-- Ref: https://github.com/neovim/nvim-lspconfig/blob/master/lsp/clangd.lua

---@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

-- NOTES:
-- Clangd requires compile_commands.json to work and the easiest way to generate it is to use CMake.
-- How to use clangd C/C++ LSP in any project: https://gist.github.com/Strus/042a92a00070a943053006bf46912ae9

-- 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

return {
    cmd = {
        'clangd',
        '--clang-tidy',
        '--header-insertion=iwyu',
        '--completion-style=detailed',
        '--function-arg-placeholders',
        '--fallback-style=none',
    },
    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 client vim.lsp.Client
    ---@param init_result ClangdInitializeResult
    on_init = function(client, init_result)
        if init_result.offsetEncoding then
            client.offset_encoding = init_result.offsetEncoding
        end
    end,
    ---@param client vim.lsp.Client
    ---@param bufnr integer
    on_attach = function(client, bufnr)
        -- Create a command to switch between source file and header
        -- https://clangd.llvm.org/extensions.html#switch-between-sourceheader
        vim.api.nvim_buf_create_user_command(bufnr, 'ClangdSwitchSourceHeader', function()
            switch_source_header(bufnr, client)
        end, { desc = 'Switch between the main source file (*.cpp) and header (*.h)' })

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