--- Yet another badly designed and implemented GUI library, but this time I wrote it so it's the best.
-- Part of daccord. See daccord.can for more information.

-- Copyright 2017-2018 Étienne "Reuh" Fildadut
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

let curses = require("curses")
let class = require("classtoi")
let sleep = require("socket").sleep

let screen

os.setlocale("")

let everyWidget = {}

let widget = class {
	id = nil, -- (optional) widget id
	type = nil, -- widget type

	width = nil, -- height
	height = nil, -- width

	focused = false, -- true if take inputs

	updateInterval = -1, -- time in seconds between updates

	new = :(data) -- create a new widget
		table.insert(everyWidget, self)

		-- Copy properties
		for k, v in pairs(data) do
			@[k] = v
		end

		-- Dimensions
		if not @_parent._firstX then @_parent._firstX, @_parent._firstY = 0, 0 end
		@_x, @_y = @_parent._firstX, @_parent._firstY

		if     @width == "extend" @_w = @_parent._w - @_x
		elseif @width:match("%d+em$") @_w = tonumber(@width:match("%d+"))
		if     @height == "extend" then
			@_h = @_parent._h - @_y
			@_parent._lastVerticalExtend = self -- will be resized if vertical space is needed
			@_parent._afterLastVerticalExtend = {}
		elseif @height:match("%d+em$") @_h = tonumber(@height:match("%d+"))

		if @_y >= @_parent._h then -- resize
			@_parent._lastVerticalExtend:_resize(@_parent._lastVerticalExtend._w, @_parent._lastVerticalExtend._h - @_h)
			@_parent._firstY -= @_h
			@_y -= @_h
			for _, el in ipairs(@_parent._afterLastVerticalExtend) do -- move widgets
				el._y -= @_h
			end
		end

		@_parent._firstX += @_w
		if @_parent._firstX >= @_parent._w then @_parent._firstX = 0 end -- newline
		@_parent._firstY += @_h
		if @_parent._lastVerticalExtend ~= self and @_parent._afterLastVerticalExtend then table.insert(@_parent._afterLastVerticalExtend, self) end

		-- Setup
		if @_setup then @_setup() end

		screen:move(@_parent._y + @_y + @_h, @_parent._x + @_x + @_w)
	end,

	exit = :() -- exit the application
		@_exit = true
	end,

	byId = :(id) -- return a widget by its id
		for _, el in ipairs(everyWidget) do
			if el.id == id return el
		end
		error("no element with id "..tostring(id))
	end,

	updateAfter = :(time) -- reschedule the next widget update
		@_nextUpdate = os.time() + time
	end,

	_parent = {},

	_exit = false,

	_redraw = true,
	_x = 0,
	_y = 0,
	_w = 0,
	_h = 0,

	_nextUpdate = os.time(), -- -1 = no update
}

let widgets = setmetatable({
	fill = widget {
		fill = nil, -- filling type

		_draw = :()
			if type(@fill) == "string" then @fill = curses[@fill] end
			for y = @_parent._y + @_y, @_parent._y + @_y + @_h - 1 do
				screen:move(y, @_parent._x + @_x)
				for x = @_parent._x + @_x, @_parent._x + @_x + @_w - 1 do
					screen:addch(@fill or 32)
				end
			end
		end
	},

	input = widget {
		content = "", -- text content
		cursorPosition = 1, -- cursor position, first character is 1
		sub = :(start, stop=utf8.len(@content)) -- get the substring
			if stop < 1 or start >= utf8.len(@content) then
				return ""
			else
				return @content:sub(utf8.offset(@content, start), (utf8.offset(@content, stop+1) or (#@content+1))-1)
			end
		end,
		replace = :(start, stop, newText) -- replace a substring
			if @cursorPosition >= stop then
				@cursorPosition += utf8.len(newText) - (stop - start)
			end
			@content = @sub(1, start-1) .. newText .. @sub(stop+1)
			@onTextInput()
			@_redraw = true
		end,
		onTextInput = :() end, -- called when the text change

