using CVRManager.Models;

namespace CVRManager.Services;

public record Identified(AssemblyDetails File, string Folder, string Source, string Repo, string AssetName, CvrmgMod? Cvrmg, string Why);

public class ModImportService
{
    static readonly string[] Folders = { "Mods", "Plugins", "UserLibs" };

    readonly GitHubService github;
    readonly CvrmgService cvrmg;
    readonly Dictionary<string, List<ReleaseInfo>> repoReleases = new(StringComparer.OrdinalIgnoreCase);

    public ModImportService(GitHubService github, CvrmgService cvrmg)
    {
        this.github = github;
        this.cvrmg = cvrmg;
    }

    public static string Norm(string s) => CvrmgService.Normalize(s);

    public async Task<List<Identified>> IdentifyAsync(string gameDir, IEnumerable<SourceDef> sources, Action<string> log, CancellationToken ct)
    {
        var files = new List<(AssemblyDetails Details, string Folder)>();
        foreach (var folder in Folders)
        {
            var dir = Path.Combine(gameDir, folder);
            if (!Directory.Exists(dir)) continue;
            foreach (var f in Directory.EnumerateFiles(dir, "*.dll", SearchOption.TopDirectoryOnly).OrderBy(f => f, StringComparer.OrdinalIgnoreCase))
                files.Add((AssemblyReader.Read(f), folder));
            foreach (var sub in Directory.EnumerateDirectories(dir))
                log($"Skipping folder {folder}\\{Path.GetFileName(sub)} (only loose DLLs are imported).");
        }
        log($"Found {files.Count} mod files.");

        List<CvrmgMod> catalog = new();
        try { catalog = await cvrmg.GetAllAsync(ct); }
        catch (Exception e) when (e is not OperationCanceledException) { log($"CVRMG unavailable ({e.Message}); matching without it."); }

        var index = new Dictionary<string, List<(string Repo, string Asset)>>();
        foreach (var src in sources.Where(s => s.Kind == "github" && s.Repo.Length > 0))
        {
            var releases = await ReleasesAsync(src.Repo, log, ct);
            foreach (var r in releases)
                foreach (var a in r.Assets.Where(a => a.Name.EndsWith(".dll", StringComparison.OrdinalIgnoreCase)))
                {
                    var key = Norm(a.Name);
                    if (!index.TryGetValue(key, out var l)) index[key] = l = new();
                    if (l.All(x => !x.Repo.Equals(src.Repo, StringComparison.OrdinalIgnoreCase))) l.Add((src.Repo, a.Name));
                }
        }

        var result = new List<Identified>();
        foreach (var (d, folder) in files)
        {
            ct.ThrowIfCancellationRequested();
            var cm = catalog.FirstOrDefault(m => m.Hash.Length > 0 && m.Hash == d.Sha256);
            var cmWhy = cm != null ? "same file as the current CVRMG release" : "";
            if (cm == null)
            {
                var keys = new[] { d.MelonName, d.AssemblyName, Path.GetFileNameWithoutExtension(d.FileName) }
                    .Select(Norm).Where(k => k.Length > 0).Distinct().ToList();
                cm = catalog.Where(m => new[] { m.Name }.Concat(m.Aliases).Select(Norm).Any(keys.Contains))
                    .OrderBy(m => m.ApprovalStatus == 1 ? 0 : 1).ThenByDescending(m => m.Updated).FirstOrDefault();
                if (cm != null) cmWhy = "name match in CVRMG";
            }

            string? repo = null, asset = null, why = "";
            var link = GitHubService.ParseRepo(d.MelonLink.Contains("github.com", StringComparison.OrdinalIgnoreCase) ? d.MelonLink : "");
            if (link != null)
            {
                var rel = await ReleasesAsync(link, log, ct);
                var hit = rel.SelectMany(r => r.Assets).FirstOrDefault(a => Norm(a.Name) == Norm(d.FileName));
                if (hit != null) { repo = link; asset = hit.Name; why = "download link in the mod's own metadata"; }
            }
            if (repo == null && index.TryGetValue(Norm(d.FileName), out var cands))
            {
                var pick = cands.FirstOrDefault(c => d.MelonAuthor.Length > 0 && c.Repo.Split('/')[0].Equals(d.MelonAuthor, StringComparison.OrdinalIgnoreCase));
                if (pick == default) pick = cands[0];
                repo = pick.Repo;
                asset = pick.Asset;
                why = "release assets of " + repo;
            }

            if (repo != null) result.Add(new Identified(d, folder, "github", repo, asset!, cm, why));
            else if (cm != null) result.Add(new Identified(d, folder, "cvrmg", "", "", cm, cmWhy));
            else result.Add(new Identified(d, folder, "local", "", "", null,
                d.MelonLink.Length > 0 ? $"no published release contains it; its metadata points at {d.MelonLink}" : "no known source"));
        }
        return result;
    }

    public void Invalidate() => repoReleases.Clear();

