--- @since 25.5.31

local DEFAULT_OPTIONS = {
	-- Can't reference Header.RIGHT etc. here (it hangs) so parent and align are strings
	-- 2000 puts it to the right of the indicator, and leaves some room between
	position = { parent = "Header", align = "RIGHT", order = 2000 },
	format = "both",
	bar = true,
	warning_threshold = 90,
	style_label = {
		fg = th.status.progress_label:fg(),
	},
	style_normal = {
		fg = th.status.progress_normal:fg(),
		bg = th.status.progress_normal:bg(),
	},
	style_warning = {
		fg = th.status.progress_error:fg(),
		bg = th.status.progress_error:bg(),
	},
	padding = { open = "", close = "" },
}

---Deep copy and merge two tables, overwriting values from one table into another
---@param from Table to take values from
---@param to Table to merge into
local function merge(into, from)
	-- Handle nil inputs
	into = into or {}
	from = from or {}

	local result = {}

	-- Deep copy 'into' first
	for k, v in pairs(into) do
		if type(v) == "table" then
			result[k] = merge({}, v)
		else
			result[k] = v
		end
	end

	-- Merge
	for k, v in pairs(from) do
		if type(v) == "table" then
			result[k] = merge(result[k], v)
		else
			result[k] = v
		end
	end

	return result
end

---Merge label and bar styles into left/right styles for the bar
---@param style_label Label style
---@param style_bar Usage bar style
local function build_styles(style_label, style_bar)
	local style_right = ui.Style():fg(style_label.fg or style_bar.fg):bg(style_bar.bg) -- Label bg is ignored
	if style_label.bold then
		style_right = style_right:bold()
	end
	if style_label.italic then
		style_right = style_right:italic()
	end

	-- Left style is the same as right, but with fg/bg reversed
	--  (this is overridden by the label colour if set)
	local style_left = ui.Style():patch(style_right):fg(style_label.fg or style_bar.bg):bg(style_bar.fg) -- Label bg is ignored

	return style_left, style_right
end

---Parse source and usage from df output
---@param stdout string df output
local function process_df_output(stdout)
	local source, usage = stdout:match(".*%s(%S+)%s+(%S+)")

	-- Follow symlinks in source
	if string.sub(source, 1, 1) == "/" then
		source = Command("readlink"):arg({ "--silent", "--canonicalize", "--no-newline", source }):output().stdout
	end

	-- Assume usage is a valid percentage
	-- Remove the percent and parse
	usage = tonumber(string.sub(usage, 1, #usage - 1))

	return source, usage
end

---Format text based on options
---@param source Source
---@param usage Usage
---@param format Format
local function format_text(source, usage, format)
	local text = ""
	if format == "both" then
		text = string.format("%s: %d%%", source, usage)
	elseif format == "name" then
		text = string.format("%s", source)
	elseif format == "usage" then
		text = string.format("%d%%", usage)
	end
	return text
end

---Set new plugin state and redraw
local set_state = ya.sync(function(st, source, usage, text, bar_len)
	st.source = source
	st.usage = usage
	st.text = text
	st.bar_len = bar_len

	local render = ui.render or ya.render
	render()
end)

---Get plugin state needed by entry
local get_state = ya.sync(function(st)
	return {
		-- Persistent options
		format = st.format,
		bar = st.bar,
		padding = st.padding,

		-- Variables
		source = st.source,
		usage = st.usage,
	}
end)

-- Called from init.lua
---@param st State
---@param opts Options
local function setup(st, opts)
	opts = merge(DEFAULT_OPTIONS, opts)

	-- Allow unsetting some options
	if opts.style_label.fg == "" then
		opts.style_label.fg = nil
	end
	if opts.warning_threshold < 0 then
		opts.warning_threshold = nil
	end

	-- Translate opts.position.parent option into a component reference
	if opts.position.parent == "Header" then
		opts.position.parent = Header
	elseif opts.position.parent == "Status" then
		opts.position.parent = Status
	else
		-- Just set it to nil, it's gonna cause errors anyway
		opts.position.parent = nil
	end

