Lumacs/include/lumacs/message_formatter.hpp

#pragma once

#include <string>
#include <cstddef>

namespace lumacs {

/// @brief Shared message formatting utilities for both GTK and TUI frontends.
///
/// This utility provides consistent message formatting including:
/// - Multi-line message collapsing (show first line + count)
/// - Message truncation with help hint
class MessageFormatter {
public:
    /// Truncation suffix shown when message is too long
    static constexpr const char* TRUNCATION_SUFFIX = "... [C-h e]";

    /// @brief Collapse a multi-line message to show only the first line with a count indicator.
    /// @param message The original message (may contain newlines)
    /// @return The collapsed message with line count indicator if multi-line, otherwise unchanged
    static std::string collapse_multiline(const std::string& message) {
        size_t newline_pos = message.find('\n');
        if (newline_pos == std::string::npos) {
            return message;  // Single line, return as-is
        }

        // Count additional lines
        size_t line_count = 1;
        size_t pos = 0;
        while ((pos = message.find('\n', pos)) != std::string::npos) {
            ++line_count;
            ++pos;
        }

        // Return first line with indicator
        return message.substr(0, newline_pos) +
               " [+" + std::to_string(line_count - 1) + " lines, C-h e]";
    }

    /// @brief Truncate a message to fit within a maximum character width.
    /// @param message The message to truncate
    /// @param max_width Maximum number of characters allowed
    /// @return The truncated message with suffix if it was too long, otherwise unchanged
    static std::string truncate_to_width(const std::string& message, size_t max_width) {
        if (message.length() <= max_width) {
            return message;
        }

        const std::string suffix = TRUNCATION_SUFFIX;
        if (max_width <= suffix.length()) {
            return suffix.substr(0, max_width);  // Edge case: very narrow width
        }

        size_t max_chars = max_width - suffix.length();
        return message.substr(0, max_chars) + suffix;
    }

    /// @brief Format a message for display in the echo area.
    /// Combines multi-line collapsing and width truncation.
    /// @param message The original message
    /// @param max_width Maximum display width in characters
    /// @return The formatted message ready for display
    static std::string format_for_echo_area(const std::string& message, size_t max_width) {
        std::string result = collapse_multiline(message);
        return truncate_to_width(result, max_width);
    }
};

} // namespace lumacs