using System;
using System.Collections.Generic;
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;

        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;

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

            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++)
            {
                foreach (var link in _orificeLinks)
                    link.Resolve(dtSub);
                foreach (var link in _openEndLinks)
                    link.Resolve(dtSub);
                foreach (var junc in _junctions)
                    junc.Resolve(dtSub);
                foreach (var p in pipes)
                    p.SimulateSingleStep(dtSub);
            }

            foreach (var p in pipes)
                p.ClearGhostFlags();

            foreach (var comp in _components)
                comp.UpdateState(_dt);
        }
    }
}