using System.Globalization;
using System.Net.Http.Json;
using System.Text.Json;

namespace AnchorCli.OpenRouter;

/// <summary>
/// Fetches and caches model pricing from the OpenRouter API.
/// </summary>
internal sealed class PricingProvider
{
    private const string ModelsUrl = "https://openrouter.ai/api/v1/models";

    private static readonly HttpClient Http = new();
    private Dictionary<string, ModelInfo>? _models;

    /// <summary>
    /// Fetches the full model list from OpenRouter (cached after first call).
    /// </summary>
    public async Task<Dictionary<string, ModelInfo>> GetAllModelsAsync(
        CancellationToken ct = default)
    {
        if (_models != null) return _models;

        var response = await Http.GetAsync(ModelsUrl, ct);
        response.EnsureSuccessStatusCode();

        var json = await response.Content.ReadAsStringAsync(ct);
        var result = JsonSerializer.Deserialize(json, AppJsonContext.Default.ModelsResponse);

        _models = result?.Data?.ToDictionary(m => m.Id) ?? [];
        return _models;
    }

    /// <summary>
    /// Looks up pricing for a specific model ID. Returns null if not found.
    /// </summary>
    public async Task<ModelInfo?> GetModelInfoAsync(
        string modelId, CancellationToken ct = default)
    {
        var models = await GetAllModelsAsync(ct);
        return models.GetValueOrDefault(modelId);
    }

    /// <summary>
    /// Parses a pricing string (USD per token) to decimal. Returns 0 on failure.
    /// </summary>
    public static decimal ParsePrice(string? priceStr) =>
        decimal.TryParse(priceStr, NumberStyles.Float, CultureInfo.InvariantCulture, out var v)
            ? v
            : 0m;
}