local M = {}

local function within(path, root)
  return path == root or path:sub(1, #root + 1) == root .. "/"
end

local function setup_formatting(state)
  if state.formatting then
    return
  end
  local ok, conform = pcall(require, "conform")
  if not ok then
    vim.notify("Modulus formatting requires conform.nvim", vim.log.levels.WARN)
    return
  end
  state.formatting = true
  local function project(buf)
    local ft = vim.bo[buf].filetype
    if ft ~= "c" and ft ~= "cpp" and ft ~= "python" then
      return nil
    end
    return state.project(vim.api.nvim_buf_get_name(buf))
  end
  local fallback = conform.formatters_by_ft["_"]
  for _, ft in ipairs({ "c", "cpp", "python", "*" }) do
    local original = conform.formatters_by_ft[ft]
    if ft ~= "*" and (not original or (type(original) == "table" and vim.tbl_isempty(original))) then
      original = fallback
    end
    conform.formatters_by_ft[ft] = function(buf)
      if project(buf) then
        if ft == "*" then
          return {}
        end
        return { "modulus", lsp_format = "never", timeout_ms = 10000 }
      end
      if type(original) == "function" then
        return original(buf) or {}
      end
      return original or {}
    end
  end
  conform.formatters.modulus = {
    command = "python3",
    env = { MODULUS_DIRECT = "0" },
    args = function(_, context)
      local root = assert(project(context.buf))
      local args = vim.uv.fs_stat(root .. "/modulus/cli.py")
        and { root .. "/tools/format.py" }
        or { root .. "/modulus.py", "format" }
      vim.list_extend(args, { "--stdin-filename", context.filename })
      return args
    end,
    cwd = function(_, context) return project(context.buf) end,
    stdin = true,
  }
  -- LazyVim already owns save/manual formatting and its global/buffer toggles.
  local has_save, save_hooks = pcall(vim.api.nvim_get_autocmds, { event = "BufWritePre", group = "Conform" })
  if not rawget(_G, "LazyVim") and (not has_save or #save_hooks == 0) then
    vim.api.nvim_create_autocmd("BufWritePre", {
      group = vim.api.nvim_create_augroup("ModulusFormat", { clear = true }),
      callback = function(event)
        if project(event.buf) and vim.g.autoformat ~= false and vim.b[event.buf].autoformat ~= false
          and not vim.g.disable_autoformat and not vim.b[event.buf].disable_autoformat then
          conform.format({ bufnr = event.buf, lsp_format = "never", timeout_ms = 10000 })
        end
      end,
    })
  end
end

function M.setup(root)
  if vim.fn.has("nvim-0.11") ~= 1 then
    vim.notify("Modulus container clangd requires Neovim 0.11+", vim.log.levels.ERROR)
    return
  end
  root = vim.fs.normalize(root)
  -- Finish LazyVim's server setup before changing only the command and root routing.
  local has_lazy, lazy = pcall(require, "lazy")
  if has_lazy then
    lazy.load({ plugins = { "nvim-lspconfig", "conform.nvim" } })
  end
  local state = rawget(_G, "modulus_clangd")
  if not state then
    state = { roots = {} }
    _G.modulus_clangd = state
    local original = vim.lsp.config.clangd or { cmd = { "clangd" }, filetypes = { "c", "cpp", "objc", "objcpp", "cuda" } }
    if not vim.lsp.config.clangd then
      vim.lsp.config("clangd", original)
    end
    local original_cmd, original_root = original.cmd, original.root_dir
    local cache = vim.fs.normalize((vim.env.XDG_CACHE_HOME or (vim.env.HOME .. "/.cache")) .. "/modulus/clangd")
    local function project(path)
      local best
      for candidate in pairs(state.roots) do
        if within(path, candidate) and (not best or #candidate > #best) then
          best = candidate
        end
      end
      return best
    end
    state.project = project
    vim.lsp.config("clangd", {
      cmd = function(dispatchers, config)
        local selected = config.root_dir and state.roots[config.root_dir]
        if selected then
          config._modulus_container = true
          return vim.lsp.rpc.start(selected, dispatchers, { cwd = config.root_dir })
        end
        if type(original_cmd) == "function" then
          return original_cmd(dispatchers, config)
        end
        return vim.lsp.rpc.start(original_cmd or { "clangd" }, dispatchers, { cwd = config.root_dir })
      end,
      root_dir = function(buf, on_dir)
        local name = vim.api.nvim_buf_get_name(buf)
        if within(name, cache) then
          local clients = vim.tbl_filter(function(client) return client.config._modulus_container end, vim.lsp.get_clients({ name = "clangd" }))
          if #clients == 1 then
            vim.lsp.buf_attach_client(buf, clients[1].id)
          end
          return
        end
        local selected = project(name)
        if selected then
          on_dir(selected)
        elseif type(original_root) == "function" then
          original_root(buf, on_dir)
        elseif type(original_root) == "string" then
          on_dir(original_root)
        else
          on_dir(vim.fs.root(name, { ".clangd", "compile_commands.json", ".git" }) or vim.fs.dirname(name))
        end
      end,
    })
    vim.api.nvim_create_autocmd("BufReadPost", {
      group = vim.api.nvim_create_augroup("ModulusClangdHeaders", { clear = true }),
      callback = function(event)
        if within(vim.api.nvim_buf_get_name(event.buf), cache) then
          vim.bo[event.buf].readonly = true
          vim.bo[event.buf].modifiable = false
        end
      end,
    })
  end
  local command
  if vim.uv.fs_stat(root .. "/modulus/cli.py") then
    command = { "python3", root .. "/tools/clangd.py" }
  else
    command = { "python3", root .. "/modulus.py", "clangd" }
  end
  state.roots[root] = command
  setup_formatting(state)
  for _, client in ipairs(vim.lsp.get_clients({ name = "clangd" })) do
    if not client.config._modulus_container and client.config.root_dir and within(client.config.root_dir, root) then
      client:stop()
    end
  end
  vim.lsp.enable("clangd")
end

return M