create context for the llm in neovim

commands.lua

-----------------------------
-- Create context for the LLM
-- Long context prompting tips
-- https://docs.anthropic.com/en/docs/build-with-claude/prompt-engineering/long-context-tips#example-quote-extraction
-----------------------------

-- Dump context with documents tags
vim.api.nvim_create_user_command("ContextDump", function()
  local content = vim.fn.getreg("z")
  vim.fn.setreg("+", "<documents>\n" .. content .. "</documents>")
  vim.fn.setreg("z", "")
  vim.notify("Context dumped to clipboard", vim.log.levels.INFO)
end, { bang = true })

-- Add buffer to context
local function add_buffer_to_context(bufnr)
  -- Get buffer name
  local bufname = vim.api.nvim_buf_get_name(bufnr)
  if bufname == "" then
    return false
  end

  local header = string.format("<document>\n<source>%s</source>\n<document_content>\n", bufname)
  local footer = "\n</document_content>\n</document>\n"

  local lines = vim.api.nvim_buf_get_lines(bufnr, 0, -1, false)
  local content = table.concat(lines, "\n")

  vim.fn.setreg("z", vim.fn.getreg("z") .. header .. content .. footer)
  return true
end

-- Add current file to context
vim.api.nvim_create_user_command("ContextAddBuffer", function()
  if add_buffer_to_context(0) then
    vim.notify("Added file to context", vim.log.levels.INFO)
  end
end, { bang = true })

-- Add all open buffers to context
vim.api.nvim_create_user_command("ContextAddOpenBuffers", function()
  local buffers = vim.api.nvim_list_bufs()
  local added_count = 0

  for _, bufnr in ipairs(buffers) do
    if vim.api.nvim_buf_is_loaded(bufnr) then
      if add_buffer_to_context(bufnr) then
        added_count = added_count + 1
      end
    end
  end

  vim.notify(string.format("Added %d buffers to context", added_count), vim.log.levels.INFO)
end, { bang = true })

-- Add current selection to context
vim.api.nvim_create_user_command("ContextAddSelection", function(opts)
  local start_line = vim.fn.line("'<") - 1 -- nvim_buf_get_lines es 0-based
  local end_line = vim.fn.line("'>")

  local header = string.format(
    "<document>\n<source>%s</source>\n<line_start>%d</line_start>\n<line_end>%d</line_end>\n<document_content>\n",
    vim.fn.expand("%"),
    start_line + 1, -- volvemos a 1-based para el XML
    end_line
  )
  local footer = "\n</document_content>\n</document>\n"

  local lines = vim.api.nvim_buf_get_lines(0, start_line, end_line, false)
  local content = table.concat(lines, "\n")

  vim.fn.setreg("z", vim.fn.getreg("z") .. header .. content .. footer)
  vim.notify("Added selection to context", vim.log.levels.INFO)
end, { range = true, bang = true })

-- Copy function to context
vim.api.nvim_create_user_command("ContextAddFunction", function()
  local current_pos = vim.fn.getpos(".")
  vim.cmd('normal "Zyas') -- usar treesitter para obtener el scope

  local start_line = current_pos[2]
  local end_line = start_line + #vim.fn.split(vim.fn.getreg("Z"), "\n") - 1

  local header = string.format("<document>\n<source>%s</source>\n<line_start>%d</line_start>\n<line_end>%d</line_end>\n<document_content>\n", vim.fn.expand("%"), start_line, end_line)
  local footer = "\n</document_content>\n</document>\n"

  local content = vim.fn.getreg("Z")
  vim.fn.setreg("z", vim.fn.getreg("z") .. header .. content .. footer)
  vim.notify("Added function to context", vim.log.levels.INFO)
end, { bang = true })

-- Add directory structure to context
vim.api.nvim_create_user_command("ContextAddDirectoryStructure", function()
  if vim.fn.executable("tree") ~= 1 then
    vim.notify("'tree' command not found. Please install it first.", vim.log.levels.ERROR)
    return
  end

  local header = string.format("<document>\n<source>directory_structure</source>\n<document_content>\n")
  local footer = "\n</document_content>\n</document>\n"

  -- -I para ignorar .git explícitamente, además de usar --gitignore
  local cmd = 'tree -L 3 -a --gitignore --noreport --dirsfirst -I ".git"'
  local lines = vim.fn.systemlist(cmd)
  local content = table.concat(lines, "\n")

  vim.fn.setreg("z", vim.fn.getreg("z") .. header .. content .. footer)
  vim.notify("Added directory structure to context", vim.log.levels.INFO)
end, { bang = true })

-----------
-- Mappings
-----------

-- ContextAddOpenBuffers
-- ContextAddFunction
-- ContextAddDirectoryStructure
vim.keymap.set("v", "<F9>", ":<C-u>ContextAddSelection<CR>", { noremap = true, silent = true })
vim.keymap.set("n", "<F9>", ":<C-u>ContextAddBuffer<CR>", { noremap = true, silent = true })
vim.keymap.set("n", "<F10>", ":ContextDump<CR>", { noremap = true, silent = true })