local api = vim.api

local M = {}

local SignatureHelp = {}
SignatureHelp.__index = SignatureHelp

function SignatureHelp.new()
	local instance = setmetatable({
		win = nil,
		buf = nil,
		dock_win = nil,
		dock_buf = nil,
		dock_win_id = "signature_help_dock_" .. vim.api.nvim_get_current_buf(),
		timer = nil,
		visible = false,
		current_signatures = nil,
		enabled = false,
		normal_mode_active = false,
		current_signature_idx = nil,
		config = nil,
	}, SignatureHelp)

	instance._default_config = {
		silent = false,
		number = true,
		icons = {
			parameter = "",
			method = "󰡱",
			documentation = "󱪙",
		},
		colors = {
			parameter = "#86e1fc",
			method = "#c099ff",
			documentation = "#4fd6be",
			default_value = "#a80888",
		},
		active_parameter_colors = {
			bg = "#86e1fc",
			fg = "#1a1a1a",
		},
		border = "solid",
		winblend = 10,
		auto_close = true,
		trigger_chars = { "(", "," },
		max_height = 10,
		max_width = 40,
		floating_window_above_cur_line = true,
		preview_parameters = true,
		debounce_time = 100,
		dock_toggle_key = "<Leader>sd",
		toggle_key = "<C-k>",
		dock_mode = {
			enabled = false,
			position = "bottom",
			height = 3,
			padding = 1,
		},
		render_style = {
			separator = true,
			compact = true,
			align_icons = true,
		},
	}

	return instance
end

local function signature_index_comment(index)
	if #vim.bo.commentstring ~= 0 then
		return vim.bo.commentstring:format(index)
	else
		return "(" .. index .. ")"
	end
end

local function markdown_for_signature_list(signatures, config)
	local lines, labels = {}, {}
	local number = config.number and #signatures > 1
	local max_method_len = 0

	-- First pass to calculate alignment
	if config.render_style.align_icons then
		for _, signature in ipairs(signatures) do
			max_method_len = math.max(max_method_len, #signature.label)
		end
	end

	for index, signature in ipairs(signatures) do
		if not config.render_style.compact then
			table.insert(lines, "")
		end
		table.insert(labels, #lines + 1)

		local suffix = number and (" " .. signature_index_comment(index)) or ""
		local padding = config.render_style.align_icons and string.rep(" ", max_method_len - #signature.label) or " "

		-- Method signature with syntax highlighting
		table.insert(lines, string.format("```%s", vim.bo.filetype))
		-- table.insert(lines, string.format("%s Method:", config.icons.method))
		table.insert(lines, string.format("%s %s%s%s", config.icons.method, signature.label, padding, suffix))
		table.insert(lines, "```")

		-- -- Parameters section
		-- if signature.parameters and #signature.parameters > 0 then
		-- 	if config.render_style.separator then
		-- 		table.insert(lines, string.rep("─", 40))
		-- 	end
		-- 	table.insert(lines, string.format("%s Parameters:", config.icons.parameter))
		-- 	for _, param in ipairs(signature.parameters) do
		-- 		local param_doc = param.documentation and string.format(" - %s", vim.inspect(param.documentation))
		-- 		table.insert(lines, string.format("  • %s = %s", vim.inspect(param.label), param_doc))
		-- 	end
		-- end

		-- Documentation section
		if signature.documentation then
			if config.render_style.separator then
				table.insert(lines, string.rep("─", 40))
			end
			table.insert(lines, string.format("%s Documentation:", config.icons.documentation))
			local doc_lines = vim.split(signature.documentation.value or signature.documentation, "\n")
			for _, line in ipairs(doc_lines) do
				table.insert(lines, "  " .. line)
			end
		end

		if index ~= #signatures and config.render_style.separator then
			table.insert(lines, string.rep("═", 40))
		end
	end
	return lines, labels
end

function SignatureHelp:create_float_window(contents)
	local max_width = math.min(self.config.max_width, vim.o.columns)
	local max_height = math.min(self.config.max_height, #contents)