	-- Set persistent options
	local style_normal_left, style_normal_right = build_styles(opts.style_label, opts.style_normal)
	local style_warning_left, style_warning_right = build_styles(opts.style_label, opts.style_warning)
	st.style = {
		normal = {
			left = style_normal_left,
			right = style_normal_right,
			padding = {
				left = ui.Style():fg(style_normal_left:bg()),
				right = ui.Style():fg(style_normal_right:bg()),
			},
		},
		warning = {
			left = style_warning_left,
			right = style_warning_right,
			padding = {
				left = ui.Style():fg(style_warning_left:bg()),
				right = ui.Style():fg(style_warning_right:bg()),
			},
		},
	}
	st.format = opts.format
	st.bar = opts.bar
	st.warning_threshold = opts.warning_threshold
	st.padding = opts.padding

	-- Add the component to the parent
	opts.position.parent:children_add(function(self)
		-- No point showing anything if usage is nil
		if not st.usage then
			return
		end

		local style = (st.warning_threshold and st.usage >= st.warning_threshold) and st.style.warning
			or st.style.normal

		-- Apply styles to components based on the bar length, and ad them to the bar
		local output = {}
		local bar_len = st.bar_len
		local components = {
			{ text = st.padding.open, style = style.padding },
			{ text = st.text, style = style },
			{ text = st.padding.close, style = style.padding },
		}
		for _, component in ipairs(components) do
			-- bar_len_bytes should point to the last byte that should be coloured by the usage bar
			local bar_len_bytes
			if bar_len <= 0 then
				-- 1-indexed, so effectively no bar showing
				bar_len_bytes = 0
			elseif bar_len >= utf8.len(component.text) then
				bar_len_bytes = #component.text
			else
				bar_len_bytes = utf8.offset(component.text, bar_len + 1) - 1
			end

			if bar_len_bytes > 0 then
				table.insert(output, ui.Span(string.sub(component.text, 1, bar_len_bytes)):style(component.style.left))
			end
			if bar_len_bytes < #component.text then
				table.insert(
					output,
					ui.Span(string.sub(component.text, bar_len_bytes + 1)):style(component.style.right)
				)
			end

			bar_len = bar_len - utf8.len(component.text)
		end

		return ui.Line(output)
	end, opts.position.order, opts.position.parent[opts.position.align])

	---Pass cwd to the plugin for df
	local function callback()
		ya.emit("plugin", {
			st._id,
			ya.quote(tostring(cx.active.current.cwd), true),
		})
	end

	-- Subscribe to events
	ps.sub("cd", callback)
	ps.sub("tab", callback)
	ps.sub("delete", callback)
	-- These are the only relevant events that actually work
	-- Note: df might not immediately reflect usage changes
	--  when deleting files
end

-- Called from ya.emit in the callback
---@param job Job
local function entry(_, job)
	local cwd = job.args[1]

	-- Don't set cwd directly for Command() here, it hangs for dirs without read perms
	-- cwd is fine as an argument to df though
	local output = Command("df"):arg({ "--output=source,pcent", tostring(cwd) }):output()

	-- If df fails, hide the module
	if not output.status.success then
		set_state(nil, nil, nil, nil)
		return
	end

	local source, usage = process_df_output(output.stdout)

	-- If df read the filesystem but couldn't get a percentage, hide the module
	-- if usage == nil then
	if type(usage) ~= "number" then
		set_state(nil, nil, nil, nil)
		return
	end

	-- Get the plugin state (async) early since we know it will be used
	local st = get_state()

	-- If nothing has changed, don't bother updating
	if source == st.source and usage == st.usage then
		return
	end

	local text = format_text(source, usage, st.format)
	local bar_len = 0 -- Start with no bar by default

	-- Only calculate bar length if the bar will be shown
	if st.bar then
		local total_len = utf8.len(st.padding.open .. text .. st.padding.close)

		-- Using ceil so the bar is only empty at 0%
		-- Using len - 1 so the bar isn't full until 100%
		bar_len = usage < 100 and math.ceil((total_len - 1) / 100 * usage) or total_len
	end

	set_state(source, usage, text, bar_len)
end

return { setup = setup, entry = entry }