using System.Text;

namespace ExtractMethod.Tooling;

/// <summary>
/// Renders an <see cref="ExtractionReport"/> as the human-readable extract-
/// method suggestion report (parent spec): params (with ref), return
/// candidates, locals, extract-first candidates (deduped, with occurrence
/// counts and flags), the limitation notes, and the suggested signature line
/// LAST. Pure string shaping — no Roslyn — so tests can pin the exact output
/// the CLI prints.
/// </summary>
public static class ReportFormatter
{
    public static string Format(ExtractionReport report)
    {
        var sb = new StringBuilder();
        var selection = report.Selection;
        var suggestion = report.Suggestion;

        // Header (same wording the CLI printed since em 01).
        sb.AppendLine(
            $"{selection.Count} statement(s) selected, lines {selection.StartLine}..{selection.EndLine} " +
            $"in {selection.Method?.Identifier.ValueText}(): " +
            string.Join(", ", selection.Kinds));

        AppendBucket(sb, "params", suggestion.Params.Select(p =>
            $"{p.Name} ({p.Type}){(p.ByRef ? " [ref]" : " [in]")}"));
        AppendBucket(sb, "returns", suggestion.Returns.Select(r => $"{r.Name} ({r.Type})"));
        AppendBucket(sb, "locals", suggestion.Locals);

        if (report.ExtractFirst.Count == 0)
        {
            sb.AppendLine("extract-first: (none)");
        }
        else
        {
            sb.AppendLine("extract-first:");
            foreach (var entry in report.ExtractFirst)
            {
                // Flags accumulate; occurrence count is always shown because
                // "count occurrences" is the point of the dedupe.
                var flags = new List<string>();
                if (entry.IsInvocation)
                {
                    flags.Add("hoisting changes eval count");
                }

                if (entry.Optional)
                {
                    flags.Add($"optional: own-class {entry.OwnMemberKind}");
                }

                var flagText = flags.Count > 0 ? $" [{string.Join("; ", flags)}]" : string.Empty;
                sb.AppendLine($"  - {entry.Text} — {entry.SymbolDisplay} ×{entry.Occurrences}{flagText}");
            }
        }

        foreach (var note in report.Notes)
        {
            sb.AppendLine($"note: {note}");
        }

        var signature = report.Signature;
        var parameterList = string.Join(", ", signature.Params.Select(p => $"{(p.ByRef ? "ref " : "")}{p.Type} {p.Name}"));
        sb.AppendLine($"suggested signature: {signature.ReturnType} {signature.MethodName}({parameterList})");

        return sb.ToString();
    }

    private static void AppendBucket(StringBuilder sb, string name, IEnumerable<string> items)
    {
        var enumerated = items.ToList();
        sb.AppendLine(enumerated.Count == 0 ? $"{name}: (none)" : $"{name}: {enumerated[0]}");
        for (var i = 1; i < enumerated.Count; i++)
        {
            sb.AppendLine($"{name}: {enumerated[i]}");
        }
    }
}