using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using FluidSim.Components;
using FluidSim.Interfaces;

namespace FluidSim.Core
{
    public class Solver
    {
        private readonly List<IComponent> _components = new();
        private readonly List<OrificeLink> _orificeLinks = new();
        private readonly List<Junction> _junctions = new();
        private readonly List<OpenEndLink> _openEndLinks = new();

        private double _dt;

        /// <summary>CFL target for sub‑stepping (0.3‑0.8). Lower values are safer for shocks.</summary>
        public double CflTarget { get; set; } = 0.8;

        // ---------- Timing accumulators (reset every LogInterval steps) ----------
        private long _stepCount;
        private double _timeTotal;
        private double _timeCFL;
        private double _timeOrifice;
        private double _timeOpenEnd;
        private double _timeJunction;
        private double _timePipe;
        private double _timeClearGhosts;
        private double _timeUpdateState;

        private const int LogInterval = 5000;   // print once per second (at 44.1 kHz)
        private const bool EnableLogging = false;

        public void SetTimeStep(double dt) => _dt = dt;

        public void AddComponent(IComponent component) => _components.Add(component);
        public void AddOrificeLink(OrificeLink link) => _orificeLinks.Add(link);
        public void AddJunction(Junction junction) => _junctions.Add(junction);
        public void AddOpenEndLink(OpenEndLink link) => _openEndLinks.Add(link);

        public void Step()
        {
            var pipes = _components.OfType<Pipe1D>().ToList();
            if (pipes.Count == 0) return;

            var sw = Stopwatch.StartNew();

            // CFL count
            int nSub = 1;
            foreach (var p in pipes)
                nSub = Math.Max(nSub, p.GetRequiredSubSteps(_dt, CflTarget));
            double dtSub = _dt / nSub;

            _timeCFL += sw.Elapsed.TotalSeconds;

            const int maxSubSteps = 10000;
            if (nSub > maxSubSteps)
            {
                Console.WriteLine($"Warning: required sub‑steps {nSub} exceeds limit. Simulation stopped.");
                return;
            }

            for (int sub = 0; sub < nSub; sub++)
            {
                double t0;

                t0 = sw.Elapsed.TotalSeconds;
                foreach (var link in _orificeLinks)
                    link.Resolve(dtSub);
                _timeOrifice += sw.Elapsed.TotalSeconds - t0;

                t0 = sw.Elapsed.TotalSeconds;
                foreach (var link in _openEndLinks)
                    link.Resolve(dtSub);
                _timeOpenEnd += sw.Elapsed.TotalSeconds - t0;

                t0 = sw.Elapsed.TotalSeconds;
                foreach (var junc in _junctions)
                    junc.Resolve(dtSub);
                _timeJunction += sw.Elapsed.TotalSeconds - t0;

                t0 = sw.Elapsed.TotalSeconds;
                foreach (var p in pipes)
                    p.SimulateSingleStep(dtSub);
                _timePipe += sw.Elapsed.TotalSeconds - t0;
            }

            double tCG = sw.Elapsed.TotalSeconds;
            foreach (var p in pipes)
                p.ClearGhostFlags();
            _timeClearGhosts += sw.Elapsed.TotalSeconds - tCG;

            double tUS = sw.Elapsed.TotalSeconds;
            foreach (var comp in _components)
                comp.UpdateState(_dt);
            _timeUpdateState += sw.Elapsed.TotalSeconds - tUS;

            // accumulate total step time (includes CFL, sub‑steps, clear ghosts, update state)
            _timeTotal += sw.Elapsed.TotalSeconds;

            // ---------- Periodic report ----------
            _stepCount++;
            if (_stepCount % LogInterval == 0 && EnableLogging)
            {
                if (_timeTotal > 0)
                {
                    double totalMs = _timeTotal * 1000.0;
                    double avgUs = (_timeTotal / LogInterval) * 1e6;       // µs per step
                    double stepsPerSec = LogInterval / _timeTotal;        // steps per second

                    Console.WriteLine($"--- Solver timing ({LogInterval} steps) ---");
                    Console.WriteLine($"  Steps per second: {stepsPerSec:F1}");
                    Console.WriteLine($"  Avg step time:    {avgUs:F1} µs  (last nSub = {nSub})");
                    Console.WriteLine($"  CFL calc:         {_timeCFL / _timeTotal * 100:F1} %  ({_timeCFL * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine($"  Sub‑step loop:");
                    Console.WriteLine($"    Orifice:        {_timeOrifice / _timeTotal * 100:F1} %  ({_timeOrifice * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine($"    OpenEnd:        {_timeOpenEnd / _timeTotal * 100:F1} %  ({_timeOpenEnd * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine($"    Junctions:      {_timeJunction / _timeTotal * 100:F1} %  ({_timeJunction * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine($"    Pipe steps:     {_timePipe / _timeTotal * 100:F1} %  ({_timePipe * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine($"  Clear ghosts:     {_timeClearGhosts / _timeTotal * 100:F1} %  ({_timeClearGhosts * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine($"  Update state:     {_timeUpdateState / _timeTotal * 100:F1} %  ({_timeUpdateState * 1e6 / LogInterval:F1} µs/step)");
                    Console.WriteLine();

                    // ---------- Optional detailed pipe profiling ----------
                    if (Pipe1D.EnableDetailedProfiling)
                    {
                        foreach (var pipe in pipes)
                        {
                            Console.WriteLine(pipe.GetDetailProfileReport());
                            pipe.ResetDetailCounters();
                        }
                    }
                }

                // Reset accumulators for next interval
                _timeTotal = 0;
                _timeCFL = 0;
                _timeOrifice = 0;
                _timeOpenEnd = 0;
                _timeJunction = 0;
                _timePipe = 0;
                _timeClearGhosts = 0;
                _timeUpdateState = 0;
            }
        }
    }
}