using System;
using System.Collections.Generic;
using System.IO;
using UnityEngine;

public static class DlcManifestService
{
    private static readonly string[] ManifestFilePatterns =
    {
        "*.json"
    };

    private const string RuntimeFolderName = "DLC";
    private const string ManifestFolderName = "manifests";

    public static List<DlcManifestRuntimeEntry> LoadInstalledEntries()
    {
        DlcPackageArchiveService.PrepareInstalledPackages();

        List<DlcManifestRuntimeEntry> result = new List<DlcManifestRuntimeEntry>();
        HashSet<string> visitedFiles = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        string[] roots = GetManifestSearchRoots();

        for (int i = 0; i < roots.Length; i++)
        {
            string root = roots[i];
            if (string.IsNullOrWhiteSpace(root) || !Directory.Exists(root))
            {
                continue;
            }

            CollectManifestEntries(root, result, visitedFiles);
        }

        return result;
    }

    public static string[] GetManifestSearchRoots()
    {
        List<string> result = new List<string>();
        AppendIfValid(result, Path.Combine(Application.streamingAssetsPath, RuntimeFolderName, ManifestFolderName));
        AppendIfValid(result, Path.Combine(Application.streamingAssetsPath, RuntimeFolderName));
        AppendIfValid(result, Path.Combine(Application.persistentDataPath, RuntimeFolderName, ManifestFolderName));
        AppendIfValid(result, Path.Combine(Application.persistentDataPath, RuntimeFolderName));

#if !UNITY_ANDROID
        // 项目外（可执行文件同级目录）的 DLC 扫描仅在 PC 端有意义；
        // 安卓无此目录概念，Application.dataPath 指向 APK，跳过以避免无效/异常路径。
        string playerRoot = GetPlayerRootDirectory();
        AppendIfValid(result, Path.Combine(playerRoot, RuntimeFolderName, ManifestFolderName));
        AppendIfValid(result, Path.Combine(playerRoot, RuntimeFolderName));
#endif

        return result.ToArray();
    }

    public static DlcManifestFile ParseManifestJson(string json)
    {
        if (string.IsNullOrWhiteSpace(json))
        {
            return null;
        }

        try
        {
            return JsonUtility.FromJson<DlcManifestFile>(json);
        }
        catch (Exception ex)
        {
            Debug.LogWarning("[DLC] Failed to parse manifest json: " + ex.Message);
            return null;
        }
    }

    private static void CollectManifestEntries(
        string root,
        List<DlcManifestRuntimeEntry> result,
        HashSet<string> visitedFiles)
    {
        for (int patternIndex = 0; patternIndex < ManifestFilePatterns.Length; patternIndex++)
        {
            string pattern = ManifestFilePatterns[patternIndex];
            string[] files;
            try
            {
                files = Directory.GetFiles(root, pattern, SearchOption.AllDirectories);
            }
            catch (Exception ex)
            {
                Debug.LogWarning("[DLC] Failed to enumerate manifest files in '" + root + "': " + ex.Message);
                continue;
            }

            for (int i = 0; i < files.Length; i++)
            {
                string manifestPath = files[i];
                if (string.IsNullOrWhiteSpace(manifestPath))
                {
                    continue;
                }

                string fullPath = Path.GetFullPath(manifestPath);
                if (!visitedFiles.Add(fullPath))
                {
                    continue;
                }

                TryLoadManifestFile(fullPath, result);
            }
        }
    }

    private static void TryLoadManifestFile(string manifestPath, List<DlcManifestRuntimeEntry> result)
    {
        try
        {
            string json = File.ReadAllText(manifestPath);
            DlcManifestFile file = ParseManifestJson(json);
            if (file == null || file.entries == null || file.entries.Count == 0)
            {
                return;
            }

            string manifestDirectory = Path.GetDirectoryName(manifestPath) ?? string.Empty;
            string manifestId = string.IsNullOrWhiteSpace(file.manifestId)
                ? Path.GetFileNameWithoutExtension(manifestPath)
                : file.manifestId.Trim();

            for (int i = 0; i < file.entries.Count; i++)
            {
                DlcManifestEntry entry = file.entries[i];
                if (entry == null || !entry.enabled)
                {
                    continue;
                }

                string resolvedCatalogPath = ResolveCatalogPath(entry.catalogPath, manifestDirectory);
                if (string.IsNullOrWhiteSpace(resolvedCatalogPath))
                {
                    Debug.LogWarning("[DLC] Manifest entry '" + manifestId + "' has no valid catalogPath.");
                    continue;
                }

                result.Add(new DlcManifestRuntimeEntry
                {
                    manifestId = manifestId,
                    manifestSourcePath = manifestPath,
                    manifestDirectory = manifestDirectory,
                    entry = entry,
                    resolvedCatalogPath = resolvedCatalogPath
                });
            }
        }
        catch (Exception ex)
        {
            Debug.LogWarning("[DLC] Failed to load manifest '" + manifestPath + "': " + ex.Message);
        }
    }

    private static string ResolveCatalogPath(string catalogPath, string manifestDirectory)
    {
        if (string.IsNullOrWhiteSpace(catalogPath))
        {
            return string.Empty;
        }

        string trimmed = catalogPath.Trim();
        if (trimmed.StartsWith("http://", StringComparison.OrdinalIgnoreCase) ||
            trimmed.StartsWith("https://", StringComparison.OrdinalIgnoreCase) ||
            trimmed.StartsWith("file://", StringComparison.OrdinalIgnoreCase))
        {
            return trimmed;
        }

        string combined = trimmed;
        if (!Path.IsPathRooted(combined))
        {
            combined = Path.Combine(manifestDirectory ?? string.Empty, combined);
        }

        try
        {
            return new Uri(Path.GetFullPath(combined)).AbsoluteUri;
        }
        catch
        {
            return string.Empty;
        }
    }

    private static string GetPlayerRootDirectory()
    {
        try
        {
            string dataPath = Application.dataPath;
            if (string.IsNullOrWhiteSpace(dataPath))
            {
                return string.Empty;
            }

            DirectoryInfo parent = Directory.GetParent(dataPath);
            return parent != null ? parent.FullName : string.Empty;
        }
        catch
        {
            return string.Empty;
        }
    }

    private static void AppendIfValid(List<string> result, string path)
    {
        if (result == null || string.IsNullOrWhiteSpace(path))
        {
            return;
        }

        string fullPath;
        try
        {
            fullPath = Path.GetFullPath(path);
        }
        catch
        {
            return;
        }

        if (!result.Contains(fullPath))
        {
            result.Add(fullPath);
        }
    }
}