using AvParser.Core.Parsing;

namespace AvParser.Core.Tests;

/// <summary>Collection helpers so the tests read as assertions rather than as loops.</summary>
internal static class ParserTestExtensions
{
    /// <summary>
    /// Drains a parse into memory, using the ambient test cancellation token.
    /// </summary>
    /// <remarks>
    /// Deliberately takes no <see cref="CancellationToken"/>: every call site would otherwise have
    /// to pass <c>TestContext.Current.CancellationToken</c> to satisfy xUnit1051. Cancellation
    /// behaviour is covered by driving <see cref="IParser{TInput,TOutput}.ParseAsync"/> directly.
    /// </remarks>
    internal static async Task<(List<ParsedRecord> Records, List<ParseError> Errors)> CollectAsync(
        this ITextParser parser,
        string input,
        IProgress<ParseProgress>? progress = null
    )
    {
        var records = new List<ParsedRecord>();
        var errors = new List<ParseError>();

        await foreach (var outcome in parser.ParseAsync(input, progress, TestContext.Current.CancellationToken))
        {
            if (outcome.IsSuccess)
            {
                records.Add(outcome.Value!);
            }
            else
            {
                errors.Add(outcome.Error);
            }
        }

        return (records, errors);
    }

    /// <summary>Reads a field by name, failing the test if it is absent.</summary>
    internal static string Field(this ParsedRecord record, string name) =>
        record[name] ?? throw new InvalidOperationException($"Field '{name}' is missing.");

    /// <summary>Builds a delimited document with a header plus <paramref name="rows"/> data rows.</summary>
    internal static string DelimitedDocument(int rows) =>
        string.Join('\n', Enumerable.Range(0, rows + 1).Select(i => i == 0 ? "id,name" : $"{i},row{i}"));
}