using InboxIntel.Application.Abstractions;
using InboxIntel.Domain.Enums;
using InboxIntel.Infrastructure.Configuration;
using Microsoft.Extensions.Options;
using System.Linq;
using System.Net.Http.Json;
using System.Text.Json;

namespace InboxIntel.Infrastructure.Ai;

/// <summary>No-op provider used when AI is disabled. Returns empty completions.</summary>
public class NullAiProvider : IAiProvider
{
    public AiProviderMode Mode => AiProviderMode.Disabled;
    public Task<string> CompleteAsync(string systemPrompt, string userPrompt, CancellationToken ct = default)
        => Task.FromResult(string.Empty);
}

/// <summary>No-op embeddings used when AI is disabled. Returns empty vectors so callers fall
/// back to lexical search.</summary>
public class NullEmbeddingProvider : IEmbeddingProvider
{
    public bool IsAvailable => false;
    public Task<float[]> EmbedAsync(string text, CancellationToken ct = default)
        => Task.FromResult(Array.Empty<float>());
    public Task<IReadOnlyList<float[]>> EmbedBatchAsync(IReadOnlyList<string> texts, CancellationToken ct = default)
        => Task.FromResult<IReadOnlyList<float[]>>(Array.Empty<float[]>());
}

/// <summary>Local embeddings via Ollama's /api/embeddings endpoint (e.g. nomic-embed-text).</summary>
public class OllamaEmbeddingProvider : IEmbeddingProvider
{
    private readonly HttpClient _http;
    private readonly AiOptions _options;

    public OllamaEmbeddingProvider(IHttpClientFactory factory, IOptions<AiOptions> options)
    {
        _options = options.Value;
        _http = factory.CreateClient("ollama");
        _http.BaseAddress = new Uri(_options.OllamaBaseUrl);
    }

    public bool IsAvailable => true;

    public async Task<float[]> EmbedAsync(string text, CancellationToken ct = default)
    {
        var payload = new { model = _options.EmbeddingModel, prompt = text };
        var resp = await _http.PostAsJsonAsync("/api/embeddings", payload, ct);
        resp.EnsureSuccessStatusCode();
        using var doc = JsonDocument.Parse(await resp.Content.ReadAsStringAsync(ct));
        return doc.RootElement.GetProperty("embedding").EnumerateArray()
            .Select(e => e.GetSingle()).ToArray();
    }

    // Ollama's /api/embeddings takes one prompt per call, so batch is a sequential loop.
    // Kept behind the interface so a future batch endpoint is a drop-in swap.
    public async Task<IReadOnlyList<float[]>> EmbedBatchAsync(IReadOnlyList<string> texts, CancellationToken ct = default)
    {
        var results = new List<float[]>(texts.Count);
        foreach (var t in texts)
            results.Add(await EmbedAsync(t, ct));
        return results;
    }
}

/// <summary>Local LLM via Ollama's /api/chat endpoint.</summary>
public class OllamaProvider : IAiProvider
{
    private readonly HttpClient _http;
    private readonly AiOptions _options;

    public OllamaProvider(IHttpClientFactory factory, IOptions<AiOptions> options)
    {
        _options = options.Value;
        _http = factory.CreateClient("ollama");
        _http.BaseAddress = new Uri(_options.OllamaBaseUrl);
    }

    public AiProviderMode Mode => AiProviderMode.LocalOllama;

    public async Task<string> CompleteAsync(string systemPrompt, string userPrompt, CancellationToken ct = default)
    {
        var payload = new
        {
            model = _options.OllamaModel,
            stream = false,
            messages = new[]
            {
                new { role = "system", content = systemPrompt },
                new { role = "user", content = userPrompt }
            }
        };
        var resp = await _http.PostAsJsonAsync("/api/chat", payload, ct);
        resp.EnsureSuccessStatusCode();
        using var doc = JsonDocument.Parse(await resp.Content.ReadAsStringAsync(ct));
        return doc.RootElement.GetProperty("message").GetProperty("content").GetString() ?? string.Empty;
    }
}

/// <summary>Cloud LLM via the OpenAI Chat Completions API (optional).</summary>
public class OpenAiProvider : IAiProvider
{
    private readonly HttpClient _http;
    private readonly AiOptions _options;

    public OpenAiProvider(IHttpClientFactory factory, IOptions<AiOptions> options)
    {
        _options = options.Value;
        _http = factory.CreateClient("openai");
        _http.BaseAddress = new Uri("https://api.openai.com");
        _http.DefaultRequestHeaders.Authorization =
            new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", _options.OpenAiApiKey);
    }

    public AiProviderMode Mode => AiProviderMode.CloudOpenAi;

    public async Task<string> CompleteAsync(string systemPrompt, string userPrompt, CancellationToken ct = default)
    {
        var payload = new
        {
            model = _options.OpenAiModel,
            messages = new[]
            {
                new { role = "system", content = systemPrompt },
                new { role = "user", content = userPrompt }
            }
        };
        var resp = await _http.PostAsJsonAsync("/v1/chat/completions", payload, ct);
        resp.EnsureSuccessStatusCode();
        using var doc = JsonDocument.Parse(await resp.Content.ReadAsStringAsync(ct));
        return doc.RootElement.GetProperty("choices")[0].GetProperty("message").GetProperty("content").GetString() ?? string.Empty;
    }
}