// v1.11 Phase B — binary in-memory document storage backed by yyjson mut_doc.
//
// All yyjson includes are confined to this translation unit; the public
// header forward-declares yyjson_mut_doc / yyjson_mut_val so callsites stay
// yyjson-agnostic.

#include "doc_binary.hpp"

#include <yyjson.h>

#include <cstdlib>
#include <new>
#include <string>
#include <utility>

namespace smartbotic::db::doc_binary {

namespace {

// Build a yyjson_mut_val for `j` inside `doc`. Returns nullptr on allocator
// failure; the caller treats nullptr as bad_alloc.
yyjson_mut_val* build_value(yyjson_mut_doc* doc, const nlohmann::json& j) {
    using value_t = nlohmann::detail::value_t;
    switch (j.type()) {
        case value_t::null:
            return yyjson_mut_null(doc);
        case value_t::boolean:
            return yyjson_mut_bool(doc, j.get<bool>());
        case value_t::number_integer:
            return yyjson_mut_sint(doc, j.get<int64_t>());
        case value_t::number_unsigned:
            return yyjson_mut_uint(doc, j.get<uint64_t>());
        case value_t::number_float:
            return yyjson_mut_real(doc, j.get<double>());
        case value_t::string: {
            const std::string& s = j.get_ref<const std::string&>();
            return yyjson_mut_strncpy(doc, s.data(), s.size());
        }
        case value_t::array: {
            yyjson_mut_val* arr = yyjson_mut_arr(doc);
            if (!arr) return nullptr;
            for (const auto& elem : j) {
                yyjson_mut_val* v = build_value(doc, elem);
                if (!v) return nullptr;
                if (!yyjson_mut_arr_add_val(arr, v)) return nullptr;
            }
            return arr;
        }
        case value_t::object: {
            yyjson_mut_val* obj = yyjson_mut_obj(doc);
            if (!obj) return nullptr;
            for (auto it = j.begin(); it != j.end(); ++it) {
                const std::string& key = it.key();
                yyjson_mut_val* k = yyjson_mut_strncpy(doc, key.data(), key.size());
                if (!k) return nullptr;
                yyjson_mut_val* v = build_value(doc, it.value());
                if (!v) return nullptr;
                if (!yyjson_mut_obj_add(obj, k, v)) return nullptr;
            }
            return obj;
        }
        case value_t::binary:
            // nlohmann's binary type has no direct JSON mapping; fall through
            // to null. No production callsite uses binary().
            return yyjson_mut_null(doc);
        case value_t::discarded:
        default:
            return yyjson_mut_null(doc);
    }
}

// Convert a yyjson_mut_val back into an nlohmann::json. Mirrors json_parse.cpp
// but operates on the mut tree.
nlohmann::json convert_to_nlohmann(yyjson_mut_val* v) {
    if (!v) {
        return nullptr;
    }
    switch (yyjson_mut_get_type(v)) {
        case YYJSON_TYPE_NULL:
            return nullptr;
        case YYJSON_TYPE_BOOL:
            return yyjson_mut_get_bool(v);
        case YYJSON_TYPE_NUM:
            switch (yyjson_mut_get_subtype(v)) {
                case YYJSON_SUBTYPE_UINT:
                    return yyjson_mut_get_uint(v);
                case YYJSON_SUBTYPE_SINT:
                    return yyjson_mut_get_sint(v);
                case YYJSON_SUBTYPE_REAL:
                default:
                    return yyjson_mut_get_real(v);
            }
        case YYJSON_TYPE_STR:
            return std::string(yyjson_mut_get_str(v), yyjson_mut_get_len(v));
        case YYJSON_TYPE_ARR: {
            nlohmann::json out = nlohmann::json::array();
            size_t idx = 0, max = 0;
            yyjson_mut_val* elem = nullptr;
            yyjson_mut_arr_foreach(v, idx, max, elem) {
                out.push_back(convert_to_nlohmann(elem));
            }
            return out;
        }
        case YYJSON_TYPE_OBJ: {
            nlohmann::json out = nlohmann::json::object();
            size_t idx = 0, max = 0;
            yyjson_mut_val* key = nullptr;
            yyjson_mut_val* val = nullptr;
            yyjson_mut_obj_foreach(v, idx, max, key, val) {
                out[std::string(yyjson_mut_get_str(key), yyjson_mut_get_len(key))] =
                    convert_to_nlohmann(val);
            }
            return out;
        }
        default:
            return nullptr;
    }
}

// RAII guard for the malloc'd buffer returned by yyjson_mut_write.
struct WriteBuf {
    char* data = nullptr;
    ~WriteBuf() {
        if (data) {
            std::free(data);
        }
    }
};

}  // namespace

// ---------------- Doc ----------------

Doc::Doc(yyjson_mut_doc* doc) : doc_(doc) {}

Doc::Doc(Doc&& other) noexcept : doc_(other.doc_) {
    other.doc_ = nullptr;
}

Doc& Doc::operator=(Doc&& other) noexcept {
    if (this != &other) {
        if (doc_) {
            yyjson_mut_doc_free(doc_);
        }
        doc_ = other.doc_;
        other.doc_ = nullptr;
    }
    return *this;
}

Doc::~Doc() {
    if (doc_) {
        yyjson_mut_doc_free(doc_);
        doc_ = nullptr;
    }
}

bool Doc::empty() const noexcept {
    return doc_ == nullptr;
}

yyjson_mut_val* Doc::root() const noexcept {
    if (!doc_) return nullptr;
    return yyjson_mut_doc_get_root(doc_);
}

yyjson_mut_doc* Doc::raw() const noexcept {
    return doc_;
}

// ---------------- free functions ----------------

Doc encode(const nlohmann::json& j) {
    yyjson_mut_doc* doc = yyjson_mut_doc_new(nullptr);
    if (!doc) {
        throw std::bad_alloc();
    }
    yyjson_mut_val* root = build_value(doc, j);
    if (!root) {
        yyjson_mut_doc_free(doc);
        throw std::bad_alloc();
    }
    yyjson_mut_doc_set_root(doc, root);
    return Doc(doc);
}

nlohmann::json decode(const Doc& doc) {
    if (doc.empty()) {
        return nlohmann::json(nullptr);
    }
    return convert_to_nlohmann(doc.root());
}

std::optional<nlohmann::json> get_field(const Doc& doc, std::string_view field_name) {
    if (doc.empty()) {
        return std::nullopt;
    }
    yyjson_mut_val* root = doc.root();
    if (!root || yyjson_mut_get_type(root) != YYJSON_TYPE_OBJ) {
        return std::nullopt;
    }
    // yyjson_mut_obj_getn does NOT require a null-terminated key — it takes
    // explicit length, so std::string_view's non-terminated buffer is safe.
    yyjson_mut_val* v = yyjson_mut_obj_getn(root, field_name.data(), field_name.size());
    if (!v) {
        return std::nullopt;
    }
    return convert_to_nlohmann(v);
}

std::string to_json_text(const Doc& doc) {
    if (doc.empty()) {
        return "null";
    }
    size_t len = 0;
    WriteBuf buf;
    buf.data = yyjson_mut_write(doc.raw(), 0, &len);
    if (!buf.data) {
        throw std::bad_alloc();
    }
    return std::string(buf.data, len);
}

}  // namespace smartbotic::db::doc_binary