local M = {}

M.config = function()
    function on_attach(client, bufnr)
        local function buf_set_keymap(...)
            vim.api.nvim_buf_set_keymap(bufnr, ...)
        end
        local function buf_set_option(...)
            vim.api.nvim_buf_set_option(bufnr, ...)
        end

        buf_set_option("omnifunc", "v:lua.vim.lsp.omnifunc")

        -- Mappings.
        local opts = {noremap = true, silent = true}

        buf_set_keymap("n", "gD", "<Cmd>lua vim.lsp.buf.declaration()<CR>", opts)
        buf_set_keymap("n", "gd", "<Cmd>lua vim.lsp.buf.definition()<CR>", opts)
        buf_set_keymap("n", "K", "<Cmd>lua vim.lsp.buf.hover()<CR>", opts)
        buf_set_keymap("n", "gi", "<cmd>lua vim.lsp.buf.implementation()<CR>", opts)
        buf_set_keymap("n", "<C-k>", "<cmd>lua vim.lsp.buf.signature_help()<CR>", opts)
        buf_set_keymap("n", "<space>wa", "<cmd>lua vim.lsp.buf.add_workspace_folder()<CR>", opts)
        buf_set_keymap("n", "<space>wr", "<cmd>lua vim.lsp.buf.remove_workspace_folder()<CR>", opts)
        buf_set_keymap("n", "<space>wl", "<cmd>lua print(vim.inspect(vim.lsp.buf.list_workspace_folders()))<CR>", opts)
        buf_set_keymap("n", "<space>D", "<cmd>lua vim.lsp.buf.type_definition()<CR>", opts)
        buf_set_keymap("n", "<space>rn", "<cmd>lua vim.lsp.buf.rename()<CR>", opts)
        buf_set_keymap("n", "gr", "<cmd>lua vim.lsp.buf.references()<CR>", opts)
        buf_set_keymap("n", "<space>e", "<cmd>lua vim.lsp.diagnostic.show_line_diagnostics()<CR>", opts)
        buf_set_keymap("n", "[d", "<cmd>lua vim.lsp.diagnostic.goto_prev()<CR>", opts)
        buf_set_keymap("n", "]d", "<cmd>lua vim.lsp.diagnostic.goto_next()<CR>", opts)
        buf_set_keymap("n", "<space>q", "<cmd>lua vim.lsp.diagnostic.set_loclist()<CR>", opts)

        -- Set some keybinds conditional on server capabilities
        if client.resolved_capabilities.document_formatting then
            buf_set_keymap("n", "<space>f", "<cmd>lua vim.lsp.buf.formatting()<CR>", opts)
        elseif client.resolved_capabilities.document_range_formatting then
            buf_set_keymap("n", "<space>f", "<cmd>lua vim.lsp.buf.range_formatting()<CR>", opts)
        end
    end

    -- lspInstall + lspconfig stuff

    local function setup_servers()
        require "lspinstall".setup()

        local lspconf = require("lspconfig")
        local servers = require "lspinstall".installed_servers()

        for _, lang in pairs(servers) do
            if lang ~= "lua" then
                lspconf[lang].setup {
                    on_attach = on_attach,
                    root_dir = vim.loop.cwd
                }
            elseif lang == "lua" then
                lspconf[lang].setup {
                    root_dir = vim.loop.cwd,
                    settings = {
                        Lua = {
                            diagnostics = {
                                globals = {"vim"}
                            },
                            workspace = {
                                library = {
                                    [vim.fn.expand("$VIMRUNTIME/lua")] = true,
                                    [vim.fn.expand("$VIMRUNTIME/lua/vim/lsp")] = true
                                }
                            },
                            telemetry = {
                                enable = false
                            }
                        }
                    }
                }
            end
        end
    end

    setup_servers()

    -- Automatically reload after `:LspInstall <server>` so we don't have to restart neovim
    require "lspinstall".post_install_hook = function()
        setup_servers() -- reload installed servers
        vim.cmd("bufdo e") -- triggers FileType autocmd that starts the server
    end

    -- replace the default lsp diagnostic letters with prettier symbols
    vim.fn.sign_define("LspDiagnosticsSignError", {text = "", numhl = "LspDiagnosticsDefaultError"})
    vim.fn.sign_define("LspDiagnosticsSignWarning", {text = "", numhl = "LspDiagnosticsDefaultWarning"})
    vim.fn.sign_define("LspDiagnosticsSignInformation", {text = "", numhl = "LspDiagnosticsDefaultInformation"})
    vim.fn.sign_define("LspDiagnosticsSignHint", {text = "", numhl = "LspDiagnosticsDefaultHint"})
end

return M