#include "vdm/rules/collision.hpp"

#include <string>
#include <string_view>

namespace vdm::rules {
namespace {

// Split on the last '.', unless it's a leading dot (a dotfile like ".gitignore" has no
// extension by this convention — matches sanitize_filename's own treatment). Returns
// {stem, ext} where `ext` includes the leading '.' when present.
std::pair<std::string_view, std::string_view> split_stem_ext(std::string_view name) {
    auto dot = name.rfind('.');
    if (dot == std::string_view::npos || dot == 0)
        return {name, {}};
    return {name.substr(0, dot), name.substr(dot)};
}

}  // namespace

std::string resolve_collision(std::string_view desired,
                              const std::function<bool(std::string_view)> &exists,
                              CollisionPolicy policy, int max_attempts) {
    if (policy == CollisionPolicy::overwrite)
        return std::string(desired);

    if (!exists || !exists(desired))
        return std::string(desired);

    auto [stem, ext] = split_stem_ext(desired);
    std::string candidate;
    for (int n = 1; n <= max_attempts; ++n) {
        candidate = std::string(stem) + " (" + std::to_string(n) + ")" + std::string(ext);
        if (!exists(candidate))
            return candidate;
    }
    return candidate;  // still colliding; see the header comment on why this isn't hidden
}

}  // namespace vdm::rules