// This file is auto-generated by alef — DO NOT EDIT.
// alef:hash:4e15143f4af1ae8bafbdb1506ef057da924484c66a19483966333558ad437e75
// To regenerate: alef generate
// To verify freshness: alef verify --exit-code
// Issues & docs: https://github.com/kreuzberg-dev/alef
#nullable enable

using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace Kreuzberg;

/// <summary>
/// Token usage and cost data for a single LLM call made during extraction.
///
/// Populated when VLM OCR, structured extraction, or LLM-based embeddings
/// are used. Multiple entries may be present when multiple LLM calls occur
/// within one extraction (e.g. VLM OCR + structured extraction).
/// </summary>
public sealed record LlmUsage
{
    /// <summary>
    /// The LLM model identifier (e.g. "openai/gpt-4o", "anthropic/claude-sonnet-4-20250514").
    /// </summary>
    [JsonPropertyName("model")]
    public string Model { get; init; } = "";

    /// <summary>
    /// The pipeline stage that triggered this LLM call
    /// (e.g. "vlm_ocr", "structured_extraction", "embeddings").
    /// </summary>
    [JsonPropertyName("source")]
    public string Source { get; init; } = "";

    /// <summary>
    /// Number of input/prompt tokens consumed.
    /// </summary>
    [JsonPropertyName("input_tokens")]
    public ulong? InputTokens { get; init; } = null;

    /// <summary>
    /// Number of output/completion tokens generated.
    /// </summary>
    [JsonPropertyName("output_tokens")]
    public ulong? OutputTokens { get; init; } = null;

    /// <summary>
    /// Total tokens (input + output).
    /// </summary>
    [JsonPropertyName("total_tokens")]
    public ulong? TotalTokens { get; init; } = null;

    /// <summary>
    /// Estimated cost in USD based on the provider's published pricing.
    /// </summary>
    [JsonPropertyName("estimated_cost")]
    public double? EstimatedCost { get; init; } = null;

    /// <summary>
    /// Why the model stopped generating (e.g. "stop", "length", "content_filter").
    /// </summary>
    [JsonPropertyName("finish_reason")]
    public string? FinishReason { get; init; } = null;


    /// <summary>
    /// Parse a <see cref="LlmUsage"/> from a JSON string.
    /// </summary>
    /// <exception cref="KreuzbergException">When the JSON cannot be deserialised.</exception>
    public static LlmUsage FromJson(string json)
    {
        try
        {
            return JsonSerializer.Deserialize<LlmUsage>(json, JsonOptions)
                ?? throw new KreuzbergException($"Failed to parse LlmUsage from JSON: deserializer returned null");
        }
        catch (KreuzbergException)
        {
            throw;
        }
        catch (Exception e)
        {
            throw new KreuzbergException($"Failed to parse LlmUsage from JSON: {e.Message}", e);
        }
    }

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault,
        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.SnakeCaseLower) },
    };

    /// <summary>Options for serializing config/input objects to FFI. Strips nulls
    /// (nullable C# fields default to null and would override required Rust fields with
    /// non-deserialisable nulls) but preserves explicit false/0 so caller intent is kept.</summary>
    private static readonly JsonSerializerOptions JsonSerializationOptions = new()
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.SnakeCaseLower) },
    };
}
