using System.Text;
using System.Text.Json.Nodes;
using CareFix.Api.Infrastructure;
using CareFix.Api.Options;
using Microsoft.Extensions.Options;

namespace CareFix.Api.Ai;

/// <summary>Thin client for the Anthropic Messages API with tool use and retries.</summary>
public sealed class ClaudeClient(IHttpClientFactory http, IOptions<CareFixOptions> options, AiUsageService usage, ILogger<ClaudeClient> log)
{
    public const string HttpClientName = "claude";

    public async Task<JsonObject> CreateMessageAsync(JsonArray system, JsonArray? tools, JsonArray messages, CancellationToken ct, int? maxTokens = null, UsageContext? usageContext = null)
    {
        var o = options.Value.Claude;
        if (string.IsNullOrWhiteSpace(o.ApiKey)) throw new AppException(500, "The Claude API key is not configured (CareFix:Claude:ApiKey).");

        var req0 = new JsonObject
        {
            ["model"] = o.Model,
            ["max_tokens"] = maxTokens ?? o.MaxTokens,
            ["system"] = system.DeepClone(),
            ["messages"] = messages.DeepClone(),
        };
        if (tools is { Count: > 0 }) req0["tools"] = tools.DeepClone();
        var body = req0.ToJsonString();

        for (var attempt = 1; ; attempt++)
        {
            using var req = new HttpRequestMessage(HttpMethod.Post, $"{o.BaseUrl.TrimEnd('/')}/v1/messages")
            {
                Content = new StringContent(body, Encoding.UTF8, "application/json"),
            };
            req.Headers.Add("x-api-key", o.ApiKey);
            req.Headers.Add("anthropic-version", "2023-06-01");

            var client = http.CreateClient(HttpClientName);
            HttpResponseMessage resp;
            try { resp = await client.SendAsync(req, ct); }
            catch (HttpRequestException ex) when (attempt < 3)
            {
                log.LogWarning(ex, "Claude request failed, retrying (attempt {Attempt})", attempt);
                await Task.Delay(TimeSpan.FromSeconds(2 * attempt), ct);
                continue;
            }

            using (resp)
            {
                var text = await resp.Content.ReadAsStringAsync(ct);
                if (resp.IsSuccessStatusCode)
                {
                    var parsed = JsonNode.Parse(text)!.AsObject();
                    await usage.RecordAsync(o.Model, parsed["usage"], usageContext, ct);
                    return parsed;
                }

                var code = (int)resp.StatusCode;
                if ((code is 429 or 529 || code >= 500) && attempt < 3)
                {
                    log.LogWarning("Claude returned {Code}, retrying (attempt {Attempt})", code, attempt);
                    await Task.Delay(TimeSpan.FromSeconds(3 * attempt), ct);
                    continue;
                }
                log.LogError("Claude error {Code}: {Body}", code, text);
                throw new AppException(502, $"The AI service returned an error ({code}). Try again in a minute.");
            }
        }
    }
}