local util = require 'lspconfig.util'
local lsp = vim.lsp

local function buf_cache(bufnr, client)
  local params = {
    command = 'deno.cache',
    arguments = { {}, vim.uri_from_bufnr(bufnr) },
  }
  client.request('workspace/executeCommand', params, function(err, _result, ctx)
    if err then
      local uri = ctx.params.arguments[2]
      vim.api.nvim_err_writeln('cache command failed for ' .. vim.uri_to_fname(uri))
    end
  end, bufnr)
end

local function virtual_text_document_handler(uri, res, client)
  if not res then
    return nil
  end

  local lines = vim.split(res.result, '\n')
  local bufnr = vim.uri_to_bufnr(uri)

  local current_buf = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
  if #current_buf ~= 0 then
    return nil
  end

  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
  vim.api.nvim_set_option_value('readonly', true, { buf = bufnr })
  vim.api.nvim_set_option_value('modified', false, { buf = bufnr })
  vim.api.nvim_set_option_value('modifiable', false, { buf = bufnr })
  lsp.buf_attach_client(bufnr, client.id)
end

local function virtual_text_document(uri, client)
  local params = {
    textDocument = {
      uri = uri,
    },
  }
  local result = client.request_sync('deno/virtualTextDocument', params)
  virtual_text_document_handler(uri, result, client)
end

local function denols_handler(err, result, ctx, config)
  if not result or vim.tbl_isempty(result) then
    return nil
  end

  local client = vim.lsp.get_client_by_id(ctx.client_id)
  for _, res in pairs(result) do
    local uri = res.uri or res.targetUri
    if uri:match '^deno:' then
      virtual_text_document(uri, client)
      res['uri'] = uri
      res['targetUri'] = uri
    end
  end

  lsp.handlers[ctx.method](err, result, ctx, config)
end

return {
  default_config = {
    cmd = { 'deno', 'lsp' },
    cmd_env = { NO_COLOR = true },
    filetypes = {
      'javascript',
      'javascriptreact',
      'javascript.jsx',
      'typescript',
      'typescriptreact',
      'typescript.tsx',
    },
    root_dir = util.root_pattern('deno.json', 'deno.jsonc', '.git'),
    settings = {
      deno = {
        enable = true,
        suggest = {
          imports = {
            hosts = {
              ['https://deno.land'] = true,
            },
          },
        },
      },
    },
    handlers = {
      ['textDocument/definition'] = denols_handler,
      ['textDocument/typeDefinition'] = denols_handler,
      ['textDocument/references'] = denols_handler,
    },
  },
  commands = {
    DenolsCache = {
      function()
        local clients = util.get_lsp_clients { bufnr = 0, name = 'denols' }
        if #clients > 0 then
          buf_cache(0, clients[#clients])
        end
      end,
      description = 'Cache a module and all of its dependencies.',
    },
  },
  docs = {
    description = [[
https://github.com/denoland/deno

Deno's built-in language server

To appropriately highlight codefences returned from denols, you will need to augment vim.g.markdown_fenced languages
 in your init.lua. Example:

```lua
vim.g.markdown_fenced_languages = {
  "ts=typescript"
}
```

]],
    default_config = {
      root_dir = [[root_pattern("deno.json", "deno.jsonc", ".git")]],
    },
  },
}