using System.Net.Http.Headers;
using System.Text.Json;
using System.Text.RegularExpressions;
using CVRManager.Models;

namespace CVRManager.Services;

public class GitHubService
{
    readonly HttpClient http = new();
    readonly Func<string> token;

    public GitHubService(Func<string> token)
    {
        this.token = token;
        http.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("CVRManager", "1.0"));
        http.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/vnd.github+json"));
    }

    public static string? ParseRepo(string input)
    {
        input = input.Trim();
        var m = Regex.Match(input, @"^(?:https?://github\.com/)?([\w.-]+)/([\w.-]+?)(?:\.git)?(?:/.*)?$");
        return m.Success ? $"{m.Groups[1].Value}/{m.Groups[2].Value}" : null;
    }

    HttpRequestMessage Request(string url)
    {
        var req = new HttpRequestMessage(HttpMethod.Get, url);
        var t = token();
        if (!string.IsNullOrWhiteSpace(t)) req.Headers.Authorization = new AuthenticationHeaderValue("Bearer", t);
        return req;
    }

    public async Task<List<ReleaseInfo>> GetReleasesAsync(string repo, CancellationToken ct)
    {
        using var resp = await http.SendAsync(Request($"https://api.github.com/repos/{repo}/releases?per_page=40"), ct);
        if (!resp.IsSuccessStatusCode)
        {
            var hint = (int)resp.StatusCode is 403 or 429 ? " (rate limited: add a GitHub token in Settings)" : "";
            throw new InvalidOperationException($"GitHub returned {(int)resp.StatusCode} for {repo}{hint}.");
        }
        using var doc = JsonDocument.Parse(await resp.Content.ReadAsStringAsync(ct));
        var list = new List<ReleaseInfo>();
        foreach (var r in doc.RootElement.EnumerateArray())
        {
            if (r.GetProperty("draft").GetBoolean()) continue;
            var rel = new ReleaseInfo
            {
                Tag = r.GetProperty("tag_name").GetString() ?? "",
                Prerelease = r.GetProperty("prerelease").GetBoolean(),
                Published = r.TryGetProperty("published_at", out var p) && p.ValueKind == JsonValueKind.String ? p.GetDateTime() : default,
            };
            foreach (var a in r.GetProperty("assets").EnumerateArray())
                rel.Assets.Add(new AssetInfo
                {
                    Name = a.GetProperty("name").GetString() ?? "",
                    Url = a.GetProperty("browser_download_url").GetString() ?? "",
                    Size = a.GetProperty("size").GetInt64(),
                });
            list.Add(rel);
        }
        return list;
    }

    public async Task<ReleaseInfo?> GetMelonLoaderNightlyAsync(CancellationToken ct)
    {
        using var resp = await http.SendAsync(Request(
            "https://api.github.com/repos/LavaGang/MelonLoader/actions/workflows/build.yml/runs?branch=master&status=success&per_page=1"), ct);
        if (!resp.IsSuccessStatusCode) return null;
        using var doc = JsonDocument.Parse(await resp.Content.ReadAsStringAsync(ct));
        var runs = doc.RootElement.GetProperty("workflow_runs");
        if (runs.GetArrayLength() == 0) return null;
        var run = runs[0];
        var sha = run.GetProperty("head_sha").GetString() ?? "";
        var id = run.GetProperty("id").GetInt64();
        var rel = new ReleaseInfo
        {
            Tag = $"nightly-{sha[..Math.Min(7, sha.Length)]}",
            Prerelease = true,
            Published = run.GetProperty("created_at").GetDateTime(),
        };
        rel.Assets.Add(new AssetInfo
        {
            Name = "MelonLoader.x64.zip",
            Url = $"https://nightly.link/LavaGang/MelonLoader/actions/runs/{id}/MelonLoader.Windows.x64.CI.Release.zip",
        });
        return rel;
    }

    public async Task<string> DownloadAsync(string url, string path, CancellationToken ct)
    {
        using var resp = await http.GetAsync(url, HttpCompletionOption.ResponseHeadersRead, ct);
        resp.EnsureSuccessStatusCode();
        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
        await using var src = await resp.Content.ReadAsStreamAsync(ct);
        await using var dst = File.Create(path);
        await src.CopyToAsync(dst, ct);
        var last = resp.RequestMessage?.RequestUri?.Segments.LastOrDefault() ?? "";
        return Uri.UnescapeDataString(last.TrimEnd('/'));
    }
}