		_input = :(charbuffer, control)
			let y, x = @_parent._y + @_y, @_parent._x + @_x + @cursorPosition-1
			if control == "backspace" then
				screen:mvdelch(y, x-1)
				if @cursorPosition > 1 then
					if @cursorPosition == 2 then -- utf8.offset(s, 0) returns the start of the last character, ie something we don't want
						@content = @content:sub(utf8.offset(@content, @cursorPosition))
					else
						@content = @content:sub(1, utf8.offset(@content, @cursorPosition-1)-1)
									.. @content:sub(utf8.offset(@content, @cursorPosition))
					end
					@cursorPosition -= 1
					@onTextInput()
				end
			elseif control == "delete" then
				screen:mvdelch(y, x)
				if @cursorPosition <= utf8.len(@content) then
					if @cursorPosition == 1 then -- utf8.offset(s, 0) returns the start of the last character, ie something we don't want
						@content = @content:sub(utf8.offset(@content, @cursorPosition+1))
					else
						@content = @content:sub(1, utf8.offset(@content, @cursorPosition)-1)
									.. @content:sub(utf8.offset(@content, @cursorPosition+1))
					end
					@onTextInput()
				end
			elseif control == "right" then
				if @cursorPosition <= utf8.len(@content) then
					screen:addstr(@content:sub(utf8.offset(@content, @cursorPosition), utf8.offset(@content, @cursorPosition+1)-1))
					@cursorPosition += 1
				end
			elseif control == "left" then
				if @cursorPosition > 1 then
					screen:move(y, x-1)
					@cursorPosition -= 1
				end
			elseif charbuffer then
				screen:move(y, x)
				screen:winsstr(charbuffer)
				screen:move(y, x+1)
				@content = @content:sub(1, utf8.offset(@content, @cursorPosition)-1)
								.. charbuffer
								.. @content:sub(utf8.offset(@content, @cursorPosition))
				@cursorPosition += 1
				@onTextInput()
			end
		end,
		_draw = :()
			for y = @_parent._y + @_y, @_parent._y + @_y + @_h - 1 do
				screen:move(y, @_parent._x + @_x)
				for x = @_parent._x + @_x, @_parent._x + @_x + @_w - 1 do
					screen:addch(32)
				end
			end
			screen:mvaddstr(@_parent._y + @_y, @_parent._x + @_x, @content)
		end,
		_placeCursor = :()
			screen:move(@_parent._y + @_y, @_parent._x + @_x + @cursorPosition-1)
			return true
		end
	},

	list = widget {
		content = {}, -- list content (list of tables)
		selected = 1, -- last selected line
		pump = nil, -- function used to pump. See :setPump().
		insert = :(pos, item) -- insert a line, shifting elements after it
			if item then
				table.insert(@content, pos, item)
				if @selected > pos and @selected < #@content then
					@selected += 1
				end
			else
				item = pos
				table.insert(@content, item)
			end
			if #@content == 1 then -- column count is determined by 1st item (other items can do what they want, this isn't a dictatorship)
				@_columnWidth = [for _=1,#item do 0 end]
			end
			if #item >= #@_columnWidth then -- if the column fits into our dictatorship, update column width
				for c=1, #@_columnWidth do
					let l = utf8.len(item[c]) -- if it isn't valid UTF8, ignore (can happen for files in Windows-made zipfiles). Should probably raise a warning or something... TODO.
					if l and l > @_columnWidth[c] then
						@_columnWidth[c] = utf8.len(item[c]) + 1
					end
				end
			end
			@_redraw = true
		end,
		remove = :(pos=#@content) -- remove a line, shifting elements after it
			table.remove(@content, pos)
			if @selected > pos and @selected > 1 then
				@selected -= 1
			end
			@selected = math.min(@selected, #@content)
			@_redraw = true
		end,
		replace = :(pos, item) -- replace a line
			@content[pos] = item
			if #@content == 1 then -- column count is determined by 1st item (other items can do what they want, this isn't a dictatorship)
				@_columnWidth = [for _=1,#item do 0 end]
			end
			if #item >= #@_columnWidth then -- if the column fits into our dictatorship, update column width
				for c=1, #@_columnWidth do
					let l = utf8.len(item[c]) -- if it isn't valid UTF8, ignore (can happen for files in Windows-made zipfiles). Should probably raise a warning or something... TODO.
					if l and l > @_columnWidth[c] then
						@_columnWidth[c] = utf8.len(item[c]) + 1
					end
				end
			end
			@_redraw = true
		end,
		-- Give a pump function (startPosition, stopPosition) -> {tables...} which load the lines between startPosition and stopPosition.
		-- The pump may returns the lines instead of inserting them itself.
		-- step is the preferance of number of line to be loaded at one.
		setPump = :(step, newPump)
			@pump = newPump
			@_pumpStep = step
			if #@content == 0 then
				let pumped = @pump(1, math.max(@_h, @_pumpStep))
				if pumped then
					for _, l in ipairs(pumped) do
						@insert(l)
					end
				end
			end
		end,
		repump = :() -- force already pumped elements to be repumped. The rest of the list state will be kept.
			@content = {}
			@_columnWidth = {}
			let pumped = @pump(1, math.max(@_scroll+@_h, @_scroll+@_pumpStep)) -- TODO: change everything so we only need to pump what is currently displayed
			if pumped then
				for i, l in ipairs(pumped) do
					@replace(@_scroll+i-1, l)
				end
			end
		end,
		clear = :() -- reset list: content, current selection, current pump
			@content = {}
			@_columnWidth = {}
			@_redraw = true
			@selected = 1
			@_scroll = 0
			@pump = nil
		end,
		onSelect = :() end, -- called when selecting a line