	-- Calculate optimal position
	local cursor = api.nvim_win_get_cursor(0)
	local cursor_line = cursor[1]
	local screen_line = vim.fn.screenpos(0, cursor_line, 1).row

	local row_offset = self.config.floating_window_above_cur_line and -max_height - 1 or 1
	if screen_line + row_offset < 1 then
		row_offset = 2 -- Show below if not enough space above
	end

	local win_config = {
		relative = "cursor",
		row = row_offset - 1,
		col = 0,
		width = max_width,
		height = max_height,
		style = "minimal",
		border = self.config.border,
		zindex = 50, -- Ensure it's above most other floating windows
	}

	if self.win and api.nvim_win_is_valid(self.win) then
		api.nvim_win_set_config(self.win, win_config)
		api.nvim_win_set_buf(self.win, self.buf)
	else
		self.buf = api.nvim_create_buf(false, true)
		self.win = api.nvim_open_win(self.buf, false, win_config)
	end

	vim.bo[self.buf].modifiable = true
	api.nvim_buf_set_lines(self.buf, 0, -1, false, contents)
	vim.bo[self.buf].modifiable = false
	vim.wo[self.win][self.buf].foldenable = false
	vim.wo[self.win][self.buf].wrap = true
	vim.wo[self.win][self.buf].winblend = self.config.winblend
	self.visible = true
end

function SignatureHelp:hide()
	if self.visible then
		-- Store current window and buffer
		local current_win = api.nvim_get_current_win()
		local current_buf = api.nvim_get_current_buf()

		-- Close appropriate window based on mode
		if self.config.dock_mode.enabled then
			self:close_dock_window()
		else
			if self.win and api.nvim_win_is_valid(self.win) then
				pcall(api.nvim_win_close, self.win, true)
			end
			if self.buf and api.nvim_buf_is_valid(self.buf) then
				pcall(api.nvim_buf_delete, self.buf, { force = true })
			end
			self.win = nil
			self.buf = nil
		end

		self.current_signatures = nil
		self.visible = false

		-- Restore focus
		pcall(api.nvim_set_current_win, current_win)
		pcall(api.nvim_set_current_buf, current_buf)
	end
end

function SignatureHelp:find_parameter_range(signature_str, parameter_label)
	-- Handle both string and table parameter labels
	if type(parameter_label) == "table" then
		return parameter_label[1], parameter_label[2]
	end

	-- Escape special pattern characters in parameter_label
	local escaped_label = vim.pesc(parameter_label)

	-- Look for the parameter with word boundaries
	local pattern = [[\<]] .. escaped_label .. [[\>]]
	local start_pos, end_pos = signature_str:find(pattern)

	if not start_pos then
		-- Fallback: try finding exact match if word boundary search fails
		start_pos, end_pos = signature_str:find(escaped_label)
	end

	if not start_pos then
		return nil, nil
	end

	-- local end_pos = start_pos + #parameter_label
	return start_pos, end_pos
end

function SignatureHelp:extract_default_value(param_info)
	-- Check if parameter has documentation that might contain default value
	if not param_info.documentation then
		return nil
	end

	local doc = type(param_info.documentation) == "string" and param_info.documentation
		or param_info.documentation.value

	-- Look for common default value patterns
	local patterns = {
		"default:%s*([^%s]+)",
		"defaults%s+to%s+([^%s]+)",
		"%(default:%s*([^%)]+)%)",
	}

	for _, pattern in ipairs(patterns) do
		local default = doc:match(pattern)
		if default then
			return default
		end
	end

	return nil
end

function SignatureHelp:set_active_parameter_highlights(active_parameter, signatures, labels)
	if not self.buf or not api.nvim_buf_is_valid(self.buf) then
		return
	end

	-- Clear existing highlights
	api.nvim_buf_clear_namespace(self.buf, -1, 0, -1)

