// Assets/_Project/Scripts/Gameplay/Waves/RunDefinition.cs
using System.Collections.Generic;
using System.Text;
using UnityEngine;

namespace TD.Gameplay.Waves
{
    /// <summary>
    /// The whole run: how many waves make a cycle, how many cycles make a phase, and the
    /// per-phase pools everything is drawn from. One asset assigned to <c>RunState</c> in the
    /// match scene; replaces <c>WaveManager</c>'s old flat, hand-ordered wave array.
    /// </summary>
    /// <remarks>
    /// <b>Stable wave ids.</b> Waves are replicated by index into a flat list this asset builds
    /// by walking its phases, groups, and entries in declaration order (see
    /// <see cref="RebuildIndex"/>). Because every peer loads the identical asset, the same walk
    /// produces the same ids everywhere — the same trick the tower catalog and
    /// <c>DraftPool</c> already use, and the reason the server can say "wave slot 2 is wave #7"
    /// in a single int.
    ///
    /// <para><b>The index is frozen for the match.</b> <c>RunState</c> builds it once on spawn
    /// and never rebuilds, so editing this asset mid-play-session cannot renumber ids out from
    /// under in-flight replication. Edit-time changes invalidate the cache normally.</para>
    /// </remarks>
    [CreateAssetMenu(fileName = "RunDefinition", menuName = "TD/Run/Run Definition", order = 12)]
    public class RunDefinition : ScriptableObject
    {
        [Header("Structure")]
        [Tooltip("Waves in one cycle. The phase draws this many distinct-enemy-type waves and " +
                 "replays them every cycle.")]
        [Min(1)]
        public int WavesPerCycle = 5;

        [Tooltip("Cycles before the phase's boss appears. The same drawn waves repeat each " +
                 "cycle, carrying whatever upgrades players voted onto them.")]
        [Min(1)]
        public int CyclesPerPhase = 3;

        [Tooltip("Phases in order. Beating the last phase's boss wins the run. The MVP ships " +
                 "one phase; the full design is three.")]
        public PhaseDefinition[] Phases;

        // ----- Flat wave index (network identity) --------------------------

        // Built lazily and cached. Null means "not built yet". Rebuilt only on explicit request
        // or on edit-time validation — never spontaneously during play, since ids in flight
        // would be invalidated.
        private List<WaveDefinition>            waveIndex;
        private Dictionary<WaveDefinition, int> waveIds;

        /// <summary>Number of distinct waves reachable anywhere in this run.</summary>
        public int WaveCount
        {
            get { EnsureIndex(); return waveIndex.Count; }
        }

        /// <summary>Resolves a replicated wave id back to its asset, or null if out of range.</summary>
        public WaveDefinition GetWave(int waveId)
        {
            EnsureIndex();
            return (waveId >= 0 && waveId < waveIndex.Count) ? waveIndex[waveId] : null;
        }

        /// <summary>Resolves a wave asset to its replicated id.</summary>
        public bool TryGetWaveId(WaveDefinition wave, out int waveId)
        {
            EnsureIndex();
            if (wave != null && waveIds.TryGetValue(wave, out waveId)) return true;
            waveId = -1;
            return false;
        }

        /// <summary>
        /// Rebuilds the flat wave index from the current asset contents. Called once by
        /// <c>RunState</c> on every peer at match start so ids agree, and by the editor when
        /// the asset changes.
        /// </summary>
        public void RebuildIndex()
        {
            waveIndex ??= new List<WaveDefinition>();
            waveIds   ??= new Dictionary<WaveDefinition, int>();
            waveIndex.Clear();
            waveIds.Clear();

            if (Phases == null) return;