		_columnWidth = {},
		_scroll = 0,
		_pumpStep = 5,
		_redraw = true,
		_input = :(charbuffer, control)
			if control == "up" then
				@selected -= 1
				@_redraw = true
			elseif control == "down" then
				@selected += 1
				@_redraw = true
			elseif control == "pgup" then
				@selected -= 10
				@_redraw = true
			elseif control == "pgdown" then
				@selected += 10
				@_redraw = true
			end

			if @pump and @selected > #@content then -- pump data if needed
				let pumped = @pump(#@content+1, #@content+@_pumpStep+1)
				if pumped then
					for _, l in ipairs(pumped) do
						@insert(l)
					end
				end
			end

			@selected = math.min(math.max(@selected, 1), math.max(#@content, 1))

			while @selected <= @_scroll do
				@_scroll -= 1
			end
			while @selected >= @_scroll + @_h + 1 do
				@_scroll += 1
			end

			if control == "enter" then
				@onSelect({@selected})
			elseif control == "A" then
				let len = #@content
				@onSelect([for i=1, len do i end])
			end
		end,
		_draw = :()
			let oY, oX = screen:getyx()
			for y = @_parent._y + @_y, @_parent._y + @_y + @_h -1 do -- clear
				screen:mvaddstr(y, @_parent._x + @_x, (" "):rep(@_w))
			end
			screen:move(@_parent._y + @_y, @_parent._x + @_x)
			for i=@_scroll+1, @_scroll + @_h do -- draw
				if i == @selected then
					screen:standout()
				end
				let colx = @_parent._x+@_x
				for c=1, #@_columnWidth do
					screen:mvaddstr(@_parent._y+@_y+i-1-@_scroll, colx, @content[i] and @content[i][c] or "") -- TODO: make sure it doesn't go too far right or something
					colx += @_columnWidth[c]
				end
				if i == @selected then
					screen:standend()
				end
			end
			screen:move(oY, oX)
		end
	},

	tabs = widget {
		selected = 1, -- selected tab
		children = {}, -- children elements

		_children = {},
		_setup = :()
			for i, tab in ipairs(@) do
				@children[i] = { _x = @_x, _y = @_y, _w = @_w, _h = @_h }
				for _, el in ipairs(tab) do
					el._parent = @children[i]
					table.insert(@children[i], widgets[el.type]:new(el))
				end
			end
			@_children = @children[@selected]
		end,
		_input = :(charbuffer, control)
			if control == "tab" then
				@selected += 1
				if @selected > #@ then @selected = 1 end
				@_children = @children[@selected]
				for _, el in ipairs(@_children) do -- Force redraw
					el._redraw = true
				end
			end
		end,
		_resize = :(w, h)
			@_w, @_h = w, h
			for i, tab in ipairs(@) do
				for _, el in ipairs(@children[i]) do
					if el._x + el._w > w then el._w = w - el._x end
					if el._y + el._h > h then el._h = h - el._y end
				end
			end
		end
	},

	label = widget {
		content = "Label", -- text
		set = :(str) -- set text
			@content = str
			@_redraw = true
		end,

		_draw = :()
			screen:mvaddstr(@_parent._y + @_y, @_parent._x + @_x, @content .. (" "):rep(@_w - #@content))
		end
	},

	slider = widget {
		min = 0, -- min value
		max = 1, -- max value
		value = 0, -- current value
		head = "⏸", -- associated symbol
		set = :(value) -- change value
			@value = value
			@_redraw = true
		end,
		setMax = :(max) -- change maximum
			@max = max
			@_redraw = true
		end,
		setMin = :(min) -- change minimum
			@min = min
			@_redraw = true
		end,
		setHead = :(head) -- change symbol
			@head = head
			@_redraw = true
		end,

