local opts = {
	drag_to_pan_margin = 50,
	drag_to_pan_move_if_full_view = false,

	pan_follows_cursor_margin = 50,

	cursor_centric_zoom_margin = 50,
	cursor_centric_zoom_auto_center = true,
	cursor_centric_zoom_dezoom_if_full_view = false,
}
local options = require 'mp.options'
local msg = require 'mp.msg'
local assdraw = require 'mp.assdraw'

options.read_options(opts, nil, function() end)

function clamp(value, low, high)
	if value <= low then
		return low
	elseif value >= high then
		return high
	else
		return value
	end
end

local cleanup = nil -- function set up by drag-to-pan/pan-follows cursor and must be called to clean lingering state

function drag_to_pan_handler(table)
	if cleanup then
		cleanup()
		cleanup = nil
	end
	if table["event"] == "down" then
		local dim = mp.get_property_native("osd-dimensions")
		if not dim then return end
		local mouse_pos_origin, video_pan_origin = {}, {}
		local moved = false
		mouse_pos_origin[1], mouse_pos_origin[2] = mp.get_mouse_pos()
		video_pan_origin[1] = mp.get_property_number("video-pan-x")
		video_pan_origin[2] = mp.get_property_number("video-pan-y")
		local video_size = { dim.w - dim.ml - dim.mr, dim.h - dim.mt - dim.mb }
		local margin = opts.drag_to_pan_margin
		local move_up = true
		local move_lateral = true
		if not opts.drag_to_pan_move_if_full_view then
			if dim.ml >= 0 and dim.mr >= 0 then
				move_lateral = false
			end
			if dim.mt >= 0 and dim.mb >= 0 then
				move_up = false
			end
		end
		if not move_up and not move_lateral then return end
		local idle = function()
			if moved then
				local mX, mY = mp.get_mouse_pos()
				local pX = video_pan_origin[1]
				local pY = video_pan_origin[2]
				if move_lateral then
					pX = video_pan_origin[1] + (mX - mouse_pos_origin[1]) / video_size[1]
					if 2 * margin > dim.ml + dim.mr then
						pX = clamp(pX,
							(-margin + dim.w / 2) / video_size[1] - 0.5,
							(margin - dim.w / 2) / video_size[1] + 0.5)
					else
						pX = clamp(pX,
							(margin - dim.w / 2) / video_size[1] + 0.5,
							(-margin + dim.w / 2) / video_size[1] - 0.5)
					end
				end
				if move_up then
					pY = video_pan_origin[2] + (mY - mouse_pos_origin[2]) / video_size[2]
					if 2 * margin > dim.mt + dim.mb then
						pY = clamp(pY,
							(-margin + dim.h / 2) / video_size[2] - 0.5,
							(margin - dim.h / 2) / video_size[2] + 0.5)
					else
						pY = clamp(pY,
							(margin - dim.h / 2) / video_size[2] + 0.5,
							(-margin + dim.h / 2) / video_size[2] - 0.5)
					end
				end
				mp.command("no-osd set video-pan-x " .. clamp(pX, -3, 3) .. "; no-osd set video-pan-y " .. clamp(pY, -3, 3))
				moved = false
			end
		end
		mp.register_idle(idle)
		mp.add_forced_key_binding("mouse_move", "image-viewer-mouse-move", function() moved = true end)
		cleanup = function()
			mp.remove_key_binding("image-viewer-mouse-move")
			mp.unregister_idle(idle)
		end
	end
end

