local events = require "util.events";
local cache = require "util.cache";

local service_mt = {};

local default_config = {
	itemstore = function (config, _) return cache.new(config["max_items"]) end;
	broadcaster = function () end;
	itemcheck = function () return true; end;
	get_affiliation = function () end;
	normalize_jid = function (jid) return jid; end;
	capabilities = {};
};
local default_config_mt = { __index = default_config };

local default_node_config = {
	["persist_items"] = false;
	["max_items"] = 20;
	["access_model"] = "open";
};
local default_node_config_mt = { __index = default_node_config };

-- Storage helper functions

local function load_node_from_store(service, node_name)
	local node = service.config.nodestore:get(node_name);
	node.config = setmetatable(node.config or {}, {__index=service.node_defaults});
	return node;
end

local function save_node_to_store(service, node)
	return service.config.nodestore:set(node.name, {
		name = node.name;
		config = node.config;
		subscribers = node.subscribers;
		affiliations = node.affiliations;
	});
end

local function delete_node_in_store(service, node_name)
	return service.config.nodestore:set(node_name, nil);
end

-- Create and return a new service object
local function new(config)
	config = config or {};

	local service = setmetatable({
		config = setmetatable(config, default_config_mt);
		node_defaults = setmetatable(config.node_defaults or {}, default_node_config_mt);
		affiliations = {};
		subscriptions = {};
		nodes = {};
		data = {};
		events = events.new();
	}, service_mt);

	-- Load nodes from storage, if we have a store and it supports iterating over stored items
	if config.nodestore and config.nodestore.users then
		for node_name in config.nodestore:users() do
			service.nodes[node_name] = load_node_from_store(service, node_name);
			service.data[node_name] = config.itemstore(service.nodes[node_name].config, node_name);
		end
	end

	return service;
end

--- Service methods

local service = {};
service_mt.__index = service;

function service:jids_equal(jid1, jid2)
	local normalize = self.config.normalize_jid;
	return normalize(jid1) == normalize(jid2);
end

function service:may(node, actor, action)
	if actor == true then return true; end

	local node_obj = self.nodes[node];
	local node_aff = node_obj and (node_obj.affiliations[actor]
	              or node_obj.affiliations[self.config.normalize_jid(actor)]);
	local service_aff = self.affiliations[actor]
	                 or self.config.get_affiliation(actor, node, action);
	local default_aff = self:get_default_affiliation(node, actor) or "none";

	-- Check if node allows/forbids it
	local node_capabilities = node_obj and node_obj.capabilities;
	if node_capabilities then
		local caps = node_capabilities[node_aff or service_aff or default_aff];
		if caps then
			local can = caps[action];
			if can ~= nil then
				return can;
			end
		end
	end

	-- Check service-wide capabilities instead
	local service_capabilities = self.config.capabilities;
	local caps = service_capabilities[node_aff or service_aff or default_aff];
	if caps then
		local can = caps[action];
		if can ~= nil then
			return can;
		end
	end

	return false;
end

function service:get_default_affiliation(node, actor, action) -- luacheck: ignore 212
	local node_obj = self.nodes[node];
	local access_model = node_obj and node_obj.config.access_model
		or self.node_defaults.access_model;

	if access_model == "open" then
		return "none";
	elseif access_model == "whitelist" then
		return "restricted";
	end

	if self.config.access_models then
		local check = self.config.access_models[access_model];
		if check then
			local aff = check(actor);
			if aff then
				return aff;
			end
		end
	end
end

function service:set_affiliation(node, actor, jid, affiliation)
	-- Access checking
	if not self:may(node, actor, "set_affiliation") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	jid = self.config.normalize_jid(jid);
	local old_affiliation = node_obj.affiliations[jid];
	node_obj.affiliations[jid] = affiliation;

	if self.config.nodestore then
		local ok, err = save_node_to_store(self, node_obj);
		if not ok then
			node_obj.affiliations[jid] = old_affiliation;
			return ok, "internal-server-error";
		end
	end

	local _, jid_sub = self:get_subscription(node, true, jid);
	if not jid_sub and not self:may(node, jid, "be_unsubscribed") then
		local ok, err = self:add_subscription(node, true, jid);
		if not ok then
			return ok, err;
		end
	elseif jid_sub and not self:may(node, jid, "be_subscribed") then
		local ok, err = self:add_subscription(node, true, jid);
		if not ok then
			return ok, err;
		end
	end
	return true;
end

function service:add_subscription(node, actor, jid, options)
	-- Access checking
	local cap;
	if actor == true or jid == actor or self:jids_equal(actor, jid) then
		cap = "subscribe";
	else
		cap = "subscribe_other";
	end
	if not self:may(node, actor, cap) then
		return false, "forbidden";
	end
	if not self:may(node, jid, "be_subscribed") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		if not self.config.autocreate_on_subscribe then
			return false, "item-not-found";
		else
			local ok, err = self:create(node, true);
			if not ok then
				return ok, err;
			end
			node_obj = self.nodes[node];
		end
	end
	local old_subscription = node_obj.subscribers[jid];
	node_obj.subscribers[jid] = options or true;
	local normal_jid = self.config.normalize_jid(jid);
	local subs = self.subscriptions[normal_jid];
	if subs then
		if not subs[jid] then
			subs[jid] = { [node] = true };
		else
			subs[jid][node] = true;
		end
	else
		self.subscriptions[normal_jid] = { [jid] = { [node] = true } };
	end

