using System.Text;
using System.Text.Json;
using BlueLaminate.Scraper.Browser;
using BlueLaminate.Scraper.Proxies;
using Microsoft.Extensions.Logging;
using OpenQA.Selenium;

namespace BlueLaminate.Scraper.CsMoney;

/// <summary>Outcome of a stealth pagination run.</summary>
/// <param name="PagesSucceeded">How many offset pages returned listings JSON before stopping.</param>
/// <param name="ItemsTotal">Total listing items captured across those pages.</param>
/// <param name="StoppedReason">Why pagination stopped: "challenged", "empty", "completed", or "error".</param>
public sealed record CsMoneyCaptureResult(int PagesSucceeded, int ItemsTotal, string StoppedReason);

/// <summary>
/// Drives a low-fingerprint, non-headless Edge (no CDP) through a local forwarding
/// proxy to the cs.money market, lets the operator clear Cloudflare once, then pages
/// the listings API with human-like pacing using in-page <c>fetch()</c> calls from
/// the cleared origin (so the cf_clearance cookie rides along). It records each
/// page's JSON and — crucially for the current phase — <b>measures how many pages
/// survive before Cloudflare re-challenges</b>, which tells us whether the
/// fingerprint reductions are enough for a real sweep.
/// </summary>
public sealed class CsMoneyCaptureService
{
    private readonly IProxyProvider _provider;
    private readonly LocalForwardingProxyFactory _proxyFactory;
    private readonly BrowserDriverFactory _factory;
    private readonly CsMoneyOptions _options;
    private readonly ILogger<CsMoneyCaptureService> _logger;

    public CsMoneyCaptureService(
        IProxyProvider provider,
        LocalForwardingProxyFactory proxyFactory,
        BrowserDriverFactory factory,
        CsMoneyOptions options,
        ILogger<CsMoneyCaptureService> logger)
    {
        _provider = provider;
        _proxyFactory = proxyFactory;
        _factory = factory;
        _options = options;
        _logger = logger;
    }

    /// <summary>
    /// Open the market, wait for <paramref name="browseUntilDone"/> (the operator
    /// clears Cloudflare and presses Enter), then page the listings API up to
    /// <paramref name="maxPages"/> times, stopping early on a re-challenge or an
    /// empty page. Each page's body is written to <paramref name="outputDir"/>.
    /// </summary>
    public async Task<CsMoneyCaptureResult> RunAsync(
        string outputDir,
        ProxyRequest request,
        bool loadImages,
        bool useProxy,
        int maxPages,
        Func<Task> browseUntilDone,
        CancellationToken ct = default)
    {
        Directory.CreateDirectory(outputDir);

        // --no-proxy (useProxy=false) drives the automated browser on the machine's
        // own IP, to isolate whether a re-challenge is the IPRoyal exit's reputation
        // or the webdriver fingerprint itself.
        LocalForwardingProxy? localProxy = null;
        string? proxyEndpoint = null;
        if (useProxy)
        {
            var lease = _provider.Acquire(request);
            localProxy = _proxyFactory.Create(lease).Start();
            proxyEndpoint = localProxy.Endpoint;
        }

        var driver = _factory.Create(proxyEndpoint, blockImages: !loadImages, _options.ProfileDir);

        var pages = 0;
        var items = 0;
        var reason = "completed";
        try
        {
            driver.Manage().Timeouts().PageLoad = TimeSpan.FromSeconds(90);
            driver.Manage().Timeouts().AsynchronousJavaScript = TimeSpan.FromSeconds(45);

            _logger.LogInformation("Navigating to {Url}", _options.MarketUrl);
            driver.Navigate().GoToUrl(_options.MarketUrl);

