doc = {}

doc.VERSION = {}
doc.VERSION.MAJOR = 0
doc.VERSION.MINOR = 3
doc.VERSION.PATCH = 0
doc.VERSION.STRING = doc.VERSION.MAJOR.."."..doc.VERSION.MINOR.."."..doc.VERSION.PATCH


doc.data = {}
doc.data.categories = {}
doc.data.category_order = {}
doc.data.players = {}

-- Space for additional APIs
doc.sub = {}

--[[ Core API functions ]]

-- Add a new category
function doc.new_category(id, def)
	if doc.data.categories[id] == nil and id ~= nil then
		doc.data.categories[id] = {}
		doc.data.categories[id].entries = {}
		doc.data.categories[id].entry_count = 0
		doc.data.categories[id].def = def
		doc.data.categories[id].entry_aliases = {}
		table.insert(doc.data.category_order, id)
		return true
	else
		return false
	end
end

-- Add a new entry
function doc.new_entry(category_id, entry_id, def)
	if doc.data.categories[category_id] ~= nil then
		doc.data.categories[category_id].entries[entry_id] = def
		doc.data.categories[category_id].entry_count = doc.data.categories[category_id].entry_count + 1
		return true
	else
		return false
	end
end

-- Marks a particular entry as viewed by a certain player
function doc.mark_entry_as_viewed(playername, category_id, entry_id)
	if doc.data.players[playername].stored_data.viewed[category_id] == nil then
		doc.data.players[playername].stored_data.viewed[category_id] = {}
		doc.data.players[playername].stored_data.viewed_count[category_id] = 0
	end
	if doc.entry_exists(category_id, entry_id) and doc.data.players[playername].stored_data.viewed[category_id][entry_id] ~= true then
		doc.data.players[playername].stored_data.viewed[category_id][entry_id] = true
		doc.data.players[playername].stored_data.viewed_count[category_id] = doc.data.players[playername].stored_data.viewed_count[category_id] + 1
		-- Needed because viewed entries get a different color
		doc.data.players[playername].entry_textlist_needs_updating = true
	end
end

-- Returns true if the specified entry has been viewed by the player
function doc.entry_viewed(playername, category_id, entry_id)
	if doc.data.players[playername].stored_data.viewed[category_id] == nil then
		return false
	else
		return doc.data.players[playername].stored_data.viewed[category_id][entry_id] == true
	end
end

-- Opens the main documentation formspec for the player
function doc.show_doc(playername)
	if doc.get_category_count() <= 0 then
		minetest.show_formspec(playername, "doc:error_no_categories", doc.formspec_error_no_categories())
		return
	end
	local formspec = doc.formspec_core()..doc.formspec_main()
	minetest.show_formspec(playername, "doc:main", formspec)
end

-- Opens the documentation formspec for the player at the specified category
function doc.show_category(playername, category_id)
	if doc.get_category_count() <= 0 then
		minetest.show_formspec(playername, "doc:error_no_categories", doc.formspec_error_no_categories())
		return
	end
	doc.data.players[playername].catsel = nil
	doc.data.players[playername].category = category_id
	doc.data.players[playername].entry = nil
	local formspec = doc.formspec_core(2)..doc.formspec_category(category_id, playername)
	minetest.show_formspec(playername, "doc:category", formspec)
end

-- Opens the documentation formspec for the player showing the specified entry in a category
function doc.show_entry(playername, category_id, entry_id)
	if doc.get_category_count() <= 0 then
		minetest.show_formspec(playername, "doc:error_no_categories", doc.formspec_error_no_categories())
		return
	end
	doc.data.players[playername].catsel = nil
	doc.data.players[playername].category = category_id
	doc.data.players[playername].entry = entry_id
	doc.mark_entry_as_viewed(playername, category_id, entry_id)
	local formspec = doc.formspec_core(3)..doc.formspec_entry(category_id, entry_id)
	minetest.show_formspec(playername, "doc:entry", formspec)
end

-- Returns true if and only if:
-- * The specified category exists
-- * This category contains the specified entry
function doc.entry_exists(category_id, entry_id)
	if doc.data.categories[category_id] ~= nil then
		if doc.data.categories[category_id].entries[entry_id] ~= nil then
			-- Entry exists
			return true
		else
			-- Entry of this ID does not exist, so we check if there's an alis for it
			return doc.data.categories[category_id].entry_aliases[entry_id] ~= nil
		end
	else
		return false
	end
end

