using System.Text.Json;
using Application.Abstractions.YouTube;
using Microsoft.Extensions.Logging;

namespace Infrastructure.YouTube;

internal sealed class YouTubeApiConnectionTester(
    IHttpClientFactory httpClientFactory,
    ILogger<YouTubeApiConnectionTester> logger
) : IYouTubeApiConnectionTester
{
    public async Task<YouTubeApiTestResult> TestAsync(string testChannelId, CancellationToken ct)
    {
        // "YouTubeApi" 명명 HttpClient = YouTubeApiKeyHandler가 자동으로 ?key= 붙여줌
        var client = httpClientFactory.CreateClient("YouTubeApi");
        var url = $"https://www.googleapis.com/youtube/v3/channels?part=snippet&id={Uri.EscapeDataString(testChannelId)}";

        try
        {
            using var response = await client.GetAsync(url, ct);
            var body = await response.Content.ReadAsStringAsync(ct);
            var status = (int)response.StatusCode;

            if (!response.IsSuccessStatusCode)
            {
                var msg = ExtractGoogleErrorMessage(body) ?? Truncate(body, 300);
                logger.LogWarning("[YouTube] API key test failed: {Status} — {Body}", status, Truncate(body, 500));
                return new YouTubeApiTestResult(
                    Ok: false,
                    HttpStatus: status,
                    ChannelTitle: null,
                    ChannelId: testChannelId,
                    ErrorMessage: $"HTTP {status} {response.StatusCode} — {msg}"
                );
            }

            try
            {
                var doc = JsonSerializer.Deserialize<JsonElement>(body);
                if (!doc.TryGetProperty("items", out var items) || items.GetArrayLength() == 0)
                {
                    return new YouTubeApiTestResult(
                        Ok: false,
                        HttpStatus: status,
                        ChannelTitle: null,
                        ChannelId: testChannelId,
                        ErrorMessage: "응답의 items가 비어있습니다. API Key는 유효하나 채널 조회가 제한됐을 수 있음 (Cloud Console에서 API Key 제한 설정 확인)."
                    );
                }

                var title = items[0].GetProperty("snippet").GetProperty("title").GetString();
                return new YouTubeApiTestResult(
                    Ok: true,
                    HttpStatus: status,
                    ChannelTitle: title,
                    ChannelId: testChannelId,
                    ErrorMessage: null
                );
            }
            catch (JsonException ex)
            {
                return new YouTubeApiTestResult(
                    Ok: false,
                    HttpStatus: status,
                    ChannelTitle: null,
                    ChannelId: testChannelId,
                    ErrorMessage: $"응답 JSON 파싱 실패: {ex.Message}"
                );
            }
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "[YouTube] API key test threw");
            return new YouTubeApiTestResult(
                Ok: false,
                HttpStatus: null,
                ChannelTitle: null,
                ChannelId: testChannelId,
                ErrorMessage: $"요청 실패: {ex.Message}"
            );
        }
    }

    // Google API 에러 응답: { "error": { "code": 403, "message": "...", "errors": [{reason:"keyInvalid"}] } }
    private static string? ExtractGoogleErrorMessage(string body)
    {
        if (string.IsNullOrWhiteSpace(body))
        {
            return null;
        }

        try
        {
            var doc = JsonSerializer.Deserialize<JsonElement>(body);
            if (doc.TryGetProperty("error", out var err))
            {
                var msg = err.TryGetProperty("message", out var m) ? m.GetString() : null;
                var reason = err.TryGetProperty("errors", out var errs) && errs.GetArrayLength() > 0
                    && errs[0].TryGetProperty("reason", out var r) ? r.GetString() : null;

                if (!string.IsNullOrEmpty(msg))
                {
                    return reason is not null ? $"[{reason}] {msg}" : msg;
                }
            }
        }
        catch
        {
            // ignore — fallback to raw body
        }

        return null;
    }

    private static string Truncate(string s, int max) =>
        s.Length <= max ? s : s[..max] + "...";
}