	-- Iterate over signatures to highlight the active parameter
	for index, signature in ipairs(signatures) do
		local parameter = signature.activeParameter or active_parameter
		if parameter and parameter >= 0 and parameter < #signature.parameters then
			local label = signature.parameters[parameter + 1].label
			if type(label) == "string" then
				-- Parse the signature string to find the exact range of the active parameter
				local signature_str = signature.label
				local start_pos, end_pos = self:find_parameter_range(signature_str, label)
				if start_pos and end_pos then
					api.nvim_buf_add_highlight(
						self.buf,
						-1,
						"LspSignatureActiveParameter",
						labels[index],
						start_pos,
						end_pos
					)
				end
			elseif type(label) == "table" then
				local start_pos, end_pos = unpack(label)
				api.nvim_buf_add_highlight(
					self.buf,
					-1,
					"LspSignatureActiveParameter",
					labels[index],
					start_pos + 6,
					end_pos + 6
				)
			end
		end
	end

	-- Add icon highlights
	local icon_highlights = {
		{ self.config.icons.method, "SignatureHelpMethod" },
		{ self.config.icons.parameter, "SignatureHelpParameter" },
		{ self.config.icons.documentation, "SignatureHelpDocumentation" },
	}

	for _, icon_hl in ipairs(icon_highlights) do
		local icon, hl_group = unpack(icon_hl)
		local line_num = 0
		while line_num < api.nvim_buf_line_count(self.buf) do
			local line = api.nvim_buf_get_lines(self.buf, line_num, line_num + 1, false)[1]
			local start_col = line:find(vim.pesc(icon))
			if start_col then
				api.nvim_buf_add_highlight(self.buf, -1, hl_group, line_num, start_col - 1, start_col + #icon - 1)
			end
			line_num = line_num + 1
		end
	end
end

function SignatureHelp:highlight_icons()
	local icon_highlights = {
		{ self.config.icons.method, "SignatureHelpMethod" },
		{ self.config.icons.parameter, "SignatureHelpParameter" },
		{ self.config.icons.documentation, "SignatureHelpDocumentation" },
	}

	for _, icon_hl in ipairs(icon_highlights) do
		local icon, hl_group = unpack(icon_hl)
		local line_num = 0
		while line_num < api.nvim_buf_line_count(self.buf) do
			local line = api.nvim_buf_get_lines(self.buf, line_num, line_num + 1, false)[1]
			local start_col = line:find(vim.pesc(icon))
			if start_col then
				api.nvim_buf_add_highlight(self.buf, -1, hl_group, line_num, start_col - 1, start_col - 1 + #icon)
			end
			line_num = line_num + 1
		end
	end
end

function SignatureHelp:display(result)
	if not result or not result.signatures or #result.signatures == 0 then
		self:hide()
		return
	end

	-- Store current window and buffer
	local current_win = api.nvim_get_current_win()
	local current_buf = api.nvim_get_current_buf()

	-- Prevent duplicate displays of identical content
	if
		self.current_signatures
		and vim.deep_equal(result.signatures, self.current_signatures)
		and result.activeParameter == self.current_active_parameter
	then
		return
	end

	local markdown, labels = markdown_for_signature_list(result.signatures, self.config)
	self.current_signatures = result.signatures
	self.current_active_parameter = result.activeParameter

	if #markdown > 0 then
		if self.config.dock_mode.enabled then
			local win, buf = self:create_dock_window()
			if win and buf then
				api.nvim_buf_set_option(buf, "modifiable", true)
				api.nvim_buf_set_lines(buf, 0, -1, false, markdown)
				api.nvim_buf_set_option(buf, "modifiable", false)
				self:set_active_parameter_highlights(result.activeParameter, result.signatures, labels)
				self:apply_treesitter_highlighting()
			end
		else
			self:create_float_window(markdown)
			api.nvim_buf_set_option(self.buf, "filetype", "markdown")
			self:set_active_parameter_highlights(result.activeParameter, result.signatures, labels)
			self:apply_treesitter_highlighting()
		end
	else
		self:hide()
	end