-- Adds aliases for an entry. Attempting to open an entry by an alias name
-- results in opening the entry of the original name.
-- Aliases are true within one category only.
function doc.add_entry_aliases(category_id, entry_id, aliases)
	for a=1,#aliases do
		doc.data.categories[category_id].entry_aliases[aliases[a]] = entry_id
	end
end

-- Same as above, but only adds one alias
function doc.add_entry_alias(category_id, entry_id, alias)
	doc.data.categories[category_id].entry_aliases[alias] = entry_id
end

-- Returns number of categories
function doc.get_category_count()
	return #doc.data.category_order
end

-- Returns number of entries in category
function doc.get_entry_count(category_id)
	return doc.data.categories[category_id].entry_count
end

-- Returns how many entries have been viewed by the player
function doc.get_viewed_count(playername, category_id)
	if doc.data.players[playername] == nil then
		return nil
	end
	local count = doc.data.players[playername].stored_data.viewed_count[category_id]
	if count == nil then
		return 0
	else
		return count
	end
end

-- Template function templates, to be used for build_formspec in doc.new_category
doc.entry_builders = {}

-- Freeform text
doc.entry_builders.text = function(data)
	return "textarea[0.25,0.5;12,8;;"..minetest.formspec_escape(data)..";]"
end

-- Direct formspec
doc.entry_builders.formspec = function(data)
	return data
end

--[[ Functions for internal use ]]

function doc.formspec_core(tab)
	if tab == nil then tab = 1 else tab = tostring(tab) end
	return "size[12,9]tabheader[0,0;doc_header;Category list,Entry list,Entry;"..tab..";true;false]"
end

function doc.formspec_main()
	local formstring = "label[0,0;This is the Documentation System, Version "..doc.VERSION.STRING..".\n"
	if doc.get_category_count() >= 1 then
		formstring = formstring .. "Please select a category you wish to learn more about:]"
		local y = 1
		for c=1,#doc.data.category_order do
			local id = doc.data.category_order[c]
			local data = doc.data.categories[id]
			-- Category buton
			local button = "button[0,"..y..";3,1;doc_button_category_"..id..";"..minetest.formspec_escape(data.def.name).."]"
			local tooltip = ""
			-- Optional description
			if data.def.description ~= nil then
			tooltip = "tooltip[doc_button_category_"..id..";"..minetest.formspec_escape(data.def.description).."]"
			end
			formstring = formstring .. button .. tooltip
			y = y + 1
		end
	end
	return formstring
end

function doc.formspec_error_no_categories()
	local formstring = "size[8,6]textarea[0.25,0;8,6;;"
	formstring = formstring .. minetest.formspec_escape(
[=[This is the Documentation System, Version ]=]..doc.VERSION.STRING..[=[.

ERROR: No help available.

No categories have been registered, but the Documentation System is useless without them.
The Documentation System does not come with help contents on its own, it needs additional mods to add help content.
Please make sure such mods are enabled on this server, and try again.]=])
	formstring = formstring .. ";]button_exit[3,5;2,1;okay;OK]"
	return formstring
end

function doc.generate_entry_list(cid, playername)
	local formstring
	if doc.data.players[playername].entry_textlist == nil
	or doc.data.players[playername].category ~= cid
	or doc.data.players[playername].entry_textlist_needs_updating == true then
		local entry_textlist = "textlist[0,1;11,7;doc_catlist;"
		local counter = 0
		doc.data.players[playername].entry_ids = {}
		local entries = doc.get_sorted_entry_names(cid)
		for i=1, #entries do
			local eid = entries[i].eid
			table.insert(doc.data.players[playername].entry_ids, eid)
			-- Colorize entries based on viewed status
			-- Not viewed: Cyan
			local viewedprefix = "#00FFFF"
			if doc.entry_viewed(playername, cid, eid) then
				-- Viewed: White
				viewedprefix = "#FFFFFF"
			end
			entry_textlist = entry_textlist .. viewedprefix .. minetest.formspec_escape(entries[i].name) .. ","
			counter = counter + 1
		end
		if counter >= 1  then
			entry_textlist = string.sub(entry_textlist, 1, #entry_textlist-1)
		end
		local catsel = doc.data.players[playername].catsel
		if catsel then
			entry_textlist = entry_textlist .. ";"..catsel
		end
		entry_textlist = entry_textlist .. "]"
		doc.data.players[playername].entry_textlist = entry_textlist
		formstring = entry_textlist
		doc.data.players[playername].entry_testlist_needs_updating = false
	else
		formstring = doc.data.players[playername].entry_textlist
	end
	return formstring
end

