using System.Collections.Generic;
using Mono.Cecil;

namespace StardewModdingAPI.Framework.ModLoading
{
    /// <summary>A minimal assembly definition resolver which resolves references to known assemblies.</summary>
    internal class AssemblyDefinitionResolver : IAssemblyResolver
    {
        /*********
        ** Fields
        *********/
        /// <summary>The underlying assembly resolver.</summary>
        private readonly DefaultAssemblyResolverWrapper Resolver = new();

        /// <summary>The known assemblies.</summary>
        private readonly IDictionary<string, AssemblyDefinition> Lookup = new Dictionary<string, AssemblyDefinition>();

        /// <summary>The directory paths to search for assemblies.</summary>
        private readonly HashSet<string> SearchPaths = new();


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        public AssemblyDefinitionResolver()
        {
            foreach (string path in this.Resolver.GetSearchDirectories())
                this.SearchPaths.Add(path);
        }

        /// <summary>Add known assemblies to the resolver.</summary>
        /// <param name="assemblies">The known assemblies.</param>
        public void Add(params AssemblyDefinition[] assemblies)
        {
            foreach (AssemblyDefinition assembly in assemblies)
                this.AddWithExplicitNames(assembly, assembly.Name.Name, assembly.Name.FullName);
        }

        /// <summary>Add a known assembly to the resolver with the given names. This overrides the assembly names that would normally be assigned.</summary>
        /// <param name="assembly">The assembly to add.</param>
        /// <param name="names">The assembly names for which it should be returned.</param>
        public void AddWithExplicitNames(AssemblyDefinition assembly, params string[] names)
        {
            this.Resolver.AddAssembly(assembly);
            foreach (string name in names)
                this.Lookup[name] = assembly;
        }

        /// <summary>Resolve an assembly reference.</summary>
        /// <param name="name">The assembly name.</param>
        /// <exception cref="AssemblyResolutionException">The assembly can't be resolved.</exception>
        public AssemblyDefinition Resolve(AssemblyNameReference name)
        {
            return this.ResolveName(name.Name) ?? this.Resolver.Resolve(name);
        }

        /// <summary>Resolve an assembly reference.</summary>
        /// <param name="name">The assembly name.</param>
        /// <param name="parameters">The assembly reader parameters.</param>
        /// <exception cref="AssemblyResolutionException">The assembly can't be resolved.</exception>
        public AssemblyDefinition Resolve(AssemblyNameReference name, ReaderParameters parameters)
        {
            return this.ResolveName(name.Name) ?? this.Resolver.Resolve(name, parameters);
        }

        /// <summary>Add a directory path to search for assemblies, if it's non-null and not already added.</summary>
        /// <param name="path">The path to search.</param>
        /// <returns>Returns whether the path was successfully added.</returns>
        public bool TryAddSearchDirectory(string? path)
        {
            if (path is not null && this.SearchPaths.Add(path))
            {
                this.Resolver.AddSearchDirectory(path);
                return true;
            }

            return false;
        }

        /// <summary>Remove a directory path to search for assemblies, if it's non-null.</summary>
        /// <param name="path">The path to remove.</param>
        /// <returns>Returns whether the path was in the list and removed.</returns>
        public bool RemoveSearchDirectory(string? path)
        {
            if (path is not null && this.SearchPaths.Remove(path))
            {
                this.Resolver.RemoveSearchDirectory(path);
                return true;
            }

            return false;
        }

        /// <inheritdoc />
        public void Dispose()
        {
            this.Resolver.Dispose();
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Resolve a known assembly definition based on its short or full name.</summary>
        /// <param name="name">The assembly's short or full name.</param>
        private AssemblyDefinition? ResolveName(string name)
        {
            return this.Lookup.TryGetValue(name, out AssemblyDefinition? match)
                ? match
                : null;
        }

        /// <summary>An internal wrapper around <see cref="DefaultAssemblyResolver"/> to allow access to its protected methods.</summary>
        private class DefaultAssemblyResolverWrapper : DefaultAssemblyResolver
        {
            /// <summary>Add an assembly to the resolver.</summary>
            /// <param name="assembly">The assembly to add.</param>
            public void AddAssembly(AssemblyDefinition assembly)
            {
                this.RegisterAssembly(assembly);
            }
        }
    }
}