set_string("attn", meta:get_string("attn"))
                desc = desc .. "\nAttn: " .. meta:get_string("attn")
                open_meta:set_string("description", desc)
            end
            return open_env

        else
            minetest.chat_send_player(user_name, f("The seal can only be opened by %s!", addressee))
            return itemstack
        end
    end
})

minetest.register_craftitem("envelopes:envelope_opened", {
    description = "Opened Envelope",
    inventory_image = "envelopes_envelope_opened.png",
    stack_max = 1,
    groups = {not_in_creative_inventory = 1},
    on_use = function(itemstack, user, pointed_thing)
        local meta = itemstack:get_meta()
        local sender = meta:get_string("sender")
        local receiver = meta:get_string("receiver")
        local text = meta:get_string("text")
        local attn = meta:get_string("attn") or ""
        local form =
            "size[5,5]" ..
            "label[0,0;A letter from " .. sender .. " to " .. receiver
        if attn ~= "" then
            form = form .. "\nAttn: " .. attn
        end
        form = form .. "\n" .. text .. "]" .. "button_exit[0,4;2,1;exit;Close]"
        minetest.show_formspec(user:get_player_name(), "envelope:display", form)
    end
})

minetest.register_on_player_receive_fields(function(player, formname, fields)
    if formname ~= "envelopes:input" or not minetest.is_player(player) then
        return false
    end

    local sender_name = player:get_player_name()

    local addressee = (fields.addressee or ""):trim()
    local text = (fields.text or ""):trim()
    local attn = (fields.attn or ""):trim()

    if addressee == "" or text == "" then
        minetest.chat_send_player(sender_name, "Please fill out all required fields.")
        return true
    end

    if has_canonical_name then
        addressee = canonical_name.get(addressee) or addressee
    end

    if not minetest.player_exists(addressee) then
        minetest.chat_send_player(sender_name, f("unknown addressee %q", addressee))
        return true
    end

    local inv = player:get_inventory()
    local letter = ItemStack("envelopes:envelope_sealed")
    local blank = ItemStack("envelopes:envelope_blank")
    local meta = letter:get_meta()

    meta:set_string("sender", sender_name)
    meta:set_string("receiver", addressee)
    meta:set_string("text", text)

    local desc = ("Sealed Envelope\nTo: " .. addressee .. "\nFrom: " .. sender_name)

    if attn ~= "" then
        meta:set_string("attn", attn)
        desc = desc .. "\nAttn: " .. attn
    end

    meta:set_string("description", desc)

    if inv:room_for_item("main", letter) and inv:contains_item("main", blank) then
        inv:add_item("main", letter)
        inv:remove_item("main", blank)
    else
        minetest.chat_send_player(sender_name, "Unable to create letter! Check your inventory space.")
    end

    return true
end)

if minetest.get_modpath("default") then
    minetest.register_craft({
        type = "shaped",
        output = "envelopes:envelope_blank 1",
        recipe = {
            {"", "", ""},
            {"default:paper", "default:paper", "default:paper"},
            {"default:paper", "default:paper", "default:paper"}
        }
    })
end