local M = {}

M.core = require("libdiaphragm")

M.util = {}

function M.util.eprint(s, ...)
	io.stderr:write(string.format(s, ...))
	io.stderr:write("\n")
end

function M.util.list_concat(...)
	local result = {}
	for i = 1, select("#", ...) do
		local current = select(i, ...)
		if current ~= nil then
			for _, v in ipairs(current) do
				table.insert(result, v)
			end
		end
	end
	return result
end

function M.util.list_intersperse_with(func, list)
	local result = {}

	for i = 1, #list - 1 do
		table.insert(result, list[i])
		table.insert(result, func())
	end
	table.insert(result, list[#list])

	return result
end

function M.util.tbl_map(func, t)
	local result = {}
	for k, v in pairs(t) do
		result[k] = func(v)
	end
	return result
end

function M.util.tbl_print(t)
	io.stderr:write("{ ")
	for k, v in pairs(t) do
		io.stderr:write(string.format("%s = %s, ", k, v))
	end
	io.stderr:write("}\n")
end

function M.util.tbl_extend(...)
	local result = {}
	for i = 1, select("#", ...) do
		local current = select(i, ...)
		if current ~= nil then
			for k, v in pairs(current) do
				result[k] = v
			end
		end
	end
	return result
end

function M.util.tbl_contains(t, value)
	for _, v in pairs(t) do
		if v == value then
			return true
		end
	end
	return false
end

-- TODO: depending on objects
function M.util.is_reserved(s)
	return M.util.tbl_contains({
		"top",
		"left",
		"width",
		"height",
		"right",
		"bottom",
		"vert_center",
		"horiz_center",

		"top_left",
		"top_right",
		"bottom_left",
		"bottom_right",
		"middle_left",
		"middle_right",
		"top_middle",
		"bottom_middle",
		"center",

		"stroke_color",
		"stroke_width",
		"fill_color",

		-- "x",
		-- "y",
		--
		"size",
	}, s)
end

function M.util.tbl_filter_by_key(func, t)
	local result = {}
	for k, v in pairs(t) do
		if func(k) then
			result[k] = v
		end
	end
	return result
end

function M.util.tbl_filter_reserved(t)
	return M.util.tbl_filter_by_key(function(k)
		return not M.util.is_reserved(k)
	end, t)
end

function M.util.tbl_assign_reserved(t, rhs)
	for k, v in pairs(t) do
		if M.util.is_reserved(k) then
			rhs[k] = v
		end
	end
end

-- Return lhs, but with keys that are not in rhs
function M.util.tbl_diff(lhs, rhs)
	local result = {}
	for k, v in pairs(lhs) do
		if rhs[k] == nil then
			result[k] = v
		end
	end
	return result
end

-- Assign keys from lhs to rhs, useful if rhs is userdata
function M.util.tbl_assign(lhs, rhs)
	for k, v in pairs(lhs) do
		rhs[k] = v
	end
end

M.float = {}

M.float.new = M.core.float
M.float.max = M.core.float_max
M.float.min = M.core.float_min

M.text = {}
M.text.font = M.core.font

function M.text.new(params)
	params = params or {}
	local result = M.core.text(params)
	M.util.tbl_assign_reserved(params, result)
	return result
end

M.rectangle = {}

function M.rectangle.new(params)
	params = params or {}
	local result = M.core.rectangle()
	M.util.tbl_assign_reserved(params, result)
	return result
end

function M.rectangle.surrounding(content, params)
	local result = M.rectangle.new(params)
	M.constraint.inset(content, result, params)
	return result
end

M.straight_path = {}

function M.straight_path.new(params)
	params = params or {}
	local result = M.core.straight_path(params)
	M.util.tbl_assign_reserved(params, result)
	return result
end

function M.shape(params)
	params = params or {}
	local result = M.util.tbl_filter_reserved(params)

	local shape = M.core.complex_shape()
	setmetatable(result, {
		__index = function(_, k)
			if M.util.is_reserved(k) then
				return shape[k]
			end
		end,
	})
	M.util.tbl_assign_reserved(params, shape)

	return result
end

M.layout = {}

function M.layout.margin(params)
	local result = M.shape(params)

	result.margin_left = result.margin_left or M.float.new()
	result.margin_right = result.margin_right or M.float.new()
	result.margin_top = result.margin_top or M.float.new()
	result.margin_bottom = result.margin_bottom or M.float.new()

	function result:draw()
		M.constrain(self.left:eq(self.content.left - self.margin_left))
		M.constrain(self.right:eq(self.content.right + self.margin_right))
		M.constrain(self.top:eq(self.content.top - self.margin_top))
		M.constrain(self.bottom:eq(self.content.bottom + self.margin_bottom))

		self.content:draw()
	end

	return result
end

function M.layout.margin_left(params)
	return M.layout.margin(M.util.tbl_extend(params, {
		margin_right = 0,
		margin_top = 0,
		margin_bottom = 0,
	}))
end

function M.layout.margin_right(params)
	return M.layout.margin(M.util.tbl_extend(params, {
		margin_left = 0,
		margin_top = 0,
		margin_bottom = 0,
	}))
end

function M.layout.margin_top(params)
	return M.layout.margin(M.util.tbl_extend(params, {
		margin_left = 0,
		margin_right = 0,
		margin_bottom = 0,
	}))
end

function M.layout.margin_bottom(params)
	return M.layout.margin(M.util.tbl_extend(params, {
		margin_left = 0,
		margin_right = 0,
		margin_top = 0,
	}))
end

