using HanaToolbox.Services.Interfaces;

namespace HanaToolbox.Services;

/// <summary>
/// Locates hdbsql and hdbuserstore binaries using:
/// 1. Value from config (if set)
/// 2. `which` lookup on PATH
/// 3. /usr/sap/hdbclient/
/// 4. /usr/sap/&lt;SID&gt;/HDB&lt;instance&gt;/exe/
/// </summary>
public sealed class HdbClientLocator(IProcessRunner runner) : IHdbClientLocator
{
    public string LocateHdbsql(string? configuredPath, string sid, string instanceNumber) =>
        Locate("hdbsql", configuredPath, sid, instanceNumber);

    public string LocateHdbuserstore(string? configuredPath, string sid, string instanceNumber) =>
        Locate("hdbuserstore", configuredPath, sid, instanceNumber);

    private string Locate(string binary, string? configuredPath, string sid, string instanceNumber)
    {
        // 1. User-configured explicit path
        if (!string.IsNullOrWhiteSpace(configuredPath) && File.Exists(configuredPath))
            return configuredPath;

        // 2. which <binary>
        var whichResult = runner.RunAsync("/usr/bin/which", [binary]).GetAwaiter().GetResult();
        if (whichResult.Success && !string.IsNullOrWhiteSpace(whichResult.StdOut))
            return whichResult.StdOut.Split('\n')[0].Trim();

        // 3. /usr/sap/hdbclient/
        var path3 = $"/usr/sap/hdbclient/{binary}";
        if (File.Exists(path3)) return path3;

        // 4. /usr/sap/<SID>/HDB<instance>/exe/
        var path4 = $"/usr/sap/{sid.ToUpperInvariant()}/HDB{instanceNumber}/exe/{binary}";
        if (File.Exists(path4)) return path4;

        throw new FileNotFoundException(
            $"Could not locate '{binary}'. Set HdbsqlPath/HdbuserstorePath in hanatoolbox.json or ensure it is on PATH.");
    }
}