nvim/lua/lsp/completion/init.lua

local Item = require("lsp.completion.item")
local Popup = require("lsp.completion.popup")
local request = require("lsp.completion.request")

local GROUP = vim.api.nvim_create_augroup("ow.lsp.completion", { clear = true })

local popup = Popup.new()

---@param client vim.lsp.Client
---@param buf integer
local function on_attach(client, buf)
    if
        not client:supports_method(
            vim.lsp.protocol.Methods.textDocument_completion
        )
    then
        return
    end

    vim.bo[buf].omnifunc = "v:lua.ow_lsp_completion.omnifunc"

    vim.api.nvim_clear_autocmds({ group = GROUP, buffer = buf })
    vim.api.nvim_create_autocmd("InsertCharPre", {
        buffer = buf,
        group = GROUP,
        callback = request.on_insert_char_pre,
    })
end

local M = {}

function M.setup()
    vim.lsp.config("*", {
        capabilities = {
            textDocument = {
                completion = {
                    completionItem = { snippetSupport = true },
                },
            },
        },
    })

    vim.api.nvim_create_autocmd("LspAttach", {
        group = GROUP,
        callback = function(ev)
            local client = vim.lsp.get_client_by_id(ev.data.client_id)
            if client then
                on_attach(client, ev.buf)
            end
        end,
    })

    vim.api.nvim_create_autocmd("CompleteChanged", {
        group = GROUP,
        callback = function(ev)
            local completed = vim.v.event.completed_item or {}
            local item = Item.from_user_data(completed)
            local client = item and vim.lsp.get_client_by_id(item.client_id)

            if not item or not client then
                vim.schedule(function()
                    popup:close()
                end)
                return
            end

            local ft = vim.bo[ev.buf].filetype
            ---@type ow.lsp.completion.Pum
            local pum = {
                row = vim.v.event.row,
                col = vim.v.event.col,
                width = vim.v.event.width,
                height = vim.v.event.height,
                scrollbar = vim.v.event.scrollbar,
            }

            if
                client:supports_method(
                    vim.lsp.protocol.Methods.completionItem_resolve
                )
            then
                popup:dispatch_resolve(
                    client,
                    item,
                    ft,
                    pum,
                    completed.word,
                    ev.buf
                )
            else
                vim.schedule(function()
                    popup:show(item, ft, pum)
                end)
            end
        end,
    })

    vim.api.nvim_create_autocmd({ "CompleteDonePre", "InsertLeave" }, {
        group = GROUP,
        callback = function()
            popup:close()
        end,
    })

    vim.api.nvim_create_autocmd("CompleteDone", {
        group = GROUP,
        callback = function(ev)
            local completed = vim.v.completed_item or {}
            local item = Item.from_user_data(completed)
            if not item then
                return
            end
            local client = vim.lsp.get_client_by_id(item.client_id)
            if not client then
                return
            end

            local function apply(target)
                local raw = target.raw
                if raw.additionalTextEdits then
                    vim.lsp.util.apply_text_edits(
                        raw.additionalTextEdits,
                        ev.buf,
                        client.offset_encoding
                    )
                end
                if raw.command then
                    client:request("workspace/executeCommand", {
                        command = raw.command.command,
                        arguments = raw.command.arguments,
                    }, nil, ev.buf)
                end
                if target.snippet then
                    local word = completed.word or ""
                    local cursor = vim.api.nvim_win_get_cursor(0)
                    local row = cursor[1] - 1
                    local col = cursor[2]
                    vim.api.nvim_buf_set_text(
                        ev.buf,
                        row,
                        col - #word,
                        row,
                        col,
                        {}
                    )
                    vim.snippet.expand(target.snippet)
                end
            end

            -- Prefer the resolved item when we have it. If we haven't cached
            -- one yet and the original is missing edits, resolve on the fly.
            local cached = popup:resolved_for(completed.word)
            if cached then
                apply(cached)
            elseif
                client:supports_method(
                    vim.lsp.protocol.Methods.completionItem_resolve
                )
                and not item.raw.additionalTextEdits
                and not item.raw.command
            then
                client:request(
                    vim.lsp.protocol.Methods.completionItem_resolve,
                    item.raw,
                    function(err, resolved)
                        if err or not resolved then
                            return
                        end
                        item:apply_resolved(resolved)
                        apply(item)
                    end,
                    ev.buf
                )
            else
                apply(item)
            end
        end,
    })

    ---@param key string
    ---@param action fun()
    local function scroll_map(key, action)
        vim.keymap.set("i", key, function()
            if popup:is_visible() then
                vim.schedule(action)
                return ""
            end
            return key
        end, { expr = true, replace_keycodes = true })
    end
    scroll_map("<C-d>", function()
        popup:scroll("down", Popup.HALF_PAGE)
    end)
    scroll_map("<C-u>", function()
        popup:scroll("up", Popup.HALF_PAGE)
    end)
    scroll_map("<C-j>", function()
        popup:scroll("down", 1)
    end)
    scroll_map("<C-k>", function()
        popup:scroll("up", 1)
    end)

    vim.keymap.set("i", "<CR>", function()
        if popup:is_visible() then
            return "<C-y>"
        end
        return "<CR>"
    end, { expr = true, replace_keycodes = true })
end

return M