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

namespace StellaOps.AdvisoryAI.Hosting;

internal static class GuardrailPhraseLoader
{
    public static IReadOnlyCollection<string> Load(string path)
    {
        if (string.IsNullOrWhiteSpace(path))
        {
            throw new ArgumentException("Guardrail phrase file path must be provided.", nameof(path));
        }

        using var stream = File.OpenRead(path);
        using var document = JsonDocument.Parse(stream);
        var root = document.RootElement;
        return root.ValueKind switch
        {
            JsonValueKind.Array => ExtractValues(root),
            JsonValueKind.Object when root.TryGetProperty("phrases", out var phrases) => ExtractValues(phrases),
            _ => throw new InvalidDataException($"Guardrail phrase file {path} must be a JSON array or object with a phrases array."),
        };
    }

    private static IReadOnlyCollection<string> ExtractValues(JsonElement element)
    {
        var phrases = new List<string>();
        foreach (var item in element.EnumerateArray())
        {
            if (item.ValueKind == JsonValueKind.String)
            {
                var value = item.GetString();
                if (!string.IsNullOrWhiteSpace(value))
                {
                    phrases.Add(value.Trim());
                }
            }
        }

        return phrases;
    }
}