-- TODO: factor with vstack
-- TODO: also as just a set of constraints
-- TODO: add support for "growing" element height (or elements have same size)
-- TODO: add orientation (ltr or rtl)
function M.layout.hstack(params)
	local result = M.shape(params)

	result.spacing = result.spacing or 0
	result.align = result.align or "top"
	if result.align == "middle" or result.align == "center" then
		result.align = "vert_center"
	end

	function result:draw()
		local len = #self.elements
		assert(len >= 1, "hstack must have at least 1 element in `elements`")

		local tops = {}
		local bottoms = {}

		local previous_right = self.left - self.spacing
		local previous_vert_anchor = self[self.align]

		for _, el in pairs(self.elements) do
			local el_vert_anchor = el[self.align]

			M.constrain(el.left:eq(previous_right + self.spacing))
			M.constrain(el_vert_anchor:eq(previous_vert_anchor))

			table.insert(tops, el.top)
			table.insert(bottoms, el.bottom)

			el:draw()

			previous_right = el.right
			previous_vert_anchor = el_vert_anchor
		end

		M.constrain(self.top:eq(M.float.min(tops)))
		M.constrain(self.bottom:eq(M.float.max(bottoms)))
		M.constrain(self.right:eq(previous_right))
	end

	return result
end

function M.layout.vstack(params)
	local result = M.shape(params)

	result.spacing = result.spacing or 0
	result.align = result.align or "left"
	if result.align == "middle" or result.align == "center" then
		result.align = "horiz_center"
	end

	function result:draw()
		local len = #self.elements
		assert(len >= 1, "vstack must have at least 1 element in `elements`")

		local lefts = {}
		local rights = {}

		local previous_bottom = self.top - self.spacing
		local previous_horiz_anchor = self[self.align]

		for _, el in pairs(self.elements) do
			local el_horiz_anchor = el[self.align]

			M.constrain(el.top:eq(previous_bottom + self.spacing))
			M.constrain(el_horiz_anchor:eq(previous_horiz_anchor))

			table.insert(lefts, el.left)
			table.insert(rights, el.right)

			el:draw()

			previous_bottom = el.bottom
			previous_horiz_anchor = el_horiz_anchor
		end

		M.constrain(self.left:eq(M.float.min(lefts)))
		M.constrain(self.right:eq(M.float.max(rights)))
		M.constrain(self.bottom:eq(previous_bottom))
	end

	return result
end

M.constraint = {}

function M.constraint.left_of(lhs, rhs, margin)
	M.constrain(lhs.right:eq(rhs.left - (margin or 0)))
end

function M.constraint.right_of(rhs, lhs, margin)
	M.constrain(lhs.right:eq(rhs.left - (margin or 0)))
end

function M.constraint.above(above, below, margin)
	M.constrain(above.bottom:eq(below.top - (margin or 0)))
end

function M.constraint.below(below, above, margin)
	M.constrain(above.bottom:eq(below.top - (margin or 0)))
end

function M.constraint.same_size(elems)
	local height = M.float.new()
	local width = M.float.new()

	for _, el in pairs(elems) do
		M.constrain(el.height:eq(height))
		M.constrain(el.width:eq(width))
	end
end

function M.constraint.same_height(elems)
	local height = M.float.new()

	for _, el in pairs(elems) do
		M.constrain(el.height:eq(height))
	end
end

function M.constraint.same_width(elems)
	local width = M.float.new()

	for _, el in pairs(elems) do
		M.constrain(el.width:eq(width))
	end
end

-- TODO: factor with rectangle surrounding
function M.constraint.inset(child, parent, params)
	params = params or {}
	local margin = params.margin or 0
	local margin_left = params.margin_left or margin
	local margin_right = params.margin_right or margin
	local margin_top = params.margin_top or margin
	local margin_bottom = params.margin_bottom or margin

	M.constrain(parent.left:eq(child.left - margin_left))
	M.constrain(parent.right:eq(child.right + margin_right))
	M.constrain(parent.top:eq(child.top - margin_top))
	M.constrain(parent.bottom:eq(child.bottom + margin_bottom))
end

M.constrain = M.core.constrain
M.draw = function(params)
	M.core.draw(M.util.tbl_extend(params, {
		draw = function(figure)
			local self = M.shape({ left = 0, top = 0 })
			M.constraint.inset(self, figure)
			params.draw(self)
		end,
	}))
end

return M