function doc.get_sorted_entry_names(cid)
	local sort_table = {}
	local entry_table = {}
	for eid,entry in pairs(doc.data.categories[cid].entries) do
		local new_entry = table.copy(entry)
		new_entry.eid = eid
		table.insert(entry_table, new_entry)
		table.insert(sort_table, entry.name)
	end
	table.sort(sort_table)
	local reverse_sort_table = table.copy(sort_table)
	for i=1, #sort_table do
		reverse_sort_table[sort_table[i]] = i
	end
	local comp = function(e1, e2)
		if reverse_sort_table[e1.name] < reverse_sort_table[e2.name] then return true else return false end
	end
	table.sort(entry_table, comp)

	return entry_table
end

function doc.formspec_category(id, playername)
	local formstring
	if id == nil then
		formstring = "label[0,0.5;You haven't chosen a category yet. Please choose one in the category list first.]"
		formstring = formstring .. "button[0,1.5;3,1;doc_button_goto_main;Go to category list]"
	else
		formstring = "label[0,0;Help > "..doc.data.categories[id].def.name.."]"
		if doc.get_entry_count(id) >= 1 then
			formstring = formstring .. "label[0,0.5;This category has the following entries:]"
			formstring = formstring .. doc.generate_entry_list(id, playername)
			formstring = formstring .. "button[0,8;3,1;doc_button_goto_entry;Show entry]"
			formstring = formstring .. "label[8,8;Number of entries: "..doc.get_entry_count(id).."\n"
			formstring = formstring .. "New entries: "..(doc.get_entry_count(id)-doc.get_viewed_count(playername, id)).."]"
		else
			formstring = formstring .. "label[0,0.5;This category is empty.]"
			formstring = formstring .. "button[0,1.5;3,1;doc_button_goto_main;Go to category list]"
		end
	end
	return formstring
end

function doc.formspec_entry(category_id, entry_id)
	local formstring
	if category_id == nil then
		formstring = "label[0,0;You haven't chosen a category yet. Please choose one in the category list first.]"
		formstring = formstring .. "button[0,1;3,1;doc_button_goto_main;Go to category list]"
	elseif entry_id == nil then
		formstring = "label[0,0;Help > "..doc.data.categories[category_id].def.name.." > (No Entry)]"
		if doc.get_entry_count(category_id) >= 1 then
			formstring = formstring .. "label[0,0.5;You haven't chosen an entry yet. Please choose one in the entry list first.]"
			formstring = formstring .. "button[0,1.5;3,1;doc_button_goto_category;Go to entry list]"
		else
			formstring = formstring .. "label[0,0.5;This category does not have any entries.]"
			formstring = formstring .. "button[0,1.5;3,1;doc_button_goto_main;Go to category list]"
		end
	else

		local category = doc.data.categories[category_id]
		local entry = category.entries[entry_id]
		-- Check if entry has an alias
		if entry == nil then
			local resolved_alias = doc.data.categories[category_id].entry_aliases[entry_id]
			if resolved_alias ~= nil then
				entry = category.entries[resolved_alias]
			end
		end

		formstring = "label[0,0;Help > "..category.def.name.." > "..entry.name.."]"
		formstring = formstring .. category.def.build_formspec(entry.data)
	end
	return formstring
end

