-- Create the module table
local M = {}

-- Default configuration
local defaults = {
	filetypes = { "markdown", "text", "norg" }, -- Filetypes to activate the plugin for
}

-- Helper: Parses line details for a given line number (1-based)
-- Returns table: { line = str, indent = str, marker = str|nil, content = str, is_todo = bool } or nil
local function get_line_details(lnum)
  -- Use nvim_buf_get_lines which is 0-indexed for ranges
  local lines = vim.api.nvim_buf_get_lines(0, lnum - 1, lnum, false)
  if not lines or #lines == 0 then return nil end -- Handle potential errors getting line
  local line = lines[1]

  local indent = string.match(line, "^%s*") or ""
  -- Pattern captures marker '-', '*', or '+' followed by at least one space
  -- Returns: indent, marker, space_after_marker
  local marker_pattern = "^(%s*)([%-%*%+])(%s+)"
  -- Pattern captures marker, checkbox '[ ]' or '[x]', and optional space after checkbox
  -- Matches lines like: "- [ ] task", "* [x] task", "+ [ ] task"
  local todo_pattern = "^(%s*[%-%*%+]%s+)%[([ x])%]%s*" -- Capture prefix before checkbox

  local _, marker_match, _ = string.match(line, marker_pattern)
  local is_todo = (string.match(line, todo_pattern) ~= nil)
  local content = ""

  if is_todo then
    -- Content is everything after "[x] " or "[ ] " (including leading space)
    content = string.match(line, todo_pattern .. "(.*)") or ""
  elseif marker_match then
    -- Content is everything after "- " / "* " / "+ "
    content = string.match(line, marker_pattern .. "(.*)") or ""
  else
    -- No list marker, just the trimmed line content
    content = vim.trim(line)
  end

  return {
    line = line,
    indent = indent,
    marker = marker_match, -- '-', '*', '+', or nil
    content = content,
    is_todo = is_todo,
  }
end

-- Helper: Gets details for the current line
local function get_current_line_details()
    local cursor_pos = vim.api.nvim_win_get_cursor(0)
    local lnum = cursor_pos[1] -- 1-based line number
    return get_line_details(lnum), lnum
end

-- <leader>ti: Convert line to TODO, cursor after "] " (Normal mode)
local function add_todo_insert_mode()
    local details, lnum = get_current_line_details()
    -- Don't convert if already a TODO or if getting details failed
    if not details or details.is_todo then return end

    local use_marker = details.marker or "-" -- Default to '-' if no list marker found
    local text_content = details.content -- Content already extracted correctly by get_line_details

    local new_line = details.indent .. use_marker .. " [ ] " .. text_content
    -- Replace current line (lnum is 1-based, set_lines is 0-based)
    vim.api.nvim_buf_set_lines(0, lnum - 1, lnum, false, { new_line })

    -- Set cursor position: 1-based row, 0-based byte column
    -- Position cursor right after the "] "
    local cursor_col_bytes = #(details.indent .. use_marker .. " [ ] ") -- Use Lua # operator
    vim.api.nvim_win_set_cursor(0, { lnum, cursor_col_bytes })
end

-- <leader>ta: Convert line to TODO, cursor at end of line (Normal mode)
local function add_todo_append_mode()
    local details, lnum = get_current_line_details()
    if not details or details.is_todo then return end

    local use_marker = details.marker or "-"
    local text_content = details.content

    local new_line = details.indent .. use_marker .. " [ ] " .. text_content
    vim.api.nvim_buf_set_lines(0, lnum - 1, lnum, false, { new_line })

    -- Set cursor position: 1-based row, 0-based byte column
    -- Position cursor at the very end of the line content
    local cursor_col_bytes = #new_line -- Use Lua # operator
    vim.api.nvim_win_set_cursor(0, { lnum, cursor_col_bytes })
end