    public async Task<List<ReleaseInfo>> ReleasesAsync(string repo, Action<string> log, CancellationToken ct, bool force = false)
    {
        if (!force && repoReleases.TryGetValue(repo, out var cached)) return cached;
        var path = Path.Combine(Paths.Root, "sources", "gh_" + Paths.Safe(repo.Replace('/', '_')) + ".json");
        try
        {
            if (!force && File.Exists(path) && DateTime.UtcNow - File.GetLastWriteTimeUtc(path) < TimeSpan.FromHours(1))
            {
                var fromDisk = System.Text.Json.JsonSerializer.Deserialize<List<ReleaseInfo>>(await File.ReadAllTextAsync(path, ct));
                if (fromDisk != null) return repoReleases[repo] = fromDisk;
            }
            var list = await github.GetReleasesAsync(repo, ct);
            Directory.CreateDirectory(Path.GetDirectoryName(path)!);
            await File.WriteAllTextAsync(path, System.Text.Json.JsonSerializer.Serialize(list), ct);
            return repoReleases[repo] = list;
        }
        catch (Exception e) when (e is not OperationCanceledException)
        {
            if (File.Exists(path))
            {
                try
                {
                    var stale = System.Text.Json.JsonSerializer.Deserialize<List<ReleaseInfo>>(await File.ReadAllTextAsync(path, ct));
                    if (stale != null)
                    {
                        log($"{repo}: using cached releases ({e.Message})");
                        return repoReleases[repo] = stale;
                    }
                }
                catch (System.Text.Json.JsonException) { }
            }
            log($"{repo}: {e.Message}");
            return repoReleases[repo] = new();
        }
    }

    public static string SnapshotTag(AssemblyDetails d) =>
        $"installed {d.Version} ({Convert.ToHexString(Convert.FromBase64String(d.Sha256))[..6].ToLowerInvariant()})";

    public int Apply(AppConfig cfg, InstallInfo? install, IEnumerable<Identified> found, Action<string> log, string? gameDir = null)
    {
        var game = gameDir ?? Paths.GameDir(install!);
        var added = 0;
        foreach (var it in found)
        {
            var rel = $"{it.Folder}/{it.File.FileName}";
            if (install != null && install.Deployed.Values.Any(l => l.Contains(rel, StringComparer.OrdinalIgnoreCase))) continue;

            var def = FindOrCreate(cfg, it);
            var tag = SnapshotTag(it.File);
            if (def.Releases.All(r => r.Tag != tag))
                def.Releases.Add(new ReleaseInfo { Tag = tag, Snapshot = true, Published = File.GetLastWriteTime(Path.Combine(game, it.Folder, it.File.FileName)) });

            var filesDir = Paths.ModFilesDir(def, tag);
            if (!ModStore.IsDownloaded(def, tag))
            {
                Directory.CreateDirectory(filesDir);
                File.Copy(Path.Combine(game, it.Folder, it.File.FileName), Path.Combine(filesDir, it.File.FileName), true);
                File.WriteAllText(Path.Combine(Paths.ModVersionDir(def, tag), ".complete"), "");
            }

            if (install != null)
            {
                install.Mods.RemoveAll(a => a.ModId == def.Id);
                install.Mods.Add(new ModAssignment { ModId = def.Id, Version = tag, Enabled = true });
                install.Deployed[def.Id] = ModStore.MapFiles(def, tag).Keys.ToList();
            }
            added++;
            log($"{def.Name} {it.File.Version}: {Describe(it)}");
        }
        return added;
    }

    static string Describe(Identified it) => it.Source switch
    {
        "github" => $"GitHub {it.Repo} ({it.Why})",
        "cvrmg" => $"CVRMG ({it.Why})",
        _ => $"kept as a local snapshot ({it.Why})",
    };

    ModDef FindOrCreate(AppConfig cfg, Identified it)
    {
        ModDef? def = it.Source switch
        {
            "github" => cfg.Mods.FirstOrDefault(m => m.Source == "github" && m.Repo.Equals(it.Repo, StringComparison.OrdinalIgnoreCase) && Norm(m.AssetFilter) == Norm(it.AssetName)),
            "cvrmg" => cfg.Mods.FirstOrDefault(m => m.CvrmgId == it.Cvrmg!.Id && m.Source == "cvrmg"),
            _ => cfg.Mods.FirstOrDefault(m => m.Local && Norm(m.FileName) == Norm(it.File.FileName)),
        };
        if (def != null) return def;

        def = new ModDef
        {
            Name = it.Cvrmg?.Name is { Length: > 0 } n ? n : it.File.MelonName.Length > 0 ? it.File.MelonName : it.File.AssemblyName,
            Type = it.Folder,
            FileName = it.File.FileName,
            Author = it.File.MelonAuthor,
            Source = it.Source,
            Local = it.Source == "local",
        };
        if (it.Cvrmg != null) CvrmgService.ApplyMeta(def, it.Cvrmg);
        if (def.SourceLink.Length == 0 && it.File.MelonLink.Length > 0) def.SourceLink = it.File.MelonLink;
        switch (it.Source)
        {
            case "github":
                def.Repo = it.Repo;
                def.AssetFilter = it.AssetName;
                def.SourceLink = $"https://github.com/{it.Repo}";
                def.Releases = FilterReleases(repoReleases.GetValueOrDefault(it.Repo) ?? new(), def.AssetFilter);
                break;
            case "cvrmg":
                def.Releases = new() { CvrmgService.ToRelease(it.Cvrmg!, it.File.FileName) };
                break;
        }
        cfg.Mods.Add(def);
        return def;
    }

    public static List<ReleaseInfo> FilterReleases(IEnumerable<ReleaseInfo> releases, string assetFilter) =>
        string.IsNullOrWhiteSpace(assetFilter)
            ? releases.ToList()
            : releases.Where(r => r.Assets.Any(a => ModStore.AssetMatches(a.Name, assetFilter))).ToList();
}