local shared = ...

local canvas_update_queue = {}

local function add_canvas_to_update_queue(canvas)
    for _, item in ipairs(canvas_update_queue) do
        if item == canvas then
            return
        end
    end
    table.insert(canvas_update_queue, canvas)
end

local CanvasEntity = {
    initial_properties = {
        visual = "upright_sprite",
        pointable = false,
        physical = false,
    },
}

local function validate_vec2(data)
    return type(data) == "table" and
        type(data.x) == "number" and
        type(data.y) == "number"
end
local function validate_vec3(data)
    return validate_vec2(data) and
        type(data.z) == "number"
end

local function validate_staticdata(data)
    return
        type(data) == "table" and
        -- allow canvases created with older versions of the mod
        (data.node_offset == nil or validate_vec3(data.node_offset)) and
        validate_vec2(data.size) and
        validate_vec2(data.bitmap_size) and
        type(data.bitmap) == "table" and
        #data.bitmap == data.bitmap_size.x * data.bitmap_size.y
end

function CanvasEntity:on_activate(staticdata)
    self.object:set_armor_groups({ immortal = 1 })

    -- https://github.com/minetest/minetest/blob/5.6.1/src/script/cpp_api/s_entity.cpp#L77-L104
    assert(type(staticdata) == "string")

    if staticdata ~= "" then
        local data = minetest.deserialize(staticdata)

        if not validate_staticdata(data) then
            -- This should never happen.
            local p = self.object:get_pos():to_string()
            self.object:remove()
            minetest.log("warning",
                "Removed ggraffiti:canvas entity at " .. p .. " in on_activate because of invalid staticdata")
            return
        end

        if data.node_offset then
            self.node_offset = vector.copy(data.node_offset) -- add metatable
        end
        self.size = data.size
        self.bitmap_size = data.bitmap_size
        self.bitmap = data.bitmap
        self:update_immediately()

        -- "Overwrite" other canvases in the same place.
        local rivals = minetest.get_objects_inside_radius(self.object:get_pos(), shared.EPSILON)
        for _, obj in ipairs(rivals) do
            if obj ~= self.object then
                local ent = obj:get_luaentity()
                if ent and ent.name == "ggraffiti:canvas" then
                    obj:remove()
                end
            end
        end
    end
end

function CanvasEntity:setup(node_pos, size, bitmap_size)
    self.node_offset = node_pos - self.object:get_pos()
    self.size = size
    self.bitmap_size = bitmap_size

    self.bitmap = {}
    for i = 1, self.bitmap_size.x * self.bitmap_size.y do
        self.bitmap[i] = shared.TRANSPARENT
    end
end

function CanvasEntity:update_later()
    add_canvas_to_update_queue(self)
end

function CanvasEntity:update_immediately()
    local png = minetest.encode_base64(
        minetest.encode_png(self.bitmap_size.x, self.bitmap_size.y, self.bitmap, 9)
    )
    self.object:set_properties({
        visual_size = vector.new(self.size.x, self.size.y, 0),
        textures = {
            "[png:" .. png,
            "[png:" .. png .. "^[transformFX",
            -- "ggraffiti_debug_coordinates.png^([png:" .. png .. "^[resize:128x128)",
            -- "ggraffiti_debug_coordinates.png^([png:" .. png .. "^[resize:128x128)^[transformFX",
        },
    })
end

function CanvasEntity:is_empty()
    for _, c in ipairs(self.bitmap) do
        if c ~= shared.TRANSPARENT then
            return false
        end
    end
    return true
end

function CanvasEntity:get_staticdata()
    return minetest.serialize({
        node_offset = self.node_offset,
        size = self.size,
        bitmap_size = self.bitmap_size,
        bitmap = self.bitmap,
    })
end

function CanvasEntity:get_node_pos()
    if self.node_offset then
        return (self.object:get_pos() + self.node_offset):apply(math.round)
    end
end

minetest.register_entity("ggraffiti:canvas", CanvasEntity)

function shared.update_canvases()
    for _, canvas in ipairs(canvas_update_queue) do
        -- This doesn't cause a crash if the canvas entity has been removed.
        canvas:update_immediately()
    end
    canvas_update_queue = {}
end

-- This already seems to cover all important cases.
-- I intentionally do not remove floating graffiti in on_activate, as I think
-- that this would only make the behavior even more inconsistent and thus even
-- more confusing.
minetest.register_on_dignode(function(pos)
    local objs = minetest.get_objects_in_area(
        pos - vector.new(4, 4, 4), -- arbitrary
        pos + vector.new(4, 4, 4)
    )
    for _, obj in ipairs(objs) do
        local ent = obj:get_luaentity()
        if ent and ent.name == "ggraffiti:canvas" then
            local node_pos = ent:get_node_pos()
            if pos == node_pos then -- fancy overloaded `==` operator
                obj:remove()
            end
        end
    end
end)