function pan_follows_cursor_handler(table)
	if cleanup then
		cleanup()
		cleanup = nil
	end
	if table["event"] == "down" then
		local dim = mp.get_property_native("osd-dimensions")
		if not dim then return end
		local video_size = { dim.w - dim.ml - dim.mr, dim.h - dim.mt - dim.mb }
		local moved = true
		local idle = function()
			if moved then
				local mX, mY = mp.get_mouse_pos()
				local x = math.min(1, math.max(-2 * mX / dim.w + 1, -1))
				local y = math.min(1, math.max(-2 * mY / dim.h + 1, -1))
				local command = ""
				local margin = opts.pan_follows_cursor_margin
				if dim.ml + dim.mr < 0 then
					command = command ..
						 "no-osd set video-pan-x " .. clamp(x * (2 * margin - dim.ml - dim.mr) / (2 * video_size[1]), -3, 3) .. ";"
				elseif mp.get_property_number("video-pan-x") ~= 0 then
					command = command .. "no-osd set video-pan-x " .. "0;"
				end
				if dim.mt + dim.mb < 0 then
					command = command ..
						 "no-osd set video-pan-y " .. clamp(y * (2 * margin - dim.mt - dim.mb) / (2 * video_size[2]), -3, 3) .. ";"
				elseif mp.get_property_number("video-pan-y") ~= 0 then
					command = command .. "no-osd set video-pan-y " .. "0;"
				end
				if command ~= "" then
					mp.command(command)
				end
				moved = false
			end
		end
		mp.register_idle(idle)
		mp.add_forced_key_binding("mouse_move", "image-viewer-mouse-move", function() moved = true end)
		cleanup = function()
			mp.remove_key_binding("image-viewer-mouse-move")
			mp.unregister_idle(idle)
		end
	end
end

function cursor_centric_zoom_handler(amt)
	local zoom_inc = tonumber(amt)
	if not zoom_inc or zoom_inc == 0 then return end
	local dim = mp.get_property_native("osd-dimensions")
	if not dim then return end

	local margin = opts.cursor_centric_zoom_margin

	local video_size = { dim.w - dim.ml - dim.mr, dim.h - dim.mt - dim.mb }

	-- the size in pixels of the (in|de)crement
	local diff_width  = (2 ^ zoom_inc - 1) * video_size[1]
	local diff_height = (2 ^ zoom_inc - 1) * video_size[2]
	if not opts.cursor_centric_zoom_dezoom_if_full_view and
		 zoom_inc < 0 and
		 video_size[1] + diff_width + 2 * margin <= dim.w and
		 video_size[2] + diff_height + 2 * margin <= dim.h
	then
		-- the zoom decrement is too much, reduce it such that the full image is visible, no more, no less
		-- in addition, this should take care of trying too zoom out while everything is already visible
		local new_zoom_inc_x = math.log((dim.w - 2 * margin) / video_size[1]) / math.log(2)
		local new_zoom_inc_y = math.log((dim.h - 2 * margin) / video_size[2]) / math.log(2)
		local new_zoom_inc   = math.min(0, math.min(new_zoom_inc_x, new_zoom_inc_y))
		zoom_inc             = new_zoom_inc
		diff_width           = (2 ^ zoom_inc - 1) * video_size[1]
		diff_height          = (2 ^ zoom_inc - 1) * video_size[2]
	end
	local new_width = video_size[1] + diff_width
	local new_height = video_size[2] + diff_height

	local mouse_pos_origin = {}
	mouse_pos_origin[1], mouse_pos_origin[2] = mp.get_mouse_pos()
	local new_pan_x, new_pan_y

	-- some additional constraints:
	-- if image can be fully visible (in either direction), set pan to 0
	-- if border would show on either side, then prefer adjusting the pan even if not cursor-centric
	local auto_c = opts.cursor_centric_zoom_auto_center
	if auto_c and video_size[1] + diff_width + 2 * margin <= dim.w then
		new_pan_x = 0
	else
		local pan_x = mp.get_property("video-pan-x")
		local rx = (dim.ml + video_size[1] / 2 - mouse_pos_origin[1]) / (video_size[1] / 2)
		new_pan_x = (pan_x * video_size[1] + rx * diff_width / 2) / new_width
		if auto_c then
			new_pan_x = clamp(new_pan_x, (dim.w - 2 * margin) / (2 * new_width) - 0.5,
				-(dim.w - 2 * margin) / (2 * new_width) + 0.5)
		end
	end