function doc.process_form(player,formname,fields)
	local playername = player:get_player_name()
	--[[ process clicks on the tab header ]]
	if(formname == "doc:main" or formname == "doc:category" or formname == "doc:entry") then
		if fields.doc_header ~= nil then
			local tab = tonumber(fields.doc_header)
			local formspec, subformname, contents
			local cid, eid
			cid = doc.data.players[playername].category
			eid = doc.data.players[playername].entry
			if(tab==1) then
				contents = doc.formspec_main()
				subformname = "main"
			elseif(tab==2) then
				contents = doc.formspec_category(cid, playername)
				subformname = "category"
			elseif(tab==3) then
				contents = doc.formspec_entry(cid, eid)
				if cid ~= nil and eid ~= nil then
					doc.mark_entry_as_viewed(playername, cid, eid)
				end
				subformname = "entry"
			end
			formspec = doc.formspec_core(tab)..contents
			minetest.show_formspec(playername, "doc:" .. subformname, formspec)
			return
		end
	end
	if(formname == "doc:main") then
		for id,_ in pairs(doc.data.categories) do
			if fields["doc_button_category_"..id] then
				local formspec = doc.formspec_core(2)..doc.formspec_category(id, playername)
				doc.data.players[playername].catsel = nil
				doc.data.players[playername].category = id
				doc.data.players[playername].entry = nil
				minetest.show_formspec(playername, "doc:category", formspec)
				break
			end
		end
	elseif(formname == "doc:category") then
		if fields["doc_button_goto_entry"] then
			local cid = doc.data.players[playername].category
			if cid ~= nil then
				local eid = nil
				local eids, catsel = doc.data.players[playername].entry_ids, doc.data.players[playername].catsel
				if eids ~= nil and catsel ~= nil then
					eid = eids[catsel]
				end
				local formspec = doc.formspec_core(3)..doc.formspec_entry(cid, eid)
				minetest.show_formspec(playername, "doc:entry", formspec)
				doc.mark_entry_as_viewed(playername, cid, eid)
			end
		end
		if fields["doc_button_goto_main"] then
			local formspec = doc.formspec_core(1)..doc.formspec_main()
			minetest.show_formspec(playername, "doc:main", formspec)
		end
		if fields["doc_catlist"] then
			local event = minetest.explode_textlist_event(fields["doc_catlist"])
			if event.type == "CHG" then
				doc.data.players[playername].catsel = event.index
				doc.data.players[playername].entry = doc.data.players[playername].entry_ids[event.index]
			elseif event.type == "DCL" then
				local cid = doc.data.players[playername].category
				local eid = nil
				local eids, catsel = doc.data.players[playername].entry_ids, event.index
				if eids ~= nil and catsel ~= nil then
					eid = eids[catsel]
				end
				local formspec = doc.formspec_core(3)..doc.formspec_entry(cid, eid)
				minetest.show_formspec(playername, "doc:entry", formspec)
				doc.mark_entry_as_viewed(playername, cid, eid)
			end
		end
	elseif(formname == "doc:entry") then
		if fields["doc_button_goto_main"] then
			local formspec = doc.formspec_core(1)..doc.formspec_main()
			minetest.show_formspec(playername, "doc:main", formspec)
		elseif fields["doc_button_goto_category"] then
			local formspec = doc.formspec_core(2)..doc.formspec_category(doc.data.players[playername].category, playername)
			minetest.show_formspec(playername, "doc:category", formspec)
		end
	end
end

minetest.register_on_player_receive_fields(doc.process_form)

minetest.register_chatcommand("doc", {
	params = "",
	description = "Open documentation system.",
	privs = {},
	func = function(playername, param)
		doc.show_doc(playername)
	end,
	}
)

minetest.register_on_joinplayer(function(player)
	local playername = player:get_player_name()
	doc.data.players[playername] = {}
	-- Table for persistant data
	doc.data.players[playername].stored_data = {}
	-- Contains viewed entries
	doc.data.players[playername].stored_data.viewed = {}
	-- Count viewed entries
	doc.data.players[playername].stored_data.viewed_count = {}
end)

minetest.register_on_leaveplayer(function(player)
	doc.data.players[player:get_player_name()] = nil
end)

---[[ Add buttons for inventory mods ]]
-- Unified Inventory
if minetest.get_modpath("unified_inventory") ~= nil then
	unified_inventory.register_button("doc", {
		type = "image",
		image = "doc_button_icon_hires.png",
		tooltip = "Documentation System",
		action = function(player)
			doc.show_doc(player:get_player_name())
		end,
	})
end