		_draw = :()
			let len = math.ceil((@value - @min) / (@max - @min) * @_w)
			screen:mvaddstr(@_parent._y + @_y, @_parent._x + @_x, ("="):rep(len-1))
			screen:addstr(@head .. (" "):rep(@_w - len))
		end,
	}
}, {
	__index = (t, k)
		error("unknown widget "..tostring(k))
	end
})

let recursiveApply = (list, fn)
	for _, el in ipairs(list) do
		if el._widget then
			el = el._widget
		end
		fn(el)
		if el._children then
			recursiveApply(el._children, fn)
		end
	end
end

return (ui)
	xpcall(()
		-- Init
		if not screen then
			screen = curses.initscr()
			curses.cbreak()
			curses.echo(false)
			screen:nodelay(true)
		end

		-- Create widgets
		screen:clear()
		let h, w = screen:getmaxyx()
		let parent = {
			_x = 0, _y = 0,
			_w = w, _h = h
		}
		for _, el in ipairs(ui) do
			el._parent = parent
			el._widget = widgets[el.type]:new(el)
		end

		-- Update loop
		while not widget._exit do
			-- Input
			local c = screen:getch()
			if c and c < 256 then
				let charbuffer = string.char(c)
				let control
				if c > 127 then -- multibyte char
					charbuffer ..= string.char(screen:getch())
					if c > 223 then
						charbuffer ..= string.char(screen:getch())
						if c > 239 then
							charbuffer ..= string.char(screen:getch())
						end
					end
				end
				if curses.unctrl(c):match("^%^") then -- control char
					charbuffer = nil
					let k = curses.unctrl(c)
					if k == "^?" then
						control = "backspace"
					elseif k == "^W" then
						control = "close"
					elseif k == "^J" then
						control = "enter"
					elseif k == "^I" then
						control = "tab"
					elseif k == "^@" then
						control = "space"
					elseif k == "^[" then
						let k = string.char(screen:getch()) .. string.char(screen:getch())
						if k == "[C" then
							control = "right"
						elseif k == "[D" then
							control = "left"
						elseif k == "[A" then
							control = "up"
						elseif k == "[B" then
							control = "down"
						elseif k == "[5" then
							k ..= string.char(screen:getch())
							if k == "[5~" then
								control = "pgup"
							else
								error("unknown control "..tostring(k))
							end
						elseif k == "[6" then
							k ..= string.char(screen:getch())
							if k == "[6~" then
								control = "pgdown"
							else
								error("unknown control "..tostring(k))
							end
						elseif k == "[3" then
							k ..= string.char(screen:getch())
							if k == "[3~" then
								control = "delete"
							elseif k == "[3;" then
								control = "clear"
							else
								error("unknown control "..tostring(k))
							end
						else
							error("unknown control "..tostring(k))
						end
					elseif k:match("^%^[A-Z]$") then
						control = k:match("^%^([A-Z])$")
					else
						error("unknown control "..tostring(k))
					end
				end

				recursiveApply(ui, (el)
					if el.focused and el._input then
						el:_input(charbuffer, control)
					end
					if el.focused and control and el.onControl then
						el:onControl(control)
					end
				end)

				if control == "close" then
					if ui.onClose then ui.onClose(widget) end
				end
			end

			-- Update
			recursiveApply(ui, (el)
				if el._nextUpdate ~= -1 and os.difftime(el._nextUpdate, os.time()) <= 0 then
					if el.onUpdate then el:onUpdate() end
					if el.updateInterval ~= -1 then
						el._nextUpdate += el.updateInterval
					else
						el._nextUpdate = -1
					end
				end
			end)

			-- Redraw
			recursiveApply(ui, (el)
				if el._redraw and el._draw then
					el._redraw = false
					el:_draw()
				end
			end)

			-- Place cursor
			let cursorVis = 0
			recursiveApply(ui, (el)
				if el._placeCursor and el:_placeCursor() then
					cursorVis = 2
				end
			end)
			curses.curs_set(cursorVis)

			-- Done
			screen:refresh()
			sleep(0.03)
		end

		curses.endwin()
	end, (err)
	  curses.endwin()
	  print(require("candran").messageHandler(err))
	  os.exit(2)
	end)
end