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

namespace BlueLaminate.Scraper.Proxies;

/// <summary>The exit IP a proxy lease actually resolves to, per ipinfo.io.</summary>
/// <param name="Org">
/// ASN + organisation, e.g. "AS7922 Comcast Cable". This is the tell for
/// residential vs. datacenter: a consumer ISP here means a real residential
/// exit; a hosting provider (OVH, Hetzner, AWS…) means datacenter dressed up.
/// </param>
public sealed record ProxyExitInfo(
    string? Ip,
    string? City,
    string? Region,
    string? Country,
    string? Org,
    string? Hostname,
    string? Timezone);

/// <summary>
/// Smallest possible end-to-end check of the proxy plumbing: acquire a lease,
/// launch the real browser through it, and read back the exit IP from an
/// IP-echo endpoint. Costs a few KB, so it's the right first thing to run
/// against a metered residential plan — it proves auth works and shows whether
/// the IP is genuinely residential before we spend bandwidth on CSFloat.
/// </summary>
public sealed class ProxyProbe
{
    private const string IpEchoUrl = "https://ipinfo.io/json";

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true,
    };

    private readonly IProxyProvider _provider;
    private readonly LocalForwardingProxyFactory _proxyFactory;
    private readonly BrowserDriverFactory _factory;
    private readonly ILogger<ProxyProbe> _logger;

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

    public async Task<ProxyExitInfo> RunAsync(ProxyRequest request)
    {
        var lease = _provider.Acquire(request);
        _logger.LogInformation(
            "Acquired {Provider} lease (exit {Mode}).",
            lease.Provider, lease.SessionId is null ? "rotating" : $"sticky:{lease.SessionId}");

        await using var localProxy = _proxyFactory.Create(lease).Start();
        var driver = _factory.Create(localProxy.Endpoint, blockImages: true);
        try
        {
            driver.Manage().Timeouts().PageLoad = TimeSpan.FromSeconds(60);
            driver.Navigate().GoToUrl(IpEchoUrl);

            // Read the document's text rather than the DOM so the browser's
            // built-in JSON viewer doesn't get in the way, then carve out the
            // JSON object it rendered.
            var rendered = ((IJavaScriptExecutor)driver)
                .ExecuteScript("return document.documentElement.innerText;") as string
                ?? throw new InvalidOperationException("Browser returned no page text.");

            var info = JsonSerializer.Deserialize<ProxyExitInfo>(ExtractJson(rendered), JsonOptions)
                ?? throw new InvalidOperationException("IP-echo response was empty.");

            _logger.LogInformation(
                "Exit IP {Ip} — {City}, {Region}, {Country} — {Org}",
                info.Ip, info.City, info.Region, info.Country, info.Org);

            return info;
        }
        finally
        {
            driver.Quit();
        }
    }

    private static string ExtractJson(string text)
    {
        var start = text.IndexOf('{');
        var end = text.LastIndexOf('}');
        if (start < 0 || end <= start)
        {
            throw new InvalidOperationException($"No JSON found in IP-echo response: {text}");
        }

        return text[start..(end + 1)];
    }
}