-- <leader>to: Insert new TODO line below, cursor after "] " (Normal mode)
local function add_todo_new_line_mode()
    local details, lnum = get_current_line_details()
    if not details then return end -- Should not happen usually, but check anyway

    -- Determine indent and marker based on current line, default to '-' if no marker
    local new_indent = details.indent
    local new_marker = details.marker or "-"

    local new_line_content = new_indent .. new_marker .. " [ ] "
    -- Insert after current line (lnum is 1-based, set_lines is 0-based for ranges)
    vim.api.nvim_buf_set_lines(0, lnum, lnum, false, { new_line_content })

    -- Set cursor position: 1-based row (lnum + 1), 0-based byte column
    -- Position cursor at the end of the new line (after "] ")
    local cursor_col_bytes = #new_line_content -- Use Lua # operator
    vim.api.nvim_win_set_cursor(0, { lnum + 1, cursor_col_bytes })
end

-- Internal function to set up buffer-local keymaps
local function setup_buffer_keymaps()
	-- Handles Enter key press in Insert mode
	local function press_enter()
        local details, lnum = get_current_line_details()
        if not details then
            -- Fallback if getting details fails for some reason
            return vim.api.nvim_replace_termcodes("<CR>", true, false, true)
        end

        -- Check if the line is a TODO item and if it has content after the marker
        local has_content = details.content and not vim.trim(details.content):empty()

        if details.is_todo and has_content then
            -- Case 1: Non-empty TODO line
            -- Create a new TODO line below with same indent/marker
            local new_marker = details.marker or "-" -- Should always have marker if is_todo, but safety check
            local new_line_content = details.indent .. new_marker .. " [ ] "

            -- Insert the new line below the current one
            vim.api.nvim_buf_set_lines(0, lnum, lnum, false, { new_line_content })

            -- Move cursor to the new line, after the "] "
            local cursor_col_bytes = #new_line_content
            vim.api.nvim_win_set_cursor(0, { lnum + 1, cursor_col_bytes })

            -- Action handled, return empty string because mapping is expr=true
            return ""

        elseif details.is_todo and not has_content then
            -- Case 2: Empty TODO line (e.g., "- [ ]")
            -- TODO: Implement Step 3 logic (outdenting) here later.
            -- For now, keep the old (potentially problematic) feedkeys behavior
            -- or simply clear the line and let Neovim handle Enter.
            -- Let's try clearing the line and returning <CR> for now.
            vim.api.nvim_buf_set_lines(0, lnum - 1, lnum, false, { details.indent }) -- Replace with just indent
            return vim.api.nvim_replace_termcodes("<CR>", true, false, true) -- Let Neovim handle newline

            -- Old feedkeys behavior (kept for reference, but commented out):
            -- vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<Esc>S<CR>", true, false, true), "n", false)
            -- return "" -- Feedkeys handles it

        else
            -- Case 3: Not a TODO line
            -- Let Neovim handle the Enter key press normally
            return vim.api.nvim_replace_termcodes("<CR>", true, false, true)
        end
	end

	-- indent line if tab is pressed when line is a todo (Will be refactored in Step 4)
	local function press_tab()
		local current_line = vim.api.nvim_get_current_line()
		-- Check if current line matches the patterns (Only checks '-' marker currently)
        -- TODO: Update pattern to match *, + as well
		local pattern = "^%s*%- %[[ x]%]"
		if string.match(current_line, pattern) then
			-- print("tab pressed, allegedly") -- Removed print
			vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<C-t>", true, false, true), "i", false)
            return "" -- Action handled by feedkeys
		else
            -- Return <Tab> to allow default behavior
            return vim.api.nvim_replace_termcodes("<Tab>", true, false, true)
        end
	end

