using System.Text;
using System.Text.Json;

namespace ClaudeDo.Localization.Tests;

/// <summary>
/// JsonDocument/JsonElement silently keep the last value on a duplicate key instead of throwing,
/// so a repeated top-level block (e.g. two "checks" objects) is invisible to JSON-validity and
/// parity tests alike. This walks the raw token stream instead.
/// </summary>
public class DuplicateLocaleKeysTests
{
    private static string LocalesDir()
    {
        var dir = AppContext.BaseDirectory;
        while (dir is not null)
        {
            var candidate = Path.Combine(dir, "src", "ClaudeDo.Localization", "locales");
            if (Directory.Exists(candidate)) return candidate;
            dir = Path.GetDirectoryName(dir);
        }
        throw new DirectoryNotFoundException("Could not locate src/ClaudeDo.Localization/locales");
    }

    private static List<string> FindDuplicateTopLevelKeys(string json)
    {
        var reader = new Utf8JsonReader(Encoding.UTF8.GetBytes(json));
        var seen = new HashSet<string>(StringComparer.Ordinal);
        var duplicates = new List<string>();
        var depth = 0;

        while (reader.Read())
        {
            switch (reader.TokenType)
            {
                case JsonTokenType.StartObject:
                case JsonTokenType.StartArray:
                    depth++;
                    break;
                case JsonTokenType.EndObject:
                case JsonTokenType.EndArray:
                    depth--;
                    break;
                case JsonTokenType.PropertyName:
                    if (depth == 1)
                    {
                        var name = reader.GetString()!;
                        if (!seen.Add(name)) duplicates.Add(name);
                    }
                    break;
            }
        }

        return duplicates;
    }

    [Fact]
    public void Detects_duplicate_top_level_key_in_fixture()
    {
        const string json = """
        {
          "checks": { "a": "1" },
          "other": { "b": "2" },
          "checks": { "c": "3" }
        }
        """;

        var duplicates = FindDuplicateTopLevelKeys(json);

        Assert.Contains("checks", duplicates);
    }

    [Fact]
    public void Locale_files_have_no_duplicate_top_level_keys()
    {
        var localesDir = LocalesDir();
        foreach (var path in Directory.EnumerateFiles(localesDir, "*.json"))
        {
            var duplicates = FindDuplicateTopLevelKeys(File.ReadAllText(path));
            Assert.True(duplicates.Count == 0,
                $"{Path.GetFileName(path)} has duplicate top-level keys: {string.Join(", ", duplicates)}");
        }
    }
}