// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Generic;
using System.Diagnostics;

using ILCompiler.DependencyAnalysis.Wasm;
using ILCompiler.DependencyAnalysisFramework;
using Internal.Text;

namespace ILCompiler.DependencyAnalysis
{
    /// <summary>
    /// An abstract assembly stub node whose instances are discoverable by string key.
    /// All instances present in the dependency graph are collected and emitted as a single
    /// READYTORUN_FIXUP_InjectStringThunks eager fixup, mapping each LookupString to
    /// the code address of the stub in the R2R image.
    /// </summary>
    public abstract class StringDiscoverableAssemblyStubNode : AssemblyStubNode
    {
        /// <summary>
        /// The string key used to look up this stub at runtime via LookupPregeneratedThunkByString.
        /// Must be non-empty and must not contain embedded null characters.
        /// </summary>
        public abstract string LookupString { get; }

        protected static string GetLookupString(string prefix, WasmFuncType funcType, bool hasReturnBuffer = false)
        {
            Utf8StringBuilder sb = new Utf8StringBuilder();
            sb.Append(prefix);

            if (funcType.Returns.Types.Length == 0)
            {
                sb.Append('v');
            }
            else
            {
                foreach (WasmValueType type in funcType.Returns.Types)
                {
                    AppendTypeCode(sb, type);
                }
            }

            if (hasReturnBuffer)
            {
                sb.Append('r');
            }

            foreach (WasmValueType type in funcType.Params.Types)
            {
                AppendTypeCode(sb, type);
            }

            return sb.ToString();
        }

        private static void AppendTypeCode(Utf8StringBuilder sb, WasmValueType type)
        {
            sb.Append(type switch
            {
                WasmValueType.I32 => 'i',
                WasmValueType.I64 => 'l',
                WasmValueType.F32 => 'f',
                WasmValueType.F64 => 'd',
                WasmValueType.V128 => 'V',
                _ => throw new UnreachableException(),
            });
        }

        protected override DependencyList ComputeNonRelocationBasedDependencies(NodeFactory factory)
        {
            DependencyList dependencies = new DependencyList();
            dependencies.Add(factory.InjectStringThunksImport, "StringDiscoverableAssemblyStubNode requires InjectStringThunks fixup");

            return dependencies;
        }

        protected override void OnMarked(NodeFactory factory)
        {
            Debug.Assert(!string.IsNullOrEmpty(LookupString), "LookupString must be non-empty");
            Debug.Assert(!LookupString.Contains('\0'), "LookupString must not contain embedded null characters");
            factory.RegisterStringDiscoverableStub(this);
        }
    }
}