            // Operator clears the Cloudflare challenge in the visible window, waits
            // until the market grid is actually rendered, then presses Enter.
            await browseUntilDone();

            for (var offset = 0; pages < maxPages; offset += 60)
            {
                ct.ThrowIfCancellationRequested();

                var apiUrl = string.Format(_options.ApiUrlTemplate, offset);
                var (status, body) = DirectFetch(driver, apiUrl);

                if (LooksLikeChallenge(status, body))
                {
                    _logger.LogWarning(
                        "Re-challenged at offset {Offset} (after {Pages} clean page(s)). Stopping.",
                        offset, pages);
                    await WriteAsync(outputDir, $"challenge_offset_{offset}.html", body, ct);
                    reason = "challenged";
                    break;
                }

                var count = TryCountItems(body);
                if (count is 0)
                {
                    _logger.LogInformation("Offset {Offset} returned no items — end of listings.", offset);
                    reason = "empty";
                    break;
                }

                await WriteAsync(outputDir, $"page_{pages:D3}_offset_{offset}.json", body, ct);
                pages++;
                items += count ?? 0;
                _logger.LogInformation(
                    "Page {Page} [offset {Offset}] [{Status}] → {Count} items ({Bytes} bytes).",
                    pages, offset, status, count, body.Length);

                await DelayAsync(ct);
            }
        }
        catch (OperationCanceledException)
        {
            reason = "cancelled";
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "cs.money capture failed after {Pages} page(s).", pages);
            reason = "error";
        }
        finally
        {
            driver.Quit();
            if (localProxy is not null)
            {
                await localProxy.DisposeAsync();
            }
        }

        return new CsMoneyCaptureResult(pages, items, reason);
    }

    // Run a same-origin fetch() in the cleared page and return (status, body). Uses
    // ExecuteAsyncScript so we can await the fetch promise; the page is on the
    // cs.money origin, so the cf_clearance cookie is sent automatically.
    private (int Status, string Body) DirectFetch(IWebDriver driver, string apiUrl)
    {
        const string script = """
            const url = arguments[0];
            const done = arguments[arguments.length - 1];
            fetch(url, { credentials: 'include', headers: { 'accept': 'application/json' } })
                .then(r => r.text().then(t => done(JSON.stringify({ status: r.status, body: t }))))
                .catch(e => done(JSON.stringify({ status: -1, body: String(e) })));
            """;
        var raw = ((IJavaScriptExecutor)driver).ExecuteAsyncScript(script, apiUrl) as string;
        if (string.IsNullOrEmpty(raw))
        {
            return (-1, "");
        }

        using var doc = JsonDocument.Parse(raw);
        var status = doc.RootElement.GetProperty("status").GetInt32();
        var body = doc.RootElement.GetProperty("body").GetString() ?? "";
        return (status, body);
    }

    private static bool LooksLikeChallenge(int status, string body) =>
        status is 403 or 503 or -1
        || body.Contains("Just a moment", StringComparison.OrdinalIgnoreCase)
        || body.Contains("challenge-platform", StringComparison.OrdinalIgnoreCase)
        || body.TrimStart().StartsWith("<", StringComparison.Ordinal); // HTML, not JSON

    // Count items[] without binding a full model (the typed model is Phase 2).
    private static int? TryCountItems(string body)
    {
        try
        {
            using var doc = JsonDocument.Parse(body);
            return doc.RootElement.TryGetProperty("items", out var items)
                && items.ValueKind == JsonValueKind.Array
                    ? items.GetArrayLength()
                    : null;
        }
        catch (JsonException)
        {
            return null;
        }
    }

    private async Task DelayAsync(CancellationToken ct)
    {
        var jitter = _options.PageJitterSeconds > 0
            ? Random.Shared.NextDouble() * _options.PageJitterSeconds
            : 0;
        var seconds = Math.Max(0, _options.PageDelaySeconds) + jitter;
        if (seconds > 0)
        {
            await Task.Delay(TimeSpan.FromSeconds(seconds), ct);
        }
    }

    private static async Task WriteAsync(string dir, string fileName, string body, CancellationToken ct) =>
        await File.WriteAllTextAsync(Path.Combine(dir, fileName), body, Encoding.UTF8, ct);
}