using System.Collections.Generic;
using Microsoft.CodeAnalysis;

namespace Ariadne.Generator
{
    /// <summary>
    /// Holds the analysis of every script class one generator run has needed, so classes whose passages call each
    /// other are each analyzed once.
    /// </summary>
    public class ScriptRegistry
    {
        // A class that isn't a script is held as null.
        private readonly Dictionary<INamedTypeSymbol, ScriptClass> scripts =
            new Dictionary<INamedTypeSymbol, ScriptClass>(SymbolEqualityComparer.Default);

        private readonly Dictionary<ScriptClass, ScriptLocals> locals = new Dictionary<ScriptClass, ScriptLocals>();

        /// <summary>
        /// Records a script that is still being analyzed, so a class it calls into can find it again.
        /// </summary>
        public void Register(ScriptClass script)
        {
            scripts[script.Type] = script;
        }

        /// <summary>
        /// Returns the script <paramref name="type"/> is, or null if it isn't one.  A constructed generic class is the
        /// script of its definition.
        /// </summary>
        public ScriptClass ScriptFor(INamedTypeSymbol type, Compilation compilation)
        {
            type = type.OriginalDefinition;
            ScriptClass returnMe;
            if (!scripts.TryGetValue(type, out returnMe))
            {
                returnMe = ScriptClass.Create(type, compilation, this);
                scripts[type] = returnMe;
            }

            return returnMe;
        }

        /// <summary>
        /// Returns the saved locals of <paramref name="script"/>, working them out and reporting what is wrong with
        /// them to <paramref name="diagnostics"/> the first time.
        /// </summary>
        public ScriptLocals LocalsOf(ScriptClass script, List<Diagnostic> diagnostics)
        {
            ScriptLocals returnMe;
            if (!locals.TryGetValue(script, out returnMe))
            {
                returnMe = ScriptLocals.Find(script, diagnostics);
                locals[script] = returnMe;
            }

            return returnMe;
        }
    }
}