using BoardApp.Config;

namespace BoardApp.Services;

public sealed class UserScenarioService
{
    public const int StaytimeMin = 5;
    public const int StaytimeMax = 86400;

    private readonly BoardConfigLoader _cfg;

    public UserScenarioService(BoardConfigLoader cfg)
    {
        _cfg = cfg;
    }

    private static bool IsValidStaytime(int n) => n >= StaytimeMin && n <= StaytimeMax;

    private Dictionary<string, PageDef> PagesById()
    {
        var cfg = _cfg.LoadPagesConfig();
        var map = new Dictionary<string, PageDef>(StringComparer.Ordinal);
        foreach (var p in cfg.Pages)
        {
            map[p.Id] = p;
        }
        return map;
    }

    private static void EnsureUser(UserScenariosConfig cfg, string username)
    {
        if (!cfg.Users.ContainsKey(username))
        {
            cfg.Users[username] = new UserScenariosUser { Scenarios = new List<UserScenario>() };
        }
    }

    private static string NewScenarioId()
        => $"u_{DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()}_{Guid.NewGuid().ToString("N")[..8]}";

    public List<UserScenario> ListUserScenarios(string username)
    {
        var cfg = _cfg.LoadUserScenariosConfig();
        return cfg.Users.TryGetValue(username, out var u) ? (u.Scenarios ?? new List<UserScenario>()) : new List<UserScenario>();
    }

    public (bool Ok, string? Error) DeleteUserScenario(string username, string scenarioId)
    {
        var cfg = _cfg.LoadUserScenariosConfig();
        EnsureUser(cfg, username);
        var before = cfg.Users[username].Scenarios.Count;
        cfg.Users[username].Scenarios = cfg.Users[username].Scenarios
            .Where(s => !string.Equals(s.Id, scenarioId, StringComparison.Ordinal))
            .ToList();

        if (cfg.Users[username].Scenarios.Count == before)
        {
            return (false, "未找到该场景");
        }

        _cfg.WriteUserScenariosConfig(cfg);
        return (true, null);
    }

    public (bool Ok, UserScenario? Scenario, string? Error) CreateUserScenario(
        string username,
        string name,
        List<ScenarioPageRef> pageRefs)
    {
        var nm = (name ?? "").Trim();
        if (nm.Length == 0) return (false, null, "场景名称不能为空");
        if (pageRefs is null || pageRefs.Count == 0) return (false, null, "至少选择 1 个 page");

        var pages = PagesById();
        foreach (var r in pageRefs)
        {
            if (r is null || string.IsNullOrWhiteSpace(r.PageId) || !pages.ContainsKey(r.PageId))
            {
                return (false, null, $"pageId 不存在：{r?.PageId ?? ""}");
            }
            if (!IsValidStaytime(r.Staytime))
            {
                return (false, null, $"停留时间须为 {StaytimeMin}～{StaytimeMax} 的整数（秒）");
            }
        }

        var cfg = _cfg.LoadUserScenariosConfig();
        EnsureUser(cfg, username);
        var exists = cfg.Users[username].Scenarios.Any(s => string.Equals(s.Name, nm, StringComparison.Ordinal));
        if (exists) return (false, null, "该用户下已存在同名场景");

        var firstPage = pages[pageRefs[0].PageId];
        var scenario = new UserScenario
        {
            Id = NewScenarioId(),
            Name = nm,
            Image = firstPage.Image ?? "",
            Pages = pageRefs,
            CreatedAtMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()
        };

        cfg.Users[username].Scenarios.Insert(0, scenario);
        _cfg.WriteUserScenariosConfig(cfg);
        return (true, scenario, null);
    }
}