using System.Net.Http;
using System.Net.Http.Headers;
using System.Text.Json;
using WindowsGotify.Models;

namespace WindowsGotify.Services;

public sealed class GotifyApiService
{
    private readonly AppConfig _config;
    private readonly Logger _logger;
    private readonly HttpClient _httpClient;
    private readonly object _httpLock = new();
    private string _appliedBaseUrl = "";
    private string _appliedToken = "";

    public GotifyApiService(AppConfig config, Logger logger)
    {
        _config = config;
        _logger = logger;
        _httpClient = new HttpClient
        {
            Timeout = TimeSpan.FromSeconds(15)
        };
        SyncAuthHeaders();
    }

    /// <summary>
    /// 检测 URL/Token 是否变了,变了就刷新 HttpClient 的 Authorization。
    /// 注意:HttpClient.BaseAddress 构造后只读,所以我们用绝对 URI 绕过。
    /// </summary>
    private void SyncAuthHeaders()
    {
        var baseUrl = (_config.Gotify.Url ?? "").TrimEnd('/');
        var token = _config.Gotify.ClientToken ?? "";

        if (_appliedBaseUrl == baseUrl && _appliedToken == token)
            return;

        lock (_httpLock)
        {
            if (_appliedBaseUrl == baseUrl && _appliedToken == token)
                return;

            // 显式给默认 header;实际请求走绝对 URI,所以 BaseAddress 永远为空
            _httpClient.DefaultRequestHeaders.Authorization =
                string.IsNullOrEmpty(token) ? null : new AuthenticationHeaderValue("Bearer", token);
            _appliedBaseUrl = baseUrl;
            _appliedToken = token;
        }
    }

    private Uri BuildUri(string path)
    {
        var baseUrl = (_config.Gotify.Url ?? "").TrimEnd('/');
        if (string.IsNullOrEmpty(baseUrl))
            throw new InvalidOperationException("Gotify URL 未配置。请在主窗填入 URL 并保存。");
        return new Uri(baseUrl + "/" + path);
    }

    /// <summary>
    /// 拉取 lastId 之后的增量消息(去重补齐用)。
    /// </summary>
    public async Task<List<GotifyMessage>> GetMessagesSinceAsync(long sinceId, int limit, CancellationToken ct)
    {
        SyncAuthHeaders();
        var path = $"message?limit={Math.Clamp(limit, 1, 100)}&since={Math.Max(0, sinceId)}";
        using var response = await _httpClient.GetAsync(BuildUri(path), ct);
        response.EnsureSuccessStatusCode();

        await using var stream = await response.Content.ReadAsStreamAsync(ct);
        var page = await JsonSerializer.DeserializeAsync<GotifyMessagePage>(stream, cancellationToken: ct);
        return page?.Messages ?? new List<GotifyMessage>();
    }

    /// <summary>
    /// 拉取最近 N 条消息(历史查看用)。since=0 让服务器从最新往旧返回。
    /// </summary>
    public async Task<List<GotifyMessage>> GetRecentMessagesAsync(int limit, CancellationToken ct)
    {
        SyncAuthHeaders();
        var path = $"message?limit={Math.Clamp(limit, 1, 100)}&since=0";
        using var response = await _httpClient.GetAsync(BuildUri(path), ct);
        response.EnsureSuccessStatusCode();

        await using var stream = await response.Content.ReadAsStreamAsync(ct);
        var page = await JsonSerializer.DeserializeAsync<GotifyMessagePage>(stream, cancellationToken: ct);
        var list = page?.Messages ?? new List<GotifyMessage>();

        // Gotify 的 since=0 行为:返回数据库里所有消息中的 limit 条;按 id 降序再取一次保证正确
        return list.OrderByDescending(m => m.Id).Take(Math.Clamp(limit, 1, 100)).ToList();
    }

    /// <summary>
    /// 拉取所有 Gotify Application,供 UI 用来把消息 AppId 解析为应用名。
    /// </summary>
    public async Task<List<GotifyApplication>> GetApplicationsAsync(CancellationToken ct)
    {
        SyncAuthHeaders();
        var path = "application?limit=999";
        using var response = await _httpClient.GetAsync(BuildUri(path), ct);
        response.EnsureSuccessStatusCode();

        await using var stream = await response.Content.ReadAsStreamAsync(ct);
        var list = await JsonSerializer.DeserializeAsync<List<GotifyApplication>>(stream, cancellationToken: ct);
        return list ?? new List<GotifyApplication>();
    }
}