local M = {}

M.options = {
    hotkey = "<leader>tq",
    quote_chars = { "'", '"', "`" },
}

---Merges user-provided options with default options.
---@param user_options table|nil User-provided options
function M.setup(user_options)
    if user_options and type(user_options) == "table" then
        for k, v in pairs(user_options) do
            if v ~= nil then
                M.options[k] = v
            end
        end
    end

    local map_opts = {
        desc = "Swaps the quotes around",
        silent = true,
        noremap = true,
    }

    vim.keymap.set("n", M.options.hotkey, M.toggle_quotes, map_opts)
end

--- Checks if a given character is one of the predefined quote characters.
--- @param char string The character to check.
--- @return boolean true if the character is a quote character, false otherwise.
local function is_defined_quote_char(char)
    for _, qc in ipairs(M.options.quote_chars) do
        if char == qc then
            return true
        end
    end
    return false
end

--- Finds the starting and ending indices of a quoted string on the current line
--- that contains the cursor, using a predefined set of quote characters.
--- @param line string The current line of text.
--- @param cursor_col number The column index of the cursor (0-based).
--- @return number start_index The 0-based starting index of the quote, or -1 if not found.
--- @return number end_index The 0-based ending index of the quote, or -1 if not found.
--- @return string current_quote_char The character of the identified quote, or nil.
local function find_quoted_string_at_cursor(line, cursor_col)
    local start_quote_index = -1
    local end_quote_index = -1
    local current_quote_char = nil

    -- Iterate through the line to find a matching pair of quotes that contain the cursor.
    for i = 0, #line - 1 do
        local char = line:sub(i + 1, i + 1)

        if not is_defined_quote_char(char) then
            goto continue_loop -- Not a quote character, skip.
        end

        -- If we haven't found an opening quote yet, this is a potential candidate.
        if start_quote_index == -1 then
            start_quote_index = i
            current_quote_char = char
        elseif char == current_quote_char then
            -- Found a closing quote that matches the current opening quote.
            end_quote_index = i

            -- Check if the cursor is within this identified quoted string (inclusive of quotes).
            if (cursor_col >= start_quote_index and cursor_col <= end_quote_index) or (cursor_col <= start_quote_index and cursor_col <= end_quote_index) then
                return start_quote_index, end_quote_index, current_quote_char
            else
                -- Cursor is not in this string, reset to look for the next potential string.
                start_quote_index = -1
                end_quote_index = -1
                current_quote_char = nil
            end
        end
        ::continue_loop::
    end

    -- No relevant quoted string found that contains the cursor.
    return -1, -1, nil
end

--- Cycles to the next quote character in the predefined list.
--- @param current_char string The current quote character.
--- @return string The next quote character, or nil if current_char is not found.
local function get_next_quote_char(current_char)
    local current_char_list_index = -1
    for i, qc in ipairs(M.options.quote_chars) do
        if qc == current_char then
            current_char_list_index = i
            break
        end
    end

    if current_char_list_index == -1 then
        return nil -- Current character not in our defined list.
    end

    local next_char_list_index = (current_char_list_index % #M.options.quote_chars) + 1
    return M.options.quote_chars[next_char_list_index]
end

--- Toggles the quotes around the string at the cursor position
--- by cycling through a predefined list of quote characters.
function M.toggle_quotes()
    local current_line = vim.api.nvim_get_current_line()
    local cursor_row, cursor_col = unpack(vim.api.nvim_win_get_cursor(0))

    local start_idx, end_idx, current_char =
        find_quoted_string_at_cursor(current_line, cursor_col)

    -- If no quoted string containing the cursor was found, do nothing.
    if start_idx == -1 or end_idx == -1 or not current_char then
        return
    end

    local next_char = get_next_quote_char(current_char)
    if not next_char then
        -- This should ideally not happen if current_char came from find_quoted_string_at_cursor
        -- and QUOTE_CHARS is consistent, but acts as a safeguard.
        return
    end

    -- Reconstruct the line with the new quote characters.
    local new_line =
        current_line:sub(1, start_idx) ..
        next_char ..
        current_line:sub(start_idx + 2, end_idx) ..
        next_char ..
        current_line:sub(end_idx + 2)

    -- Update Neovim's buffer and cursor position.
    vim.api.nvim_set_current_line(new_line)
    vim.api.nvim_win_set_cursor(0, { cursor_row, cursor_col })
end

return M