using TeamsISO.Engine.Domain;

namespace TeamsISO.Engine.Discovery;

/// <summary>
/// Parses NDI source strings emitted by Microsoft Teams.
///
/// Examples Teams emits:
///   "MACHINE (Teams - Display Name)"
///   "MACHINE (Teams)"                — auto-mixed active speaker
///   "MACHINE (Teams Audio)"          — audio-only mix
///   "MACHINE (Teams Screen Share)"   — screen share
/// </summary>
public static class NdiSourceParser
{
    public static NdiSource? Parse(string fullName)
    {
        if (string.IsNullOrWhiteSpace(fullName))
            return null;

        // Find the last '(' so machine names can themselves contain parens.
        var openParen = fullName.LastIndexOf('(');
        if (openParen <= 0 || !fullName.EndsWith(')'))
        {
            // Try outer parens for cases like "MACHINE (Teams - Smith, Bob (PM))"
            // by walking from the first '(' that opens a "Teams" inner.
            var firstParen = fullName.IndexOf(" (Teams", StringComparison.Ordinal);
            if (firstParen <= 0)
                return null;
            openParen = firstParen + 1;
            if (!fullName.EndsWith(')'))
                return null;
        }
        else
        {
            // Re-anchor to the first " (Teams" if present, so display names containing
            // their own parens (e.g. "Smith, Bob (PM)") don't get truncated.
            var firstParen = fullName.IndexOf(" (Teams", StringComparison.Ordinal);
            if (firstParen > 0)
                openParen = firstParen + 1;
        }

        var machine = fullName[..openParen].TrimEnd();
        if (machine.Length == 0)
            return null;

        var inner = fullName.Substring(openParen + 1, fullName.Length - openParen - 2).Trim();

        if (!inner.StartsWith("Teams", StringComparison.Ordinal))
            return null;

        if (inner == "Teams")
            return new NdiSource(fullName, machine, NdiSourceKind.ActiveSpeaker, DisplayName: null);
        if (inner == "Teams Audio")
            return new NdiSource(fullName, machine, NdiSourceKind.Audio, DisplayName: null);
        if (inner == "Teams Screen Share")
            return new NdiSource(fullName, machine, NdiSourceKind.ScreenShare, DisplayName: null);

        const string prefix = "Teams - ";
        if (inner.StartsWith(prefix, StringComparison.Ordinal))
        {
            var display = inner[prefix.Length..].Trim();
            if (display.Length == 0)
                return null;
            return new NdiSource(fullName, machine, NdiSourceKind.Participant, display);
        }

        return null;
    }
}