#include <stdexcept>

#include "escape.h"

static inline const char* get_replacement(char c);

namespace blankie {
namespace html {

std::string escape(const std::string& in) {
    std::string out;
    size_t pos = 0;
    size_t last_pos = 0;

    out.reserve(in.size());
    while ((pos = in.find_first_of("&<>\"'", pos)) != std::string::npos) {
        out.append(in, last_pos, pos - last_pos);
        out.append(get_replacement(in[pos]));
        pos++;
        last_pos = pos;
    }

    if (in.size() > last_pos) {
        out.append(in, last_pos);
    }

    return out;
}

} // namespace html
} // namespace blankie

static inline const char* get_replacement(char c) {
    switch (c) {
        case '&': return "&amp;";
        case '<': return "&lt;";
        case '>': return "&gt;";
        case '"': return "&quot;";
        case '\'': return "&#x27;";
        default: throw std::runtime_error("Encountered unknown replacement character");
    }
}