	if self.config.nodestore then
		local ok, err = save_node_to_store(self, node_obj);
		if not ok then
			node_obj.subscribers[jid] = old_subscription;
			self.subscriptions[normal_jid][jid][node] = old_subscription and true or nil;
			return ok, "internal-server-error";
		end
	end

	self.events.fire_event("subscription-added", { node = node, jid = jid, normalized_jid = normal_jid, options = options });
	return true;
end

function service:remove_subscription(node, actor, jid)
	-- Access checking
	local cap;
	if actor == true or jid == actor or self:jids_equal(actor, jid) then
		cap = "unsubscribe";
	else
		cap = "unsubscribe_other";
	end
	if not self:may(node, actor, cap) then
		return false, "forbidden";
	end
	if not self:may(node, jid, "be_unsubscribed") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	if not node_obj.subscribers[jid] then
		return false, "not-subscribed";
	end
	local old_subscription = node_obj.subscribers[jid];
	node_obj.subscribers[jid] = nil;
	local normal_jid = self.config.normalize_jid(jid);
	local subs = self.subscriptions[normal_jid];
	if subs then
		local jid_subs = subs[jid];
		if jid_subs then
			jid_subs[node] = nil;
			if next(jid_subs) == nil then
				subs[jid] = nil;
			end
		end
		if next(subs) == nil then
			self.subscriptions[normal_jid] = nil;
		end
	end

	if self.config.nodestore then
		local ok, err = save_node_to_store(self, node_obj);
		if not ok then
			node_obj.subscribers[jid] = old_subscription;
			self.subscriptions[normal_jid][jid][node] = old_subscription and true or nil;
			return ok, "internal-server-error";
		end
	end

	self.events.fire_event("subscription-removed", { node = node, jid = jid, normalized_jid = normal_jid });
	return true;
end

function service:get_subscription(node, actor, jid)
	-- Access checking
	local cap;
	if actor == true or jid == actor or self:jids_equal(actor, jid) then
		cap = "get_subscription";
	else
		cap = "get_subscription_other";
	end
	if not self:may(node, actor, cap) then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	return true, node_obj.subscribers[jid];
end

function service:create(node, actor, options)
	-- Access checking
	if not self:may(node, actor, "create") then
		return false, "forbidden";
	end
	--
	if self.nodes[node] then
		return false, "conflict";
	end

	self.nodes[node] = {
		name = node;
		subscribers = {};
		config = setmetatable(options or {}, {__index=self.node_defaults});
		affiliations = {};
	};

	if self.config.nodestore then
		local ok, err = save_node_to_store(self, self.nodes[node]);
		if not ok then
			self.nodes[node] = nil;
			return ok, "internal-server-error";
		end
	end

	self.data[node] = self.config.itemstore(self.nodes[node].config, node);
	self.events.fire_event("node-created", { node = node, actor = actor });
	if actor ~= true then
		local ok, err = self:set_affiliation(node, true, actor, "owner");
		if not ok then
			self.nodes[node] = nil;
			self.data[node] = nil;
			return ok, err;
		end
	end

	return true;
end

function service:delete(node, actor)
	-- Access checking
	if not self:may(node, actor, "delete") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	self.nodes[node] = nil;
	if self.data[node] and self.data[node].clear then
		self.data[node]:clear();
	end
	self.data[node] = nil;

	if self.config.nodestore then
		local ok, err = delete_node_in_store(self, node);
		if not ok then
			self.nodes[node] = nil;
			return ok, err;
		end
	end

	self.events.fire_event("node-deleted", { node = node, actor = actor });
	self.config.broadcaster("delete", node, node_obj.subscribers, nil, actor, node_obj, self);
	return true;
end

function service:publish(node, actor, id, item)
	-- Access checking
	if not self:may(node, actor, "publish") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		if not self.config.autocreate_on_publish then
			return false, "item-not-found";
		end
		local ok, err = self:create(node, true);
		if not ok then
			return ok, err;
		end
		node_obj = self.nodes[node];
	end
	if not self.config.itemcheck(item) then
		return nil, "internal-server-error";
	end
	local node_data = self.data[node];
	local ok = node_data:set(id, item);
	if not ok then
		return nil, "internal-server-error";
	end
	if type(ok) == "string" then id = ok; end
	self.events.fire_event("item-published", { node = node, actor = actor, id = id, item = item });
	self.config.broadcaster("items", node, node_obj.subscribers, item, actor, node_obj, self);
	return true;
end

