// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include "implicit_levenshtein_dfa.hpp"
#include "unicode_utils.h"
#include <cassert>

namespace vespalib::fuzzy {

/**
 * Builds two separate vectors that exist alongside the (possibly case-normalized) UTF-32
 * target string:
 *
 *   - The UTF-8 representation of the (possibly case-normalized) target string
 *   - An offset vector that maps each UTF-32 string index to the first byte of the
 *     equivalent UTF-8 character.
 *
 * These are used for efficiently dumping an UTF-8 target string suffix from an UTF-32
 * target string index.
 */
template <typename Traits>
void ImplicitLevenshteinDfa<Traits>::precompute_utf8_target_with_offsets() {
    _target_utf8_char_offsets.reserve(_u32_str_buf.size());
    _target_as_utf8.reserve(_u32_str_buf.size()); // Under-reserves for all non-ASCII (TODO count via simdutf?)
    // Important: the precomputed UTF-8 target is based on the potentially case-normalized
    // target string, ensuring that we don't emit raw target chars for uncased successors.
    for (uint32_t u32ch : _u32_str_buf) {
        _target_utf8_char_offsets.emplace_back(static_cast<uint32_t>(_target_as_utf8.size()));
        append_utf32_char(_target_as_utf8, u32ch);
    }
    assert(_target_as_utf8.size() < UINT32_MAX);
}

template class ImplicitLevenshteinDfa<FixedMaxEditDistanceTraits<1>>;
template class ImplicitLevenshteinDfa<FixedMaxEditDistanceTraits<2>>;

}