	-- indent line if shift tab is pressed when line is a todo (Will be refactored in Step 4)
	local function press_shift_tab()
		local current_line = vim.api.nvim_get_current_line()
		-- Check if current line matches the patterns (Only checks '-' marker currently)
        -- TODO: Update pattern to match *, + as well
		local pattern = "^%s*%- %[[ x]%]"
		if string.match(current_line, pattern) then
			-- print("shift tab pressed, allegedly") -- Removed print
			vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<C-d>", true, false, true), "i", false)
            return "" -- Action handled by feedkeys
		else
            -- Return <S-Tab> to allow default behavior
            return vim.api.nvim_replace_termcodes("<S-Tab>", true, false, true)
        end
	end

	-- function that checks if the current line starts with the string "- [ ]" or "- [x]" and toggles the x
    -- (Will be updated in Step 2 to handle *, +)
	local function toggle_todo()
		local openpattern = "%- %[[ ]%]"
		local closedpattern = "%- %[[x]%]"
		local titleopenpattern = "# %[[ ]%]" -- Keep title toggle for now? Or remove? Let's keep it.
		local titleclosedpattern = "# %[[x]%]"

		local line = vim.api.nvim_get_current_line()

		if string.match(line, openpattern) then
			line = string.gsub(line, openpattern, "- [x]", 1) -- Replace only first instance
			vim.api.nvim_set_current_line(line)
		elseif string.match(line, closedpattern) then
			line = string.gsub(line, closedpattern, "- [ ]", 1) -- Replace only first instance
			vim.api.nvim_set_current_line(line)
		elseif string.match(line, titleopenpattern) then
			line = string.gsub(line, titleopenpattern, "# [x]", 1)
			vim.api.nvim_set_current_line(line)
		elseif string.match(line, titleclosedpattern) then
			line = string.gsub(line, titleclosedpattern, "# [ ]", 1)
			vim.api.nvim_set_current_line(line)
		end
	end

	-- Set up buffer-local keymaps
	-- Use buffer = 0 to target the current buffer
	-- Note: Setting expr = true for Tab/S-Tab allows returning keys for default behavior
	vim.keymap.set("n", "<leader>t", function() end, { desc = "+TODOs", buffer = 0 }) -- Placeholder
	vim.keymap.set("i", "<CR>", press_enter, { desc = "Todoer: Handle Enter", expr = true, buffer = 0 })
	vim.keymap.set("i", "<TAB>", press_tab, { desc = "Todoer: Handle Tab", expr = true, buffer = 0 })
	vim.keymap.set("i", "<S-Tab>", press_shift_tab, { desc = "Todoer: Handle Shift-Tab", expr = true, buffer = 0 })
	vim.keymap.set("n", "<leader>tt", toggle_todo, { desc = "Todoer: Toggle TODO", buffer = 0 })
	-- New mappings for adding TODOs
	vim.keymap.set("n", "<leader>ti", add_todo_insert_mode, { desc = "Todoer: Add TODO (cursor after marker)", buffer = 0, silent = true })
	vim.keymap.set("n", "<leader>ta", add_todo_append_mode, { desc = "Todoer: Add TODO (cursor at end)", buffer = 0, silent = true })
	vim.keymap.set("n", "<leader>to", add_todo_new_line_mode, { desc = "Todoer: Add new TODO line below", buffer = 0, silent = true })

	-- Optional: Notify that keymaps are set for this buffer
	-- vim.notify("Todoer keymaps activated for this buffer", vim.log.levels.INFO)
end

-- Setup function: Called by the user in their config
function M.setup(opts)
	-- Merge user options with defaults
	local config = vim.tbl_deep_extend("force", {}, defaults, opts or {})

	-- Create an autocommand group to ensure we can clear it later if needed
	local group = vim.api.nvim_create_augroup("TodoerUserSetup", { clear = true })

	-- Create the autocommand
	vim.api.nvim_create_autocmd("FileType", {
		group = group,
		pattern = config.filetypes, -- Use filetypes from config
		desc = "Setup Todoer keymaps for specific filetypes",
		callback = function()
			-- Call the function that sets up buffer-local keymaps
			setup_buffer_keymaps()
		end,
	})
end

-- Return the module table
return M