function service:retract(node, actor, id, retract)
	-- Access checking
	if not self:may(node, actor, "retract") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if (not node_obj) or (not self.data[node]:get(id)) then
		return false, "item-not-found";
	end
	local ok = self.data[node]:set(id, nil);
	if not ok then
		return nil, "internal-server-error";
	end
	self.events.fire_event("item-retracted", { node = node, actor = actor, id = id });
	if retract then
		self.config.broadcaster("items", node, node_obj.subscribers, retract, actor, node_obj, self);
	end
	return true
end

function service:purge(node, actor, notify)
	-- Access checking
	if not self:may(node, actor, "retract") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	if self.data[node] and self.data[node].clear then
		self.data[node]:clear()
	else
		self.data[node] = self.config.itemstore(self.nodes[node].config, node);
	end
	self.events.fire_event("node-purged", { node = node, actor = actor });
	if notify then
		self.config.broadcaster("purge", node, node_obj.subscribers, nil, actor, node_obj, self);
	end
	return true
end

function service:get_items(node, actor, id)
	-- Access checking
	if not self:may(node, actor, "get_items") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	if id then -- Restrict results to a single specific item
		local with_id = self.data[node]:get(id);
		if not with_id then
			return true, { };
		end
		return true, { id, [id] = with_id };
	else
		local data = {}
		for key, value in self.data[node]:items() do
			data[#data+1] = key;
			data[key] = value;
		end
		return true, data;
	end
end

function service:get_last_item(node, actor)
	-- Access checking
	if not self:may(node, actor, "get_items") then
		return false, "forbidden";
	end
	--
	return true, self.data[node]:tail();
end

function service:get_nodes(actor)
	-- Access checking
	if not self:may(nil, actor, "get_nodes") then
		return false, "forbidden";
	end
	--
	return true, self.nodes;
end

local function flatten_subscriptions(ret, serv, subs, node, node_obj)
	for subscribed_jid, subscribed_nodes in pairs(subs) do
		if node then -- Return only subscriptions to this node
			if subscribed_nodes[node] then
				ret[#ret+1] = {
					node = node;
					jid = subscribed_jid;
					subscription = node_obj.subscribers[subscribed_jid];
				};
			end
		else -- Return subscriptions to all nodes
			local nodes = serv.nodes;
			for subscribed_node in pairs(subscribed_nodes) do
				ret[#ret+1] = {
					node = subscribed_node;
					jid = subscribed_jid;
					subscription = nodes[subscribed_node].subscribers[subscribed_jid];
				};
			end
		end
	end
end

function service:get_subscriptions(node, actor, jid)
	-- Access checking
	local cap;
	if actor == true or jid == actor or self:jids_equal(actor, jid) then
		cap = "get_subscriptions";
	else
		cap = "get_subscriptions_other";
	end
	if not self:may(node, actor, cap) then
		return false, "forbidden";
	end
	--
	local node_obj;
	if node then
		node_obj = self.nodes[node];
		if not node_obj then
			return false, "item-not-found";
		end
	end
	local ret = {};
	if jid == nil then
		for _, subs in pairs(self.subscriptions) do
			flatten_subscriptions(ret, self, subs, node, node_obj)
		end
		return true, ret;
	end
	local normal_jid = self.config.normalize_jid(jid);
	local subs = self.subscriptions[normal_jid];
	-- We return the subscription object from the node to save
	-- a get_subscription() call for each node.
	if subs then
		flatten_subscriptions(ret, self, subs, node, node_obj)
	end
	return true, ret;
end

-- Access models only affect 'none' affiliation caps, service/default access level...
function service:set_node_capabilities(node, actor, capabilities)
	-- Access checking
	if not self:may(node, actor, "configure") then
		return false, "forbidden";
	end
	--
	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end
	node_obj.capabilities = capabilities;
	return true;
end

function service:set_node_config(node, actor, new_config)
	if not self:may(node, actor, "configure") then
		return false, "forbidden";
	end

	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end

	setmetatable(new_config, {__index=self.node_defaults})

	if self.config.check_node_config then
		local ok = self.config.check_node_config(node, actor, new_config);
		if not ok then
			return false, "not-acceptable";
		end
	end

	local old_config = node_obj.config;
	node_obj.config = new_config;

	if self.config.nodestore then
		local ok, err = save_node_to_store(self, node_obj);
		if not ok then
			node_obj.config = old_config;
			return ok, "internal-server-error";
		end
	end

	if old_config["persist_items"] ~= node_obj.config["persist_items"] then
		self.data[node] = self.config.itemstore(self.nodes[node].config, node);
	elseif old_config["max_items"] ~= node_obj.config["max_items"] then
		self.data[node]:resize(self.nodes[node].config["max_items"]);
	end

	return true;
end

function service:get_node_config(node, actor)
	if not self:may(node, actor, "get_configuration") then
		return false, "forbidden";
	end

	local node_obj = self.nodes[node];
	if not node_obj then
		return false, "item-not-found";
	end

	local config_table = {};
	for k, v in pairs(default_node_config) do
		config_table[k] = v;
	end
	for k, v in pairs(node_obj.config) do
		config_table[k] = v;
	end

	return true, config_table;
end

return {
	new = new;
};