local M = {}

-- get git remote url and extract username/repo
local function get_repo_info()
  local handle = io.popen("git config --get remote.origin.url 2>/dev/null")
  if not handle then
    return nil, "Failed to execute git command"
  end

  local remote = handle:read("*a")
  handle:close()

  if remote == "" then
    return nil, "No git remote found"
  end

  -- Remove trailing whitespace/newline
  remote = remote:gsub("%s+$", "")

  -- https://host/username/repo or https://host/username/repo.git
  local user_repo = remote:match("[:/]([^:/]+/[^/]+)%.?g?i?t?$")

  if not user_repo then
    return nil, "Could not parse repository from remote: " .. remote
  end

  -- Remove .git suffix if present
  user_repo = user_repo:gsub("%.git$", "")

  return user_repo, nil
end

-- Get current git commit hash
local function get_commit_hash()
  local handle = io.popen("git rev-parse HEAD 2>/dev/null")
  if not handle then
    return nil, "Failed to execute git command"
  end

  local hash = handle:read("*a")
  handle:close()

  if hash == "" then
    return nil, "Not in a git repository"
  end

  return hash:gsub("%s+$", ""), nil
end

-- Get file path relative to git root
local function get_relative_path(absolute_path)
  local handle = io.popen("git rev-parse --show-toplevel 2>/dev/null")
  if not handle then
    return nil, "Failed to execute git command"
  end

  local git_root = handle:read("*a")
  handle:close()

  if git_root == "" then
    return nil, "Not in a git repository"
  end

  git_root = git_root:gsub("%s+$", "")

  -- Remove git root from absolute path
  local rel_path = absolute_path:gsub("^" .. git_root .. "/", "")
  return rel_path, nil
end

-- copy text to system clipboard
local function copy_to_clipboard(text)
  vim.fn.setreg("+", text)
  vim.fn.setreg('"', text)
end

-- generate and copy permalink
function M.copy_permalink()
  local repo, err = get_repo_info()
  if err then
    vim.notify("Error: " .. err, vim.log.levels.ERROR)
    return
  end

  local commit, err = get_commit_hash()
  if err then
    vim.notify("Error: " .. err, vim.log.levels.ERROR)
    return
  end

  local filepath = vim.fn.expand("%:p")
  local rel_path, err = get_relative_path(filepath)
  if err then
    vim.notify("Error: " .. err, vim.log.levels.ERROR)
    return
  end

  -- get line numbers
  local mode = vim.fn.mode()
  local start_line, end_line

  if mode == "v" or mode == "V" or mode == "\22" then -- visual modes
    start_line = vim.fn.line("v")
    end_line = vim.fn.line(".")

    -- ensure start_line <= end_line
    if start_line > end_line then
      start_line, end_line = end_line, start_line
    end
  else
    start_line = vim.fn.line(".")
    end_line = start_line
  end

  -- construct url
  local url = string.format(
    "https://tangled.org/%s/blob/%s/%s#L%d",
    repo,
    commit,
    rel_path,
    start_line
  )

  -- add end line if selection spans multiple lines
  if end_line > start_line then
    url = url .. "-" .. end_line
  end

  -- copy to clipboard
  copy_to_clipboard(url)


  if end_line > start_line then
    vim.notify(string.format("Copied permalink for lines %d-%d", start_line, end_line), vim.log.levels.INFO)
  else
    vim.notify(string.format("Copied permalink for line %d", start_line), vim.log.levels.INFO)
  end
end

-- setup function to configure the plugin
function M.setup(opts)
  opts = opts or {}
  vim.api.nvim_create_user_command(
    "TangledPermalink",
    function()
      M.copy_permalink()
    end,
    { range = true, desc = "Copy tangled.org permalink to clipboard" }
  )
end

-- set up keybindings
vim.keymap.set({"n", "v"}, "<leader>gl", M.copy_permalink, { 
  desc = "Copy tangled.org permalink",
  silent = true 
})

return M