	-- Restore focus to original window and buffer
	api.nvim_set_current_win(current_win)
	api.nvim_set_current_buf(current_buf)
end

function SignatureHelp:apply_treesitter_highlighting()
	local buf = self.config.dock_mode.enabled and self.dock_buf or self.buf
	if not buf or not api.nvim_buf_is_valid(buf) then
		return
	end

	if not pcall(require, "nvim-treesitter") then
		return
	end

	-- Store current window and buffer
	local current_win = api.nvim_get_current_win()
	local current_buf = api.nvim_get_current_buf()

	-- Apply treesitter highlighting
	pcall(function()
		require("nvim-treesitter.highlight").attach(buf, "markdown")
	end)

	-- Restore focus
	api.nvim_set_current_win(current_win)
	api.nvim_set_current_buf(current_buf)
end

function SignatureHelp:trigger()
	if not self.enabled then
		return
	end
	vim.notify("trigger")

	local params = vim.lsp.util.make_position_params()
	vim.lsp.buf_request(0, "textDocument/signatureHelp", params, function(err, result, _, _)
		if err then
			if not self.config.silent then
				vim.notify("Error in LSP Signature Help: " .. vim.inspect(err), vim.log.levels.ERROR)
			end
			self:hide()
			return
		end

		if result and result.signatures and #result.signatures > 0 then
			self:display(result)
		else
			self:hide()
			-- Only notify if not silent and if there was actually no signature help
			if not self.config.silent and result then
				vim.notify("No signature help available", vim.log.levels.INFO)
			end
		end
	end)
end

function SignatureHelp:check_capability()
	local clients = vim.lsp.get_clients()
	for _, client in ipairs(clients) do
		if client.server_capabilities.signatureHelpProvider then
			self.enabled = true
			return
		end
	end
	self.enabled = false
end

function SignatureHelp:toggle_normal_mode()
	self.normal_mode_active = not self.normal_mode_active
	if self.normal_mode_active then
		self:trigger()
	else
		self:hide()
	end
end

function SignatureHelp:setup_autocmds()
	local group = api.nvim_create_augroup("LspSignatureHelp", { clear = true })

	local function debounced_trigger()
		-- vim.defer_fn(function()
		-- 	self:trigger()
		-- end, 30)
		if self.timer then
			vim.fn.timer_stop(self.timer)
		end
		self.timer = vim.fn.timer_start(self.debounce_time, function()
			self:trigger()
		end)
	end

	api.nvim_create_autocmd({ "InsertEnter", "CursorMovedI" }, {
		group = group,
		callback = function()
			-- vim.notify("trigger")

			-- local cmp_visible = require("cmp").visible()
			-- if cmp_visible then
			-- self:hide()
			-- elseif vim.fn.pumvisible() == 0 then
			debounced_trigger()
			-- else
			-- self:hide()
			-- end
		end,
	})

	api.nvim_create_autocmd({ "CursorMoved" }, {
		group = group,
		callback = function()
			if self.normal_mode_active then
				debounced_trigger()
			end
		end,
	})

	api.nvim_create_autocmd({ "InsertLeave" }, {
		group = group,
		callback = function()
			self:hide()
			self.normal_mode_active = false
		end,
	})

	api.nvim_create_autocmd("LspAttach", {
		group = group,
		callback = function()
			vim.defer_fn(function()
				self:check_capability()
			end, 100)
		end,
	})

	api.nvim_create_autocmd("ColorScheme", {
		group = group,
		callback = function()
			if self.visible then
				self:apply_treesitter_highlighting()
				self:set_active_parameter_highlights(
					self.current_signatures.activeParameter,
					self.current_signatures,
					{}
				)
			end
		end,
	})
end

function SignatureHelp:create_dock_window()
	-- Store current window and buffer
	local current_win = api.nvim_get_current_win()
	local current_buf = api.nvim_get_current_buf()

