using System;
using ProjectM.Simulation;
using Unity.Entities;
using Unity.NetCode;

namespace ProjectM.Server
{
    /// <summary>
    /// Host-only autosave writer. A managed <see cref="SystemBase"/> (file IO =&gt; NO Burst) that reacts to the
    /// <see cref="SaveRequest"/> flag <c>RunDirectorSystem</c> raises on the terminal bank: reads the shared
    /// resource ledger + permanent meta off the director ghost, writes the JSON save (<see cref="SaveService"/>),
    /// then clears the flag. ServerSimulation-only, so a pure (Join) client never writes.
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    public partial class SaveWriteSystem : SystemBase
    {
        protected override void OnCreate()
        {
            RequireForUpdate<SaveRequest>();
            RequireForUpdate<NetworkTime>();
        }

        protected override void OnUpdate()
        {
            var dir = SystemAPI.GetSingletonEntity<SaveRequest>();
            var req = SystemAPI.GetComponent<SaveRequest>(dir);
            if (req.Pending == 0)
                return;

            req.Pending = 0;
            SystemAPI.SetComponent(dir, req);

            // The shared ledger lives on this same director ghost (ResourceLedger-tagged StorageEntry buffer).
            var buffer = SystemAPI.GetBuffer<StorageEntry>(dir);
            var rows = new LedgerRow[buffer.Length];
            for (int i = 0; i < buffer.Length; i++)
                rows[i] = new LedgerRow { ItemId = buffer[i].ItemId, Count = buffer[i].Count };

            // Persist player-built structures (single shared scan; drift-proof vs the quit-to-menu writer).
            uint nowTick = SystemAPI.GetSingleton<NetworkTime>().ServerTick.TickIndexForValidTick;
            SaveStructureScan.Collect(EntityManager, nowTick, out var structures);
            // v6: the permanent-meta slice via the ONE shared collector.
            MetaSaveScan.Collect(EntityManager, dir, out var metaRows, out var runsCompleted, out var maxDepth);

            SaveService.Save(new SaveData
            {
                RunsCompleted = runsCompleted,
                MaxDepthReached = maxDepth,
                MetaUpgrades = metaRows,

                Ledger = rows,
                Structures = structures,
                SavedAtMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
            });
        }
    }
}