module xdiff_mmfile;

import std.exception : enforce;
import xdiff_init : ensureInit, initMmfile;
import xdiff_mmblocks : MMBlocks;
import xdiff;

final class MMFile
{
private:
    mmfile_t _inner;
    bool     _owned = true;

public:
    this()
    {
        _inner = initMmfile(0);
    }

    static MMFile fromBytes(const(ubyte)[] data)
    {
        auto f = new MMFile;
        if (data.length > 0)
        {
            auto wrote = xdl_write_mmfile(&f._inner, data.ptr, cast(long)data.length);
            enforce(wrote == cast(long)data.length, "xdl_write_mmfile wrote less than requested");
        }
        return f;
    }

    ~this()
    {
        if (_owned && _inner.head !is null)
            xdl_free_mmfile(&_inner);

        _inner.head = null; _inner.tail = null;
        _inner.rcur = null; _inner.wcur = null;
        _inner.fsize = 0;   _inner.bsize = 0;
    }

    size_t size()            { return cast(size_t)xdl_mmfile_size(&_inner); }
    bool   isCompact() const { return xdl_mmfile_iscompact(cast(mmfile_t*)&_inner) != 0; }

    const(ubyte)[] asSlice() const
    {
        enforce(isCompact(), "MMFile must be compact for asSlice");
        auto h = _inner.head;
        if (h is null || h.size <= 0) return (cast(ubyte*)null)[0 .. 0];
        return (cast(const(ubyte)*)h.ptr)[0 .. cast(size_t)h.size];
    }

    ubyte[] asSliceMut()
    {
        enforce(isCompact(), "MMFile must be compact for asSliceMut");
        auto h = _inner.head;
        if (h is null || h.size <= 0) return (cast(ubyte*)null)[0 .. 0];
        return (cast(ubyte*)h.ptr)[0 .. cast(size_t)h.size];
    }

    alias MMPatch = MMBlocks;

    /// Сформировать patch (diff self → other)
    MMPatch computePatch(ref MMFile other)
    {
        auto patch = new MMBlocks();

        static extern(C) int emitToPatch(void* priv, mmbuffer_t* bufs, int num)
        {
            auto target = cast(MMBlocks)priv; // класс
            foreach (i; 0 .. num)
            {
                auto b = bufs + i;
                auto wrote = xdl_writem_mmfile(target.mmfilePtr(), b, 1);
                if (wrote != (*b).size) return -1;
            }
            return 0;
        }

        xpparam_t xpp; xpp.flags = 0;
        xdemitconf_t xec; xec.ctxlen = 3;
        xdemitcb_t ecb; ecb.priv = cast(void*)patch; ecb.outf = &emitToPatch;

        auto rc = xdl_diff(&_inner, &other._inner, &xpp, &xec, &ecb);
        enforce(rc == 0, "xdl_diff failed");
        return patch;
    }

    struct PatchResult { bool success; MMFile patched; MMFile rejected; }

    /// Применить patch к self
    PatchResult applyPatch(ref MMPatch patch)
    {
        patch.toCompact();

        auto acc = new MMBlocks();
        auto rej = new MMBlocks();

        static extern(C) int emitTo(void* priv, mmbuffer_t* bufs, int num)
        {
            auto target = cast(MMBlocks)priv; // класс
            long expect = 0; foreach (i; 0 .. num) expect += (bufs + i).size;
            auto wrote = xdl_writem_mmfile(target.mmfilePtr(), bufs, num);
            return (wrote == expect) ? 0 : -1;
        }

        xdemitcb_t accCb; accCb.priv = cast(void*)acc; accCb.outf = &emitTo;
        xdemitcb_t rejCb; rejCb.priv = cast(void*)rej; rejCb.outf = &emitTo;

        auto rc = xdl_patch(&_inner, patch.mmfilePtr(), XDL_PATCH_NORMAL, &accCb, &rejCb);
        enforce(rc == 0 || rc == 1, "xdl_patch failed");

        auto accFile = MMFile.fromBlocksMoved(acc);
        auto rejFile = MMFile.fromBlocksMoved(rej);

        bool ok = (rejFile.size() == 0);
        return PatchResult(ok, accFile, rejFile);
    }

    /// 3-way merge: коллбэки nothrow, чтобы не бросать через C
    void merge3Raw(
        ref MMFile f1,
        ref MMFile f2,
        scope int delegate(const(ubyte)[]) nothrow acceptCb,
        scope int delegate(const(ubyte)[]) nothrow rejectCb)
    {
        static extern(C) int emitAccept(void* priv, mmbuffer_t* bufs, int num)
        {
            auto d = cast(int delegate(const(ubyte)[]) nothrow*)priv;
            foreach (i; 0 .. num)
            {
                auto b = bufs + i;
                auto slice = (cast(const(ubyte)*)((*b).ptr))[0 .. cast(size_t)((*b).size)];
                auto r = (*d)(slice); if (r != 0) return r;
            }
            return 0;
        }
        static extern(C) int emitReject(void* priv, mmbuffer_t* bufs, int num)
        {
            auto d = cast(int delegate(const(ubyte)[]) nothrow*)priv;
            foreach (i; 0 .. num)
            {
                auto b = bufs + i;
                auto slice = (cast(const(ubyte)*)((*b).ptr))[0 .. cast(size_t)((*b).size)];
                auto r = (*d)(slice); if (r != 0) return r;
            }
            return 0;
        }

        auto a = acceptCb, r = rejectCb;
        xdemitcb_t accCb; accCb.priv = cast(void*)&a; accCb.outf = &emitAccept;
        xdemitcb_t rejCb; rejCb.priv = cast(void*)&r; rejCb.outf = &emitReject;

        auto rc = xdl_merge3(&_inner, &f1._inner, &f2._inner, &accCb, &rejCb);
        enforce(rc == 0, "xdl_merge3 failed");
    }

    /// «Move» из MMBlocks: забрать владение внутренними блоками
    static MMFile fromBlocksMoved(MMBlocks b)
    {
        b.toCompact();
        auto f = new MMFile;
        f._inner = *b.mmfilePtr(); // копируем заголовок (указатели на блоки)
        b.disarm();                // источник больше не владеет
        return f;
    }
}