using System.Diagnostics;
using Microsoft.AspNetCore.Mvc;
using LowLevelGuyCom.Models;

namespace LowLevelGuyCom.Controllers;

public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;
    private const string LanguageCookieName = "site-lang";

    public HomeController(ILogger<HomeController> logger)
    {
        _logger = logger;
    }

    public IActionResult Index()
    {
        return View(UseJapanese() ? "IndexJa" : "Index");
    }

    [Route("ja")]
    public IActionResult IndexJa()
    {
        return Redirect("/?lang=ja");
    }

    [Route("cv")]
    public IActionResult Cv()
    {
        return View(UseJapanese() ? "CvJa" : "Cv");
    }

    [Route("cv/ja")]
    public IActionResult CvJa()
    {
        return Redirect("/cv?lang=ja");
    }

    public IActionResult Privacy()
    {
        return View();
    }

    [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
    public IActionResult Error()
    {
        return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
    }

    private bool UseJapanese()
    {
        string? queryLanguage = Request.Query["lang"].FirstOrDefault();
        if (TryNormalizeLanguage(queryLanguage, out bool queryIsJapanese))
        {
            Response.Cookies.Append(
                LanguageCookieName,
                queryIsJapanese ? "ja" : "en",
                new CookieOptions
                {
                    MaxAge = TimeSpan.FromDays(365),
                    SameSite = SameSiteMode.Lax
                });

            return queryIsJapanese;
        }

        if (TryNormalizeLanguage(Request.Cookies[LanguageCookieName], out bool cookieIsJapanese))
            return cookieIsJapanese;

        return BrowserPrefersJapanese();
    }

    private static bool TryNormalizeLanguage(string? language, out bool isJapanese)
    {
        isJapanese = false;

        if (string.IsNullOrWhiteSpace(language))
            return false;

        string normalized = language.Trim().ToLowerInvariant();
        if (normalized.StartsWith("ja"))
        {
            isJapanese = true;
            return true;
        }

        if (normalized.StartsWith("en"))
        {
            isJapanese = false;
            return true;
        }

        return false;
    }

    private bool BrowserPrefersJapanese()
    {
        string acceptLanguage = Request.Headers.AcceptLanguage.ToString();
        if (string.IsNullOrWhiteSpace(acceptLanguage))
            return false;

        foreach (string segment in acceptLanguage.Split(',', StringSplitOptions.RemoveEmptyEntries))
        {
            string language = segment.Split(';', 2)[0].Trim();
            if (TryNormalizeLanguage(language, out bool isJapanese))
                return isJapanese;
        }

        return false;
    }
}