#define MAX_SANE_LAYERS 50

/// A datum tying together a greyscale configuration and dmi file. Required for using GAGS and handles the code interactions.
/datum/greyscale_config
	/// User friendly name used in the debug menu
	var/name

	/// Reference to the json config file
	var/json_config

	/// Reference to the dmi file for this config
	var/icon_file

	/// An optional var to set that tells the material system what material this configuration is for.
	/// Use a typepath here, not an instance.
	var/datum/material/material_skin

	///////////////////////////////////////////////////////////////////////////////////////////
	// Do not set any further vars, the json file specified above is what generates the object

	/// Spritesheet width of the icon_file
	var/width

	/// Spritesheet height of the icon_file
	var/height

	/// String path to the json file, used for reloading
	var/string_json_config

	/// The md5 file hash for the json configuration. Used to check if the file has changed
	var/json_config_hash

	/// String path to the icon file, used for reloading
	var/string_icon_file

	/// The md5 file hash for the icon file. Used to check if the file has changed
	var/icon_file_hash

	/// A list of icon states and their layers
	var/list/icon_states

	/// A list of all layers irrespective of nesting
	var/list/flat_all_layers

	/// A list of types to update in the world whenever a config changes
	var/list/live_edit_types

	/// How many colors are expected to be given when building the sprite
	var/expected_colors = 0

	/// Generated icons keyed by their color arguments
	var/list/icon_cache

// There's more sanity checking here than normal because this is designed for spriters to work with
// Sensible error messages that tell you exactly what's wrong is the best way to make this easy to use
/datum/greyscale_config/New()
	if(!json_config)
		stack_trace("Greyscale config object [DebugName()] is missing a json configuration, make sure `json_config` has been assigned a value.")
	string_json_config = "[json_config]"
	if(!icon_file)
		stack_trace("Greyscale config object [DebugName()] is missing an icon file, make sure `icon_file` has been assigned a value.")
	string_icon_file = "[icon_file]"
	if(!name)
		stack_trace("Greyscale config object [DebugName()] is missing a name, make sure `name` has been assigned a value.")

/datum/greyscale_config/Destroy(force, ...)
	if(!force)
		return QDEL_HINT_LETMELIVE
	return ..()

/datum/greyscale_config/process(delta_time)
	if(!Refresh(loadFromDisk=TRUE))
		return
	if(!live_edit_types)
		return
	for(var/atom/thing in world)
		if(live_edit_types[thing.type])
			thing.update_greyscale()

/datum/greyscale_config/proc/EnableAutoRefresh(live_type)
	message_admins("Config auto refresh has been enabled for '[live_type]' with configuration [DebugName()]. Expect heavy lag.")
	if(live_type)
		if(!live_edit_types)
			live_edit_types = list()
		live_edit_types += typecacheof(live_type)
	START_PROCESSING(SSgreyscale, src)

/datum/greyscale_config/proc/DisableAutoRefresh(live_type, remove_all=FALSE)
	if(!remove_all && !(live_type in live_edit_types))
		return
	message_admins("Config auto refresh has been disabled for '[live_type]' with configuration [DebugName()]")
	if(remove_all)
		live_edit_types = null
	else if(live_type && live_edit_types)
		live_edit_types -= typecacheof(live_type)
	if(!length(live_edit_types))
		live_edit_types = null
		STOP_PROCESSING(SSgreyscale, src)

/// Call this proc to handle all the data extraction from the json configuration. Can be forced to load values from disk instead of memory.
/datum/greyscale_config/proc/Refresh(loadFromDisk=FALSE)
	if(loadFromDisk)
		var/changed = FALSE

		json_config = file(string_json_config)
		var/json_hash = md5asfile(json_config)
		if(json_config_hash != json_hash)
			json_config_hash = json_hash
			changed = TRUE

		icon_file = file(string_icon_file)
		var/icon_hash = md5asfile(icon_file)
		if(icon_file_hash != icon_hash)
			icon_file_hash = icon_hash
			changed = TRUE

		for(var/datum/greyscale_layer/layer as anything in flat_all_layers)
			if(layer.DiskRefresh())
				changed = TRUE

		if(!changed)
			return FALSE

	var/list/raw = json_decode(file2text(json_config))
	ReadIconStateConfiguration(raw)

	if(!length(icon_states))
		CRASH("The json configuration [DebugName()] doesn't have any icon states.")

	icon_cache = list()

	ReadMetadata()

	SEND_SIGNAL(src, COMSIG_GREYSCALE_CONFIG_REFRESHED)

	return TRUE

/// Called after every config has refreshed, this proc handles data verification that depends on multiple entwined configurations.
/datum/greyscale_config/proc/CrossVerify()
	for(var/icon_state in icon_states)
		var/list/verification_targets = icon_states[icon_state]
		verification_targets = verification_targets.Copy()
		while(length(verification_targets))
			var/datum/greyscale_layer/layer = verification_targets[length(verification_targets)]
			verification_targets.len--
			if(islist(layer))
				verification_targets += layer
				continue
			layer.CrossVerify()

/// Gets the name used for debug purposes
/datum/greyscale_config/proc/DebugName()
	var/display_name = name || "MISSING_NAME"
	return "[display_name] ([icon_file]|[json_config])"

/// Takes the json icon state configuration and puts it into a more processed format.
/datum/greyscale_config/proc/ReadIconStateConfiguration(list/data)
	icon_states = list()
	for(var/state in data)
		var/list/raw_layers = data[state]
		if(!length(raw_layers))
			stack_trace("The json configuration [DebugName()] for icon state '[state]' is missing any layers.")
			continue
		if(icon_states[state])
			stack_trace("The json configuration [DebugName()] has a duplicate icon state '[state]' and is being overriden.")
		icon_states[state] = ReadLayersFromJson(raw_layers)

