#include "CLIForge/Levenshtein.hpp"

namespace cliforge::detail
{
	std::size_t levenshtein(const std::string& a, const std::string& b)
	{
		const std::size_t n = a.size(), m = b.size();
		std::vector<std::size_t> prev(m + 1), cur(m + 1);
		for (std::size_t j = 0; j <= m; ++j)
			prev[j] = j;
		for (std::size_t i = 1; i <= n; ++i)
		{
			cur[0] = i;
			for (std::size_t j = 1; j <= m; ++j)
			{
				std::size_t cost = (a[i - 1] == b[j - 1]) ? 0 : 1;
				cur[j] = std::min({prev[j] + 1, cur[j - 1] + 1, prev[j - 1] + cost});
			}
			std::swap(prev, cur);
		}
		return prev[m];
	}

	// Returns up to `limit` candidates from `pool` that are close to `query`,
	// ordered by distance. Anything farther than a generous relative
	// threshold is dropped so we never suggest something wildly unrelated.
	std::vector<std::string> closestMatches(const std::string& query,
											const std::vector<std::string>& pool, std::size_t limit)
	{
		std::vector<std::pair<std::size_t, std::string>> scored;
		scored.reserve(pool.size());
		for (const auto& candidate : pool)
		{
			std::size_t d = levenshtein(query, candidate);
			// A prefix relationship (e.g. "--arch" for "--architectures") is a
			// very strong signal -- treat it as near-identical even though its
			// raw edit distance is large, so common abbreviations still surface.
			if (query.size() >= 2 && candidate.size() > query.size() &&
				candidate.compare(0, query.size(), query) == 0)
			{
				d = std::min<std::size_t>(d, 1);
			}
			scored.emplace_back(d, candidate);
		}
		std::sort(scored.begin(), scored.end(), [](auto& a, auto& b) { return a.first < b.first; });

		std::size_t threshold = std::max<std::size_t>(3, query.size() / 2);
		std::vector<std::string> out;
		for (auto& [dist, name] : scored)
		{
			if (out.size() >= limit)
				break;
			if (dist <= threshold)
				out.push_back(name);
		}
		return out;
	}
}