	-- Update dock window ID for current buffer
	self.dock_win_id = "signature_help_dock_" .. current_buf

	if not self.dock_win or not api.nvim_win_is_valid(self.dock_win) then
		-- Create dock buffer if needed
		if not self.dock_buf or not api.nvim_buf_is_valid(self.dock_buf) then
			self.dock_buf = api.nvim_create_buf(false, true)
			api.nvim_buf_set_option(self.dock_buf, "buftype", "nofile")
			api.nvim_buf_set_option(self.dock_buf, "bufhidden", "hide")
			api.nvim_buf_set_option(self.dock_buf, "modifiable", false)
			api.nvim_buf_set_option(self.dock_buf, "filetype", "markdown")

			-- Set buffer name with ID for easier tracking
			api.nvim_buf_set_name(self.dock_buf, self.dock_win_id)
		end

		-- Calculate dock position and dimensions
		local win_height = api.nvim_win_get_height(current_win)
		local win_width = api.nvim_win_get_width(current_win)
		local dock_height = math.min(self.config.dock_mode.height, math.floor(win_height * 0.3))
		local padding = self.config.dock_mode.padding
		local dock_width = win_width - (padding * 2)

		local row = self.config.dock_mode.position == "bottom" and win_height - dock_height - padding or padding

		-- Create dock window with enhanced config
		self.dock_win = api.nvim_open_win(self.dock_buf, false, {
			relative = "win",
			win = current_win,
			width = dock_width,
			height = dock_height,
			row = row,
			col = padding,
			style = "minimal",
			border = self.config.border,
			zindex = 45,
			focusable = false, -- Make window non-focusable to prevent focus issues
		})

		-- Apply window options
		local win_opts = {
			wrap = true,
			winblend = self.config.winblend,
			foldenable = false,
			cursorline = false,
			winhighlight = "Normal:SignatureHelpDock,FloatBorder:SignatureHelpBorder",
			signcolumn = "no",
		}

		for opt, value in pairs(win_opts) do
			api.nvim_win_set_option(self.dock_win, opt, value)
		end

		-- Set up dock window keymaps
		local dock_buf_keymaps = {
			["q"] = function()
				self:hide()
			end,
			["<Esc>"] = function()
				self:hide()
			end,
			["<C-c>"] = function()
				self:hide()
			end,
			["<C-n>"] = function()
				self:next_signature()
			end,
			["<C-p>"] = function()
				self:prev_signature()
			end,
		}

		for key, func in pairs(dock_buf_keymaps) do
			vim.keymap.set("n", key, func, { buffer = self.dock_buf, silent = true, nowait = true })
		end

		-- Set window ID as a window variable
		api.nvim_win_set_var(self.dock_win, "signature_help_id", self.dock_win_id)
	end

	-- Ensure focus returns to original window
	api.nvim_set_current_win(current_win)

	return self.dock_win, self.dock_buf
end

function SignatureHelp:close_dock_window()
	-- Fast check for existing dock window
	if not self.dock_win_id then
		return
	end

	-- Try to find window by ID
	local wins = api.nvim_list_wins()
	for _, win in ipairs(wins) do
		local ok, win_id = pcall(api.nvim_win_get_var, win, "signature_help_id")
		if ok and win_id == self.dock_win_id then
			pcall(api.nvim_win_close, win, true)
			break
		end
	end

	-- Clean up buffer
	if self.dock_buf and api.nvim_buf_is_valid(self.dock_buf) then
		pcall(api.nvim_buf_delete, self.dock_buf, { force = true })
	end

	-- Reset dock window state
	self.dock_win = nil
	self.dock_buf = nil
end

-- Add navigation between multiple signatures
function SignatureHelp:next_signature()
	if not self.current_signatures then
		return
	end
	self.current_signature_idx = (self.current_signature_idx or 0) + 1
	if self.current_signature_idx > #self.current_signatures then
		self.current_signature_idx = 1
	end
	self:display({
		signatures = self.current_signatures,
		activeParameter = self.current_active_parameter,
		activeSignature = self.current_signature_idx - 1,
	})
end

function SignatureHelp:prev_signature()
	if not self.current_signatures then
		return
	end
	self.current_signature_idx = (self.current_signature_idx or 1) - 1
	if self.current_signature_idx < 1 then
		self.current_signature_idx = #self.current_signatures
	end
	self:display({
		signatures = self.current_signatures,
		activeParameter = self.current_active_parameter,
		activeSignature = self.current_signature_idx - 1,
	})
end

function SignatureHelp:toggle_dock_mode()
	-- Store current window and buffer
	local current_win = api.nvim_get_current_win()
	local current_buf = api.nvim_get_current_buf()

