---@brief
---
--- https://clangd.llvm.org/installation.html
---
--- - **NOTE:** Clang >= 11 is recommended! See [#23](https://github.com/neovim/nvim-lspconfig/issues/23).
--- - If `compile_commands.json` lives in a build directory, you should
---   symlink it to the root of your source tree.
---   ```
---   ln -s /path/to/myproject/build/compile_commands.json /path/to/myproject/
---   ```
--- - clangd relies on a [JSON compilation database](https://clang.llvm.org/docs/JSONCompilationDatabase.html)
---   specified as compile_commands.json, see https://clangd.llvm.org/installation#compile_commandsjson

-- https://clangd.llvm.org/extensions.html#switch-between-sourceheader
local function switch_source_header(bufnr, client)
	local method_name = 'textDocument/switchSourceHeader'
	---@diagnostic disable-next-line:param-type-mismatch
	if not client or not client:supports_method(method_name) then
		return vim.notify(('method %s is not supported by any servers active on the current buffer'):format(method_name))
	end
	local params = vim.lsp.util.make_text_document_params(bufnr)
	---@diagnostic disable-next-line:param-type-mismatch
	client:request(method_name, params, function(err, result)
		if err then
			error(tostring(err))
		end
		if not result then
			vim.notify('corresponding file cannot be determined')
			return
		end
		vim.cmd.edit(vim.uri_to_fname(result))
	end, bufnr)
end

local function symbol_info(bufnr, client)
	local method_name = 'textDocument/symbolInfo'
	---@diagnostic disable-next-line:param-type-mismatch
	if not client or not client:supports_method(method_name) then
		return vim.notify('Clangd client not found', vim.log.levels.ERROR)
	end
	local win = vim.api.nvim_get_current_win()
	local params = vim.lsp.util.make_position_params(win, client.offset_encoding)
	---@diagnostic disable-next-line:param-type-mismatch
	client:request(method_name, params, function(err, res)
		if err or #res == 0 then
			-- Clangd always returns an error, there is no reason to parse it
			return
		end
		local container = string.format('container: %s', res[1].containerName) ---@type string
		local name = string.format('name: %s', res[1].name) ---@type string
		vim.lsp.util.open_floating_preview({ name, container }, '', {
			height = 2,
			width = math.max(string.len(name), string.len(container)),
			focusable = false,
			focus = false,
			title = 'Symbol Info',
		})
	end, bufnr)
end

---@class ClangdInitializeResult: lsp.InitializeResult
---@field offsetEncoding? string

---@type vim.lsp.Config
return {
	cmd = {
		"clangd",
		"--fallback-style=gnu"
	},
	filetypes = { 'c', 'cpp', 'objc', 'objcpp', 'cuda' },
	root_markers = {
		'.clangd',
		'.clang-tidy',
		'.clang-format',
		'compile_commands.json',
		'compile_flags.txt',
		'configure.ac', -- AutoTools
		'.git',
	},
	capabilities = {
		textDocument = {
			completion = {
				editsNearCursor = true,
			},
		},
		offsetEncoding = { 'utf-8', 'utf-16' },
	},
	---@param init_result ClangdInitializeResult
	on_init = function(client, init_result)
		if init_result.offsetEncoding then
			client.offset_encoding = init_result.offsetEncoding
		end
	end,
	on_attach = function(client, bufnr)
		vim.api.nvim_buf_create_user_command(bufnr, 'LspClangdSwitchSourceHeader', function()
			switch_source_header(bufnr, client)
		end, { desc = 'Switch between source/header' })

		vim.api.nvim_buf_create_user_command(bufnr, 'LspClangdShowSymbolInfo', function()
			symbol_info(bufnr, client)
		end, { desc = 'Show symbol info' })
	end,
}