using System;
using UnityEngine;
using Object = UnityEngine.Object;

#if UNITY_STANDALONE || UNITY_EDITOR
using System.Collections;
using System.IO;
using UnityEngine.Networking;
#endif

namespace OCES
{
#if UNITY_STANDALONE || UNITY_EDITOR
    /// <summary>
    /// 从 StreamingAssets 加载资源的 IAssetProvider 实现。
    /// 仅支持桌面平台（Windows / macOS / Linux）及 Editor。
    /// 无内置缓存——每次调用都从磁盘读取，缓存由上层 ResourceLoader 负责。
    /// 目前仅支持 AudioClip（.wav 格式）。
    /// </summary>
    public class StreamingAssetProvider : IAssetProvider
    {
        public T Load<T>(string path) where T : Object
        {
            if (typeof(T) != typeof(AudioClip))
            {
                Debug.LogError($"[StreamingAssetProvider] Load<{typeof(T).Name}> 不支持，仅支持 AudioClip");
                return null;
            }

            string fullPath = Path.Combine(Application.streamingAssetsPath, path);
            if (!File.Exists(fullPath))
            {
                Debug.LogError($"[StreamingAssetProvider] 文件 {fullPath} 不存在。");
                return null;
            }

            byte[] wavBytes = File.ReadAllBytes(fullPath);
            AudioClip clip = ParseWav(wavBytes, Path.GetFileNameWithoutExtension(path));
            return clip as T;
        }

        public void LoadAsync<T>(string path, MonoBehaviour coroutineHost, Action<T> onComplete) where T : Object
        {
            coroutineHost.StartCoroutine(LoadAsyncCoroutine(path, onComplete));
        }

        IEnumerator LoadAsyncCoroutine<T>(string path, Action<T> onComplete) where T : Object
        {
            if (typeof(T) != typeof(AudioClip))
            {
                Debug.LogError($"[StreamingAssetProvider] LoadAsync<{typeof(T).Name}> 不支持，仅支持 AudioClip");
                onComplete?.Invoke(null);
                yield break;
            }

            string fullPath = Path.Combine(Application.streamingAssetsPath, path);
            string url = "file://" + fullPath;

            using UnityWebRequest request = UnityWebRequestMultimedia.GetAudioClip(url, AudioType.WAV);
            yield return request.SendWebRequest();

            if (request.result == UnityWebRequest.Result.Success)
            {
                AudioClip clip = DownloadHandlerAudioClip.GetContent(request);
                onComplete?.Invoke(clip as T);
            }
            else
            {
                Debug.LogError($"[StreamingAssetProvider] 加载失败: {url}, 错误: {request.error}");
                onComplete?.Invoke(null);
            }
        }

        // ─────────────────────────────────────────────
        // WAV 解析（PCM 16-bit / 8-bit，单声道 / 立体声）
        // ─────────────────────────────────────────────

        static AudioClip ParseWav(byte[] wavBytes, string clipName)
        {
            int position = 0;

            // RIFF header
            if (wavBytes.Length < 44 ||
                wavBytes[0] != 'R' || wavBytes[1] != 'I' || wavBytes[2] != 'F' || wavBytes[3] != 'F')
            {
                Debug.LogError("[StreamingAssetProvider] 无效的 WAV 文件：缺少 RIFF 头");
                return null;
            }
            position += 4; // "RIFF"
            position += 4; // file size (unused)
            if (wavBytes[8] != 'W' || wavBytes[9] != 'A' || wavBytes[10] != 'V' || wavBytes[11] != 'E')
            {
                Debug.LogError("[StreamingAssetProvider] 无效的 WAV 文件：缺少 WAVE 标识");
                return null;
            }
            position += 4; // "WAVE"

            int channels = 1;
            int sampleRate = 44100;
            int bitsPerSample = 16;
            byte[] pcmData = null;

            // 遍历 chunk
            while (position < wavBytes.Length - 8)
            {
                string chunkId = System.Text.Encoding.ASCII.GetString(wavBytes, position, 4);
                position += 4;
                int chunkSize = BitConverter.ToInt32(wavBytes, position);
                position += 4;

                if (chunkId == "fmt ")
                {
                    int audioFormat = BitConverter.ToInt16(wavBytes, position);
                    if (audioFormat != 1) // PCM = 1
                    {
                        Debug.LogError($"[StreamingAssetProvider] 不支持的音频格式: {audioFormat}，仅支持 PCM");
                        return null;
                    }
                    channels = BitConverter.ToInt16(wavBytes, position + 2);
                    sampleRate = BitConverter.ToInt32(wavBytes, position + 4);
                    bitsPerSample = BitConverter.ToInt16(wavBytes, position + 14);

                    if (channels < 1 || channels > 2)
                    {
                        Debug.LogError($"[StreamingAssetProvider] 不支持的声道数: {channels}");
                        return null;
                    }
                }
                else if (chunkId == "data")
                {
                    pcmData = new byte[chunkSize];
                    Array.Copy(wavBytes, position, pcmData, 0, chunkSize);
                }

                position += chunkSize;
            }

            if (pcmData == null || pcmData.Length == 0)
            {
                Debug.LogError("[StreamingAssetProvider] WAV 文件中未找到 data chunk");
                return null;
            }

            // PCM → float 样本
            int sampleCount = pcmData.Length / (bitsPerSample / 8);
            float[] samples = new float[sampleCount];

            if (bitsPerSample == 16)
            {
                for (int i = 0; i < sampleCount; i++)
                {
                    short sample = BitConverter.ToInt16(pcmData, i * 2);
                    samples[i] = sample / 32768f;
                }
            }
            else if (bitsPerSample == 8)
            {
                for (int i = 0; i < sampleCount; i++)
                {
                    samples[i] = (pcmData[i] - 128f) / 128f;
                }
            }
            else
            {
                Debug.LogError($"[StreamingAssetProvider] 不支持的位深度: {bitsPerSample}");
                return null;
            }

            AudioClip clip = AudioClip.Create(clipName, sampleCount / channels, channels, sampleRate, false);
            clip.SetData(samples, 0);
            return clip;
        }
    }
#else
    /// <summary>
    /// 非桌面平台的桩实现——StreamingAssetProvider 仅支持桌面平台。
    /// </summary>
    public class StreamingAssetProvider : IAssetProvider
    {
        public T Load<T>(string path) where T : Object
        {
            Debug.LogError("[StreamingAssetProvider] 仅支持桌面平台 (Windows/macOS/Linux)");
            return null;
        }

        public void LoadAsync<T>(string path, MonoBehaviour coroutineHost, Action<T> onComplete) where T : Object
        {
            Debug.LogError("[StreamingAssetProvider] 仅支持桌面平台 (Windows/macOS/Linux)");
            onComplete?.Invoke(null);
        }
    }
#endif
}