	-- Store current signatures
	local current_sigs = self.current_signatures
	local current_active = self.current_active_parameter

	-- Close existing windows efficiently
	if self.config.dock_mode.enabled then
		self:close_dock_window()
	else
		if self.win and api.nvim_win_is_valid(self.win) then
			pcall(api.nvim_win_close, self.win, true)
			pcall(api.nvim_buf_delete, self.buf, { force = true })
			self.win = nil
			self.buf = nil
		end
	end

	-- Toggle mode
	self.config.dock_mode.enabled = not self.config.dock_mode.enabled

	-- Redisplay if we had signatures
	if current_sigs then
		self:display({
			signatures = current_sigs,
			activeParameter = current_active,
		})
	end

	-- Restore focus
	pcall(api.nvim_set_current_win, current_win)
	pcall(api.nvim_set_current_buf, current_buf)
end

function SignatureHelp:setup_keymaps()
	-- Setup toggle keys using the actual config
	local toggle_key = self.config.toggle_key
	local dock_toggle_key = self.config.dock_toggle_key

	if toggle_key then
		vim.keymap.set("n", toggle_key, function()
			self:toggle_normal_mode()
		end, { noremap = true, silent = true, desc = "Toggle signature help in normal mode" })
	end

	if dock_toggle_key then
		vim.keymap.set("n", dock_toggle_key, function()
			self:toggle_dock_mode()
		end, { noremap = true, silent = true, desc = "Toggle between dock and float mode" })
	end
end

function M.setup(opts)
	-- Ensure setup is called only once
	if M._initialized then
		return M._instance
	end

	opts = opts or {}
	local signature_help = SignatureHelp.new()

	-- Deep merge user config with defaults
	signature_help.config = vim.tbl_deep_extend("force", signature_help._default_config, opts)

	-- Setup highlights with user config
	local function setup_highlights()
		local colors = signature_help.config.colors
		local highlights = {
			SignatureHelpDock = { link = "NormalFloat" },
			SignatureHelpBorder = { link = "FloatBorder" },
			SignatureHelpMethod = { fg = colors.method },
			SignatureHelpParameter = { fg = colors.parameter },
			SignatureHelpDocumentation = { fg = colors.documentation },
			SignatureHelpDefaultValue = { fg = colors.default_value, italic = true },
			LspSignatureActiveParameter = {
				fg = signature_help.config.active_parameter_colors.fg,
				bg = signature_help.config.active_parameter_colors.bg,
			},
		}

		for group, hl_opts in pairs(highlights) do
			vim.api.nvim_set_hl(0, group, hl_opts)
		end
	end

	-- Setup highlights and ensure they persist across colorscheme changes
	setup_highlights()
	vim.api.nvim_create_autocmd("ColorScheme", {
		group = vim.api.nvim_create_augroup("LspSignatureColors", { clear = true }),
		callback = setup_highlights,
	})

	-- Setup autocmds and keymaps
	signature_help:setup_autocmds()
	signature_help:setup_keymaps()

	-- Store instance for potential reuse
	M._initialized = true
	M._instance = signature_help

	return signature_help
end

-- Add version and metadata for lazy.nvim compatibility
M.version = "1.0.0"
M.dependencies = {
	"nvim-treesitter/nvim-treesitter",
}

-- Add API methods for external use
M.toggle_dock = function()
	if M._instance then
		M._instance:toggle_dock_mode()
	end
end

M.toggle_normal_mode = function()
	if M._instance then
		M._instance:toggle_normal_mode()
	end
end

return M