/// Takes the json layers configuration and puts it into a more processed format
/datum/greyscale_config/proc/ReadLayersFromJson(list/data)
	var/list/output = ReadLayerGroup(data)
	return output[1]

/datum/greyscale_config/proc/ReadLayerGroup(list/data)
	if(!islist(data[1]))
		var/layer_type = SSgreyscale.layer_types[data["type"]]
		if(!layer_type)
			CRASH("An unknown layer type was specified in the json of greyscale configuration [DebugName()]: [data["layer_type"]]")
		return new layer_type(icon_file, data.Copy()) // We don't want anything in there touching our version of the data
	var/list/output = list()
	for(var/list/group as anything in data)
		output += ReadLayerGroup(group)
	if(length(output)) // Adding lists to lists unwraps the top level so here we are
		output = list(output)
	return output

/// Reads layer configurations to take out some useful overall information
/datum/greyscale_config/proc/ReadMetadata()
	var/icon/source = icon(icon_file)
	height = source.Height()
	width = source.Width()

	var/list/datum/greyscale_layer/all_layers = list()
	for(var/state in icon_states)
		var/list/to_process = list(icon_states[state])
		var/list/state_layers = list()

		while(length(to_process))
			var/current = to_process[length(to_process)]
			to_process.len--
			if(islist(current))
				to_process += current
			else
				state_layers += current

		all_layers += state_layers

		if(length(state_layers) > MAX_SANE_LAYERS)
			stack_trace("[DebugName()] icon state '[state]' has [length(state_layers)] layers which is larger than the max of [MAX_SANE_LAYERS].")

	flat_all_layers = list()
	var/list/color_groups = list()
	var/largest_id = 0
	for(var/datum/greyscale_layer/layer as anything in all_layers)
		flat_all_layers += layer
		for(var/id in layer.color_ids)
			if(!isnum(id))
				continue
			largest_id = max(id, largest_id)
			color_groups["[id]"] = TRUE

	for(var/i in 1 to largest_id)
		if(color_groups["[i]"])
			continue
		stack_trace("Color Ids are required to be sequential and start from 1. [DebugName()] has a max id of [largest_id] but is missing [i].")

	expected_colors = length(color_groups)

/// For saving a dmi to disk, useful for debug mainly
/datum/greyscale_config/proc/SaveOutput(color_string)
	var/icon/icon_output = GenerateBundle(color_string)
	fcopy(icon_output, "tmp/gags_debug_output.dmi")

/// Actually create the icon and color it in, handles caching
/datum/greyscale_config/proc/Generate(color_string, icon/last_external_icon)
	var/key = color_string
	var/icon/new_icon = icon_cache[key]
	if(new_icon)
		return icon(new_icon)

	var/icon/icon_bundle = GenerateBundle(color_string, last_external_icon=last_external_icon)
	icon_bundle = fcopy_rsc(icon_bundle)
	icon_cache[key] = icon_bundle
	var/icon/output = icon(icon_bundle)
	return output

/// Handles the actual icon manipulation to create the spritesheet
/datum/greyscale_config/proc/GenerateBundle(list/colors, list/render_steps, icon/last_external_icon)
	if(!istype(colors))
		colors = SSgreyscale.ParseColorString(colors)
	if(length(colors) != expected_colors)
		CRASH("[DebugName()] expected [expected_colors] color arguments but only received [length(colors)]")

	var/list/generated_icons = list()
	for(var/icon_state in icon_states)
		var/list/icon_state_steps
		if(render_steps)
			icon_state_steps = render_steps[icon_state] = list()
		var/icon/generated_icon = GenerateLayerGroup(colors, icon_states[icon_state], icon_state_steps, last_external_icon)
		// We read a pixel to force the icon to be fully generated before we let it loose into the world
		// I hate this
		generated_icon.GetPixel(1, 1)
		generated_icons[icon_state] = generated_icon

	var/icon/icon_bundle = generated_icons[""] || icon('icons/testing/greyscale_error.dmi')
	icon_bundle.Scale(width, height)
	generated_icons -= ""

	for(var/icon_state in generated_icons)
		icon_bundle.Insert(generated_icons[icon_state], icon_state)

	return icon_bundle

/// Internal recursive proc to handle nested layer groups
/datum/greyscale_config/proc/GenerateLayerGroup(list/colors, list/group, list/render_steps, icon/last_external_icon)
	var/icon/new_icon
	for(var/datum/greyscale_layer/layer as anything in group)
		var/icon/layer_icon
		if(islist(layer))
			layer_icon = GenerateLayerGroup(colors, layer, render_steps, new_icon || last_external_icon)
			layer = layer[1] // When there are multiple layers in a group like this we use the first one's blend mode
		else
			layer_icon = layer.Generate(colors, render_steps, new_icon || last_external_icon)

		if(!new_icon)
			new_icon = layer_icon
		else
			new_icon.Blend(layer_icon, layer.blend_mode)

		// These are so we can see the result of every step of the process in the preview ui
		if(render_steps)
			var/list/icon_data = list()
			render_steps += list(icon_data)
			icon_data["config_name"] = name
			icon_data["step"] = icon(layer_icon)
			icon_data["result"] = icon(new_icon)
	return new_icon

/datum/greyscale_config/proc/GenerateDebug(colors)
	var/list/output = list()
	var/list/debug_steps = list()
	output["steps"] = debug_steps

	output["icon"] = GenerateBundle(colors, debug_steps)
	return output

#undef MAX_SANE_LAYERS