            // Declaration-order walk. Every peer runs this over the same asset, so the
            // resulting ids match without any negotiation. Zero-weight entries are indexed
            // too: they can't be drawn, but indexing them keeps ids stable if a designer
            // re-weights between sessions.
            foreach (var phase in Phases)
            {
                if (phase == null) continue;
                IndexGroups(phase.WaveGroups);
                IndexGroups(phase.BossGroups);
            }
        }

        private void IndexGroups(WaveGroup[] groups)
        {
            if (groups == null) return;
            foreach (var group in groups)
            {
                if (group?.Waves == null) continue;
                foreach (var entry in group.Waves)
                {
                    if (entry?.Wave == null) continue;
                    if (waveIds.ContainsKey(entry.Wave)) continue; // first occurrence wins
                    waveIds[entry.Wave] = waveIndex.Count;
                    waveIndex.Add(entry.Wave);
                }
            }
        }

        private void EnsureIndex()
        {
            if (waveIndex == null || waveIds == null) RebuildIndex();
        }

        // ----- Validation --------------------------------------------------

        /// <summary>
        /// Checks that this run can actually be played: at least one phase, every phase able to
        /// fill <see cref="WavesPerCycle"/> slots with distinct enemy types, and every phase able
        /// to produce a boss. Returns true when the run is playable;
        /// <paramref name="report"/> carries the problems either way (it may hold warnings even
        /// on success).
        /// </summary>
        /// <remarks>
        /// The distinct-enemy-type requirement is the one that bites in practice: a phase can
        /// hold twenty waves and still be unplayable if they all point at the same three enemies.
        /// Checking it up front turns that into a startup error instead of a draw that silently
        /// runs short a wave.
        /// </remarks>
        public bool Validate(out string report)
        {
            var sb = new StringBuilder();
            bool ok = true;

            if (Phases == null || Phases.Length == 0)
            {
                sb.AppendLine("• No phases assigned — the run has nothing to play.");
                report = sb.ToString();
                return false;
            }

            var candidates = new List<WavePoolEntry>();

            for (int i = 0; i < Phases.Length; i++)
            {
                var phase = Phases[i];
                string label = phase != null ? phase.Label : $"Phase {i + 1}";

                if (phase == null)
                {
                    sb.AppendLine($"• {label}: slot is empty.");
                    ok = false;
                    continue;
                }

                int distinctTypes = phase.CountDistinctEnemyTypes();
                if (distinctTypes < WavesPerCycle)
                {
                    sb.AppendLine($"• {label}: needs {WavesPerCycle} distinct enemy types to fill " +
                                  $"a cycle but only {distinctTypes} are reachable. Add waves " +
                                  $"using other enemies, or lower Waves Per Cycle.");
                    ok = false;
                }

                phase.CollectBossCandidates(candidates);
                if (candidates.Count == 0)
                {
                    sb.AppendLine($"• {label}: no boss candidates (every boss group is empty, " +
                                  $"unassigned, or entirely zero-weight).");
                    ok = false;
                }

                // Warnings — these don't block a run, they just play oddly.
                phase.CollectWaveCandidates(candidates);
                foreach (var entry in candidates)
                {
                    if (entry.Wave.PrimaryEnemyType == null)
                        sb.AppendLine($"• (warning) {label}: '{entry.Wave.name}' has no usable " +
                                      $"enemy entries and can never be drawn meaningfully.");
                    else if (!entry.Wave.HasSingleEnemyType)
                        sb.AppendLine($"• (warning) {label}: '{entry.Wave.name}' mixes enemy " +
                                      $"types. Upgrades and HUD labels will use " +
                                      $"'{entry.Wave.PrimaryEnemyType.name}' only.");
                }
            }

            report = sb.Length > 0 ? sb.ToString() : "Run structure OK.";
            return ok;
        }

#if UNITY_EDITOR
        private void OnValidate()
        {
            // Only invalidate outside play mode. Clearing the cache mid-match would renumber
            // wave ids while replicated slot references are still pointing at the old numbering.
            if (!Application.isPlaying)
            {
                waveIndex = null;
                waveIds   = null;
            }
        }
#endif
    }
}