	if auto_c and video_size[2] + diff_height + 2 * margin <= dim.h then
		new_pan_y = 0
	else
		local pan_y = mp.get_property("video-pan-y")
		local ry = (dim.mt + video_size[2] / 2 - mouse_pos_origin[2]) / (video_size[2] / 2)
		new_pan_y = (pan_y * video_size[2] + ry * diff_height / 2) / new_height
		if auto_c then
			new_pan_y = clamp(new_pan_y, (dim.h - 2 * margin) / (2 * new_height) - 0.5,
				-(dim.h - 2 * margin) / (2 * new_height) + 0.5)
		end
	end

	local zoom_origin = mp.get_property("video-zoom")
	mp.command("no-osd set video-zoom " ..
		zoom_origin + zoom_inc ..
		"; no-osd set video-pan-x " .. clamp(new_pan_x, -3, 3) .. "; no-osd set video-pan-y " .. clamp(new_pan_y, -3, 3))
end

function align_border(x, y)
	local dim = mp.get_property_native("osd-dimensions")
	if not dim then return end
	local video_size = { dim.w - dim.ml - dim.mr, dim.h - dim.mt - dim.mb }
	local x, y = tonumber(x), tonumber(y)
	local command = ""
	if x then
		command = command .. "no-osd set video-pan-x " .. clamp(-x * (dim.ml + dim.mr) / (2 * video_size[1]), -3, 3) .. ";"
	end
	if y then
		command = command .. "no-osd set video-pan-y " .. clamp(-y * (dim.mt + dim.mb) / (2 * video_size[2]), -3, 3) .. ";"
	end
	if command ~= "" then
		mp.command(command)
	end
end

function pan_image(axis, amount, zoom_invariant, image_constrained)
	amount = tonumber(amount)
	if not amount or amount == 0 or axis ~= "x" and axis ~= "y" then return end
	if zoom_invariant == "yes" then
		amount = amount / 2 ^ mp.get_property_number("video-zoom")
	end
	local prop = "video-pan-" .. axis
	local old_pan = mp.get_property_number(prop)
	if image_constrained == "yes" then
		local dim = mp.get_property_native("osd-dimensions")
		if not dim then return end
		local margin =
		(axis == "x" and amount > 0) and dim.ml
			 or (axis == "x" and amount < 0) and dim.mr
			 or (amount > 0) and dim.mt
			 or (amount < 0) and dim.mb
		local vid_size = (axis == "x") and (dim.w - dim.ml - dim.mr) or (dim.h - dim.mt - dim.mb)
		local pixels_moved = math.abs(amount) * vid_size
		-- the margin is already visible, no point going further
		if margin >= 0 then
			return
		elseif margin + pixels_moved > 0 then
			amount = -(math.abs(amount) / amount) * margin / vid_size
		end
	end
	mp.set_property_number(prop, old_pan + amount)
end

function rotate_video(amt)
	local rot = mp.get_property_number("video-rotate")
	rot = (rot + amt) % 360
	mp.set_property_number("video-rotate", rot)
end

function reset_pan_if_visible()
	local dim = mp.get_property_native("osd-dimensions")
	if not dim then return end
	local command = ""
	if (dim.ml + dim.mr >= 0) then
		command = command .. "no-osd set video-pan-x 0" .. ";"
	end
	if (dim.mt + dim.mb >= 0) then
		command = command .. "no-osd set video-pan-y 0" .. ";"
	end
	if command ~= "" then
		mp.command(command)
	end
end

mp.add_key_binding(nil, "drag-to-pan", drag_to_pan_handler, { complex = true })
mp.add_key_binding(nil, "pan-follows-cursor", pan_follows_cursor_handler, { complex = true })
mp.add_key_binding(nil, "cursor-centric-zoom", cursor_centric_zoom_handler)
mp.add_key_binding(nil, "align-border", align_border)
mp.add_key_binding(nil, "pan-image", pan_image)
mp.add_key_binding(nil, "rotate-video", rotate_video)
mp.add_key_binding(nil, "reset-pan-if-visible", reset_pan_if_visible)
mp.add_key_binding(nil, "force-print-filename", force_print_filename)